全文获取类型
收费全文 | 3796篇 |
免费 | 439篇 |
国内免费 | 209篇 |
专业分类
化学 | 1864篇 |
晶体学 | 58篇 |
力学 | 389篇 |
综合类 | 46篇 |
数学 | 482篇 |
物理学 | 1605篇 |
出版年
2024年 | 8篇 |
2023年 | 35篇 |
2022年 | 88篇 |
2021年 | 96篇 |
2020年 | 107篇 |
2019年 | 91篇 |
2018年 | 88篇 |
2017年 | 109篇 |
2016年 | 143篇 |
2015年 | 98篇 |
2014年 | 154篇 |
2013年 | 324篇 |
2012年 | 199篇 |
2011年 | 218篇 |
2010年 | 174篇 |
2009年 | 199篇 |
2008年 | 252篇 |
2007年 | 236篇 |
2006年 | 201篇 |
2005年 | 192篇 |
2004年 | 169篇 |
2003年 | 169篇 |
2002年 | 113篇 |
2001年 | 116篇 |
2000年 | 98篇 |
1999年 | 122篇 |
1998年 | 84篇 |
1997年 | 69篇 |
1996年 | 44篇 |
1995年 | 68篇 |
1994年 | 44篇 |
1993年 | 46篇 |
1992年 | 49篇 |
1991年 | 32篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 27篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1974年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有4444条查询结果,搜索用时 31 毫秒
81.
Cécile Huybrechts 《Journal of Algebraic Combinatorics》1996,5(4):329-335
Let be a rank three incidence geometry of points, lines and planes whose planes are linear spaces and whose point residues are dual linear spaces (notice that we do not require anything on the line residues). We assume that the residual linear spaces of belong to a natural class of finite linear spaces, namely those linear spaces whose full automorphism group acts flag-transitively and whose orders are polynomial functions of some prime number. This class consists of six families of linear spaces. In the amalgamation of two such linear spaces imposes an equality on their orders leading, in particular, to a series of diophantine equations, the solutions of which provide a reduction theorem on the possible amalgams of linear spaces that can occur in .We prove that one of the following holds (up to a permutation of the words point and plane):A) the planes of and the dual of the point residues belong to the same family and have the same orders,B) the diagram of is in one of six families,C) the diagram of belongs to a list of seven sporadic cases.Finally, we consider the particular case where the line residues of are generalized digons. 相似文献
82.
A model, based on inverse gas chromatography experiments, has been developed for intermolecular interaction and its temperature dependence. The model ascribes to each substance a four-component solubility parameter; the four components reflect the van der Waals, polar, electron donor, and electron acceptor interactive properties. Their values depend on temperature in the same manner as does the cohesive energy. The latter was found to depend only on the critical temperature, the acentric factor, and the reduced temperature. The model was used for evaluation of the solubility parameters from polymer-solvent interaction coefficients and their temperature dependence with high accuracy. For binary solventsolvent mixtures, the free energy of mixing and its temperature dependence, as well as enthalpy of mixing can be derived from this model with a good accuracy. 相似文献
83.
Vaishali Tiwari 《Thermochimica Acta》2006,443(2):206-211
Densities ρ and viscosities η of two hydroxamic acids, N-phenyl-2-chlorobenzo- and N-o-tolyl-4-chlorobenzo-, have been determined as a function of their concentration in aqueous acetone solution at temperatures 303.15 and 313.15 K. Apparent molar volumes, standard-state partial molar volumes and relative viscosities have been calculated. The viscosity data have been analyzed using Jones-Dole equation. The activation thermodynamic parameters of viscous flow have been evaluated using Feakins equation. These were obtained to throw light on the mechanism of viscous flow. Thermodynamic interactions in solutions have been studied in terms of a number of excess functions calculated from the experimental data. The effect of hydroxamic acid concentration and temperature on these parameters has been discussed. The results were interpreted in the light of solute-solvent interactions in aquo-organic media. 相似文献
84.
85.
Traceability of the measurement of analytical parameters capable of evaluating the performance of methods is an important
concept for the assessment of quality for the routine control, especially for residue monitoring of non-authorized medicinal
substances in food from animal origin. The European Decision no. 657/2002/EC recommends to calculate two statistical limits,
CCα and CCβ, which allow to evaluate the critical concentrations above which the method reliably distinguish and quantify
a substance taking into account the variability of the method and the statistical risk to take a wrong decision. The calculation,
which can be derived from the ISO standard no. 11843 is applied on a routine basis. An example displays a very simple way
for evaluating the performance of an LC-MSMS method which has been validated a few years ago and is qualified onto a Micromass
Quattro LCZ tandem mass spectrometer to monitor and confirm the nitrofuran metabolite residues in food from animal origin.
Community Reference Laboratory for Antimicrobial Veterinary Drug Residue Control in Food from Animal Origin 相似文献
86.
87.
The effect of injection procedures on efficiency in micellar electrokinetic capillary chromatography
Summary Micellar electrokinetic capillary chromatography (MECC) involves the application of a high voltage (10–30 KV) across a capillary
column (75μm i.d.) which is filled with a solution containing micelles. The mobile phase in this work consisted of sodium
dodecyl sulfate in an aqueous borate/phosphate buffer system. Injection parameters in MECC were investigated to minimize the
contribution to band-broadening resulting from the injection process. Efficiencies as high as 240,000 theoretical plates/meter
are reported. 相似文献
88.
利用溶胶-凝胶分配理论对氢键溶液的模型体系进行研究, 给出了体系的凝胶化条件以及凝胶点后氢键网络中各类结构参数的计算方案, 并进行了相应的数值计算. 结果表明, 当两类质子受体基团的活性不同时, 质子受体基团的竞争作用对网络结构有一定影响. 这为控制氢键网络结构特征提供了可能的理论线索. 相似文献
89.
V. G. Badelin E. Yu. Tyunina G. V. Girichev N. I. Giricheva O. V. Pelipets 《Journal of Structural Chemistry》2007,48(4):647-653
This paper reports on our mass spectrometric study of sublimation of glycine and DL-alanyl-glycine (Ala-gly). The sublimation enthalpy of Ala-gly has been determined by generalization of the data obtained and the results of AM1 quantum-chemical calculations. A relationship has been found between the sublimation enthalpy (ΔH subl), heat capacity (C P), and the sum of bond lengths (Σn i l i ) in 17 α-amino acid and 9 dipeptide molecules. Correlations are suggested for evaluating ΔH subl of amino acids and peptides. 相似文献
90.
有机锡聚合物兼具杀菌防腐的生物活性功能和一般高分子材料的结构功能,有着潜在的应用前景[1]。本工作应用X射线萤光光谱测定甲基丙烯酸三丁基锡(TBTM)和甲基丙烯酸异戊酯(IPMA)共聚物中锡的含量。方便,迅速地获得了该共聚物的组成,计算了TBTM和IPMA在四氢呋喃中,55℃下共聚合的竞聚率,其结果分别为0.29和0.24。 相似文献