全文获取类型
收费全文 | 2441篇 |
免费 | 132篇 |
国内免费 | 489篇 |
专业分类
化学 | 1491篇 |
晶体学 | 3篇 |
力学 | 106篇 |
综合类 | 8篇 |
数学 | 482篇 |
物理学 | 972篇 |
出版年
2022年 | 11篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 19篇 |
2017年 | 12篇 |
2016年 | 32篇 |
2015年 | 24篇 |
2014年 | 106篇 |
2013年 | 64篇 |
2012年 | 42篇 |
2011年 | 400篇 |
2010年 | 213篇 |
2009年 | 199篇 |
2008年 | 29篇 |
2007年 | 41篇 |
2006年 | 82篇 |
2005年 | 150篇 |
2004年 | 403篇 |
2003年 | 218篇 |
2002年 | 168篇 |
2001年 | 202篇 |
2000年 | 41篇 |
1999年 | 42篇 |
1998年 | 65篇 |
1997年 | 43篇 |
1996年 | 31篇 |
1995年 | 29篇 |
1994年 | 32篇 |
1993年 | 79篇 |
1992年 | 67篇 |
1991年 | 31篇 |
1990年 | 25篇 |
1989年 | 31篇 |
1988年 | 20篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1977年 | 3篇 |
1932年 | 2篇 |
1928年 | 2篇 |
1919年 | 3篇 |
1917年 | 2篇 |
1916年 | 2篇 |
1911年 | 4篇 |
1910年 | 3篇 |
1909年 | 3篇 |
1907年 | 3篇 |
排序方式: 共有3062条查询结果,搜索用时 46 毫秒
991.
FAN Jing ZHU GuiFen WANG HaiBo & WANG JianJi Henan Key Laboratory for Environmental Pollution Control Key Laboratory for Yellow Huai River Water Environmental Pollution Control Ministry of Education School of Chemical Environmental Sciences Henan Normal University Xinxiang China 《中国科学B辑(英文版)》2011,(6)
Trace of Pb(Ⅱ) has been on-line separated and enriched from environmental samples and wastewater by using the self-made alizarin violet functionalized silica gel micro-column coupling with a sequential injection sampling technology. The determination is based on the color reaction of Pb(Ⅱ) with iodide and crystal violet to form an ionic association complex in the presence of polyvinyl alcohol and hydrochloric acid. The use of the microcolumn can prevent the interference of most familiar metal ions, and ther... 相似文献
992.
LV YongJun XU Jian GUO Yong & SHAO ShiJun Key Laboratory of Chemistry of Northwestern Plant Resources Key Laboratory for Natural Medicine of Gansu Province Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou China State Key Laboratory for Oxo Synthesis Selective Oxidation China Graduate University of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2011,(5)
A boradiazaindacenes (BODIPY)-phenol conjugate,1,can act as a colorimetric and fluorometric sensor for sensitive and se-lective measurement of F-over AcO-and H2PO-4 in CH3CN. Sensor 1 gives response to F-in a 1:1 ratio via the deprotonation of the phenolic OH proton,which results in color change from pale yellow to light green and quenching of bright green fluo-rescence. 相似文献
993.
ZHANG Ding YAN Hui ZHANG Huan QI Lu Beijing National Laboratory for Molecular Sciences 《高等学校化学研究》2011,(3):478-481
A new solid polymer electrolyte PEO20-LiTf-Urea1.5 was prepared by solution casting technique. The energy of frontier orbitals for the components of the electrolyte was predicted by quantum chemistry calculations, and TG stability and electrochemical features were measured. Urea exhibited a lower HOMO energy than PEO, implying its enhanced stability against electrochemical oxidation. Experimentally addition of urea increases the ionic conductivity, which guarantees conductivity requirement for lithium ion b... 相似文献
994.
995.
996.
The KRYSTHAL Collaboration L. A. Harland-Lang V. A. Khoze M. G. Ryskin W. J. Stirling 《The European Physical Journal C - Particles and Fields》2011,71(2):1545
We study the Central Exclusive Production (CEP) of χ
cJ
and η
c
mesons at RHIC in proton–proton collisions. We consider the χ
cJ
→J/ψ + γ decay channels and, recalling that the J
z
=0 suppression of the J=1,2 states can be compensated by their larger branchings to J/ψ + γ, present predictions of rates and distributions for χ
c(0,1,2) production. Particular attention is paid to the impact of p
⊥ cuts applied to the outgoing protons, which can influence the relative rates significantly. The distribution in the azimuthal
angle difference between the outgoing protons and the proton p^2p_{\perp}^{2} is also studied, and shown to depend sensitively on the spin and parity of the centrally produced meson, as well as being
affected by the soft-survival factors, S
2. Two- and four-body decays, which are particularly relevant for χ
c0 production, are also considered. We show that in the two-body case, backgrounds from ‘direct’ QCD production based on both
perturbative and non-perturbative models are expected to be under control. 相似文献
997.
