全文获取类型
收费全文 | 484篇 |
免费 | 20篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 50篇 |
地球物理 | 124篇 |
地质学 | 174篇 |
海洋学 | 49篇 |
天文学 | 73篇 |
综合类 | 3篇 |
自然地理 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 10篇 |
2020年 | 17篇 |
2019年 | 6篇 |
2018年 | 18篇 |
2017年 | 22篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 22篇 |
2013年 | 28篇 |
2012年 | 22篇 |
2011年 | 35篇 |
2010年 | 37篇 |
2009年 | 30篇 |
2008年 | 37篇 |
2007年 | 21篇 |
2006年 | 16篇 |
2005年 | 18篇 |
2004年 | 25篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有508条查询结果,搜索用时 31 毫秒
91.
92.
Ugolini A Ungherese G Somigli S Galanti G Baroni D Borghini F Cipriani N Nebbiai M Passaponti M Focardi S 《Marine environmental research》2008,65(4):349-357
The present paper assesses the use of the supralittoral amphipod Talitrus saltator as a bioindicator of the effects of human trampling on the supralittoral sandy band. Samplings in delimited areas were carried out at sites subjected to different human impact. The results showed a strong negative correlation between the number of swimmers and the sandhopper population density, while there was no clear relationship between sandhopper abundance and the other factors considered: granulometry, compactness and organic carbon content of the sand, and trace metal contents in the sand and sandhoppers. A field test of trampling conducted in a confined space showed its direct negative effect on sandhopper survival. However, trace metal analysis confirmed the ability of T. saltator to bioaccumulate some elements (Hg, Zn, Cu, Cd). Our study demonstrates that T. saltator is a good bioindicator of human impact in the supralittoral zone of sandy shores. 相似文献
93.
Marsili L Casini S Bucalossi D Porcelloni S Maltese S Fossi MC 《Marine environmental research》2008,66(1):151-153
The aim of the present study was to propose the immunofluorescence technique in cultured fibroblasts from Mediterranean cetaceans as a new "in vitro" tool to explore the susceptibility of these marine mammals to different xenobiotic compounds. The cell lines were cultured from integument biopsies of free-ranging and stranded cetaceans (dead within 12h). Using the indirect immunofluorescence assay, we detected endogenous proteins induced by different contaminants. Here we present the method used for qualitative and quantitative evaluation of cytochromes P450 (CYP1A1 and CYP2B) induced by some POPs (DDTs and PCBs) and emerging contaminants (PBDEs) in fibroblast cell cultures of striped dolphin (Stenella coeruleoalba) and bottlenose dolphin (Tursiops truncatus). Immunofluorescence was quantified with a specially designed Olympus macro, DetectIntZ. A major result was the possibility of using this "in vitro" assay to quantify induction of endogenous proteins. 相似文献
94.
We summarize currently available evidence for ionization stratification in the winds of [WR] stars and point out that ionization stratification may be important to explain with radiation-driven wind theory the winds of [WR] stars, while also providing an empirical tool to investigate [WR] wind structures. 相似文献
95.
96.
Francesco Di Benedetto Ilaria Bencistà Francesco D’Acapito Silvia Frizzera Andrea Caneschi Massimo Innocenti Alessandro Lavacchi Giordano Montegrossi Werner Oberhauser Maurizio Romanelli Herbert Dittrich Luca A. Pardi Gerold Tippelt Georg Amthauer 《Physics and Chemistry of Minerals》2016,43(8):535-544
The successful synthesis of nanoparticles of Fe-bearing kuramite, (Cu,Fe)3SnS4, is reported in this study. Nanocrystalline powders were obtained through a mild, environmentally friendly and scalable solvothermal approach, in a single run. The sample was the object of a multidisciplinary investigation, including X-ray diffraction and absorption, scanning electron microscopy and microanalysis, electron paramagnetic resonance, diffuse reflectance and Mössbauer spectroscopy as well as SQUID magnetometry. The nanoparticles consist of pure Fe-bearing kuramite, exhibiting tetragonal structure. The valence state of the metal cations was assessed to be Cu+, Sn4+ and Fe3+. The material presents a band gap value of 1.6 eV, which is fully compatible with solar cell applications. The uptake of Fe by nanokuramite opens a compositional field where the physical properties can be tuned. We thus foster the application of Fe-bearing nanokuramite for photovoltaics and energy storage purposes. 相似文献
97.
98.
