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   19677篇
  免费   717篇
  国内免费   9篇
化学   11958篇
晶体学   61篇
力学   311篇
数学   2601篇
物理学   5472篇
  2023年   120篇
  2021年   145篇
  2020年   196篇
  2019年   154篇
  2018年   189篇
  2017年   182篇
  2016年   479篇
  2015年   412篇
  2014年   429篇
  2013年   783篇
  2012年   781篇
  2011年   972篇
  2010年   461篇
  2009年   400篇
  2008年   880篇
  2007年   838篇
  2006年   847篇
  2005年   749篇
  2004年   596篇
  2003年   555篇
  2002年   566篇
  2001年   477篇
  2000年   387篇
  1999年   344篇
  1998年   284篇
  1997年   302篇
  1996年   309篇
  1995年   276篇
  1994年   275篇
  1993年   298篇
  1992年   306篇
  1991年   254篇
  1990年   217篇
  1989年   234篇
  1988年   212篇
  1987年   220篇
  1986年   218篇
  1985年   252篇
  1984年   303篇
  1983年   223篇
  1982年   263篇
  1981年   299篇
  1980年   253篇
  1979年   261篇
  1978年   242篇
  1977年   229篇
  1976年   201篇
  1975年   208篇
  1974年   177篇
  1973年   180篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The rate constant for dissociative electron attachment to ozone has been derived over the energy range from about 0 to 10 eV using recently measured and also corrected cross section data. The new rate constant data sets for two partial dissociative channels, as well as for the total dissociative electron attachment, are compared with previously reported values, and existing discrepancies are discussed.  相似文献   
102.
103.
Reuther  H.  Arnold  T.  Krawczyk-Bärsch  E. 《Hyperfine Interactions》2004,156(1-4):439-443
Hyperfine Interactions - During batch sorption experiments of heavy metals on chlorite not only sorption reactions take place, but also reactions of chemical weathering leading to mineral...  相似文献   
104.
In aqueous solutions, amphiphilic block copolymers in which a polystyrene (PS) segment is connected to a poly(ethylene oxide) (PEO) block via a bis(2,2′:6′,2″‐ terpyridine ruthenium) complex can form micelles. Such micelles of the protomer type PS20‐[Ru]‐PEO70, according to the preparation procedure representing frozen micelles, were studied by sedimentation velocity and sedimentation equilibrium analysis in an analytical ultracentrifuge and by transmission electron microscopy, with different techniques applied for the sample preparation. The particles obtained were surprisingly multifarious in size. In ultracentrifugation experiments performed at relatively low salt concentrations, the distributions of the sedimentation coefficient s20,w showed a pronounced peak at 9.6 S and a broad, only partly separated second peak around 14 S. The molar mass of the particles at the peak was around 430,000 g/mol, corresponding to an aggregation number of approximately 85. The average hydrodynamic diameter of the particles in the peak fraction was approximately 13 nm. In electron micrographs of negatively stained samples, spheres of diameters between 10 and 25 nm were the most abundant particles, but larger ones with a wide size range were also visible. The latter particles apparently were composed of smaller ones. The data from both sedimentation analysis and electron microscopy showed that (1) the studied compound formed primary micelles of diameters around 20 nm and (2) the primary micelles had a tendency toward aggregation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3159–3168, 2003  相似文献   
105.
Introduction to Hardy Spaces   总被引:1,自引:1,他引:0  
Basic material from the theory of Hardy spaces is presented. The principle of positive energy representations is used as motivation to introduce these spaces.  相似文献   
106.
107.
A calibration technique for the constant-temperature hot-wire anemometer is presented, which is based on traversing the probe through the boundary layer of a flat plate while simultaneously performing fluctuation measurements. The free stream Mach number was M = 2.54, and the Reynolds number Red, based on wire diameter, ranged from 9 to 23. A comparison of the sensitivity values obtained with the aid of such a calibration procedure — under the condition of neglecting low temperature loadings (t<0.6) — agrees well with sensitivities determined with free-stream data-The use of a modified transfer function for correcting the power spectra of flow perturbations revealed a conformity of wide parts of the corrected spectra with the Kolmogorov decay. The fluctuation levels of total temperature and mass flux were computed for the boundary layer of a flat plate. This work was presented at the International Conference on the Methods of Aerophysical Research ICMAR 2007, which was held in Novosibirsk on 5–10 February 2007.  相似文献   
108.
Let R be a local ring and let (x 1, …, x r) be part of a system of parameters of a finitely generated R-module M, where r < dimR M. We will show that if (y 1, …, y r) is part of a reducing system of parameters of M with (y 1, …, y r) M = (x 1, …, x r) M then (x 1, …, x r) is already reducing. Moreover, there is such a part of a reducing system of parameters of M iff for all primes P ε Supp MV R(x 1, …, x r) with dimR R/P = dimR M − r the localization M P of M at P is an r-dimensional Cohen-Macaulay module over R P. Furthermore, we will show that M is a Cohen-Macaulay module iff y d is a non zero divisor on M/(y 1, …, y d−1) M, where (y 1, …, y d) is a reducing system of parameters of M (d:= dimR M).  相似文献   
109.
110.
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