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   731217篇
  免费   6561篇
  国内免费   1773篇
化学   363385篇
晶体学   8638篇
力学   38174篇
综合类   26篇
数学   105659篇
物理学   223669篇
  2021年   5805篇
  2020年   6520篇
  2019年   7321篇
  2018年   13760篇
  2017年   14100篇
  2016年   15900篇
  2015年   8073篇
  2014年   12821篇
  2013年   30242篇
  2012年   25305篇
  2011年   33754篇
  2010年   23874篇
  2009年   23720篇
  2008年   31083篇
  2007年   32970篇
  2006年   24009篇
  2005年   24079篇
  2004年   21154篇
  2003年   19626篇
  2002年   18531篇
  2001年   18893篇
  2000年   14900篇
  1999年   11448篇
  1998年   9910篇
  1997年   9673篇
  1996年   8659篇
  1995年   8192篇
  1994年   8328篇
  1993年   7875篇
  1992年   8461篇
  1991年   8919篇
  1990年   8580篇
  1989年   8334篇
  1988年   8267篇
  1987年   8153篇
  1986年   7723篇
  1985年   10087篇
  1984年   10667篇
  1983年   8967篇
  1982年   9305篇
  1981年   8816篇
  1980年   8505篇
  1979年   8946篇
  1978年   9430篇
  1977年   9276篇
  1976年   9290篇
  1975年   8783篇
  1974年   8683篇
  1973年   9036篇
  1972年   6535篇
排序方式: 共有10000条查询结果,搜索用时 812 毫秒
41.
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   
42.
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   
43.
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   
44.
45.
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   
46.
Crystallography Reports - Membrane proteins, including ion channels, became the focus of structural proteomics midway through the 20th century. Methods for studying ion channels are diverse and...  相似文献   
47.
Nonlinear Dynamics - Given a data-set of Ribonucleic acid (RNA) sequences we can infer the phylogenetics of the samples and tackle the information for scientific purposes. Based on current data and...  相似文献   
48.

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   
49.
Osipov  A. A. 《JETP Letters》2021,113(6):413-417
JETP Letters - The result of removing heavy particles with different mass from the theory spectrum can be described at low energy by the effective action, which is an asymptotic series in inverse...  相似文献   
50.
Optics and Spectroscopy - The current–voltage characteristics and photocurrent of “monolithic” diode optical pairs optically coupled by a substrate made of InAs common for them...  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