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991.
Chun‐Bo Liu Guang‐Bo Che Chuan‐Bi Li Yun‐Cheng Cui 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(4):m153-m155
An in situ reaction under hydrothermal conditions leads to the formation of the title compound, diaqua(pyridine‐2‐carboxylato)(pyridine‐2,6‐dicarboxylato)indium(II) trihydrate, [In(C6H4NO2)(C7H3NO4)(H2O)2]·3H2O, in which the central InIII atom is seven‐coordinated by one pyridine‐2,6‐dicarboxylate ligand, one pyridine‐2‐carboxylate ligand and two water molecules in a pentagonal–bipyramidal coordination environment. An indium(III)–water chain based on an unusual water pentamer is observed. 相似文献
992.
Brownian dynamics (BD) and molecular dynamics (MD) simulations and electrostatic calculations were performed to study the binding process of kappa-PVIIA to the Shaker potassium channel and the structure of the resulting complex. BD simulations, guided by electrostatic interactions, led to an initial alignment between the toxin and the channel protein. MD simulations were then carried out to allow for rearrangements from this initial structure. After approximately 4 ns, a critical "induced fit" process was observed to last for approximately 2 ns. In this process, the interface was reorganized, and side chains were moved so that favorable atomic contacts were formed or strengthened, while unfavorable contacts were eliminated. The final complex structure was stabilized through electrostatic interactions with the positively charged side chain of Lys7 of kappa-PVIIA deeply inserted into the channel pore and other hydrogen bonds and by hydrophobic interactions involving Phe9 and Phe23 of the toxin. The validity of the predicted structure for the complex was assessed by calculating the effects of mutating charged and polar residues of both the toxin and the channel protein, with the calculated effects correlating reasonably well with experimental data. The present study suggests a general binding mechanism, whereby proteins are pre-aligned in their diffusional encounter by long-range electrostatic attraction, and nanosecond-scale rearrangements within the initial complex then lead to a specifically bound complex. 相似文献
993.
The results from the measurement of the fluorescence spectrum showing the binding characteristics of acridine orange (AO) and bovine serum albumin (BSA) are reported. It was found that the equilibrium constant k=4848.64 l mol−1, and the number of binding sites n=0.82. Based on the mechanism of the Forster energy transference, the transfer efficiency of energy and distance between the acceptor AO and BSA were found. The interaction between AO and BSA have been verified as consistent with the static quenching procedure and the quenching mechanism is related to the energy transfer. 相似文献
994.
Wan Yong Feng Moshe Goldenberg Chava Lifshitz 《Journal of the American Society for Mass Spectrometry》1994,5(8):695-703
Thermal reactions of proton-bound dimers, (CH3CN)2H +, (CH3OCH3)2H +, and (CH3COCH3)2H+, were studied using a selected ion flow tube. Reactions observed include association, switching, and proton transfer. The association channel was observed only for base molecules that had hydrogen bonding protons such as NH3, CH3NH2, (CH3)2NH, and CH3OH. An association-insertion mechaniSoc was proposed in which the central proton of the symmetrically bound dimers is replaced by a protonated base, for example, NH 4 + . These reactions are relatively slow, which demonstrates a central barrier along the potential energy surface. Ether-containing dimers do not demonstrate this insertion reaction, except for diethers, for example, CH3OCH2CH2OCH3, which can form stable bicyclic structures. Dimers such as (HCOOH)2H+, which possess hydrogen bonding protons in the periphery, undergo switching reactions with ammonia and no insertion. 相似文献
995.
合成了硫氰酸铈(Ⅲ)与三缩四乙醇配合物[Ce(C_8H_(18)O_5)(NCS)_3(H_(2)O)].晶体结构分析表明,该配合物晶体属三斜晶系,P(?)空间群.晶胞参数:a=0.8816(3)nm,b=1.0465(2)nm,c=1.2490(2)nm,α=86.46(1)°,β=70.90(2)°,γ=66.37(2)°,ν=0.9943nm~(3),Z=2.D_(计算)=1.769cm~(3),最终偏差因子R=0.049. 相似文献
996.
