全文获取类型
收费全文 | 78143篇 |
免费 | 18552篇 |
国内免费 | 78篇 |
专业分类
化学 | 73344篇 |
晶体学 | 216篇 |
力学 | 2743篇 |
数学 | 8787篇 |
物理学 | 11683篇 |
出版年
2023年 | 4151篇 |
2022年 | 1512篇 |
2021年 | 2620篇 |
2020年 | 4828篇 |
2019年 | 2488篇 |
2018年 | 2618篇 |
2017年 | 972篇 |
2016年 | 6272篇 |
2015年 | 6081篇 |
2014年 | 5618篇 |
2013年 | 6892篇 |
2012年 | 4549篇 |
2011年 | 2877篇 |
2010年 | 4169篇 |
2009年 | 3914篇 |
2008年 | 2759篇 |
2007年 | 2437篇 |
2006年 | 1705篇 |
2005年 | 1483篇 |
2004年 | 1190篇 |
2003年 | 1001篇 |
2002年 | 930篇 |
2001年 | 792篇 |
2000年 | 695篇 |
1999年 | 491篇 |
1997年 | 490篇 |
1996年 | 589篇 |
1995年 | 602篇 |
1994年 | 565篇 |
1993年 | 752篇 |
1992年 | 559篇 |
1990年 | 442篇 |
1985年 | 570篇 |
1984年 | 566篇 |
1983年 | 531篇 |
1982年 | 566篇 |
1981年 | 594篇 |
1980年 | 597篇 |
1979年 | 538篇 |
1978年 | 590篇 |
1977年 | 682篇 |
1976年 | 681篇 |
1975年 | 766篇 |
1974年 | 757篇 |
1973年 | 595篇 |
1972年 | 485篇 |
1971年 | 482篇 |
1970年 | 692篇 |
1969年 | 549篇 |
1968年 | 605篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
The aim of this Note is to give explicit limit expressions, for diffusion equations involving a small parameter ε, describing both nonperiodic homogenization and reduction of dimension. We consider two kinds of reduction of dimension: the case of plates and the case of thin cylinders. In particular, we give the limit diffusion equation for stratified plates. This is completely explicit and requires no special assumption, except stratification. In the case of thin cylinders, the formulae are less explicit, but we also indicate some simple applications to fibered materials. To cite this article: B. Gustafsson, J. Mossino, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 977–982. 相似文献
142.
Dr. H. Schmieg Prof. Dr. P. Vielsack 《Archive of Applied Mechanics (Ingenieur Archiv)》1987,57(6):446-458
Übersicht Betrachtet wird ein zwangserregtes Zweikörpersystem mit wechselnden Bindungen infolge trockener Reibung. Stationäre Bewegungen werden als Grenzfall instationärer Einschwingvorgänge berechnet. Abhängig von den Systemparametern ergeben sich drei typische Bewegungsformen. Ihnen entsprechen dauernde Haftzustände, wechselnde Haft-Gleitzustände oder dauernde Gleitzustände an der Berührfläche beider Körper.
Intermittant constraints in a two-body-system with dry friction
Summary An externally excited two-body-system with intermittant constraints due to dry friction is considered. Stationary motions are calculated as limit cases of instationary transients. Depending on the parameters of the system, three typical modes are of interest. These correspond to permanent sticking, slipstick behaviour, or to permanent slipping in the contact surface of the bodies, respectively.相似文献
143.
Ludmila C. Fidale Sarah Köhler Martin H.G. Prechtl Thomas Heinze Omar A. El Seoud 《Cellulose (London, England)》2006,13(5):581-592
The concentrations of water, W, and electrolytes present in solutions of LiCl in N,N-dimethylacetamide, LiCl/DMAc, and of tetrabutylammonium fluoride. x-hydrate in DMSO, TBAF.xW/DMSO can be accurately and expediently determined by three independent methods, UV–vis, FTIR and EMF measurement. The first relies on the use of solvatochromic probes whose spectra are sensitive to solution composition. It is applicable to W/LiCl/DMAc solutions but not to TBAF.xW/DMSO, because the charge-transfer complex bands of the probes are suppressed by strong interactions with the latter electrolyte. Integration of νOH band of water may be employed in order to determine [W], hence [electrolyte] by weight difference. EMF measurement uses ion-selective electrodes in order to determine [electrolyte], hence [W] by weight difference. Results of the latter method were in excellent agreement with those of FTIR. The reason for the failure of Karl Fischer titration is addressed, and the relevance of the results obtained to functionalization of cellulose under homogenous solution conditions is briefly commented on. 相似文献
144.
Gábor Dörnyei Marietta Bárczai-Beke Gábor Blaskó Péter Péchy Csaba Szántay 《Tetrahedron letters》1982,23(28):2913-2916
Regioselective demethylation of 3,4-dihydropapaveraldine (a) at 7 and 3' positions affords a properly substituted diphenolic key intermidiate (d) for the synthesis of reticuline and N-norreticuline. 相似文献
145.
We consider Markov processes built from pasting together pieces of strong Markov processes which are killed at a position
dependent rate and connected via a transition kernel. We give necessary and sufficient conditions for local absolute continuity
of probability laws for such processes on a suitable path space and derive an explicit formula for the corresponding likelihood
ratio process. The main tool is the consideration of the process between successive jumps – what we call ‘elementary experiments’
– and criteria for absolute continuity of laws of the process there. We apply our results to systems of branching diffusions
with interactions and immigrations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
146.
For more than 25 yearsJΨ production has helped to sharpen our understanding of QCD. In proton induced reaction some observations are rather well understood
while others are still unclear. The current status of the theory ofJΨ production will be sketched, paying special attention to the issues of formation time andJΨ re-interaction in a nuclear medium. 相似文献
147.
148.
Yun-Zhi Tang Shao-Song Qian Xi-Sen Wang Hong Zhao Xue-Feng Huang Yong-Hua Li Xing-Cai Jiao Ren-Gen Xiong Prof. Dr. 《无机化学与普通化学杂志》2004,630(11):1623-1626
The in situ hydrolysis of phthalyl-γ-glutaminyl-histidine with Cd(ClO4)2·6H2O in the presence of water and methanol affords a novel two-dimensional cadmium coordination polymer, a new phase, anhydrous cadmium(II) phthalate, ( 1 ). The structure was determined by single crystal X-ray diffraction. Crystal data: P21/c, a = 13.8168(14), b = 7.0351(7), c = 8.2054(8) Å, β = 105.540(2)°, V = 768.43(13) Å3, Z = 4, R1 = 0.0380, wR2 = 0.1111. 相似文献
149.
150.