全文获取类型
收费全文 | 3167篇 |
免费 | 104篇 |
国内免费 | 27篇 |
专业分类
化学 | 1974篇 |
晶体学 | 28篇 |
力学 | 85篇 |
数学 | 650篇 |
物理学 | 561篇 |
出版年
2023年 | 14篇 |
2022年 | 45篇 |
2021年 | 85篇 |
2020年 | 76篇 |
2019年 | 88篇 |
2018年 | 80篇 |
2017年 | 69篇 |
2016年 | 124篇 |
2015年 | 112篇 |
2014年 | 141篇 |
2013年 | 237篇 |
2012年 | 206篇 |
2011年 | 218篇 |
2010年 | 152篇 |
2009年 | 150篇 |
2008年 | 187篇 |
2007年 | 181篇 |
2006年 | 146篇 |
2005年 | 123篇 |
2004年 | 99篇 |
2003年 | 73篇 |
2002年 | 79篇 |
2001年 | 35篇 |
2000年 | 40篇 |
1999年 | 30篇 |
1998年 | 20篇 |
1997年 | 22篇 |
1996年 | 35篇 |
1995年 | 27篇 |
1994年 | 24篇 |
1993年 | 21篇 |
1992年 | 28篇 |
1991年 | 13篇 |
1990年 | 21篇 |
1989年 | 14篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 24篇 |
1977年 | 22篇 |
1976年 | 12篇 |
1970年 | 7篇 |
1968年 | 10篇 |
排序方式: 共有3298条查询结果,搜索用时 15 毫秒
901.
We prove that the absolutely continuous subspace of the completely non-selfadjoint part of a first-order dissipative Dirac-like
system is trivial when the imaginary part of the potential is non-integrable. 相似文献
902.
903.
Induced absorption spectra in the range 200–900 nm at 77 and 290 K for Li2B4O7 single crystals, isotopically Li and B enriched are presented after irradiation of these crystals by thermal neutrons with fluence 1.8×1016 cm−2. The dependence of induced absorption spectra on the isotope composition was revealed: for 6Li210B4O7 and 7Li210B4O7 crystals intensive band in the region of 280–294 nm was observed. Under substitution of 7Li isotope by 6Li in the lithium tetraborate lattice no changes in the absorption spectra were observed. The nuclear reaction 10B(n,)7Li is proposed to be the main mechanism of formation of the radiation defects. 相似文献
904.
Burak Ozbagci 《Topology and its Applications》2007,154(4):908-916
We describe explicit horizontal open books on some Seifert fibered 3-manifolds. We show that the contact structures compatible with these horizontal open books are Stein fillable and horizontal as well. Moreover we draw surgery diagrams for some of these contact structures. 相似文献
905.
Lucjan Strekowski Dong-Feng Hou Roman L. Wydra Raymond F. Schinazi 《Journal of heterocyclic chemistry》1993,30(6):1693-1695
Phenothiazin-5-ium tetraiodide hydrate ( 2 ), the suggested oxidation product of phenothiazine with iodine, is treated with two equivalents of a dialkylamine to give 3-(dialkylamino)phenothiazin-5-ium triiodides, 3-6 . 3,7-Disubstituted phenothiazin-5-ium iodides, 7-9 , are obtained by the reaction of 3-6 with an amine. 相似文献
906.
Generalizing the work of Lua and Grosberg [R.C. Lua, A.Y. Grosberg, J. Phys. Chem. B 109 (2005) 6805], we verify the validity of the Jarzynski equation for the non-equilibrium expansion of an ideal relativistic gas and black-body radiation, respectively. The upper limit for the speed of the particles allows one to choose the parameters of the problem such that no multiple collisions need to be taken into account. Although related, the two cases considered differ from each other due to the quantum nature of photons. We show that bunching of photons is crucial for the Jarzynski equation to hold. 相似文献
907.
908.
Piotr Kutrowski Piotr Michorczyk Lucjan Chmielarz Zofia Piwowarska Barbara Dudek Jan Ogonowski Roman Dziembaj 《Thermochimica Acta》2008,471(1-2):26-32
Active carbon was used as a support for chromium(III) oxide phase. The synthesized materials appeared to be very active catalysts of the propane dehydrogenation in the presence of CO2. An influence of the Cr content on the catalytic activity and selectivity was observed. The best results were achieved over the sample containing about 5 wt.% of Cr. A negative effect of activity decay with time-on-stream was found. The reasons of the observed deactivation were explained using the thermal analysis method. A behavior of the fresh and used samples was tested in a temperature range of 25–1000 °C in different atmospheres (inert gas, air or CO2). It was found that the catalytic runs resulted in a partial decomposition of surface O-containing groups, which together with CrOx species play a role of active centers. Moreover, a formation of inactive carbonaceous deposit on the catalyst surface was observed. 相似文献
909.
The syntheses of four new tungsten(V) dimeric thio-complexes with disulphido bridge are reported. The complexes have been identified by IR and electronic spectra, magnetic susceptibilities and analytical data. On the basis of the physical measurements we propose these complexes the following formula W2S4(Rdtc)2, where dtc = dithiocarbamate and R = morpholine, piperidine, N-ethylaniline and N,N-methylcyclohexyl. The low values of magnetic moments show a WW interaction. IR spectral results support a bidentate ligand behaviour and show a band in the 550-525 cm?1 region, that we attribute to a W S bond. 相似文献
910.
Micallef R. W. Kivshar Yu. S. Love J. D. Burak D. Binder R. 《Optical and Quantum Electronics》1998,30(7-10):751-770
We investigate how two-dimensional spatial optical solitons can be generated in a non-linear Kerr medium using the non-linear guided modes of a weakly-guiding slab waveguide with a linear core and a non-linear cladding as the source of excitation. Symmetric, antisymmetric and asymmetric non-linear modes are considered, from which we determine the parameters of single solitons, oscillating two-soliton bound states, and two repelling solitons, respectively. Both the beam propagation method and inverse scattering transform are used. 相似文献