A MORPHOLOGICAL STUDY OF POLY(DIVINYLBENZENE-co-ACRYLIC ACID) IN CROSSLINKING PRECIPITATION POLYMERIZATION 总被引:1,自引:0,他引:1
Feng Bai Xin-lin Yang Wen-qiang Huang 《高分子科学》2006,(2):163-171
Divinylbenzene-80 (DVB-80) and polar monomer acrylic acid (AA) having hydrogen bonding at a total monomer loading of 5 vol% were precipitated-copolymerized in a variety of organic solvents with 2,2'-azobis(isobutyronitrile) (AIBN) as initiator. The experiments were investigated from a two-dimensional matrix, i.e., the actual crosslinking degree of DVB varying from 0 to 80% and the solvent composition varying from 0 to 100% of toluene mixture with acetonitrile, when the mixture of acetonitrile and toluene was used as the reaction solvent. Under various reaction conditions, six distinct morphologies including soluble polymers, swellable microgels, coagulum, irregular microparticles, and nano-/micrometer microspheres were formed and the structures of these polymer architectures were described. A morphological map was utilized to discuss the effects of both crosslinking degree of DVB and composition of solvent on the transitions between morphology domains. The results demonstrated that the microspheres are formed by an internal contraction due to the marginal solvency of the continuous phase and the crosslinking of the polymer network through the covalent bonding from DVB as well as the interchain hydrogen-bonding between the carboxylic acid units. 相似文献
997.
Synthesis and characterization of the ligand, [2-tetradecyl-3,6,9-tris(carboxymethyl)-3,6,9-triazaundecan-1,11-dioic acid, H5L] and its Gd(Ⅲ) chelate are described. Protonation constants for H5L (lgKiH = 10.80, 8.40, 4.30, 2.80, 2.15) and the stability constant for GdL2- (lgKGdL2-= 22.75) were determined by potentiometric titration and are similar with the related values of DTPA and Gd-DTPA respectively. The results obtained show that the basicity of the ligand and the stability constant of its Gd(Ⅲ) chelate are not obviously altered after introduction of a linear chain tetradecyl group at the terminal acetic acid residue of DTPA. 相似文献
998.
α-Al2O3纳米粒子对Co-Ni合金异常共沉积电化学行为的影响 总被引:1,自引:0,他引:1
为了研究在电化学复合共沉积过程中,惰性纳米粒子和金属离子、电极表面的相互作用,以及由此产生的对合金电化学共沉积行为的影响.本文从两个吸附过程出发: 电解液中的金属离子和H+在纳米粒子表面的吸附;纳米粒子迁移到阴极表面,在电极表面的吸附.采用Zeta电势和稳态极化以及电化学交流阻抗(EIS)研究了纳米Al2O3粒子和电解液中的金属离子,和电极表面的相互作用,进而分析了纳米粒子对Co2+和Ni2+还原沉积的影响规律.通过对阻抗数据的拟合,讨论了Al2O3纳米粒子对等效电路中各物理参数的影响.在H+和不同金属离子在纳米粒子上发生竞争吸附的基础上,提出了纳米粒子和合金共沉积的可能反应历程. 相似文献
999.
A new family of bifunctional catalysts (N-oxides-Ti(OiPr)4 (2:1)) containing a Lewis acid and a Lewis base was developed and applied to the catalytic cyanosilylation of ketones. Utilizing rac((1R,2S) and (1S,2R))-1-(2′-pyridylmethyl)-2-diphenylhydroxymethylpyrrolidine N-oxide-titanium (2:1) complex and N-benzyl-diethanolamine N-oxide-titanium (2:1) complex as catalysts, the cyanosilylation products were obtained in 42-97% yield. Based on experimental phenomena and kinetic studies, a catalytic cycle was proposed to explain the remarkable activities of these catalysts. Investigations indicated that rac((1R,2S) and (1S,2R))-1-(2′-pyridylmethyl)-2-diphenylhydroxymethylpyrrolidine N-oxide-titanium (2:1) complex and N-benzyl-diethanolamine N-oxide-titanium (2:1) complex should promote the reaction via a dual activation of the ketone by the titanium and TMSCN by the N-oxide. 相似文献
1000.
Tetsuro Fujita 《中国化学快报》2007,18(2):175-177
A new highly conjugated alkaloid of veratramine type, 225,25S,5α-veratramine-7(8),12(14)-diene-3β,13β,23β-triol-6-one (1), was isolated from the bulbs of Fritillaria hupehensis Hsiao et K.C. Hsia. Its structure was determined on the basis of spectroscopic evidences. 相似文献