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   378457篇
  免费   4469篇
  国内免费   2250篇
化学   205642篇
晶体学   5896篇
力学   16703篇
综合类   117篇
数学   41593篇
物理学   115225篇
  2019年   3160篇
  2018年   3943篇
  2017年   3867篇
  2016年   5958篇
  2015年   3885篇
  2014年   5861篇
  2013年   15378篇
  2012年   11662篇
  2011年   14249篇
  2010年   9850篇
  2009年   9483篇
  2008年   13069篇
  2007年   13224篇
  2006年   12597篇
  2005年   11629篇
  2004年   10535篇
  2003年   9535篇
  2002年   9369篇
  2001年   10287篇
  2000年   7939篇
  1999年   6259篇
  1998年   5537篇
  1997年   5498篇
  1996年   5188篇
  1995年   4874篇
  1994年   4837篇
  1993年   4528篇
  1992年   5159篇
  1991年   5143篇
  1990年   4992篇
  1989年   4852篇
  1988年   4935篇
  1987年   4850篇
  1986年   4580篇
  1985年   6120篇
  1984年   6487篇
  1983年   5414篇
  1982年   5792篇
  1981年   5564篇
  1980年   5582篇
  1979年   5567篇
  1978年   5970篇
  1977年   5814篇
  1976年   5930篇
  1975年   5532篇
  1974年   5444篇
  1973年   5824篇
  1972年   3961篇
  1971年   3222篇
  1967年   3111篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Investigations to the causes and effects of contaminants at the rf diode deposition of CrSi films in a non-heated high vacuum apparatus were carried out comparing an oxygen-free fusion target with an oxygen-containing cermet target. The films of the fusion target contained considerable amounts of oxygen; analogously the oxygen concentration in the films was increased in the case of the cermet target. Moreover, hydrogen was found. The concentration of the contaminants decreased with the sputtering power, however the rate of incorporation increased. For high sputtering rates the contamination process was reproducible and independent of the plant conditioning; the deposited films were depth-homogeneous. The reasons for this behaviour lie in water sources which are activated first of all by the discharge itself. The electrical properties found are explained by the contaminants and the deposition conditions.  相似文献   
122.
Summary We report on novel optical techniques, based on evanescent waves, for the characterization of polymer surfaces and thin films. We first describe photo-ablation studies with polysilane films investigated by surface plasmon microscopy, a technique which is particularly well-suited for ultrathin samples. Thicker films that are homogeneous enough to carry optical waveguide modes can be characterized with high lateral resolution by the recently developed waveguide microscopy. We demonstrate this for a thin film of a solid polyelectrolyte. Finally, we report on surface plasmon field-enhanced Raman-spectroscopic and -imaging investigations of ultrathin Langmuir-Blodgett-Kuhn-layers of cadmium arachidate.W. Hickel is now with HOECHST AG, Angewandte Physik, W-6230 Frankfurt 80  相似文献   
123.
124.
The equations describing the behaviour of temperature/flow microsensorsemploy-ing polysilicon thermistors form a degenerate nonlinearparabolic system. One special feature is that different equationsof this system are to be satisfied on different domains. Bymeans of supersolutions and subsolutions, the maximum principle,and fixed point arguments, the authors show the existence ofsolutions to the equations.  相似文献   
125.
In 1980 Chern and Terng defined a Bäcklund transformation for affine minimal surfaces. In this paper we show that this Bäcklund transformation can be simply represented by an involution and translation of the affine conormal.  相似文献   
126.
127.
This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out.  相似文献   
128.
129.
Moscow Institute of Electronic Engineering. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 89, No. 1, pp. 132–150, October, 1991.  相似文献   
130.
A new microscopic model of anomalous muonium for the elemental semiconductors is proposed. The relevant configuration consisting of both a diamagrentic molecule Si−Mu and an unpaired orbital e is contained into a semivacancy of the real lattice. By using the unrestricted Hartree-Fock computational method the principal properties of the system are established. A dynamical version of the model together with a question on the formation of such system are discussed.  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