全文获取类型
收费全文 | 1261篇 |
免费 | 19篇 |
国内免费 | 7篇 |
专业分类
化学 | 728篇 |
晶体学 | 4篇 |
力学 | 30篇 |
数学 | 220篇 |
物理学 | 305篇 |
出版年
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 58篇 |
2012年 | 42篇 |
2011年 | 62篇 |
2010年 | 20篇 |
2009年 | 25篇 |
2008年 | 49篇 |
2007年 | 46篇 |
2006年 | 62篇 |
2005年 | 60篇 |
2004年 | 39篇 |
2003年 | 63篇 |
2002年 | 38篇 |
2001年 | 30篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 23篇 |
1995年 | 21篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 21篇 |
1985年 | 29篇 |
1984年 | 24篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 20篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 27篇 |
1975年 | 25篇 |
1974年 | 21篇 |
1973年 | 17篇 |
1970年 | 10篇 |
1968年 | 9篇 |
1966年 | 7篇 |
排序方式: 共有1287条查询结果,搜索用时 15 毫秒
961.
Synthesis and characterisation of a [Ni8] single molecule magnet and another octanuclear nickel cage
Bell A Aromí G Teat SJ Wernsdorfer W Winpenny RE 《Chemical communications (Cambridge, England)》2005,(22):2808-2810
Two new octanuclear nickel(II) cage complexes are reported; the second is a new single molecule magnet. 相似文献
962.
R. J. Pillar M. Ginic-Markovic S. R. Clarke A. K. Gibson W. R. Bell H. R. Brown D. J. Willis W. A. Renshaw J. G. Matisons 《Journal of Thermal Analysis and Calorimetry》2005,80(1):211-216
Summary This study investigates mechanisms of cold rolling oil removal from the surface of low-carbon steel. The removal process has been probed using thermogravimetric analysis techniques. A range of furnace atmospheres, from non-oxidizing through to highly oxidising, have been used to simulate the oil removal conditions in the industrial process. The activation energies of oil removal under each gas atmosphere have been determined by MTG and the Flynn-Wall-Ozawa method. The results show that a reducing atmosphere is the optimal environment for effective oil removal. Steel-oil surface interactions have also been investigated to show that the steel substrate catalyses oil removal. 相似文献
963.
[reaction: see text]. Allylation of aromatic aldehydes with allyltrichlorosilane is catalyzed by the new terpene-derived pyridine N-oxide (+)-METHOX (< or =5 mol %) in MeCN with high enantioselectivities (< or =96% ee) and conversion rates; this catalyst retains high selectivity even at room temperature. 相似文献
964.
965.
Denah M Appelt Maria R Roupas Deana S Way Marcus G Bell Elizabeth V Albert Christine J Hammond Brian J Balin 《BMC neuroscience》2008,9(1):13
Background
Chlamydophila (Chlamydia) pneumoniae is an intracellular bacterium that has been identified within cells in areas of neuropathology found in Alzheimer disease (AD), including endothelia, glia, and neurons. Depending on the cell type of the host, infection by C. pneumoniae has been shown to influence apoptotic pathways in both pro- and anti-apoptotic fashions. We have hypothesized that persistent chlamydial infection of neurons may be an important mediator of the characteristic neuropathology observed in AD brains. Chronic and/or persistent infection of neuronal cells with C. pneumoniae in the AD brain may affect apoptosis in cells containing chlamydial inclusions. 相似文献966.
Acosta D Affolder T Akimoto H Albrow MG Amaral P Ambrose D Amidei D Anikeev K Antos J Apollinari G Arisawa T Artikov A Asakawa T Ashmanskas W Azfar F Azzi-Bacchetta P Bacchetta N Bachacou H Bailey S de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Baroiant S Barone M Bauer G Bedeschi F Belforte S Bell WH Bellettini G Bellinger J Benjamin D Bensinger J Beretvas A Berge JP Berryhill J Bhatti A Binkley M Bisello D Bishai M Blair RE Blocker C Bloom K Blumenfeld B Blusk SR Bocci A Bodek A 《Physical review letters》2002,88(16):161802
We report on measurements of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections (d(2)sigma/dp(T)dy)(/y/<0.4), as well as on the Upsilon(1S) polarization in p p macro collisions at square root of s = 1.8 TeV using a sample of 77+/-3 pb(-1) collected by the collider detector at Fermilab. The three resonances were reconstructed through the decay Upsilon-->mu(+)mu(-). The measured angular distribution of the muons in the Upsilon(1S) rest frame is consistent with unpolarized meson production. 相似文献
967.
968.
W. Bell K. Braune G. Claesson D. Drijard M. A. Faessler H. G. Fischer H. Frehse R. W. Frey S. Garpman W. Geist C. Gruhn P. Hanke M. Heiden W. Herr P. G. Innocenti T. J. Ketel E. E. Kluge I. Lund G. Mornacchi T. Nakada I. Otterlund M. Panter B. Povh A. Putzer E. Stenlund T. J. M. Symons R. Szwed O. Ullaland 《Zeitschrift für Physik A Hadrons and Nuclei》1986,324(1):67-73
We have investigated kinematical correlations between the outgoing beam proton and the proton emerging from the fragmentingα-particle inpα collisions at \(\sqrt {s_{p\alpha } } = 88GeV\) . Strong correlations are seen, indicating the dominance of quasi-elasticpp scattering in the fragmentation channelp+α→p+pX, for the ¦t¦ range 0.05–1.00 (GeV/c)2. A Monte Carlo simulation of this process can explain the observed correlation spectra assuming an admixture of about 16% spectator protons. 相似文献
969.
H. A. Klein A. S. Bell G. P. Barwood P. Gill 《Applied physics. B, Lasers and optics》1990,50(1):13-17
172Yb+ ions in an rf trap have been laser cooled for the first time by driving the 2
S
1/2–2
P
1/2 transition at 369.5 nm. It was necessary to irradiate the ions with 2.438 m infra-red radiation to depopulate the metastable 2
D
3/2 state. An upper limit on ion energies was determined by observing the size of the trapped cloud and corresponds to a temperature below 2 K. Cooled ion lineshapes were compared with simulations and coherence nulls were observed in the infra-red frequency scans. 相似文献
970.