全文获取类型
收费全文 | 3054篇 |
免费 | 529篇 |
国内免费 | 785篇 |
专业分类
测绘学 | 106篇 |
大气科学 | 294篇 |
地球物理 | 762篇 |
地质学 | 1814篇 |
海洋学 | 660篇 |
天文学 | 16篇 |
综合类 | 162篇 |
自然地理 | 554篇 |
出版年
2024年 | 9篇 |
2023年 | 40篇 |
2022年 | 99篇 |
2021年 | 102篇 |
2020年 | 147篇 |
2019年 | 129篇 |
2018年 | 140篇 |
2017年 | 168篇 |
2016年 | 143篇 |
2015年 | 177篇 |
2014年 | 200篇 |
2013年 | 215篇 |
2012年 | 159篇 |
2011年 | 216篇 |
2010年 | 187篇 |
2009年 | 244篇 |
2008年 | 215篇 |
2007年 | 189篇 |
2006年 | 250篇 |
2005年 | 190篇 |
2004年 | 178篇 |
2003年 | 137篇 |
2002年 | 120篇 |
2001年 | 104篇 |
2000年 | 103篇 |
1999年 | 92篇 |
1998年 | 76篇 |
1997年 | 65篇 |
1996年 | 54篇 |
1995年 | 30篇 |
1994年 | 33篇 |
1993年 | 41篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 26篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有4368条查询结果,搜索用时 468 毫秒
991.
LI Yaohu WANG Yang SHI Yu YANG Leilei CUI Qiliang BI Caiqin XU Yinbo WANG Qianyou SHAN Yansheng LIU Weibin MIAO Miao WANG Ting 《《地质学报》英文版》2023,97(3):873-888
Because it is necessary to focus on differences in regional oil reservoirs and determine the priority of the CCUSEOR(Carbon capture, utilization, and storage-enhanced oil recovery) deployment under China’s net-zero CO2 emission target, systematic and regional evaluations of CO2 sequestration capacity in major oil basins are needed considering the geofluid properties―carbon sequestration capacity in place(CSCIP)―where the ’in place’ indicates actual geological formation cond... 相似文献
992.
Climate change affects biophysical processes related to the transmission of many infectious diseases, with potentially adverse consequences for the health of communities. While our knowledge of biophysical associations between meteorological factors and disease is steadily improving, our understanding of the social processes that shape adaptation to environmental perturbations lags behind. Using computational modeling methods, we explore the ways in which social cohesion can affect adaptation of disease prevention strategies when communities are exposed to different environmental scenarios that influence transmission pathways for diseases such as diarrhea. We developed an agent-based model in which household agents can choose between two behavioral strategies that offer different levels of protection against environmentally mediated disease transmission. One behavioral strategy is initially set as more protective, leading households to adopt it widely, but its efficacy is sensitive to variable weather conditions and stressors such as floods or droughts that modify the disease transmission system. The efficacy of the second strategy is initially moderate relative to the first and is insensitive to environmental changes. We examined how social cohesion (defined as average number of household social network connections) influences health outcomes when households attempt to identify an optimal strategy by copying the behaviors of socially connected neighbors who seem to have adapted successfully in the past. Our simulation experiments suggest that high-cohesion communities are able to rapidly disseminate the initially optimal behavioral strategy compared to low-cohesion communities. This rapid and pervasive change, however, decreases behavioral diversity; i.e., once a high cohesion community settles on a strategy, most or all households adopt that behavior. Following environmental changes that reduce the efficacy of the initially optimal strategy, rendering it suboptimal relative to the alternative strategy, high-cohesion communities can fail to adapt. As a result, despite faring better early in the course of computational experiments, high-cohesion communities may ultimately experience worse outcomes. In the face of uncertainty in predicting future environmental stressors due to climate change, strategies to improve effective adaptation to optimal disease prevention strategies should balance between intervention efforts that promote protective behaviors based on current scientific understanding and the need to guard against the crystallization of inflexible norms. Developing generalizable models allows us to integrate a wide range of theories and multiple datasets pertaining to the relationship between social mechanisms and adaptation, which can provide further understanding of future climate change impacts. Models such as the one we present can generate hypotheses about the mechanisms that underlie the dynamics of adaptation events and suggest specific points of measurement to assess the impact of these mechanisms. They can be incorporated as modules within predictive simulations for specific socio-ecological contexts. 相似文献
993.
