全文获取类型
收费全文 | 3909篇 |
免费 | 71篇 |
国内免费 | 13篇 |
专业分类
化学 | 2382篇 |
晶体学 | 10篇 |
力学 | 39篇 |
数学 | 675篇 |
物理学 | 887篇 |
出版年
2021年 | 22篇 |
2020年 | 35篇 |
2019年 | 32篇 |
2018年 | 27篇 |
2016年 | 65篇 |
2015年 | 56篇 |
2014年 | 60篇 |
2013年 | 110篇 |
2012年 | 101篇 |
2011年 | 141篇 |
2010年 | 94篇 |
2009年 | 78篇 |
2008年 | 108篇 |
2007年 | 133篇 |
2006年 | 118篇 |
2005年 | 90篇 |
2004年 | 111篇 |
2003年 | 72篇 |
2002年 | 79篇 |
2001年 | 79篇 |
2000年 | 64篇 |
1999年 | 44篇 |
1998年 | 44篇 |
1997年 | 51篇 |
1996年 | 63篇 |
1995年 | 67篇 |
1994年 | 70篇 |
1993年 | 54篇 |
1992年 | 52篇 |
1991年 | 42篇 |
1990年 | 57篇 |
1989年 | 44篇 |
1988年 | 46篇 |
1987年 | 49篇 |
1986年 | 39篇 |
1985年 | 84篇 |
1984年 | 68篇 |
1983年 | 51篇 |
1982年 | 39篇 |
1981年 | 69篇 |
1980年 | 61篇 |
1979年 | 46篇 |
1978年 | 63篇 |
1977年 | 64篇 |
1976年 | 38篇 |
1975年 | 52篇 |
1974年 | 51篇 |
1973年 | 28篇 |
1972年 | 28篇 |
1960年 | 21篇 |
排序方式: 共有3993条查询结果,搜索用时 15 毫秒
51.
Zinc Complexes of a New N, N, O Ligand The tridentate ligand N, N(2‐dimethylaminoethyl)‐3, 5‐di‐tert.‐butyl‐salicylaldimine ( L H) results from the corresponding salicylic aldehyde and N, N‐dimethyl ethylenediamine. With zinc salts it forms the mononuclear halide complexes [ L ZnCl ˙ CH3OH] ( 1 ) and [ L ZnI ˙ CH3OH] ( 2 ) and the presumably polymeric acetate [ L ZnOCOCH3] ( 3 ). With diethyl zinc and diphenylphosphoric acid it yields the phosphate complex [ L Zn‐OPO(OPh)2 ˙ CH3OH] ( 4 ). The coordination of the complexes, which is between trigonal bipyramidal and square pyramidal, and the character of the five donors in the phosphate complex represent the transition state of a hydrolytic substrate cleavage in a zinc enzyme. 相似文献
52.
H. W. Goedde D. Gehring und R. Hofmann 《Fresenius' Journal of Analytical Chemistry》1965,212(1):238-252
Zusammenfassung Es werden verschiedene Methoden zur Differenzierung genetisch bedingter Enzymvarianten der Pseudocholinesterase (spektrophotometrischer Test, Agar-Diffusionstest, Säulenchromatographie), Versuche zur Charakterisierung der verschiedenen Enzymproteine und der in der Stärkegelelektrophorese auftretenden vier Enzymfraktionen mitgeteilt. Ein Reinigungsverfahren für die Pseudocholinesterase wurde ausgearbeitet; nach der Immunisierung von Kaninchen mit dem angereicherten Enzymprotein wurden mit dem gewonnenen Antiserum immunchemische Versuche durchgeführt.
Die in der Literatur am häufigsten zu findende Bezeichnung Pseudocholinesterase wird hier verwendet.
Wir danken der Deutschen Forschungsgemeinschaft, dem Bundesministerium für Wissenschaftliche Forschung und dem Fonds der Chemischen Industrie für ihre Unterstützung. 相似文献
Summary Methods are reported for the differentiation and characterisation of genetically determined enzyme variants and the enzyme fractions occuring in starch-gel electrophoresis of pseudocholinesterase (spectrophotometrical assays, agar diffusion test, column chromatography). A method has been developed to purify the pseudocholinesterase. Rabbits were immunized against a purified enzyme protein. Results of these immuno-chemical assays are given.
