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   693篇
  免费   11篇
  国内免费   1篇
化学   493篇
晶体学   7篇
力学   29篇
数学   20篇
物理学   156篇
  2022年   4篇
  2021年   6篇
  2020年   5篇
  2019年   10篇
  2018年   5篇
  2016年   9篇
  2015年   8篇
  2014年   12篇
  2013年   35篇
  2012年   18篇
  2011年   32篇
  2010年   17篇
  2009年   14篇
  2008年   36篇
  2007年   21篇
  2006年   32篇
  2005年   36篇
  2004年   17篇
  2003年   23篇
  2002年   22篇
  2001年   10篇
  2000年   15篇
  1999年   8篇
  1998年   4篇
  1997年   8篇
  1996年   11篇
  1995年   4篇
  1993年   7篇
  1992年   9篇
  1991年   7篇
  1990年   6篇
  1989年   6篇
  1988年   4篇
  1986年   8篇
  1985年   17篇
  1984年   22篇
  1983年   12篇
  1982年   18篇
  1981年   26篇
  1980年   21篇
  1979年   17篇
  1978年   14篇
  1977年   11篇
  1976年   11篇
  1975年   10篇
  1974年   12篇
  1973年   11篇
  1972年   7篇
  1971年   3篇
  1968年   3篇
排序方式: 共有705条查询结果,搜索用时 514 毫秒
1.
This paper reports a successful achievement of laser-induced biological cell fusion using an excimer laser excited dye laser. To our knowledge, we examined for the first time the dependence of fusion rate on laser pulse energy, number of laser pulses, and laser wavelength. Maximum fusion rate of approximately 50% was obtained by this laser fusion technology.  相似文献   
2.
3.
4.
The educational system has gradually shifted from a face-to-face to an e-learning system, which has become prevalent in advanced countries with the advance of information technology, and connection of global networks. Accordingly, a growing demand is emerging for more reliable individual certification with technical precision in order to measure and record learning achievements and credentials of participants. The present system has a limit in terms of registration capacity, therefore, its accuracy has often been questioned. Against this background, an individual certification system is proposed particularly for access control in e-learning. Under our proposed system, a compact optical correlator for facial recognition is employed. This correlator was previously tested for of biometrics authentication accuracy and proved highly reliable, having recorded remarkably low error rates (below 1%). The recorded error rate is sufficiently robust that the system itself can be regarded as a valid and practical viable attestation system.  相似文献   
5.
The drying conditions for primary standards of volumetric analysis have a significant effect on the titration results due to changes in the purity, stability and homogeneity. Amidosulfuric acid, a strong acid used as a reference material for volumetric analysis in Japan, was dried in a vacuum desiccator or heated at different temperatures, and then measured by Karl-Fischer titration, thermogravimetry/mass spectroscopy (TG-MS), ion chromatography and coulometric titration. The optimum drying conditions were at 50 degrees C for 24 h with crushing.  相似文献   
6.
In this paper, we discuss two key aspects of magnetisation reversal in magnetic thin films with perpendicular anisotropy. Firstly, a study has been made of the additional field required to erase data written perpendicular to a thin film recording disk as the linear data density is increased. It has been found that an increase in data density from 40 to 360 kfci results in an increase of 1.25 kOe in the field required to erase the data. Secondly, the effect of varying the level of exchange coupling by co-sputtering CoCrPt samples with SiO2 has been studied using a characterisation technique that is independent of the self-demagnetising field. It has been found that the samples are fully exchange de-coupled when the film contains >9.8% SiO2 and the activation volume of reversal remains constant for higher levels of SiO2.  相似文献   
7.
8.
Infrared and Raman spectra of 1,2-dibromoethane CH2BrCH2Br and CD2BrCD2Br were observed in the liquid state, and the fundamental frequencies were determined by comparison with those of related molecules. Infrared absorption intensities of fundament bands were measured in the liquid state, and the intensity data were interpreted on the basis of the valence-optical theory. From the converged value of a population ratio, the energy difference between the trans and gauche isomers was determined, which was in good agreement with the value obtained from the temperature effect of the IR spectrum.  相似文献   
9.
Treatment of alkyl allyl carbonates derived from various alcohols with a palladium catalyst in MeCN affords ketones and aldehydes in high yields. This new method of oxidation of alcohols can be applied to various alcohols except simple primary alcohols.  相似文献   
10.
Isotropie Raman spectra of the symmetric C—H stretching bands of several organic molecules are measured in the neat liquid and in solvents including water. The linewidths are interpreted on the basis of the vibrational dephasing model, and intermolecular interactions between the solutes and solvents are discussed.  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