全文获取类型
收费全文 | 51519篇 |
免费 | 444篇 |
国内免费 | 360篇 |
专业分类
测绘学 | 1343篇 |
大气科学 | 3139篇 |
地球物理 | 10000篇 |
地质学 | 19029篇 |
海洋学 | 4450篇 |
天文学 | 12249篇 |
综合类 | 195篇 |
自然地理 | 1918篇 |
出版年
2022年 | 475篇 |
2021年 | 742篇 |
2020年 | 784篇 |
2019年 | 845篇 |
2018年 | 1814篇 |
2017年 | 1658篇 |
2016年 | 1902篇 |
2015年 | 873篇 |
2014年 | 1745篇 |
2013年 | 2738篇 |
2012年 | 1984篇 |
2011年 | 2345篇 |
2010年 | 2115篇 |
2009年 | 2495篇 |
2008年 | 2164篇 |
2007年 | 2307篇 |
2006年 | 2176篇 |
2005年 | 1387篇 |
2004年 | 1259篇 |
2003年 | 1246篇 |
2002年 | 1209篇 |
2001年 | 1145篇 |
2000年 | 1032篇 |
1999年 | 811篇 |
1998年 | 794篇 |
1997年 | 824篇 |
1996年 | 684篇 |
1995年 | 664篇 |
1994年 | 620篇 |
1993年 | 521篇 |
1992年 | 490篇 |
1991年 | 521篇 |
1990年 | 561篇 |
1989年 | 479篇 |
1988年 | 451篇 |
1987年 | 526篇 |
1986年 | 417篇 |
1985年 | 556篇 |
1984年 | 587篇 |
1983年 | 569篇 |
1982年 | 555篇 |
1981年 | 453篇 |
1980年 | 486篇 |
1979年 | 393篇 |
1978年 | 432篇 |
1977年 | 393篇 |
1976年 | 333篇 |
1975年 | 336篇 |
1974年 | 347篇 |
1973年 | 375篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Izvestiya, Physics of the Solid Earth - Abstract—In their paper published in Izvestiya, Physics of the Solid Earth, G.A. Sobolev et al. (2020) discussed the results of their study. Firstly,... 相似文献
43.
Roy C. Bartholomay Brian V. Twining Peter E. Rose 《Ground Water Monitoring & Remediation》2014,34(1):79-88
Starting in 2008, a 4‐year tracer study was conducted to evaluate ambient changes in groundwater concentrations of a 1,3,6‐naphthalene trisulfonate tracer that was added to drill water. Samples were collected under open borehole conditions and after installing a multilevel groundwater monitoring system completed with 11 discrete monitoring zones within dense and fractured basalt and sediment layers in the eastern Snake River aquifer. The study was done in cooperation with the U.S. Department of Energy to test whether ambient fracture flow conditions were sufficient to remove the effects of injected drill water prior to sample collection. Results from thief samples indicated that the tracer was present in minor concentrations 28 days after coring, but was not present 6 months after coring or 7 days after reaming the borehole. Results from sampling the multilevel monitoring system indicated that small concentrations of the tracer remained in 5 of 10 zones during some period after installation. All concentrations were several orders of magnitude lower than the initial concentrations in the drill water. The ports that had remnant concentrations of the tracer were either located near sediment layers or were located in dense basalt, which suggests limited groundwater flow near these ports. The ports completed in well‐fractured and vesicular basalt had no detectable concentrations. 相似文献
44.
45.
Dr. E. K. Walton 《International Journal of Earth Sciences》1960,50(1):63-77
Lower Palaeozoic successions in the Southern Uplands are much thicker than previously supposed and sedimentation may have lasted well into Ludlow times. Volcanic rocks are Arenig and Glenkiln in age and are often interbedded with greywackes and shales. Lapworth's concept of the structure as an anticlinorium and a synclinorium is rejected and it is suggested that the rocks have been folded into a series of compound monoclines which face north-westwards. These are probably cut by strike faults which bring up the older beds to the north.
Zusammenfassung Die altpaläozoischen Schichtfolgen in den Südlichen Hochlanden sind viel mächtiger, als bisher angenommen wurde, und die Ablagerung kann bis ins Ludlow gereicht haben. Vulkanite haben Arenig- und Glenkiln-Alter; sie wechsellagern oft mit Grauwacken und Tonschiefern.Lapworths Vorstellung, der tektonische Bau sei ein Antiklinorium und ein Synklinorium, wird bestritten. Es wird angenommen, daß die Gesteine zu zusammengesetzten Monoklinen gefaltet wurden, deren steile Flügel nordwestwärts weisen. Sie werden wahrscheinlich durch streichende Verwerfungen zerschnitten, die die älteren Schichten im Norden herausheben.相似文献
46.
Distribution of the trace elements Cr, Cu, Ni, Pb and Zn in surficial sediments of the river/sea environment in Danang –
Hoian area (Vietnam) was investigated to examine the degree of metal pollution caused by anthropogenic activities. Point sources
from domestic and industrial wastes are identified as dominant contributors of trace element accumulation. Surficial sediments
of Hoian River show extremely high total concentrations of Cu (Average Concentration 295 μg/g), Ni (AC 112 μg/g), Pb (AC 396 μg/g)
and Zn (AC 429 μg/g) that exceed assigned safety levels ER-M. Similarly, the sediments of Han River show high Pb (AC 188 μg/g)
and Zn (AC 282 μg/g) contents. In marine sediments of Thanhbinh beach Pb is also enriched (138 μg/g) above guideline levels.
In contrast the sediments of the Cude River are dominated by trace element concentrations close to background values.
Received: 17 December 1998 · Accepted: 6 May 1999 相似文献
47.
48.
Reply to comment on ‘Up‐scaling potential impacts on water flows from agricultural water interventions: opportunities and trade‐offs in the Osman Sagar catchment,Musi sub‐basin,India’. Hydrological Processes 27: 3905–3921 by Bouma et al.,
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kaushal K. Garg Suhas P. Wani Jennie Barron Louise Karlberg Johan Rockstrom 《水文研究》2014,28(8):3352-3355
49.
Dubey Om Prakash Niwas Sri Awasthi A. K. 《Journal of the Indian Society of Remote Sensing》1986,14(1):39-44
Journal of the Indian Society of Remote Sensing - Development activities must be compatible for possibilities and limitation of natural environment and resources. Predevelopmental analysis must... 相似文献
50.
Seasonal hydrological forecasts, or outlooks, can potentially provide water managers with estimates of river flows and water resources for a lead time of several months ahead. An experimental modelling tool for national hydrological outlooks has been developed which combines a hydrological model estimate of sub‐surface water storage across Britain with a range of seasonal rainfall forecasts to provide estimates of area‐wide hydrological conditions up to a few months ahead. The link is made between a deficit in sub‐surface water storage and a requirement for additional rainfall over subsequent months to enable sub‐surface water storage and river flow to return to mean monthly values. The new scheme is assessed over a recent period which includes the termination of the drought that affected much of Britain in the first few months of 2012. An illustration is provided of its use to obtain return‐period estimates of the ‘rainfall required’ to ease drought conditions; these are well in excess of 200 years for several regions of the country, for termination within a month of 1 April 2012, and still exceed 40 years for termination within three months. National maps of sub‐surface water storage anomaly show for the first time the current spatial variability of drought severity. They can also be used to provide an indication of how a drought situation might develop in the next few months given a range of possible future rainfall scenarios. © 2013 CEH/Crown and John Wiley & Sons, Ltd. 相似文献