首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   31976篇
  免费   10207篇
  国内免费   2676篇
地球科学   44859篇
  2025年   200篇
  2024年   715篇
  2023年   888篇
  2022年   1385篇
  2021年   1619篇
  2020年   1562篇
  2019年   1396篇
  2018年   1658篇
  2017年   1538篇
  2016年   1777篇
  2015年   1360篇
  2014年   1852篇
  2013年   1604篇
  2012年   1542篇
  2011年   1620篇
  2010年   1751篇
  2009年   1724篇
  2008年   1443篇
  2007年   1398篇
  2006年   1191篇
  2005年   1083篇
  2004年   872篇
  2003年   873篇
  2002年   868篇
  2001年   831篇
  2000年   1030篇
  1999年   1469篇
  1998年   1245篇
  1997年   1326篇
  1996年   1098篇
  1995年   1017篇
  1994年   907篇
  1993年   805篇
  1992年   652篇
  1991年   484篇
  1990年   338篇
  1989年   367篇
  1988年   314篇
  1987年   227篇
  1986年   186篇
  1985年   140篇
  1984年   114篇
  1983年   93篇
  1982年   81篇
  1981年   59篇
  1980年   49篇
  1979年   32篇
  1978年   16篇
  1977年   7篇
  1958年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
In order to make more accurate estimates of the physical parameters of extrasolar planets, the observation and research on the phenomena of transits of the 7 known stars with the planetary systems TrES-1, TrES-3, XO-2, WASP-1, WASP-2, WASP-3 and HAT-P-7 are carried out with the 1-m reflecting telescope at Shandong University Weihai Astronomical Observatory/Weihai Municipal Astronomical Observatory. The fundamental conditions of the observation and data processing are introduced, and the transit light curves as well as the parameters of some planets derived from them are given. At the same time, when the results are summarized and analyzed, the prospects for the more in-depth and detailed researches which will be further carried out are also described.  相似文献   
72.
大同盆地现今构造活动及地壳应力场特征   总被引:5,自引:1,他引:5  
大量震源机制结果推断出大同分轩现代地壳应力场和主压应力方向为NE-NEE,仰角变化不定,主张应力方向为NW-NNW,仰角很小的结论。这与区域构造应力场NE-NEE向挤压作用的结果相符,另据大同一阳高6.1级、5.8级地震的震源机制结果得出,大同一阳高地震的孕震应力场与华北区域应力场相一致,而不是受本地局部小区域应力场的控制的结论。  相似文献   
73.
Zhang  Chengli  Hu  Bozhou  Wang  Peng  Fu  Xiaofei  Song  Guoliang  Liu  Haoliang 《Natural Resources Research》2020,29(3):2191-2207
Natural Resources Research - Alkali–surfactant–polymer (ASP)-produced effluent contains polymer, alkali and surfactant, and it has higher content of suspended oil droplets and suspended...  相似文献   
74.
A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological...  相似文献   
75.
ASP是可以与数据库和其它程序进行交互的一种比较简单、方便的编程工具,被最广泛的运用于各种动态网站中。本文集中介绍了ASP程序设计容易产生的几种错误类型和产生错误时的处理方式。  相似文献   
76.
利用MATLAB实现图像处理与分析   总被引:1,自引:0,他引:1  
本文通过对图像的均衡操作、二值图像的处理、小波去噪等实例,介绍了MATLAB进行图像处理和分析的实用方法与技巧,它对各种软钉包、进行图像处理和分析等,提供了高效便捷的方法。  相似文献   
77.
    
The Taiwanese‐American Occultation Survey (TAOS) seeks to determine the number and size spectrum for small (∼3 km) bodies in the Kuiper Belt. This will be accomplished by searching for the brief occultations of bright stars (R ∼ 14) by these objects. We have designed and built a special purpose photometric monitoring system for this purpose. TAOS comprises four 50 cm telescopes, each equipped with a 2048 × 2048 pixel CCD camera, in a compact array located in the central highlands of Taiwan. TAOS will monitor up to 2 000 stars at 5 Hz. The system went into scientific operation in the autumn of 2005. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
78.
Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic activity on climate change have been truly recorded in peat, since it is a major archive of volcanic eruption incidents. A section of sand was identified as tephra from the Jinchuan peat, Jilin Province, China, for the grains look like slag with surface bubbles and pits, characterized by high porosity, and loose structure with irregular edges and corners. According to the peat characteristics of uniform deposition, the tephra was dated at 2002–1976 a B.P. by way of linear interpolation, so the time of volcanic eruption was 15 B.C.–26 A.D. (the calibrated age). While the geochemical characteristics of tephra in this study are quite the same as those of tephra from the Jinlongdingzi volcano at Longgang and from alkaline basaltic magma, with the contents of SiO2<55%, and the similar contents to Al2O3 and Fe, but the contents of Na2O>K2O. We speculated that the tephra in this study came from the Longgang volcano group. Compared with 11 recorded volcanic eruption events as shown on the carbon and oxygen isotope curves of the Jinchuan peat cellulose, it is obviously seen that adjacent or large-scale volcanic eruptions are precisely corresponding to the minimum temperature and humidity. It seems that these volcanic eruptions indeed affected the local climate, leading to the drop of regional temperature and humidity. As a result, there was prevailing a cold and dry climate there, and all these changes can be well recorded in peat. So the comparison of volcanic eruption events with information about climate change developed from peat, can provide strong evidence for the impact of volcanism on climate change.  相似文献   
79.
随着有色金属采选建设项目的增加,选矿生产的耗水量日渐为公众及管理部门所关注,在整个生产过程中,除精矿粉中会带走精矿重量约10%的水分外,绝大部分排放水是尾矿矿浆经输送至尾矿库澄清后排出的。因此从环境保护及提高水的利用率角度考虑,选矿废水应回用,而尾矿的排放方式又对生产用水回用率有着很大的影响。  相似文献   
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号

京公网安备 11010802026262号