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   25665篇
  免费   4136篇
  国内免费   2399篇
化学   17949篇
晶体学   309篇
力学   1534篇
综合类   109篇
数学   2935篇
物理学   9364篇
  2024年   71篇
  2023年   524篇
  2022年   953篇
  2021年   916篇
  2020年   1013篇
  2019年   998篇
  2018年   829篇
  2017年   732篇
  2016年   1208篇
  2015年   1157篇
  2014年   1350篇
  2013年   1800篇
  2012年   2413篇
  2011年   2419篇
  2010年   1585篇
  2009年   1507篇
  2008年   1644篇
  2007年   1509篇
  2006年   1363篇
  2005年   1157篇
  2004年   839篇
  2003年   642篇
  2002年   608篇
  2001年   443篇
  2000年   436篇
  1999年   521篇
  1998年   429篇
  1997年   436篇
  1996年   457篇
  1995年   358篇
  1994年   306篇
  1993年   238篇
  1992年   234篇
  1991年   198篇
  1990年   171篇
  1989年   143篇
  1988年   98篇
  1987年   109篇
  1986年   88篇
  1985年   83篇
  1984年   48篇
  1983年   43篇
  1982年   35篇
  1981年   19篇
  1980年   11篇
  1979年   10篇
  1978年   6篇
  1976年   9篇
  1975年   11篇
  1957年   4篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
Recent successes in applying tabu search to a wide variety of classical optimization problems have motivated the investigation of applying tabu search to the well-known general fixed charge problem (GFCP). In this paper, an adaptation of tabu search to GFCP is described and computational results are given. In addition, the computational results are compared with those obtained from SWIFT-2, the most well-known and frequently used heuristic method for GFCP. As will be shown, the results are very encouraging.  相似文献   
122.
光照与彩陶俑表面色变关系的实验研究   总被引:1,自引:0,他引:1  
黄玉金  赵葆常 《光子学报》1997,26(2):178-188
本文以秦彩俑表面色彩为研究对象,通过光照实验与色彩变化的色度测量,分析了光照引起彩俑颜料色变的规律,为秦彩俑这一大型重点文物的色彩保护提供了科学理论依据.  相似文献   
123.
High spin states of the odd-odd162Lu nucleus have been studied via147Sm(19F,4nγ)162Lu reaction at 95 MeV beam energy. Level scheme for yrast band based onπ[h11/2 v[i13/2] quasiparticle configuration was established up to I π = (23?) for the first time. This band shows the signature inversion in energy before backbending generally appeared in this mass region. It is stressed that the signature splitting in162Lu is larger than that in the160Tm nucleus.  相似文献   
124.
Na SUN 《数学学报(英文版)》2007,23(10):1909-1914
In this paper, we introduce an operator Hμ(z) on L^∞(△) and obtain some of its properties. Some applications of this operator to the extremal problem of quasiconformal mappings are given. In particular, a sufficient condition for a point r in the universal Teichmfiller space T(△) to be a Strebel point is obtained.  相似文献   
125.
One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented. P. Beller, deceased.  相似文献   
126.
This paper is concerned with a class of nonlinear delay partial difference equations with variable coefficients, which may change sign. By making use of frequency measures, some new oscillatory criteria are established. This is the first time oscillation of these partial difference equations is discussed by employing frequency measures.   相似文献   
127.
Seven new highly oxygenated nortriterpenoids, rubriflorins D–J ( 1 – 7 ), were isolated from the leaves and stems of Schisandra rubriflora, and their structures were elucidated on the basis of extensive analysis of spectroscopic data. These new compounds feature the opening of ring A compared with related known nortriterpenoids isolated from the genus Schisandra and showed weak activity against HIV‐1.  相似文献   
128.
A laser micro-chopper has been designed to respond fast to a molecular beam. A method of spectral structure measurement is established to analyse the responding signals. In experiments, the minimum detectable signals correspond to an air molecular-beam intensity of 5 × 108/s  相似文献   
129.
It is shown that for a large collection of independent martingales, the martingale property is preserved on the empirical processes. Under the assumptions of independence and identical finite-dimensional distributions, it is proved that a large collection of stochastic processes are martingales essentially if and only if the empirical processes are also martingales. These two results have implications on the testability of the martingale property in scientific modeling. Extensions to submartingales and supermartingales are given.

  相似文献   

130.
电子被HF和HCl分子散射总截面的计算   总被引:1,自引:1,他引:0  
利用光学势方法计算了能量在10eV—1000eV范围内电子被H、F和Cl原子散射的总截面,并与已有的实验结果和理论计算进行了比较;又利用可加性规则(additivityrule)计算得到了电子被HF和HCl分子散射的总截面,计算结果也与已有的实验结果和理论计算进行了比较  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