全文获取类型
收费全文 | 371992篇 |
免费 | 4241篇 |
国内免费 | 928篇 |
专业分类
化学 | 186152篇 |
晶体学 | 4878篇 |
力学 | 16565篇 |
综合类 | 15篇 |
数学 | 58873篇 |
物理学 | 110678篇 |
出版年
2021年 | 2609篇 |
2020年 | 2964篇 |
2019年 | 3218篇 |
2018年 | 11895篇 |
2017年 | 12556篇 |
2016年 | 10084篇 |
2015年 | 4840篇 |
2014年 | 5833篇 |
2013年 | 13265篇 |
2012年 | 14552篇 |
2011年 | 23607篇 |
2010年 | 15003篇 |
2009年 | 14767篇 |
2008年 | 21241篇 |
2007年 | 24392篇 |
2006年 | 11073篇 |
2005年 | 15917篇 |
2004年 | 11791篇 |
2003年 | 10856篇 |
2002年 | 8586篇 |
2001年 | 7474篇 |
2000年 | 6172篇 |
1999年 | 4411篇 |
1998年 | 3824篇 |
1997年 | 3786篇 |
1996年 | 3907篇 |
1995年 | 3193篇 |
1994年 | 3330篇 |
1993年 | 3337篇 |
1992年 | 3499篇 |
1991年 | 3350篇 |
1990年 | 3232篇 |
1989年 | 3152篇 |
1988年 | 3053篇 |
1987年 | 3043篇 |
1986年 | 2922篇 |
1985年 | 3849篇 |
1984年 | 4013篇 |
1983年 | 3188篇 |
1982年 | 3493篇 |
1981年 | 3359篇 |
1980年 | 3163篇 |
1979年 | 3311篇 |
1978年 | 3427篇 |
1977年 | 3371篇 |
1976年 | 3316篇 |
1975年 | 3160篇 |
1974年 | 3085篇 |
1973年 | 3251篇 |
1972年 | 2100篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
33.
34.
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
35.
Knyazev A. A. Karyakin M. E. Krupin A. S. Galyametdinov Yu. G. 《Russian Journal of General Chemistry》2015,85(12):2806-2812
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine... 相似文献
36.
37.
38.
39.
Nasirizadeh Navid Dehghani Mohammad Yazdanshenas Mohammad E. 《Journal of Sol-Gel Science and Technology》2015,73(1):14-21
Journal of Sol-Gel Science and Technology - In this paper, a simple method is presented for making a conductive and hydrophobic cotton fabric using a multi-walled carbon nanotube (MWCNT). The... 相似文献
40.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation. 相似文献