全文获取类型
收费全文 | 12316篇 |
免费 | 1502篇 |
国内免费 | 1040篇 |
专业分类
化学 | 8960篇 |
晶体学 | 130篇 |
力学 | 536篇 |
综合类 | 110篇 |
数学 | 1613篇 |
物理学 | 3509篇 |
出版年
2023年 | 186篇 |
2022年 | 275篇 |
2021年 | 335篇 |
2020年 | 397篇 |
2019年 | 383篇 |
2018年 | 313篇 |
2017年 | 340篇 |
2016年 | 567篇 |
2015年 | 487篇 |
2014年 | 686篇 |
2013年 | 935篇 |
2012年 | 1077篇 |
2011年 | 1104篇 |
2010年 | 752篇 |
2009年 | 682篇 |
2008年 | 776篇 |
2007年 | 660篇 |
2006年 | 557篇 |
2005年 | 518篇 |
2004年 | 457篇 |
2003年 | 429篇 |
2002年 | 434篇 |
2001年 | 295篇 |
2000年 | 199篇 |
1999年 | 233篇 |
1998年 | 167篇 |
1997年 | 138篇 |
1996年 | 152篇 |
1995年 | 112篇 |
1994年 | 118篇 |
1993年 | 116篇 |
1992年 | 92篇 |
1991年 | 94篇 |
1990年 | 62篇 |
1989年 | 72篇 |
1988年 | 53篇 |
1987年 | 47篇 |
1986年 | 50篇 |
1985年 | 48篇 |
1984年 | 41篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1978年 | 26篇 |
1977年 | 30篇 |
1976年 | 18篇 |
1975年 | 21篇 |
1957年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
131.
A new fluorescent probe 2 is developed that is capable of measuring the concentration of a mixture of sodium and potassium ions in the solution. This probe contains a fluorophore that is utilized in two ways depending on the pH of the solution. 相似文献
132.
Thermal behaviour of a polyhedral oligomeric silsesquioxane with epoxy resin cured by diamines 总被引:1,自引:0,他引:1
Ramírez C. Abad M. J. Barral L. Cano J. Díez F. J. López J. Montes R. Polo J. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):421-429
A new material belongs to the family of polyhedral oligomeric silsesquioxanes, the 1-(3-glycidyl) propoxy-3,5,7,9,11,13,15-isobutylpentacyclo-[9.5.1.1(3,9).1(5,15).1(7,13)]octasiloxane
(glycidylisobutyl-POSS) is characterized by differential scanning calorimetry, thermogravimetric analysis and atomic force
microscopy. Epoxy systems based on diglycidyl ether of bisphenol A (DGEBA) cured with the diamines, 4,4'-diamine-diphenylmethane
(DDM) and 1,4-phenylenediamine (pPDA), were kinetically studied by differential scanning calorimetry in isothermal and dynamic
modes. The thermal behaviour of these systems as the glycidylisobutyl-POSS was added, is discussed later.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
133.
This paper has extended nonequilibrium Monte Carlo (MC) approach to simulate oscillatory shear flow in a lattice block copolymer system. Phase transition and associated rheological behaviors of multiple self-avoiding chains have been investigated. Stress tensor has been obtained based upon sampled configuration distribution functions. At low temperatures, micellar structures have been observed and the underlying frequency-dependent rheological properties exhibit different initial slopes. The simulation outputs are consistent with the experimental observations in literature. Chain deformation during oscillatory shear flow has also been revealed. Although MC simulation cannot account for hydrodynamic interaction, the highlight of our simulation approach is that it can, at small computing cost, investigate polymer chains simultaneously at different spatial scales, i.e., macroscopic rheological behaviors, mesoscopic self-assembled structures, and microscopic chain configurations. 相似文献
134.
135.
Based on the classifications of the four nucleic acid bases, we introduce a new 2-D method of DNA representation: TB-curve, which avoids loss of information accompanying alternative 2-D representation in which the curve standing for DNA overlaps and intersects itself. The method is illustrated on the coding sequence of the first exon of human beta-globin gene. 相似文献
136.
137.
138.
139.
Corona-Avendaño S Rojas-Hernández A Romero-Romo MA Pardavé MP Ramírez-Silva MT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3139-3144
Noradrenaline is a catecholamine which has been largely recognised to play a very important role in biological systems. In view of the neurotransmitter's alleged importance, this work aimed at showing the influence of time on its spectral behaviour using different analytical methods and determining its acidity constants through spectrophotometric titration and by the so-called point-by-point analysis, where the samples are freshly prepared for each pH value investigated at the instant required. Because the catecholamines are light-sensitive and likely to react with the oxygen in the surrounding air, both methods used preclude its incidence onto the samples being analysed under the presence of a nitrogen atmosphere maintained over the solutions. The constants obtained through point-by-point analysis were log beta1 = 30.71+/-0.16, log beta2 = 22.00+/-0.15 and log beta3 = 11.69+/-0.16. 相似文献