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   1435492篇
  免费   43797篇
  国内免费   16585篇
化学   734417篇
晶体学   18775篇
力学   80304篇
综合类   618篇
数学   251864篇
物理学   409896篇
  2021年   16051篇
  2020年   18838篇
  2019年   18994篇
  2018年   15501篇
  2017年   13517篇
  2016年   31581篇
  2015年   24157篇
  2014年   34698篇
  2013年   80052篇
  2012年   46281篇
  2011年   44498篇
  2010年   42235篇
  2009年   44227篇
  2008年   41033篇
  2007年   36311篇
  2006年   41972篇
  2005年   33322篇
  2004年   33812篇
  2003年   31338篇
  2002年   32085篇
  2001年   32711篇
  2000年   27802篇
  1999年   24896篇
  1998年   22750篇
  1997年   22687篇
  1996年   22599篇
  1995年   20452篇
  1994年   19710篇
  1993年   19112篇
  1992年   19402篇
  1991年   19619篇
  1990年   18755篇
  1989年   18618篇
  1988年   18097篇
  1987年   17995篇
  1986年   16959篇
  1985年   23255篇
  1984年   24234篇
  1983年   20283篇
  1982年   21423篇
  1981年   20604篇
  1980年   19893篇
  1979年   20401篇
  1978年   21546篇
  1977年   21282篇
  1976年   21046篇
  1975年   19772篇
  1974年   19400篇
  1973年   19913篇
  1972年   14433篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial...  相似文献   
62.
63.
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   
64.
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   
65.
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   
66.
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   
67.
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   
68.
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   
69.
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   
70.

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   
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