全文获取类型
收费全文 | 3858篇 |
免费 | 128篇 |
国内免费 | 13篇 |
专业分类
化学 | 2587篇 |
晶体学 | 51篇 |
力学 | 55篇 |
数学 | 408篇 |
物理学 | 898篇 |
出版年
2022年 | 81篇 |
2021年 | 101篇 |
2020年 | 78篇 |
2019年 | 84篇 |
2018年 | 80篇 |
2017年 | 89篇 |
2016年 | 130篇 |
2015年 | 108篇 |
2014年 | 141篇 |
2013年 | 263篇 |
2012年 | 199篇 |
2011年 | 251篇 |
2010年 | 177篇 |
2009年 | 152篇 |
2008年 | 210篇 |
2007年 | 166篇 |
2006年 | 116篇 |
2005年 | 140篇 |
2004年 | 107篇 |
2003年 | 86篇 |
2002年 | 74篇 |
2001年 | 36篇 |
2000年 | 44篇 |
1999年 | 26篇 |
1998年 | 31篇 |
1997年 | 30篇 |
1996年 | 29篇 |
1995年 | 32篇 |
1994年 | 27篇 |
1993年 | 41篇 |
1992年 | 37篇 |
1990年 | 25篇 |
1989年 | 37篇 |
1988年 | 40篇 |
1987年 | 31篇 |
1986年 | 28篇 |
1985年 | 32篇 |
1984年 | 31篇 |
1983年 | 28篇 |
1982年 | 30篇 |
1981年 | 45篇 |
1980年 | 49篇 |
1979年 | 39篇 |
1978年 | 46篇 |
1977年 | 47篇 |
1976年 | 29篇 |
1975年 | 27篇 |
1974年 | 26篇 |
1973年 | 41篇 |
1972年 | 24篇 |
排序方式: 共有3999条查询结果,搜索用时 15 毫秒
1.
Russian Journal of Organic Chemistry - A highly efficient green protocol has been proposed for the synthesis of symmetrical S-aryl arenesulfonothioates by irradiation of N-hydroxy arenesulfonamides... 相似文献
2.
Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes 下载免费PDF全文
Olena Mykhailiv Monika Imierska Martyna Petelczyc Prof. Dr. Luis Echegoyen Dr. Marta E. Plonska‐Brzezinska 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5783-5793
The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g?1 for the CNOs/Ppy bilayer (electrochemical deposition). 相似文献
3.
4.
5.
6.
7.
Rajiv Manohar G. Tripathi A.K. Srivastava A.K. Prajapati 《Journal of Physics and Chemistry of Solids》2006,67(11):2300-2304
Dielectric properties of polymer-liquid crystal mixture, having constituent polymer, poly-butyl methacrylate (PBMA) and liquid crystal, cholesteryl nonanoate, are reported as a function of frequency and temperature. The measurement has been done in a temperature range of 300-375 K and frequency range of 100 Hz-10 MHz. The dielectric permittivity and dielectric loss shows significant changes with the addition of polymer molecules in liquid crystal. The significant feature of composite formation is that the pure liquid crystal and polymer do not show dielectric relaxation in the frequency range covered, while the composite shows relaxation peak at a particular frequency. The optical transmittance of pure liquid crystal and composite has also been measured and compared. 相似文献
8.
C M Srivastava 《Pramana》1989,32(3):251-267
A theory of high temperature superconductivity in YBa2Cu3O7_δ compound has been developed on the basis of the momentum pairing of electrons through the relativistic Darwin interaction.
The transport behaviour of electrons is explained in terms of a mechanism of correlated electron transfer arising from the
electron-phonon coupling. A model Hamiltonian has been developed to describe the superconducting properties of the system.
This gives an energy gap which is higher than the BCS value. Attempts have been made to explain the absence of isotope effect,
the linear dependence of specific heat, the presence of larger temperature-independent paramagnetism in the normal phase and
the softening of some of the optic phonon modes observed in this system. 相似文献
9.
The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are
compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy
sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along
varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between
them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show
that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class. 相似文献
10.
Benjamin E. Blass Anil Srivastava Amy L. Faulkner James M. Ridgeway 《Tetrahedron letters》2004,45(6):1275-1277
The solid-phase synthesis of a series of imidazo[1,2-b]pyrazol-2-ones, an interesting 5,5-fused ring system, based on diverse set of hydrazine acids and malanonitriles is described. The method involves formation of 5-aminopyrazoles on solid support and subsequent cyclizative cleavage off the resin. Compounds were obtained in acceptable to excellent yields and are suitable for biological evaluation without further purification. 相似文献