全文获取类型
收费全文 | 16108篇 |
免费 | 3706篇 |
国内免费 | 5450篇 |
专业分类
测绘学 | 1252篇 |
大气科学 | 1482篇 |
地球物理 | 3500篇 |
地质学 | 14381篇 |
海洋学 | 1268篇 |
天文学 | 34篇 |
综合类 | 1857篇 |
自然地理 | 1490篇 |
出版年
2024年 | 110篇 |
2023年 | 359篇 |
2022年 | 730篇 |
2021年 | 864篇 |
2020年 | 846篇 |
2019年 | 1125篇 |
2018年 | 829篇 |
2017年 | 861篇 |
2016年 | 964篇 |
2015年 | 1030篇 |
2014年 | 1276篇 |
2013年 | 1044篇 |
2012年 | 1253篇 |
2011年 | 1228篇 |
2010年 | 985篇 |
2009年 | 1126篇 |
2008年 | 1049篇 |
2007年 | 1090篇 |
2006年 | 1056篇 |
2005年 | 870篇 |
2004年 | 852篇 |
2003年 | 752篇 |
2002年 | 644篇 |
2001年 | 564篇 |
2000年 | 574篇 |
1999年 | 503篇 |
1998年 | 452篇 |
1997年 | 411篇 |
1996年 | 340篇 |
1995年 | 325篇 |
1994年 | 265篇 |
1993年 | 231篇 |
1992年 | 190篇 |
1991年 | 118篇 |
1990年 | 107篇 |
1989年 | 76篇 |
1988年 | 52篇 |
1987年 | 50篇 |
1986年 | 29篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1979年 | 9篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1954年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
21.
基于拖带坐标法建立了岩层大变形的一维非线性微分方程,然后用解析与数值方法研究了变刚度、可伸缩岩层在侧向压力及自重作用下的分叉特性,初步揭示了褶皱岩层初始挠曲的形成机理。 相似文献
22.
I INTRODUCTIONWetland has very important effect on retainingwater and against drought, regUlating climate, controlling soil erosion and so on ac. Today men often attachimportance to economic effect of wetland reclamation,but neglect and destroy other functions and effectswhich result in blind wetland development, a lot ofwetland degeneration. The area of freshwater wetland inthe 1950s was 134 x 10'ha, but in the 1970s 70% hadchanged into farmland (MITSCH, 1993). The area ofwetland in d… 相似文献
23.
介绍了自动高精度测距系统。该系统能以5×10-7的测距精度测定多个观测点的形变,可作为跨断层动态连续观测的新仪器。 相似文献
24.
北天山东段康古尔塔格带是晚古生代塔里木板块和准噶尔板块碰撞的结果。它是一条复杂的、强烈的高应变带.并具有独特的变形机制、应变序列以及构造变形。本文运用构造-地层研究方法对该碰撞带的构造特征加以分析和研究。 相似文献
25.
A. P. M. Vaughan L. A. Dowling F. J. G. Mitchell S.‐E. Lauritzen A. M. McCabe P. Coxon 《第四纪科学杂志》2004,19(6):577-590
Organic‐rich deposits, uncovered during overburden removal from mantled gypsum karst at Knocknacran opencast gypsum mine, Co. Monaghan, are the best candidate to date for a last interglacial record in Ireland. The two till and organic‐rich deposits (preserved at different quarry elevations) were emplaced on to a Tertiary dolerite surface during high‐energy flood events and subsequently folded and faulted by movement towards sinkholes in underlying gypsum. Uranium–thorium disequilibrium dating suggests that the organic‐rich deposits in the upper section were hydrologically isolated at ca. 41 ka and those in the lower section at ca. 86 ka. Interpretation of the pollen content, although tentative because of the depositional and post‐depositional history of the material, suggests that the organic material originated in a warm stage possibly warmer than the post‐Eemian interstadials. The unusual setting of preservation may indicate that in situ, last interglacial deposits have generally been removed by erosion in Ireland. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
26.
寇新建 《大地测量与地球动力学》1994,(3)
由于观测条件的变化,观测值方差将产生随机波动。本文根据Bayes估计理论,推导了线性模型待估参数的分布函数及观测值方差估计公式,并将其用于位移检验。计算结果表明,在同样的置信度下,本方法更符合实际。文中还对参数估值的统计性质进行了讨论。 相似文献
27.
28.
29.
I.IN~crIOXLocatedinthecoddlepatofTallmBasin,withanareaof33.76X104klnZ,theTaldirnakan~isinthehinterlandofEurasia.Blockedbythehighmountainsaround,vapourofoceancanhardlyreachthedesert.APartfromthis,asthedeSertisinthesinkingcompensationareaoftheascensionalaircurrentaamstheQinghal-XIZangPlateau,itSprecipitationisrareandtheevaporationcapacityisintensealltheyearround.Allthesecontributetotheformationsofthetypifydrydesertclimate.Theacidityindexofthedesertandthearoundregionisashighasmorethan50,w… 相似文献
30.
Based on the Germany Koldwey Station's 1994-2003 conventional observation hourly data, this paper conducts a statistical analysis on the short-term climate characteristics for an arctic tundra region (Ny-(A)lesund island) where our first arctic expedition station (Huanghe Station) was located. Affected by the North Atlantic warming current, this area has a humid temperate climate, and the air temperature at Ny-(A)lesund rose above 0 ℃ even during deep winter season during our research period. The wind speed in this area was low and appeared most at southeast direction. We find that the temperature at Ny-(A)lesund rose in the faster rate (0.68 ℃/10 a) than those at the whole Arctic area. Compared with the floating ices where our expedition conducted in the Arctic, Ny-(A)lesund was warmer and more humid and had lower wind speed. Comparison of the near surface air temperature derived by NCEP/NCAR reanalysis to the conventional measurements conducted at the Koldwey site in Ny-(A)lesund area shows a good agreement for winter season and a significant difference for summer season. 相似文献