首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   118篇
  免费   7篇
  国内免费   16篇
测绘学   3篇
大气科学   6篇
地球物理   35篇
地质学   39篇
海洋学   32篇
天文学   13篇
综合类   3篇
自然地理   10篇
  2023年   1篇
  2021年   7篇
  2020年   1篇
  2019年   7篇
  2018年   1篇
  2017年   7篇
  2016年   5篇
  2015年   8篇
  2014年   5篇
  2013年   7篇
  2012年   4篇
  2011年   8篇
  2010年   9篇
  2009年   8篇
  2008年   8篇
  2007年   8篇
  2006年   5篇
  2005年   8篇
  2004年   5篇
  2003年   3篇
  2002年   5篇
  2001年   1篇
  1999年   1篇
  1997年   3篇
  1996年   1篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1992年   4篇
  1989年   1篇
  1982年   1篇
排序方式: 共有141条查询结果,搜索用时 671 毫秒
81.
We describe a compact, highly integrated instrument concept for the detection and identification of a wide range of molecules associated with extinct/extant life or potential life processes. The Specific Molecular Identification of Life Experiment (SMILE) will be sensitive to the presence of a range of target molecules using both electrical and optical transduction techniques, and incorporates molecular imprinted polymers in addition to traditional biological receptors such as antibodies. A number of versions of the concept are possible depending on available resources e.g. mass, volume, etc. The full concept utilises a novel imaging interferometer where a large number of molecular receptors are deposited on the measurement plane of an imaging interferometer and read out by an imaging detector, enabling multiple targets—biomarkers—within a sample to be measured simultaneously. The optics can also form the basis of an UV-NIR imaging Fourier spectrometer allowing basic mineralogy studies to be conducted using optical properties to assist in the determination of the geological context of the samples. By incorporating micro-fabricated transducer arrays, micro-fluidics and artificial molecular recognition systems, as well as recombinant antibody technology with appropriate integration methods, SMILE forms a compact and robust “Life Marker Chip” which has been proposed for future planetary missions including ESA's ExoMars mission, where the instrument offers the possibility of conducting a direct in situ search for signs of past or present biological activity on Mars. In addition to its role in planetary exploration, derivatives of SMILE have multiple terrestrial applications in fields such as forensic analysis and environmental monitoring.  相似文献   
82.
Knowledge of altitudinal covariation in interspecific competition and life history of birds inhabiting meadow-wastelands in the Tibetan plateau can contribute to our understanding for ecological adaptation of organisms to extreme environments and aid conservation for the unique ecosystem in the world. We reported reproductive ecology of two sympatric Montifringilla snowfinch species (Montifringilla taczanowskii and Montifringilla ruficollis) in a higher altitude wasteland, and compared the data with those of their lower altitude conspecifics. Both species nested in pika burrows and had similar breeding phenology. Nesting habitats of the two species tended to be separated in space as a result of asymmetrical competition, with large-sized M. taczanowskii occupying patches with better vegetation and small-sized M. ruficollis using poorly vegetated patches. In the less harsh lower altitude, however, their nest sites are randomly distributed. Relative to their lower altitude conspecifics, the higher altitude snowfinches had small body sizes but long wings, assuming an adaptation to increasing power demands for flying in thin air. There was a reduced fecundity with increasing altitudes, suggesting an adaptive response to the unpredictable conditions. We argue that the simplified bird community in stressful environments will be more vulnerable to perturbations. This highlights the importance to maintain ecological processes of the ecosystem.  相似文献   
83.
A comparative life cycle assessment (LCA) between three different cheese packages (P1: completely polypropylene (PP), P2: tin and polyethylene (PE), and P3: carton and PE) has been carried out for the production, distribution and waste disposal (100% landfill) phase. A package for 1 kg of cheese was selected as the functional unit. SimaPro7 software (PRèConsultants, The Netherlands) was used for the LCA study. The EcoIndicator 99 method was selected for comparison of the packages. The comparisons show that the total environmental performance of the cheese package types in order from worst to best is P2, P1, and P3. This conclusion was supported by a sensitivity analysis, which was conducted by using different impact assessment methods.  相似文献   
84.
