全文获取类型
收费全文 | 1068篇 |
免费 | 208篇 |
国内免费 | 102篇 |
专业分类
化学 | 808篇 |
晶体学 | 13篇 |
力学 | 30篇 |
数学 | 66篇 |
物理学 | 461篇 |
出版年
2024年 | 1篇 |
2023年 | 30篇 |
2022年 | 26篇 |
2021年 | 41篇 |
2020年 | 62篇 |
2019年 | 55篇 |
2018年 | 39篇 |
2017年 | 38篇 |
2016年 | 55篇 |
2015年 | 66篇 |
2014年 | 66篇 |
2013年 | 76篇 |
2012年 | 104篇 |
2011年 | 99篇 |
2010年 | 74篇 |
2009年 | 55篇 |
2008年 | 70篇 |
2007年 | 64篇 |
2006年 | 52篇 |
2005年 | 38篇 |
2004年 | 32篇 |
2003年 | 29篇 |
2002年 | 23篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1378条查询结果,搜索用时 15 毫秒
191.
Note on Generalized Quantum Gates and Quantum Operations 总被引:1,自引:0,他引:1
Yue-Qing Wang Hong-Ke Du Yan-Ni Dou 《International Journal of Theoretical Physics》2008,47(9):2268-2278
Recently, Gudder proved that the set of all generalized quantum gates coincides the set of all contractions in a finite-dimensional
Hilbert space (S. Gudder, Int. J. Theor. Phys. 47:268–279, 2008). In this note, we proved that the set of all generalized
quantum gates is a proper subset of the set of all contractions on an infinite dimensional separable Hilbert space ℋ. Meanwhile,
we proved that the quantum operation deduced by an isometry is an extreme point of the set of all quantum operations on ℋ.
This subject is supported by NSF of China (10571113). 相似文献
192.
Y. F. Gui W. B. Dou K. Yin P. G. Su 《International Journal of Infrared and Millimeter Waves》2008,29(8):782-791
As low loss dielectric materials, ZnS, MgF2, MgAl2O4 and quartz ceramic have a very important application at millimeter frequencies. However, there is little information about
their dielectric properties in the millimeter wavelength band. To obtain their dielectric properties, an automatic open resonator
measurement system at Ka-band is designed and constructed. The importance on the precision determination of cavity length
over a broad band and the checking of a measurement system are emphasized and their solutions are put forward in this paper
for the first time so far as we know. The solutions of above problems ensure the credibility and high accuracy of our measurement
system. The certified measurement system after a series of checking is used to measure the above materials. Lots of measurement
results show that the standard deviation of measurement error is less than 0.154% in permittivity and 20.42% in loss tangent.
Meanwhile, some experimental summaries on the open resonator technique are provided. Software that controls the measurement
system is developed and it improves the testing efficiency greatly. 相似文献
193.
194.
高端芯片制造所需要的极紫外光刻技术位于我国当前面临35项"卡脖子"关键核心技术之首.高转换效率的极紫外光源是极紫外光刻系统的重要组成部分.本文通过采用双激光脉冲打靶技术实现较强的6.7 nm极紫外光输出.首先,理论计算Gd18+—Gd27+离子最外层4d壳层的4p-4d和4d-4f能级之间跃迁、以及Gd14+—Gd17+离子最外层4f壳层的4d-4f能级之间跃迁对波长为6.7 nm附近极紫外光的贡献.其后开展实验研究,结果表明,随着双脉冲之间延时的逐渐增加,波长为6.7 nm附近的极紫外光辐射强度呈现先减弱、后增加、之后再减弱的变化趋势,在双脉冲延时为100 ns处产生的极紫外光辐射最强.并且,在延时为100 ns处产生的光谱效率最高,相比于单脉冲激光产生的光谱效率提升了33%.此外,发现双激光脉冲打靶技术可以有效地减弱等离子体的自吸收效应,获得的6.7 nm附近极紫外光谱宽度均小于单激光脉冲打靶的情形,且在脉冲延时为30 ns时刻所产生的光谱宽度最窄,约为单独主脉冲产生极紫外光谱宽度的1/3.同时... 相似文献
195.
Back Cover: Room‐Temperature Synthesis of Cu2−xE (E=S,Se) Nanotubes with Hierarchical Architecture as High‐Performance Counter Electrodes of Quantum‐Dot‐Sensitized Solar Cells (Chem. Eur. J. 3/2015)
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
196.
197.
198.
Shaohua Huang Rui Wu Zhengwu Bai Ying Yang Suying Li Xiaowei Dou 《Magnetic resonance in chemistry : MRC》2014,52(9):486-490
Polyvinylpyrrolidone (PVP) was used as a virtual stationary phase to separate p‐xylene, benzyl alcohol, and p‐methylphenol by the chromatographic NMR technique. The effects of concentration and weight‐average molecular weight (Mw) of PVP, solvent viscosity, solvent polarity, and sample temperature on the resolution of these components were investigated. It was found that both higher PVP concentration and higher PVP Mw caused the increase of diffusion resolution for the three components. Moreover, the diffusion resolution did not change at viscosity‐higher solvents. Moreover, the three components showed different resolution at different solvents. As temperature increased, the diffusion resolution between p‐xylene and benzyl alcohol gradually increased, and the one between p‐xylene and p‐methylphenol slightly increased from 278 to 298 K and then decreased above 298 K. It was also found that the polarity of the analytes played an important role for the separation by affecting the diffusion coefficient. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
199.
Dr. Mingzhe Chen Dr. Jin Xiao Dr. Weibo Hua Dr. Zhe Hu Dr. Wanlin Wang Dr. Qinfen Gu Prof. Yuxin Tang Prof. Shu-Lei Chou Prof. Hua-Kun Liu Prof. Shi-Xue Dou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12174-12181
Titanium-based polyanions have been intensively investigated for sodium-ion batteries owing to their superior structural stability and thermal safety. However, their low working potential hindered further applications. Now, a cation and anion dual doping strategy is used to boost the redox potential of Ti-based cathodes of Na3Ti0.5V0.5(PO3)3N as a new cathode material for sodium ion batteries. Both the Ti3+/Ti4+ and V3+/V4+ redox couples are reversibly accessed, leading to two distinctive voltage platforms at ca. 3.3 V and ca. 3.8 V, respectively. The remarkably improved cycling stability (86.3 %, 3000 cycles) can be ascribed to the near-zero volume strain in this unusual cubic symmetry, which has been demonstrated by in situ synchrotron-based X-ray diffraction. First-principles calculations reveal its well-interconnected 3D Na diffusion pathways with low energy barriers, and the two-sodium-extracted intermediate NaTi0.5V0.5(PO3)3N is also a stable phase according to formation energy calculations. 相似文献
200.
Qin Dou Zhao Bin Gao Diankui Xu Lizhi 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6893-6900
Journal of Thermal Analysis and Calorimetry - The leakage of scroll compressor can reduce the working efficiency and cause risk, it is significant to study it in depth, thermal analysis of leakage... 相似文献