WANG FuRong & DU ShaoFei School of Information Beijing Wuzi University Beijing China School of Mathematical Sciences Capital Normal University Beijing 《中国科学 数学(英文版)》2011,(2)
In [J. Algeb. Combin. 19(2004), 123-141], Du et al. classified the orientable regular embeddings of connected simple graphs of order pq for any two primes p and q. In this paper, we shall classify the nonorientable regular embeddings of these graphs, where p ≠ q. Our classification depends on the classification of primitive permutation groups of degree p and degree pq but is independent of the classification of the arc-transitive graphs of order pq. 相似文献
998.
Hoang The Ban Hideaki Hagihara Yasuo Tsunogae Zhengguo Cai Takeshi Shiono 《Journal of polymer science. Part A, Polymer chemistry》2011,49(1):65-71
This article reports the synthesis and characterization of an extremely high thermostable cyclic olefin copolymer with advanced optical properties resulting from the vinyl addition copolymerization of norbornene with styrene catalyzed by a substituted fluorenylamidodimethyltitanium catalyst [Me2Si(3,6‐tBu2Flu)(tBuN)]TiMe2 activated with a [Ph3C] [B(C6F5)4]/Al(iBu)3 cocatalyst using o‐dichlorobenzene as solvent. The prepared copolymer possesses a glass transition temperature as high as polyimide (Tg > 300 °C) and a high transmittance which is comparable with that of the conventional optical resins ([T] > 90%). The incorporation of polystyrene, which exhibits a negative birefringence into the vinyl‐added polynorbornene that possesses an intrinsic positive birefringence, effectively reduced the birefringent magnitude of the norbornene‐styrene copolymer due to a mutual compensation between these opposite‐sign birefringences. The absence of any functional and aromatic heterocyclic groups and the presence of highly hydrophobic saturated bicyclic rings in the copolymer main chains effectively prevented the diffusion of water/oxygen and thus enhanced the dimensional and optical stabilities of the material. Preliminary results on the characterization of the thermal stability, mechanical, and optical properties of the vinyl‐added norbornene‐styrene copolymers indicate that they satisfy all the rigorous requirements for a polymer to be applied as a flexible substrate for the manufacturing of the flexible displays. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
999.
Hoang The Ban Masahiro Shigeta Tsutomu Nagamune Mitsugu Uejima 《Journal of polymer science. Part A, Polymer chemistry》2013,51(21):4584-4591
An efficient and environmentally benign synthetic method for the production of the stabilized cyclo‐olefin copolymer latexes and their carbon nanotube composite nanoparticles has been developed using an emulsion ring opening metathesis copolymerization catalyzed by the 2nd generation Grubbs catalyst in aqueous solution. Homopolymerizations of norbornene (NB) and dicyclopentadiene (DCPD) in aqueous solution yield unstable polymer latexes in combination with a large amount of their flocculation fractions. Copolymerizations of NB or DCPD with a selected liquid cyclo‐olefin comonomer dramatically improve not only the colloidal stability of the copolymer latexes but also the thermal stability of the copolymer nanoparticles. The liquid cyclo‐olefin comonomer plays a double role as a liquefied agent for the solid NB and DCPD monomers before the emulsification treatment, and a reactive comonomer itself to control entirely the copolymerization system. The as‐prepared cyclo‐olefin copolymer latexes exhibit an exceptionally high compatibility with a well‐dispersed carbon nanotube (CNT) in aqueous solution due to strong π–π interactions between the graphitic surfaces of the CNT with the C‐C double bonds located on the cyclo‐olefin copolymer main chains. Accordingly, a binary blending of these two well‐dispersed colloidal systems in aqueous solution led to the fabrication, for the first time, of the highly electrical conductive cyclo‐olefin copolymer/CNT composite nanoparticles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4584–4591 相似文献
1000.