全文获取类型
收费全文 | 1319篇 |
免费 | 96篇 |
国内免费 | 58篇 |
专业分类
化学 | 754篇 |
晶体学 | 12篇 |
力学 | 59篇 |
综合类 | 1篇 |
数学 | 202篇 |
物理学 | 445篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 20篇 |
2020年 | 21篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 30篇 |
2015年 | 27篇 |
2014年 | 47篇 |
2013年 | 83篇 |
2012年 | 66篇 |
2011年 | 90篇 |
2010年 | 56篇 |
2009年 | 65篇 |
2008年 | 78篇 |
2007年 | 73篇 |
2006年 | 75篇 |
2005年 | 54篇 |
2004年 | 53篇 |
2003年 | 51篇 |
2002年 | 78篇 |
2001年 | 48篇 |
2000年 | 50篇 |
1999年 | 16篇 |
1998年 | 14篇 |
1997年 | 19篇 |
1996年 | 30篇 |
1995年 | 17篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1975年 | 14篇 |
1974年 | 4篇 |
1972年 | 5篇 |
1965年 | 6篇 |
排序方式: 共有1473条查询结果,搜索用时 265 毫秒
961.
962.
King‐Fu Lin Shanq‐Chyang Lin An‐Ting Chien Chi‐Chun Hsieh Ming‐Huei Yen Chia‐Hsin Lee Chao‐Sung Lin Wen‐Yen Chiu Yuan‐Hon Lee 《Journal of polymer science. Part A, Polymer chemistry》2006,44(19):5572-5579
Montmorillonites (MMTs) intercalating a potassium persulfate initiator were readily exfoliated in the presence of polymerizing methyl methacrylate during soap‐free emulsion polymerization. Because of the confined space, the polymerizing chains were aggregated into a disk form inside the clay interlayer regions for micellation. It was surprising to find from X‐ray diffraction analysis that the exfoliation of MMT was almost completed in the micellation stage. Further polymerization afforded latex particles of exfoliated poly(methyl methacrylate) (PMMA)–MMT nanocomposites. In addition, two kinds of MMT nanosheets were collected by the removal of PMMA with toluene: One was a single‐layer nanosheet with a thickness of 1.25 nm, and the other was a stacked sheet with an average thickness of 7.5 nm that may have consisted of six individual layers. Electron diffraction analysis revealed that if the individual layer of an MMT nanosheet were not a single crystal, it should contain an ultrathin layer of ice with a commonly occurring hexagonal phase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5572–5579, 2006 相似文献
963.
Motivated by a two-bump (or 1-peak plus 1-hump) structure in the ATIC data, we perform a statistical analysis fitting the PAMELA and ATIC data to a dark matter model, in which the dark matter particle can undergo both annihilation and decay. Using a chi-square analysis we show that both data can be simultaneously fitted better with such a double-action dark matter particle. We use an existing neutrino mass model in literature to illustrate the idea. 相似文献
964.
965.
Lizhu ZHANG Yiran AN Zhi LI G. Q. CHEN Joseph H. W. LEE Department of Mechanics Engineering Science / State Key Laboratory for Studies of Turbulence Complex Systems Peking University Beijing China e-mail: zhlzh@cnls.pku.edu.cn De 《Communications in Nonlinear Science & Numerical Simulation》2001,(4)
IntroductionGravity currents, which are primarily horizonta1 flows and generated by a density differenceof only a few percent, are recognzed by rnore and more scientists fqr its importance in envi-ronmental and industrial flo.s[i]. NIany interesting'fiows such as sea water intrusion, turbiditycurrents. sandstorms, avalanches and pollutant outfalls can be tegarded as gravity currents\:.. ~ l'Lock.release gravity current, the most typical gravit1' current. is considered in this paper, as'a conti… 相似文献
966.
N. Misra Y. Pan N.W. Cheung C.P. Grigoropoulos 《Applied Physics A: Materials Science & Processing》2008,90(2):219-223
Semiconductor nanowires have attracted intense interest due to potential applications in electronics, sensors and photonics.
Introduction of dopants and their subsequent activation are essential for exploiting the electronic properties of semiconductor
materials. In this work, we demonstrate pulsed laser annealing of silicon nanowires by visible radiation to be an efficient
way for activating incorporated dopants and repairing implantation damage in a process that is compatible with sensitive flexible
substrates. In situ electrical monitoring was used to study the laser annealing process. The absorption of laser light in
SiNWs was shown to be strongly dependent on the light polarization and nanowire diameter based on finite difference time domain
simulations.
PACS 42.62.-b; 64.70.Nd; 78.67.n; 81.16.c 相似文献
967.
This paper studies the M/G/1 processor-sharing (PS) queue, in particular the sojourn time distribution conditioned on the
initial job size. Although several expressions for the Laplace-Stieltjes transform (LST) are known, these expressions are
not suitable for computational purposes. This paper derives readily applicable insensitive bounds for all moments of the conditional sojourn time distribution. The instantaneous sojourn time, i.e., the sojourn time of an infinitesimally small job, leads to insensitive upper bounds requiring only knowledge
of the traffic intensity and the initial job size. Interestingly, the upper bounds involve polynomials with so-called Eulerian
numbers as coefficients. In addition, stochastic ordering and moment ordering results for the sojourn time distribution are
obtained.
AMS Subject Classification: 60K25, 60E15
This work has been partially funded by the Dutch Ministry of Economic Affairs under the program ‘Technologische Samenwerking
ICT-doorbraakprojecten’, project TSIT1025 BEYOND 3G. 相似文献
968.
Electron density studies of two organic radical species, para-nitronyl-4-benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl, 1, and para-bromide-4-benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl, 2, have been carefully investigated by X-ray diffraction method at low temperature( 125 K and 100 K). They crystallized in the space group of Pnma and P21/c respectively. No phase transition is detected at the temperature range studied. Electron density distribution based on Multipole model will be presented. Electron density accumulation and the delocalized □-character found at C-C bonds of the benzene ring. 相似文献
969.
Some continuous and discrete versions of Opial-type inequalities which are readily applicable to differential and difference operators are established. These generalize earlier results of Anastassiou and Pe?ari?, and of Koliha and Pe?ari?. 相似文献
970.