全文获取类型
收费全文 | 15562篇 |
免费 | 2634篇 |
国内免费 | 2973篇 |
专业分类
化学 | 15439篇 |
晶体学 | 103篇 |
力学 | 258篇 |
综合类 | 106篇 |
数学 | 72篇 |
物理学 | 5191篇 |
出版年
2024年 | 45篇 |
2023年 | 228篇 |
2022年 | 461篇 |
2021年 | 640篇 |
2020年 | 766篇 |
2019年 | 593篇 |
2018年 | 546篇 |
2017年 | 612篇 |
2016年 | 673篇 |
2015年 | 688篇 |
2014年 | 860篇 |
2013年 | 1393篇 |
2012年 | 1099篇 |
2011年 | 1052篇 |
2010年 | 816篇 |
2009年 | 935篇 |
2008年 | 955篇 |
2007年 | 1131篇 |
2006年 | 943篇 |
2005年 | 827篇 |
2004年 | 766篇 |
2003年 | 809篇 |
2002年 | 654篇 |
2001年 | 499篇 |
2000年 | 438篇 |
1999年 | 346篇 |
1998年 | 307篇 |
1997年 | 284篇 |
1996年 | 293篇 |
1995年 | 236篇 |
1994年 | 201篇 |
1993年 | 172篇 |
1992年 | 193篇 |
1991年 | 119篇 |
1990年 | 110篇 |
1989年 | 92篇 |
1988年 | 63篇 |
1987年 | 59篇 |
1986年 | 44篇 |
1985年 | 41篇 |
1984年 | 35篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
101.
The features of interaction of a spherical metallic particle with a rarefied thermal plasma flow due to the presence o charges-electrons and ions in the gaseous phase-are considered. Analytical expressions describing charge, momentum, and energy exchange between the plasma and the particle für the cases of strong and weak Debye screening are obtained. It is illustrated that the efficiency of particle heating in the plasma considerably grows as compared with a hot molecular gas due to participation of electrons and ions in file transfer processes. 相似文献
102.
Yu. A. Dobrovolsky P. Jannasch B. Lafitte N. M. Belomoina A. L. Rusanov D. Yu. Likhachev 《Russian Journal of Electrochemistry》2007,43(5):489-501
The 2000–2006 achievements in the field of synthesis, property examination, and application of proton-exchange membranes are reviewed on the basis of more than 120 papers. 相似文献
103.
Electrolysis of dimethyl malonate or methyl cyanoacetate in methanol in the presence of LiCl in an undivided cell leads to formation of 1,1,2,2-cyclopropanetetracarboxylic derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1835–1836, October, 1994.This work was supported by the International Science Foundation (Grant No MHY 000). 相似文献
104.
105.
O. D. Greenwood S. Tasker J. P. S. Badyal 《Journal of polymer science. Part A, Polymer chemistry》1994,32(13):2479-2486
Dielectric barrier air discharge treatment of polyethylene, polypropylene, polyisobutylene, polystyrene, and polyisoprene substrates has been characterized by x-ray photoelectron spectroscopy (XPS). The relative reactivities of these polymers towards silent discharge oxidation are rationalized in terms of ozone molecules interacting with an excited surface. © 1994 John Wiley & Sons, Inc. 相似文献
106.
Marko D. Mihovilovic Bernhard Müller Markus Spina Arjumand I. Durrani Peter Stanetty Georg Dazinger Karl Kirchner 《Monatshefte für Chemie / Chemical Monthly》2006,137(6):785-794
Summary. Recombinant Escherichia coli overexpressing Pseudomonas sp. NCIMB 9872 cyclopentanone monooxygenase (CPMO, EC 1.14.13.16) and Acinetobacter sp. NCIMB 9871 cyclohexanone monooxygenase (CHMO, EC 1.14.13.22) have been utilized in whole-cell Baeyer-Villiger biotransformations of prochiral bicycloketones. A significant difference in substrate acceptance and stereoselectivity was
observed for bicyclo[3.3.0] and bicyclo[4.3.0] substrates. A plausible mechanism of these transformations was established
by means of high level DFT/B3LYP calculations suggesting an essential difference in electronic requirements for a successful
enzymatic conversion, which was similarly encountered in recombinant whole-cell mediated biooxidations. Some of the lactones
produced in the biocatalytic Baeyer-Villiger oxidation represent key intermediates for the synthesis of indole alkaloids. 相似文献
107.
Sam Lohse 《Microchemical Journal》2006,82(1):66-72
Although photooxidation has previously been shown to be successful in removing organic contaminants from water, methods combining the rapid photooxidation of the desired contaminant with easy catalyst manipulation and removal are few and far between. In the absence of an easy means of catalyst removal, the photooxidation process becomes more costly and time consuming, and photocatalysis cannot be employed as an in situ method for the remediation of aqueous organic contaminants. In this study, the photocatalyst was added to an aqueous trichloroethylene (TCE) solution in the form of TiO2-coated buoyant microspheres. The solution, placed in a flow-cell photoreactor along with the buoyant catalyst, was irradiated with a UV-filtered Xenon light source. Limited sample sizes necessitated the development of a low-cost headspace GC/MS analysis method, utilizing a standard direct-injection autosampler. This analytical technique aptly monitored reaction progress and indicated that aqueous TCE concentration decreases by nearly 90% in the first hour of irradiation. Subsequent solvent extraction GC/MS analysis indicated that the TCE is initially sorbed by the photocatalyst spheres, but as irradiation continued, TCE is removed from the catalyst spheres surfaces. During the course of irradiation, the expected TCE mineralization product hydrochloric acid appeared, as indicated by a decrease in pH and ion chromatography analysis. The microsphere-born catalyst was easily removed from the treated solution by filtration. Thus, it is possible that a method for effective, low-cost in situ photooxidation of aqueous organic contaminants will be realized in the near future. 相似文献
108.
Summary Oblique propagating magnetohydrodynamic waves with various wave forms and amplitudes are observed both at the Earth's foreshock
and at comets. The possibility of interpreting some observational results in terms of nonlinear evolution of one- and two-dimensional
hydromagnetic waves is investigated. For this purpose both analytical and numerical techniques are employed. It is found that
an initial monochromatic wave changes its polarization giving origin to magnetosonic shocks and rotational discontinuities;
the time evolution of density-magnetic-field correlation is studied, as a function of the plasma parameters and of the propagation
angle. In the two-dimensional case both a transverse instability and a self-focusing effect may take place. Moreover, a two-dimensional
magnetosonic solution is found, in which the density fluctuations are driven by the total pressure fluctuation as in a one-dimensional
simple wave. These theoretical predictions compare well with the features observed in the solar-wind waves.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
109.
Melvin Keith Carter 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):191-203
Catalytic air oxidation of the aliphatic hydrocarbons n-decane, hexanes, gasoline and diesel fuel was conducted at ambient temperature with novel iron catalysts. The concentration of n-decane in water was reduced from 1.42 g in 100 ml to 0.07 g in 100 ml in 5 h at room temperature forming carbon monoxide and water by means of intermediate aldehydes. Results of FT–IR and GC–MS analyses demonstrated formation of aldehydes and unsaturated alcohols. Carbon monoxide was detected on catalyst residues and in the vapor phase. The indicated catalytic reaction mechanisms are discussed. 相似文献
110.