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   1418573篇
  免费   40155篇
  国内免费   14779篇
化学   722436篇
晶体学   19467篇
力学   79267篇
综合类   415篇
数学   250318篇
物理学   401604篇
  2021年   15596篇
  2020年   18200篇
  2019年   18486篇
  2018年   15276篇
  2017年   13523篇
  2016年   30918篇
  2015年   23488篇
  2014年   33809篇
  2013年   78816篇
  2012年   44908篇
  2011年   42917篇
  2010年   41547篇
  2009年   43616篇
  2008年   39979篇
  2007年   35413篇
  2006年   40526篇
  2005年   32769篇
  2004年   33008篇
  2003年   30735篇
  2002年   31474篇
  2001年   31421篇
  2000年   27045篇
  1999年   24369篇
  1998年   22333篇
  1997年   22317篇
  1996年   22386篇
  1995年   20265篇
  1994年   19616篇
  1993年   18931篇
  1992年   19170篇
  1991年   19370篇
  1990年   18505篇
  1989年   18373篇
  1988年   17887篇
  1987年   17839篇
  1986年   16715篇
  1985年   23047篇
  1984年   24150篇
  1983年   20217篇
  1982年   21831篇
  1981年   21028篇
  1980年   20361篇
  1979年   20344篇
  1978年   21515篇
  1977年   21257篇
  1976年   20954篇
  1975年   19641篇
  1974年   19232篇
  1973年   19760篇
  1972年   14276篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Makarov  G. N. 《JETP Letters》2022,115(11):660-666
JETP Letters - Using the spectroscopic data on the 235UF6 and 238UF6 molecules and on the lasing frequencies of CF4 and para-H2 lasers and recent results, a method has been proposed to increase the...  相似文献   
62.
Knyazev  Yu. V.  Kazak  N. V.  Gavrichkov  V. A.  Polukeev  S. I.  Ovchinnikov  S. G. 《JETP Letters》2022,116(8):567-573
JETP Letters - Changes in the magnetic properties of FeBO3 single crystals in the course of spin crossover occurring with increasing pressure up to 63 GPa are studied both experimentally and...  相似文献   
63.
Chemistry of Heterocyclic Compounds - 2-Imino-2,5-dihydrofurans are a highly valuable class of heterocyclic compounds that show versatile biological activity and are used in diverse fields of...  相似文献   
64.
Low-flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for MS have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow LC, the types of columns employed, and strategies for multidimensionality of separations, which are key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend toward biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy-to-use platform.  相似文献   
65.
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field.  相似文献   
66.
Hua  Saixiang  Zhu  Huichao  Wang  Xiao  Wu  Mingyuan  Wu  Qingyun  Liu  Jiuyi  Yang  Jianjun  Zhang  Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,...  相似文献   
67.
Journal of Analytical Chemistry - The present study reports the development of a magnetic polyethylene glycol nanocomposite based on graphite reinforcement carbon paste electrode for the sensitive...  相似文献   
68.

A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.

  相似文献   
69.
Russian Journal of Organic Chemistry - A highly efficient green protocol has been proposed for the synthesis of symmetrical S-aryl arenesulfonothioates by irradiation of N-hydroxy arenesulfonamides...  相似文献   
70.
Numerical Algorithms - In this work, we propose a fractional extension of the one-dimensional nonlinear vibration problem on an elastic string. The fractional problem is governed by a hyperbolic...  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