全文获取类型
收费全文 | 7238篇 |
免费 | 972篇 |
国内免费 | 718篇 |
专业分类
化学 | 2521篇 |
晶体学 | 114篇 |
力学 | 974篇 |
综合类 | 170篇 |
数学 | 2351篇 |
物理学 | 2798篇 |
出版年
2024年 | 14篇 |
2023年 | 71篇 |
2022年 | 209篇 |
2021年 | 223篇 |
2020年 | 225篇 |
2019年 | 187篇 |
2018年 | 196篇 |
2017年 | 280篇 |
2016年 | 303篇 |
2015年 | 257篇 |
2014年 | 398篇 |
2013年 | 615篇 |
2012年 | 396篇 |
2011年 | 452篇 |
2010年 | 363篇 |
2009年 | 467篇 |
2008年 | 470篇 |
2007年 | 445篇 |
2006年 | 437篇 |
2005年 | 376篇 |
2004年 | 291篇 |
2003年 | 300篇 |
2002年 | 240篇 |
2001年 | 222篇 |
2000年 | 220篇 |
1999年 | 182篇 |
1998年 | 148篇 |
1997年 | 147篇 |
1996年 | 134篇 |
1995年 | 135篇 |
1994年 | 75篇 |
1993年 | 71篇 |
1992年 | 58篇 |
1991年 | 42篇 |
1990年 | 50篇 |
1989年 | 40篇 |
1988年 | 37篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 27篇 |
1983年 | 6篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1979年 | 8篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有8928条查询结果,搜索用时 15 毫秒
71.
Huang H. X. Liang Z. A. Pardalos P. M. 《Journal of Optimization Theory and Applications》2004,120(1):53-71
A flow search approach is presented in this paper. In the approach, each iterative process involves a subproblem, whose variables are the stepsize parameters. Every feasible solution of the subproblem corresponds to some serial search stages, the stepsize parameters in different search stages may interact mutually, and their optimal values are determined by evaluating the total effect of the interaction. The main idea of the flow search approach is illustrated via the minimization of a convex quadratic function. Based on the flow search approach, some properties of the m-step linear conjugate gradient algorithm are analyzed and new bounds on its convergence rate are also presented. Theoretical and numerical results indicate that the new bounds are better than the well-known ones. 相似文献
72.
P. Cicman M. Francis J.D. Skalny S. Matejcik T.D. Märk 《Czechoslovak Journal of Physics》2003,53(3):181-190
The rate constant for dissociative electron attachment to ozone has been derived over the energy range from about 0 to 10 eV using recently measured and also corrected cross section data. The new rate constant data sets for two partial dissociative channels, as well as for the total dissociative electron attachment, are compared with previously reported values, and existing discrepancies are discussed. 相似文献
73.
74.
Summary An analysis of five different datasets of inhibitors of serotonin uptake has yielded quantitative structure/ activity relationships (QSARs) which delineate the role of steric and hydrophobic properties essential for inhibition by phenylethylamine-type analogues. 相似文献
75.
76.
Seiya Uyeda Atsumi Kumamoto 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(3):140
Kushida and Kushida found that FM radio waves from stations at distances over-the-horizon are received before earthquakes. Based on this finding, since the mid-1990’s, the Kushidas have been practicing “Earthquake Precursor Detection Experiment”. The performance of the Kushida method during 2000–2003 has been evaluated by checking their predictions against the actual seismicity. During the period, there were 92 Kushida predictions mentioning the possibility of M ≥ 5.5 event, whereas there were 49 M ≥ 5.5 earthquakes in the Japanese region. If the criteria for successful prediction are set as: the errors in date is less than one day, epicentral position is roughly within specified area, and error in M is less than 0.5, the success rate was 20% and the alarm rate was 12%. If we relax the criteria to: the errors in dates within 10 days, epicenter within additional 100 km of specified area and the magnitude error less than 1.0, the success rate was 40% and the alarm rate was 27%. These rates may look insufficient for a practical prediction method. Considering, however, the fact that no other short-term prediction has ever been made in Japan so far it is a significant achievement. Moreover, it was found that in almost all failed predictions, meaningful signals were detected although the interpretations were incorrect. This indicates that the method is promising provided further investigation is carried out. The same evaluation at the M ≥ 6.0 level showed that the general performance was similar to the M ≥ 5.5 level, except that both success rate and alarm rate were lower at the M ≥ 6.0 level. If this unexpected finding is real, it might be inherent to the methodology using scattering of short-wave length radio waves as suggested by M. Hayakawa and may contain important information in understanding the earthquake physics and LAI-coupling. The results of the present study indicate strongly that the earthquake prediction research using anomalous transmission of VHF FM radio waves should be enhanced in parallel with complementary research in other frequency ranges. 相似文献
77.
Da-Zhi Li Li Gan Zi-Qiang Yang Zheng Liang Jia-Yin Li 《International Journal of Infrared and Millimeter Waves》1997,18(10):1885-1896
The dispersion characteristic of the plasma-loaded relativistic backward wave oscillator has been analyzed. The theoretical
model has been established and the numerical calculations accord with the experimental results, which provides some useful
suggestions on the designing of slow-wave structure of BWO. 相似文献
78.
林支桂 《数学物理学报(B辑英文版)》1998,(3)
1IntroductionInthispaper,weconsidertheinitial-boundaryvalueproblem,where"o(x)isnon-negativesmoothfunctionsatisfying"o.(0)=0,"o.(1)=1'Whenconsideringtheblow-upofsolution,thefollowingproblemarisenaturally:Doesblow-upoccur?Howdoesthesolutionapproachtheblow-uptime'!Andwilersisthehotspotlocated(blow-upset)?WelookattheheatequationwithanonlillearboundaryconditiollHerefiisaboundeddomaininR",p>1isarealnumber.IthasbeenknownforalongtimethattheDroblelil(1.1).(1.2)withAL(~,0)--'no(x)doesnothaveaglobals… 相似文献
79.
一类时变需求且存货影响销售率的EOQ模型 总被引:3,自引:0,他引:3
从实际背景出发,在R AM P型需求和存货影响销售率条件下,讨论了一类以缺货开始的变质性物品的EOQ模型.给出了模型的求解方案及单位时间内平均利润最大化的两个充分条件,并用数值算例进行了验证. 相似文献
80.