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   39286篇
  免费   1356篇
  国内免费   20篇
化学   22120篇
晶体学   180篇
力学   860篇
综合类   1篇
数学   6555篇
物理学   10946篇
  2023年   218篇
  2021年   327篇
  2020年   518篇
  2019年   363篇
  2018年   473篇
  2017年   449篇
  2016年   1037篇
  2015年   872篇
  2014年   987篇
  2013年   2113篇
  2012年   1707篇
  2011年   2039篇
  2010年   1048篇
  2009年   883篇
  2008年   1930篇
  2007年   1870篇
  2006年   1658篇
  2005年   1498篇
  2004年   1195篇
  2003年   1006篇
  2002年   938篇
  2001年   767篇
  2000年   685篇
  1999年   469篇
  1998年   422篇
  1997年   418篇
  1996年   529篇
  1995年   476篇
  1994年   488篇
  1993年   568篇
  1992年   474篇
  1991年   361篇
  1990年   393篇
  1989年   324篇
  1988年   341篇
  1987年   334篇
  1986年   313篇
  1985年   499篇
  1984年   477篇
  1983年   437篇
  1982年   446篇
  1981年   451篇
  1980年   434篇
  1979年   378篇
  1978年   419篇
  1977年   400篇
  1976年   347篇
  1975年   330篇
  1974年   321篇
  1973年   320篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
Ohne ZusammenfassungDie vorliegende Untersuchung wurde im Laboratorium für allgemeine Experimentalchemie und in jenem für analytische Chemie an der technischen Hochschule in Wien durchgeführt. Es ist uns eine angenehme Pflicht, den Vorständen dieser Institute, den Herren Professoren Dr. M. Bamberger und Dr. G. Vortmann für ihr stetes Entgegenkommen unseren wärmsten Dank zu sagen.  相似文献   
143.
144.
Poly(D ,L ‐lactide) and poly(D ,L ‐lactide‐co‐glycolide) with various composition and with one methacrylate and one carboxylate end group were synthesized and grafted onto poly(vinyl alcohol) (PVA) via the carboxylate group. The graft copolymers were crosslinked via the methacrylate groups using a free radical initiator. The polymer networks were characterized by means of NMR and studied qualitatively by means of IR spectroscopy. The influence of the glycolide content in the polyester grafts and of the number of ester units in the grafts on thermal properties and swellability were studied as well. The high swellability in water is characteristic of all hydrogels. Differential scanning calorimetry (DSC) showed a single glass transition temperature that occurs in the range between 51 and 69 °C. Thermogravimetric analysis (TGA) of the networks showed the main loss in weight in the temperature range between 290 and 370 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4536–4544, 2007  相似文献   
145.
146.
147.
The production cross sections of L-shell X-ray of some rare earth elements have been measured by collision of 12C4+ and 16O4+ ions of 0.5 to 0.75 MeV/amu. The results were compared with experimental data of other authors and with theoretical predictions gained by the ECPSSR and ECPSSR plus multiple ionization (ECPSSR+MI) models. For atomic parameters (fluorescence yields and probabilities for Coster-Kronig transitions) the role of several databases were studied. The ECPSSR theory underestimates cross sections when compared with experimental results obtained in the present work, but ECPSSR+MI has a better agreement with the experimental data. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
148.
A central problem that arises in evolutionary biology is that of displaying partitions of subsets of a finite set X on a tree whose vertices are partially labelled with the elements of X. Such a tree is called an X-tree and, for a collection of partitions of subsets of X, characterisations for the existence and uniqueness of an X-tree that displays have been previously given in terms of chordal graphs. In this paper, we obtain two closely related characterisations also in terms of chordal graphs. The first describes when identifies an X-tree, and the second describes when a compatible subset of is of maximum size.  相似文献   
149.
The final state of Au+Au collisions at √s=130 AGeV at RHIC has been reconstructed within the framework of the Buda-Lund hydrodynamical model, by performing a simultaneous fit to final data on twoparticle Bose-Einstein correlations of the STAR and PHENIX Collaboration, and final identified single-particle spectra as measured by the PHENIX Collaboration. The results indicate a strongly three dimensional expansion, with a four-velocity field that is almost a spherically symmetric Hubble flow. We find large transverse geometrical source sizes, R G=9.8±1.2 fm, relatively short mean freeze-out time, τ0=6.1±0.3 fm/c and a short duration of particle emission, Δτ=0.02±1.5 fm/c. Most strikingsly, we find an indication for a hot central part of the hydrodynamically evolving core, characterized by a central temperature T 0=202±13 MeV that is close to (or even above) the deconfinement temperature of the quark-hadron phase transition. The best fit indicates a cold surface temperature T s=110±16 MeV. When the possibility of the hot center is excluded, the confidence level of the fit decreases from 28.9% to 1.0%. Predictions are made for the rapidity dependence of the slope parameters and for the transverse mass depedence of the rapidity width of the single-particle spectra, and the transverse mass dependence of the non-identical particle correlations.  相似文献   
150.
We establish new estimates for the Laplacian, the div–curl system, and more general Hodge systems in arbitrary dimension, with an application to minimizers of the Ginzburg–Landau energy. To cite this article: J. Bourgain, H. Brezis, C. R. Acad. Sci. Paris, Ser. I 338 (2004).  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