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   203854篇
  免费   1962篇
  国内免费   591篇
化学   102305篇
晶体学   3340篇
力学   9287篇
综合类   5篇
数学   22470篇
物理学   69000篇
  2021年   1655篇
  2020年   1797篇
  2019年   1998篇
  2018年   2699篇
  2017年   2601篇
  2016年   3765篇
  2015年   2304篇
  2014年   3613篇
  2013年   9084篇
  2012年   7239篇
  2011年   8733篇
  2010年   6040篇
  2009年   5908篇
  2008年   7911篇
  2007年   8079篇
  2006年   7722篇
  2005年   6890篇
  2004年   6424篇
  2003年   5651篇
  2002年   5491篇
  2001年   6424篇
  2000年   4931篇
  1999年   3794篇
  1998年   3038篇
  1997年   3045篇
  1996年   2791篇
  1995年   2613篇
  1994年   2462篇
  1993年   2337篇
  1992年   2691篇
  1991年   2671篇
  1990年   2600篇
  1989年   2396篇
  1988年   2449篇
  1987年   2448篇
  1986年   2279篇
  1985年   2960篇
  1984年   3215篇
  1983年   2631篇
  1982年   2801篇
  1981年   2771篇
  1980年   2637篇
  1979年   2727篇
  1978年   2821篇
  1977年   2819篇
  1976年   2886篇
  1975年   2670篇
  1974年   2644篇
  1973年   2776篇
  1972年   1763篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
V Kumar  B N Roy  D K Rai 《Pramana》1992,38(1):77-90
We have calculated total and differential cross-sections for 1sns (n = 2, 3, 4) electron impact excitation of hydrogen and hydrogenic ions at various energies in Coulomb-projected Born approximation. Distortion due to static interactions, target polarization and exchange effects has been incorporated in the initial channel. The present calculations have been compared with other theoretical and experimental results.  相似文献   
994.
Plasmatic accumulation of uraemic toxins in the middle molecular mass range has been reported to be associated with several pathologies observed in uraemic patients. The very low concentration of these toxins in uraemic body fluids makes classical chromatography techniques inadequate in isolating sufficient amounts of these endogenous substances, thus precluding their identification. A scaling up of gel permeation and ion-exchange chromatographies was therefore developed. This considerably increased the amount of uraemic toxins isolated, thus allowing the study of their chemical nature and facilitating understanding of their biological activities.  相似文献   
995.
Ferric ferrocyanides synthesized from different sources of ferric cations and ferrocyanide anions and those derived from ferrous ferricyanide, ferrous ferrocyanide and ferric ferricyanide have been studied using Mössbauer and XRD techniques. Structural information of the effect of the provenance on the properties of the final compound is obtained. Significant correlations between isomer shift and quadrupole splitting of inner and outer iron cations have been observed.  相似文献   
996.
Total charge-changing cross sections have been measured for8Li on C and Pb targets, for9Li on C, Al, Cu, Sn and Pb targets, as well as for11Li on C, Sn and Pb targets at about 80 MeV/nucleon. These data are compared to measured total reaction cross sections and Glauber-type calculations using Hartree-Fock density distributions. These comparisons allow to draw conclusions on the proton density distribution of the neutronrich lithium isotopes. The results show that even for the most exotic nucleus11Li the proton distribution is only very weakly influenced by the long tail in the neutron density distribution already established in several experiments.  相似文献   
997.
With a suitable combination of ligand-stabilised nanoparticle suspension and ionic salt solutions, it is possible to produce microcrystals that are coated with nanoparticles. The self-assembly process of coating microcrystals by gold nanoparticles (NP) is mediated by the crystal lattice. This is the so-called CLAMS process - a generic process for self-organisation of nanoparticles on the surface of crystals [M. Murugeshan, D. Cunningham, J.-L. Martnez-Albertos, R. Vrcelj, B.D. Moore, Chem. Commun. (2005) 2677]. We are exploring here the structural properties of these self-assembled structures by using different imaging techniques.  相似文献   
998.
Summary Four different bottled water brands sold in Greece in the winter of 2001-2002 were analyzed for a wide range of chemical elements, using neutron activation analysis (NAA). The elements Na and Br were determined instrumentally (INAA), whereas the other metals and trace elements radiochemically (RNAA). The results indicated that the mean level of all the elements determined in the samples were well within the European Union (EU) directive on drinking water and accomplish the drinking water standards of the World Health Organisation (WHO) as well as of the Food and Drug Administration (FDA).  相似文献   
999.
1000.
We study the rate of rational approximation and asymptotic monogeneity of functions at points of the finite porosity of a compact set.Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 9, Suzdal Conference-3, 2003.  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