全文获取类型
收费全文 | 529842篇 |
免费 | 3243篇 |
国内免费 | 1253篇 |
专业分类
化学 | 240052篇 |
晶体学 | 7836篇 |
力学 | 30852篇 |
综合类 | 7篇 |
数学 | 91912篇 |
物理学 | 163679篇 |
出版年
2021年 | 4078篇 |
2020年 | 4527篇 |
2019年 | 5374篇 |
2018年 | 17613篇 |
2017年 | 17462篇 |
2016年 | 15987篇 |
2015年 | 5990篇 |
2014年 | 9591篇 |
2013年 | 19456篇 |
2012年 | 19013篇 |
2011年 | 28177篇 |
2010年 | 19587篇 |
2009年 | 20074篇 |
2008年 | 23566篇 |
2007年 | 25530篇 |
2006年 | 16148篇 |
2005年 | 15245篇 |
2004年 | 14819篇 |
2003年 | 14023篇 |
2002年 | 13250篇 |
2001年 | 13019篇 |
2000年 | 10303篇 |
1999年 | 7686篇 |
1998年 | 6872篇 |
1997年 | 6687篇 |
1996年 | 6178篇 |
1995年 | 5605篇 |
1994年 | 5483篇 |
1993年 | 5386篇 |
1992年 | 5708篇 |
1991年 | 6070篇 |
1990年 | 5969篇 |
1989年 | 5765篇 |
1988年 | 5612篇 |
1987年 | 5679篇 |
1986年 | 5243篇 |
1985年 | 6382篇 |
1984年 | 6823篇 |
1983年 | 5727篇 |
1982年 | 6121篇 |
1981年 | 5786篇 |
1980年 | 5453篇 |
1979年 | 5978篇 |
1978年 | 6135篇 |
1977年 | 6213篇 |
1976年 | 6366篇 |
1975年 | 5890篇 |
1974年 | 5725篇 |
1973年 | 6026篇 |
1972年 | 4595篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
Mo2Ni3Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo2Ni3Si primary dendrites and the interdendritic Mo2Ni3Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo2Ni3Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance. 相似文献
192.
V. S. Berezinsky 《Physics of Atomic Nuclei》2003,66(3):423-434
About 400 years have passed since the great discoveries by Galileo, Kepler, and Newton, but astronomy still remains an important source of discoveries in physics. They start with puzzles, with phenomena difficult to explain, and phenomena which in fact need new physics for explanation. Do such puzzles exist now? There are at least three candidates: absence of absorption of TeV gamma radiation in extragalactic space (violation of Lorentz invariance?), absence of GZK cutoff in the spectrum of ultrahigh-energy cosmic rays (new particle physics?), tremendous energy (up to 1054 erg) released in gamma ray bursts on a time scale of a second (collapsing stars or sources of a new type?). Do these puzzles really exist? A critical review of these phenomena is given. 相似文献
193.
194.
195.
Mathematical Notes - 相似文献
196.
197.
198.
199.
In this paper, we obtain a nonlinear Poisson structure and two first integrals in the problem of the plane motion of a circular cylinder and n point vortices in an ideal fluid. This problem is a priori not Hamiltonian; specifically, in the case n= 1 (i.e., in the problem of the interaction of a cylinder with a vortex) it is integrable. 相似文献
200.
Chris Hope 《The Journal of the Operational Research Society》2003,54(11):1167-1176
What strategy should a football (soccer, in American parlance) club adopt when deciding whether to sack its manager? This paper introduces a simple model assuming that a club's objective is to maximize the number of league points that it scores per season. The club's strategy consists of three choices: the length of the honeymoon period during which it will not consider sacking a new manager, the level of the performance trapdoor below which the manager get the sack, and the weight that it will give to more recent games compared to earlier ones. Some data from the last six seasons of the English Premiership are used to calibrate the model. At this early stage of the research, the best strategy appears to have only a short honeymoon period of eight games (much less than the actual shortest period of 12 games), to set the trapdoor at 0.74 points per game, and to put 47% of the weight on the last five games. A club adopting this strategy would obtain on average 56.8 points per season, compared to a Premiership average of 51.8 points. 相似文献