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   278245篇
  免费   3222篇
  国内免费   1011篇
化学   144586篇
晶体学   3135篇
力学   13032篇
综合类   64篇
数学   32452篇
物理学   89209篇
  2020年   2269篇
  2019年   2471篇
  2018年   4109篇
  2017年   4182篇
  2016年   5102篇
  2015年   3123篇
  2014年   4716篇
  2013年   11243篇
  2012年   9202篇
  2011年   10666篇
  2010年   7618篇
  2009年   7406篇
  2008年   9620篇
  2007年   9786篇
  2006年   9117篇
  2005年   10912篇
  2004年   10127篇
  2003年   8157篇
  2002年   6265篇
  2001年   7172篇
  2000年   5444篇
  1999年   4147篇
  1998年   3647篇
  1997年   3672篇
  1996年   3380篇
  1995年   3299篇
  1994年   3432篇
  1993年   3125篇
  1992年   3585篇
  1991年   3594篇
  1990年   3521篇
  1989年   3383篇
  1988年   3464篇
  1987年   3399篇
  1986年   3206篇
  1985年   4288篇
  1984年   4574篇
  1983年   3802篇
  1982年   3933篇
  1981年   3855篇
  1980年   3828篇
  1979年   3807篇
  1978年   4136篇
  1977年   4059篇
  1976年   4127篇
  1975年   3796篇
  1974年   3861篇
  1973年   4004篇
  1972年   2822篇
  1971年   2349篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Doklady Mathematics - New properties of convex infinitely differentiable functions related to extremal problems are established. It is shown that, in a neighborhood of the solution, even if the...  相似文献   
2.
JETP Letters - The effect of static mechanical strain on the splitting of spin sublevels of color centers based on spin 3/2 silicon vacancies in silicon carbide at room temperature has been shown....  相似文献   
3.
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...  相似文献   
4.
Doklady Physics - The dependence of Raman spectra of the molecules containing polyene chains on the conjugation length, structure of side and end groups, and isomer type is analyzed theoretically.  相似文献   
5.
JETP Letters - Photonically controlled metastructures containing resonant conducting dipole and chiral elements with CdS and CdSe in gaps have been proposed, implemented, and studied in a waveguide...  相似文献   
6.
7.
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have...  相似文献   
8.
Integrated information theory (IIT) provides a mathematical framework to characterize the cause-effect structure of a physical system and its amount of integrated information (Φ). An accompanying Python software package (“PyPhi”) was recently introduced to implement this framework for the causal analysis of discrete dynamical systems of binary elements. Here, we present an update to PyPhi that extends its applicability to systems constituted of discrete, but multi-valued elements. This allows us to analyze and compare general causal properties of random networks made up of binary, ternary, quaternary, and mixed nodes. Moreover, we apply the developed tools for causal analysis to a simple non-binary regulatory network model (p53-Mdm2) and discuss commonly used binarization methods in light of their capacity to preserve the causal structure of the original system with multi-valued elements.  相似文献   
9.
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials.  相似文献   
10.
Ferrarini  A.  Finotello  A.  Salsano  G.  Auricchio  F.  Palombo  D.  Spinella  G.  Pane  B.  Conti  M. 《Acta Mechanica Sinica》2021,37(7):1192-1192
Acta Mechanica Sinica - A Correction to this paper has been published: https://doi.org/10.1007/s10409-021-01066-2  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