全文获取类型
收费全文 | 5597篇 |
免费 | 42篇 |
国内免费 | 8篇 |
专业分类
化学 | 3905篇 |
晶体学 | 32篇 |
力学 | 53篇 |
数学 | 835篇 |
物理学 | 822篇 |
出版年
2021年 | 44篇 |
2020年 | 79篇 |
2019年 | 68篇 |
2016年 | 101篇 |
2015年 | 88篇 |
2014年 | 110篇 |
2013年 | 206篇 |
2012年 | 190篇 |
2011年 | 199篇 |
2010年 | 127篇 |
2009年 | 119篇 |
2008年 | 169篇 |
2007年 | 183篇 |
2006年 | 174篇 |
2005年 | 185篇 |
2004年 | 171篇 |
2003年 | 128篇 |
2002年 | 134篇 |
2001年 | 108篇 |
2000年 | 75篇 |
1999年 | 92篇 |
1998年 | 97篇 |
1997年 | 97篇 |
1996年 | 96篇 |
1995年 | 75篇 |
1994年 | 97篇 |
1993年 | 89篇 |
1992年 | 96篇 |
1991年 | 66篇 |
1990年 | 85篇 |
1989年 | 85篇 |
1988年 | 82篇 |
1987年 | 91篇 |
1986年 | 119篇 |
1985年 | 127篇 |
1984年 | 92篇 |
1983年 | 80篇 |
1982年 | 79篇 |
1981年 | 75篇 |
1980年 | 99篇 |
1979年 | 58篇 |
1978年 | 89篇 |
1977年 | 83篇 |
1976年 | 74篇 |
1975年 | 51篇 |
1974年 | 65篇 |
1973年 | 62篇 |
1972年 | 53篇 |
1971年 | 42篇 |
1970年 | 49篇 |
排序方式: 共有5647条查询结果,搜索用时 15 毫秒
71.
72.
73.
A New Approach to Bicyclo[4.1.0]heptane Derivatives The reaction of the dienone 1 with ethyl α-bromoacetate does not furnish the expected glycidic acid ester 2 but leads to the bicyclo[4.1.0]heptenone derivative 3 . The structure of this new compound has been proved by means of spectroscopic methods (1R, 1H-NMR, 13C-NMR, MS). The elucidation of the configuration at C(7) could be realized by measuring a NOE effect. Other α-alkylated α-bromoacetates react with 1 in the same manner. 相似文献
74.
Daria Goldmann Barbara Zdrazil Daniela Digles Gerhard F. Ecker 《Journal of computer-aided molecular design》2017,31(3):319-328
With the public availability of large data sources such as ChEMBLdb and the Open PHACTS Discovery Platform, retrieval of data sets for certain protein targets of interest with consistent assay conditions is no longer a time consuming process. Especially the use of workflow engines such as KNIME or Pipeline Pilot allows complex queries and enables to simultaneously search for several targets. Data can then directly be used as input to various ligand- and structure-based studies. In this contribution, using in-house projects on P-gp inhibition, transporter selectivity, and TRPV1 modulation we outline how the incorporation of linked life science data in the daily execution of projects allowed to expand our approaches from conventional Hansch analysis to complex, integrated multilayer models. 相似文献
75.
76.
This document treats performance parameters in electrochemical engineering. Nomenclature and definitions for electrochemical engineering together with the respective symbols are given. Parameters to account for electrochemical reactions in electrolysis as well as for electrochemical power sources (electrochemical energy generators) are included in this document. 相似文献
77.
78.
Gerhard Knothe 《Macromolecular theory and simulations》1993,2(6):917-927
The number of isomers ir,t for stacked polymeric phthalocyanines in which each phthalocyanine ring is tetrasubstituted or octasubstituted with two different substituents (each benzene moiety substituted with both substitutents) is determined to be where m is the number of substituted phthalonitrile molecules incorporated into the polymer and x is the number of phthalocyanine macrocycles (degree of polymerization; m = 4x). Specifically, for a stacked polymeric phthalocyanine with x = 2; there exist 298 isomers. The stacked polymeric phthalocyanines with substituted phthalocyanine rings possess different symmetry groups (D2h, D2d, C4, C2V or CS E as sole symmetry operation). The results are valid for stacking of other macrocycles similar to phthalocyanine such as prophyrins. 相似文献
79.
Ralf Garbe Jürgen Pebler Kurt Dehnicke Dieter Fenske Helmut Goesmann Gerhard Baum 《无机化学与普通化学杂志》1994,620(4):592-598
Phosphorane Iminato Complexes of Antimony. The Crystal Structures of [Sb2Cl5(NPMe3)2][SbCl6] · CH3CN and [SbCl(NPPh3)]2[SbCl6]2 · 6 CH3CN The title compounds are formed by reaction of antimony pentachloride in acetonitrile solution with the phosphorane iminato complexes SbCl2(NPMe3) and SbCl2(NPPh3), respectively, which themselves are synthesized by reaction of antimony trichloride with Me3SiNPR3 (R = Me, Ph). The complexionic compounds are characterized by 121Sb Mössbauer spectroscopy and by crystal structure determinations. [Sb2Cl5(NPMe3)2][SbCl6] · CH3CN: Space group P41, Z = 4, 3 698 observed unique reflections, R = 0.022. Lattice dimensions at ?60°C: a = b = 1 056.0(1), c = 2 709.6(2) pm. The structure consists of SbCl6? ions and cations [Sb2Cl5(NPMe3)2(CH3CN)]+, in which one SbIII atom and one SbV atom are bridged by the N atoms of the phosphorane iminato ligands. [SbCl(NPPh3)]2[SbCl6]2 · 6 CH3CN: Space group P1 , Z = 2, 5 958 observed unique reflections, R = 0.033. Lattice dimensions at ?60°C: a = 989.4(11), b = 1 273(1), c = 1 396(1) pm, α = 78.33(7), β = 77.27(8)°, γ = 86.62(8)°. The structure consists of SbCl6? ions and centrosymmetric cations [SbCl(NPPh3)(CH3CN)2]22+, in which the antimony atoms are bridged by the N atoms of the phosphorane iminato ligands. 相似文献
80.
Preparation and Characterization of Iodoplatinates MexNH4–xPtI4 (x = 2–4), Mixed Valence Octaiododiplatinates(II,IV) with Pt2I8 Groups Iodoplatinates APtI4 (A = MexNH4–x with x = 2–4) have been prepared by partial oxidation of the correspondent hexaiododiplatinates(II) A2Pt2I6 with I2 in methanolic solutions. X-ray structure analyses of the bronze-coloured needle-shaped crystals of the compounds showed rows of dinuclear anions Pt2I82?, built up by edgesharing planar PtI4 groups with PtII und octahedral PtI6 groups with PtIV. The different space requirement of the cations leads to the formation of three different structures. Within the anion stacks weak intermolecular PtIV? I …? PtII interactions are detectable by Raman spectroscopy. 相似文献