全文获取类型
收费全文 | 502篇 |
免费 | 21篇 |
专业分类
化学 | 356篇 |
晶体学 | 2篇 |
力学 | 16篇 |
数学 | 36篇 |
物理学 | 113篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 12篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 12篇 |
2016年 | 22篇 |
2015年 | 13篇 |
2014年 | 16篇 |
2013年 | 30篇 |
2012年 | 32篇 |
2011年 | 42篇 |
2010年 | 23篇 |
2009年 | 16篇 |
2008年 | 32篇 |
2007年 | 25篇 |
2006年 | 20篇 |
2005年 | 25篇 |
2004年 | 17篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 12篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有523条查询结果,搜索用时 31 毫秒
101.
More Krantiveer V. Dhodamani Ananta G. Dongale Tukaram D. Panda Dillip K. Delekar Sagar D. 《Journal of Solid State Electrochemistry》2022,26(4):1075-1084
Journal of Solid State Electrochemistry - Ti1-xFexO2-δ nanoparticles (NPs) with varying content of Fe (III) ions (x = 0.008 to 0.024 and δ =0.5x) were synthesized using sol-gel method at... 相似文献
102.
Jena Sudipta Ray Asit Sahoo Ambika Das Prabhat Kumar Champati Bibhuti Bhusan Nayak Sanghamitra Panda Pratap Chandra 《Chemistry of Natural Compounds》2022,58(3):550-552
Chemistry of Natural Compounds - 相似文献
103.
2-Borylpyrrole was prepared from 2-iodopyrrole almost quantitatively and then reacted with dihaloarenes under typical reaction conditions of Suzuki-Miyaura cross coupling to give bis(pyrrol-2-yl)arenes in good yields, while the cross coupling reaction of 2-iodopyrrole with 1,4-phenylenebisboronic acid was susceptible to oxidative self-coupling to produce 4,4′-bis(pyrrol-2-yl)biphenyl as a byproduct. These bis(pyrrol-2-yl)arenes showed strong fluorescence. 相似文献
104.
Magnetic moments of decuplet baryons have been calculated in a relativistic independent quark model with a phenomenological
potential in equally mixed scalar-vector harmonic form. Such a model has been successful in describing wide ranging hadronic
phenomena in mesonic and baryonic sectors. Using the solutions of the constituent quark orbitals with the model parameters
taken from its earlier applications, the magnetic moments of decuplet baryons Δ++ and Ω− have been obtained which are in good agreement with the available experimental data. However, the agreement is found to be
much better when the magnetic moment ratios such as μδ++/μ
p and μΩ-/μΛ are considered. Model predictions for the magnetic moments of other decuplet baryons together with the charge radii have
also been calculated which may be verified in future experiments. 相似文献
105.
Double barrier resonant tunneling diode using annealing induced diffusion modified quantum well is proposed as a viable alternative
to that using parabolic quantum well which requires complex techniques to fabricate it. The transmission coefficients are
calculated using the hybrid incremental airy function plane wave approach. The room temperature current-voltage characteristics
have been calculated using transmission coefficients. The current-voltage characteristics are found to be similar in both
diodes. 相似文献
106.
Nonlinear finite element analysis of functionally graded plates integrated with patches of piezoelectric fiber reinforced composite 总被引:1,自引:0,他引:1
In this paper, a nonlinear static finite element analysis of simply supported smart functionally graded (FG) plates in the presence/absence of the thermal environment has been presented. The substrate FG plate is integrated with the patches of piezoelectric fiber reinforced composite (PFRC) material which act as the distributed actuators of the plate. The material properties of the FG substrate plate are assumed to be temperature dependent and graded along the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The derivation of this nonlinear thermo-electro-mechanical coupled finite element model is based on the first order shear deformation theory and the Von Karman type geometric nonlinearity. The numerical solutions of the nonlinear equations of the finite element model are obtained by employing the direct iteration method. The numerical illustrations suggest the potential use of the distributed actuator made of the PFRC material for active control of nonlinear deformations of smart FG structures. The effects of volume fraction index of the FG material of the substrate plates and the locations of the PFRC patches on the control authority of the patches are investigated. Emphasis has also been placed on investigating the effect of variation of piezoelectric fiber orientation angle in the PFRC patches on their actuation capability for counteracting the large deflections of FG plates. 相似文献
107.
Raj Gandhi Subhendra Mohanty Tarun Souradeep S Agarwalla K Bhattacharya B Brahmachari R Crittenden S Goswami P Ghoshal M Lindner H S Mani S Mitra S Pascoli S Panda R Rangarajan S Ray T Roy Choudhury R Saha S Sarkar A Srivastava R Sheth S Uma Sankar U Yajnik 《Pramana》2006,67(4):735-742
The working group on astroparticle and neutrino physics at WHEPP-9 covered a wide range of topics. The main topics were neutrino
physics at INO, neutrino astronomy and recent constraints on dark energy coming from cosmological observations of large scale
structure and CMB anisotropy. 相似文献
108.
