全文获取类型
收费全文 | 2039篇 |
免费 | 184篇 |
国内免费 | 173篇 |
专业分类
化学 | 857篇 |
晶体学 | 38篇 |
力学 | 207篇 |
综合类 | 9篇 |
数学 | 99篇 |
物理学 | 1186篇 |
出版年
2024年 | 4篇 |
2023年 | 34篇 |
2022年 | 38篇 |
2021年 | 67篇 |
2020年 | 60篇 |
2019年 | 50篇 |
2018年 | 57篇 |
2017年 | 76篇 |
2016年 | 80篇 |
2015年 | 90篇 |
2014年 | 90篇 |
2013年 | 140篇 |
2012年 | 83篇 |
2011年 | 147篇 |
2010年 | 96篇 |
2009年 | 128篇 |
2008年 | 149篇 |
2007年 | 154篇 |
2006年 | 122篇 |
2005年 | 103篇 |
2004年 | 94篇 |
2003年 | 67篇 |
2002年 | 59篇 |
2001年 | 51篇 |
2000年 | 52篇 |
1999年 | 42篇 |
1998年 | 60篇 |
1997年 | 22篇 |
1996年 | 29篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
排序方式: 共有2396条查询结果,搜索用时 15 毫秒
1.
《Mendeleev Communications》2022,32(5):597-600
Calorimetric monitoring of the autoclave reaction N2O4 + C2H4 at –85 to +10 °C under argon pressure 10–30 bar revealed that the exothermic chemical reaction started at temperatures above –52 °C at 10 bar, whereas an intensive exothermic reaction started at –85 °C and pressure of 30 bar. IR study showed that oligo/polynitroethylene was formed at 30 bar, while carbonyl and hydroxy compound as well as nitrate R–ONO2 formation occurred upon processing at 10 bar. 相似文献
2.
Naoto Takase Junpei Kuwabara Seong Jib Choi Takeshi Yasuda Liyuan Han Takaki Kanbara 《Journal of polymer science. Part A, Polymer chemistry》2015,53(4):536-542
The Pd‐catalyzed polycondensation of 4‐octylaniline with various dibromoarylenes was carried out under microwave heating. Microwave heating led to a decrease in the reaction time and an increase in the molecular weight of the polymers as compared to conventional heating. Microwave heating also allowed the catalyst loading to be reduced to 1 mol %, yielding polymerization results that were comparable to those under conventional heating and 5 mol % catalyst. Investigations regarding field‐effect transistors and organic photovoltaic cells using the obtained poly(arylamine) with azobenzene units revealed that increasing the molecular weight of the polymer led to improved device performance, including hole mobility and power conversion efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 536–542 相似文献
3.
《Physics letters. A》2019,383(17):2090-2092
In this paper, we have used Monte Carlo (MC) method to simulate and study the temperature and doping effects on the electric conductivity of fullerene (C60). The results show that the band gap has reduced by the doping and the charge carrier transport is facilitated from valence band to conduction band by the temperature where is touched a 300 K. In this case, the conductivity reached a value of . The electric conductivity of C60 can increase by the triphenylmethane dye crystal violet (CV) alkali metal to reach at 303 K. Our results of MC simulation have a good agreement with those extracted from literature [10], [33]. 相似文献
4.
Activated carbon production from almond shells using phosphoric acid activation agent was achieved by applying both conventional heating and microwave heating in succession. The morphology and surface properties of activated carbon were studied using thermogravimetric and differential gravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. A surface area of 1128 m2/g was achieved by optimizing the microwave power (500?W), microwave application time (15?minutes), conventional heating time (45?minutes), conventional heating temperature (500?°C), and the phosphoric acid:sample ratio (0.7:1). An adsorption capacity of methylene blue of 148?mg/g and an iodine value of 791?mg/g was obtained for the prepared activated carbon. 相似文献
5.
Jong Chan Lee Jin Young Park So Young Yoon Yong Hun Bae Seung Jun Lee 《Tetrahedron letters》2004,45(1):191-193
A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described. 相似文献
6.
Yu. Satov B. Sharkov H. Haseroth Yu. Smakovski K. Makarov S. Kondrashev V. Roerich A. Stepanov H. Kugler R. Scrivens O. Camut A. Shumshurov A. Balabaev A. Charushin 《Journal of Russian Laser Research》2004,25(3):205-216
Experimental and numerical calculation results devoted to development of an optical system for an ion source based on a repetition rate CO2 laser are described. The laser chain consists of a master oscillator, gas absorber cells, and a four-pass amplifier. The optical system provides smooth laser pulses with variable duration and high spatial quality that ensures efficiency for plasma heating and ion generation. The parameters of the plasma ion component measured in the CERN laboratory are applied for a lead target illumination. 相似文献
7.
8.
9.
A model for the flow of a fluid through a channel with parallel plates is investigated. The channel is narrow, so that the lubrication approximation may be applied. The channel walls are maintained at a constant temperature. Shear heating effects are included and the fluid viscosity decreases exponentially with temperature. When the flow is driven solely by shear stress or imposed velocity at the top, analytical progress is possible. When pressure gradient also drives the flow the problem is solved numerically. 相似文献
10.