全文获取类型
收费全文 | 45232篇 |
免费 | 441篇 |
国内免费 | 561篇 |
专业分类
测绘学 | 994篇 |
大气科学 | 2367篇 |
地球物理 | 8698篇 |
地质学 | 17742篇 |
海洋学 | 4192篇 |
天文学 | 10572篇 |
综合类 | 145篇 |
自然地理 | 1524篇 |
出版年
2022年 | 549篇 |
2021年 | 773篇 |
2020年 | 828篇 |
2019年 | 907篇 |
2018年 | 1927篇 |
2017年 | 1735篇 |
2016年 | 1928篇 |
2015年 | 782篇 |
2014年 | 1692篇 |
2013年 | 2486篇 |
2012年 | 1861篇 |
2011年 | 2294篇 |
2010年 | 2087篇 |
2009年 | 2443篇 |
2008年 | 2118篇 |
2007年 | 2307篇 |
2006年 | 2084篇 |
2005年 | 1202篇 |
2004年 | 1104篇 |
2003年 | 1075篇 |
2002年 | 1002篇 |
2001年 | 995篇 |
2000年 | 840篇 |
1999年 | 609篇 |
1998年 | 610篇 |
1997年 | 633篇 |
1996年 | 501篇 |
1995年 | 495篇 |
1994年 | 452篇 |
1993年 | 383篇 |
1992年 | 359篇 |
1991年 | 382篇 |
1990年 | 422篇 |
1989年 | 356篇 |
1988年 | 328篇 |
1987年 | 366篇 |
1986年 | 269篇 |
1985年 | 375篇 |
1984年 | 385篇 |
1983年 | 380篇 |
1982年 | 360篇 |
1981年 | 324篇 |
1980年 | 323篇 |
1979年 | 260篇 |
1978年 | 282篇 |
1977年 | 257篇 |
1976年 | 230篇 |
1975年 | 224篇 |
1974年 | 207篇 |
1973年 | 256篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
M. V. Martynova 《Water Resources》2012,39(2):223-228
The causes of the high Mn concentration in the solid phase and pore solution of bottom sediments in the Mozhaisk Reservoir
are discussed. Regularities are identified in variations the concentrations of Mn forms in reservoir deposits from its upper
part to the dam. 相似文献
72.
A special system of canonical variables is considered. An algorithm for expanding the principal functions of Keplerian motion in new elements is presented. The advantage of the proposed system is a relatively small number of terms in the classical expansions of the unperturbed two-body problem. A method for expanding the time derivatives of the rectangular coordinates is proposed. Some estimates of the number of terms in the presented expansions have been obtained through numerical experiments. 相似文献
73.
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
74.
O. V. Ilyina N. S. Tychkov A. M. Agashev A. V. Golovin A. E. Izokh O. A. Kozmenko N. P. Pokhilenko 《Doklady Earth Sciences》2016,467(2):408-411
The results of the first study of the PGE distribution in deformed lherzolites of the Udachnaya kimberlite pipe (Yakutia) are presented here. The complex character of evolution of the PGE composition in the Deformed lherzolites is assumed to be the result of silicate metasomatism. At the first stage, growth in the amount of clinopyroxene and garnet in the rock is accompanied by a decrease in the concentration of the compatible PGE (Os, Ir). During the final stage, the rock is enriched with incompatible PGE (Pt, Pd) and Re possible due to precipitation of submicron-sized particles of sulfides in the interstitial space of these mantle rocks. 相似文献
75.
The first small active regions of the last two new cycles seem to be formed, in its very first, preparatory stage, close to the equator with uncertain magnetic orientation, and as secondary products at the periphery of equatorial `magnetic bubbles' of the new magnetic flux still belonging to the old cycle. At the real beginning of the new cycle, at the periphery of its higher-latitude `magnetic bubbles', the opposite applies to the secondary regions of the ending cycle. It seems that two modes of magnetic flux supply the visible layers of the photosphere during the cycle transition phase: the emergence of the magnetic flux from the depth of the convective zone, and the mutual interaction of the earlier emerging fluxes, or the action of the `local dynamo', giving rise to the new local magnetic field concentrations. 相似文献
76.
The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied. 相似文献
77.
The heavy metal inventory and the ecological risk of the estuarine sediments in Hailing Bay, an important maricultural zone along the southern coast of China, were investigated. Results show that the surface sediments were mainly polluted by As (2.17-20.34 mg/kg), Ni (1.37-42.50mg/kg), Cu (1.21-58.84 mg/kg) and Zn (11.69-219.22 mg/kg). Furthermore, the aquafarming zone was significantly more polluted than the non-aquafarming zone, and cluster analysis suggested additional sources of heavy metal input in the aquafarming zone. As, Cr, Cu, Ni, Pb and Zn were mainly present in the non-bioavailable residual form in the surface sediments, whereas Cd was predominantly in the highly mobile acid soluble and reducible fractions. The ecological risk of the polluted sediments stemmed mainly from Cd, and from As, Cu and Pb to less degrees. The highest potential risks occurred near the aquaculture base, indicating the need to control heavy metal inputs from aquafarming activities. 相似文献
78.
The distribution of sites where globular clusters have crossed the Galactic disk during the last 100 million years has been analyzed using the most recent kinematic data for 133 globular clusters (GCs). ThreeGCs (NGC 6341, NGC 7078, and ω Cen) whose distances between the positions where they crossed the Galactic disk and trajectories of the Gould Belt are less than 20% of their heliocentric distances at the crossing time (82, 98, and 96 million years ago, respectively) have been identified. For each of the clusters, this was their next to last, rather than their last, crossing of the Galactic disk. The passage of any one of these three GCs through the disk could potentially have initiated the formation of the Gould Belt. 相似文献
79.
The eleventh list of faint late M and carbon type stars detected on the plates of the First Byurakan Spectral Survey in zone -7° -3° and covering about 1000 square degrees is presented. From 126 detected stars, 88 are newly discovered objects: they are 6 carbon stars, 8 carbon star candidates, and 74 M-type stars; among the latter 38 (26 PSC + 12 FSC) are unclassified IRAS sources, and one object is an unclassified ROSAT source. Distances to the 6 newly discovered early-type carbon stars are estimated. Equatorial coordinates, red magnitudes, and spectral classes determined from the Palomar E-charts are provided. The lack of optical counterparts on Palomar O and E maps for two detected late M-type stars indicates a large variability in brightnesses of these objects (amplitude not smaller than 7.0 magnitude). 相似文献
80.