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排序方式: 共有216条查询结果,搜索用时 250 毫秒
1.
A Hybrid Multiobjective Evolutionary Algorithm for Solving Vehicle Routing Problem with Time Windows 总被引:2,自引:0,他引:2
Vehicle routing problem with time windows (VRPTW) involves the routing of a set of vehicles with limited capacity from a central
depot to a set of geographically dispersed customers with known demands and predefined time windows. The problem is solved
by optimizing routes for the vehicles so as to meet all given constraints as well as to minimize the objectives of traveling
distance and number of vehicles. This paper proposes a hybrid multiobjective evolutionary algorithm (HMOEA) that incorporates
various heuristics for local exploitation in the evolutionary search and the concept of Pareto's optimality for solving multiobjective
optimization in VRPTW. The proposed HMOEA is featured with specialized genetic operators and variable-length chromosome representation
to accommodate the sequence-oriented optimization in VRPTW. Unlike existing VRPTW approaches that often aggregate multiple
criteria and constraints into a compromise function, the proposed HMOEA optimizes all routing constraints and objectives simultaneously,
which improves the routing solutions in many aspects, such as lower routing cost, wider scattering area and better convergence
trace. The HMOEA is applied to solve the benchmark Solomon's 56 VRPTW 100-customer instances, which yields 20 routing solutions
better than or competitive as compared to the best solutions published in literature. 相似文献
2.
Chaotic micromixers using two-layer crossing channels to exhibit fast mixing at low Reynolds numbers
We report two chaotic micromixers that exhibit fast mixing at low Reynolds numbers in this paper. Passive mixers usually use the channel geometry to stir the fluids, and many previously reported designs rely on inertial effects which are only available at moderate Re. In this paper, we propose two chaotic micromixers using two-layer crossing channels. Both numerical and experimental studies show that the mixers are very efficient for fluid manipulation at low Reynolds numbers, such as stretching and splitting, folding and recombination, through which chaotic advection can be generated and the mixing is significantly promoted. More importantly, the generation of chaotic advection does not rely on the fluid inertial forces, so the mixers work well at very low Re. The mixers are benchmarked against a three-dimensional serpentine mixer. Results show that the latter is inefficient at Re = 0.2, while the new design exhibits rapid mixing at Re = 0.2 and at Re of O(10(-2)). The new mixer design will benefit various microfluidic systems. 相似文献
3.
Reeve VE Widyarini S Domanski D Chew E Barnes K 《Photochemistry and photobiology》2005,81(6):1548-1553
Topical application of the isoflavone equol immediately following solar-simulated UV (SSUV) radiation exposure has previously been demonstrated to have significant photoprotective effects. Equol reduced both the inflammatory edema and the systemic suppression of the contact hypersensitivity reaction in hairless mice. Furthermore, daily topical equol application immediately following irradiation during a 10-week chronic SSUV exposure regime also reduced photocarcinogenesis severity in the mouse. This study examines the potential for topical equol to prevent photoaging in response to chronic SSUV irradiation for up to 30 weeks. We did not find consistent expression of the characteristic markers of photoaging until 30 weeks, although moderate epidermal hyperplasia and a transient increase in dermal mast cell numbers were evident after 1 week. Daily application of 10 muM equol lotion significantly reduced these early changes. However after 30 weeks of SSUV exposure, photoaging was well developed, as shown histologically by markedly increased epidermal hyperplasia, increased dermal mast cell number, pronounced focal elastotic deposits, degraded dermal collagen and deposition of glycosaminoglycans in the lower dermis. Topical equol treatment protected significantly from each of these impairments, as demonstrated histologically and quantitatively. Additionally, equol was found to have strong antioxidant action against acute UVA (320-400 nm)-induced lipid peroxidation of mouse skin, this property accounting for its antiphotoaging mechanism. The evidence for equol's antiphotoaging activity, taken together with its anti-inflammatory, immunoprotective and anticarcinogenic efficacy against SSUV irradiation in the mouse, suggests that equol could be developed as a helpful topical photoprotective agent for daily use by humans. 相似文献
4.
A new type of latex particle was prepared by copolymerization of styrene and poly(ethylene oxide) macromonomer. By controlling the concentration of styrene in reaction mixtures, several latexes with different grain sizes were obtained. The packing patterns of the latex films as well as shapes and sizes of the latex particles were measured with atomic force microscopy (AFM). AFM images revealed that the grain sizes of the latexes increase with increasing concentration of styrene. At a higher styrene concentration (10 wt%), the latex showed a rather homogenous distribution of grain sizes. Lateral force microscopy (LFM) was used to reveal frictional features of latex particles. Contact and non-contact mode AFM were employed to image the same sample of the latex films. The results show that AFM working in non-contact mode can be used to effectively eliminate the horizontal-line-like artifacts, which may obscure AFM images. 相似文献
5.
