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941.
Rotational ambiguity is a major problem in the application of soft-modeling analysis to a variety of multivariate mixture resolution problems and particularly important in the analysis of kinetic data. Soft-modeling analyses rely on constraints that restrict the concentration profiles and/or the spectral responses of all components. The main goal of this work is to demonstrate how a hard-modeling constraint on concentration profiles drastically decreases the extent of the rotational ambiguity. Therefore, in the present paper the discussion is focused on systems in which hard-modeling information is available. The results of simulated examples reveal that the utilized hard constraint decreases the rotational ambiguity in estimated concentration profile even components that do not take part in the explicit model. In addition, the rate constant of known reaction is determined in this method. 相似文献
942.
Khodayar Gholivand Hamid R. MahzouniForoogh Molaei Ali A. Kalateh 《Tetrahedron letters》2012,53(44):5944-5947
The reaction between phosphoryl-containing reagents and hydrazides has been studied. The tetrahedral phosphoryl structure is transformed into a spiro-bicyclophosphorane system with trigonal bipyramidal geometry by the elimination of a β-amidic proton in the reaction between a hydrazide and phosphoryl reagents with at least two leaving groups (Cl) bound to the phosphorus atom, such as POCl3 or PhPOCl2. In the spiro-bicyclophosphorane structure, the CN imine bond is formed upon β-amidic proton elimination, leading to the conversion of the CO into a C-O bond and the formation of a P-O bond. All of these structural rearrangements are supported by X-ray crystallography data, and NMR and IR experiments. 相似文献
943.
Abbas Ali Esmaeili Mahdieh Zangouei Ali Reza Fakhari Azizollah Habibi 《Tetrahedron letters》2012,53(11):1351-1353
We present a novel, convenient, and efficient method for synthesizing polysubstituted 3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidines via a three-component reaction. The zwitterions generated from the reaction of isocyanides and dialkyl acetylenedicarboxylates react with 2-imino-1,3-thiazolidin-4-one to produce the title compounds in good yields. 相似文献
944.
Masoud Heydari Hamid Moharrami Hadi Yazdani-Paraei 《Journal of Optimization Theory and Applications》2012,155(3):1025-1046
In this paper the nonlinear analysis and design optimization of guyed masts is addressed. The mast is modeled as a 3D truss and is supported by catenary cable elements that have nonlinear elastic behavior. For nonlinear static analysis, an innovative procedure is proposed that divides the structure into linear and nonlinear parts and analyzes them separately. The proposed method satisfies the equilibrium and compatibility by establishing and solution of a set of nonlinear equations. The optimization problem employs the sizes of members, initial cable tensions and the positions of anchor on the ground and tie level of cables on the mast as design variables. To facilitate the optimization solution, a compatible sensitivity analysis procedure is proposed. Sensitivities of objective function, displacement and strength constraints in the mast and cables, subjected to a variety of load combinations including dead, wind and ice loads are calculated. Numerical examples are provided to show the nonlinear analysis procedure and the applicability of the algorithm to optimum design of practical guyed masts. 相似文献
945.
We consider the homogenization of a conductivity equation for a medium made up of a set ${F_\varepsilon}$ ( ${\varepsilon}$ being the size of the period of the medium) of highly conductive vertical fibers surrounded by another material (the matrix) assumed to be a poor conductor. The conductivity coefficients in the fibers behave as ${\frac{1}{\varepsilon^2}}$ while whose of the matrix behave as ${\varepsilon^2}$ . We show that the homogenized problem consists of an equality of the kind u(x) = m(x) f (x) where u denotes the macroscopic temperature, f the source term and m(x) a coefficient given by solving some cell equation. 相似文献
946.
Reza Azadbakht Hassan Keypour Hadi Amiri Rudbari Ali Hossein Mohammad Zaheri Saeid Menati 《Journal of luminescence》2012,132(8):1860-1866
Two new macrocyclic systems (L1, L2) containing two emissive naphthalene were synthesized and characterized. The macrocycles were studied by 1H NMR, 13C NMR, COSY, HMQC, DEPT, microanalysis and mass spectroscopy. The influence of metal cations Na+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+ on the spectroscopic properties of the macrocyclic systems in acetonitrile/DMF 9:1 (v/v) mixtures were investigated by means of absorption and emission spectrophotometry. The macrocycle L1 was found to be as an effective fluorescence sensor for Zn2+ ions. Zn2+ and Cd2+ ions show the most effects on the fluorescence intensity of L2. 相似文献
947.
