全文获取类型
收费全文 | 250543篇 |
免费 | 3092篇 |
国内免费 | 759篇 |
专业分类
化学 | 136448篇 |
晶体学 | 3462篇 |
力学 | 9354篇 |
综合类 | 11篇 |
数学 | 29791篇 |
物理学 | 75328篇 |
出版年
2021年 | 2042篇 |
2020年 | 2436篇 |
2019年 | 2634篇 |
2018年 | 3691篇 |
2017年 | 3599篇 |
2016年 | 5279篇 |
2015年 | 3145篇 |
2014年 | 4688篇 |
2013年 | 11070篇 |
2012年 | 8561篇 |
2011年 | 10216篇 |
2010年 | 7300篇 |
2009年 | 6933篇 |
2008年 | 9792篇 |
2007年 | 9765篇 |
2006年 | 9110篇 |
2005年 | 8266篇 |
2004年 | 7334篇 |
2003年 | 6577篇 |
2002年 | 6312篇 |
2001年 | 6667篇 |
2000年 | 5291篇 |
1999年 | 3888篇 |
1998年 | 3398篇 |
1997年 | 3412篇 |
1996年 | 3283篇 |
1995年 | 2754篇 |
1994年 | 2880篇 |
1993年 | 2918篇 |
1992年 | 3109篇 |
1991年 | 3000篇 |
1990年 | 2900篇 |
1989年 | 2861篇 |
1988年 | 2751篇 |
1987年 | 2751篇 |
1986年 | 2641篇 |
1985年 | 3507篇 |
1984年 | 3628篇 |
1983年 | 2924篇 |
1982年 | 3208篇 |
1981年 | 3070篇 |
1980年 | 2880篇 |
1979年 | 3073篇 |
1978年 | 3179篇 |
1977年 | 3201篇 |
1976年 | 3142篇 |
1975年 | 3000篇 |
1974年 | 2965篇 |
1973年 | 3058篇 |
1967年 | 2013篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is... 相似文献
22.
23.
Laurens Kooijman Dr. Matthias Schuster Christian Baumann Simon Jurt Dr. Frank Löhr Dr. Boris Fürtig Prof. Dr. Peter Güntert Prof. Dr. Oliver Zerbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21151-21158
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR. 相似文献
24.
Kazakova E. F. Dmitrieva N. E. Zvereva N. L. 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2020,94(2):341-344
Russian Journal of Physical Chemistry A - Rapidly quenched alloys of aluminum with cobalt and zirconium are investigated using a combination of means of physicochemical analysis to study the... 相似文献
25.
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
26.
27.
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
28.
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
29.
30.
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