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   407747篇
  免费   3428篇
  国内免费   953篇
化学   189747篇
晶体学   6450篇
力学   21390篇
综合类   7篇
数学   59852篇
物理学   134682篇
  2021年   3128篇
  2020年   3330篇
  2019年   3762篇
  2018年   11918篇
  2017年   12618篇
  2016年   10500篇
  2015年   4817篇
  2014年   7123篇
  2013年   16004篇
  2012年   15762篇
  2011年   24770篇
  2010年   16810篇
  2009年   16792篇
  2008年   21812篇
  2007年   24597篇
  2006年   12307篇
  2005年   15893篇
  2004年   12518篇
  2003年   11452篇
  2002年   9861篇
  2001年   10520篇
  2000年   7933篇
  1999年   5998篇
  1998年   5002篇
  1997年   4823篇
  1996年   4646篇
  1995年   3958篇
  1994年   3906篇
  1993年   3778篇
  1992年   4160篇
  1991年   4375篇
  1990年   4167篇
  1989年   4083篇
  1988年   3862篇
  1987年   3994篇
  1986年   3756篇
  1985年   4713篇
  1984年   4777篇
  1983年   3975篇
  1982年   4055篇
  1981年   3781篇
  1980年   3734篇
  1979年   4015篇
  1978年   4016篇
  1977年   3931篇
  1976年   3940篇
  1975年   3722篇
  1974年   3663篇
  1973年   3723篇
  1972年   2638篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A new derivative of dioxouranium(VI) salen complex, [UO2(L)(pyridine)], where [L = N,N′-Bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine] is synthesized and characterized by elemental analysis (C, H, N), FT-IR, ESI-MS spectrometry, UV/Vis, fluorescence, 1H and 13C NMR spectroscopy and thermal gravimetric (TG) study. Furthermore, the single crystal X-ray diffraction measurements of the complex were carried out at 100 and 273 K. The crystal structure measurements revealed that the complex has distorted pentagonal bipyramidal geometry with uranium atom located at the centre and bonded to two phenoxy oxygen and two azomethine nitrogen in tetradenate fashion and one nitrogen from pyridine making it seven coordinated. In addition, the photoluminescence property of the complex was also recorded.  相似文献   
42.
Russian Journal of Organic Chemistry - A procedure has been proposed for the synthesis of a series of substituted N-(1,3-thiazol-2-yl)-pyrimidin-2-amines and N-(pyrimidin-2-yl)thioureas by...  相似文献   
43.
44.
Saleh  Z. M.  Nasser  H.  Özkol  E.  Günöven  M.  Abak  K.  Canli  S.  Bek  A.  Turan  R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting...  相似文献   
45.
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   
46.
47.
48.
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism.  相似文献   
49.
50.
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