An automated gas chromatographic system was constructed to easily adapt either the cryogenic trap or chemical sorbent trap for preconcentrating ambient levels of volatile organic compounds. Remarkable similarity in chromatograms from C3 to C10 was found between these two enrichment methods, except that the sorbent trap did not quantitatively trap the C2-hydrocarbons. In contrast to cryogenic trapping, the chromatographic conditions for more volatile compounds were substantially improved using the sorbent trap. Water interference on the porous-layer open tubular column was also better managed using the sorbent trap for the continuous analysis of humid room air. The similarity in peak profiles between the GC-flame ionization detection (FID) and a commercial GC-MS system, regardless of concentration levels, facilitated compound identification on the FID chromatograms based on a field mission involving analysis of 106 air samples. 相似文献
6.
L. M. Gan C. H. Chew J. H. Lim K. C. Lee L. H. Gan 《Colloid and polymer science》1994,272(9):1082-1089
The polymerization of styrene in ternary microemulsions stabilized by the cationic surfactant tetradecyltrimethylammonium bromide was studied as a function of concentrations of water-soluble (potassium persulfate, KPS) and oil-soluble (AIBN) initiators. At a particular molar ratio of the initiators, similar maximum rates of polymerization can be achieved from using both types of the initiators. In addition, both initiated systems produced microlatexes with similar hydrodynamic radius, number of polymer particles, molecular weight of polystyrene and number of polymer chain per latex particle. But the dependencies of these latex parameters on concentrations of KPS and AIBN may not be the same. The polymerization mechanism appears to be similar, irrespective of using KPS or AIBN. It is discussed in terms of effective radicals produced for the polymerization. While the different dependencies of some latex parameters on concentrations of the initiators are attributed to the different efficiencies of the initiators in producing effective radicals. 相似文献
7.
8.
It is proposed that on the quantum surface of a topological-expansion surface pair the lepton be associated with a 2-triangle ? \(\bar I\bar Y\) ? band whose perimeter is built from the same two peripheral \(\bar I\) -triangle edges that constitute an antiquark's contribution to a hadron-disk perimeter. Although all lepton “internal” degrees of freedom are in one to one correspondence with antiquark attributes, it is shown that the simplest representation of quarkgeneration (Cabibbo) mixing cannot be invoked for leptons. The proposed lepton contains a neutral \(\bar Y\) triangle and permits a topological representation of baryon-lepton mixing. Described in parallel is a quantum-classical surface pair to represent the (standard) electroweak leptonic current. 相似文献
9.
Yulong Kuang Hui Cao Haidi Tang Junhong Chew Wei Chen Xiangcheng Shi Jie Wu 《Chemical science》2020,11(33):8912
Deuterium labelled compounds are of significant importance in chemical mechanism investigations, mass spectrometric studies, diagnoses of drug metabolisms, and pharmaceutical discovery. Herein, we report an efficient hydrogen deuterium exchange reaction using deuterium oxide (D2O) as the deuterium source, enabled by merging a tetra-n-butylammonium decatungstate (TBADT) hydrogen atom transfer photocatalyst and a thiol catalyst under light irradiation at 390 nm. This deuteration protocol is effective with formyl C–H bonds and a wide range of hydridic C(sp3)–H bonds (e.g. α-oxy, α-thioxy, α-amino, benzylic, and unactivated tertiary C(sp3)–H bonds). It has been successfully applied to the high incorporation of deuterium in 38 feedstock chemicals, 15 pharmaceutical compounds, and 6 drug precursors. Sequential deuteration between formyl C–H bonds of aldehydes and other activated hydridic C(sp3)–H bonds can be achieved in a selective manner.A selective hydrogen deuterium exchange reaction with formyl C–H bonds and a wide range of hydridic C(sp3)–H bonds has been achieved by merging tetra-n-butylammonium decatungstate photocatalyst and a thiol catalyst under 390 nm light irradiation. 相似文献
10.
Peirong Chen Ly May Chew Aleksander Kostka Kunpeng Xie Martin Muhler Wei Xia 《Journal of Energy Chemistry》2013,22(2):312-320
Oxygen- and nitrogen-functionalized carbon nanotubes (OCNTs and NCNTs) were applied as metal-free catalysts in selective olefin hydrogenation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 °C led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis. 相似文献