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   485115篇
  免费   5167篇
  国内免费   1432篇
化学   253835篇
晶体学   7980篇
力学   21882篇
综合类   8篇
数学   54700篇
物理学   153309篇
  2021年   3830篇
  2020年   4145篇
  2019年   4630篇
  2018年   6157篇
  2017年   6334篇
  2016年   9074篇
  2015年   5409篇
  2014年   8795篇
  2013年   22023篇
  2012年   16190篇
  2011年   19651篇
  2010年   14228篇
  2009年   14100篇
  2008年   17655篇
  2007年   17791篇
  2006年   16462篇
  2005年   14490篇
  2004年   13496篇
  2003年   11940篇
  2002年   11884篇
  2001年   14282篇
  2000年   10843篇
  1999年   8491篇
  1998年   7042篇
  1997年   6961篇
  1996年   6651篇
  1995年   5862篇
  1994年   5742篇
  1993年   5571篇
  1992年   6332篇
  1991年   6384篇
  1990年   6193篇
  1989年   6148篇
  1988年   5870篇
  1987年   6007篇
  1986年   5628篇
  1985年   7351篇
  1984年   7366篇
  1983年   6152篇
  1982年   6431篇
  1981年   6130篇
  1980年   6018篇
  1979年   6361篇
  1978年   6656篇
  1977年   6459篇
  1976年   6387篇
  1975年   6070篇
  1974年   5990篇
  1973年   6026篇
  1972年   4178篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
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   
22.

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   
23.
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   
24.
Mathematical Notes - Subspaces of the space of analytic functions on a convex domain in the complex plane that are invariant with respect to the differentiation operator are studied. The problem of...  相似文献   
25.
The requirement of green and sustainable materials to prepare heterogeneous catalysts has intensified for practical reasons over the past few decades. Carbohydrates are possibly the most plentiful and renewable organic materials in nature with inimitable physiochemical properties, plausible low-cost and large-scale production, and sustainability features could be exploited in the generation of nanostructured heterogeneous catalysts. This review article outlines the organic transformations catalyzed by diverse carbohydrate-based nanostructured catalysts in greener and environmentally friendly processes. Selected examples are highlighted for a variety of organic reactions exploiting the proposed catalysts’ reactivity and reusability, and interactions with the intrinsic nature of the applied carbohydrate supports; advantages and speculated challenges of the introduced catalysts are deliberated as well.  相似文献   
26.
The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3, by cyanostar macrocycles that are size-complementary to the inorganic BF4 progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R−BF3 anions.  相似文献   
27.
28.
Sun  J.  Yuan  H. 《Experimental Mechanics》2021,61(3):565-580
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients...  相似文献   
29.
Russian Physics Journal - The temperature dependences of the linear dielectric permittivity ε′ and the third harmonic coefficient γ3ω for nanocomposites obtained by embedding a...  相似文献   
30.

We show that near periodic rivet chains that connect two Kirchhoff plates and are modeled by point Sobolev transmission conditions, Rayleigh waves arise, propagate along the chains, and decay exponentially in the orthogonal direction. Under additional geometric conditions we discover the standing (periodic) waves that carry no energy.

  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