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41.
A simple correction technique for positron annihilation photon lineshape measurements which can significantly decrease systematic errors arising from resolution changes is described. 相似文献
42.
The fracture of thick laminated graphite/epoxy composites has been the subject of an extensive research program. The program
was divided into three major areas of investigation which included laminate thickness, laminate stacking sequence, and part-through
surface flaws. The results from this program are reviewed with emphasis placed on their applicability to the design of thick
laminated composite structures.
Paper was presented at 1985 SEM Spring Conference on Experimental Mechanics held in Las Vegas on June 9–14, 1985. 相似文献
43.
For any graph, there is a largest integer k such that given any partition of the vertex set with at most k elements in each class of the partition, there is transversal of the partition that is a dominating set in the graph. Some basic results about this parameter, the partition domination number, are obtained. In particular, it is shown that its value is 2 for the two-dimensional infinite grid, and that determining whether a given vertex partition admits a dominating transversal is NP-complete, even for a graph which is a simple path. The existence of various dominating transversals in certain partitions in regular graphs is studied as well. © 1996 John Wiley & Sons, Inc. 相似文献
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二氧化硅悬浮体和水解聚丙烯酰胺体系的流变性 总被引:6,自引:0,他引:6
研究了二氧化硅悬浮体的流变性。在固体含量较少的情况下, 体系呈Newton型;固体含量达到一定程度以后, 产生三维结构, 为假塑性体系。三维结构的固体含量与pH值有关。实验证实, 在等电点(i,e, p)附近三维结构最为疏松。还研究了水解聚丙烯酰胺(HPAM)对悬浮体流变性能的影响。HPAM破坏了二氧化硅粒子聚集体结构, 呈絮凝体结构, 并出现触变性。当高聚物在固体表面覆盖一半时, 具有最大触变性和动剪切力。HPAM的水解度达到一定程度, 由于对固体粒子由“强”吸附转变为“弱”吸附, 固体粒子“屏蔽”了高分子间的相互作用, 出现了负触变性现象。在流动时粒子会脱附, 静止以后又产生吸附, 这种吸附与脱附是产生负触变性的主要原因。HPAM水解过度或用量过多, 均会减弱负触变性现象。 相似文献
47.
Liming Cai Jianer Chen Rodney G. Downey Michael R. Fellows 《Archive for Mathematical Logic》1997,36(4-5):321-337
A completeness theory for parameterized computational complexity has been studied in a series of recent papers, and has been
shown to have many applications in diverse problem domains including familiar graph-theoretic problems, VLSI layout, games,
computational biology, cryptography, and computational learning [ADF,BDHW,BFH, DEF,DF1-7,FHW,FK]. We here study the parameterized
complexity of two kinds of problems: (1) problems concerning parameterized computations of Turing machines, such as determining
whether a nondeterministic machine can reach an accept state in steps (the Short TM Computation Problem), and (2) problems concerning derivations and factorizations, such as determining whether a word can be derived in a grammar in steps, or whether a permutation has a factorization of length over a given set of generators. We show hardness and completeness for these problems for various levels of the hierarchy. In particular, we show that Short TM Computation is complete for . This gives a new and useful characterization of the most important of the apparently intractable parameterized complexity
classes.
Received August 1, 1994 相似文献
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Hitoshi Sato Anurag Tyagi Hong Zhong Natalie Fellows Roy B. Chung Makoto Saito Kenji Fujito James S. Speck Steven P. DenBaars Shuji Nakamura 《固体物理学:研究快报》2007,1(4):162-164
We demonstrate a high power green InGaN/GaN multiple‐quantum‐well (MQW) light emitting diode (LED) with a peak emission wavelength of 516 nm grown on low extended defect density semipolar (11 2) bulk GaN substrate by metal organic chemical vapor deposition. The output power and external quantum efficiency (EQE) at drive currents of 20 and 100 mA under direct current (DC) operation were 5.0 mW, 10.5% and 15.6 mW, 6.3%, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
50.
Spectroelectrochemical studies of the intervalence charge transfer (IVCT) characteristics of both diastereoisomeric forms of the dinuclear complex [{Ru(bpy)2}2(mu-dpi-)]n+ [bpy=2,2'-bipyridine; dpi-=4,5-di(2-pyridyl)imidazolate] showed that the degree of inter-metal electronic coupling (or valence delocalization) is dependent on stereochemical identity. Increasing the relative concentration of the strongly associating anion toluene-4-sulfonate in acetonitrile/[(n-C4H9)4N]{B(C6F5)4} solution differentially decreased the level of delocalization for the two diastereoisomers. In a comparative investigation of electrochemical and spectroelectrochemical techniques of the anion-induced electron localization in [{Ru(bpy)2}2(mu-dpo)]5+ [dpo=3,4-di(2-pyridyl)-1,2,5-oxadiazole], differences were observed between the two methods in the order and extent of effects induced by a number of inorganic anions (PF6-, BF4-, ClO4-). It was determined that the measure of coupling derived from electrochemical methods was less reliable than that obtained from spectral methods. Comparative electrochemical studies were undertaken on [{M(bpy)2}2(mu-BL)]n+ {M=Ru, Os; BL=dpo, dpi-), which revealed substantial differences in DeltaEox (the separation between the redox potentials for the MII-MII/MIII-MII and MII-MIII/MIII-MIII couples) for the two metal centers and therefore the comproportionation constant Kc, dependent on the neutral or anionic nature of the bridging ligand. 相似文献