全文获取类型
收费全文 | 2285篇 |
免费 | 235篇 |
国内免费 | 281篇 |
专业分类
化学 | 1096篇 |
晶体学 | 7篇 |
力学 | 311篇 |
综合类 | 53篇 |
数学 | 715篇 |
物理学 | 619篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 61篇 |
2021年 | 73篇 |
2020年 | 64篇 |
2019年 | 57篇 |
2018年 | 52篇 |
2017年 | 84篇 |
2016年 | 113篇 |
2015年 | 93篇 |
2014年 | 149篇 |
2013年 | 157篇 |
2012年 | 134篇 |
2011年 | 146篇 |
2010年 | 108篇 |
2009年 | 159篇 |
2008年 | 143篇 |
2007年 | 132篇 |
2006年 | 144篇 |
2005年 | 135篇 |
2004年 | 99篇 |
2003年 | 98篇 |
2002年 | 73篇 |
2001年 | 56篇 |
2000年 | 60篇 |
1999年 | 61篇 |
1998年 | 47篇 |
1997年 | 46篇 |
1996年 | 37篇 |
1995年 | 26篇 |
1994年 | 34篇 |
1993年 | 20篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1978年 | 1篇 |
排序方式: 共有2801条查询结果,搜索用时 31 毫秒
1.
空间遥感相机长条反射镜较圆反射镜的整体刚度相差很大,整个组件在随火箭发射过程中因力学环境引起的自身位置改变导致面形的微小畸变从而对成像质量造成严重影响。因此,反射镜组件的设计就成为整个相机系统研制的重点与难点之一。对其进行科学、严谨的力学环境仿真是设计中的有效辅助手段。对某相机的长条反射镜组件动力学响应进行了较为深入的研究,借助MSC-patran,用有限元法进行了求解。获得了组件的动力学特性。 相似文献
2.
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
3.
A theorem of Birkhoff‐Frink asserts that every algebraic closure operator on an ordinary set arises, from some algebraic structure on the set, as the corresponding generated subalgebra operator. However, for many‐sorted sets, i.e., indexed families of sets, such a theorem is not longer true without qualification. We characterize the corresponding many‐sorted closure operators as precisely the uniform algebraic operators. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
Two groups of 10 speech-language pathology graduate students were each given 7 weeks of singing lessons to determine whether voice lessons could have an effect on their clinical and perceptual skills. Pre-, mid-, and posttests to measure various skills were designed and implemented. With use of paired sample statistical testing, statistically significant results were obtained. In addition, the subjective responses of the students show that the lessons were effective in improving pitch perception, breath control, and legato production or easy onset. This study supports efforts to integrate curricula in vocal performance and speech-language pathology. 相似文献
5.
A. D. Zamanov 《Mechanics of Composite Materials》2005,41(1):49-54
The possibility of using the finite-element method for investigating two-dimensional problems on natural vibrations in the mechanics of composite materials with curved structures is considered. With the example of a hinge-supported strip made of a composite material with a locally curved structure, the influence of geometrical and mechanical parameters of the strip on its eigenfrequencies is examined. It is established that the presence of local curving in the structure of strip material decreases the magnitude of eigenfrequencies.Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 1, pp. 71–78, January–February, 2005. 相似文献
6.
7.
A. Truffert 《Annals of Operations Research》1991,30(1):115-156
The conditional expectation of integrands and random sets is the main tool of stochastic optimization. This work wishes to make up for the lack of real synthesis about this subject. We improve the existing hypothesis and simplify the corresponding proofs. In the convex case we especially study the problem of the exchange of conditional expectation and subdifferential operators. 相似文献
8.
张贵婷 《中国惯性技术学报》2007,(8)
下穿京港澳高速公路顶推箱涵是郑开大道的关键控制性工程,顶进过程中箱涵的裂缝控制是该顶推工程成功与否的重要因素。经实践结果表明,临时支撑结构达到了预期的目的,值得应用推广。 相似文献
9.
Simone Alfarano Iván Barreda-Tarrazona Eva Camacho-Cuena 《Central European Journal of Operations Research》2006,14(4):417-433
In this paper, we analyze the behavior of a group of heterogeneously informed investors in an laboratory asset market. Our experimental setting is inspired by Huber et al. (On the benefit of information in markets with heterogeneously informed traders: an experimental study, 2004). However, instead of their system of cumulative and exogenously given information structure, we introduce an information market where the traders can buy an imperfect prediction of the future value of the dividend with a maximum anticipation of four periods. The accuracy of the prediction decreases with the chosen time horizon, whereas its price remains constant. Our results confirm a non-strictly monotonic increasing value of the information. 相似文献
10.