Die in der Literatur am häufigsten zu findende Bezeichnung Pseudocholinesterase wird hier verwendet.
Wir danken der Deutschen Forschungsgemeinschaft, dem Bundesministerium für Wissenschaftliche Forschung und dem Fonds der Chemischen Industrie für ihre Unterstützung. 相似文献
53.
Mercury Compounds with Cyancarbanions. II Synthesis and Crystal Structure of Dimercury(I)-bis(1,1,3,3-tetracyanpropenide) The structure of dimercury(I)-bis(1,1,3,3-tetracyanpropenide), Hg2(tcp)2, has been determined by single-crystal X-ray diffraction methods. The crystals are monoclinic, space group P 21/n. The unit cell dimensions are: a = 9.9193(3) Å, b = 5.6912(6) Å, c = 13.3806(4), β = 92.544(4)° and Z = 2. The mercury atoms in the centrosymmetric cation are three-coordinate with Hg? Hg 2.503, Hg? N 2.207, 2.207, 2.560 Å. tcp behaves as a bidentate ligand forming infinite chains running parallel to the a-axis. 相似文献
54.
Contrary to the results of other semi-empirical all-valence electron methods, the main features concerning the conformation of trans-benzylideneaniline are correctly accounted for using the NDDO method. Based on a modified continuum model the influence of solvents on the molecular structure was estimated. 相似文献
55.
Sucrose ethyleneoxide adducts have been prepared by reaction of sucrose with various amounts of ethyleneoxide inDMSO. The resulting polypode molecules were found to be efficient phase transfer catalysts in nucleophilic substitutions, oxidation and dichlorcarbene generation. Polymerisable polypodes have been obtained by reaction of sucrose ethyleneoxide adducts with methacrylic anhydride or methacryloylchloride in pyridine. Free radical polymerisation of the resulting mixtures of mono- and polyfunctional methacrylic esters of sucrose ethyleneoxide adducts yielded crosslinked gels. These polymer-supported octopus-molecules were found to be efficient triphase catalysts. 相似文献
56.
William Heilman Ernst Kupfer Walter Keller-Schierlein Hans Zhner Heinz Wolf Heinrich H. Peter 《Helvetica chimica acta》1979,62(1):1-6
From cultures of the Avilamycin (Avilamycin A) producing organism, Streptomyces viridochromogenes, strain ETH 23575, a second antibiotic, Avilamycin C, C61H90Cl2O32 could be isolated in crystalline form. Both Avilamycins belong to the group of the Orthosomycins. By IR., 1H- and 13C-NMR. spectroscopy and by transformation to a common derivative it could be proven that Avilamycin A is a methyl ketone, Avilamycin C the corresponding methyl carbinol. 相似文献
57.
Heinrich Hillig Hendrik Küper Wolfgang Riepe Hans Peter Ritter 《Analytica chimica acta》1979,112(2):123-132
Automation of a mass spectrometer—computer system makes it possible to process up to 30 samples without attention after sample loading. An automatic sample changer introduces the samples successively into the ion source by means of a direct inlet probe. A process control unit determines the operation sequence. Computer programs are available for the hardware support, system supervision and evaluation of the spectrometer signals. The most essential precondition for automation — automatic evaporation of the sample material by electronic control of the total ion current — is confirmed to be satisfactory. The system operates routinely overnight in an industrial laboratory, so that day work can be devoted to difficult analytical problems. The cost of routine analyses is halved. 相似文献
58.
On the Reaction of Germanium with Germanium Tetrachloride and on the Existence of the Oxidechlorides GeOCl2 and GeOCl6 at the Equilibrium The above equilibrium was measured in a Gauge-manometer and the enthalpy of formation and the entropy for GeCl2,g were derived from these results. From total pressure measurements and transport experiments of GeO2 with GeCl4 follows, that the oxidechlorides Ge2OCl6 and GeOCl2 are not present in measurable concentrations, that means the enthalpy of formation of GeOCl2 must be higher than ?327 kJ · mol?1. 相似文献
59.