全文获取类型
收费全文 | 22348篇 |
免费 | 889篇 |
国内免费 | 70篇 |
专业分类
化学 | 13217篇 |
晶体学 | 86篇 |
力学 | 518篇 |
数学 | 3417篇 |
物理学 | 6069篇 |
出版年
2023年 | 152篇 |
2021年 | 255篇 |
2020年 | 319篇 |
2019年 | 265篇 |
2018年 | 300篇 |
2017年 | 308篇 |
2016年 | 613篇 |
2015年 | 593篇 |
2014年 | 561篇 |
2013年 | 1097篇 |
2012年 | 1167篇 |
2011年 | 1398篇 |
2010年 | 672篇 |
2009年 | 613篇 |
2008年 | 1133篇 |
2007年 | 1141篇 |
2006年 | 1118篇 |
2005年 | 973篇 |
2004年 | 750篇 |
2003年 | 710篇 |
2002年 | 635篇 |
2001年 | 472篇 |
2000年 | 382篇 |
1999年 | 306篇 |
1998年 | 265篇 |
1997年 | 268篇 |
1996年 | 266篇 |
1995年 | 235篇 |
1994年 | 230篇 |
1993年 | 239篇 |
1992年 | 253篇 |
1991年 | 224篇 |
1990年 | 192篇 |
1989年 | 180篇 |
1988年 | 165篇 |
1987年 | 177篇 |
1986年 | 169篇 |
1985年 | 207篇 |
1984年 | 258篇 |
1983年 | 204篇 |
1982年 | 225篇 |
1981年 | 235篇 |
1980年 | 210篇 |
1979年 | 186篇 |
1978年 | 211篇 |
1977年 | 211篇 |
1976年 | 177篇 |
1975年 | 164篇 |
1974年 | 155篇 |
1973年 | 147篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
L. Landström D. Brodoceanu K. Piglmayer D. Bäuerle 《Applied Physics A: Materials Science & Processing》2006,84(4):373-377
Extraordinary optical transmission through metal-coated close-packed monolayers has been observed. The monolayers consist of silica (a-SiO2) or polystyrene microspheres that form two-dimensional close-packed lattices by self-assembly. Metal layers of Ag, Au and Ni with different thicknesses (larger than the skin depth) were evaporated onto such lattices by means of standard techniques. The optical transmission spectra investigated between 300 and 2500 nm show pronounced peaks that scale with the diameter and the optical properties of the composite slabs. The enhanced transmission observed is most likely mediated via plasmons. PACS 78.66.-w; 81.16.Dn; 82.70.Dd 相似文献
42.
Mustafa Çelebier Ertan Şahin Nilgün Ancın Nurşen Altuntaş Öztaş Selma Gül Öztaş 《应用有机金属化学》2007,21(10):viii-viii
The article referenced above was first published online on 30 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
43.
Differentiation of functions w.r.t. finite atomless measures with compact support on the real line is introduced. The related harmonic calculus is similar to that of the classical Lebesgue case. As an application we obtain the Weyl exponent for the spectral asymptotics of the Laplacians w.r.t. linear Cantor-type measures with arbitrary weights. 相似文献
44.
Pál Sohár Gábor Bernáth Géza Stájer Angela E. Szabo 《Magnetic resonance in chemistry : MRC》1989,27(9):872-876
Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene-azetidinone-fused 3,1-oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments. 相似文献
45.
46.
Electronic properties of model quantum-dot structures in zero and finite magnetic fields 总被引:1,自引:0,他引:1
H. Saarikoski E. Räsänen S. Siljamäki A. Harju M.J. Puska R.M. Nieminen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):241-252
We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral
dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional
theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method.
The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions
which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic
field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability
of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained
for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking
solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed.
Received 16 October 2001 and Received in final form 17 January 2002 相似文献
47.
Pirjo Sainio Irma Mäkinen Jaap-Willem Hutter Theo den Ouden Mikael Krysell 《Accreditation and quality assurance》2006,11(3):116-121
The international joint project HYCREF (Contract No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogeneous and stable reference materials of water, soil, and waste contaminated with mineral oil hydrocarbons and to certify the mineral oil content by gas chromatographic methods. The results of a feasibility study for the preparation of three soil reference materials are discussed in this paper, and for the preparation of three waste reference materials in the second part (Koch et al., Accred Qual Assur submitted for publication). The soil materials were selected to represent different soil types and contamination levels. The project plan set three requirements for these reference materials: uncertainty in the mineral oil content resulting from the certification exercise <5%, a sample inhomogeneity of <3% and a minimum long-term stability of 5 years. For the most part, these requirements were met within this project. 相似文献
48.
49.
U. Täuber C.E.M. Carvalho R.F. dos Santos C.G. Carvalhaes C.E. Fellows 《Applied physics. B, Lasers and optics》2007,87(3):475-481
A six level rate equation system was used to investigate the impact of photodepletion to amplified spontaneous emission (ASE)
of intramolecular proton-transfer (IPT) dyes incorporated into polymeric hosts. The model includes the most important transitions
for the normal and tautomer form of the molecule as well as intersystem crossing and triplet–triplet transitions. The experimentally
observed pulse shape as well as photodepletion phenomena, i.e. a first order exponential decay of the ASE intensity and a
shortening in ASE pulse width, have been simulated successfully. Additionally, the model was used to propose an explanation
of the unexpected high photodepletion of proton-transfer dyes in solids. The results show that the emission cross section
and reabsorption cross section of the tautomer form of the molecule are the most important parameter not only for efficiency
but also for photodepletion. The model was tested by comparison with experimental results of 2-(2’-hydroxyphenyl)benzimidazole
in polymethylmethacrylate (PMMA), polystyrene (PS) and a 1:1 alternating copolymer matrix PS-co-PMMA.
PACS 78.45.th; 42.55.Mv; 42.70.Jk 相似文献
50.