全文获取类型
收费全文 | 1594篇 |
免费 | 40篇 |
国内免费 | 7篇 |
专业分类
化学 | 913篇 |
晶体学 | 8篇 |
力学 | 19篇 |
数学 | 213篇 |
物理学 | 488篇 |
出版年
2021年 | 10篇 |
2020年 | 25篇 |
2019年 | 17篇 |
2018年 | 16篇 |
2016年 | 31篇 |
2015年 | 21篇 |
2014年 | 21篇 |
2013年 | 60篇 |
2012年 | 63篇 |
2011年 | 86篇 |
2010年 | 40篇 |
2009年 | 39篇 |
2008年 | 67篇 |
2007年 | 54篇 |
2006年 | 52篇 |
2005年 | 55篇 |
2004年 | 55篇 |
2003年 | 43篇 |
2002年 | 55篇 |
2001年 | 31篇 |
2000年 | 28篇 |
1999年 | 22篇 |
1998年 | 18篇 |
1997年 | 17篇 |
1996年 | 39篇 |
1995年 | 40篇 |
1994年 | 30篇 |
1993年 | 42篇 |
1992年 | 45篇 |
1991年 | 32篇 |
1990年 | 32篇 |
1989年 | 35篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1985年 | 29篇 |
1984年 | 21篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 19篇 |
1978年 | 20篇 |
1977年 | 16篇 |
1976年 | 8篇 |
1975年 | 19篇 |
1974年 | 25篇 |
1973年 | 26篇 |
1972年 | 10篇 |
1970年 | 13篇 |
排序方式: 共有1641条查询结果,搜索用时 15 毫秒
131.
Recent magnetotransport experiments on high mobility two-dimensional electron systems have revealed many-body electron states unique to high Landau levels. Among these are reentrant integer quantum Hall states which undergo sharp transitions to conduction above some threshold field. Here we report that these transitions are often accompanied by narrow- and broad-band noise with frequencies which are strongly dependent on the magnitude of the applied dc current. 相似文献
132.
Mechanism of hydrogen sorption in single-walled carbon nanotubes 总被引:1,自引:0,他引:1
133.
The electrostatic self-assembly monolayer process has been utilized for what is believed to be the first time to deposit quarter-wavelength stacks on the end faces of cleaved and polished optical fibers. Standard multimode optical fibers as well as single-mode optical fibers were used as substrates with different coating materials to fabricate broadband filters, and the experimentally measured spectral responses of these devices are shown. These optical filter structures were employed to develop chemical sensors that use an unperturbed reference wavelength to normalize the output signal. 相似文献
134.
An insecticide, pirimicarb, and a fungicide, azoxystrobin, were analyzed by capillary electrochromatography. Nine environmental matrices derived from soil, plant and animal extracts were used. After a series of 311 consecutive injections with no washing between injections, retention times increased by ca. 0.5 min. The use of exaggerated application rates for metabolism studies enabled the detection of xenobiotic pesticide degradates by UV absorbance. A 1.2 mm path length, high-sensitivity flow cell gave a gain in sensitivity; however, a further increase in sensitivity of at least two orders of magnitude is required for pesticide residue analysis. Analyte stacking using large volume injections of aqueous samples led to a large increase in retention times. 相似文献
135.
Ramanujan's partition congruences can be proved by first showing that the coefficients in the expansions of (q; q)
r
satisfy certain divisibility properties when r = 4, 6 and 10. We show that much more is true. For these and other values of r, the coefficients in the expansions of (q; q)
r
satisfy arithmetic relations, and these arithmetic relations imply the divisibility properties referred to above. We also obtain arithmetic relations for the coefficients in the expansions of (q; q)
r
(q
t; q
t)
s
, for t = 2, 3, 4 and various values of r and s. Our proofs are explicit and elementary, and make use of the Macdonald identities of ranks 1 and 2 (which include the Jacobi triple product, quintuple product and Winquist's identities). The paper concludes with a list of conjectures. 相似文献
136.
Lablanquie P Penent F Hall RI Eland JH Bolognesi P Cooper D King GC Avaldi L Camilloni R Stranges S Coreno M Prince KC Muehleisen A &Zbreve;itnik M 《Physical review letters》2000,84(3):431-434
Fluorescence decay of the 2s2p(6)np (1)P(o) excited states of neon has been observed directly for the first time. This process has also been observed indirectly by threshold photoelectron spectroscopy and in electron/photon coincidences. The measurements have allowed this weak decay channel to be characterized and branching ratios derived. The fluorescence excitation spectrum is well described by a simple Rydberg model that highlights the interplay and competition between the decay channels of autoionization and fluorescence. 相似文献
137.
A three-step conversion of 3aα-H-4α-(3′-propionic acid)-7aβ-methylhexahydro-1,5-indanedione into 19-norandrost-4-ene- 3,17-dione is described. 相似文献
138.
Hasell T Schmidtmann M Stone CA Smith MW Cooper AI 《Chemical communications (Cambridge, England)》2012,48(39):4689-4691
A crystalline porous organic cage molecule, CC3, is shown to adsorb up to 20.1 wt% water reversibly. This was confirmed by both gravimetric sorption and by crystallographic analysis. Crystals of CC3 are stable in boiling water for at least 4 h. The surprising chemical and supramolecular stability of these imine-based molecular crystals suggests scope for practical applications in humid environments. 相似文献
139.
Abe F Amidei D Apollinari G Atac M Auchincloss P Baden AR Bamberger A Barbaro-Galtieri A Barnes VE Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Bensinger J Beretvas A Berge JP Bertolucci S Bhadra S Binkley M Blair R Blocker C Booth AW Brandenburg G Brown D Buckley E Byon A Byrum KL Campagnari C Campbell M Carey R Carithers W Carlsmith D Carroll JT Cashmore R Cervelli F Chadwick K Chiarelli G Chinowsky W Cihangir S Clark AG Connor D Contreras M Cooper J Cordelli M Crane D Curatolo M 《Physical review letters》1989,63(7):720-723
140.
L. Adiels G. Backenstoss I. Bergström S. Carius S. Charalambous M. D. Cooper Ch. Findeisen D. Hatzifotiadou M. Hugi A. Kerek H. O. Meyer P. Pavlopoulos J. Repond L. Tauscher D. Troester M. C. S. Williams K. Zioutas 《Zeitschrift fur Physik C Particles and Fields》1989,42(1):49-58
The inclusive η-momentum spectrum from \(\bar p\) annihilations at rest in liquid hydrogen was measured at LEAR. Branching ratios were obtained for $$\begin{gathered} p\bar p \to \eta \omega \left( {1.04_{ - 0.10}^{ + 0.09} } \right)\% ,\eta \rho ^0 \left( {0.53_{ - 0.08}^{ + 0.20} } \right)\% , \hfill \\ \pi a_2 \left( {8.49_{ - 1.10}^{ + 1.05} } \right)\% ,\eta \pi ^0 \left( {1.33 \pm 0.27} \right) \times 10^{ - 4} , \hfill \\ \end{gathered} $$ , and ηη(8.1±3.1)×10?5. An upper limit for \(p\bar p \to \eta \eta '\) of 1.8×10?4 at 95% CL was found. The ratio of the branching ratios is BR(η?)/BR(ηω)=0.51 ?0.06 +0.20 . For the ratio of branching ratios into two pseudoscalar mesons, we have BR(ηπ0)/BR(π0π0)=0.65±0.14, BR(ηη)/BR(π0π0), BR(η η ′ )/BR(π0π0) at 95% CL, and BR(ηη)/BR(ηπ0). 相似文献