Urban water supply security is commonly measured in terms of per capita water availability at the city level. However, the actual services that citizens receive are influenced by several components, including (1) a city's access to water, (2) infrastructure for its treatment, storage and distribution, (3) financial capital for building and maintaining infrastructure, and (4) management efficacy for regulating and operating the water system. These four types of "capital" are required for the provision of public water supply services. A fifth capital “community adaptation” is needed when public services are insufficient. Here, we develop and test an integrated framework for the quantification of urban water supply security based on these five capitals. “Security” involves three dimensions: 1) the level of system function (i.e., supply services); 2) risks to these services; and 3) robustness of system functioning. We apply this Capital Portfolio Approach (CPA) to seven urban case studies selected from a wide range of hydro-climatic and socio-economic regions on four continents. Detailed data on urban water infrastructure and services were collected in two cities, and key stakeholder interviews and household surveys were conducted in one city. Additional cities were assessed based on publicly available utility and globally available datasets. We find that in cities with high levels of public services, adaptive capacity remains inactive, while cities with high levels of water insecurity rely on community adaptation for self-provision of services. Inequality in the capacity to adapt leads to variable levels of urban water security and the vulnerability of the urban poor. Results demonstrate the applicability of the presented framework for the assessment of individual urban water systems, as well as for cross-city comparison of any type of cities. We discuss implications for policy and decision-making. 相似文献
994.
水足迹与主成分分析法耦合的新疆水资源承载能力评价 总被引:2,自引:0,他引:2
通过耦合水足迹理论与主成分分析方法,构建基于水足迹的新疆地区水资源承载力评价指标体系,分析研究区2010~2015年间水资源承载能力变化情况。结果表明:2010~2015年间新疆地区的水资源承载力呈先增大后减小的现象,2014年水资源承载力最差,供水压力最大。其中,研究区的承载力主要受水资源和社会因素以及进出口贸易中虚拟水的影响,贡献度分别为56.791%、22.724%。另外,外部水足迹约占水足迹总量的10%,表明研究区出口产品中的水约占总水资源量的10%。 相似文献
995.
自升式钻井平台在东海的作业量随着西湖地区勘探开发的不断发展而在增加。因受台风影响及在同一地点多次作业的原因,自升式钻井平台不可避免地会在上一次作业位置附近重复作业,引起桩靴滑移现象,可能造成就位后悬臂梁覆盖能力下降,无法满足钻井作业需求,甚至影响平台结构安全,造成工程事故,大大增加了作业风险。本文以H9自升式钻井平台桩靴为例,分析了桩靴部分重合工况下的受力特点,研究了海底土体破坏形式,提出了不同类型土质条件下的桩靴水平力计算模型,并利用滑移线有限差分法近似计算桩靴极限载荷。对H9平台在现场重复就位时采取的措施进行了分析,并根据海上作业要求提出了一系列安全控制措施,为安全高效地实现平台重复就位提供了参考。 相似文献
996.
