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181.
A. K. Mitra V. B. Gawandi K. George H. Mohan T. Mukherjee 《Research on Chemical Intermediates》2008,34(1):85-92
5,8-dihydroxy-1,4-dihydro-1,4-methanonaphthalene (DDMN), a substituted phenol, is synthesized by reduction of a cyclic dione,
1,4,4a,8a-tetrahydro-endo-1,4-methano-naphtha-5,8-dione (THMND). Pulse radiolysis technique has been employed to understand
the nature of transient species formed on reaction of radiolytic species of water radiolysis with DDMN.•OH radicals were observed to react with DDMN with a bimolecular rate constant of 1.5×1010 dm3 mol−1 s−1. Inhibition of radiation induced lipid-peroxidation by DDMN was studied in rat liver microsomes by assessing the formation
of thiobarbituric acid reactive substances (TBARS). It was found to be strongly inhibitory. The results suggest that DDMN
has very good antioxidant activity and may possibly emerge as a good radio-protector. 相似文献
182.
Thakurta S Chakraborty J Rosair G Tercero J El Fallah MS Garribba E Mitra S 《Inorganic chemistry》2008,47(14):6227-6235
Two new Cu(II) linear trinuclear Schiff base complexes, [Cu3(L)2(CH3COO)2] (1) and [Cu3(L)2(CF3COO)2] (2), have been prepared using a symmetrical Schiff base ligand H2L [where H2L = N,N'-bis(2-hydroxyacetophenone)propylenediimine]. Both of the complexes have been characterized by elemental analyses, Fourier transform IR, UV/vis, and electron paramagnetic resonance spectroscopy. Single-crystal X-ray structures show that the adjacent Cu(II) ions are linked by double phenoxo bridges and a mu(2)-eta(1):eta(1) carboxylato bridge. In each complex, the central copper atom is located in an inversion center with distorted octahedral coordination geometry, while the terminal copper atoms have square-pyramidal geometry. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit a distinct antiferromagnetic interaction of J = -36.5 and -72.3 cm(-1) for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) and continuous-shape measurement (CShM) studies have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the antiferromagnetic behavior shown by the complexes. 相似文献
183.
A new electron precise, six-electron, sulfide-bicapped trinuclear cluster complex [Et4N]4[Mo(IV)3(mu3-S)2(mnt)6] (1) has been synthesized, where each Mo(IV) atom is seven coordinated. Identical reaction conditions yielded a dimeric complex, [PNP]2[W(V)2(mu2-S)2(mnt)4] (2) from the starting W(IV) analogue due to oxidation by sulfur formed by the auto-oxidation of H2S. Two stepwise reversible reductions and no oxidation of 2 as observed by cyclic voltammetry are correlated with the nonbonding nature of the lowest unoccupied molecular orbital and deeply buried highest occupied molecular orbital by theoretical calculations at the density-functional theory level. 相似文献
184.
Reaction of [RuIII(edta)(H2O)]- with H2O2 in aqueous solution. Kinetic and mechanistic investigation
The reaction of [Ru(III)(edta)(H(2)O)](-) (1) (edta = ethylenediaminetetraacetate) with hydrogen peroxide was studied kinetically as a function of [H(2)O(2)], temperature (5-35 degrees C) and pressure (1-1300 atm) at a fixed pH of 5.1 using stopped-flow techniques. The reaction was found to consist of two steps involving the rapid formation of a [Ru(III)(edta)(OOH)](2-) intermediate which subsequently undergoes parallel heterolytic and homolytic cleavage to produce [(edta)Ru(V)=O](-) (45%) and [(edta)Ru(IV)(OH)](-) (55%), respectively. The water soluble trap, 2,2'-azobis(3-ethylbenzithiazoline-6-sulfonate) (ABTS), was employed to substantiate the mechanistic proposal. Reactions were carried out under pseudo-first conditions for [ABTS] > [HOBr] > [1], and were monitored as a function of time for the formation of the one-electron oxidation product ABTS* (+). A detailed mechanism in agreement with the rate and activation parameters is presented, and the results are discussed with reference to data reported for the corresponding [Fe(III)(edta)(H(2)O)](-)/H(2)O(2) system. 相似文献
185.
186.
