全文获取类型
收费全文 | 6513篇 |
免费 | 735篇 |
国内免费 | 358篇 |
专业分类
化学 | 807篇 |
晶体学 | 7篇 |
力学 | 612篇 |
综合类 | 146篇 |
数学 | 3700篇 |
物理学 | 2334篇 |
出版年
2024年 | 19篇 |
2023年 | 57篇 |
2022年 | 98篇 |
2021年 | 138篇 |
2020年 | 172篇 |
2019年 | 167篇 |
2018年 | 148篇 |
2017年 | 192篇 |
2016年 | 191篇 |
2015年 | 170篇 |
2014年 | 229篇 |
2013年 | 462篇 |
2012年 | 273篇 |
2011年 | 285篇 |
2010年 | 224篇 |
2009年 | 308篇 |
2008年 | 380篇 |
2007年 | 386篇 |
2006年 | 353篇 |
2005年 | 281篇 |
2004年 | 269篇 |
2003年 | 302篇 |
2002年 | 308篇 |
2001年 | 269篇 |
2000年 | 287篇 |
1999年 | 219篇 |
1998年 | 190篇 |
1997年 | 142篇 |
1996年 | 127篇 |
1995年 | 77篇 |
1994年 | 105篇 |
1993年 | 72篇 |
1992年 | 82篇 |
1991年 | 77篇 |
1990年 | 64篇 |
1989年 | 54篇 |
1988年 | 54篇 |
1987年 | 43篇 |
1986年 | 31篇 |
1985年 | 42篇 |
1984年 | 60篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 35篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 20篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有7606条查询结果,搜索用时 15 毫秒
91.
In his celebrated paper, Polya has considered the random walk in the three-dimensional (cubic) lattice and showed that the probability of return to the origin is less than 1. Subsequent authors have shown that the probability is %34.053.... Here we consider the same random walk, with the restriction that the drunkard is only allowed to stay inxyz. It is shown that his probability of returning to the originand staying in the allowed region is %6.4844.... 相似文献
92.
Fabio Martinelli Enzo Olivieri Elisabetta Scoppola 《Journal of statistical physics》1989,55(3-4):477-504
We apply previous results on the pathwise exponential loss of memory of the initial condition for stochastic differential equations with small diffusion to the problem of the asymptotic distribution of the first exit times from an attracted domain. We show under general hypotheses that the suitably rescaled exit time converges in the zero-noise limit to an exponential random variable. Then we extend the results to an infinite-dimensional case obtained by adding a small random perturbation to a nonlinear heat equation. 相似文献
93.
Wansoo T Rhee 《Operations Research Letters》1985,4(3):121-123
Consider independent identically distributed random variables (Xi) valued in [0,1]. Let B(n) be the optimal (minimum) number of unit size bins needed to pack n items of size X1, X2,…,Xn. We prove that there exists a numerical constant C such that for t > 0, The constant C does not depend on the distribution of X. 相似文献
94.
In this review paper, the NBS scale and its limitations are briefly discussed. The magnitude of liquid junction potentials and some calculated values are presented. The use of a molality scale for hydrogen electrode concentration cells at high temperatures is described, and results from measurements on ionization equilibria are summarized. Use of this scale is also recommended for certain circumstances with cells without liquid junction. As an alternative activity scale, use of the Pitzer ion-interaction treatment for ions is recommended for special cases. Finally, reference data are presented for ±HCl in HCl(aq) to 350°C and (HCl+NaCl)(aq) to 200°C that were derived by use of the Pitzer ion-interaction treatment.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991. 相似文献
95.
96.
Summary {\rtf1\ansi\ansicpg1250\deff0\deflang1038\deflangfe1038\deftab708{\fonttbl{\f0\froman\fprq2\fcharset238{\*\fname Times New Roman;}Times New Roman CE;}}
\viewkind4\uc1\pard\f0\fs20 New explanations are given for two types of irregular thermogravimetric (TG) data. A TG relationship between mass and temperature is derived on the basis of migration behavior of bubbles generated in bulk of sample system, and superposed on that derived on the basis of kinetics of the 4\super th\nosupersub order event, which is superposed on the experimental TG data obtained from three reference papers. This suggests that these TG data are reflecting migration of bubbles. A dependence of TG behavior on heating rate, which is contrary to usual that, is shown and is explained in terms of event-rate determination by boiling.
\par } 相似文献
97.
It is proven that the canonical Gibbs measure associated with a gas of vortices of intensity ± converges, in the limitN, 0,Nconst, to a Gaussian measure, which is invariant for the two-dimensional Euler equation.On leave from Dipartimento di Matematica Università di Roma Tor Vergata Roma, Italy.On leave from Dipartimento di Matematica Università di Roma La Sapienza, Roma, Italy. 相似文献
98.
The spherical-model limitn of then-vector model in a random field, with either a statistically independent distribution or with long-range correlated random fields, is studied to demonstrate the correctness of the replica method in which then and replica limits limits are interchanged, provided the replica and thermodynamic limits are taken in the right order, in the case of long-range correlated random fields. A scaling form for the two-point correlation function relevant to the first-order phase transition below the lower critical dimensionality of the random system is also obtained. 相似文献
99.
A comparative quantum-chemical analysis of the electronic structures and spectroscopic parameters of the cycloalkanes C3H6, C4H8, C5H10, and C6H12 and their silicon analogs Si3H6, Si4H8, Si5H10 and Si6H12 was performed in the framework of the SCF MO LCAO method in the INDO approximation. Qualitative interpretation of “abnormal”
ionization potentials and energies of electronic absorption spectra of cyclopolysilanes has been given.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1997. 相似文献
100.
The first part of the paper deals with a critical discussion of the methodical basis of essential work of fracture (EWF) concept with respect to the specimen geometry (especially the notch depth) and application to polymers. In the second part, an in situ testing device, which combines a tensile testing machine with an optical strain-field measuring system, has successfully demonstrated possibility of characterization of fracture behaviour of polystyrene-polybutadiene block copolymers and block copolymer/homopolymer blends as examples of nanostructured polymer materials. It has been shown that knowledge of the time evolution of the strain field close to the crack tips leads to a simple verification of the basic precondition for the applicability of the EWF concept, the precondition “plastic zone coalescence-before-stable crack propagation”. 相似文献