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   2547篇
  免费   60篇
  国内免费   3篇
化学   1801篇
晶体学   46篇
力学   107篇
数学   190篇
物理学   466篇
  2024年   13篇
  2023年   26篇
  2022年   52篇
  2021年   64篇
  2020年   71篇
  2019年   99篇
  2018年   75篇
  2017年   70篇
  2016年   82篇
  2015年   61篇
  2014年   83篇
  2013年   204篇
  2012年   167篇
  2011年   184篇
  2010年   94篇
  2009年   83篇
  2008年   122篇
  2007年   111篇
  2006年   99篇
  2005年   90篇
  2004年   110篇
  2003年   55篇
  2002年   41篇
  2001年   24篇
  2000年   19篇
  1999年   27篇
  1998年   12篇
  1997年   14篇
  1996年   15篇
  1995年   19篇
  1994年   16篇
  1993年   19篇
  1992年   18篇
  1990年   14篇
  1989年   20篇
  1988年   14篇
  1987年   14篇
  1986年   14篇
  1985年   13篇
  1984年   16篇
  1983年   18篇
  1982年   13篇
  1981年   12篇
  1980年   27篇
  1979年   12篇
  1978年   14篇
  1977年   24篇
  1976年   14篇
  1975年   12篇
  1973年   13篇
排序方式: 共有2610条查询结果,搜索用时 0 毫秒
31.
Calculations of the Dynamic Deformation Model for the E2/M1 mixing ratios for ψ-band to ground-band transitions in166Er have been extended to higher spins (up to I=20). Previous comparisons with the experimental values and with the IBA-1 predictions, available at present up to spins 8 only, are also included for the sake of completeness. Additional comparison with the Frankfurt Model is also given. While all three models give reasonable magnitudes of the mixing ratios, only the DDM gives the sign changes at the correct spin values. Predictions are presented for additional sign changes of the mixing ratios, as well as those of the E2 and the M1 transition moments.  相似文献   
32.
The Measurement of K β K /α intensity ratios are measured in some 3d shell elements by using a 2 MeV proton beam along with a high resolution Si(Li) detector. The present Measurement of K β K /α intensity ratios are in good agreement with Scofield modified theoretical values, thus supporting the basic assumptions in that theory. From the present Measurement of K β K /α intensity ratios, it is evident that due to chemical effects, the experimental Measurement of K β K /α intensity ratios will be increased while they will be decreased due to the presence of simultaneous M-shell vacancies which are produced due to proton excitation.  相似文献   
33.
34.
The present work reports a simple approach for fabrication of self‐standing titania (TiO2) nanotube membranes with through‐hole morphology. The method is hydrofluoric acid free and the pore opening of TiO2 nanotubes is performed by electrochemical thinning of the oxide barrier layer. A reduction of anodization voltage was applied at the end of the anodization process to cause a successful removal of the remaining barrier layer from the TiO2 nanotubes during their detachment from the underlying titanium substrate. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
35.
A modified two-aperture speckle shear interferometer that eliminates the contribution of the in-plane component and its derivative to the phase change, and yields a fringe pattern corresponding to the first-order partial derivatives of the out-of-plane displacement component, is reported in this note. In this method, two laterally sheared object points are viewed axially. The wave fields from these points are independently combined at the image plane of the imaging system.  相似文献   
36.
We demonstrate a technique to measure hyperfine structure using a frequency-stabilized diode laser and an acousto-optic modulator locked to the frequency difference between two hyperfine peaks. We use this technique to measure hyperfine intervals in the 5 P 3/2 state of 85Rb and obtain a precision of 20 kHz. We extract values for the magnetic-dipole coupling constant A = 25.038(5) MHz and the electric-quadrupole coupling constant B = 26.011(22) MHz. These values are a significant improvement over previous results. Received 6 March 2003 Published online 15 April 2003  相似文献   
37.
We report a technique that is capable of making simultaneous two-point time-series measurements of minor-species concentrations in turbulent flames. The experimental setup, which incorporates picosecond time-resolved laser-induced fluorescence, has a spatial resolution of less than 250 microm and a temporal resolution of less than 100 micros, which spatially and temporally resolve microscales in many turbulent flows. Two-point time-series data are given for a standard turbulent nonpremixed flame at Re= 10,000, including a discussion of potential implications.  相似文献   
38.
P Riesz  T Kondo  C M Krishna 《Ultrasonics》1990,28(5):295-303
Recent spin trapping studies of the free radical intermediates generated by the sonolysis of aqueous solutions are reviewed. Studies of rare gas saturated solutions of volatile solutes (e.g., methanol and ethanol) and of non-volatile solutes (acetate, amino acids, sugars, pyrimidines, nucleotides and surfactants) are consistent with the theory of three reaction zones in aqueous sonochemistry. The very high temperatures and pressures induced by acoustic cavitation in collapsing gas bubbles in aqueous solutions lead to the thermal dissociation of water vapour into hydrogen atoms and hydroxyl radicals. Reactions take place in the gas phase (pyrolysis reactions), in the region of the gas-liquid interface, and in the bulk of the solution at ambient temperature (similar to radiation chemistry reactions). By use of the rare gases with different thermal conductivities, the contributions of individual reaction steps with widely different energies of activation can be evaluated.  相似文献   
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