全文获取类型
收费全文 | 53196篇 |
免费 | 784篇 |
国内免费 | 351篇 |
专业分类
测绘学 | 1470篇 |
大气科学 | 4148篇 |
地球物理 | 10135篇 |
地质学 | 17726篇 |
海洋学 | 4499篇 |
天文学 | 12782篇 |
综合类 | 133篇 |
自然地理 | 3438篇 |
出版年
2021年 | 372篇 |
2020年 | 434篇 |
2019年 | 389篇 |
2018年 | 945篇 |
2017年 | 923篇 |
2016年 | 1188篇 |
2015年 | 786篇 |
2014年 | 1283篇 |
2013年 | 2616篇 |
2012年 | 1268篇 |
2011年 | 1752篇 |
2010年 | 1604篇 |
2009年 | 2154篇 |
2008年 | 1954篇 |
2007年 | 1917篇 |
2006年 | 1835篇 |
2005年 | 1719篇 |
2004年 | 1743篇 |
2003年 | 1600篇 |
2002年 | 1488篇 |
2001年 | 1324篇 |
2000年 | 1240篇 |
1999年 | 1187篇 |
1998年 | 1122篇 |
1997年 | 1110篇 |
1996年 | 875篇 |
1995年 | 870篇 |
1994年 | 827篇 |
1993年 | 762篇 |
1992年 | 744篇 |
1991年 | 705篇 |
1990年 | 801篇 |
1989年 | 689篇 |
1988年 | 661篇 |
1987年 | 760篇 |
1986年 | 636篇 |
1985年 | 840篇 |
1984年 | 959篇 |
1983年 | 925篇 |
1982年 | 870篇 |
1981年 | 836篇 |
1980年 | 729篇 |
1979年 | 705篇 |
1978年 | 708篇 |
1977年 | 642篇 |
1976年 | 610篇 |
1975年 | 535篇 |
1974年 | 611篇 |
1973年 | 600篇 |
1972年 | 366篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The paper presents the results of a photometric study of the hydroxyl bands (7–2) and (8–3) in the night airglow spectrum at Mt. Abu in the winter and spring of 1966–1972. The observed nocturnal variation differs from the variation expected from the theoretical studies of Hesstvedt, Hunt, Shimazaki and others. Instead of a gradual fall in intensity after sunset to shortly before sunrise, a peak in intensity is found at a time which changes from month to month and roughly coincides with the transit times of the X-ray star TAU (XR-1)-Crab Nebula. Anexplanation of the observed phenomenon is offered in terms of the increased energy output into the D and E regions of the atmospheres, increased eddy diffusion, and production, of additional O(3P) and O3 in the region 80–95 km. O3 reacting with H gives rise to OH*. 相似文献
62.
R. E. Bevan A.C.I.S. F. Insp. P.C. 《Aquatic Sciences - Research Across Boundaries》1969,31(2):322-334
Ohne Zusammenfassung 相似文献
63.
64.
65.
66.
67.
The problem of the diversity of the geochemical types of carbon dioxide waters (CDW) in petrografically and mineralogically uniform crystalline rock masses is solved with allowance made for the effect of different boundary conditions (physicochemical parameters) on the geochemical effect of interaction in the rock–water system. The formation of the entire geochemical spectrum of CDW in crystalline rock masses is shown to be explicable on the basis of a model of interaction in granite–water systems at different mass ratios of reacting rock (S) and water (L), different temperatures T, and equilibrium concentrations of dissolved CO2 (P
CO2). 相似文献
68.
69.
Summary In this paper we present a methodology for evaluating rain rates from a mix of satellite and surface based observations. The component data sets include the outgoing longwave radiation (OLR), microwave radiometric data from the special sensor microwave imager (SSM/I) and surface raingauge data from the World Weather Watch. We have noted some deficiencies in the SSM/I algorithm-based rain rate over land areas; the OLR-based rain rates exhibit a larger lateral spread and lower intensities than the observed rainfall structures. The proposed combined method assimilates these three data sets to provide improved fields of global tropical rainfall.With 3 Figures 相似文献
70.
I. Choe R. Ingalls J. M. Brown Y. Sato-Sorensen 《Physics and Chemistry of Minerals》1992,19(4):236-239
We have measured in situ Mössbauer transmission spectra of iron silicate spinel (γ-Fe2SiO4) in a diamond anvil cell at room temperature and pressures up to 16 GPa. The observed spectra show a doublet characteristic of the paramagnetic state. The isomer shift and quadrupole splitting at atmospheric pressure are 1.10 and 2.63 mm/s, respectively, which are smaller than those of fayalite (α-Fe2SiO4). Both the isomer shift and quadrupole splitting decrease linearly with pressure with slope of ?0.003(1) and ?0.020(1) mm/sec · GPa, respectively. This simple linear trend suggests that no electronic or polymorphic transitions occur under 16 GPa except for those due to the small and continuous changes of volume and local symmetry under pressure. On the basis of a crystalline field calculation, the negative pressure derivative of the quadrupole splitting is associated with a trend towards an ideal cubic symmetry of the oxygen sublattice. 相似文献