全文获取类型
收费全文 | 43714篇 |
免费 | 2667篇 |
国内免费 | 2144篇 |
专业分类
化学 | 16295篇 |
晶体学 | 475篇 |
力学 | 2011篇 |
综合类 | 146篇 |
数学 | 10057篇 |
物理学 | 11622篇 |
无线电 | 7919篇 |
出版年
2024年 | 69篇 |
2023年 | 329篇 |
2022年 | 538篇 |
2021年 | 626篇 |
2020年 | 646篇 |
2019年 | 534篇 |
2018年 | 1737篇 |
2017年 | 2124篇 |
2016年 | 1347篇 |
2015年 | 1443篇 |
2014年 | 1391篇 |
2013年 | 1831篇 |
2012年 | 4415篇 |
2011年 | 3543篇 |
2010年 | 2842篇 |
2009年 | 2573篇 |
2008年 | 1584篇 |
2007年 | 1493篇 |
2006年 | 1437篇 |
2005年 | 5435篇 |
2004年 | 4496篇 |
2003年 | 2670篇 |
2002年 | 883篇 |
2001年 | 615篇 |
2000年 | 413篇 |
1999年 | 370篇 |
1998年 | 224篇 |
1997年 | 163篇 |
1996年 | 137篇 |
1995年 | 123篇 |
1994年 | 90篇 |
1993年 | 86篇 |
1992年 | 227篇 |
1991年 | 194篇 |
1990年 | 186篇 |
1989年 | 154篇 |
1988年 | 147篇 |
1987年 | 114篇 |
1986年 | 103篇 |
1985年 | 90篇 |
1984年 | 73篇 |
1983年 | 62篇 |
1982年 | 59篇 |
1979年 | 54篇 |
1976年 | 99篇 |
1975年 | 54篇 |
1974年 | 53篇 |
1973年 | 66篇 |
1972年 | 49篇 |
1970年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Non-specific antitumoral activity of staphylococcal enterotoxins 总被引:2,自引:0,他引:2
O N Shcheglovitova A D Voskobo?nik M N Solov'eva M K Fan'kovskaia Iu V Ezepchuk 《Eksperimental?nai?a onkologii?a》1987,9(1):28-30
St. aureus enterotoxins A and B possess an antitumour effect. After intraperitoneal inoculation they decrease the size and in some cases prevent the development of the human hypernephroma in the cheek pouch of golden hamsters. The effect of enterotoxins may possibly consist in inducing the production of endogenous immune interferon which activates the host immune system and enhances the rejection of heterologous tumour cells. 相似文献
82.
83.
The design of controlled-resistance loads for domestic induction heating applications using thin non-magnetic conductive layers is described. Thin metallic layers are fabricated using the phase vapour deposition technique. Such layers would enable vessels, the inductive behaviour of which was similar to those fabricated with conventional ferromagnetic bulk materials, to be manufactured. Optimum layer thickness is investigated using an analytical impedance model of the complete induction system 相似文献
84.
We use the PCP-SAFT equation of state, which is of the Van der Waals type and has a sound physical basis, to predict mixture properties, such as vapor–liquid and liquid–liquid equilibria, as well as excess enthalpies. We use molecular properties, such as dipole moment, quadrupole moment, polarizability and dispersion interaction coefficients, that have been determined quantum mechanically in Part I of this publication and adjust the remaining three pure compound parameters to pure compound data. We finally present a new combination rule for the dispersion energy parameter ? that is based on the quantum mechanically determined data. The predictions based on quantum mechanically determined pure compound properties along with the new combination rule show an improved performance compared to the original PCP-SAFT combination rule. 相似文献
85.
86.
Kai Konola 《通信世界》2007,(8):5
3GSM大会的规模一年比一年大,此次是我连续第六次参加3GSM大会.仅大会的前3天就有55,000多名参观者,使今年的大会成为最热闹的一届. 相似文献
87.
M. A. Rizzutto N. Added M. H. Tabacniks F. R. Espinoza-Qui?ones S. M. Palacio R. M. Galante R. M. Galante N. Rossi R. A. Welter A. N. Módenes 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(3):727-731
Summary Kulcsszavak (angolul, ha nem azonos az elozovel) 相似文献
88.
Peptidosulfonamides are an emerging group of peptidomimetics with a variety of applications in medicinal chemistry. We present a novel approach to the synthesis of peptidosulfonamides, and apply it to a series of new potential inhibitors of the bacterial peptidoglycan biosynthesis enzymes MurD and MurE. The synthesis was conducted via N-phthalimido β-aminoethanesulfonyl chlorides, which are new building blocks for the synthesis of peptidosulfonamides. In the most crucial step, sulfonic acids or their sodium salts were converted into the corresponding sulfonyl chlorides using an excess of either SOCl2 or SOCl2/DMF, and then coupled to the C-protected amino acid. None of the compounds significantly inhibited MurD, however, some inhibited MurE; one had an IC50 below 200 μM, which constitutes a promising starting point for further development. Molecular modelling simulations were performed on two analogues to investigate the absence of inhibitory activity of the sulfonamide compounds on MurD. 相似文献
89.
Kai Wang Huan-yu Li Jian-ping Li Zhi-gang Zhang Ning Zhang Lu Chai Qing-yue Wang 《Optics Communications》2006,265(2):369-372
Recently, the semiconductor saturable absorber mirror (SESAM) has become a key component of passive mode-locked solid-state lasers. Here we present a simple method based on the reflection Z-scan technique to measure the key optical parameters of SESAM such as saturation fluence and modulation depth. The experimental results demonstrate that our method is able to perform with a high accuracy of 10−4 and a dynamic range of over four orders of magnitude. 相似文献
90.
合成了重稀土高氯酸盐甲基苯甲酰甲基亚砜配合物RE(ClO4)3·L5·C2H5OH(RE=Gd,Tb,Dy,Tm,Yb;L=C6H5COCH2SOCH3).经元素分析、稀土络合滴定、摩尔电导及热重分析确定了配合物的组成,测定了配体及配合物的IR谱、1H NMR及铽配合物的磷光光谱、荧光激发和发射光谱,根据荧光发射光谱数据计算了铽配合物的各能级值. 相似文献