全文获取类型
收费全文 | 3504篇 |
免费 | 469篇 |
国内免费 | 487篇 |
专业分类
化学 | 3702篇 |
晶体学 | 42篇 |
力学 | 33篇 |
综合类 | 37篇 |
数学 | 8篇 |
物理学 | 638篇 |
出版年
2024年 | 8篇 |
2023年 | 45篇 |
2022年 | 111篇 |
2021年 | 108篇 |
2020年 | 176篇 |
2019年 | 133篇 |
2018年 | 96篇 |
2017年 | 110篇 |
2016年 | 165篇 |
2015年 | 148篇 |
2014年 | 167篇 |
2013年 | 428篇 |
2012年 | 242篇 |
2011年 | 182篇 |
2010年 | 142篇 |
2009年 | 165篇 |
2008年 | 177篇 |
2007年 | 210篇 |
2006年 | 191篇 |
2005年 | 183篇 |
2004年 | 158篇 |
2003年 | 166篇 |
2002年 | 155篇 |
2001年 | 94篇 |
2000年 | 78篇 |
1999年 | 59篇 |
1998年 | 55篇 |
1997年 | 62篇 |
1996年 | 87篇 |
1995年 | 67篇 |
1994年 | 38篇 |
1993年 | 28篇 |
1992年 | 33篇 |
1991年 | 28篇 |
1990年 | 24篇 |
1989年 | 24篇 |
1988年 | 19篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1972年 | 5篇 |
排序方式: 共有4460条查询结果,搜索用时 62 毫秒
31.
综述了近年来利用固体电解质电解池消除NO的研究进展.重点总结了电化学消除NO研究体系、电化学消除NO分解机制、O2-在固体电解质电解池中传导的控速步骤、电极种类和形态对NO分解性能的影响以及直流与交流电作用的差异等几个方面的研究结果.在RuO2—Ag—YSZ—Pd电解池上实现的NO选择性分解是迄今为止的最佳结果,500℃下NO的转化率为31.8%,NO的分解活性是O2的分解活性的13倍.该领域今后研究的主要方向是,进一步提高NO分解相对于共存O2离子化的选择性、降低O2-在阴极界面处的传导阻力和探寻可在更低温度传导O2-的新的固体电解质 相似文献
32.
33.
Modeling Studies of the Formation and Destruction of NO in Pulsed Barrier Discharges in Nitrogen and Air 总被引:1,自引:0,他引:1
This paper presents the results of modeling studies on the formation and destruction of NO in pulsed barrier discharges in nitrogen and air. The goals of this work are to identify the major processes involved in the formation and destruction of NO in air discharges, to distinguish between oxidative and reductive paths for NO destruction, to explore the potential importance of excited state reactions, to evaluate the role of water in such systems, and to identify the final products in the absence of heterogeneous processes. In all cases, the systems were modeled with 100×10–4% (100 ppm) of added NO, with and without 3% added water. The focus in all of this work is chemistry in the post-pulse regime. 相似文献
34.
A New Efficient Synthesis of p-Nitrocalix[4]arene 总被引:1,自引:0,他引:1
YongLI JiaSongWANG QiWANG DeShanLI 《中国化学快报》2004,15(4):400-403
A new efficient synthesis of p-nitrocalix[4]arene from calix[4]arene by using nitrogen dioxide is described.The compound is an useful intermediates for the introduction of other functional groups to obtain N containing substituted calix[4]arene.The reaction mechanism is briefly discussed. 相似文献
35.
Savos'kin M. V. Yaroshenko A. P. Mysyk R. D. Vaiman G. E. Vovchenko L. L. Popov A. F. 《Theoretical and Experimental Chemistry》2004,40(2):92-97
New thermally stable intercalation compounds of graphite were obtained by the further intercalation of a series of organic compounds into graphite nitrate. The stabilization is explained by the formation of hydrogen bonds between the protonated form of the modifying substance and neutral surrounding molecules. 相似文献
36.
V. P. Borovik I. Yu. Bagryanskaya Yu. V. Gatilov O. P. Shkurko 《Journal of Structural Chemistry》2003,44(4):650-654
The crystal structures of 2-amino-4-phenyl-9H-pyrimido[4,5-b]indole and its nitrate were determined by XRD analysis. 13C NMR, XRD, and quantum-chemical data indicate that the acid proton is predominantly localized at the N(3) atom of the pyrimidine ring in both isolated nitrate molecules and in molecules in crystal and solution. 相似文献
37.
Densities of four aqueous NaNO3 solutions (0.100, 0.303, 0.580, 0.892 mol-kg–1 H2O) have been measured in the liquid phase with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made at ten isotherms between 292 and 573 K. The range of pressure was 0.1–30 MPa. The total uncertainty of density, pressure, temperature, and concentration measurements were estimated to be less than 0.06%, 0.05%, 10 mK, and 0.014%, respectively. Values of saturated densities were determined by extrapolating experimental P- data to the vapor pressure at fixed temperature and composition. Apparent molar volumes were derived using measured values of density for the solutions and for pure water. The apparent molar volumes were extrapolated to zero concentration to yield partial molar volumes at infinite dilution. The temperature, pressure, and concentration dependence of partial and apparent molar volumes were studied. The measured values of density and apparent and partial molar volume were compared with data reported in the literature. 相似文献
38.
39.
ZheLi DangLi WeiHuang KechangXie 《天然气化学杂志》2005,14(2):115-118
The Cu-Mo/ZSM-5 catalysts with different Cu/Mo ratios were prepared by wet impregnation method, and their catalytic performance for selective catalytic reduction of NOx was studied. The results showed that Cu-Mo/ZSM-5 is a very effective catalyst for NOx catalytic reduction with ammonia, especially when Cu/Mo molar ratio is about 1.5. It not only exhibited the extremely high catalytic activity, but also showed good stability for 02. The bulk phase structure of Cu-Mo/ZSM-5 catalysts was determined by XRD technique, and the results indicated that there is a maximum dispersion for Cu species when Cu/Mo molar ratio is 1.5, and an interaction between Cu and Mo along with HZSM-5 may be present in Cu-Mo/ZSM-5, which may possibly result in a special structure favorable for the catalytic reduction of NOx over Cu-Mo/ZSM-5 catalyst. 相似文献
40.