Stereochemically defined enantioenriched molecules were, are and will always be playing a pivotal role in the development of novel pharmaceutical agents. On this line, compounds having tertiary benzylic stereocenter are of special note. This has led to an increase in the development of novel synthetic strategies for accessing molecules having this structural moiety. The current critical discussion proposes to describe the various synthetic methodologies for the enantioselective synthesis of diaryl methanols, diarylmethyl amines and other related scaffolds with tertiary benzylic stereogenic center that came up during 1995–2016. Through this critical view, we would not only like to give the readers a brief outlook on the different techniques that can be followed for the synthesis of a vast array of entities having this structural core, but also would like to highlight the limitations the protocols that need to be addressed. 相似文献
109.
The concerned azooximes (L1OH, 1) are of type p-X-C6H4C(N2Ph)(NOH) (X = H, Me, Cl). The reaction of [Re(MeCN)Cl3(PPh3)2] with [Ag(L1OH)(L1O)] in cold dichloromethane-acetonitrile solvent has furnished the green colored ionized azoimine complex [ReV(O)Cl(PPh3)2(L1)](PF6), 2. In effect L1O- has undergone oxidative addition, the oxygen atom being transferred to the metal site. Upon treatment of [ReV(NPh)Cl3(PPh3)2] with L1OH in solution, the neutral azoimine complex [ReV(NPh)Cl3(L1H)], 3, resulted due to the spontaneous transfer of the oxime oxygen atom to a PPh3 ligand, which is eliminated as OPPh3. In contrast, the oxime of 2-acetylpyridine (L2OH, 4) did not undergo oxygen atom transfer and simply afforded the imine-oxime complex [ReV(NC6H4Y)Cl2(PPh3)(L2O)], 5, upon reacting with [ReV(NC6H4Y)Cl3(PPh3)2] (Y = H, Me, Cl). The spectral and electrochemical properties of 2, 3, and 5 and the structures of three representative compounds are reported. In the cation of 2 (X = H) the two PPh3 ligands lie trans to each other and the equatorial plane is defined by the five-membered azoimine chelate ring and the oxo and chloro ligands. The oxo ligand which forms a model triple bond (Re-O length 1.616(6) A) lies cis to the imine-N atom. In 3 (X = Cl) the ReCl3 fragment has meridional geometry and the imido nitrogen lies trans to the imine nitrogen of the planar azoimine chelate ring. In 5 x H2O (Y = Me), the Cl, oximato-N, and P atoms define an equatorial plane and the pyridine-N lies trans to the imido-N. The water of crystallization is hydrogen bonded to the oximato oxygen atom (O...O, 2.829(5) A). Reaction models in which chelation of the azooxime precedes oxygen atom transfer are proposed on the basis of oxophilicity of trivalent rhenium, Lewis acid activity of pentavalent rhenium, electron withdrawal by the azo group, and observed relative disposition of ligands in products. 相似文献
110.
Reacting Re(CO)5Cl with the azopyridine ligand (1) (L) in boiling benzene afford the complex Re(CO)3Cl(L), (2) in excellent yield [L=2-(p-Cl-C6H4NN)C5H4N]. The chelation of the azopyridine ligand accompanied by displacement of the two carbon monoxide ligands furnish a five-membered chelate ring. Structure determination of complex (2) has revealed a distorted octahedral ReC3N2Cl coordination sphere. The Re–N(pyridine) and, Re–N(azo) distances are 2.158(3) and 2.153(6) Å respectively, and the N–N length [1.273(4) Å], implicate relatively weak Re-azo(π*) back–bonding. The Re(CO)3Cl(L) lattice consists of C–H...Cl hydrogen bonding and Cl...O non-bonded interactions constituting a supramolecular network. Extended Hückel calculations reveal that the LUMO of Re(CO)3Cl(L) is Ca. 57% azo in character. One-electron quasireversible electrochemical reduction of the complex occurs near −0.3 V versus Saturated Calomel electrode(s.c.e.) The redox orbital is believed to belong to the above noted LUMO. Electrogenerated Re(CO)3Cl(L•–) underwent spontaneous solvolytic chloride displacement in MeCN, resulting in the isolation of Re(CO)3(MeCN)(L•–). The latter complex in turn reacted with imidazole and triphenylphosphine, furnishing Re(CO)3(C3H4N2)(L•–) and Re(CO)3(PPh3)(L•–), respectively. The pattern of carbonyl stretching frequencies of these radical anion complexes is similar to that of Re(CO)3Cl(L) but with shifts to lower frequencies by 10–20 cm−1. All three radical anion systems are one-electron paramagnetic (1.7–1.8 μB). The unpaired electron is primarily localized on the azoheterocycle ligand in a predominantly azo-π* orbital, but a small metal contribution (185, 187Re, I=5/2) is also present. Thus Re(CO)3(MeCN)(L•–) and Re(CO)3(C3H4N2)(L•–) display six-line e.p.r. spectra (A ˜ 28 G). The line shapes and intensities are characteristic of the presence of g-strain. In the case of Re(CO)3(PPh3)(L•–) seven nearly equispaced lines are observed due to virtually equal coupling between the metal and 31P (I=&frac;) nuclei. The g-values of the radical species are slightly higher than the free-electron value of 2.0023. 相似文献