The primary motivation for the vehicle replacement schemes that were implemented in many countries was to encourage the purchase of new cars. The basic assumption of these schemes was that these acquisitions would benefit both the economy and the environment as older and less fuel-efficient cars were scrapped and replaced with more fuel-efficient models. In this article, we present a new environmental impact assessment method for assessing the effectiveness of scrappage schemes for reducing CO2 emissions taking into account the rebound effect, driving behavior for older versus new cars and entire lifecycle emissions for during the manufacturing processes of new cars. The assessment of the Japanese scrappage scheme shows that CO2 emissions would only decrease if users of the scheme retained their new gasoline passenger vehicles for at least 4.7 years. When vehicle replacements were restricted to hybrid cars, the reduction in CO2 achieved by the scheme would be 6–8.5 times higher than the emissions resulting from a scheme involving standard, gasoline passenger vehicles. Cost–benefit analysis, based on the emission reduction potential, showed that the scheme was very costly. Sensitivity analysis showed that the Japanese government failed to determine the optimum, or target, car age for scrapping old cars in the scheme. Specifically, scrapping cars aged 13 years and over did not maximize the environmental benefits of the scheme. Consequently, modifying this policy to include a reduction in new car subsidies, focused funding for fuel-efficient cars, and modifying the target car age, would increase environmental benefits.  相似文献   
85.
Knowledge of the basic life history traits of an aquatic organism such as voltinism and growth patterns is a fundamental step in understanding its potential use as indicator taxon and how it adapts to its complex environment. The distribution and life cycle of the Maghrebian endemic Choroterpes atlas Soldán & Thomas, 1983 was studied over a two year period. Random forest classification indicated that the species occupied both permanent and intermittent streams with high water depth, large river bed width and strong water flow. Density-based clustering of body measurements allowed the identification of last-instar nymphs which exhibited a significant sexual dimorphism: F-0 females were significantly larger than corresponding males. In addition, size-frequency plots and generalized additive models indicated that C. atlas exhibited a multivoltine annual cycle with three overlapping generations. Nymphal growth of the first generation happened in winter and spring with emergence occurring in June/July. The second generation grew from June/July to September whereas the third generation was completed from August/September to November. GAMs also indicated that body size varied significantly between years. The large regional distribution, habitat requirement, and phenology of C. atlas may ideally complement the potential use of Ecdyonurus rothschildi as a useful environmental indicator for North African streams and rivers.  相似文献   
86.
Assessing the environmental impact due to consumption of goods and services is a pivotal step towards achieving the sustainable development goal related to responsible production and consumption (i.e. SDG 12). Household appliances plays a crucial role and should be assessed in a systemic manner, namely considering all life cycle stages, technological efficiency, and affluence aspects. The present study assess the impact of such household appliances used in Europe, and tests scenarios of potential impact reduction at various scales. Life cycle assessment is applied to 14 different household appliances (ranging from dishwashers to television devices) selected to build a set of representative products, based on their economic value and diffusion in households in Europe. Related impacts are calculated with the Environmental Footprint method for calculating a Consumer Footprint “appliances” for the baseline year 2010. A number of scenarios encompassing eco-solutions on a technical level, changes in consumption pattern, behavioral changes, as well as the combination of all these aspects are run to estimate the Consumer Footprint related to household appliances for the year 2030, compared against this baseline scenario. The baseline Consumer Footprint is confirming the importance of the use phase in leading the impacts in almost all impact categories. Testing different scenarios concludes that there is a reduction of the impact for most of the categories (with up to 67% for the ozone depletion potential, and still around 35% for the global warming potential), while two of the here examined impact categories (i.e. land-use and mineral resource depletion) show an overall potential that is even negative – i.e. the results of all scenarios are higher than the ones of the 2010 baseline scenario. The increase in purchase and use of such appliances may offset energy efficiency benefits in some of the examined categories. Hence, the assessment of sustainability of appliances consumption should always include several scales, from the efficiency of the products (micro scale), to the improvement of the energy mix (meso scale), up to accounting for socio-economic drivers and patterns of consumption affecting the overall appliances stock (macro scale).  相似文献   
87.
The paradigm of an ancient warm, wet, and dynamically active Mars, which transitioned into a cold, dry, and internally dead planet, has persisted up until recently despite published Viking-based geologic maps that indicate geologic and hydrologic activity extending into the Late Amazonian epoch. This paradigm is shifting to a water-enriched planet, which may still exhibit internal activity, based on a collection of geologic, hydrologic, topographic, chemical, and elemental evidences obtained by the Viking, Mars Global Surveyor (MGS), Mars Odyssey (MO), Mars Exploration Rovers (MER), and Mars Express (MEx) missions. The evidence includes: (1) stratigraphically young rock materials such as pristine lava flows with few, if any, superposed impact craters; (2) tectonic features that cut stratigraphically young materials; (3) features with possible aqueous origin such as structurally controlled channels that dissect stratigraphically young materials and anastomosing-patterned slope streaks on hillslopes; (4) spatially varying elemental abundances for such elements as hydrogen (H) and chlorine (Cl) recorded in rock materials up to 0.33 m depth; and (5) regions of elevated atmospheric methane. This evidence is pronounced in parts of Tharsis, Elysium, and the region that straddles the two volcanic provinces, collectively referred to here as the Tharsis/Elysium corridor. Based in part on field investigations of Solfatara Crater, Italy, recommended as a suitable terrestrial analog, the Tharsis/Elysium corridor should be considered a prime target for Mars Reconnaissance Orbiter (MRO) investigations and future science-driven exploration to investigate whether Mars is internally and hydrologically active at the present time, and whether the persistence of this activity has resulted in biologic activity.  相似文献   
88.
