全文获取类型
收费全文 | 23249篇 |
免费 | 3137篇 |
国内免费 | 2847篇 |
专业分类
化学 | 19759篇 |
晶体学 | 657篇 |
力学 | 1468篇 |
综合类 | 267篇 |
数学 | 2180篇 |
物理学 | 4902篇 |
出版年
2024年 | 68篇 |
2023年 | 330篇 |
2022年 | 707篇 |
2021年 | 897篇 |
2020年 | 1188篇 |
2019年 | 942篇 |
2018年 | 876篇 |
2017年 | 852篇 |
2016年 | 1202篇 |
2015年 | 1132篇 |
2014年 | 1233篇 |
2013年 | 2333篇 |
2012年 | 1362篇 |
2011年 | 1299篇 |
2010年 | 1137篇 |
2009年 | 1254篇 |
2008年 | 1256篇 |
2007年 | 1421篇 |
2006年 | 1289篇 |
2005年 | 1148篇 |
2004年 | 1090篇 |
2003年 | 873篇 |
2002年 | 746篇 |
2001年 | 564篇 |
2000年 | 527篇 |
1999年 | 468篇 |
1998年 | 437篇 |
1997年 | 383篇 |
1996年 | 352篇 |
1995年 | 312篇 |
1994年 | 198篇 |
1993年 | 202篇 |
1992年 | 196篇 |
1991年 | 114篇 |
1990年 | 102篇 |
1989年 | 83篇 |
1988年 | 66篇 |
1987年 | 69篇 |
1986年 | 60篇 |
1985年 | 78篇 |
1984年 | 64篇 |
1983年 | 32篇 |
1982年 | 52篇 |
1981年 | 46篇 |
1980年 | 36篇 |
1979年 | 34篇 |
1978年 | 23篇 |
1977年 | 24篇 |
1976年 | 18篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 812 毫秒
41.
42.
A Dirac picture perturbation theory is developed for the time evolution operator in classical dynamics in the spirit of the Schwinger–Feynman–Dyson perturbation expansion and detailed rules are derived for computations. Complexification formalisms are given for the time evolution operator suitable for phase space analyses, and then extended to a two-dimensional setting for a study of the geometrical Berry phase as an example. Finally a direct integration of Hamilton's equations is shown to lead naturally to a path integral expression, as a resolution of the identity, as applied to arbitrary functions of generalized coordinates and momenta. 相似文献
43.
通过改变带细玻璃管的烧瓶中水的温度导致水位变化来粗略演示水的收缩情况.为较准确测定水最大密度时的温度,将2个温度计放在水下较浅处和较深处,分别测量当温度经由4℃升高时和由4℃降低时两温度计的示数,进而验证水的反常热膨胀特性. 相似文献
44.
R. S. Martynov Yu. M. Nechepurenko 《Computational Mathematics and Mathematical Physics》2006,46(7):1155-1167
For a discrete linear stochastic dynamical system, computation of the response matrix to the external action from a subspace using given observational data is examined. An algorithm is proposed and substantiated that makes it possible to improve the numerical accuracy and to reduce the amount of observational data compared to the general case where an arbitrary external action is allowed. As an illustration, a discrete system arising in the analysis of a linear stochastic dynamical continuous-time system is considered more thoroughly. Some numerical results are presented. 相似文献
45.
46.
47.
Bajdik J. Pintye-Hódi K. Novák Cs. Kelemen A. Regdon G. Erős I. 《Journal of Thermal Analysis and Calorimetry》2002,68(2):613-627
The extents of the protective effects of coating films on the surface of crystals were determined. Three different samples
were made with different quantities of coating fluid (Sepifilm LP 010 in 10% aqueous solution). Since the atomizing rate was
constant, the coating time increased in parallel with the volume of coating fluid applied. The direct measurement of film
thickness and smoothness is very difficult, and therefore indirect methods were used. Dimenhydrinate was chosen as model drug;
this is a heat-sensitive antihistamine with a low melting point. This temperature can be reached during the tableting process.
The behaviour of samples on exposure to heat was examined by differential scanning calorimetry. The water uptakes of the samples
were determined with an Enslin apparatus. Plasticity was studied with an instrumented tablet machine. These indirect methods
(thermal conductivity, water uptake and plasticity measurements) revealed connections between the results of the various experiments.
An overlong coating time decreased the protective effect of the coating film.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
48.
49.
The effect of the amount of desorbed water on the mechanical properties of composites based on low-density polyethylene and linen yarn production waste (LW) is analyzed by statistical methods. It is shown that the amount of absorbed water decreases during the desorption process at room temperature both for specimens modified and unmodified with diphenylmethane diisocyanate (DIC.) The most sensitive to the action of water is the elastic modulus, which decreases considerably under the effect of water and is fully restored in the desorption process. The tensile strain also increases with the amount of absorbed water. It is found that the elastic modulus of the unmodified composite correlates linearly with the amount of desorbed water. Between the amount of desorbed water and the tensile strain, as well the specific work of deformation, a negative linear correlation is revealed. After water desorption, all strength and deformation characteristics of both the modified and unmodified composites are fully recovered.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 515–524, July–August, 2005. 相似文献
50.
By further generalizing the skew-symmetric triangular splitting iteration method studied by Krukier, Chikina and Belokon (Applied Numerical Mathematics, 41 (2002), pp. 89–105), in this paper, we present a new iteration scheme, called the modified skew-Hermitian triangular splitting iteration method, for solving the strongly non-Hermitian systems of linear equations with positive definite coefficient matrices. We discuss the convergence property and the optimal parameters of this new method in depth. Moreover, when it is applied to precondition the Krylov subspace methods like GMRES, the preconditioning property of the modified skew-Hermitian triangular splitting iteration is analyzed in detail. Numerical results show that, as both solver and preconditioner, the modified skew-Hermitian triangular splitting iteration method is very effective for solving large sparse positive definite systems of linear equations of strong skew-Hermitian parts. 相似文献