全文获取类型
收费全文 | 7712篇 |
免费 | 558篇 |
国内免费 | 888篇 |
专业分类
化学 | 5423篇 |
晶体学 | 104篇 |
力学 | 203篇 |
综合类 | 21篇 |
数学 | 331篇 |
物理学 | 3076篇 |
出版年
2024年 | 13篇 |
2023年 | 144篇 |
2022年 | 181篇 |
2021年 | 128篇 |
2020年 | 213篇 |
2019年 | 221篇 |
2018年 | 190篇 |
2017年 | 222篇 |
2016年 | 305篇 |
2015年 | 293篇 |
2014年 | 414篇 |
2013年 | 486篇 |
2012年 | 363篇 |
2011年 | 571篇 |
2010年 | 484篇 |
2009年 | 543篇 |
2008年 | 514篇 |
2007年 | 528篇 |
2006年 | 458篇 |
2005年 | 353篇 |
2004年 | 361篇 |
2003年 | 315篇 |
2002年 | 235篇 |
2001年 | 182篇 |
2000年 | 161篇 |
1999年 | 177篇 |
1998年 | 146篇 |
1997年 | 136篇 |
1996年 | 99篇 |
1995年 | 98篇 |
1994年 | 97篇 |
1993年 | 58篇 |
1992年 | 65篇 |
1991年 | 66篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1988年 | 37篇 |
1987年 | 25篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 33篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1974年 | 6篇 |
排序方式: 共有9158条查询结果,搜索用时 15 毫秒
41.
衍射辐射是由于运动的带电粒子遇到随空间变化的电介质而由感应电流产生的一种辐射. 衍射辐射由于其非阻拦性, 多参数性, 可在线性, 非常适合下一代对撞机和第四代光源的电子束诊断. 简要介绍了其物理机制, 系统的讨论了其在电子束诊断中的应用. 相似文献
42.
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
43.
The 11 800-14 380 cm−1 frequency range has been scanned for rotationally resolved rovibronic transitions in the A2B2-X2A1 electronic band system of the symmetric (C2v) 16O14N16O and 18O14N18O isotopologues and in the corresponding electronic band system of the asymmetric (Cs) 18O14N16O isotopologue. The rotational analysis—reflecting minor differences in mass—in combination with symmetry induced spectral differences allows an identification of 68 16O14N16O vibronic levels, 26 18O14N18O vibronic levels and 51 18O14N16O vibronic levels. The bands are recorded using near infrared fluorescence spectroscopy and a piezo valve based pulsed molecular beam expansion of premixed 18O2 and 14N16O in Ar. The majority of the observed bands is rotationally assigned and can be identified as transitions starting from the vibrational ground state of one of the isotopologues. Numerous hot bands have also been identified. A comparison of the overall spectroscopic features of C2v vs. Cs symmetric species provides qualitative information on symmetry dependence of vibronic couplings. 相似文献
44.
Alain Adenier Eva Cabet-Deliry Sophie Griveau Florence Mercier Christine Vautrin-Ul 《Surface science》2006,600(21):4801-4812
This study investigates the spontaneous grafting of different para-substituted phenyl groups on carbon and metallic surfaces from diazonium salts solutions. Glassy carbon, nickel, zinc and iron plates were allowed to react with an acetonitrile solution of aryldiazonium tetrafluoroborate salt by simple dipping. The surfaces were characterized before and after their immersion by XPS and AFM to evidence the formation of a coating on the different materials. The results are indicative of the presence of substituted phenyl groups on all the investigated surfaces. This study also aims at correlating grafting efficiency with metal reactivities and diazonium salt electronic properties by means of AFM and FT-IRRAS. For this purpose, zinc and nickel were chosen due to their opposite reducing properties and two diazonium salts were selected with electron-donor or -withdrawing para-substituents. The results tend to indicate that redox properties of both partners (diazonium + metal) are of prime importance for grafting to occur. 相似文献
45.
脑细胞激活素药物的化学成分分析 总被引:1,自引:0,他引:1
采用日本岛津LC-60A型高压液相色谱仪和美国P-E3030型原子吸收分光光度计,对该药进行了氨基酸、维生素和化学元素的含量测定。结果表明,该药含有18种氨基酸,不少于3种维生素和20几种化学元素,为进一步改进该药物的合理配制方法和临床应用提供了参考数据。 相似文献
46.
The Randi? index R(G) of a (chemical) graph G is also called connectivity index. Hansen and Mélot [Variable neighborhood search for extremal graphs 6: analyzing bounds for the connectivity index, J. Chem. Inf. Comput. Sci. 43 (2003) 1-14] in their paper, characterized the chemical trees of given order and number of pendent vertices which have the minimum and maximum Randi? index, respectively. In this note, we point out the mistakes in the proofs of their results Theorems 8 and 10, while we still believe that the two theorems are true, and then we give their corrected proofs. 相似文献
47.
48.
用高密度等离子体模型可以计算出一整套输运参数,并且在很宽的等离子体温度和密度范围内有合理的精度,可广泛应用于Z箍缩等离子体、激光聚变和磁约束聚变等领域,并将这个模型计算出的各种输运参数拟合成了实用的公式。 相似文献
49.
50.
Fernando M. Lanas Janete H. Y. Vilegas Srgio Martins Elaine A. F. Gobato 《Journal of separation science》1994,17(4):237-244
An overview is presented of the analytical approaches developed by our research group over the last ten years for analysis of alternative fuel, both biomass and fossil. The alternative fuels are analyzed successively by PLC-8 (preparative liquid chromatography–group-type) fractionation and high resolution gas chromatography. Some of the possibilities for fractionation and characterization of alternative fuels are herein exemplified with sugar cane bagasse pyrolysis products. 相似文献