Shale adsorption and breakthrough pressure are important indicators of shale gas development and key factors in evaluating the reservoir capacities of shales. In this study, geochemical tests, pore-structure tests, methane adsorption tests, and breakthrough-pressure tests were conducted on shales from the Carboniferous Hurleg Formation in eastern Qaidam Basin. The effects of the shale compositions and pore structures on the adsorption and breakthrough pressures were studied, and the reservoir capacities of the shales were evaluated by analyzing the shale adsorptions and sealing effects. The results indicate that the organic carbon content was only one of factors in affecting the adsorption capacity of the shale samples while the effect of the clay minerals was limited. Based on the positive correlation between the adsorption capacity and specific surface area of the shale, the specific surface area of the micropores can be used as an indicator to determine the adsorption capacity of shale. The micro-fracturing of brittle minerals, such as quartz, create a primary path for shale gas breakthrough, whereas the expansion of clay minerals with water greatly increases the breakthrough pressure in the shale samples. Methane adsorption tests showed that maximum methane adsorption for shale samples Z045 and S039 WAS 0.107 and 0.09655 mmol/g, respectively. The breakthrough pressure was 39.36 MPa for sample S039, maintained for 13 days throughout the experiment; however, no breakthrough was observed in sample Z045 when subjected to an injected pressure of 40 MPa for 26 days. This indicates that sample Z045, corresponding to a depth of 846.24 m, exhibited higher adsorption capacity and a better reservoir-sealing effect than sample S039 (498.4 m depth). This study provides useful information for future studies of Qaidam Basin shale gas exploration and development and for evaluation of shale quality. 相似文献
997.
基于能值的山东省海洋生态足迹研究 总被引:1,自引:0,他引:1
能值-生态足迹模型是基于能值理论基础,结合生态足迹模型,运用区域能值密度将各项消费项目转换为可以直接相加的生物生产性面积,并以此来反映区域发展对区域环境资源的利用程度,衡量和评价区域海洋经济的可持续发展状况。将能值-生态足迹模型应用到区域海洋生态系统中,对海洋能值-生态足迹概念进行了界定,构建了海洋能值-生态足迹模型,并以山东省海洋生态系统为例进行了实证研究。结果表明,2010年山东省海洋生态系统总能值-生态足迹为1.74×106hm2,海洋生态系统总能值-生态承载力为1.60×107hm2,处于生态盈余状态,反映出山东海洋经济具有较强的可持续性。 相似文献
998.
0引言陈学溶老前辈的大名,我最早是在《朱文荣先生九秩嵩庆纪念文集》(1992年出版,发起者戚启勋教授)中看到的,他为这本纪念文集写了回忆文章《敬贺我国高空测候开拓者朱师九秩大庆》。戚启勋教授和陈学溶前辈是中央研究院气象研究所第三届气象练习班同学,朱文荣老前辈是他们当年的老师。没想到两岸气象双向交流后,我有幸在南京、北 相似文献
999.
对短螺栓型膨胀式自应力灌浆卡箍的滑动承载力进行了试验研究,首先从自应力产生机理介绍了短螺栓型灌浆卡箍结构,分析了这种结构的特点和优越性,然后在不同膨胀剂掺量和长细比下进行了这种卡箍试件的滑动承载力测试。试验结果表明:滑动承载力随着膨胀剂掺量的增加线性增加;在长细比为1.02~1.67的范围内,滑动应力差异不大,但当长细比增加到3.33时,滑动应力明显降低;而且短螺栓型膨胀式自应力灌浆卡箍比近似结构尺寸的传统长螺栓型卡箍能提供更大的滑动应力。试验结果为短螺栓型膨胀式灌浆卡箍的工程应用提供了一定的设计依据。 相似文献
1000.
基于城市综合承载力的概念,从水土资源、生态环境、社会经济、基础设施与公共服务等4个方面选择23个指标构建城市综合承载力评价指标体系。并尝试运用因子分析模型对湖南"3+5"城市群城市综合承载力区域差异进行客观评价。结果表明:影响和制约湖南"3+5"城市群城市综合承载力的核心因子为水土资源与公共服务、社会消费、污染治理及人口密度;湖南"3+5"城市群城市综合承载力区域差异明显,可分为3个等级。针对上述分析结果,提出提高湖南"3+5"城市群城市综合承载力的政策建议。 相似文献