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   474588篇
  免费   2755篇
  国内免费   743篇
化学   213632篇
晶体学   7048篇
力学   28632篇
综合类   13篇
数学   75899篇
物理学   152862篇
  2021年   4071篇
  2020年   4411篇
  2019年   5341篇
  2018年   12585篇
  2017年   12894篇
  2016年   12638篇
  2015年   5198篇
  2014年   9154篇
  2013年   17473篇
  2012年   16787篇
  2011年   24026篇
  2010年   17537篇
  2009年   18008篇
  2008年   22189篇
  2007年   24268篇
  2006年   14082篇
  2005年   15258篇
  2004年   13262篇
  2003年   12825篇
  2002年   11876篇
  2001年   11261篇
  2000年   8919篇
  1999年   6558篇
  1998年   5967篇
  1997年   5865篇
  1996年   5524篇
  1995年   4792篇
  1994年   4933篇
  1993年   4902篇
  1992年   5099篇
  1991年   5531篇
  1990年   5400篇
  1989年   5418篇
  1988年   5192篇
  1987年   5194篇
  1986年   4866篇
  1985年   5892篇
  1984年   6181篇
  1983年   5227篇
  1982年   5423篇
  1981年   5097篇
  1980年   4714篇
  1979年   5443篇
  1978年   5475篇
  1977年   5655篇
  1976年   5734篇
  1975年   5381篇
  1974年   5211篇
  1973年   5457篇
  1972年   4416篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
84.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
85.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
86.
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual polytope.  相似文献   
87.
88.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature.  相似文献   
89.
The lidar equation for the vibrational backscattering of neodymium laser radiation and its harmonics by hydrogen molecules is solved numerically. Inclined paths in the atmosphere are investigated with the aim of selecting the transmitter wavelength for detecting the lowest concentrations of hydrogen. Zh. Tekh. Fiz. 68, 20–22 (January 1998)  相似文献   
90.
Ordinary cohomologies in an algebra most often exhibit themselves either as objects that describe extensions (of algebras, groups, or modules) or as subjects hindering the existence of algebraic constructions. We introduce the notion of nonlinear cohomologies at a level of cochain complexes, furnish particular examples for Lie algebras, and give an interpretation of first nonlinear cohomologies in terms of “quasiextensions” of orthogonal modules. Translated fromAlgebra i Logika, Vol. 37, No. 5, pp. 522–541, September–October, 1998.  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