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   291321篇
  免费   2113篇
  国内免费   1003篇
化学   141503篇
晶体学   4019篇
力学   14957篇
综合类   6篇
数学   54546篇
物理学   79406篇
  2020年   1980篇
  2019年   2271篇
  2018年   13390篇
  2017年   13163篇
  2016年   10207篇
  2015年   3203篇
  2014年   4104篇
  2013年   9565篇
  2012年   10566篇
  2011年   18666篇
  2010年   11553篇
  2009年   11802篇
  2008年   14544篇
  2007年   16735篇
  2006年   7860篇
  2005年   8219篇
  2004年   7663篇
  2003年   7568篇
  2002年   6491篇
  2001年   6174篇
  2000年   4951篇
  1999年   3600篇
  1998年   3185篇
  1997年   3171篇
  1996年   3009篇
  1995年   2432篇
  1994年   2500篇
  1993年   2545篇
  1992年   2649篇
  1991年   2722篇
  1990年   2612篇
  1989年   2592篇
  1988年   2520篇
  1987年   2495篇
  1986年   2414篇
  1985年   3086篇
  1984年   3239篇
  1983年   2595篇
  1982年   2867篇
  1981年   2743篇
  1980年   2548篇
  1979年   2761篇
  1978年   2867篇
  1977年   2875篇
  1976年   2848篇
  1975年   2703篇
  1974年   2676篇
  1973年   2836篇
  1972年   1893篇
  1967年   1840篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
This work deals with the formation of inclusion complexes between cinnamaldehyde and two synthetic alkylcarbonates of γ-cyclodextrin, namely ethylcarbonate-γ-CD and octylcarbonate-γ-CD. Complexation was monitored by phase-solubility studies, by FT-IR spectroscopy and by DSC and TG analysis. The diffusion of cinnamaldehyde through a cellulose membrane was investigated in the absence and in the presence of each of the two γ-CD alkylcarbonates. Studies on photostability and stability over time were carried out on different cosmetic formulations containing pure cinnamaldehyde or an equivalent amount of cinnamaldehyde complexed with the two alkylcarbonates. Phase-solubility diagrams, DSC, FTIR and TGA analysis suggested the formation of inclusion complexes. The diffusion of cinnamaldehyde through the cellulose membrane decreased in the presence of the two alkylcarbonates confirming the interaction of this molecule with the inclusion agents. Moreover the stability of cinnamaldehyde to light and heat resulted increased by complexing this fragrance material with the two alkylcarbonates.  相似文献   
942.
943.
We analyze the dynamics of a simple but nontrivial classical Hamiltonian system of infinitely many coupled rotators. We assume that this infinite system is driven out of thermal equilibrium either because energy is injected by an external force (Case I), or because heat flows between two thermostats at different temperatures (Case II). We discuss several possible definitions of the entropy production associated with a finite or infinite region, or with a partition of the system into a finite number of pieces. We show that these definitions satisfy the expected bounds in terms of thermostat temperatures and energy flow.  相似文献   
944.
 Let M be a 2m-dimensional compact Riemannian manifold with Anosov geodesic flow. We prove that every closed bounded k form, k≥2, on the universal covering of M is d(bounded). Further, if M is homotopy equivalent to a compact K?hler manifold, then its Euler number χ(M) satisfies (−1) m χ(M)>0. Received: 25 September 2001 / Published Online: 16 October 2002  相似文献   
945.
946.
Anindya Datta 《Pramana》2003,60(2):363-368
We propose a novel method for the search of supersymmetry, especially for the electroweak gauginos at the large hadron collider (LHC). Gauge boson fusion technique was shown to be useful for heavy and intermediate mass Higgs bosons. In this article, we have shown that this method can also be applied to find the signals of EW gauginos in supersymmetric theories where the canonical search strategies for these particles fail.  相似文献   
947.
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets.  相似文献   
948.
949.
950.
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