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   422篇
  免费   29篇
  国内免费   2篇
化学   235篇
晶体学   7篇
力学   58篇
综合类   2篇
数学   42篇
物理学   109篇
  2023年   5篇
  2022年   12篇
  2021年   9篇
  2020年   17篇
  2019年   10篇
  2018年   10篇
  2017年   9篇
  2016年   13篇
  2015年   21篇
  2014年   20篇
  2013年   30篇
  2012年   23篇
  2011年   45篇
  2010年   17篇
  2009年   17篇
  2008年   21篇
  2007年   20篇
  2006年   16篇
  2005年   23篇
  2004年   10篇
  2003年   8篇
  2002年   4篇
  2001年   4篇
  2000年   8篇
  1999年   4篇
  1998年   4篇
  1996年   4篇
  1995年   5篇
  1994年   3篇
  1993年   4篇
  1992年   3篇
  1991年   4篇
  1990年   4篇
  1989年   3篇
  1986年   2篇
  1985年   3篇
  1984年   3篇
  1983年   3篇
  1981年   2篇
  1980年   2篇
  1977年   2篇
  1976年   3篇
  1975年   3篇
  1974年   5篇
  1973年   5篇
  1972年   1篇
  1970年   1篇
  1969年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有453条查询结果,搜索用时 93 毫秒
431.
In this article, we proposed a new scheme to encrypt highly autocorrelated image pixel data. In existing literature, single substitution was used to break autocorrelation in images. To get better results, instead of single substitution box, some researchers are minimizing the autocorrelation via utilizing multiple substitution boxes. However, we found that multiple substitution boxes cannot solve the problem of autocorrelation independently. Therefore, we added chaotic confusion and diffusion to the existing substitution scheme in order to remove the correlation completely. Initially, we break the autocorrelation of data by permuting the pixels via TD-ERCS chaotic map. Bitwise XOR is carried out for diffusion using logistic map followed by the existing substitution scheme. Experimental analysis shows that the proposed scheme has greater resistance to brute force attack and statistical attack. Further analyses such as statistical analysis, peak signal-to-noise ratio, contrast analysis, key space analysis, entropy analysis, correlation analysis, key sensitivity analysis, and encryption quality analysis proved the high robustness of the proposed scheme.  相似文献   
432.
In this article, the solution of the time-fractional Phi-4 equation is investigated. We implement the residual power series method to approximate the solution of this equation. Numerical results are presented. In addition, the effects of the fractional order on the Phi-4 are discussed graphically.  相似文献   
433.
Experiment 865 at the Brookhaven Alternating Gradient Synchrotron obtained 410 K+-->e(+)nue(+)e(-) and 2679 K+-->mu(+)nue(+)e(-) events including 10% and 19% background. The branching ratios were measured to be [2.48+/-0.14(stat)+/-0.14(syst)]x10(-8) (m(ee)>150 MeV) and (7.06+/-0.16+/-0.26)x10(-8) (m(ee)>145 MeV), respectively. Results for the decay form factors are presented.  相似文献   
434.
The problem concerning the explosion of a cord charge in the ground, with a hard upper layer, is considered in pulse formulation. A numerical solution is obtained and profiles are given for the throwout craters for several values of thickness of the layer and emplacement depth of the charge, in two limiting cases: when the resistance of the lower ground is negligibly small in comparison with the resistance of the layer and when the resistance of the ground and layer are quite close in magnitude.Translated from Zhurnal Prikladnoi Mekhanika i Tekhnicheskoi Fiziki, No. 2, pp. 143–146, March–April, 1973.  相似文献   
435.
436.
Ramosine, a new sesquiterpene lactone, was isolated from the chloroform fraction of Amberboa ramosa and the structure was assigned as 4beta-(hydroxymethyl)-3beta,4alpha-dihydroxy-8alpha-[(S)-3-hydroxy-2-ethylenepropionyloxy]-1alphaH, 5alphaH,6betaH,7alphaH,11betaH,11alpha-methylguaia-10(14)-en-6, 12-olide by extensive NMR studies.  相似文献   
437.
Book review     
  相似文献   
438.
More than 400 K+-->pi(+)&mgr;(+)&mgr;(-) events were observed in a rare K+ decay experiment at the Brookhaven Alternating Gradient Synchrotron. Normalized to the K+-->pi(+)pi(+)pi(-) decay, the branching ratio is determined to be [9.22+/-0.60(stat)+/-0. 49(syst)]x10(-8). This branching ratio and the &mgr;&mgr; mass spectrum is in very good agreement with the measurement of the K+-->pi(+)e(+)e(-) decay, but deviates significantly from the previous measurement.  相似文献   
439.
Peculiar features of the self-action of non-one-dimensional wave packets described by the nonlinear Schrodinger equation with a hyperbolic spatial operator were studied analytically and numerically. It was shown that the self-action dynamics is determined by the consequence of the processes of transverse self-focusing filamentation and longitudinal splitting. Splitting scenarios were classified. It is shown that the strongest inhomogeneities are excited along "hyperbolas" in the self-similar collapse process.  相似文献   
440.
Dihydromyricetin-mediated silver nanoparticles (DMY-AgNPs) were synthesized and their efficacy against fungal pathogens tested in vitro. The shape of DMY-AgNPs appeared to be spherical with size of ~34 nm. Fourier-transform infrared (FT-IR) analysis indicated that –OH and C=O groups were involved in nanoparticle formation. The XRD pattern of DMY-AgNPs showed strong peaks at 38°, 44°, and 64°, corresponding to reflection from (111), (200), and (220) planes. Five opportunistic fungal pathogens, namely Aspergillus fumigatus, Aspergillus niger, Paecilomyces formosus, Candida albicans, and Candida parapsilosis, were isolated from patients suffering from respiratory tract infections. Growth of each fungal strain was inhibited by DMY-AgNPs. The zone of inhibition of DMY-AgNPs against A. fumigatus, A. niger, P. formosus, C. albicans, and C. parapsilosis was 17.6, 19.2, 22.2, 15.8, and 18.5 mm. The minimal inhibitory concentration was found to be 0.83, 0.73, 0.67, 0.95, and 0.89 µg mL?1, respectively. This is the first report on DMY-AgNPs as an effective antifungal agent. DMY-AgNPs are a potential alternative to commercially available antifungal fungicidals.  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