全文获取类型
收费全文 | 23849篇 |
免费 | 220篇 |
国内免费 | 151篇 |
专业分类
测绘学 | 391篇 |
大气科学 | 1242篇 |
地球物理 | 4531篇 |
地质学 | 9563篇 |
海洋学 | 2259篇 |
天文学 | 5325篇 |
综合类 | 48篇 |
自然地理 | 861篇 |
出版年
2022年 | 296篇 |
2021年 | 467篇 |
2020年 | 427篇 |
2019年 | 485篇 |
2018年 | 1016篇 |
2017年 | 947篇 |
2016年 | 940篇 |
2015年 | 406篇 |
2014年 | 825篇 |
2013年 | 1362篇 |
2012年 | 936篇 |
2011年 | 1138篇 |
2010年 | 1090篇 |
2009年 | 1248篇 |
2008年 | 1069篇 |
2007年 | 1236篇 |
2006年 | 1081篇 |
2005年 | 589篇 |
2004年 | 551篇 |
2003年 | 554篇 |
2002年 | 574篇 |
2001年 | 516篇 |
2000年 | 419篇 |
1999年 | 344篇 |
1998年 | 324篇 |
1997年 | 332篇 |
1996年 | 259篇 |
1995年 | 267篇 |
1994年 | 243篇 |
1993年 | 187篇 |
1992年 | 214篇 |
1991年 | 184篇 |
1990年 | 200篇 |
1989年 | 190篇 |
1988年 | 159篇 |
1987年 | 184篇 |
1986年 | 175篇 |
1985年 | 212篇 |
1984年 | 202篇 |
1983年 | 200篇 |
1982年 | 195篇 |
1981年 | 175篇 |
1980年 | 162篇 |
1979年 | 183篇 |
1978年 | 161篇 |
1977年 | 142篇 |
1976年 | 135篇 |
1975年 | 138篇 |
1974年 | 126篇 |
1973年 | 168篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
The spatial positions of unidentified gamma-ray sources ( E>100 MeV) were analyzed. This analysis shows that gamma-ray sources with fluxes >5×10?7 cm?2 s?1 correlate with Wolf-Rayet stars, while gamma-ray sources with fluxes <5×10?7 cm?2 s?1 may be associated with flaring stars. 相似文献
82.
O.?V.?YushkovaEmail author A.?L.?Gavrik V.?N.?Marchuk V.?V.?Yushkov V.?M.?Smirnov M.?A.?Laptev B.?V.?Chernyshev I.?N.?Dutyshev V.?P.?Lebedev A.?V.?Medvedev A.?A.?Petrukovich 《Solar System Research》2018,52(4):287-300
An overview of radiophysical investigations of the lunar soil and plasma shell by active radar detection with the use of spacecraft is presented. The possibility is analyzed of conducting bistatic measurements using the Irkutsk Incoherent Scattering Radar and the onboard radar system RLK-L which is being developed for the orbital station of the Luna-Resurs mission. 相似文献
83.
84.
85.
Low phase angle effects in photometry of trans-neptunian objects: 20000 Varuna and 19308 (1996 TO66)
We present the results of photometric observations of trans-neptunian object 20000 Varuna, which were obtained during 7 nights in November 2004-February 2005. The analysis of new and available photometric observations of Varuna reveals a pronounced opposition surge at phase angles less than 0.1 deg with amplitude of 0.2 mag relatively to the extrapolation of the linear part of magnitude-phase dependence to zero phase angle. The opposition surge of Varuna is markedly different from that of dark asteroids while quite typical for moderate albedo Solar System bodies. We find an indication of variations of the scattering properties over Varuna's surface that could result in an increase of the lightcurve amplitude toward zero phase angle. It is shown that a similar phase effect can be responsible for lightcurve changes found for TNO 19308 (1996 TO66) in 1997-1999. 相似文献
86.
E.?S.?KazakEmail author E.?G.?Kalitina N.?A.?Kharitonova G.?A.?Chelnokov E.?V.?Elovskii I.?V.?Bragin 《Moscow University Geology Bulletin》2018,73(3):287-294
This paper reports the results of the experimental determination of the coefficient of sorption of rare-earth elements and yttrium (REY) under conditions of acidic pH using several strains of heterotrophic bacteria (Microbacterium sp., Curtobacterium sp., Bacillus subtilis, Pseudomonas putida, and Bacillus pumilis) that are widespread in natural and technogenic waters of the Far East (Russia). Insignificant fractionation between heavy and light rare-earth elements, negative cerium and dysprosium anomalies, and a positive europium anomaly were revealed. The selectivity of REY biosorption by gram-positive and gram-negative bacteria, as well as inertia of the biosorption process under more acidic conditions of the medium, were shown. 相似文献
87.
Study of the material composition of Fe-Mn crusts from submarine rises in the central part of the Sea of Japan, with modern
precision methods applied, has yielded a high (up to 854 g/t) concentration of gallium contained in sorbed form. The new data
obtained have allowed a new genetic type of gallium deposits—hydrothermal-sedimentary—to be distinguished. 相似文献
88.
The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied. 相似文献
89.
Geospatial data and tools are key in locating lost or missing persons in as short a time as possible. In this study, we used a geographic information system (GIS) to analyze four years of search and rescue (SAR) mission data from Colorado to determine the appropriate use of GIS for volunteer-based SAR organizations with limited resources and GIS expertise. GIS can provide more sophisticated analyses of geospatial data than simple mapping technologies, but our findings indicated that complex spatial analysis might not be required on all missions, because the majority of missions were completed within six to ten hours. Instead, new technologies such as tablets with mapping software and online GIS systems that provide quick and easy access to up-to-date geospatial data such as imagery offer capabilities that could improve mission planning. Here we provide a framework in which SAR missions can apply geospatial technologies to aid with missions, identify critical “hotspots,” and enhance postanalysis and training. The work here is highly applicable for nonprofit SAR groups when deciding on what GIS technologies to consider for their areas. 相似文献
90.
Mohammad M. M. Alsahli Ahmed M. AlHasem 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2016,116(1):56-70
Assessing coastal vulnerability to sea level rise (SLR) at local and regional scales is a fundamental step for designing successful long-term coastal management plans. This study was thus designed to assess Kuwait coastal vulnerability to SLR at four scenarios (.5, 1, 1.5 and 2 m). Potential inundated areas and the number of people at risk were estimated based on these SLR scenarios. A coastal vulnerability index (CVI) map of Kuwait was then computed based on the lowest scenario using eight parameters: elevation, coastal slope, geomorphology, distance to 20-m isobath, population, land use, cultural heritage and transportation. The geographic distribution of inundated areas at an SLR of .5 m revealed that the northern islands of Kuwait and coastal areas along Kuwait Bay would be highly impacted, whereas the coastal area near Shuaibah Port was the most influenced among the southern coasts. Most of the coastal area exhibited a moderate vulnerability to SLR, especially the northern islands. This study presented an initial vulnerability assessment for Kuwait coasts to SLR, which can be extended with more variables. The integrated remote sensing and geographic information system methodology demonstrated in this study can be applied in similar studies elsewhere. 相似文献