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排序方式: 共有219条查询结果,搜索用时 15 毫秒
71.
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73.
Competitive queue policies for differentiated services 总被引:1,自引:0,他引:1
William A. Aiello Yishay Mansour S. Rajagopolan Adi Rosn 《Journal of Algorithms in Cognition, Informatics and Logic》2005,55(2):398-141
We consider the setting of a network providing differentiated services. As is often the case in differentiated services, we assume that the packets are tagged as either being a high priority packet or a low priority packet. Outgoing links in the network are serviced by a single FIFO queue.Our model gives a benefit of α1 to each high priority packet and a benefit of 1 to each low priority packet. A queue policy controls which of the arriving packets are dropped and which enter the queue. Once a packet enters the queue it is eventually sent. The aim of a queue policy is to maximize the sum of the benefits of all the packets it sends.We analyze and compare different queue policies for this problem using the competitive analysis approach, where the benefit of the online policy is compared to the benefit of an optimal offline policy. We derive both upper and lower bounds for the policies we consider. We believe that competitive analysis gives important insight to the performance of these queuing policies. 相似文献
74.
Adi Ben-Israel 《Israel Journal of Mathematics》1964,2(1):50-54
In a *-linear Hestenes algebra, the elements with *-reciprocals are characterized by means of certain direct sum decompositions
of the algebra.
Research partly supported by the Office of Naval Research, contract Nonr-1228(10) project NR 047-021, and by the National
Science Foundation, project B-14102. 相似文献
75.
The asymptotic stability of a microscopic stochastic laser model in the Heisenberg picture is discussed using Liapounov's direct method. By reducing the laser Langevin equations to a classical van der Pol equation for the photon number in the rotating wave approximation, it may be shown that the above-threshold steady state characterized by the cubic non-linearity in the van der Pol equation, is stable. This leads to the definition of a monotonic increasing entropy function far from thermal equilibrium. 相似文献
76.
Alan Shaver Ian S. Butler Adi Eisenberg Jian Ping Gao Zhen H Xu Bertwin Fong Haewon Uhm David Klein 《应用有机金属化学》1987,1(5):383-392
A convenient method for embedding organometallic complexes in polymer films has been developed and the FT-IR spectra of these films have been investigated at room temperature. Infrared data in the n?(CO) stretching region are reported for M(CO)6 (M = Cr, Mo, W), CpMn(CO)3 (Cp = η5-C5H5), η-C6H6Cr(CO)2L [L = CO, P(n-Bu)3], (η6-C6H5NH2)Cr(CO)3, [η6-o-C6H4(NH2)MeCr(CO)3], CpFe(CO)LR [L = CO, PPh3; R = Me, C(O)Me] embedded in poly(methyl methacrylate) (PMMA), polystyrene (PS), polystyrene-poly(methyl methacrylate) (PS-PMMA), and polystyrene–polyacrylonitrile (PS-AN) plastic films. These matrices appear to approximate the common solvents ethyl acetate, toluene, toluene–ethyl acetate, and toluene–acetonitrile, respectively, with respect to n?(CO) vibrational band behavior. Several of the films have been subjected to UV irradiation and the photoproducts formed have been identified by FT-IR spectroscopy. PS-AN effectively traps photogenerated coordinatively unsaturated species via coordination of its pendant nitrile groups. 相似文献
77.
