全文获取类型
收费全文 | 23437篇 |
免费 | 827篇 |
国内免费 | 356篇 |
专业分类
化学 | 16202篇 |
晶体学 | 158篇 |
力学 | 517篇 |
综合类 | 30篇 |
数学 | 2990篇 |
物理学 | 4723篇 |
出版年
2023年 | 151篇 |
2022年 | 441篇 |
2021年 | 645篇 |
2020年 | 444篇 |
2019年 | 452篇 |
2018年 | 391篇 |
2017年 | 328篇 |
2016年 | 703篇 |
2015年 | 567篇 |
2014年 | 735篇 |
2013年 | 1316篇 |
2012年 | 1249篇 |
2011年 | 1428篇 |
2010年 | 999篇 |
2009年 | 845篇 |
2008年 | 1222篇 |
2007年 | 1261篇 |
2006年 | 1041篇 |
2005年 | 954篇 |
2004年 | 900篇 |
2003年 | 812篇 |
2002年 | 814篇 |
2001年 | 546篇 |
2000年 | 471篇 |
1999年 | 369篇 |
1998年 | 283篇 |
1997年 | 248篇 |
1996年 | 283篇 |
1995年 | 281篇 |
1994年 | 274篇 |
1993年 | 218篇 |
1992年 | 203篇 |
1991年 | 208篇 |
1990年 | 218篇 |
1989年 | 187篇 |
1988年 | 159篇 |
1987年 | 159篇 |
1986年 | 151篇 |
1985年 | 263篇 |
1984年 | 255篇 |
1983年 | 177篇 |
1982年 | 209篇 |
1981年 | 170篇 |
1980年 | 176篇 |
1979年 | 151篇 |
1978年 | 121篇 |
1977年 | 173篇 |
1976年 | 153篇 |
1975年 | 119篇 |
1973年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
81.
Maria G. Semenova Larisa E. Belyakova Anna S. Antipova Yu. N. Polikarpov Lida Klouda Anna Markovic Michael M. Il'in 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):47-54
We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na+), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed. 相似文献
82.
A. M. Yakunin A. Yu. Silov P. M. Koenraad W. Van Roy J. De Boeck J. H. Wolter 《Superlattices and Microstructures》2003,34(3-6):539
An individual Mn acceptor in GaAs is mapped by cross-sectional scanning tunneling microscopy (X-STM) at room temperature and a strongly anisotropic shape of the acceptor state is observed. An acceptor state manifests itself as a cross-like feature which we attribute to a valence hole weakly bound to the Mn ion forming the (Mn2+3d5+hole) complex. We propose that the observed anisotropy of the Mn acceptor wavefunction is due to the d-wave present in the acceptor ground state. 相似文献
83.
The synthesis of several analogues of (±)-semivioxanthin including five thiophene analogues, using directed metalation are reported. The strategy consisted of the synthesis of functionalized naphthalene or benzo[b]thiophene as building blocks followed by annelation of the pyrone. 相似文献
84.
Homogeneously prepared tosylcelluloses (TC) with degrees of substitution (DS) of DSTos 0.1–1.8 were used as intermediates for the synthesis of methylaminocelluloses (MAC) by nucleophilic substitution with methylamine. TC with DSTos up to 1.1 were shown to be valuable intermediates for selective synthesis of MAC with DSMA varying from 0.1 to approximately 1. No nucleophilic substitution was observed at higher DSTos. At the chosen reaction conditions (60 °C, 48 h) residual tosyl moieties remained unchanged and little hydrolysis took place. The samples obtained were characterized by means of elemental analysis, FTIR and 13C CP/MAS NMR spectroscopy. 13C CP/MAS NMR spectroscopy was found to be an efficient tool for quantification of DSMA. Furthermore, the swelling behaviour in water was investigated and preliminary tests concerning the bilirubin adsorption capacity of MAC were carried out. 相似文献
85.
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
86.
Deák L. Bottyán L. Major M. Nagy D. L. Spiering H. Szilágyi E. Tanczikó F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase... 相似文献
87.
复Finsler流形上的Koppelman-Leray-Norguet公式 总被引:1,自引:1,他引:0
利用不变积分核(Berndtsson核),复Finsler度量和联系于Chern-Finsler联络的非线性联络,研究复Finsler流形上具有逐块光滑C~((1))边界的有界域上(p,q)型微分形式的积分表示,得到了(p,q)型微分形式的Koppelman-Leray-Norguet公式和■-方程的解.作为应用,利用复Finsler度量和联系于Chern-Finsler联络的非线性联络,给出了Stein流形上具有逐块光滑C~((1))边界的有界域上(p,q)型微分形式的Koppelman- Leray-Norguet公式以及■-方程的解,并且得到了Stein流形上实非退化强拟凸多面体上(p,q)型微分形式的积分表示式和■-方程的解. 相似文献
88.
Anna Canale 《Journal of Mathematical Analysis and Applications》2003,287(1):101-117
In unbounded domains we state some a priori bounds for solutions of the Dirichlet problem for linear second order elliptic differential equations in nondivergence form with discontinuous coefficients in weighted spaces. The weight function is related to the distance function from a fixed subset S of ∂Ω. 相似文献
89.
P. Schuurmans J. Wouters P. De Moor N. Severijns W. Vanderpoorten J. Vanhaverbeke L. Vanneste 《Hyperfine Interactions》1992,75(1-4):423-430
Anisotropic α-emission from nuclei in the decay chain from223Ra to207Tl has been observed using low temperature nuclear orientation in combination with high resolution α-detection at 4.2 K. Information
on partial wave amplitudes as well as hyperfine interactions has been extracted. 相似文献
90.