全文获取类型
收费全文 | 382460篇 |
免费 | 2330篇 |
国内免费 | 1181篇 |
专业分类
化学 | 163482篇 |
晶体学 | 5727篇 |
力学 | 22212篇 |
综合类 | 1篇 |
数学 | 74895篇 |
物理学 | 119654篇 |
出版年
2020年 | 1820篇 |
2019年 | 2069篇 |
2018年 | 18863篇 |
2017年 | 19335篇 |
2016年 | 12279篇 |
2015年 | 3862篇 |
2014年 | 4365篇 |
2013年 | 10484篇 |
2012年 | 14262篇 |
2011年 | 28531篇 |
2010年 | 17520篇 |
2009年 | 17899篇 |
2008年 | 23279篇 |
2007年 | 28100篇 |
2006年 | 8622篇 |
2005年 | 14710篇 |
2004年 | 11224篇 |
2003年 | 10894篇 |
2002年 | 8213篇 |
2001年 | 7436篇 |
2000年 | 5899篇 |
1999年 | 4406篇 |
1998年 | 3774篇 |
1997年 | 3615篇 |
1996年 | 3591篇 |
1995年 | 3198篇 |
1994年 | 3097篇 |
1993年 | 3194篇 |
1992年 | 3263篇 |
1991年 | 3454篇 |
1990年 | 3189篇 |
1989年 | 3144篇 |
1988年 | 3203篇 |
1987年 | 3083篇 |
1986年 | 2919篇 |
1985年 | 3936篇 |
1984年 | 4140篇 |
1983年 | 3321篇 |
1982年 | 3530篇 |
1981年 | 3452篇 |
1980年 | 3352篇 |
1979年 | 3469篇 |
1978年 | 3560篇 |
1977年 | 3403篇 |
1976年 | 3520篇 |
1975年 | 3201篇 |
1974年 | 3203篇 |
1973年 | 3296篇 |
1972年 | 2289篇 |
1971年 | 1878篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
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
133.
134.
135.
136.
F. Prez-Willard C. Sürgers H. Von Lhneysen P. Pfundstein 《Physica E: Low-dimensional Systems and Nanostructures》2004,22(4):872-880
The electronic transport through nanostructured bismuth nanobridges has been investigated at low temperatures (T<2 K) and in magnetic fields B up to 8.5 T. The samples show reproducible resistance fluctuations as a function of B, superimposed on a large magnetoresistance of up to 50%. In addition, time-dependent resistance fluctuations in zero magnetic field demonstrate the presence of bistable scatterers in the constriction region of our samples, which are described by two-level systems. Their dynamics are shown to be sensitive to subtle modifications of the static scatterer configuration in their vicinity, which cannot be detected in the sample magnetofingerprint. 相似文献
137.
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
138.
Yu. A. Kumzerov L. S. Parfen’eva I. A. Smirnov H. Misiorek J. Mucha A. Jezowski 《Physics of the Solid State》2003,45(1):57-60
The thermal conductivity of crystalline chrysotile asbestos made up of hollow tubular Mg3Si2O5(OH)4 filaments is measured in the range 5–300 K. The paper discusses the possibility of using this material in studies of the thermal conductivity of thin filaments of metals and semiconductors incorporated into the channels of crystalline chrysotile asbestos tubes. 相似文献
139.
140.
Dominique Fourdrinier William E. Strawderman 《Annals of the Institute of Statistical Mathematics》2003,55(4):803-816
We consider estimation of loss for generalized Bayes or pseudo-Bayes estimators of a multivariate normal mean vector, θ. In
3 and higher dimensions, the MLEX is UMVUE and minimax but is inadmissible. It is dominated by the James-Stein estimator and by many others. Johnstone (1988,
On inadmissibility of some unbiased estimates of loss,Statistical Decision Theory and Related Topics, IV (eds. S. S. Gupta and J. O. Berger), Vol. 1, 361–379, Springer, New York) considered the estimation of loss for the usual
estimatorX and the James-Stein estimator. He found improvements over the Stein unbiased estimator of risk. In this paper, for a generalized
Bayes point estimator of θ, we compare generalized Bayes estimators to unbiased estimators of loss. We find, somewhat surprisingly,
that the unbiased estimator often dominates the corresponding generalized Bayes estimator of loss for priors which give minimax
estimators in the original point estimation problem. In particular, we give a class of priors for which the generalized Bayes
estimator of θ is admissible and minimax but for which the unbiased estimator of loss dominates the generalized Bayes estimator
of loss. We also give a general inadmissibility result for a generalized Bayes estimator of loss.
Research supported by NSF Grant DMS-97-04524. 相似文献