全文获取类型
收费全文 | 741255篇 |
免费 | 92869篇 |
国内免费 | 121062篇 |
专业分类
化学 | 502384篇 |
晶体学 | 7994篇 |
力学 | 38908篇 |
综合类 | 13544篇 |
数学 | 81850篇 |
物理学 | 310506篇 |
出版年
2024年 | 4080篇 |
2023年 | 12688篇 |
2022年 | 15682篇 |
2021年 | 13551篇 |
2020年 | 12329篇 |
2019年 | 16031篇 |
2018年 | 17688篇 |
2017年 | 13770篇 |
2016年 | 15298篇 |
2015年 | 15960篇 |
2014年 | 26403篇 |
2013年 | 23406篇 |
2012年 | 55810篇 |
2011年 | 70224篇 |
2010年 | 31265篇 |
2009年 | 27177篇 |
2008年 | 60552篇 |
2007年 | 60544篇 |
2006年 | 61983篇 |
2005年 | 58078篇 |
2004年 | 50057篇 |
2003年 | 40128篇 |
2002年 | 35871篇 |
2001年 | 27846篇 |
2000年 | 29693篇 |
1999年 | 15029篇 |
1998年 | 8940篇 |
1997年 | 7008篇 |
1996年 | 12255篇 |
1995年 | 10371篇 |
1994年 | 11535篇 |
1993年 | 12496篇 |
1992年 | 11831篇 |
1991年 | 7536篇 |
1990年 | 7388篇 |
1989年 | 6619篇 |
1988年 | 7144篇 |
1987年 | 6651篇 |
1986年 | 6417篇 |
1985年 | 5967篇 |
1984年 | 3735篇 |
1983年 | 3220篇 |
1982年 | 2568篇 |
1981年 | 2031篇 |
1980年 | 1414篇 |
1979年 | 924篇 |
1978年 | 571篇 |
1966年 | 372篇 |
1965年 | 451篇 |
1948年 | 903篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We numerically solve the time-dependent Ginzburg–Landau equations for two-gap superconductors using the finite-element technique. The real-time simulation shows that at low magnetic field, the vortices in small-size samples tend to form clusters or other disorder structures. When the sample size is large, stripes appear in the pattern. These results are in good agreement with the previous experimental observations of the intriguing anomalous vortex pattern, providing a reliable theoretical basis for the future applications of multi-gap superconductors. 相似文献
102.
We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160. 相似文献
103.
The CO_2 adsorption on CaO(001) surface at different coverages from 1/9 monolayer(ML) to 1 ML has been investigated using density functional theory calculations. With the analysis of the most stable adsorption structures at different coverages, the mechanism of CaO(001)surface carbonating into CaCO_3 has been explored. At low coverages(≤1/3 ML), CO_2 molecule prefers sitting in parallel pattern on the CaO(001) surface, while the structure of the CaO(001)surface remains unchanged. At medium coverage(4/9 ~ 2/3 ML), the repulsive interactions between oxygen atoms of CO_2 become stronger, and the calcium carbonation structure appears on the CaO(001) surface. At high coverage( ≥ 7/9 ML), the structure of the CaO(001) surface is deeply damaged, and a few CO_2 molecules have penetrated into the surface and bound to the O atom of the second layer(sub-surface), eventually forming the layered structure of CaCO_3.Additionally, herein has discussed the simulation of HREELS and thermodynamical stability of these structures at different coverages. 相似文献
105.
106.
静止轨道卫星差分吸收光谱仪采用摆扫成像方式对大气进行探测,针对其工作时CCD成像系统信噪比大于1 000、高速探测模式下探测周期小于10min、高分辨率模式下探测周期小于1h的要求,进行CCD成像系统设计.选取CCD47-20作为探测器,设计成像电路实现光谱图像信号的采集和上传.分析了帧叠加和像元合并对时间、空间分辨率的影响.结合帧转移CCD的特点设计了每个位置最后一帧读出时摆镜转动的成像方式,并合理设置了帧叠加数和像元合并数,达到优化成像周期的目的.1s曝光时间条件下,该CCD成像系统的高速、高分辨率模式探测周期分别为515s和3 315s,图像信噪比均大于1 000,污染物观测实验中未出现失帧或重复的现象.该CCD成像系统方案满足静止轨道星载差分吸收光谱仪的探测需求,为静止轨道环境监测仪器设计提供参考. 相似文献
108.
In the excitation of the resonant state followed by the sequential cluster-decay,the in-plane angular correlation method is usually employed to determine the spin of the mother nucleus.However,the correlation pattern exhibited in a two-dimensional angular-correlation spectrum depends on the selected coordinate system.In particular,the parity-symmetric and axial-symmetric processes should be presented in a way to enhance the correlation pattern,whereas the non-symmetric process should be plotted separately to reduce the background.In this study,three coordinate systems previously adopted for correlation patterns in the literature are described and compared to each other.The consistency among these systems is evaluated based on the experimental data analysis for the 10.29-MeV state in ~(18) O.A spin-parity of 4~+ is obtained for all three coordinate systems. 相似文献
110.
We report on a data center network(DCN) architecture based on hybrid optical circuit switching(OCS) and optical burst switching(OBS) interconnect for dynamic DCN connectivity provisioning. With the combination of the centralized and distributed control of the software-defined optical networks, the proposed interconnect can achieve unprecedented flexibility in dealing with both mice and elephant flow in the DCN. Numerical simulation is employed to investigate the performance of the proposed architecture. The results show that the OBS module has preferable performance in dealing with a larger burst packet, and the throughput is constrained by the capacity of the server random access memory module. 相似文献