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121.
122.
In activation of hydrogen storage alloys, the nickel-group metals, especially Pd, act as the catalysts to dissociate hydrogen and turn the alloys into successful hydrogen absorbers. The Laves phase Sc and Zr alloys with Cr–Mn as common components exhibit extraordinary hydrogen activation properties matching Pd. Through a cracking mechanism, the bulk samples of these alloys rapidly absorb hydrogen at sub-atmospheric pressures and room-temperature, achieve absorption performance of those Pd surface-modified alloys, meanwhile retaining good reversibility. Among them, the ScCrMn exhibits significantly higher absorption rate than Pd, whereas, the ZrCrMn shows similar absorption kinetics and reversibility to Pd. The shortest initial-activation-time, highest initial-activation-rate and lowest allowed-activation-pressure achieved by ScCrMn are 15 s, −16.6 kPa/s and 0.46 kPa, respectively, in comparison with those of 18 s, 3.2 kPa/s and 0.13 kPa for Pd powder measured under equivalent conditions. The findings and associated magnetization measurements indicate that Cr and Mn upon alloying with certain lower valence metals possess surface electronic structures highly beneficial to hydrogen dissociation. 相似文献
123.
Spatially resolved extrinsic photoresponse experiments in pentacene two terminal devices without or under additional intrinsic bias-light excitation are employed. These experiments are used to investigate the microscopic mechanism of the recently observed phenomenon of the photoresponse enhancement under additional bias-light intrinsic excitation and to preclude that this phenomenon arises from contact-related artifacts. It is found that the extrinsic photogeneration near the contacts via electric field-assisted exciton splitting and/or light-induced depletion width-reduction have a negligible contribution to the extrinsic photoresponse. Under additional bias-light intrinsic excitation, a uniform increase of the photogenerated hole density is found to take place across the whole conduction channel, without changes in the electric field distribution and in the interfacial properties of the contacts. The photoresponse enhancement by the blue bias-light becomes stronger upon increasing the red-light intensity. A nearly square root dependence of the photoresponse enhancement on the blue bias-light intensity is found. It is shown that the observed dependence of the photoresponse enhancement on the light intensities of the extrinsic and intrinsic excitation can be explained with the extrinsic photogeneration mechanism based on hole detrapping by triplet exciton dissociation. 相似文献
124.
《Journal of Nuclear Science and Technology》2013,50(4):426-430
Laser isotope separation experiments of Gd and B by atomic and molecular methods, respectively, have been performed. Gadolinium-157 was selectively photoionized by means of three linearly polarized dye lasers, the excitation process of which is based on the polarization selection rules. The effect of magnetic field on isotopic selectivity was discussed. 10BCl3 was selectively photodissociated through IR multiphoton dissociation by the irradiation of TEA CO2 laser or free electron laser (FEL). Selectivity was improved by two-color laser irradiation. 相似文献
125.
A chemo-thermo-mechanically coupled analysis of ground deformation induced by gas hydrate dissociation 总被引:1,自引:0,他引:1
Sayuri Kimoto Fusao Oka Tomohiko Fushita 《International Journal of Mechanical Sciences》2010,52(2):365-3536
We present a numerical analysis of gas hydrate dissociation in hydrate-bearing sediments in the seabed ground. Behavior of multiphase materials has been described within the framework of a macroscopic continuum approach through the use of the theory of porous media. The proposed simulation method has been developed based on chemo-thermo-mechanically coupled analysis, taking into account phase changes from solids to fluids, that is, water and gas, flow of water and gas, heat transfer, and ground deformation. From the numerical results, it has been found that ground deformation is induced by generation and dissipation of water and gas, and by reduction of soil strength due to the loss of hydrates. 相似文献
126.
The values of bond dissociation energies, BDE, of the weakest N–N bonds and total energies, Etotal, of molecules have been calculated for 14 cyclic nitramines by means of the UB3LYP/6-31G? and UB3LYP/6-31 + G? // PM3 methods. The relationships found between the BDE values and logarithms of impact sensitivity of these nitramines, expressed as drop energy, Edr, are not unambiguous. Replacement of these BDE values by the BDE/Etotal ratio has not resulted in any simplification of the said relationships, but their quality improved, particularly with application of the UB3LYP/6-31 + G? // PM3 (UHF) method. The reason of ambiguity of the relationships found mainly lies in real conformation of the respective molecules and intermolecular force effects in real molecular crystals, which are included in neither of the two calculation methods. 相似文献
127.
This study tested a dynamic field theory (DFT) of spatial working memory and an associated spatial precision hypothesis (SPH). Between 3 and 6 years of age, there is a qualitative shift in how children use reference axes to remember locations: 3-year-olds’ spatial recall responses are biased toward reference axes after short memory delays, whereas 6-year-olds’ responses are biased away from reference axes. According to the DFT and the SPH, quantitative improvements over development in the precision of excitatory and inhibitory working memory processes lead to this qualitative shift. Simulations of the DFT in Experiment 1 predict that improvements in precision should cause the spatial range of targets attracted toward a reference axis to narrow gradually over development, with repulsion emerging and gradually increasing until responses to most targets show biases away from the axis. Results from Experiment 2 with 3- to 5-year-olds support these predictions. Simulations of the DFT in Experiment 3 quantitatively fit the empirical results and offer insights into the neural processes underlying this developmental change. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
128.
This article presents a potential synthesis between the fitness indicator and life history models of human intelligence through consideration of the phenomena of ability differentiation and integration. The cognitive differentiation-integration effort hypothesis proposes that these effects result from a life history tradeoff between cognitive integration effort, a mating effort component associated with strengthening the positive manifold amongst abilities; and cognitive differentiation effort, a somatic effort component associated with the cultivation of specific abilities. This represents one of two largely independent sources of genetic variance in intelligence; the other is mediated by general fitness and mutation load and is associated with individual differences in levels of 'genetic g'. These two sources (along with a common source of environmental variance) combine to give rise to a variety of cognitive phenotypes characterized by different combinations of high or low levels of 'genetic g' and cognitive specialism or generalism. Fundamental to this model is the assumption that measures of life history speed (K) and g are essentially independent, which is demonstrated via meta-analysis of 10 studies reporting correlations between the variables (ρ = .023, ns, n = 2056). The implications of the model are discussed in an evolutionary, ecological, and developmental context. Seven key predictions are made in the discussion which if tested could provide definitive evidence for the hypothesis. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
129.
130.
针对体育场馆类空旷大跨度结构的设计特点,运用有限元程序,对某公司文化体育中心结构的整体受力性能、薄弱部位及大跨度网架屋盖对主体结构受力性能的影响与协同工作等问题进行了模拟分析.计算表明,此类结构具有扭转不规则性,薄弱部位常出现在空旷结构部位和弱连接部位;空旷框架部分存在相对变形大的现象.由于框架柱缺乏有效约束,其计算长度较大,P-△效应明显;网架屋盖在水平力及地震作用下对主体结构有不可忽视的作用,应考虑网架屋盖与下部框架结构的协同工作.实际设计中可考虑将网架部分按照一定的规则等代为钢梁,来近似考虑网架的刚度进行整体设计. 相似文献