全文获取类型
收费全文 | 214517篇 |
免费 | 3251篇 |
国内免费 | 519篇 |
专业分类
化学 | 115166篇 |
晶体学 | 3252篇 |
力学 | 7874篇 |
综合类 | 4篇 |
数学 | 27761篇 |
物理学 | 64230篇 |
出版年
2021年 | 1636篇 |
2020年 | 2004篇 |
2019年 | 2116篇 |
2018年 | 2879篇 |
2017年 | 2874篇 |
2016年 | 4765篇 |
2015年 | 3201篇 |
2014年 | 4369篇 |
2013年 | 10516篇 |
2012年 | 8447篇 |
2011年 | 9505篇 |
2010年 | 6712篇 |
2009年 | 6392篇 |
2008年 | 8771篇 |
2007年 | 8483篇 |
2006年 | 7938篇 |
2005年 | 7406篇 |
2004年 | 6732篇 |
2003年 | 5938篇 |
2002年 | 5621篇 |
2001年 | 6091篇 |
2000年 | 4750篇 |
1999年 | 3573篇 |
1998年 | 2956篇 |
1997年 | 2781篇 |
1996年 | 2782篇 |
1995年 | 2490篇 |
1994年 | 2555篇 |
1993年 | 2414篇 |
1992年 | 2736篇 |
1991年 | 2614篇 |
1990年 | 2599篇 |
1989年 | 2448篇 |
1988年 | 2455篇 |
1987年 | 2418篇 |
1986年 | 2318篇 |
1985年 | 3036篇 |
1984年 | 3063篇 |
1983年 | 2672篇 |
1982年 | 2793篇 |
1981年 | 2616篇 |
1980年 | 2535篇 |
1979年 | 2676篇 |
1978年 | 2702篇 |
1977年 | 2633篇 |
1976年 | 2678篇 |
1975年 | 2581篇 |
1974年 | 2567篇 |
1973年 | 2736篇 |
1972年 | 1753篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
JETP Letters - A quasi-two-dimensional plasma crystal in (3 + 1) dimensions has been experimentally observed for the first time; i.e., three spatial coordinates of each microparticles of the... 相似文献
62.
Crystallography Reports - The studies of wide-gap semiconductor materials using electron-beam induced current (EBIC) method are reviewed. The main methods for measuring the diffusion length of... 相似文献
63.
Differential Equations - We study a mixed problem for systems of one-dimensional semilinear hyperbolic equations with variable nonlinearity growth rate and nonlinear boundary conditions. Theorems... 相似文献
64.
Nováková Kateřina Hrdlička Vojtěch Navrátil Tomáš Vyskočil Vlastimil Barek Jiří 《Monatshefte für Chemie / Chemical Monthly》2015,146(5):761-769
Monatshefte für Chemie - Chemical Monthly - The voltammetric behavior of 5-nitroindazole was investigated at polished (p-AgSAE) and at mercury meniscus-modified (m-AgSAE) silver solid amalgam... 相似文献
65.
E. V. Shadrina O. N. Malinkina T. G. Khonina A. B. Shipovskaya V. I. Fomina E. Yu. Larchenko N. A. Popova I. G. Zyryanova L. P. Larionov 《Russian Chemical Bulletin》2015,64(7):1633-1639
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications. 相似文献
66.
67.
68.
69.
João Marcos G. Barbosa Milenna K. Fernandes Rodrigues Lurian C. David Taynara C. e Silva Danielly A. Fortuna Lima Naiara Z. Pereira Emmanuel B. D'Alessandro Anselmo E. de Oliveira Paulo H. Jorge da Cunha Maria Clorinda S. Fioravanti Nelson R. Antoniosi Filho 《Biomedical chromatography : BMC》2020,34(11):e4935
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication. 相似文献
70.
Valentin A. Semenov Dmitry O. Samultsev Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2020,58(6):532-539
The density functional theory calculation of 1H and 13C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated 1H and 13C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases. 相似文献