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Nélio Henderson Marroni de Sá Rêgo Janaína Imbiriba Márlison de Sá Rêgo Wagner F. Sacco 《Optimization Letters》2018,12(4):727-741
In general, classical iterative algorithms for optimization, such as Newton-type methods, perform only local search around a given starting point. Such feature is an impediment to the direct use of these methods to global optimization problems, when good starting points are not available. To overcome this problem, in this work we equipped a Newton-type method with the topographical global initialization strategy, which was employed together with a new formula for its key parameter. The used local search algorithm is a quasi-Newton method with backtracking. In this approach, users provide initial sets, instead of starting points. Then, using points sampled in such initial sets (merely boxes in \({\mathbb {R}}^{n}\)), the topographical method selects appropriate initial guesses for global optimization tasks. Computational experiments were performed using 33 test problems available in literature. Comparisons against three specialized methods (DIRECT, MCS and GLODS) have shown that the present methodology is a powerful tool for unconstrained global optimization. 相似文献
974.
Viktor Bezugly Pawel Wielgus Miroslav Kohout Frank R. Wagner 《Journal of computational chemistry》2010,31(12):2273-2285
Electron localizability indicators based on the electron pair density ELI–D and ELIA Electron localizability indicators ELI‐D and ELIA based on the electron pair density are studied for the correlated ground‐state wavefunctions of N2, O2, F2, and Ne2 diatomics. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two indicators. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for O2 and F2, the reliable topology of ELI–D is obtained only at the correlated level of theory. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010 相似文献
975.
Júlio C. S. da Silva Roberta P. Dias Wagner B. de Almeida Willian R. Rocha 《Journal of computational chemistry》2010,31(10):1986-2000
DFT calculations were carried out to study the full catalytic cycle for the hydroformylation of propene, catalyzed by the heterobimetallic model catalyst trans‐Pt(H)(PH3)2(SnCl3). Before the study of the full catalytic cycle, the performance of six pure GGA, one GGA with inclusion of dispersion corrections, four hybrid‐GGA, and three meta‐GGA exchange correlation functional to describe a model reaction promoted by Pt‐Sn catalyst were assessed. It is shown that the BP86 and GPW91 functionals, using extended basis set, provides reliable energetic results when compared with the CCSD(T) calculations. All intermediates and transition states along the elementary steps of the entire catalytic cycle were located and the energies involved in the catalytic cycle calculated using BP86 functional. The solvent effects along the entire catalytic cycle were evaluated using the polarizable continuum model. In contrast with the rhodium catalysts, the regioselectivity of the hydroformylation is set at the carbonylation step. The hydrogenolysis is the rate determining step of the entire cycle, with the activation energy of ~21 kcal mol?1 in agreement with the experimental value of ~25 kcal mol?1. The trans effect of the SnCl ligand seems to be pronounced only in the first step of the catalytic cycle, facilitating the insertion of the olefin into the Pt? H bond trans to it. The analysis of the stationary points obtained along each elementary step of the catalytic cycle is carried out separately and discussed. The BP86/cc‐pVTZ/SBKJC results shows that the pathway leading to the linear aldehyde is preferred, being in agreement with the experimental findings. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
976.
Li2O-ZrO2-BaO-SiO2 glass fibers were produced and their surfaces were coated with zinc oxide. The fibers’ surface morphology was examined by scanning electron microscopy and the zinc oxide layer was characterized by mapping the Kα and Lα lines of zinc by energy dispersive X-ray spectroscopy. The results indicated that a homogeneous and porous layer of ZnO was formed on the fibers’ surface. This layer was subjected to a simultaneous determination of trihalomethanes using headspace-solid phase microextraction-gas chromatography. The study was conducted after evaluating the ideal time of incubation (15 min), extraction (15 min) and desorption (10 min), as well as the effect of the addition of salt (15%, m/v) on the analytical response. A good linear dynamic range was observed individually for trihalomethanes aqueous solutions containing 20 μg L−1 and 500 μg L−1 of trichloromethane, 15 μg L−1 and 250 μg L−1 of dichlorobromomethane and dibromochloromethane and 10 μg L−1 and 100 μg L−1 of tribromomethane, with all the compounds showing correlation coefficients higher than 0.9900. 相似文献
977.
Megan K. Wagner Feng Li Jingjing Li Xing-Fang Li X. Chris Le 《Analytical and bioanalytical chemistry》2010,397(8):3213-3224
Biomarker assays may be useful for screening and diagnosis of cancer if a set of molecular markers can be quantified and statistically differentiated between cancerous cells and healthy cells. Markers of disease are often present at very low concentrations, so methods capable of low detection limits are required. Quantum dots (QDs) are nanoparticles that are emerging as promising probes for ultrasensitive detection of cancer biomarkers. QDs attached to antibodies, aptamers, oligonucleotides, or peptides can be used to target cancer markers. Their fluorescent properties have enabled QDs to be used as labels for in-vitro assays to quantify biomarkers, and they have been investigated as in-vivo imaging agents. QDs can be used as donors in assays involving fluorescence resonance energy transfer (FRET), or as acceptors in bioluminescence resonance energy transfer (BRET). The nanoparticles are also capable of electrochemical detection and are potentially useful for “lab-on-a-chip” applications. Recent developments in silicon QDs, non-blinking QDs, and QDs with reduced-size and controlled-valence further make these QDs bioanalytically attractive because of their low toxicity, biocompatibility, high quantum yields, and diverse surface modification flexibility. The potential of multiplexed sensing using QDs with different wavelengths of emission is promising for simultaneous detection of multiple biomarkers of disease. Figure
Quantum dots have been conjugated to affinity probes to assay for cancer biomarkers including proteins, peptides, DNA, and whole cells 相似文献
978.
Daniel Franz Matthias Wagner Hans‐Wolfram Lerner Michael Bolte 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(6):m152-m156
The title compound, 3K+·C6H3B3F93−, crystallizes as discrete anions and cations which are connected by K...F and K...π interactions. Two of the –BF3 residues attached to the aromatic ring adopt a conformation with all F atoms out of the plane of the aromatic ring, whereas the third residue has an almost synperiplanar conformation for one of the F—B—C—C torsion angles. It is remarkable that only one of the K+ cations interacts with the arene ring and that only one side of the aromatic ring coordinates to a K+ cation. As a result, a sandwich structure does not occur. All K+ ions show a coordination mode that cannot be conveniently described with a polyhedron. The anions are located in the (102) planes with the K+ cations located between these planes. The investigated crystal was a nonmerohedral twin with the fractional contribution of the minor twin component being 0.405 (4). The title compound is the first example of a structure containing a benzene ring substituted with three –BF3 groups. Only eight other structures have been reported in which a benzene ring carries at least one –BF3 group. Just five of these contain a K+ ion, but in none of these is the K+ ion coordinated to the aromatic ring. 相似文献
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980.