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901.
A four-noded rectangular element with seven degrees of freedom at each node is developed for buckling analysis of laminated plate structures having any number of layers with a constant thickness of individual layers. The displacement model is so chosen that it can explain adequately the parabolic distribution of transverse shear stresses and the non-linearity of in-plane displacements across the thickness. A geometrical stiffness matrix is developed using in-plane stresses. A wide range of plates from thick to thin are examined under uniaxial loading conditions. The results are compared with the existing analytical and numerical solutions. The present formulations confirm its applicability for buckling analysis of a wide range of plates. 相似文献
902.
Vaporizing solid samples of metals and semiconductors with a YAG Laser is a method well suited for producing molecules and
clusters of those materials. The clusters are examined by either laser-induced fluorescence (LIF) or mass spectroscopic methods.
The technique is valuable for both gas phase and matrix studies. The method is described and some applications, studying either
the structure of small metal molecules or their reactions, are reviewed, with emphasis on our recent results from the LIF
studies of LiBe, Al2 and the reaction of Al with oxygen, yielding A12O. For larger clusters, Ion Cyclotron Resonance is an extremely valuable method, as we demonstrate by its application to the
reactions of small charged silicon clusters with strong oxidising agents. 相似文献
903.
M. Sperling Xuefeng Yin B. Welz 《Spectrochimica Acta Part B: Atomic Spectroscopy》1991,46(14):1789-1801
Arsenic(III) can be quantitatively extracted using sodium diethyldithiocarbamate (NaDDTC) as the complexing agent and C18 reversed phase packing as the column material for solid phase extraction. Arsenic(V) must be reduced to its trivalent oxidation state prior to extraction. A mixture of sodium sulphite, hydrochloric acid, sodium thiosulphate and potassium iodide was found to be optimum for on-line reduction. When the sorbent extraction is carried out without and with the addition of the reduction mixture, arsenic(III) and total arsenic can be determined sequentially by graphite furnace atomic absorption spectrometry with detection limits (3 σ) of 0.32 ng for As(III) and 0.43 ng for total arsenic. A 7.6-fold enhancement in peak area compared to direct injection of 40 μl samples was obtained after 60 s preconcentration. Results obtained for sea water standard reference materials, using aqueous standards for calibration, agree well with certified values. A precision of 5.5% RSD was obtained for total arsenic in a sea water sample (1.65
As). Results obtained for synthetic mixtures of trivalent and pentavalent arsenic agreed well with expected values. 相似文献
904.
本文简要介绍钽酸锂晶体及器件的一些特性,对用该材料制作的21.4MHz宽带滤波器的设计、制作和测试结果作了较详细的介绍,滤波器的带宽达225kHz,矩形系数(BW_(?0dB)/BW_(3dB)为2.66,带外衰减在50dB以上。该材料在做宽带滤波器和压控振荡器方面具有优越性。 相似文献
905.
本文简单地回顾了提高VLSI测试效率所采用的一些手段,讨论了在ASIC测试问题研究中出现的一些新观点、新方法、新动向,以及所取得的成果。在此基础上,文章阐明了ASIC测试技术的发展方向,并着重论述了可望在未来得到发展的,针对ASIC的功能测试方法。 相似文献
906.
在“星光Ⅱ”激光装置上,利用80只分立式探测器研究了约0.8ns,0.351μm激光辐照Au盘靶的吸收、散射.结果表明,强度约为5×1014W/cm2的激光以10°角入射,吸收可达90%以上;但是,以45°角入射,吸收仅为75%左右,散射高达25%.散射主要来自未被等离子体充分吸收的激光在弯曲临界面上的反射,同时伴随少量受激布里渊散射.吸收的理论计算与实验结果进行了比较,两者符合较好.
关键词: 相似文献
907.
Matthias Heydenreich Andreas Koch E. Kleinpeter Thomas Zimmermann 《Fresenius' Journal of Analytical Chemistry》1997,357(5):517-521
Dynamic NMR investigations of a number of 2-amino-3-aroyl-4,6-diaryl-pyrylium salts were carried out. The barrier to rotation
of the partial C, N double bond was determined and proved to be in the range of 62 to 63 kJ/mol. Quantum chemical calculations
of bond orders and electron densities of the different atoms in the molecules show the distinct double bond character of the
exocyclic C, N bond. This is in agreement with the relatively high barrier to rotation. By quantum chemical ab initio 3-21G
calculations, the dynamic behaviour of this kind of compounds was simulated; two pairs (image and mirror image) of ground
state conformations, in coincidence with the experiment, were obtained.
Received: 10 May 1996 / Revised: 1 July 1996 / Accepted: 4 July 1996 相似文献
908.
A. Jarid M. Aaid Y. Legoux J. Merini M. Loudet D. Gonbeau G. Pfister-Guillouzo 《Chemical physics》1991,150(3):353-360
The electronic and structural characteristics of CrF5, CrF4, RuF5 and RuF4 were studied. Ab initio (SCF-CI) calculations were performed with different structures and spin states for each complex. The favored conformation always corresponds to the highest multiplicity: doublet for CrF5 in D3h, triplet for CrF4 in Td, quadruplet for RuF5 in C4v and quintuplet for RuF4 in D4h symmetry. 相似文献
909.
910.