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   643727篇
  免费   5171篇
  国内免费   1664篇
化学   302735篇
晶体学   8748篇
力学   35873篇
综合类   17篇
数学   110863篇
物理学   192326篇
  2021年   5031篇
  2020年   5505篇
  2019年   6254篇
  2018年   20956篇
  2017年   21061篇
  2016年   18524篇
  2015年   7296篇
  2014年   10794篇
  2013年   23995篇
  2012年   23609篇
  2011年   36586篇
  2010年   24670篇
  2009年   25016篇
  2008年   31493篇
  2007年   35068篇
  2006年   19054篇
  2005年   21075篇
  2004年   18441篇
  2003年   17716篇
  2002年   15714篇
  2001年   15079篇
  2000年   11879篇
  1999年   8947篇
  1998年   7826篇
  1997年   7669篇
  1996年   7297篇
  1995年   6507篇
  1994年   6489篇
  1993年   6270篇
  1992年   6567篇
  1991年   7023篇
  1990年   6720篇
  1989年   6661篇
  1988年   6508篇
  1987年   6307篇
  1986年   6040篇
  1985年   7593篇
  1984年   7959篇
  1983年   6705篇
  1982年   6987篇
  1981年   6494篇
  1980年   6180篇
  1979年   6686篇
  1978年   6916篇
  1977年   6722篇
  1976年   6690篇
  1975年   6413篇
  1974年   6221篇
  1973年   6563篇
  1972年   4778篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Russian Journal of General Chemistry - A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan,...  相似文献   
22.
Central European Journal of Operations Research - We define a geometric transformation of Euclidean Travelling Salesman Problem (TSP) tours that leads to a new formulation of the TSP. For every...  相似文献   
23.
Differential Equations - For a spectrally controllable linear autonomous system with incommensurable delays, we construct a dynamic state feedback in the form of a differential-difference...  相似文献   
24.
Journal of Experimental and Theoretical Physics - The surface current density of charge carriers in two-dimensional doubly periodic n-type semiconductor superlattices in an external magnetic field...  相似文献   
25.
Russian Journal of Applied Chemistry - In September 1975, the head of Russian electrochemists, Academician A.N. Frumkin (1895–1976), in his report at the XI Mendeleev Congress on General and...  相似文献   
26.
Russian Journal of General Chemistry - Tungstophosphatozincates with the Keggin anion structure Kt5[PW11O39Zn(H2O)]?nH2O, Kt = Rb+, Cs+, (CH3)4N+; (C2H5)4N+ were synthesized. Their...  相似文献   
27.
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   
28.
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   
29.
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   
30.

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