José?D.?CarriquiryEmail author Pablo?Jorgensen Julio?A.?Villaescusa Silvia?E.?Ibarra-Obando 《Estuaries and Coasts》2016,39(2):451-461
Nutrient sources of San Quintin Bay, a coastal lagoon affected by coastal upwelling off Baja California (Mexico), were traced using generalized additive (mixed) models (GAMM) to the stable nitrogen isotopic composition, C:N and N content of two co-occurring macrophytes (the macroalgae Ulva spp. and the seagrass Zostera marina). The geochemical tracers followed a spatial trend that partly responded to the long-term nutrient gradient from the ocean towards the interior of the bay. N content in Z. marina and Ulva spp. decreased linearly (while C:N increased) towards the middle section of the bay to concentration levels that indicate potential N limitation for growth. Concurrently midway into the bay (6–9 km), the δ15N of both macrophytes showed a gradual enrichment in 15N reflecting progressive denitrification. The spatial pattern of δ15N and the decrease in C:N of the macrophytes towards the innermost section of the bay indicated an additional nonoceanic source of dissolved nitrogen in this zone. The similarity of the δ15N pattern of Z. marina and Ulva spp. implies that their δ15N composition is mainly controlled by the availability of N, in spite of the physiological differences between taxa. A better fit of GAMM to N content and C:N was obtained for Z. marina than for Ulva spp. indicating that the former delineate more steadily and smoothly the influence of upwelling along the spatial gradient. Nonetheless, Ulva spp. may be analyzed in combination with Z. marina to characterize the environmental conditions at the time of sampling. 相似文献
99.
The effectiveness of high-resolution LiDAR data combined with PSInSAR data in landslide study 总被引:1,自引:0,他引:1
Andrea Ciampalini Federico Raspini William Frodella Federica Bardi Silvia Bianchini Sandro Moretti 《Landslides》2016,13(2):399-410
The spatial resolution of digital elevation models (DEMs) is an important factor for reliable landslide studies. Multi-interferometric techniques such as persistent scatterer interferometric synthetic aperture radar (PSInSAR) are used to evaluate the landslide state of activity and its ground deformation velocity, which is commonly measured along the satellite line of sight (LOS). In order to compare velocities measured by different satellites in different periods, their values can be projected along the steepest slope direction, which is the most probable direction of real movement. In order to achieve this result, DEM-derived products are needed. In this paper, the effectiveness of different DEM resolutions was evaluated in order to project ground deformation velocities measured by means of PSInSAR technique in two different case studies in the Messina Province (Sicily, southern Italy): San Fratello and Giampilieri. Three DEMs were used: (i) a 20-m resolution DEM of the Italian Military Geographic Institute (IGM), (ii) a 2-m resolution DEM derived from airborne laser scanning (ALS) light detection and ranging (LiDAR) data for the San Fratello 2010 landslide, and (iii) a 1-m resolution DEM derived from ALS LiDAR data for the area of Giampilieri. The evaluation of the applied method effectiveness was performed by comparing the DEMs elevation with those of each single permanent scatterer (PS) and projecting the measured velocities along the steepest slope direction. Results highlight that the higher DEM resolution is more suitable for this type of analysis; in particular, the PS located nearby the watershed divides is affected by geometrical problems when their velocities are projected along the steepest slope. 相似文献
100.
Daniel Karthe Ole Behrmann Verena Blättel Dennis Elsässer Christian Heese Matthias Hügle Frank Hufert Andreas Kunze Reinhard Niessner Johannes Ho Buren Scharaw Matthias Spoo Andreas Tiehm Gerald Urban Silvia Vosseler Thomas Westerhoff Gregory Dame Michael Seidel 《Environmental Earth Sciences》2016,75(23):1481
The state-of-the-art monitoring of drinking water hygiene is based on the cultivation and enumeration of indicator bacteria. Despite its proven reliability, this approach has the disadvantages of being (a) relatively slow and (b) limited to a small number of indicator bacteria. Ideally, alternative methods would be less time-consuming while providing information about a larger set of hygienically relevant microorganisms including viruses. In this paper, we present insights into the design of a modular concentration and detection system for bacteria, bacteriophages and viruses. Following further validation, this or similar techniques have the potential to extend and speed up the monitoring of raw and drinking water hygiene in the future. The system consists of different modules for the concentration of microorganisms, an amplification and detection unit that includes a module for the differentiation between live and dead microorganisms, and an automated system for decision support and self-diagnosis. The ongoing testing under controlled laboratory conditions and real-life conditions in the water supply industry yields further system improvements. Moreover, the increased sensitivity and broader range of microbiological parameters emphasize the need for a reconsideration of the currently used criteria for the assessment of (drinking) water hygiene. 相似文献