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91.
A computer program for railway wheel life prediction has been developed incorporating an elastoplastic calculation of both the residual stress field induced by shoe-braking and the superposed alternating rolling contact stresses. The possibilities of unstable propagation of surface cracks, crack arrest, fatigue propagation through a complex stress field and crack detention on reaching the threshold value have been accounted for. An approximate method for crack growth prediction is used providing bounds for instantaneous crack front position and estimations of crack shape within short computing times. Some examples of application for an UIC R7 wheel are presented. 相似文献
92.
Kh. Kh. Gil’manov R. G. Romanova A. A. Lamberov R. R. Gil’mullin 《Russian Journal of Applied Chemistry》2010,83(1):76-83
Calorimetry, thermogravimetry, X-ray diffraction analysis, and low-temperature adsorption of nitrogen were used to study the
structure of bimetallic Pt—Sn catalysts on zinc–alumina spinel supports. The effect of the porous structure of the catalyst
samples synthesized on their catalytic activity in dehydrogenation of 2–methyl butane was analyzed. 相似文献
93.
Mechanical Behavior of Polymer Gels for RDCs and RCSAs Collection: NMR Imaging Study of Buckling Phenomena 下载免费PDF全文
Erich Hellemann Dr. Rubens R. Teles Prof. Dr. Fernando Hallwass Prof. Dr. W. Barros Jr. Dr. Armando Navarro‐Vázquez Prof. Dr. Roberto R. Gil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16632-16635
Anisotropic NMR parameters, such as residual dipolar couplings (RDCs), residual chemical shift anisotropies (RCSAs) and residual quadrupolar couplings (RQCs or ΔνQ), appear in solution‐state NMR when the molecules under study are subjected to a degree of order. The tunable alignment by reversible compression/relaxation of gels (PMMA and p‐HEMA) is an easy, user‐friendly, and very affordable method to measure them. When using this method, a fraction of isotropic NMR signals is observed in the NMR spectra, even at a maximum degree of compression. To explain the origin of these isotropic signals we decided to investigate their physical location inside the NMR tube using deuterium 1D imaging and MRI micro‐imaging experiments. It was observed that after a certain degree of compression the gels start to buckle and they generate pockets of isotropic solvent, which are never eliminated. The amount of buckling depends on the amount of cross‐linker and the length of the gel. 相似文献
94.
Dr. Pere Miró Dr. Bess Vlaisavljevich Dr. Adria Gil Dr. Peter C. Burns Dr. May Nyman Dr. Carles Bo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8571-8578
A wide range of uranyl–peroxide nanocapsules have been synthesized using very simple reactants in basic media; however, little is known about the process to form these species. We have performed a density functional theory study of the speciation of the uranyl ions under different experimental conditions and explored the formation of dimeric species via a ligand exchange mechanism. We shed some light onto the importance of the excess of peroxide and alkali counterions as a thermodynamic driving force towards the formation of larger uranyl–peroxide species. 相似文献
95.
Sang Sub Kim Sun-Woo Choi Han Gil Na Dong Sub Kwak Yong Jung Kwon Hyoun Woo Kim 《Current Applied Physics》2013,13(3):526-532
ZnO–SnO2 branch–stem nanostructures were realized on a basis of a two-step process. In step 1, SnO2-stem nanowires were synthesized. In step 2, ZnO-branch nanowires were successfully grown on the SnO2-stem nanowires through a simple evaporation technique. We have pre-deposited thin Au layers on the surface of SnO2 nanowire stems and subsequently evaporated Zn powders on the nanowires. The ZnO branches, which sprouted from the SnO2 stems, had diameters in a range of 30–35 nm. As-synthesized branches were of single crystalline hexagonal ZnO structures. Since the branch tips were comprised of Au-containing nanoparticles, the Au-catalyzed vapor–liquid–solid growth mechanism was more likely to control the growth process of the ZnO branches. To test a potential use of ZnO–SnO2 branch–stem nanostructures in chemical gas sensors, their sensing performances with respect to NO2 gas were investigated, showing the promising potential in chemical gas sensors. 相似文献
96.
M. I. Gil’ 《Annali dell'Universita di Ferrara》2010,56(1):207-216
We consider a matrix valued function of two infinite commuting matrices generating bounded operators in a Banach space. Sharp
estimates for the norm and entries are derived. Applications of the obtained estimates to differential equations are also
discussed. 相似文献
97.
98.
Maria J. Alves Vera C.M. Duarte Hélio Faustino António Gil Fortes 《Tetrahedron: Asymmetry》2010,21(15):1817-1820
Erythrose benzylidene-acetal 1,3-butadienes are studied as partners in Diels–Alder cycloadditions. A high diastereofacial improvement is found in cases where both the alcohol function is protected and a π–π interaction between the diene and dienophile is possible. Several competing factors have been studied independently in order to explain its influence on the selectivity of the cycloadditions. 相似文献
99.
Integral representations are considered of solutions of the Airy differential equation w
–zw=0 for computing Airy functions for complex values of z. In a first method contour integral representations of the Airy functions are written as non-oscillating integrals for obtaining stable representations, which are evaluated by the trapezoidal rule. In a second method an integral representation is evaluated by using generalized Gauss–Laguerre quadrature; this approach provides a fast method for computing Airy functions to a predetermined accuracy. Comparisons are made with well-known algorithms of Amos, designed for computing Bessel functions of complex argument. Several discrepancies with Amos' code are detected, and it is pointed out for which regions of the complex plane Amos' code is less accurate than the quadrature algorithms. Hints are given in order to build reliable software for complex Airy functions. 相似文献
100.
E. Rodrigues S. Vaz V.M.S.S. Gil M. Caldeira A.M.G. Moreira Da Silva 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):395-397
A 1H-NMR study of the interactionsbetween -cyclodextrin (-CD) and included phenolic molecules (chloragenic acid and caffeic acid ) in aqueous medium is reported. The results confirm that inclusion occurs. Data analysis by the continuous variation method shows that all the complexes have 1 : 1 stoichiometries. Values for the apparent association constants of the inclusion compounds are estimated and compared with previously reported values. 相似文献