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   2631篇
  免费   68篇
  国内免费   12篇
化学   1775篇
晶体学   43篇
力学   46篇
综合类   1篇
数学   106篇
物理学   740篇
  2022年   20篇
  2021年   17篇
  2020年   36篇
  2019年   31篇
  2018年   18篇
  2017年   23篇
  2016年   42篇
  2015年   52篇
  2014年   58篇
  2013年   134篇
  2012年   121篇
  2011年   172篇
  2010年   94篇
  2009年   83篇
  2008年   178篇
  2007年   174篇
  2006年   184篇
  2005年   172篇
  2004年   143篇
  2003年   133篇
  2002年   115篇
  2001年   46篇
  2000年   40篇
  1999年   28篇
  1998年   21篇
  1997年   24篇
  1996年   21篇
  1995年   27篇
  1994年   36篇
  1993年   27篇
  1992年   39篇
  1991年   12篇
  1990年   30篇
  1989年   31篇
  1988年   21篇
  1987年   14篇
  1986年   24篇
  1985年   31篇
  1984年   29篇
  1983年   17篇
  1982年   13篇
  1981年   24篇
  1980年   14篇
  1979年   21篇
  1978年   18篇
  1977年   15篇
  1976年   14篇
  1974年   13篇
  1973年   10篇
  1969年   11篇
排序方式: 共有2711条查询结果,搜索用时 15 毫秒
51.
52.
Quenching treatments were performed on CuCl microcrystallite-doped glasses prepared by a melting method. Radiative decay time measurement and χ(3) measurement for the quenched glasses were performed using ps and ns laser. The glasses showed that the radiative decay time were shortened by one order of magnitude without a decrease of third-order nonlinear susceptibility χ(3) after the quenching treatment from above 300°C. The distorted structure of CuCl microcrystallites quenched from high temperature was considered to be most effective for the shortening of the lifetime of Z3 exciton.  相似文献   
53.
Real forms of the quantum universal enveloping algebraU q (sl(2)) and a topological quantum group associated with this algebra are discussed.  相似文献   
54.
We present a study of the dijet invariant mass spectrum in events with two jets produced in association with a W boson in data corresponding to an integrated luminosity of 4.3 fb(-1) collected with the D0 detector at √s = 1.96 TeV. We find no evidence for anomalous resonant dijet production and derive upper limits on the production cross section of an anomalous dijet resonance recently reported by the CDF Collaboration, investigating the range of dijet invariant mass from 110 to 170 GeV/c(2). The probability of the D0 data being consistent with the presence of a dijet resonance with 4 pb production cross section at 145 GeV/c(2) is 8×10(-6).  相似文献   
55.
In this work we report the preparation of magnetic hematite hollow sub-micron spheres (??-Fe2O3) by colloidal suspensions of ferric nitrate nine-hydrate (Fe(NO3)3·9H2O) particles in citric acid solution by following the sol?Cgel method. After the gel formation, the samples were annealed at different temperatures in an oxidizing atmosphere. Annealing at 180°C resulted in an amorphous phase, without iron oxide formation. Annealing at 250°C resulted in coexisting phases of hematite, maghemite and magnetite, whereas at 400°C, only hematite and maghemite were found. Pure hematite hollow sub-micron spheres with porous shells were formed after annealing at 600°C. The characterization was performed by X-ray diffraction (XRD), Mössbauer spectroscopy (MS) and scanning electron microscopy (SEM).  相似文献   
56.
We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200 GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2相似文献   
57.
Pulsed EPR spectroscopy was employed to determine reaction rate constants at an early stage of addition reactions in radical polymerizations triggered by four initiator radicals, which were generated by photodissociation of four parent molecules. Two monomers (tert‐butylacrylate and tert‐butylmethacrylate) were examined as reactant. Stern–Volmer analysis on the measured decay time of electron spin echo intensity of reacting radicals provides rate constants for addition reactions. We focused on rate constants for the second step reaction between monomer and adduct radical that is produced by the first step addition reaction between initiator radical and monomer. The rate constant measured by pulsed EPR was evaluated by theoretical calculations in the light of (1) enthalpy difference between product radical and reactants and (2) charge transfer interaction between reacting radical and monomer. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
58.
Using Monte Carlo simulation, we have compared the magnetic properties between nanostructured thin films and two-dimensional crystalline solids. The dependence of nanostructured properties on the interaction between particles that constitute the nanostructured thin films is also studied. The result shows that the parameters in the interaction potential have an important effect on the properties of nanostructured thin films at the transition temperatures.  相似文献   
59.
Phase adjustment elements called islands and peninsulas are introduced to obtain an AWG demultiplexer with a flat spectral response. Use of the peninsulas enables us to achieve a 1dB bandwidth of 0.5 nm.  相似文献   
60.
This paper reviews recent theoretical and experimental studies on optical amplification by stimulated Raman scattering (Raman amplification) in single-mode optical fibres, and discusses its possible applications to long-distance optical communications. The fibre Raman amplifier can be used as an in-line optical amplifier in both repeaterless and non-regenerative all-optical repeater configurations. In the former application, signal transmission of over 400 km has been predicted theoretically, although high-power pump sources are considered to be required. In the latter configuration, in which optical fibre losses are compensated for by Raman gains, it has been shown that extremely long-distance transmission over more than 1000 km is feasible in terms of signal-to-noise ratio, where the distance achievable is mainly limited by the accumulation of Raman noise. Recent experimental demonstrations including bit-error rate measurements on the Raman amplified signal, and laser-diode pumped amplification, etc., are also reviewed. The results confirm the effectiveness of fibre Raman amplifiers in future long-haul systems.  相似文献   
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