Assessing the environmental impact due to consumption of goods and services is a pivotal step towards achieving the sustainable development goal related to responsible production and consumption (i.e. SDG 12). Household appliances plays a crucial role and should be assessed in a systemic manner, namely considering all life cycle stages, technological efficiency, and affluence aspects. The present study assess the impact of such household appliances used in Europe, and tests scenarios of potential impact reduction at various scales. Life cycle assessment is applied to 14 different household appliances (ranging from dishwashers to television devices) selected to build a set of representative products, based on their economic value and diffusion in households in Europe. Related impacts are calculated with the Environmental Footprint method for calculating a Consumer Footprint “appliances” for the baseline year 2010. A number of scenarios encompassing eco-solutions on a technical level, changes in consumption pattern, behavioral changes, as well as the combination of all these aspects are run to estimate the Consumer Footprint related to household appliances for the year 2030, compared against this baseline scenario. The baseline Consumer Footprint is confirming the importance of the use phase in leading the impacts in almost all impact categories. Testing different scenarios concludes that there is a reduction of the impact for most of the categories (with up to 67% for the ozone depletion potential, and still around 35% for the global warming potential), while two of the here examined impact categories (i.e. land-use and mineral resource depletion) show an overall potential that is even negative – i.e. the results of all scenarios are higher than the ones of the 2010 baseline scenario. The increase in purchase and use of such appliances may offset energy efficiency benefits in some of the examined categories. Hence, the assessment of sustainability of appliances consumption should always include several scales, from the efficiency of the products (micro scale), to the improvement of the energy mix (meso scale), up to accounting for socio-economic drivers and patterns of consumption affecting the overall appliances stock (macro scale).  相似文献   
89.
落实科学发展观,推行全寿命周期管理建设电网,对推动标准化建设理念和方法的创新,完善标准化建设内涵,提高标准化建设水平有着重要作用。作为负责把关、协调、服务工作的项目设总,结合工程的实际情况,以全寿命周期的观点做好设计方案的技术比选工作,对建设统一坚强智能电网具有实质性的意义。  相似文献   
90.
Assessing the environmental impact due to consumption of goods and services is a pivotal step towards achieving the sustainable development goal related to responsible production and consumption (i.e. SDG 12). Household appliances plays a crucial role and should be assessed in a systemic manner, namely considering all life cycle stages, technological efficiency, and affluence aspects. The present study assess the impact of such household appliances used in Europe, and tests scenarios of potential impact reduction at various scales. Life cycle assessment is applied to 14 different household appliances (ranging from dishwashers to television devices) selected to build a set of representative products, based on their economic value and diffusion in households in Europe. Related impacts are calculated with the Environmental Footprint method for calculating a Consumer Footprint “appliances” for the baseline year 2010. A number of scenarios encompassing eco-solutions on a technical level, changes in consumption pattern, behavioral changes, as well as the combination of all these aspects are run to estimate the Consumer Footprint related to household appliances for the year 2030, compared against this baseline scenario. The baseline Consumer Footprint is confirming the importance of the use phase in leading the impacts in almost all impact categories. Testing different scenarios concludes that there is a reduction of the impact for most of the categories (with up to 67% for the ozone depletion potential, and still around 35% for the global warming potential), while two of the here examined impact categories (i.e. land-use and mineral resource depletion) show an overall potential that is even negative – i.e. the results of all scenarios are higher than the ones of the 2010 baseline scenario. The increase in purchase and use of such appliances may offset energy efficiency benefits in some of the examined categories. Hence, the assessment of sustainability of appliances consumption should always include several scales, from the efficiency of the products (micro scale), to the improvement of the energy mix (meso scale), up to accounting for socio-economic drivers and patterns of consumption affecting the overall appliances stock (macro scale).  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号