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   105398篇
  免费   6749篇
  国内免费   5890篇
化学   61658篇
晶体学   1425篇
力学   5968篇
综合类   443篇
数学   12613篇
物理学   35930篇
  2023年   846篇
  2022年   1868篇
  2021年   2268篇
  2020年   2577篇
  2019年   2755篇
  2018年   3142篇
  2017年   3034篇
  2016年   3794篇
  2015年   2747篇
  2014年   3930篇
  2013年   5399篇
  2012年   5605篇
  2011年   5919篇
  2010年   4755篇
  2009年   4728篇
  2008年   4947篇
  2007年   4588篇
  2006年   4212篇
  2005年   3743篇
  2004年   3385篇
  2003年   2999篇
  2002年   3167篇
  2001年   2823篇
  2000年   2218篇
  1999年   1759篇
  1998年   1630篇
  1997年   1395篇
  1996年   1367篇
  1995年   1142篇
  1994年   1189篇
  1993年   1133篇
  1992年   1092篇
  1991年   1151篇
  1990年   1141篇
  1989年   1049篇
  1988年   932篇
  1987年   925篇
  1986年   888篇
  1985年   925篇
  1984年   917篇
  1983年   823篇
  1982年   800篇
  1979年   802篇
  1978年   812篇
  1977年   806篇
  1976年   919篇
  1975年   812篇
  1974年   844篇
  1973年   847篇
  1972年   752篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
The invariant differential cross section, the tensor analyzing power A yy , and the vector analyzing power A y for the reaction 9Be(d, p)X are measured at an initial deuteron momentum of 4.5 GeV/c and a proton detection angle of about 80 mrad. The data obtained for the differential cross section are consistent with the results of measurements at 3.5 and 5.78 GeV/c and a proton emission angle of 2.5°. The values found for the tensor analyzing power A yy are compared with similar data obtained previously for the deuteron-fragmentation process occurring on a carbon target at various values of the initial deuteron momentum and leading to proton emission at zero angle. The data on the differential cross section for the reaction 9Be(d, p)X can be satisfactorily described within the relativistic impulse approximation by using standard deuteron wave functions; however, the approach based on this conceptual framework proves to be inadequate in dealing with data on the tensor analyzing power. These results indicate that it is necessary either to change the method for describing the relativistic deuteron or to take into account additional mechanisms.  相似文献   
143.
Some possible errors in determining the gravity anomalies are discussed. Such errors may be caused by an inaccurate calibration of the gravimeter used in an airborne survey system. An approach based on wavelet decompositions is proposed for its additional calibration with the use of flight data obtained during repeated flights.  相似文献   
144.
The aim of this study is to construct a quantitative characteristic for the degree of gaze stabilization on a visual target with consideration of physiological constraints. A quality criterion for visual tracking during optokinetic vestibulocervical nystagmus is proposed. The index of imaginary tracking during rotation in the dark allows one to speak of a difference in the image stabilization quality between a healthy person and a patient. Experimental nystagmus data are used to calculate the quality index of visual tracking and the index of imaginary tracking.  相似文献   
145.
The chlorination of benzene, toluene, and o-xylene with molecular chlorine in the presence of the phthalocyanine complexes of different structures was studied. The transformations of the catalysts during the reaction were investigated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1644–1647, August, 2008.  相似文献   
146.
147.
Oximes of 4-(4-pyrazolyl)-3-buten-2-onees obtained by successive reaction of 3-aryl-4-formylpyrazoles with acetone and hydroxylamine at the treatment with iodine suffered an oxidative cyclization yielding 3-aryl-4-(5-isoxazolyl)pyrazoles.  相似文献   
148.
The melting mechanism of polymer crystals is proposed. It is assumed that the melting happens due to forming supervacancies. This mechanism leads the appearance of anisotropic phase of a melt. It is shown that two phases—anisotropic and isotropic—can exist in polymer melts.  相似文献   
149.
150.
Conclusion A method was proposed which makes it possible to study the low-frequency internal friction of complex fibers. This method was used to study the internal friction of complex composite fibers based on PCA and PE. We observed a relaxation process which is typical of the composite and is absent in the pure materials.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 11–15, January–February, 1989.  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