全文获取类型
收费全文 | 41814篇 |
免费 | 15765篇 |
国内免费 | 56篇 |
专业分类
化学 | 54153篇 |
晶体学 | 32篇 |
力学 | 1097篇 |
数学 | 1562篇 |
物理学 | 791篇 |
出版年
2024年 | 422篇 |
2023年 | 4243篇 |
2022年 | 1399篇 |
2021年 | 2399篇 |
2020年 | 4671篇 |
2019年 | 2216篇 |
2018年 | 2369篇 |
2017年 | 600篇 |
2016年 | 5538篇 |
2015年 | 5500篇 |
2014年 | 4921篇 |
2013年 | 5096篇 |
2012年 | 3029篇 |
2011年 | 981篇 |
2010年 | 3327篇 |
2009年 | 3255篇 |
2008年 | 1019篇 |
2007年 | 709篇 |
2006年 | 136篇 |
2005年 | 121篇 |
2004年 | 102篇 |
2003年 | 87篇 |
1995年 | 131篇 |
1994年 | 88篇 |
1993年 | 216篇 |
1992年 | 103篇 |
1991年 | 80篇 |
1990年 | 70篇 |
1989年 | 73篇 |
1988年 | 126篇 |
1987年 | 106篇 |
1986年 | 89篇 |
1985年 | 97篇 |
1984年 | 94篇 |
1983年 | 120篇 |
1982年 | 107篇 |
1981年 | 124篇 |
1980年 | 139篇 |
1979年 | 136篇 |
1978年 | 139篇 |
1977年 | 192篇 |
1976年 | 236篇 |
1975年 | 218篇 |
1974年 | 218篇 |
1973年 | 133篇 |
1972年 | 173篇 |
1971年 | 139篇 |
1970年 | 225篇 |
1969年 | 135篇 |
1968年 | 145篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Axial blocking in various binary (GaAs, GaP, InSb, GaN) and ternary ((Ga, Al)P; (Ga, Al)As; (Ga, Al)Sb; (Ga, In)As) single crystals and epitaxial layers of the AIIIBV-type has been investigated by means of Rutherford backscattering with 0.5 MeV- and 1 MeV-protons. The angular distributions of the latter has been measured with solid-state detectors and with photographic plates. The observed “zero-depth” values of the blocking dips are in fair agreement with theoretical predictions by Barrett. Some applications of proton blocking and channeling to AIIIBV-compounds by backscattering are briefly described and some measuring examples are given. 相似文献
92.
Roberta Cavalli Emilio Marengo Otto Caputo Elena Ugazio Maria Rosa Gasco 《Journal of Dispersion Science and Technology》2013,34(7):717-734
The influence of twenty five different alcohols on the formation of warm oil-in-water (O/W) microemulsions was investigated. Selected concentrations of each alcohol were added to fixed amounts of stearic acid, Tween 20 and water at 65 ° C. Fifteen alcohols formed microemulsions, at least at one of the concentrations. A pattern recognition study was performed to elucidate the activities of the alcohols by Principal Component Analysis (PCA). Linear Discriminant Analysis (LDA) was used to classify them. Two classification functions, obtained for alcohols forming / not forming microemulsions, suggest that the formation of warm O/W microemulsion is linked to the nature and the dimension/lipophilicity of the alcohol. 相似文献
93.
94.
A solid state metathesis (SSM) reaction was investigated with respect to the formation of rare‐earth carbodiimides, the role of the co‐produced salt (LiCl), and the eutectic flux medium (LiCl/KCl). A SSM reaction is characterized by an exothermic reaction in which a salt (often LiCl) is coproduced. When the salt melts, it can serve as a useful medium for the crystallization of a desired product. An improved crystal growth can be observed by using an eutectic flux. However, the composition of an eutectic LiCl/KCl flux is altered when LiCl is produced during the reaction. The thermal effects concerning the endothermic melting of the flux and the exothermic ingnition of the SSM reaction may compensate each other, which is not necessarily a drawback for the reaction to proceed. 相似文献
95.
Maurits Kuiper Manfred Speldrich Helmut Schilder Prof. Dr. Heiko Lueken 《无机化学与普通化学杂志》2012,638(10):1432-1436
Abstract. The magnetic behavior of the mononuclear nd1 systems MCp2Cl2 (M = V4+[3d1], Nb4+[4d1], Ta4+[5d1], space group P21/c, pseudosymmetry of the molecules C2v) deviates from pure single ion spin magnetism on account of ligand field effect (Hlf), spin‐orbit coupling (Hso), and intermolecular spin‐spin exchange interactions (Hex). For both VCp2Cl2 and NbCp2Cl2 excellent adaptations to the measured susceptibility data were obtained (2 K ≤ T ≤ 300 K) on the basis of spectroscopic data (lf, so) and cooperative metal–metal interactions (ex) of antiferromagnetic nature [molecular field model (mf)]. For TaCp2Cl2 experimental term structure data are not available. Therefore, Jørgensen's spectroscopical series (g‐factor of the central ion) was applied to extrapolate the data set for TaCp2Cl2. Hlf, Hso, and Hex (antiferromagnetic) increase in the order 3d1 → 4d1 → 5d1 leading, with rising atomic number of the metals, to a distinct enhancement of the magnetic anisotropy. At 4 K the μeff components μeff,y (oriented perpendicular to the cg–M–cg plane; “cg” = center of gravity of the Cp ring), μeff,z (oriented along the twofold pseudoaxis), and μeff,x are 1.73, 1.69, 1.68 (V), 1.73, 1.62, 1.59 (Nb), and 1.71, 1.59, 1.49 (Ta). While μeff,y is independent of T, both μeff,z and μeff,x decrease with decreasing T. 相似文献
96.
97.
98.
99.
100.