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   37591篇
  免费   5579篇
  国内免费   4268篇
化学   27464篇
晶体学   558篇
力学   1982篇
综合类   260篇
数学   4204篇
物理学   12970篇
  2024年   105篇
  2023年   678篇
  2022年   1345篇
  2021年   1337篇
  2020年   1415篇
  2019年   1446篇
  2018年   1174篇
  2017年   1134篇
  2016年   1720篇
  2015年   1747篇
  2014年   2082篇
  2013年   2692篇
  2012年   3451篇
  2011年   3500篇
  2010年   2414篇
  2009年   2296篇
  2008年   2612篇
  2007年   2299篇
  2006年   2121篇
  2005年   1784篇
  2004年   1360篇
  2003年   1056篇
  2002年   1103篇
  2001年   782篇
  2000年   681篇
  1999年   709篇
  1998年   576篇
  1997年   532篇
  1996年   550篇
  1995年   427篇
  1994年   365篇
  1993年   294篇
  1992年   279篇
  1991年   260篇
  1990年   201篇
  1989年   182篇
  1988年   111篇
  1987年   135篇
  1986年   103篇
  1985年   104篇
  1984年   59篇
  1983年   52篇
  1982年   40篇
  1981年   24篇
  1980年   17篇
  1979年   14篇
  1978年   11篇
  1977年   7篇
  1976年   14篇
  1975年   13篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The coupled model has been developed in this study for moisture transport and beat exchange in soil. The model is driven by atmospheric conditions measured in a field. The concept that soil has a surface resistance to evaporation is introduced in order to relate the evaporation from surface with the vapour flux in air. With the use of this concept, the simulation results agree quite well with the measured data.  相似文献   
102.
Model and empirical study on some collaboration networks   总被引:8,自引:0,他引:8  
In this paper we present an empirical study of a few practical systems described by cooperation networks, and propose a model to understand the results obtained. We study four non-social systems, which are the Bus Route Networks of Beijing and Yangzhou, the Travel Route Network of China, Huai-Yang recipes of Chinese cooked food, and a social system, which is the Collaboration Network of Hollywood Actors. In order to explain the results related to the degree distribution, act-degree distribution and act-size distribution (especially about the degree distribution, which may be better fitted using a stretched exponential distribution (SED)), we suggest a simple model to show a possible evolutionary mechanism for the emergence of such networks. The analytic and numerical results obtained from the model are in good agreement with the empirical results.  相似文献   
103.
A new Co–Fe-based ferromagnetic bulk metallic glass (BMG) was synthesized by copper mould casting method. The thermal stability and crystallization processes were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The soft magnetic behavior was studied by DC magnetic measurements. The high glass formation ability was interpreted in terms of the effective suppression of nucleation and growth of the intermetallic compounds which appear in the multicomponent system during solidification. The high thermal stability indicates that the new Co–Fe-based BMG could be used as high-temperature magnetic material. The low coercivity which was as low as 8 A/m for the as-cast sample was found in the Co–Fe-based metallic glass cylinder with a diameter of 1.5 mm.  相似文献   
104.
We answer a problem of Liao [S.T. Liao, Standard systems of differential equations and obstruction sets—from linearity to perturbations, in: System Researches, Proceedings Dedicated to the 85th Anniversary of Qian Xue-Sen, Zhejiang Education Press, Hangzhou, China, 1996, pp. 279-290 (in Chinese)]: A C1 vector field or a C1 diffeomorphism on an n-dimensional manifold has equal entropy with that of its bundle extensions. We also prove that each ergodic probability with simple Lyapunov spectrum has at most n2n! covering probabilities on each bundle extension.  相似文献   
105.
L-fuzzyRingandL-fuzzyModuleL-fuzzyRingandL-fuzzyModule¥SunRongguangJiangBaoqing(HumanUniversity,Kaifeng,475001)RenXuejun(Minq...  相似文献   
106.
新型稀土电子输运材料Tb(AcA)3·phen   总被引:1,自引:0,他引:1       下载免费PDF全文
Kido等人在文献[1]中报导,在研究有机电致发光(OEL)器件时发现,斓系化合物不能很好地传输载流子.但是,我们在实验中却现Tb(AcA)3phen·不仅是一种很好的OEL发射材料.而且具有很强的电子输运能力.  相似文献   
107.
A review of the advance in the theory of wavelet analysis in recent years is given.  相似文献   
108.
Theformationofanewtypeofself_assembledmultilayerfilms,moleculardeposition(MD)films[1,2],isafastdevelopingareaofthinfilmresearch.Thisnewmethodoffilmpreparationisbasedonionicattractionbetweenoppositechargedchromophores.IncomparisonwiththeclassicLangmuir_Blo…  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