全文获取类型
收费全文 | 303篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 172篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 95篇 |
物理学 | 44篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 9篇 |
2011年 | 12篇 |
2010年 | 15篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 3篇 |
1987年 | 4篇 |
1982年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1967年 | 3篇 |
1966年 | 7篇 |
1965年 | 6篇 |
1964年 | 3篇 |
1963年 | 5篇 |
1962年 | 5篇 |
1961年 | 7篇 |
1960年 | 8篇 |
1959年 | 4篇 |
1958年 | 4篇 |
1957年 | 3篇 |
1956年 | 2篇 |
1947年 | 7篇 |
1946年 | 6篇 |
1945年 | 2篇 |
1944年 | 3篇 |
1943年 | 2篇 |
1942年 | 3篇 |
1941年 | 5篇 |
1940年 | 2篇 |
排序方式: 共有315条查询结果,搜索用时 296 毫秒
21.
A new bis-andrographolide ether from Andrographis paniculata nees and evaluation of anti-HIV activity 总被引:3,自引:0,他引:3
Reddy VL Reddy SM Ravikanth V Krishnaiah P Goud TV Rao TP Ram TS Gonnade RG Bhadbhade M Venkateswarlu Y 《Natural product research》2005,19(3):223-230
Novel bis-andrographolide ether (1) and six known compounds andrographolide, 14-deoxy-11,12-didehydroandrographolide, andrograpanin, 14-deoxyandrographolide, (+/-)-5-hydroxy-7,8-dimethoxyflavanone, and 5-hydroxy-7,8-dimethoxyflavone have been isolated from the aerial parts of Andrographis paniculata and their structures were established by spectral data. All the isolates were tested for the anti-HIV and cytotoxic activity. 相似文献
22.
Electrostatic assembly of multilayered thin films through sequential adsorption of polyions in layer-by-layer fashion utilizes the strong electrostatic attraction between oppositely charged molecules. We perform molecular dynamics simulations of multilayers of flexible polyelectrolytes around a charged spherical particle. Our simulations establish that the charge reversal after each deposition step is a crucial factor for the steady layer growth. The multilayers appear to be nonequilibrium structures. 相似文献
23.
24.
25.
26.
27.
28.
Baggu Chinnababu Sudina Purushotham Reddy Chitturi Bhujanga Rao Karuturi Rajesh Yenamandra Venkateswarlu 《Helvetica chimica acta》2010,93(10):1960-1966
A simple and highly efficient stereoselective total synthesis of dodoneine ( 1 ), a naturally occurring bioactive 5,6‐dihydro‐2H‐pyran‐2‐one, was achieved. The synthesis involved Keck's asymmetric allylation, iodine‐induced electrophilic cyclization, and Grubbs' catalyzed ring‐closing metathesis as key steps. 相似文献
29.
Varadhi GovindaPankaj Attri P. Venkatesu P. Venkateswarlu 《Journal of Molecular Liquids》2011,164(3):218-225
To understand the molecular interactions between newly synthesized ammonium ionic liquids (ILs) and highly polar solvent dimethylsulfoxide (DMSO), precise measurements such as densities (ρ), ultrasonic sound velocities (u) and viscosities (η) have been performed over the whole composition range at temperature ranging from 298.15 to 308.15 K and at atmospheric pressure. The ILs investigated in the present study included diethyl ammonium acetate ([Et2NH][CH3COO], DEAA) and triethyl ammonium acetate ([Et3NH][CH3COO], TEAA). Further, to gain some insight into the nature of molecular interactions in these mixed solvents, we predicted the excess molar volume (VE), the deviation in isentropic compressibilities (ΔKs) and deviation in viscosity (Δη) as a function of the concentration of IL using the measured properties of ρ, u and η, respectively. Redlich-Kister polynomial was used to correlate the results. The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMSO molecules and their structural factors. 相似文献
30.
Mahabir Prasad Jhanwar Ayineedi Venkateswarlu Reihaneh Safavi-Naini 《Designs, Codes and Cryptography》2014,73(2):529-546
A verifiable secret sharing is a secret sharing scheme with an untrusted dealer that allows participants to verify validity of their own shares. A publicly verifiable secret sharing (PVSS) scheme is a verifiable secret sharing scheme that allows a third party to verify correctness of the distributed shares. We propose an efficient non-interactive PVSS scheme using Paillier additively homomorphic encryption system, and analyze its security in a model that we define in line with the classic semantic-security definition and offering stronger security compared to the previous models. We reduce security of our PVSS scheme to the well studied decisional composite residuosity assumption in this model. 相似文献