Subhra Basak Soma Sen Sambuddha Banerjee Samiran Mitra Georgina Rosair M.T. Garland Rodriguez 《Polyhedron》2007
Three new dinuclear Zn(II) complexes [Zn(L)(μ1,1-N3)Zn(L)(N3)] · 1.5H2O (1), [Zn(L)(μ1,1-NCO)Zn(L)(NCO)] · 1.5H2O (2) and [Zn(L)(μ1,1-NCS)Zn(L)(NCS)(OH2)] (3) have been synthesized from a potentially tetradentate N2O2-donor Schiff base ligand LH, [LH = (OCH3)(OH)C6H3CHN(CH2)2N(CH3)2], which is the condensation product of o-vanillin and 2-dimethylaminoethylamine. All the three complexes 1, 2 and 3 have been characterized by elemental analysis, IR and 1H NMR spectroscopy, TGA and fluorescence studies. Finally, their structures have been established by the single crystal X-ray diffraction method. Structural studies reveal that in complexes 1, 2 and 3 the two Zn(II) centers are held together by a μ2-phenolato oxygen atom and also by an end-on pseudohalide nitrogen (azide for 1; cyanate for 2; thiocyanate for 3) atom. Among the two deprotonated Schiff base ligands present in each complex, one acts as a tetradentate ligand (N2O2 donor set) while the other acts as a tridentate ligand (N2O donor set), having a non-coordinated methoxy group. All the synthesized complexes display intraligand 1(π–π∗) fluorescence and can potentially serve as photoactive materials. 相似文献
187.
Merca A Haupt ET Mitra T Bögge H Rehder D Müller A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(27):7650-7658
Spherical capsules of the type [{(Mo)Mo(5)}(12){Mo(2)(ligand)}(30)](n-) exhibiting 20 {Mo(9)O(9)} pores with crown ether functions allowed us to perform a sophisticated study of the title phenomenon based on synthetic work as well as NMR spectroscopy. The pores of the host system interact in solution specifically with guests that can be noncovalently bonded, such as formamidinium and acetamidinium cations, while having different affinities to the pores. The exchange between the guest species present in solution and in the pores was investigated, including, besides the extreme scenarios of complete pore closing and complete opening, that of stepwise pore plugging. Because of this option it was possible to model for the first time passive transmembrane cation transport based on gated pores/channels. These have the appropriate dimensions and can even adopt different structure flexibilities in response to different cations. The present investigation is based on related syntheses as well as on numerous detailed (7)Li NMR studies of Li(+) transport/exchange equilibria in dependence of the pore environment/guest situations. One compound containing capsules with sulfate ligands (2) could be obtained in which all the pores are plugged with formamidinium cations and another corresponding one was obtained with additionally encapsulated Ca(2+) ions (3); these were taken up after temporary release of some of the formamidinium plugs/guests upon short heating of the related solution. 相似文献
188.
Patil KR Sathaye SD Hawaldar R Sathe BR Mandale AB Mitra A 《Journal of colloid and interface science》2007,315(2):747-752
The simple recrystallization process is innovatively used to obtain the nanoparticles of copper phthalocyanine by a simple method. Liquid-liquid interface recrystallization technique (LLIRCT) has been employed successfully to produce small sized copper phthalocyanine nanoparticles with diameter between 3-5 nm. The TEM-SAED studies revealed the formation of 3-5 nm sized with beta-phase dominated mixture of alpha and beta copper phthalocyanine nanoparticles. The XRD, SEM, and the UV-vis studies were further carried out to confirm the formation of copper phthalocyanine thin films. The cyclic voltametry (CV) studies conclude that redox reaction is totally reversible one electron transfer process. The process is attributed to Cu(II)/Cu(I) redox reaction. 相似文献
189.
Mitra RK Sinha SS Pal SK 《Langmuir : the ACS journal of surfaces and colloids》2007,23(20):10224-10229
Human serum albumin (HSA) is known to undergo both reversible and irreversible thermal unfolding and refolding, depending upon the experimental conditions (end temperature) at neutral pH. In this report we have used high precision densimetric and ultrasonic measurements to determine the apparent specific volume (phi v) and compressibility (phi k) of HSA at different unfolded and refolded states at two different end temperatures, 55 degrees C and 70 degrees C. The unfolded and refolded states were characterized using dynamic light scattering (DLS), circular dichroism (CD), picosecond-resolved fluorescence decay, and anisotropy of the single-tryptophan residue in HSA (Trp214). Both the unfolded states were allowed to refold by cooling wherein the former and latter processes were found to be reversible and irreversible, respectively, in nature. The results obtained from the densimetric and ultrasonic measurements reveal that the apparent specific volume and compressibility of the protein in the reversible protein unfolding process is preserved upon restoration of HSA to ambient temperature. However, a significant change in phi v and phi k occurs in the process of irreversible protein refolding (from 70 to 20 degrees C). The experimental observation is rationalized in terms of the exposure of domain IIA to an aqueous environment, resulting in the swelling of the protein to a higher hydrodynamic diameter. Our studies attempt to explore the extent of hydration associated with the structural integrity of the popular protein HSA. 相似文献
190.