全文获取类型
收费全文 | 1528篇 |
免费 | 32篇 |
国内免费 | 5篇 |
专业分类
化学 | 1143篇 |
晶体学 | 15篇 |
力学 | 33篇 |
数学 | 142篇 |
物理学 | 232篇 |
出版年
2023年 | 11篇 |
2022年 | 57篇 |
2021年 | 58篇 |
2020年 | 45篇 |
2019年 | 32篇 |
2018年 | 30篇 |
2017年 | 23篇 |
2016年 | 50篇 |
2015年 | 57篇 |
2014年 | 53篇 |
2013年 | 105篇 |
2012年 | 121篇 |
2011年 | 115篇 |
2010年 | 60篇 |
2009年 | 81篇 |
2008年 | 107篇 |
2007年 | 89篇 |
2006年 | 72篇 |
2005年 | 51篇 |
2004年 | 63篇 |
2003年 | 47篇 |
2002年 | 41篇 |
2001年 | 24篇 |
2000年 | 27篇 |
1999年 | 19篇 |
1998年 | 9篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1985年 | 9篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1948年 | 1篇 |
1938年 | 1篇 |
1934年 | 2篇 |
1925年 | 2篇 |
1924年 | 2篇 |
排序方式: 共有1565条查询结果,搜索用时 15 毫秒
81.
Graeme Kemkes Cristiane M. Sato Nicholas Wormald 《Random Structures and Algorithms》2013,43(3):354-376
We determine an asymptotic formula for the number of labelled 2‐connected (simple) graphs on n vertices and m edges, provided that m ‐ n →∞ and m = O(nlog n) as n →∞. This is the entire range of m not covered by previous results. The proof involves determining properties of the core and kernel of random graphs with minimum degree at least 2. The case of 2‐edge‐connectedness is treated similarly. We also obtain formulae for the number of 2‐connected graphs with given degree sequence for most (“typical”) sequences. Our main result solves a problem of Wright from 1983. © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 2013 相似文献
82.
A.S. Maciel J.V. Araújo A.K. Campos L.A. Benjamin L.G. Freitas 《Micron (Oxford, England : 1993)》2009,40(4):463-470
The interaction between the nematode-trapping fungus Duddingtonia flagrans (isolate CG768) against Ancylostoma spp. dog infective larvae (L3) was evaluated by means of scanning electron microscopy. Adhesive network trap formation was observed 6 h after the beginning of the interaction, and the capture of Ancylostoma spp. L3 was observed 8 h after the inoculation these larvae on the cellulose membranes colonized by the fungus. Scanning electron micrographs were taken at 0, 12, 24, 36 and 48 h, where 0 is the time when Ancylostoma spp. L3 was first captured by the fungus. Details of the capture structure formed by the fungus were described. Nematophagous Fungus Helper Bacteria (NHB) were found at interactions points between the D. flagrans and Ancylostoma spp. L3. The cuticle penetration by the differentiated fungal hyphae with the exit of nematode internal contents was observed 36 h after the capture. Ancylostoma spp. L3 were completely destroyed after 48 h of interaction with the fungus. The scanning electron microscopy technique was efficient on the study of this interaction, showing that the nematode-trapping fungus D. flagrans (isolate CG768) is a potential exterminator of Ancylostoma spp. L3. 相似文献
83.
Diogo de Andrade Nuno Fachada Carlos M. Fernandes Agostinho C. Rosa 《Entropy (Basel, Switzerland)》2020,22(11)
We present a generative swarm art project that creates 3D animations by running a Particle Swarm Optimization algorithm over synthetic landscapes produced by an objective function. Different kinds of functions are explored, including mathematical expressions, Perlin noise-based terrain, and several image-based procedures. A method for displaying the particle swarm exploring the search space in aesthetically pleasing ways is described. Several experiments are detailed and analyzed and a number of interesting visual artifacts are highlighted. 相似文献
84.
Sylvio Barbon Jr. Rodrigo Capobianco Guido Lucimar Sasso Vieira Everthon Silva Fonseca Fabrício Lopes Sanchez Paulo Rogério Scalassara Carlos Dias Maciel José Carlos Pereira Shi-Huang Chen 《Journal of Computational and Applied Mathematics》2009
Dynamic Time Warping (DTW), a pattern matching technique traditionally used for restricted vocabulary speech recognition, is based on a temporal alignment of the input signal with the template models. The principal drawback of DTW is its high computational cost as the lengths of the signals increase. This paper shows extended results over our previously published conference paper, which introduces an optimized version of the DTW that is based on the Discrete Wavelet Transform (DWT). 相似文献
85.
Soderstrom E McKenna JA Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R 《Physical review letters》1990,64(25):2980-2983
86.
We report numerical results on the existence of periodic structures embedded in chaotic and hyperchaotic regions on the Lyapunov exponent diagrams of a 4-dimensional Chua system. The model was obtained from the 3-dimensional Chua system by the introduction of a feedback controller. Both the largest and the second largest Lyapunov exponents were considered in our colorful Lyapunov exponent diagrams, and allowed us to characterize periodic structures and regions of chaos and hyperchaos. The shrimp-shaped periodic structures appear to be malformed on some of Lyapunov exponent diagrams, and they present two different bifurcation scenarios to chaos when passing the boundaries of itself, namely via period-doubling and crisis. Hyperchaos-chaos transition can also be observed on the Lyapunov exponent diagrams for the second largest exponent. 相似文献
87.
Optimized HR-AR-DFB laser structures are proposed foreseeing their use in directly modulated optical communication systems. They present, simultaneously, high single-longitudinal-mode yield, stable single-longitudinal-mode operation, high power efficiency and stable emitted wavelength. Lasers harder to manufacture were previously proposed elsewhere and did not succeed in achieving such high performances. A detailed assessment of the proposed lasers is presented and discussed. 相似文献
88.
89.
This paper presents a method for the determination of phenylephrine hydrochloride in pharmaceuticals by spectrophotometric flow injection analysis exploiting the reaction with potassium ferricyanide and 4-aminoantipyrine, which leads to the formation of a condensation product with strong absorptivity at 500 nm. The linear dynamic range was between 0.95 and 9 mg/L, with a limit of detection of 0.2 mg/L and a sampling throughput of 120 samples per hour. The method was applied to eyewashes and nasal decongestant liquid medicines. 相似文献
90.