全文获取类型
收费全文 | 2674篇 |
免费 | 68篇 |
国内免费 | 29篇 |
专业分类
化学 | 1717篇 |
晶体学 | 13篇 |
力学 | 55篇 |
数学 | 550篇 |
物理学 | 436篇 |
出版年
2024年 | 7篇 |
2023年 | 13篇 |
2022年 | 99篇 |
2021年 | 100篇 |
2020年 | 41篇 |
2019年 | 56篇 |
2018年 | 55篇 |
2017年 | 48篇 |
2016年 | 97篇 |
2015年 | 74篇 |
2014年 | 108篇 |
2013年 | 190篇 |
2012年 | 177篇 |
2011年 | 185篇 |
2010年 | 126篇 |
2009年 | 122篇 |
2008年 | 143篇 |
2007年 | 161篇 |
2006年 | 147篇 |
2005年 | 152篇 |
2004年 | 121篇 |
2003年 | 83篇 |
2002年 | 60篇 |
2001年 | 25篇 |
2000年 | 26篇 |
1999年 | 30篇 |
1998年 | 22篇 |
1997年 | 29篇 |
1996年 | 24篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 18篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 22篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有2771条查询结果,搜索用时 15 毫秒
31.
32.
Aleksandra Mielewczyk-Gryn Tomasz Lendze Katarzyna Gdula-Kasica Piotr Jasinski Andrzej Krupa Boguslaw Kusz Maria Gazda 《Central European Journal of Physics》2013,11(2):213-218
A composite of CaTi0.9Fe0.1O3 and electrolyte material, i.e. magnesium doped La0.98Mg0.02NbO4 was prepared and studied. The phase content and the sample microstructure was examined by an X-ray diffraction method and scanning electron microscopy. EDS measurements were done both for composite samples and the diffusion couple. The electrical properties were studied by four terminal DC method. The high-temperature interaction between the two components of the composite has been observed. It has been suggested that lanthanum diffused into the perovskite phase and substituted for calcium whereas calcium and niobium formed the Ca2Nb2O7 pyrochlore phase. At 1500°C very large crystallites of the pyrochlore were observed. Regardless of strong interaction between the composite components, its total conductivity was weakly dependent on the sintering temperature. 相似文献
33.
34.
Gunnar Aksnes Fayez Y. Khalil Piotr J. Majewski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):157-161
Abstract This study reports rate data of the alkoxide promoted decomposition of triphenyl 3-hydroxypropyl phosphonium chloride, diphenyl di(3-hydroxypropyl)phosphonium chloride, and tetraphenyl phosphonium bromide. Comparison of kinetics, rate constants, and activation parameters of the alkoxide promoted decompositions points to different mechanism as compared to the hydroxyl promoted reaction. The alkoxide reaction is believed to proceed via a hexacovalent intermediate. Reasons for the hexacovalent route are discussed. 相似文献
35.
36.
Judyta Cielecka-Piontek Przemysław Zalewski Anna Jelińska Piotr Garbacki 《Chromatographia》2013,76(21-22):1429-1437
Pharmaceutical analysis based on chromatographic separation is an important part of studies aimed at developing routine quality analysis of drugs. High-performance liquid chromatography (HPLC) is one of the main analytical techniques recommended for drug analysis. Although it meets many criteria vital for analysis, it is time-consuming and uses a relatively high amount of organic solvents compared to other analytical techniques. Recently, Ultra-high-performance liquid chromatography (UHPLC) has been frequently proposed as an alternative to HPLC, which means introducing an environment-friendly approach to drug analysis achieved by reducing the consumption of solvents. It also offers greater chromatographic resolution and higher sensitivity as well as requiring less time due to faster analysis. This review focuses on the basics of UHPLC, compares that technique with HPLC and discusses the possibilities of applying UHPLC for the analysis of different pharmaceuticals and biopharmaceuticals. 相似文献
37.
The 9-[(E)-1,2-dichloroviny1]carbazole is a starting material for synthesis of 9-ethynyl-carbazole [1], which in term is monomer for preparation of photoconductive polymers [2]. Dichlorovinylation of carbazole in a solid-liquid two phase system in the presence of crown and cryptand catalysts has been studied. Application of the Phase Transfer Catalysis in the nonaqueous system increases yield of 9-[(E)-1,2-dichloroviny1]carbazole in comparison to the methods based on liquid-liquid system with benzyltriethylammonium chloride (TEBA) or dimethylsulfoxide (DMSO) as catalysts. 相似文献
38.
39.
We present here a fine singularity analysis of solutions to the Laplace equation in special polygonal domains in the plane. We assume piecewise constant Neumann data on one component of the boundary. Our motivation is to study the so‐called Berg effect, which is explained in the introduction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
40.
Piotr Rzymski Przemysław Niedzielski Jacek Karczewski Barbara Poniedziałek 《Central European Journal of Chemistry》2014,12(12):1232-1238
This paper describes the potential application of a freely suspended cyanobacterial biomass of Microcystis aeruginosa as a sorption material for toxic metals, cadmium (Cd) and lead (Pb) from aqueous solutions. In order to identify the most suitable conditions for removal of these elements (concentration range: 1–20 mg L?1), the laboratory experiments were carried out during different incubation times (1–48 h) and under various temperatures (10–40°C), pH (5–9) and with or without light irradiance. Competitive biosorption of Cd and Pb was also investigated. We found that M. aeruginosa demonstrates high efficiency in removing both of the studied metals from aqueous solutions. Sorption of Pb occurred, however, more rapidly and effectively, and was less disturbed by changes in physico-chemical conditions. Under pH=7, 25°C and light, the removal rates after 3 h and 6 h of incubation, were 90–100% for Pb and 79.5–100% for Cd, respectively. The co-occurrence of the metals decreased the rate of metal biosorption. Pb was sequestered preferentially over Cd. From the results we conclude that freely suspended M. aeruginosa can constitute a promising low-cost, easy-producible biosorbent material for toxic metals in contaminated wastewater. 相似文献