全文获取类型
收费全文 | 942篇 |
免费 | 9篇 |
国内免费 | 7篇 |
专业分类
化学 | 562篇 |
晶体学 | 9篇 |
力学 | 34篇 |
数学 | 82篇 |
物理学 | 271篇 |
出版年
2021年 | 13篇 |
2020年 | 19篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2014年 | 7篇 |
2013年 | 42篇 |
2012年 | 33篇 |
2011年 | 41篇 |
2010年 | 15篇 |
2009年 | 26篇 |
2008年 | 33篇 |
2007年 | 38篇 |
2006年 | 41篇 |
2005年 | 28篇 |
2004年 | 29篇 |
2003年 | 34篇 |
2002年 | 19篇 |
2001年 | 19篇 |
2000年 | 38篇 |
1999年 | 16篇 |
1998年 | 19篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 20篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 6篇 |
1977年 | 22篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1970年 | 5篇 |
1917年 | 7篇 |
排序方式: 共有958条查询结果,搜索用时 15 毫秒
71.
B. B. Bhattacharyya X. Li M. Pensky G. D. Richardson 《Annals of the Institute of Statistical Mathematics》2000,52(1):71-83
The limiting distribution of the normalized periodogram ordinate is used to test for unit roots in the first-order autoregressive model st= s-1,t+s,t-1- s-1,t-1+st. Moreover, for the sequence
n
= e
c/n
,
n
= e
d/n
of local Pitman-type alternatives, the limiting distribution of the normalized periodogram ordinate is shown to be a linear combination of two independent chi-square random variables whose coefficients depend on c and d. This result is used to tabulate the asymptotic power of a test for various values of c and d. A comparison is made between the periodogram test and a spatial domain test. 相似文献
72.
Fera A Dolbnya IP Grubel G Muller HG Ostrovskii BI Shalaginov AN de Jeu WH 《Physical review letters》2000,85(11):2316-2319
Coherent dynamic x-ray scattering has been used to study the thermally excited layer fluctuations in freely suspended smectic films of the compound 4O.8. Using 8-keV x rays and films with a thickness around 0.3 &mgr;m we resolve relaxation times down to a few &mgr;s. A combination of damped and oscillatory behavior is observed for the layer undulations, which can be attributed to inertial effects. These are due to the surface contribution to the free energy which cannot be disregarded for thin films. 相似文献
73.
Broderick NG Ross GW Offerhaus HL Richardson DJ Hanna DC 《Physical review letters》2000,84(19):4345-4348
We report on the fabrication of what we believe is the first example of a two-dimensional (2D) nonlinear photonic crystal [Berger, Phys. Rev. Lett. 81, 4136 (1998)], where the refractive index is constant but where the 2nd order nonlinear susceptibility is spatially periodic. Such crystals allow for efficient quasi-phase-matched 2nd harmonic generation using multiple reciprocal lattice vectors. External 2nd harmonic conversion efficiencies >60% were measured with picosecond pulses. The fabrication technique is extremely versatile and should allow for the fabrication of a broad range of 2D crystals including quasicrystals. 相似文献
74.
High-energy, high-power ytterbium-doped Q-switched fiber laser 总被引:8,自引:0,他引:8
Alvarez-Chavez JA Offerhaus HL Nilsson J Turner PW Clarkson WA Richardson DJ 《Optics letters》2000,25(1):37-39
We report on a Q -switched, cladding-pumped, ytterbium-doped large-mode-area fiber laser operating at 1090 nm that is capable of generating 2.3 mJ of output pulse energy at a 500-Hz repetition rate and more than 5 W of average output power at higher repetition rates in a high-brightness beam (M(2) = 3) . Using a similar fiber with a smaller core, we generated >0.5-mJ pulses in a diffraction-limited beam. Our results represent a threefold increase in pulse energy over previously published values for Q-switched fiber lasers and firmly establish fiber lasers as compact, multiwatt, multimillijoule pulse sources with large scope for both industrial and scientific applications. 相似文献
75.
Albanis V Bratfalean RT Dhanjal S Zheludev NI Emel'yanov VI Petropoulos P Richardson DJ 《Optics letters》2000,25(21):1594-1596
The reflectivity of a gallium/silica interface formed on an optical flat or at the tip of a cleaved optical fiber can be reduced in a reversible fashion when the interface is excited by a few milliwatts of laser power. This phenomenon occurs at temperatures just below gallium's melting point. We believe that the effect can be attributed to light-induced structuring at the interface. 相似文献
76.
We present a new approach for the simulation of beyond standard model (BSM) physics within the Herwig++ event generator. Our
approach is more generic than previous methods with the aim of minimising the effort of implementing further new physics models.
Spin correlations, which are important for BSM models due to new heavy fermions and bosons, are discussed and their effects
demonstrated for the minimal supersymmetric standard model (MSSM) and Randall–Sundrum model using our new framework. 相似文献
77.
X-ray diffraction has been used to study the nematic phases of the cis and trans isomers of an elongated molecule containing the cyclobutane group. It has been shown that these nematic phases consist of a mixture of single molecules and overlapping core dimers. It has been found that increasing the temperature of the cis isomer rapidly reduces the dimer population, whereas increasing the temperature of the trans isomer enhances the dimer population. This provides an explanation of the relatively high clearing temperature of the trans isomer. The different temperature dependences of the dimer population in the cis and trans isomers has been explained by a model involving inversion of the cylobutane group. 相似文献
78.
E. G. Richardson 《Colloid and polymer science》1937,81(1):87-88
Zusammenfassung Mit Bezug auf kürzlich in der Kolloid-Zeitschrift veröffentlichte Arbeiten wird die Theorie der Analyse der Partikelgröße mittels Sedimentation und Photozelle diskutiert. Es wird darauf hingewiesen, daß der Verfasser schon im Jahre 1934 einen ähnlichen Apparat beschrieben hat. Es wird gezeigt, wie man eine ununterbrochene Verteilungskurve der Partikeldurchmesser eines Dispersoids bekommen kann.Übersetzt von H. A. Wannow (Leipzig). 相似文献
79.
80.