全文获取类型
收费全文 | 299207篇 |
免费 | 1814篇 |
国内免费 | 642篇 |
专业分类
化学 | 134948篇 |
晶体学 | 4673篇 |
力学 | 16003篇 |
综合类 | 5篇 |
数学 | 46081篇 |
物理学 | 99953篇 |
出版年
2021年 | 1724篇 |
2020年 | 1872篇 |
2019年 | 2076篇 |
2018年 | 10997篇 |
2017年 | 11762篇 |
2016年 | 7707篇 |
2015年 | 3210篇 |
2014年 | 3861篇 |
2013年 | 9410篇 |
2012年 | 11513篇 |
2011年 | 20662篇 |
2010年 | 13037篇 |
2009年 | 12987篇 |
2008年 | 18129篇 |
2007年 | 21642篇 |
2006年 | 7955篇 |
2005年 | 13471篇 |
2004年 | 9692篇 |
2003年 | 8942篇 |
2002年 | 6876篇 |
2001年 | 6580篇 |
2000年 | 5230篇 |
1999年 | 3835篇 |
1998年 | 3085篇 |
1997年 | 3069篇 |
1996年 | 2962篇 |
1995年 | 2713篇 |
1994年 | 2555篇 |
1993年 | 2417篇 |
1992年 | 2765篇 |
1991年 | 2739篇 |
1990年 | 2668篇 |
1989年 | 2476篇 |
1988年 | 2536篇 |
1987年 | 2532篇 |
1986年 | 2358篇 |
1985年 | 3055篇 |
1984年 | 3320篇 |
1983年 | 2718篇 |
1982年 | 2885篇 |
1981年 | 2863篇 |
1980年 | 2716篇 |
1979年 | 2819篇 |
1978年 | 2925篇 |
1977年 | 2847篇 |
1976年 | 2950篇 |
1975年 | 2717篇 |
1974年 | 2688篇 |
1973年 | 2852篇 |
1972年 | 1794篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
102.
103.
104.
The finite-difference method is a numerical technique for obtaining approximate solutions to differential equations. The main
objective of the present study is to give a new aspect to the finite-difference method by using a variational derivative.
By applying this formulation, accurate values of the buckling loads of beams and frames with various end supports are obtained.
The performance of this formulation is verified by comparison with numerical examples in the literature
__________
Published in Prikladnaya Mekhanika, Vol. 41, No. 7, pp. 139–144, July 2005. 相似文献
105.
L. B. Beinenson 《Journal of Mathematical Sciences》2005,129(2):3730-3756
For an arbitrary poset H and measure ρ on H × R (where R is the real axis), we construct a monotone decreasing stochastic field ηρ and compute its finite-dimensional distributions. In the case where H is a Λ-semilattice and the measure ρ satisfies additional conditions, we compute various characteristics of the field ηρ such as the expectation of the field value at a point, variance of the field value at a point, and correlation function of the field. The described construction of random fields gives a new method for constructing positive definite functions on posets. Bibliography: 6 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 301, 2003, pp. 92–143. 相似文献
106.
Unsteady motion in single-line flow-injection systems consisting of n tubular elements with valve or hydrodynamic injection is studied theoretically. A formula for the duration of the initial period of unsteady flow is derived. This initial period is much shorter than the mean residence time of the analyte in practical systems. It can therefore be neglected in mathematical modelling of such systems. Experimental data obtained with single-line systems with valve and hydrodynamic injection confirmed the validity of the theoretical equations. 相似文献
107.
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
108.
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
109.
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
110.
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