全文获取类型
收费全文 | 2354篇 |
免费 | 291篇 |
国内免费 | 234篇 |
专业分类
化学 | 729篇 |
晶体学 | 17篇 |
力学 | 287篇 |
综合类 | 31篇 |
数学 | 618篇 |
物理学 | 1197篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 41篇 |
2021年 | 46篇 |
2020年 | 68篇 |
2019年 | 58篇 |
2018年 | 41篇 |
2017年 | 72篇 |
2016年 | 83篇 |
2015年 | 66篇 |
2014年 | 126篇 |
2013年 | 186篇 |
2012年 | 140篇 |
2011年 | 161篇 |
2010年 | 127篇 |
2009年 | 158篇 |
2008年 | 181篇 |
2007年 | 137篇 |
2006年 | 132篇 |
2005年 | 126篇 |
2004年 | 95篇 |
2003年 | 81篇 |
2002年 | 85篇 |
2001年 | 84篇 |
2000年 | 62篇 |
1999年 | 57篇 |
1998年 | 57篇 |
1997年 | 49篇 |
1996年 | 71篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 34篇 |
1991年 | 26篇 |
1990年 | 14篇 |
1989年 | 24篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有2879条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
105.
The reactivity of ethyl‐, propyl‐ and octylgallate towards diphenylpicryl hydracil radicals has been measured in homogeneous solution (ethanol) and in Triton X‐100 micellar solutions. Similar reactivities were measured in homogeneous solutions, indicating that the length of the alkyl chain does not influence the reactivity of the phenolic groups. On the other hand, different reactivities were measured in micellar solutions, particularly at low (5 mM) surfactant concentrations. Data obtained at different surfactant concentrations allow estimation of partitioning of the gallates and their intramicellar bimolecular rate constant. The values obtained indicate that all the observed differences in reactivity are attributable to differences in substrate partitioning between the micellar and aqueous pseudophases. In fact, similar values of the intramicellar rate constants were obtained, suggesting that the average location of the reactive groups inside the micelles is independent of the solute alkyl chain length. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
106.
《Physics and Chemistry of Liquids》2012,50(2):257-271
This work presents experimental liquid densities and ultrasonic velocities for a collection of substituted aromatic compounds (isobutylbenzene, 1,3,5-trimethylbenzene, butylbenzene, isopropylbenzene, p-xylene, m-xylene and o-xylene) at the range of temperature 278.15–323.15 K and atmospheric pressure of a collection of halogenated and aromatic hydrocarbons. Fitting equations were applied to data in order to correlate for later computer-based design. The estimation of the studied properties was made by the application of different theoretical procedures. An equation of state based on the generalised Van der Waals theory which combines the Staverman–Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression and the free length theory (FLT) showed a good response at the studied conditions. 相似文献
107.
Two soluble isomerized polyimides(PIs)synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA)with either 2,2′-dimethylbenzidine(2,2′-DMB)or 3,3′-DMB were investigated by means... 相似文献
108.
Conservation equations for mass, momentum and energy have been solved numerically for a cylindrical funnel with louvers (lateral openings on the side wall of the cylindrical funnel through which air can come into it) to compute the suction rate of air into the funnel. The nozzle placed centrally at the bottom of the cylinder ejects high‐velocity hot gaseous products so that atmospheric air gets sucked into the funnel. The objective of the work is to compute the ratio of the rate of mass suction to that of the mass ejected by the nozzle for different operating conditions and geometrical size of the funnel. From the computation it has been found that there exists optimum funnel diameter and optimum funnel height for which the mass suction is the highest. The protruding length of the nozzle into the funnel has almost no effect on the mass suction rate after a certain funnel height. The louvers opening area has a very high impact on the mass suction rate. The entrance length for such a sucking funnel is strikingly much lower compared with a simple cylindrical pipe having uniform flow at the inlet at same Reynolds number. A new correlation has been developed to propose the entrance length for a sucking pipe, the rate of mass suction into it and the exhaust plume temperature over a wide range of operating parameters that are normally encountered in a general funnel operations of naval or merchant ship. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
109.
Is it True That the Normal Valence‐Length Correlation Is Irrelevant for Metal–Metal Bonds? 下载免费PDF全文
Dr. Vijay Singh Dr. Mudit Dixit Dr. Monica Kosa Prof. Dan Thomas Major Prof. Elena Levi Prof. Dr. Doron Aurbach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5269-5276
The most intriguing feature of metal–metal bonds in inorganic compounds is an apparent lack of correlation between the bond order and the bond length. In this study, we combine a variety of literature data obtained by quantum chemistry and our results based on the empirical bond valence model (BVM), to confirm for the first time the existence of a normal exponential correlation between the effective bond order (EBO) and the length of the metal–metal bonds. The difference between the EBO and the formal bond order is attributed to steric conflict between the (TM)n cluster (TM=transition metal) and its environment. This conflict, affected mainly by structural type, should cause high lattice strains, but electron redistribution around TM atoms, evident from the BVM calculations, results in a full or partial strain relaxation. 相似文献
110.
V. N. Mughnetsyan A. A. Kirakosyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2008,43(4):173-176
The effect of interdiffusion of aluminum and indium atoms on the exciton emission energy and binding energy in InxGa1?xAs/AlyGa1?yAs quantum dots is studied. It is shown that the emission energy increases monotonically with increasing diffusion length, while the binding energy has a maximum. 相似文献