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971.
972.
973.
974.
Two Tetrachlorothiotantalates: [Na‐15‐crown‐5][TaSCl4 · dioxane] and [Na‐15‐crown‐5]2[(TaSCl4)2dioxane] · S8 During the reaction of Na2S4, TaCl5 and 15‐crown‐5 in dichloromethane the crown ether partly suffers degradation to 1,4‐dioxane. Aside from sulfur, [Na‐15‐crown‐5][TaSCl4 · dioxane] was the first product obtained. It crystallizes in the monoclinic space group P21/n with a = 1066.1, b = 1781.3, c = 1258.3 pm, β = 97.14°, Z = 4. In the [TaSCl4 · dioxane]– ion a dioxane molecule is loosely bonded to a square‐pyramidal TaSCl4– unit; two chlorine atoms are in contact with an Na+ ion. Upon standing with the mother liquor [Na‐15‐crown‐5]2[(TaSCl4)2dioxane] · S8 was formed. It crystallizes in the monoclinic space group C2/m; a = 1768.5, b = 1084.0, c = 1517.3 pm, β = 118.46°, Z = 4. In this case a dioxane molecule is coordinated with two TaSCl4– units. The [(TaSCl4)2 · dioxane]2– ions and S8 molecules alternate in the stacking direction b. 相似文献
975.
David C. Green Ulrich Englich Karin Ruhlandt‐Senge 《Angewandte Chemie (International ed. in English)》1999,38(3):354-357
An unprecedented ligand bending mode is displayed by the acetylide ligands in the first structurally characterized σ‐bound organometallic strontium and barium complexes [M([18]crown‐6)(CCSiPh3)2] (M=Sr, Ba). Furthermore, the observed decrease of the angle at the sp‐hybridized C atom on descending Group 2 (see structures depicted) affords new information that will lead to a better understanding of the bonding in alkaline earth metal compounds. 相似文献
976.
Ulrich Herber Birgit Weberndrfer Helmut Werner 《Angewandte Chemie (International ed. in English)》1999,38(11):1609-1613
Significantly different coordination spheres are displayed by the two central atoms of 2 , the first representative of a novel type of mixed-valence dinuclear Rh0–RhII compound, which was synthesized from the stibane-bridged complex 1 . The Rh−Rh distance determined by an X-ray crystal structure analysis of 2 indicates a metal–metal interaction between the two metal centers. 相似文献
977.
Hans Bettermann Lars Ulrich Gabriele Domnick Hans-Dieter Martin 《Angewandte Chemie (International ed. in English)》1999,38(17):2573-2576
Owing to the low quantum yield of phosphorescence , triplet states of carotenoids have been very difficult to identify. These states can be characterized by intracavity absorption spectroscopy, which allows the direct measurement of the spin-forbidden singlet–triplet transitions in low concentrated solutions, and by delayed fluorescence measurements. 相似文献
978.
Hans J. Heger Ralph Dorfner Ralf Zimmermann Egmont R. Rohwer Ulrich Boesl Antonius Kettrup 《Journal of separation science》1999,22(7):391-394
The laser-based methods Laser Induced Fluorescence (LIF) and Resonance-Enhanced Multi-Photon Ionization (REMPI) can be used as highly selective detection modes for gas chromatography (GC). One major prerequisite for successful application of these detection methods is the availability of appropriate and reliable interfaces between the GC effluent and the molecular beam inlet. When a pulsed supersonic molecular beam (jet) source is used, the analyte molecules are efficiently cooled, allowing maximum selectivity of the laser spectroscopic detection methods. However, several technical problems have to be solved for practical realization of a GC-supersonic jet valve hyphenation. The pulsed jet interface should not interfere with the GC properties and the supersonic molecular beam properties. Further a good working cycle for the conversion from the continuously flowing GC current to the pulsed jet gas flow should be attained. This paper presents a novel setup of a GC-pulsed jet interface. The construction allows temporal and spatial compression of the analyte molecules in jet gas pulse and thus an increase of the detection sensitivity. Moreover, the GC effluent comes into contact only with glass surfaces and not with valve parts like plungers and seals. This reduces memory effects and sample decomposition. The valve setup is tested with a REMPI-TOFMS instrument. 相似文献
979.
980.
Ferenc Hegedűs Werner Lauterborn Ulrich Parlitz Robert Mettin 《Nonlinear dynamics》2018,94(1):273-293
A novel method to control multistability of nonlinear oscillators by applying dual-frequency driving is presented. The test model is the Keller–Miksis equation describing the oscillation of a bubble in a liquid. It is solved by an in-house initial-value problem solver capable to exploit the high computational resources of professional graphics cards. During the simulations, the control parameters are the two amplitudes of the acoustic driving at fixed, commensurate frequency pairs. The high-resolution bi-parametric scans in the control parameter plane show that a period-2 attractor can be continuously transformed into a period-3 one (and vice versa) by proper selection of the frequency combination and by proper tuning of the driving amplitudes. This phenomenon has opened a new way to drive the system to a desired, pre-selected attractor directly via a non-feedback control technique without the need of the annihilation of other attractors. Moreover, the residence in transient chaotic regimes can also be avoided. The results are supplemented with simulations obtained by the boundary-value problem solver AUTO, which is capable to compute periodic orbits directly regardless of their stability, and trace them as a function of a control parameter with the pseudo-arclength continuation technique. 相似文献