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   38817篇
  免费   790篇
  国内免费   245篇
测绘学   780篇
大气科学   2620篇
地球物理   7613篇
地质学   14100篇
海洋学   3602篇
天文学   8637篇
综合类   87篇
自然地理   2413篇
  2022年   259篇
  2021年   454篇
  2020年   511篇
  2019年   589篇
  2018年   1038篇
  2017年   1034篇
  2016年   1109篇
  2015年   605篇
  2014年   1064篇
  2013年   1910篇
  2012年   1225篇
  2011年   1651篇
  2010年   1467篇
  2009年   1831篇
  2008年   1659篇
  2007年   1720篇
  2006年   1575篇
  2005年   1082篇
  2004年   1094篇
  2003年   1125篇
  2002年   1002篇
  2001年   869篇
  2000年   753篇
  1999年   681篇
  1998年   676篇
  1997年   690篇
  1996年   545篇
  1995年   560篇
  1994年   497篇
  1993年   446篇
  1992年   401篇
  1991年   427篇
  1990年   434篇
  1989年   384篇
  1988年   362篇
  1987年   394篇
  1986年   407篇
  1985年   504篇
  1984年   538篇
  1983年   537篇
  1982年   491篇
  1981年   450篇
  1980年   431篇
  1979年   403篇
  1978年   373篇
  1977年   378篇
  1976年   337篇
  1975年   350篇
  1974年   337篇
  1973年   369篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Urvachev  E. M.  Blinnikov  S. I.  Nomoto  K. 《Astronomy Letters》2021,47(11):738-745
Astronomy Letters - To explain the presence of early X-ray emission from the object AT2018cow, we have studied a scenario with the presence of dense ejecta in the system in the equatorial plane....  相似文献   
2.
Solar System Research - Ionizing radiation is one of the main factors that destroy biomolecules in extraterrestrial conditions. The effects of radiation depend on the conditions of the exposure...  相似文献   
3.
Izmailov  I. S.  Shakht  N. A.  Polyakov  E. V.  Gorshanov  D. L.  Pogodin  M. A. 《Astrophysics》2021,64(2):160-171
Astrophysics - This paper is a continuation of our earlier work devoted to determining the orbit and mass of the star 61 Cyg and the changes in the photometric characteristics of its components....  相似文献   
4.
Izvestiya, Atmospheric and Oceanic Physics - Results of assessment are presented for the relationship between the forest cover of small dry valleys and their spectral response through analysis of...  相似文献   
5.
Active wildfire seasons in the western U.S. warrant the evaluation of post-fire forest management strategies. Ground-based salvage logging is often used to recover economic loss of burned timber. In unburned forests, ground-based logging often follows best management practices by leaving undisturbed areas near streams called stream buffers. However, the effectiveness of these buffers has not been tested in a post-wildfire setting. This experiment tested buffer width effectiveness with a novel field-simulated rill experiment using sediment-laden runoff (25 g/L) released over 40 min at evenly timed flow rates (50, 100 and 150 L/min) to measure surface runoff travel length and sediment concentration under unburned and high and low soil burn severity conditions at 2-, 10- and 22-month post-fire. High severity areas 2-month post-fire had rill lengths of up to 100 m. Rill length significantly decreased over time as vegetation regrowth provided ground cover. Sediment concentration and sediment dropout rate also varied significantly by soil burn severity. Sediment concentrations were 19 g/L for the highest flow 2-month post-fire and reduced to 6.9–14 g/L 10-month post-fire due to abundant vegetation recovery. The amount of sediment dropping out of the flow consistently increased over the study period with the low burn severity rate of 1.15 g L−1 m−1 approaching the unburned rate of 1.29 g L−1 m−1 by 2-year post-fire. These results suggest that an often-used standard, 15 m buffer, was sufficient to contain surface runoff and reduce sediment concentration on unburned sites, however buffers on high burn severity sites need to be eight times greater (120 m) immediately after wildfire and four times greater (60 m) 1-year post-fire. Low burn severity areas 1-year post-fire may need to be only twice the width of an unburned buffer (30 m), and 2-year post-fire these could return to unburned widths.  相似文献   
6.
Oceanology - New data are presented on sedimentary matter fluxes and its main components along a meridional transect (59°30′ N) in the North Atlantic under the effect of multidirectional...  相似文献   
7.
Doklady Earth Sciences - Using observations from a large-scale seismic station network, we built a seismic tomography model of velocity anomalies for longitudinal (P-wave) and transverse (S-wave)...  相似文献   
8.
Geology of Ore Deposits - The recognition of the Fouta Djallon–Mandingo territory as an independent bauxite province is substantiated. It is confined to the morphostructure of the same name...  相似文献   
9.
Doklady Earth Sciences - The results of an analysis of changes in the atmospheric air quality in Moscow during the lockdown period and the decline in business activity caused by the COVID-19...  相似文献   
10.
The notion of vulnerability has acquired a significant role in discussions around reducing risk and identifying vulnerable groups, which is particularly important for targeting risk‐reducing policy and practice. Through ten semi‐structured interviews with 24 stakeholders, this study collected local perceptions on the following groups considered most vulnerable in Laamu Atoll, Maldives: youth and children, women, the elderly, people with disabilities, displaced persons and migrants, and farmers. In doing this, the significance of intersecting categories of identity for understanding vulnerability emerged and was explored; an approach that is often absent or scarcely applied in studies that identify vulnerable groups in the Maldives and elsewhere. Intersections between location, youth and gender or disability, as well as gender and marital status emerged as relevant for the Laamu Atoll context. Although this study acknowledges the incompleteness of its intersectional analysis, these findings provide important preliminary insights into the role of intersectionality in shaping vulnerability experience. To enhance scholarship on vulnerability, future studies could further explore intersectionality in Laamu Atoll and the Maldives using this study as a base and also improve its practical applicability for policy and practice.  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