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991.
The reaction of ketenimines with heterocyclic N-oxides yields N-substituted oxindoles. Hydrolysis of these adducts or acid work-up of the original reaction mixtures leads directly to oxindoles in which the nitrogen atom is unsubstituted. 相似文献
992.
We have calculated the electronic states of Rb(2) by multireference configuration interactions using the averaged relativistic effective small-core potential and the core-polarization potential. The potential energy curves for a large number of states dissociating into from 5s+5s up to 7s+5s asymptotic limits are calculated and the spectroscopic constants are reported. The spin-orbit effects for the states dissociating into 5p+5s and 4d+5s are calculated using the effective spin-orbit potential. The results are compared with available experimental data and other theoretical works. Copyright 2001 Academic Press. 相似文献
993.
Sodium dodecyl sulfate-capillary gel electrophoresis of polyethylene glycolylated interferon alpha 总被引:3,自引:0,他引:3
Sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) using a hydrophilic replaceable polymer network matrix was applied to characterize the polyethylene glycol(PEG)ylated interferon alpha (PEG-IFN). The SDS-CGE method resulted in a clearer resolution in both the PEG-IFN species and the native IFN species. The distribution profile of PEGylation determined by SDS-CGE was consistent with that obtained by SDS-polyacrylamide gel electrophoresis (PAGE) with Coomassie blue or barium iodide staining. The result was also compared using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry. SDS-CGE was also useful for monitoring the PEGylation reaction to optimize the reaction conditions, such as reaction molar ratio. This study shows the potential of SDS-CGE as a new method for characterizing the PEGylated proteins with advantages of speed, minimal sample consumption and high resolution. 相似文献
994.
Kim SK Lee SH Lee JY Lee JY Bartsch RA Kim JS 《Journal of the American Chemical Society》2004,126(50):16499-16506
A new fluorescent chemosensor with two different types of cation binding sites on the lower rims of a 1,3-alternate calix[4]arene (1) is synthesized. Two pyrene moieties linked to a cation recognition unit composed of two amide groups form a strong excimer in solution. For 1, the excimer fluorescence is quenched by Pb2+, but revived by addition of K+ to the Pb2+ ligand complex. Thus, metal ion exchange produces an on-off switchable, fluorescent chemosensor. Computational results show that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of the two pyrene moieties interact under UV irradiation of 1 and its K+ complex, while such HOMO-LUMO interactions are absent in the Pb2+ complex. 相似文献
995.
Sung Ho Wang 《Transactions of the American Mathematical Society》2004,356(10):4055-4073
Conservation laws of third order quasi-linear scalar evolution equations are studied via exterior differential system and characteristic cohomology. We find a subspace of 2-forms in the infinite prolongation space in which every conservation law has a unique representative. Analysis of the structure of this subspace based upon the symbol of the differential equation leads to a universal integrability condition for an evolution equation to admit any higher order (weight) conservation laws. As an example, we give a complete classification of a class of evolution equations which admit conservation laws of the first three consecutive weights , , . The differential system describing the flow of a curve in the plane by the derivative of its curvature with respect to the arc length is also shown to exhibit the KdV property, i.e., an infinite sequence of conservation laws of distinct weights.
996.
Sharma PA Ahn JS Hur N Park S Kim SB Lee S Park JG Guha S Cheong SW 《Physical review letters》2004,93(17):177202
The thermal conductivity of the magnetically frustrated, ferroelectric YMnO3 exhibits an isotropic suppression in the cooperative paramagnetic state, followed by a sudden increase upon magnetic ordering. This unprecedented behavior without an associated static structural distortion probably originates from the strong dynamic coupling between acoustic phonons and low-energy spin fluctuations in geometrically frustrated magnets. The replacement of magnetic Ho for Y at the ferroelectrically active site results in an even larger effect, suggestive of the strong influence of multiferroicity. 相似文献
997.
