全文获取类型
收费全文 | 8201篇 |
免费 | 169篇 |
国内免费 | 8篇 |
专业分类
化学 | 4524篇 |
晶体学 | 192篇 |
力学 | 169篇 |
数学 | 1345篇 |
物理学 | 2148篇 |
出版年
2022年 | 124篇 |
2021年 | 152篇 |
2020年 | 98篇 |
2019年 | 151篇 |
2018年 | 146篇 |
2017年 | 142篇 |
2016年 | 254篇 |
2015年 | 202篇 |
2014年 | 267篇 |
2013年 | 629篇 |
2012年 | 394篇 |
2011年 | 451篇 |
2010年 | 367篇 |
2009年 | 326篇 |
2008年 | 367篇 |
2007年 | 355篇 |
2006年 | 299篇 |
2005年 | 263篇 |
2004年 | 244篇 |
2003年 | 253篇 |
2002年 | 194篇 |
2001年 | 164篇 |
2000年 | 142篇 |
1999年 | 110篇 |
1998年 | 115篇 |
1997年 | 94篇 |
1996年 | 90篇 |
1995年 | 124篇 |
1994年 | 70篇 |
1993年 | 64篇 |
1992年 | 78篇 |
1991年 | 54篇 |
1990年 | 73篇 |
1989年 | 70篇 |
1988年 | 69篇 |
1987年 | 64篇 |
1986年 | 73篇 |
1985年 | 115篇 |
1984年 | 129篇 |
1983年 | 75篇 |
1982年 | 75篇 |
1981年 | 89篇 |
1980年 | 88篇 |
1979年 | 62篇 |
1978年 | 69篇 |
1977年 | 71篇 |
1976年 | 64篇 |
1975年 | 61篇 |
1974年 | 51篇 |
1973年 | 45篇 |
排序方式: 共有8378条查询结果,搜索用时 14 毫秒
51.
R. Jantas S. Poowiski J. Podeva 《Journal of polymer science. Part A, Polymer chemistry》1989,27(2):475-485
By reacting poly(methacryloyl chloride) (PMKC) with allyl amine, a multiallyl monomer in PMKC matrix has been obtained. Free-radical polymerization of multiallyl monomer in diluted solutions at a concentration of 12 g/L multiallyl monomer occurs partly along ordered allyl units in the matrix and results in ladder-type branched polymers. The polymers obtained are soluble in alcohols, DMF, DMSO and have unreacted allyl double bonds. The structures of multiallyl monomer and homopolymer have been found on the basis of elemental analysis, IR and 1H-NMR spectra and an examination of the products of hydrolysis. The effect of the reaction of degradative chain transfer on the structure of the polymer obtained has been discussed. 相似文献
52.
53.
Boguslaw Zegarliński 《Journal of statistical physics》1986,43(3-4):687-705
We give a condition on a Gibbs measure for an attractive Markov specification, which assures extremality and the global Markov property. As an example of application we consider the class of attractive Markov specifications defined on a compact configuration space over a two-dimensional lattice by the interaction Hamiltonians (assumed to have a finite set of periodic ground configurations) satisfying Peierl's condition. We prove that each extremal Gibbs measure for such a specification, at sufficiently low temperature, has the global Markov property.On leave of absence from the Institute of Theoretical Physics, University of Wrocaw, Poland. 相似文献
54.
Andrzej Barszczewicz Michal Jaszuński Krystyna Kamieńska-Trela Trygve Helgaker Poul Jørgensen Olav Vahtras 《Theoretical chemistry accounts》1993,87(1-2):19-28
Summary
Ab initio calculations of parameters which characterize the NMR spectrum are presented for the cyclopropene molecule. The London orbitals CHF (or GIAO-CHF, Gauge-Independent Atomic Orbital Coupled Hartree-Fock) results for the shielding constants are in good agreement with the experimental data, accurately determined, and with otherab initio values. The calculations of the NMR spin-spin coupling constants have been performed using the Multiconfiguration Time-Dependent Hartree-Fock (MC TDHF) approach. Different basis sets and MC SCF wavefunctions were used to estimate the accuracy of the results. Good agreement is obtained with the coupling constants estimated using the available experimental data.Dedicated to Professor Werner Kutzelnigg on the occasion of his 60th birthday 相似文献
55.
The mechanism of degradation of 9-acetoxy-10-arylanthracenes to anthraquinose with the use of HNO3 in AcOH has been reported. This was proved by way of example on 9-acetoxy-10-(4′-acetoxyphenyl )anthracene (1) by means of separation and identification of intermediate products , and . 相似文献
56.
Z. Rzączyńska A. Ostasz M. Sikorska-Iwan H. Głuchowska E. Olszewska S. Pikus 《Journal of Thermal Analysis and Calorimetry》2006,84(3):575-579
The complexes
of yttrium(III) and lanthanides(III) with 1,2,4,5-benzenetetracarboxylic acid
were prepared as crystalline solids of the general formula Ln4(C10H2O8)3⋅14H2O. They
are insoluble in water. On heating in air or inert gas atmosphere all compounds
lose water molecules; next anhydrous compounds decompose to oxides. The yttrium
complex and heavy lanthanide (from Ho to Lu) ones crystallize in monoclinic
crystal system. The dehydration does not change the crystal structure of the
compounds. 相似文献
57.
Analysis of changes in 35Cl NQR frequency of complexes MCl4.L and MCl4.2L for M = Si, Ge, Sn and Ti was performed. The population of the atomic orbitals was calculated by the quantum chemistry methods PM3 and INDO. The results provided an explanation of the changes in 35Cl NQR frequency and the asymmetry parameter upon complex formation. In the complexes of non-transition elements, a decrease in 35Cl NQR frequency is first of all related to increasing population of pz orbitals on Cl atoms. In the complexes of Ti, the increase in 35Cl NQR frequency depends on a decrease in the pπ to dπ electron density transfer. 相似文献
58.
P. Niedzielski M. Siepak B. Dudzińska-Huczuk 《Central European Journal of Chemistry》2003,1(3):314-324
This paper reports the results of an optimisation study for a procedure to determine the total selenium and its inorganic
species, Se(IV) and Se(VI) using atomic absorption spectrometry combined with hydride generation and in-situ trapping of the
analyte on the inner walls of the graphite tube. With the use of the proposed modification, a detection limit (3σ) of 0.018
ng/ml is achieved. This paper presents exemplary results, according to the proposed procedure, for selenium determination
in samples of marine water. The concentrations of selenium in the samples ranged from <0.02 ng/ml to 0.16ng/ml of Se(IV) and
from <0.02 ng/ml to 0.10 ng/ml of Se(VI). 相似文献
59.
Mariusz Mamiński 《Analytica chimica acta》2005,540(1):153-157
In this paper we report two simple and sensitive spectrophotometric procedures for the determination of dopamine in microfluidic system based on poly(dimethylsiloxane) (PDMS) technology and comparison of their interference-susceptibility. The analytical reactions and measurements were carried out at ambient temperature in a microreactor of total volume 6 μl coupled with a spectrophotometric flow-through cuvette. 相似文献
60.
Copolymerization of acrylonitrile with methacrylates on a matrix has been examined (using methacrylate of p-cresol-formaldehyde resin). It has been found that the copolymerization proceeds at 70° without an initiator. The reactivity ratios depend on the length of the matrix used. The method of calculating Q and e according to the Alfrey-Price scheme has been discussed for the system under investigation. 相似文献