全文获取类型
收费全文 | 58988篇 |
免费 | 1045篇 |
国内免费 | 518篇 |
专业分类
测绘学 | 1425篇 |
大气科学 | 3736篇 |
地球物理 | 11849篇 |
地质学 | 21294篇 |
海洋学 | 5445篇 |
天文学 | 13053篇 |
综合类 | 175篇 |
自然地理 | 3574篇 |
出版年
2022年 | 959篇 |
2021年 | 1393篇 |
2020年 | 1373篇 |
2019年 | 1429篇 |
2018年 | 1588篇 |
2017年 | 1317篇 |
2016年 | 1444篇 |
2015年 | 927篇 |
2014年 | 1345篇 |
2013年 | 2732篇 |
2012年 | 1594篇 |
2011年 | 2198篇 |
2010年 | 1981篇 |
2009年 | 2670篇 |
2008年 | 2183篇 |
2007年 | 2163篇 |
2006年 | 2081篇 |
2005年 | 1552篇 |
2004年 | 1749篇 |
2003年 | 1701篇 |
2002年 | 1651篇 |
2001年 | 1394篇 |
2000年 | 1228篇 |
1999年 | 1083篇 |
1998年 | 1115篇 |
1997年 | 1103篇 |
1996年 | 792篇 |
1995年 | 836篇 |
1994年 | 787篇 |
1993年 | 669篇 |
1992年 | 652篇 |
1991年 | 670篇 |
1990年 | 710篇 |
1989年 | 614篇 |
1988年 | 577篇 |
1987年 | 712篇 |
1986年 | 664篇 |
1985年 | 800篇 |
1984年 | 912篇 |
1983年 | 838篇 |
1982年 | 701篇 |
1981年 | 757篇 |
1980年 | 616篇 |
1979年 | 598篇 |
1978年 | 606篇 |
1977年 | 545篇 |
1976年 | 506篇 |
1975年 | 516篇 |
1974年 | 513篇 |
1973年 | 540篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Opekunov A. Yu. Mitrofanova E. S. Spasskii V. V. Opekunova M. G. Sheinerman N. A. Chernyshova A. V. 《Water Resources》2020,47(2):282-293
Water Resources - The article gives the results of integrated studies of bottom sediments in four watercourses in the central St. Petersburg: the rivers of Ekateringofka, Okhta, Fontanka, and... 相似文献
72.
Water Resources - The possible input of nutrients-pollutants into water bodies in the Upper Volga basin from agricultural lands is evaluated for the case of the Yakhroma R. with a basin area of... 相似文献
73.
Boyuan Zhu Yao Yue Alistair G.L. Borthwick Wenjun Yu Enhang Liang Jinwu Tang Yuanfang Chai Yitian Li 《地球表面变化过程与地形》2020,45(11):2689-2705
In estuaries, the morphology of inland and offshore areas usually evolves synergistically. This study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo-center (where sediment deposition rate is maximum) of the Yangtze River estuary, under intense human interference. Integrated data analysis is provided on morphology, runoff discharge, and ebb partition ratio from 1950 to 2017. Channel-volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects. Ebb partition ratio and duration of discharge ≥ 60 000 m3 s-1 act as proxies for the water excavating force in branching channels and runoff intensity. It is found that deposition occurs in the lower/upper sub-reaches (or further downstream/upstream channels) of the inland north/south branching channels, and the offshore depo-center moves southward or southeastward, as runoff intensity grows; the reverse occurs as runoff intensity declines. This is because the horizontal circumfluence in the Yangtze estuary rotates clockwise as ebb partition ratios of the north/south branching channels increase/decrease for increasing runoff, and conversely rotates anticlockwise for decreasing runoff. Land reclamation activities, the Deepwater Channel Project, and the Qingcaosha Reservoir have impacted greatly on longitudinal changes of morphology in the North Branch and the South Passage and on ebb partition ratio variations in the North/South Channel and the North/South Passage. Dam-induced runoff flattening has enhanced deposition in the upper/lower sub-reaches of the north/south branching channels and caused northward movement of the offshore depo-center, except in areas affected by estuarine engineering projects. Dam-induced longitudinal evolution of branching channel morphology and offshore depo-center movement will likely persist in the future, given the ongoing construction of large cascade dams in the upper Yangtze and the completion of major projects in the Yangtze estuary. © 2020 John Wiley & Sons, Ltd. 相似文献
74.
Subsurface flow measurements using passive flux meters in variably-saturated cold-regions landscapes
To date, passive flux meters have predominantly been applied in temperate environments for tracking the movement of contaminants in groundwater. This study applies these instruments to reduce uncertainty in (typically instantaneous) flux measurements made in a low-gradient, wetland dominated, discontinuous permafrost environment. This method supports improved estimation of unsaturated and over-winter subsurface flows which are very difficult to quantify using hydraulic gradient-based approaches. Improved subsurface flow estimates can play a key role in understanding the water budget of this landscape. 相似文献
75.
Tsap Yu. T. Stepanov A. V. Kopylova Yu. G. Khaneichuk O. V. 《Geomagnetism and Aeronomy》2020,60(4):446-451
Geomagnetism and Aeronomy - The propagation of linear Alfvén waves with periods of 10–200 s from the photosphere to the solar chromosphere under the conditions of an isothermal... 相似文献
76.
Domrin V. I. Malova Kh. V. Popov V. Yu. Grigorenko E. E. Petrukovich A. A. 《Geomagnetism and Aeronomy》2020,60(2):171-183
Geomagnetism and Aeronomy - During geomagnetic substorms, the current sheet in the Earth’s magnetotail can transversely reduce in thickness from a few radii of the Earth (RE) to one to... 相似文献
77.
Geomagnetism and Aeronomy - Ionosonde measurements of the critical frequency of the ionospheric F2 layer (foF2) at Wakkanai station (Japan) are analyzed with the method of superposed epochs. The... 相似文献
78.
Geomagnetism and Aeronomy - Abstract—The main subject of the study is an analysis of time series of the width of annual rings of spruce and pine (D) that were obtained during the... 相似文献
79.
Water Resources - For the first time, data are given on cyanobacterial toxins entering tap water, supplied to the population of some cities in Yaroslavl oblast. The detection of microcystins with... 相似文献
80.
Water Resources - The results of long-term studies of a group of aufeis-forming Buluus groundwater sources are given. A stow, which has been formed by the spring, contains the drainage area of the... 相似文献