Il Yoon Ki-Min Park Jong Hwa Jung Jineun Kim Sung Bae Park Shim Sung Lee 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(1-2):45-50
The S2O2-donor macrocycle, L(5,8-dioxa-2,11-dithia-[12]-o-cyclophane or 3,4-benzo-1,6-dithia-9,12-dioxocyclo-tetradecane-3-ene) was synthesized by ring closure reaction of 2,2'-(ethylenedioxy)diethanethiol with ,'-dibromo-o-xyleneunder high dilution and crystallized from methanol. The X-ray structure of L has a C2 axis and is shown to have two S atoms oriented exodentate and two O atoms positionedendodentate to the ring cavity. Reaction of AgNO3 with L affords monomeric [Ag(L)(NO3)], (1)in which the Ag atom is in a distorted trigonal plane coordinated by two S atoms in a ring and to one O atom from the NO3
- ion. The behavior of complex 1 in solution was also characterized by NMR titration. Reaction between K2PtCl4 and L affords [Pt(L)Cl2], (2) in which the Pt atom has a distorted square-planar environment, coordinated to two S atoms of Land to two Cl- ions in a cis arrangement. 相似文献
998.
Man Seok Han Byung Gwon Lee Byoung Sung Ahn Kun You Park Suk In Hong 《Reaction Kinetics and Catalysis Letters》2001,73(1):33-38
Dimethyl carbonate (DMC) was synthesized by the ester exchange reaction of ethylene carbonate and methanol. K2 CO3 , KOH, LiOH and NaOH were used as catalysts for DMC synthesis and their catalytic abilities were compared in terms of kinetics. LiOH showed the best reaction rate among the catalysts. The rate constant was estimated to be 0.02538 (dm 3 /mol) 0.21 /min at 298 K. 相似文献
999.
Yeong‐Soon Gal Sung‐Ho Jin Jong‐Wook Park Won‐Chul Lee Hyo‐San Lee Sang‐Youl Kim 《Journal of polymer science. Part A, Polymer chemistry》2001,39(23):4101-4109
A fluorene‐containing spiro‐type conjugated polymer, poly(dipropargylfluorene), was synthesized via the cyclopolymerization of dipropargylfluorene by Mo‐ and W‐based transition‐metal catalysts. The polymerization of dipropargylfluorene proceeded well by MoCl5 catalyst itself to give a quantitative yield of polymer. The Mo‐based catalysts are more effective than those of W‐based catalysts. The structure of poly(dipropargylfluorene) was characterized by various instrumental methods (NMR, IR, and UV–visible spectroscopies) to have the conjugated polymer backbone carrying fluorene moieties. Analysis of the 13C NMR spectrum revealed that the polymer structure consists of only six‐membered rings. The resulting poly(dipropargylfluorene)s were brown or black powder and soluble in aromatics and halogenated hydrocarbons such as benzene, chlorobenzene, tetrahydrofuran, chloroform, and methylene chloride. Thermal and morphological properties of the polymer are also discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4101–4109, 2001 相似文献
1000.
In a half-plane problem with x1 paralleling with the straight boundary and x2 pointing into the medium, the stress components on the boundary whose acting plane is perpendicular to x1 direction may be denoted by t1 = [σ11, σ12, σ13]T. Stress components σ11 and σ13 are of more interests since σ12 is completely determined by the boundary conditions. For isotropic materials, it is known that under uniform normal loading σ11 is constant in the loaded region and vanishes in the unloaded part. Under uniform shear loading, σ11 will have a logarithmic singularity at the end points of shear loading. In this paper, the behavior of the stress components σ11 and σ13 induced by traction-discontinuity on general anisotropic elastic surfaces is studied. By analyzing the problem of uniform tractions applied on the half-plane boundary over a finite loaded region, exact expressions of the stress components σ11 and σ13 are obtained which reveal that these components consist of in general a constant term and a logarithmic term in the loaded region, while only a logarithmic term exists in unloaded region. Whether the constant term or the logarithmic term will appear or not completely depends on what values of the elements of matrices Ω and Γ will take for a material under consideration. Elements for both matrices are expressed explicitly in terms of elastic stiffness. Results for monoclinic and orthotropic materials are all deduced. The isotropic material is a special case of the present results. 相似文献