首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1219篇
  免费   18篇
  国内免费   3篇
化学   591篇
晶体学   18篇
力学   61篇
数学   108篇
物理学   462篇
  2022年   16篇
  2021年   10篇
  2020年   19篇
  2019年   25篇
  2018年   16篇
  2017年   24篇
  2016年   41篇
  2015年   19篇
  2014年   34篇
  2013年   56篇
  2012年   73篇
  2011年   78篇
  2010年   61篇
  2009年   41篇
  2008年   72篇
  2007年   73篇
  2006年   57篇
  2005年   46篇
  2004年   35篇
  2003年   37篇
  2002年   32篇
  2001年   20篇
  2000年   23篇
  1999年   11篇
  1998年   17篇
  1997年   15篇
  1996年   17篇
  1995年   14篇
  1994年   13篇
  1993年   19篇
  1992年   11篇
  1991年   5篇
  1990年   11篇
  1989年   18篇
  1988年   6篇
  1987年   19篇
  1986年   7篇
  1985年   14篇
  1984年   12篇
  1983年   13篇
  1982年   13篇
  1981年   10篇
  1980年   11篇
  1979年   7篇
  1978年   7篇
  1977年   5篇
  1975年   4篇
  1972年   4篇
  1960年   4篇
  1954年   5篇
排序方式: 共有1240条查询结果,搜索用时 13 毫秒
31.
The electrical, structural, and photoelectrochemical properties of the polymer electrolyte PEO:NaI/I2 doped with an ionic liquid 1-ethyl 3-methylimidazolium dicyanamide (EMImDCN) have been reported. Incorporation of the ionic liquid (IL) increases the membrane homogeneity, decreased surface roughness, and enhances the short current (J sc). Additionally, the doping of IL provides more charge carriers which enhances overall ionic conductivity (σ). The optimized σ was found at 40 wt.% IL composition. The fabricated DSSC using this new solid electrolyte showed 1.43% efficiency at 100 mW cm−2.  相似文献   
32.
Radio wave operating in millimetrewave and microwave frequency bands are adversely affected due to rain. Particularly the attenuation is of immense significance for sensitive remote measurements by satellites using frequencies greater than 10 GHz. Maintenance of an uninterrupted communication link requires a precise knowledge of the attenuation effect due to rain for commissioning right kind of transmitting sources for various purposes required in present day situation. Precise measurement of attenuation at various frequencies will enable us to choose the right frequency, polarization, incident angle and power of the source for different purposes. In this paper we have compared the results of earlier works using aRb Olsen et al, (1) and the formulation by Moupfouma, (2) on the basis of theoretical analysis for explaining the observed results. Effect of temperature, considered in detail in this communication, has contributed the necessary correction factor of the rain attenuation for explaining the observed results. Theoretical analyses to measure the attenuation of the propagating wave due to temperature variation in the rain path have been presented. Correction factor due to temperature profile (temperature from the ground to the rain height within which the radio wave traces its path) has been incorporated in two models by using the concept of dipole energy changes. The effect of this temperature is noted to be quite significant and incorporates an error to the extent of 7–8%.  相似文献   
33.
Observation of phonon bottleneck in quantum dot electronic relaxation   总被引:3,自引:0,他引:3  
Time-resolved differential transmission measurements of self-assembled In0.4Ga0.6As quantum dots clearly indicate a phonon bottleneck between the n = 2 and n = 1 electronic levels. The key to this observation is the generation of electrons in dots where there are no holes so that electron-hole scattering does not mask the bottleneck. We use a simple carrier capture model consisting of two capture configurations to explain the bottleneck signal and offer arguments to rule out other possible sources of the signal.  相似文献   
34.
An interferometric method for the measurement of parallelism of the end faces of a transparent material is described. It is based on the measurement of fringe displacement caused by the wedge angle of the material by using the Lau effect.  相似文献   
35.
A kinematically complete experiment has been performed to study the α-n final-state interaction (FSI) in the α + d ↦α + p + n break-up reaction at 50 MeV incident energy for the alpha-particles. For this, we have chosen four pairs of correlation angles for the outgoing alpha and protons. These are ( θα = 18°, θp = 42°), ( θα = 20°, θp = 45°), ( θα = 22°, θp = 42°) and ( θα = 22°, θp = 47°), selected kinematically where the allowed phase spaces are in favor of the α-n final-state interaction. Our experimental data show strong α-n FSI in all the selected configurations. Also, the FSI is found to be stronger at the lower alpha-particle energy when two FSI peaks appear in the same configuration. Received: 17 June 2002 / Accepted: 3 October 2002 / Published online: 4 February 2003 RID="a" ID="a"e-mail: dey_s2001@yahoo.com; Present address: 445 Waupelani Drive, Apt. F3, State College, PA 16801, USA. Communicated by M. Gar?on  相似文献   
36.
Using the pseudopotential method, theoretical investigation has been made on the firstorder Korteweg-deVries ion-acoustic solitons in a multicomponent plasma consisting of warm positive ions, negative ions and isothermal electrons. The effects of electron-inertia and drift motion of the ions on the amplitudes and widths of the solitons have been studied in a plasma having (H+, Cl), (H+, O), (He+, H) and (He+, O) ions. Ion-acoustic double-layers have also been investigated for such plasmas. It has been found that drift velocity and electron-inertia have significant contribution on the formation of double-layers in multicomponent plasma  相似文献   
37.
It is shown, using an effective theory, that the electric charge that develops on a magnetic monopole, due to the presence of the CP-violating term \([\theta e^2 /(32\pi ^2 )]F_{\mu v}^a \tilde F^{\mu va} \) , does not vanish for massless fermions.  相似文献   
38.
39.
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号