全文获取类型
收费全文 | 42617篇 |
免费 | 3992篇 |
国内免费 | 7351篇 |
专业分类
化学 | 36309篇 |
晶体学 | 1479篇 |
力学 | 902篇 |
综合类 | 407篇 |
数学 | 3034篇 |
物理学 | 11829篇 |
出版年
2024年 | 56篇 |
2023年 | 450篇 |
2022年 | 925篇 |
2021年 | 998篇 |
2020年 | 1279篇 |
2019年 | 1269篇 |
2018年 | 1057篇 |
2017年 | 1420篇 |
2016年 | 1455篇 |
2015年 | 1320篇 |
2014年 | 1793篇 |
2013年 | 3451篇 |
2012年 | 2497篇 |
2011年 | 2797篇 |
2010年 | 2381篇 |
2009年 | 2712篇 |
2008年 | 2802篇 |
2007年 | 2860篇 |
2006年 | 2647篇 |
2005年 | 2478篇 |
2004年 | 2285篇 |
2003年 | 1775篇 |
2002年 | 1534篇 |
2001年 | 1295篇 |
2000年 | 2048篇 |
1999年 | 1552篇 |
1998年 | 1370篇 |
1997年 | 781篇 |
1996年 | 718篇 |
1995年 | 669篇 |
1994年 | 612篇 |
1993年 | 532篇 |
1992年 | 420篇 |
1991年 | 291篇 |
1990年 | 192篇 |
1989年 | 182篇 |
1988年 | 146篇 |
1987年 | 107篇 |
1986年 | 92篇 |
1985年 | 98篇 |
1984年 | 77篇 |
1983年 | 44篇 |
1982年 | 67篇 |
1981年 | 89篇 |
1980年 | 73篇 |
1979年 | 57篇 |
1978年 | 50篇 |
1977年 | 41篇 |
1976年 | 26篇 |
1974年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
WeiMingXU LuLingWU XianHUANG 《中国化学快报》2004,15(11):1279-1280
A mild, regioselective 1, 3-dipolar cycloaddition protocol for the preparation ofphenylselenomethyl isoxazolines through substituted allyl phenyl selenides and nitrile oxides wasreported. 相似文献
82.
Solid Phase Synthesis of 2-Substituted 1,3-Oxazin-6-ones Using Resin-bound Cyclic Malonic Acid Ester
A facile solid phase synthesis of 2-substituted 1,3-oxazin-6-ones using polymer-supported Meldrum‘s acid has been reported. Reaction of the resin-bound cyclic malonic acid ester with triethyl orthoformate and subsequent double substitution with amide, afforded the corresponding polymer-supported acylaminomethylene cyclic malonic acid ester, which upon thermal treatment led to 1, 3-oxazin-6-ones in good yields and with high purity. 相似文献
83.
首先叙述了光纤传输Nd~(3+): YAG激光的优点,接着分析了不同光纤和其传输Nd~(3+): YAG激光的特点。然后通过对光纤传输系统各部分的分析与设计,结合实际,设计了光纤耦合机构。最后,对来自于工件反射光问题提出了解决方案。 相似文献
84.
Mean value in invexity analysis 总被引:1,自引:0,他引:1
In this paper, a generalization of the mean value theorem is considered in the case of functions defined on an invex set with respect to η (which is not necessarily connected). 相似文献
85.
Peter Naur 《BIT Numerical Mathematics》1986,26(2):175-187
The questions raised by A. M. Turing in his paper on thought and machines are discussed. Human thought is considered in turn as a concept of normal language usage, as a basic concept of psychology, and as the basis of intellectual activity. It is concluded that neither of these notions of thought identifies something specific that a human being can or cannot do. The imitation game proposed by Turing for deciding whether a machine can think is found to result from an arbitrary empoverishment of the channel of communication between the interrogator and the item under investigation. Turing's notions of thinking are shown to lead to logical difficulties. An alternative view of consciousness, that would place it beyond the reach of any finite test, is finally discussed. 相似文献
86.
87.
该文讨论了形变诺振子相干态的一些有意义的性质,利用量子代数SUq(3)的形变谐振子实现,构造了SU3(q)在玻色、费米两种情况下的相干态. 相似文献
88.
L.-H. Tang P. Smilauer D.D. Vvedensky 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):409-412
Two types of mechanisms are proposed for mound coarsening during unstable epitaxial growth: stochastic, due to deposition
noise, and deterministic, due to mass currents driven by surface energy differences. Both yield the relation H=(RWL)2 between the typical mound height W, mound size L, and the film thickness H. An analysis of simulations and experimental data shows that the parameter R saturates to a value which discriminates sharply between stochastic () and deterministic () coarsening. We derive a scaling relation between the coarsening exponent 1/z and the mound-height exponent which, for a saturated mound slope, yields .
Received: 11 November 1997 / Revised in final form: 28 November 1997 /
Accepted: 28 November 1997 相似文献
89.
E. Hatta H. Hosoi H. Akiyama T. Ishii K. Mukasa 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):347-349
We have observed a remarkable two-armed spiral in the collapse process of a floating monolayer at the air-water interface
by phase contrast microscopy. This demonstrates that the floating monolayer as a form of soft condensed matter reorganizes
itself due to a certain kind of macroscopic or collective behavior of molecules as it collapses. This pattern formation is
caused by the breakdown of a critical dynamical balance between the deformation of solid domain and the applied surface pressure.
The fragility as well as the flexibility of the floating monolayer can be associated with the observed pattern growth. There
are also observed interesting, periodically arranged collections of molecules in numerous collapsed regions.
Received: 8 July 1997 / Accepted: 4 November 1997 相似文献
90.
本文系统研究了MFX体系中Eu3+荧光光谱特征,着重讨论了X-,M2+及杂质缺陷(主要为O2-)对Eu3+发光的影响. 相似文献