全文获取类型
收费全文 | 18437篇 |
免费 | 3356篇 |
国内免费 | 2575篇 |
专业分类
化学 | 10683篇 |
晶体学 | 200篇 |
力学 | 1661篇 |
综合类 | 178篇 |
数学 | 1130篇 |
物理学 | 10516篇 |
出版年
2024年 | 34篇 |
2023年 | 162篇 |
2022年 | 484篇 |
2021年 | 608篇 |
2020年 | 698篇 |
2019年 | 586篇 |
2018年 | 602篇 |
2017年 | 735篇 |
2016年 | 823篇 |
2015年 | 628篇 |
2014年 | 989篇 |
2013年 | 1893篇 |
2012年 | 1131篇 |
2011年 | 1178篇 |
2010年 | 1018篇 |
2009年 | 1148篇 |
2008年 | 1207篇 |
2007年 | 1127篇 |
2006年 | 1131篇 |
2005年 | 909篇 |
2004年 | 927篇 |
2003年 | 797篇 |
2002年 | 687篇 |
2001年 | 632篇 |
2000年 | 578篇 |
1999年 | 432篇 |
1998年 | 448篇 |
1997年 | 380篇 |
1996年 | 349篇 |
1995年 | 297篇 |
1994年 | 258篇 |
1993年 | 240篇 |
1992年 | 224篇 |
1991年 | 165篇 |
1990年 | 134篇 |
1989年 | 121篇 |
1988年 | 117篇 |
1987年 | 89篇 |
1986年 | 64篇 |
1985年 | 51篇 |
1984年 | 55篇 |
1983年 | 22篇 |
1982年 | 42篇 |
1981年 | 27篇 |
1980年 | 18篇 |
1979年 | 18篇 |
1978年 | 23篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
Sylvia Pulmannová 《International Journal of Theoretical Physics》2003,42(5):907-919
Tensor products of quantum logics and effect algebras with some known problems are reviewed. It is noticed that although tensor products of effect algebras having at least one state exist, in the category of complex Hilbert space effect algebras similar problems as with tensor products of projection lattices occur. Nevertheless, if one of the two coupled physical systems is classical, tensor product exists and can be considered as a Boolean power. Some applications of tensor products (in the form of Boolean powers) to quantum measurements are reviewed. 相似文献
92.
93.
本文实验发现具有较大密度和较高速度的93W钨合金长杆模拟弹的穿靶深度反而比密度较小,速度较低的90W钨合金长杆弹的穿靶深度小.针对这一现象,本文从两种材料在侵彻环境下的细观响应特性的差异上给出了有实验根据的合理分析,结论是90W在侵彻环境下较易于形成绝热剪切带,从而在弹头部发生“自锐化”效应所致. 相似文献
94.
95.
考虑到量子相干效应和界面散射效应 ,利用 L ambert理论模型 ,计算正常金属 /绝缘层 /超导 /绝缘层 /正常金属双垒隧道结中的准粒子输运系数和隧道谱。研究表明 :( 1)所有的准粒子输运系数和电导谱在超导能隙之上都随能量作周期性振荡 ,其振荡周期依赖于超导层的厚度 ;( 2 )在超导能隙之上 Andreev反射系数随能量呈现周期性消失现象 ;( 3)在绝缘层势垒强度取很大的隧道极限下 ,超导层中会形成一系列的准粒子束缚态 ,其位置由量子化条件决定 ;( 4)界面散射效应不仅能压低各子能隙电导峰 ,还能使子能隙电导峰劈裂为两个峰。 相似文献
96.
A simple procedure for the synthesis of an important standard, isotopically enriched methylmercury, which is not commercially available, has been established successfully. The isotopically enriched standard synthesized is utilized in conventional isotope dilution mass spectrometry (IDMS), as well as in speciated IDMS (SIDMS), for determination of the true concentration of methylmercury in environmental samples. The CH3201Hg+ standard has been synthesized from commercially available 201HgO and tetramethyltin. The synthesis time required is 1 h at 60°C. The product is highly pure, yielding more than 90% as 201Hg in CH3201Hg+. Hazardous dimethylmercury does not occur during this synthesis procedure. The product synthesized was analyzed using high‐performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (ICP‐MS) and ICP‐MS alone in order to determine its concentration, isotopic composition and purity. The stability of the product was also evaluated for over 6 months and found to be stable at 4°C in the dark. The isotopically enriched methylmercury synthesized can be used in SIDMS and IDMS analyses as a standard. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
97.
On the basis of the hydrodynamic equations for nonlinear elastic-gravity waves beneath a solid ice cover and their Hamiltonian representation, a three-wave kinetic equation for the time evolution of the wave spectrum is formulated. The properties of the kernel of the kinetic integral describing the nonlinear interactions between wave triplets are investigated. An algorithm for numerically calculating the kinetic integral is developed. The rate of nonlinear energy transfer over the wave spectrum is estimated quantitatively and its most important characteristics are found. 相似文献
98.
Anna Avallone 《Mathematica Slovaca》2007,57(2):129-140
We prove the existence of separating points for every countable family of nonatomic σ-additive modular measures on a σ-complete lattice ordered effect algebra.
相似文献
99.
S. A. Kirillov A. Morresi M. Paolantoni P. Sassi 《Journal of Physical Organic Chemistry》2007,20(8):568-573
The most obvious consequence of the concept of aromaticity is the common confidence that in aromatic compounds, bond lengths do not alternate and are between typical to the single and double ones. However, in 1994, performing crystal structure investigations of substituted pyridines and their salts, Krygowski and co‐workers have discovered a very surprising angular group induced bond alteration (AGIBA) effect: It appears that some angular substituents, like methoxy or nitrozo groups, can induce bond alternation in aromatic rings. Crystal studies do not allow one to operate with liquids that are more common in organic chemistry. This paper presents the first possible evidence of spectroscopic manifestations of the AGIBA effect. Raman spectra of the liquid toluene are analyzed. It is found that instead of being single, the line corresponding to the ring breathing vibrations is clearly split by 1.0–1.4 cm?1, thus indicating the presence of two (cis‐ and trans‐) AGIBA isomers. The energy difference between these isomers estimated in temperature dependent Raman studies is found equal to 6.68 kJ mol?1. The low‐wavenumber line therefore corresponds to the cis‐AGIBA isomer and the high‐wavenumber line to the trans‐AGIBA isomer stabilized by the AGIBA effect. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
100.