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931.
932.
933.
934.
Zhou S 《The Journal of chemical physics》2004,121(2):895-901
A recently proposed parameter free version of a Lagrangian theorem-based density functional approximation (LTDFA) [S. Zhou, Phys. Lett. A 319, 279 (2003)] for hard-sphere fluid is applied to hard-core attractive Yukawa model fluid by dividing bulk second-order direct correlation function (DCF) of fluid under consideration into hard-core part and tail part. The former is treated by the parameter free version of the LTDFA, while the tail part is treated by second-order functional perturbation expansion approximation as done in a recent partitioned DFA [S. Zhou, Phys. Rev. E 68, 061201 (2003)]. Two versions of mean spherical approximation (MSA) for the bulk second-order DCF are employed as input, one is the less accurate plain MSA whose tail part of the second-order DCF is strictly independent of a density argument, the other is the more accurate inverse temperature expansion version of the MSA whose tail part is not strictly independent of the density argument. Calculational results indicate that prediction based on the plain MSA is far more accurate than that based on the inverse temperature expansion version of the MSA. The reason is considered to be that the partitioned DFA requires that the tail part is highly or completely independent of the density argument, the plain MSA, by assuming that the tail part is exactly the potential itself, embodies all of the nonlinearities into the hard-core part which can be treated satisfactorily by the parameter free version of the LTDFA. The present investigation results in a universal method for constructing DFA for nonuniform any nonhard-sphere interaction potential fluids. 相似文献
935.
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
936.
Lin Jia Hui Yang Jun Deng Junmei Chen Yuan Zhou Pan Ding Leigang Li Na Han Yanguang Li 《中国化学》2019,37(5):497-500
Electrocatalytic carbon dioxide reduction holds great promise for reducing the atmospheric CO2 level and alleviating the energy crisis. High‐performance electrocatalysts are often required in order to lower the high overpotential and expedite the sluggish reaction kinetics of CO2 electroreduction. Copper is a promising candidate metal. However, it usually suffers from the issues of poor stability and low product selectivity. In this work, bimetallic Cu‐Bi is obtained by reducing the microspherical copper bismuthate (CuBi2O4) for selectively catalyzing the CO2 reduction to formate (HCOO–). The bimetallic Cu‐Bi electrocatalyst exhibits high activity and selectivity with the Faradic efficiency over 90% in a wide potential window. A maximum Faradaic efficiency of ~95% is obtained at –0.93 V versus reversible hydrogen electrode. Furthermore, the catalyst shows high stability over 6 h with Faradaic efficiency of ~95%. This study provides an important clue in designing new functional materials for CO2 electroreduction with high activity and selectivity. 相似文献
937.
938.
{[Cu^Ⅱ(Hpb)(mal)]H=O}n (Hpb=2-2'-pyridylbenzimidazole, mal=maleic acid) is a helical chain-like polymer complex. In order to investigate the electronic structure of the complex, the monomer Cu^Ⅱ(Hpb)(mal) was obturated with different functional groups respectively. For these selective segments, the geometry optimizations were conducted by using hybrid DFT (B3LYP)methods to find that the structure obturated with H2O was better consistent with the experiment, and then this model would be used to latter calculations, such as the frontier molecular orbital and the NBO charge population analysis. In addition the magnetic behaviors of this complex were analyzed by experiments and the weak antiferromagnetic couple between copper(Ⅱ) ions was observed. The exchange coupling constant was calculated by DFT based on the spin broken symmetry formalism. The calculated coupling constants were in good agreement with the experimental data. 相似文献
939.
The reactions of transition metal salts with taurine 5‐chlorosalicylaldelyde Schiff base gave two complexes [Ni(TCSSB)(H2O)3].H2O (1) and [Cu(TCSSB)(H2O)2]2[Cu(TCSSB)2].6H2O (2) (TCSSB=taurine‐5‐chlorosalicylaldelyde Schiff base), which were characterized by elemental analysis and X‐ray diffraction analysis. The complex 1 crystallized in monoclinic system with space group P2 1/c, and a=1.4816(2) nm, b=1.3953(2) nm, c= 0.7466(1) nm, β= 100.499(3)°, V=1.5176(4) nm3, Z=4, and an infinite 3‐D network structure was formed by hydrogen bonds among sulfo group, crystal water and coordinated water. Complex 2 crystallized in triclinic system with space group P1 , with the cell parameters: a = 0.6413(2) nm, b= 1.4596(3) nm, c= 1.6188(4) nm, a= 102.473(5)°, β= 98.979(4)°, γ=101.739°, V=1.4165(6) nm3, Z=1. The coordination environment between Cu(1) and Cu(2) is different. Cu(1) is slightly distorted square pyramidal while Cu(2) is distorted square‐plane. The complex 1 is mononuclear while the complex 2 is made up of two coordinated subunits, namely [Cu(TCSSB)2] and [CU(TCSSB)(H2O)2]2. Besides that the TG‐DTG of the complex 1 was analyzed, the thermal decomposition reaction of the complex was studied under a non‐isothermal condition by TG‐DTG. The TG and DTG curves indicate that the complex was decomposed in three stages: . 相似文献
940.
When DNA is mixed with the cationic polyelectrolyte poly(diallyldimethyl ammonium chloride) (PDDA), the DNA/PDDA complex is formed instantaneously at room temperature. This complex is much more efficient in enhancing the fluorescence of Hoechst 33258 (H 33258) than DNA alone. Based on the interaction of H 33258 with the DNA/PDDA complex, a new fluorescence assay for DNA is described. At pH 7.3 in Tris-HCl buffered solution, the DNA/PDDA complex causes a sharp enhancement in fluorescence intensity of H 33258. Simultanously, the emission maximum wavelength of H 33258 blueshifts from 490nm to 450nm, while the excitation redshifts from 345 to 350nm. The calibration graphs for calf thymus DNA (ctDNA) and herring sperm DNA (hsDNA) are both linear up to 5.0µgmL–1 when the concentration of H 33258 and PDDA are fixed at 1.5×10–6 and 1.6×10–5molL–1, respectively. The method is specific for native DNA. The 3 detection limits for ctDNA and hsDNA are 1.8 and 5.6ngmL–1, respectively, i.e. much lower than in the presence of H 33258 alone. Four synthetic samples were determined satisfactorily. This method can also be developed to investigate the formation and the nature of the complexes between DNA and polycations, which have recently been widely applied in some fields such as genetic engineering and gene therapy. 相似文献