全文获取类型
收费全文 | 596篇 |
免费 | 13篇 |
专业分类
化学 | 404篇 |
晶体学 | 4篇 |
力学 | 14篇 |
数学 | 49篇 |
物理学 | 138篇 |
出版年
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 53篇 |
2012年 | 21篇 |
2011年 | 29篇 |
2010年 | 27篇 |
2009年 | 13篇 |
2008年 | 32篇 |
2007年 | 28篇 |
2006年 | 31篇 |
2005年 | 26篇 |
2004年 | 21篇 |
2003年 | 10篇 |
2002年 | 26篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1973年 | 3篇 |
1968年 | 4篇 |
1966年 | 3篇 |
1955年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有609条查询结果,搜索用时 15 毫秒
81.
The new molybdenum cyanonitrosyl complexes, R2[Mo(NO)(CN)5]·2H2O (R = Ph4P and Bu4N) and [Mo(NO)(CN)3(L-L)]·H2O [L-L = 相似文献
82.
H. N. Nigam 《Acta Mathematica Hungarica》1963,14(3-4):331-342
83.
Summary Cobalt(II), nickel(ll), and copper(II) complexes of piperidinum pentamethylene dithiocarbamate (pipmdte) have been prepared and studied by spectral (i.r. and absorption) and magnetic methods. The M(pipmdte)CI complexes are probably four coordinate and square planar, the tridentate ligand being coordinated via the two thiocarbamate sulphur atoms and the nitrogen atom of the piperidinium group. 相似文献
84.
The study of mixed-ligand complexes [Cux(phen)yLz] (where phen stands for 1,10-phenanthroline and L for aliphatic acids, aromatic acids, amino acids and phenols in the ratio of 1 : 1 : 1 and 1 : 2 : 1) has been made at three different temperatures, namely 30, 35 and 40°C. It is observed that all the complexes follow a partictiar reaction mechanism with temperature, and the half-wave potential shifts towards the more positive side with rise of temperature, indicating easier reduction. Besides the formal rate constant, the activation energy of diffusion, ED, has been calculated for each system. The effect of activation energy and the energy of rearrangement of electronic configuration of the depolarizer has been discussed against availability of the redox orbital for the electroreduction process. 相似文献
85.
Amarendra Patra Alok K. Mitra Saroj Ghosh Amitava Ghosh A. K. Barua 《Magnetic resonance in chemistry : MRC》1981,15(4):399-400
Carbon-13 NMR signal assignment of a number of polyoxygenated triterpenes of the olean-12-ene and urs-12-ene series, carried out by considering the changes in chemical shift produced by the change of oxygenation pattern(s), and using methyl oleanolate as a model, are reported. 相似文献
86.
Bould J Dörfler U Rath NP Barton L Kilner CA Londesborough MG Ormsby DL Kennedy JD 《Dalton transactions (Cambridge, England : 2003)》2006,(31):3752-3765
In an attempt to build up borane-based multicluster assemblies, thermolysis of [6,9-(SMe2)2-arachno-B10H12] 1 in inert hydrocarbon solution, followed by chromatographic separation, has resulted in the isolation not only of the previously established single-cluster product from this reaction, [5-(SMe2)-nido-B10H12] 2 (30%), but also the two two-cluster species [6,9-(SMe2)2-arachno-B10H11-1-(6-nido-B10H13)] 3 (20%) and [1,6-(nido-B10H13)2] 6 (ca. 0.5%) and the two three-cluster species [6,9-(SMe2)2-arachno-B10H10-1,5-(6-nido-B10H13)2] 4 (5%), characterized crystallographically, and [6,9-(SMe2)2-arachno-B10H10-1,3-(6-nido-B10H13)2] 5 (<1%), identified by NMR spectroscopy. An improved crystallographic investigation of [5-(SMe2)-nido-B10H12] 2 is also presented. The feasibility of the stability of species resulting from multiple adjacent substitution of nido-decaboranyl units on the [6,9-(SMe2)2-arachno-B10H12] skeleton is tested by DFT calculations. In an extension, to attempt the use of pre--linked two-cluster compounds as starting substrates, two-cluster [5-(SMe2)-4-(2-nido-B10H13)-nido-B10H11] 7 (0.6%) has been isolated from the reaction of SMe2 with [1,5-(nido-B10H13)2], other identified products being compound 1 (39%) and compound 3 (10.5%). 相似文献
87.
S. Dechoudhury Vaishali Naik Manas Mondal Hemendra Kumar Pandey Avik Chatterjee Dirtha Sanyal Debasis Bhowmick Alok Chakrabarti 《Pramana》2010,75(3):485-499
The design of a medium energy beam transport (MEBT) line comprising of a re-buncher and four quadrupoles, two upstream and
the other two downstream of the re-buncher, has been presented. The design was done to ensure almost 100% transport of heavy-ion
beams of about 99 keV/u energy from RFQ having a q/A not less than 1/14 through the re-buncher and then through IH Linac of about 0.6 m length in which beam would be accelerated
to about 185 keV/u. The re-buncher has been designed to operate at 37.8 MHz, the resonating frequency of both the RFQ and
the IH Linac. The entire beam line has been installed and recently O5+ beam from RFQ has been transported through the re-buncher and subsequently accelerated in the IH Linac successfully. 相似文献
88.
The effect of gamma irradiation on MOS devices prepared under different oxidation conditions Is investigated. The C-V characteristics of the devices are studied before and after exposing the latter with gamma radiations of CO60 (1.17 and 1.33 MeV gamma rays). For MOS transistor (n-channel depletion type devices) the C-V characteristics change slightly towards the negative voltage axis and the Cmin also decreases after Irradiation. For MOS capacitor (wet oxide) there is a change from high frequency C-V characteristics to low frequency C-V characteristics. In the case of a MOS capacitor (HCl grown) breakdown occurs relatively at lower voltage. 相似文献
89.
This article is concerned with a boundary-field equation approach to a class of boundary value problems exterior to a thin domain. A prototype of this kind of problems is the interaction problem with a thin elastic structure. We are interested in the asymptotic behavior of the solution when the thickness of the elastic structure approaches to zero. In particular, formal asymptotic expansions will be developed, and their rigorous justification will be considered. As will be seen, the construction of these formal expansions hinges on the solutions of a sequence of exterior Dirichlet problems, which can be treated by employing boundary element methods. On the other hand, the justification of the corresponding formal procedure requires an independence on the thickness of the thin domain for the constant in the Korn inequality. It is shown that in spite of the reduction of the dimensionality of the domain under consideration, this class of problems are, in general, not singular perturbation problems, because of appropriate interface conditions. 相似文献
90.