全文获取类型
收费全文 | 13447篇 |
免费 | 2593篇 |
国内免费 | 1706篇 |
专业分类
化学 | 9487篇 |
晶体学 | 127篇 |
力学 | 900篇 |
综合类 | 88篇 |
数学 | 1664篇 |
物理学 | 5480篇 |
出版年
2024年 | 46篇 |
2023年 | 284篇 |
2022年 | 477篇 |
2021年 | 513篇 |
2020年 | 541篇 |
2019年 | 483篇 |
2018年 | 476篇 |
2017年 | 413篇 |
2016年 | 588篇 |
2015年 | 654篇 |
2014年 | 772篇 |
2013年 | 1047篇 |
2012年 | 1171篇 |
2011年 | 1210篇 |
2010年 | 861篇 |
2009年 | 804篇 |
2008年 | 882篇 |
2007年 | 845篇 |
2006年 | 777篇 |
2005年 | 612篇 |
2004年 | 448篇 |
2003年 | 365篇 |
2002年 | 338篇 |
2001年 | 291篇 |
2000年 | 260篇 |
1999年 | 285篇 |
1998年 | 267篇 |
1997年 | 195篇 |
1996年 | 222篇 |
1995年 | 220篇 |
1994年 | 196篇 |
1993年 | 165篇 |
1992年 | 134篇 |
1991年 | 148篇 |
1990年 | 150篇 |
1989年 | 114篇 |
1988年 | 94篇 |
1987年 | 79篇 |
1986年 | 62篇 |
1985年 | 63篇 |
1984年 | 28篇 |
1983年 | 36篇 |
1982年 | 28篇 |
1981年 | 20篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Assessment of Joule heating and its effects on electroosmotic flow and electrophoretic transport of solutes in microfluidic channels 总被引:4,自引:0,他引:4
Joule heating is inevitable when an electric field is applied across a conducting medium. It would impose limitations on the performance of electrokinetic microfluidic devices. This article presents a 3-D mathematical model for Joule heating and its effects on the EOF and electrophoretic transport of solutes in microfluidic channels. The governing equations were numerically solved using the finite-volume method. Experiments were carried out to investigate the Joule heating associated phenomena and to verify the numerical models. A rhodamine B-based thermometry technique was employed to measure the solution temperature distributions in microfluidic channels. The microparticle image velocimetry technique was used to measure the velocity profiles of EOF under the influence of Joule heating. The numerical solutions were compared with experimental results, and reasonable agreement was found. It is found that with the presence of Joule heating, the EOF velocity deviates from its normal "plug-like" profile. The numerical simulations show that Joule heating not only accelerates the sample transport but also distorts the shape of the sample band. 相似文献
992.
用X光衍射(XRD)方法研究了CrO_3/SiO_2和CrO_3/γ-Al_2O_3体系。用相定量外推法测定活性组份在载体表面的最大分散量。在干燥气氛中将CrO_3与载体混合, 并在低于CrO_3熔点的温度下烘烤制备样品, 实验得到CrO_3在SiO_2或者γ-Al_2O_3表面的最大分散量都随温度的升高而增大。CrO_3在SiO_2表面的最大分散量由101 ℃的0.27gCrO_3/g SiO_2到170 ℃的0.38g CrO_3/g SiO_2; CrO_3在γ-Al_2O_3表面的最大分散量由120 ℃的0.22g CrO_3/g γ-Al_2O_3到171 ℃的0.42g CrO_3/g γ-Al_2O_3。CrO_3在SiO_2或γ-Al_2O_3表面的最大分散量超过密置单层量, 可由易聚合形成同多酸根来解释。 相似文献
993.
994.
Subluminal to superluminal light propagation in a V-type three-level atomic system interacting with squeezed vacuum
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We study the light propagation properties in a V-type three-level atomic system interacting with two independent broadband squeezed baths. Using the graphic method, the dependences of the absorption and the dispersion of the system on the coupling field strength, the incoherent pumping field strength and the intensity of the squeezed vacuum are analysed. The result shows that the probe pulse propagation can be changed from subluminal to superluminal speed. 相似文献
995.
996.
997.
998.
GAO Bing-Shui ZHOU Xiao-Hong FANG Yong-De ZHANG Yu-Hu LIU Min-Liang WANG Si-Cheng WANG Jian-Guo MA Fei GUO Ying-Xiang WU Xiao-Guang HE Chuang-Ye ZHENG Yun WANG Zhi-Min YAN Xin-Liang WANG Zhi-Gang FANG Fang 《中国物理C(英文版)》2014,38(6):064001-064001
The neutron rich nucleus 193Os was produced in the 192Os(7Li, 6Li)193Os reaction. An isomeric state based on the 9/2-[505] Nilsson orbital was identified in the present work. The half-life of the isomeric state was extracted and discussed in terms of the K quantum number. A level scheme built on the isomeric state was proposed based on the experimental data. 相似文献
999.
文中用MNDO方法研究了三甲基膦和环氧乙烷加成产物裂解反应机理 相似文献
1000.
Chen R Wang L Xiong C Zhou Y Zhen C Zhang N Tang Y Zhou X Wang J Nie Z Chen Y 《The Analyst》2011,136(18):3809-3814
Electrosonic spray ionization (ESSI) is a derivative technique of electrospray ionization (ESI) for mass spectrometry (MS) in which droplets are charged in the course of sonic spray. In this study, we applied ESSI MS to direct analysis of oligosaccharides and alpha hydroxy acids (AHAs) in fruits. The components were extracted from fruit fleshes by a feasible method prior to ESSI MS analysis, but the fruit juices were analyzed without further pretreatment. The results demonstrate that mainly alkali metal adducts of oligosaccharides are favorably produced in positive ion mode, while deprotonated AHAs and oligosaccharides are produced in negative ion mode. Compared with mass spectra obtained using electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS), mass spectra using ESSI make the identification of oligosaccharides more straightforward in positive ion mode than in negative ion mode. 相似文献