全文获取类型
收费全文 | 7869篇 |
免费 | 896篇 |
国内免费 | 970篇 |
专业分类
化学 | 2950篇 |
晶体学 | 72篇 |
力学 | 478篇 |
综合类 | 137篇 |
数学 | 4389篇 |
物理学 | 1709篇 |
出版年
2024年 | 13篇 |
2023年 | 87篇 |
2022年 | 178篇 |
2021年 | 228篇 |
2020年 | 213篇 |
2019年 | 263篇 |
2018年 | 267篇 |
2017年 | 279篇 |
2016年 | 283篇 |
2015年 | 242篇 |
2014年 | 430篇 |
2013年 | 794篇 |
2012年 | 397篇 |
2011年 | 494篇 |
2010年 | 408篇 |
2009年 | 518篇 |
2008年 | 539篇 |
2007年 | 539篇 |
2006年 | 519篇 |
2005年 | 469篇 |
2004年 | 418篇 |
2003年 | 371篇 |
2002年 | 295篇 |
2001年 | 243篇 |
2000年 | 221篇 |
1999年 | 171篇 |
1998年 | 176篇 |
1997年 | 133篇 |
1996年 | 125篇 |
1995年 | 74篇 |
1994年 | 64篇 |
1993年 | 38篇 |
1992年 | 43篇 |
1991年 | 32篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 10篇 |
1985年 | 24篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1957年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有9735条查询结果,搜索用时 15 毫秒
1.
A.Y. El-Etre 《Applied Surface Science》2006,252(24):8521-8525
The inhibitive effect of the extract of khillah (Ammi visnaga) seeds, on the corrosion of SX 316 steel in HCl solution was determined using weight loss measurements as well as potentiostatic technique. It was found that the presence of the extract reduces markedly the corrosion rate of steel in the acid solution. The inhibition efficiency increases as the extract concentration is increased. The inhibitive effect of khillah extract was discussed on the basis of adsorption of its components on the metal surface. Negative values were calculated for the energy of adsorption indicating the spontaneity of the adsorption process. The formation of insoluble complexes as a result of interaction between iron cations and khellin, which present in the extract, was also discussed. 相似文献
2.
3.
This paper gives some global and uniform convergence estimates for a class of subspace correction (based on space decomposition) iterative methods applied to some unconstrained convex optimization problems. Some multigrid and domain decomposition methods are also discussed as special examples for solving some nonlinear elliptic boundary value problems.
4.
Relying on reliability growth testing to improve system designis neither usually effective nor efficient. Instead it is importantto design in reliability. This requires models to estimate reliabilitygrowth in the design that can be used to assess whether goalreliability will be achieved within the target timescale forthe design process. Many models have been developed for analysisof reliability growth on test, but there has been much lessattention given to reliability growth in design. This paperdescribes and compares two models: one motivated by the practicalengineering process; the other by extending the reasoning ofstatistical reliability growth modelling. Both models are referencedin the recently revised edition of international standard IEC61164. However, there has been no reported evaluation of theirproperties. Therefore, this paper explores the commonalitiesand differences between these models through an assessment oftheir logic and their application to an industrial example.Recommendations are given for the use of reliability growthmodels to aid management of the design process and to informproduct development. 相似文献
5.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
6.
L. Brian Lawrence 《Transactions of the American Mathematical Society》2005,357(7):2535-2556
Working in ZFC, we give an example as indicated in the title.
7.
Keye Martin 《Applied Categorical Structures》2003,11(1):27-40
We introduce the triangle inequality for measurement. This is a property that when satisfied by a measurement enables one to construct a metric on the set of elements with measure zero that yields the relative Scott topology. The naturality of this construction permits a categorical solution to the model problem in domain theory for locally compact metric spaces. The first time such a solution has been achieved. 相似文献
8.
9.
Karl Gustafson 《Numerical Linear Algebra with Applications》2004,11(7):649-659
Given the operator product BA in which both A and B are symmetric positive‐definite operators, for which symmetric positive‐definite operators C is BA symmetric positive‐definite in the C inner product 〈x, y〉C? This question arises naturally in preconditioned iterative solution methods, and will be answered completely here. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
10.
Tae Young Kim Dong Myung Kim Won Jung Kim Tae Hee Lee Kwang S. Suh 《Journal of Polymer Science.Polymer Physics》2004,42(15):2813-2820
The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004 相似文献