Abbas Ghasempour Ardakani Ali Reza Bahrampour Seyed Mohammad Mahdavi Mojtaba Golshani Gharyeh Ali 《Optics Communications》2012,285(6):1314-1322
In this paper, the lasing action in three-dimensional active random systems has been numerically investigated. Here, random systems of spherical dielectric particles imbedded in an active medium are considered. The quasi steady state approximation for the population inversion of the active medium is applied to solve three dimensional governing equations. Results show that when the density of particles increases to an upper limit, the intensity of lasing modes is enhanced. Also, the effects of pumping rate and particle size on the number of lasing modes and their intensity are studied. Lasing threshold of laser modes in different disordered systems is calculated and it is shown that by an appropriate selection of the central frequency of gain line-shape, the output power intensity of random lasers increases. These results are in agreement with the experimental results observed by others. 相似文献
948.
Mohammad Ali Ansari Saeid Alikhani Ezeddin Mohajerani Reza Massudi 《Optics Communications》2012,285(5):851-855
In this study, the diffusion of photons in turbid media, like biological tissue has been studied. Due to scattering and absorption of photons in such media, the study of photon propagation in biological tissue is complicated. The several numerical methods have been presented to simulate the behavior of diffused photons. Recently, Boundary Integral Method (BIM) has been offered to simulate photon migration inside biological tissues. This method has advantage, e.g. lower computational time in compared with other numerical methods. In this study, the accuracy and precision of BIM compares with another numerical method like Monte Carlo technique and finite difference method, and also the calculated results obtained by BIM and Monte Carlo method evaluate with measured results. Furthermore, the effects of scattering and absorption coefficient of tissue on the measured signal are studied. 相似文献
949.
Malihe Javan Khoshkholgh Mohammad Reza Hosseindokht Saeed Balalaie Mohammad Reza Bozorgmehr Hamid Reza Bijanzadeh 《Helvetica chimica acta》2012,95(1):52-60
The CuI‐catalyzed intramolecular oxa‐Diels? Alder reaction of 2‐(prop‐2‐yn‐1‐yloxy)benzaldehydes as unactivated terminal alkynes with 4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one is described. The reaction proceeds with remarkable chemoselectivity to yield pyranones 3 (Scheme 1). A theoretical investigation of the reaction in terms of HOMO? LUMO interactions in the gas phase is also reported. The reaction could be regarded as an inverse‐electron‐demand Diels? Alder cycloaddition. The theoretical results are in high agreement with the experimental evidences. 相似文献
950.
S. Masoud Nabavizadeh Hashem Amini Fatemeh Jame Sedigheh Khosraviolya Hamid R. Shahsavari Fatemeh Niroomand Hosseini Mehdi Rashidi 《Journal of organometallic chemistry》2012
New cyclometalated platinum(II) complexes [PtMe(C^N)L], 1, in which C^N = deprotonated 2-phenylpyridine (ppy), benzo[h]quinoline (bhq) or 2-(p-tolyl)pyridine (tpy) and L = PPh3 or PMePh2, were synthesized by the reaction of [PtMe(C^N)(SMe2)] with 1 equiv of L. The reaction of complexes 1 with MeI gave the cyclometalated Pt(IV) complexes [PtMe2I(C^N)L], 3. On the basis of kinetic studies, using Uv–visible spectroscopy, it was suggested that the latter oxidative addition reactions were proceeded by an SN2 mechanism. The rates of the reactions at different temperatures were measured and consistent with the proposed mechanism, large negative ΔS3 values were found for each reaction. Besides, rate of reactions (in CHCl3) involving the PPh3 complexes [PtMe(C^N)(PPh3)], were almost 3–5 times slower than those involving the PMePh2 complexes [PtMe(C^N)(PMePh2)]. This was attributed to the electronic and steric effects of PPh3 ligand as compared with that of PMePh2 ligand which was further confirmed using density functional theory (DFT) calculations through finding approximate structures for the described complexes. 相似文献