Azzam T Bronstein L Eisenberg A 《Langmuir : the ACS journal of surfaces and colloids》2008,24(13):6521-6529
A study is presented of the stabilization of gold and palladium nanoparticles (NPs) via a place-exchange reaction. Au and Pd NPs of approximately 3.5 nm were prepared by a conventional method using tetraoctylammonium bromide (TOAB) as the stabilizing agent. The resulting nanoparticles, referred to as Au-TOAB or Pd-TOAB, were later used as templates for the replacement of TOAB ligand with poly(ethylene oxide)- b-polystyrene- b-poly(4-vinylpyridine) (PEO- b-PS- b-P4VP) triblock copolymer. This biamphiphilic triblock copolymer was synthesized by atom transfer radical polymerization (ATRP) with control over the molecular weight and polydispersity. The place-exchange reaction was mediated through strong coordination forces between the 4-vinylpyridine copolymer and the metal species located on the surface of the nanoparticles. In addition, the displacement of the outgoing low molecular weight TOAB ligands by high molecular weight polymers is an entropy-assisted process and is believed to contribute to stabilization. The prepared complex, polymer-NP, exhibits greatly improved stability over the metal-NP complex in common organic solvents for the triblock copolymer. Self-assembly in water after ligand exchange resulted in micellar structures of about approximately 20 nm (electron microscopy) with the metal NP found located on the surface of the micelles. The stability of the nanoparticles in water was shown to depend greatly on the grafting density of the copolymer, with high stability (more than 6 months) at high grafting density and low stability, accompanied with irreversible agglomeration, at relatively low grafting densities. The surprising location of the metal NP (for both Au and Pd) on the surface of the micelles in water is explained by the fact that, upon self-assembly in THF/water system, the most hydrophobic chains (i.e., PS) undergo self-assembly first at low water content forming the core, followed by the P4VP (whether or not associated with the metal) forming a shell, and finally the PEO forming the corona. In lower metal content assemblies, the P4VP chains located in the shell undergo swelling in an acidic medium causing a substantial increase in micellar corona size, as confirmed by dynamic light scattering measurements. The present study offers a simple approach for the stabilization of various metal nanoparticles of catalytic interest, using a unique polymeric support that can be dispersed in organic solvents as well as aqueous solutions. 相似文献
78.
Cohen A Yeori A Kopilov J Goldberg I Kol M 《Chemical communications (Cambridge, England)》2008,(18):2149-2151
The first synthesis of achiral and chiral [ONNO']-type Salan ligands featuring two different phenol arms, and the diastereoselective formation of the corresponding octahedral C1-symmetric zirconium complexes is described; the activity and isospecificity induction of the [ONNO']Zr(bn)2 complexes in 1-hexene polymerisation reflected those of the parent symmetric compounds. 相似文献
79.
Dr. Eko Adi Prasetyanto Dr. Alessandro Bertucci Dr. Dedy Septiadi Prof. Roberto Corradini Dr. Pablo Castro‐Hartmann Prof. Luisa De Cola 《Angewandte Chemie (International ed. in English)》2016,55(10):3323-3327
The direct delivery of specific proteins to live cells promises a tremendous impact for biological and medical applications, from therapeutics to genetic engineering. However, the process mostly involves tedious techniques and often requires extensive alteration of the protein itself. Herein we report a straightforward approach to encapsulate native proteins by using breakable organosilica matrices that disintegrate upon exposure to a chemical stimulus. The biomolecule‐containing capsules were tested for the intracellular delivery of highly cytotoxic proteins into C6 glioma cells. We demonstrate that the shell is broken, the release of the active proteins occurs, and therefore our hybrid architecture is a promising strategy to deliver fragile biomacromolecules into living organisms. 相似文献
80.
Böcking T Salomon A Cahen D Gooding JJ 《Langmuir : the ACS journal of surfaces and colloids》2007,23(6):3236-3241
Self-assembled monolayers formed by thermal hydrosilylation of a trifluoroacetyl-protected alkenylthiol on Si-H surfaces, followed by removal of the protecting groups, yield essentially oxide-free monolayers suitable for the formation of Si-C11H22-S-Hg and Si-C11H22-S-Au junctions in which the alkyl chains are chemically bound to the silicon surface (via Si-C bonds) and the metal electrode (via Hg-S or Au-S bonds). Two barriers to charge transport are present in the system: at low bias the current is temperature activated and hence limited by thermionic emission over the Schottky barrier in the silicon, whereas as at high bias transport is limited by tunneling through the organic monolayer. The thiol-terminated monolayer on oxide-free silicon provides a well-characterized system allowing a careful study of the importance of the interfacial bond to the metal electrode for current transport through saturated molecules. 相似文献