首页 | 本学科首页   官方微博 | 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   172495篇
  免费   2485篇
  国内免费   1230篇
化学   69314篇
晶体学   2658篇
力学   11093篇
综合类   73篇
数学   31088篇
物理学   61984篇
  2022年   666篇
  2021年   762篇
  2020年   780篇
  2019年   741篇
  2018年   10345篇
  2017年   11223篇
  2016年   5648篇
  2015年   1978篇
  2014年   1550篇
  2013年   3241篇
  2012年   7602篇
  2011年   17053篇
  2010年   10360篇
  2009年   10502篇
  2008年   14654篇
  2007年   18185篇
  2006年   3163篇
  2005年   9989篇
  2004年   6039篇
  2003年   5649篇
  2002年   3388篇
  2001年   3356篇
  2000年   2650篇
  1999年   1779篇
  1998年   1301篇
  1997年   1238篇
  1996年   1234篇
  1995年   1023篇
  1994年   915篇
  1993年   817篇
  1992年   1106篇
  1991年   1089篇
  1990年   996篇
  1989年   895篇
  1988年   871篇
  1987年   919篇
  1986年   771篇
  1985年   1002篇
  1984年   958篇
  1983年   683篇
  1982年   670篇
  1981年   628篇
  1980年   595篇
  1979年   735篇
  1978年   766篇
  1977年   691篇
  1976年   644篇
  1975年   537篇
  1974年   574篇
  1973年   545篇
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
31.
The Ramanujan Journal - Inspired by Andrews and Merca’s recent work on the number of even parts over all partitions into distinct parts, we introduce a new kind of Beck type identities, which...  相似文献   
32.
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme.  相似文献   
33.
Ding  Hao  Wang  Jin-Ting  Lu  Li-Qiao  Pan  Jian-Wen 《Nonlinear dynamics》2021,104(4):3365-3384
Nonlinear Dynamics - Conventional tuned liquid column dampers (TLCDs) are deficient in multidirectionality. In contrast, toroidal TLCDs are designed to extend the application to multidirectional...  相似文献   
34.
35.
Ding  Q.  Yao  M.  Wu  Sh.  Zeng  M.  Xue  N.  Wu  D.  Xu  J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the...  相似文献   
36.
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.  相似文献   
37.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
38.
39.
40.
The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments.  相似文献   
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