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排序方式: 共有651条查询结果,搜索用时 15 毫秒
61.
Mikaël Ramos da Silva Christian Schroeder Jean-Claude Verbrugge 《International Journal of Rock Mechanics and Mining Sciences》2010,47(5):797-807
This paper presents the results of an experimental study carried out on a porous, water-saturated limestone. First, a set of poroelastic parameters is obtained from a wide range of experiments (drained, undrained, pore pressure loading and unjacketed tests) conducted on the same sample at the same stress state. A “null” test, inspired from unsaturated soil testing, is added to confirm the previous results, in particular the value of the Biot coefficient. Then, the variation of the measured parameters between samples is investigated. Finally, the influence of the stress state is studied in the framework of semilinear poroelasticity. Several expressions are compared to model the evolution of the drained bulk modulus as a function of Terzaghi's effective stress. 相似文献
62.
Isabelle Bisotto Ethirajulu S Kannan Jean-Claude Portal Devin Brown Thomas J Beck Yuriy Krupko 《Science and Technology of Advanced Materials》2014,15(4)
In this work, we studied the photovoltage response of an antidot lattice to microwave radiation for different antidot parameters. The study was carried out in a Si/SiGe heterostructure by illuminating the antidot lattice with linearly polarized microwaves and recording the polarity of induced photovoltage for different angles of incidence. Our study revealed that with increased antidot density and etching depth, the polarity of induced photovoltage changed when the angle of incidence was rotated 90 degrees. In samples with large antidot density and/or a deeply etched antidot lattice, scattering was dominated by electron interaction with the asymmetrical potential created by semicircular antidots. The strong electron–electron interaction prevailed in other cases. Our study provides insight into the mechanism of interaction between microwaves and electrons in an antidot lattice, which is the key for developing an innovative ratchet-based device. Moreover, we present an original and fundamental example of antidot lattice etching through the use of a two-dimensional electron gas. This system deals with a hole lattice instead of an electron depletion in the antidot lattice region. 相似文献
63.
超短高功率脉冲激光与物质相互作用及其应用 总被引:6,自引:1,他引:5
超短高功率脉冲激光系统的小型化实用化极大地促进了激光与物质相互作用的物理和应用研究。回顾加拿大魁北克大学国立科学研究院材料研究所(简称INRS)的超短高功率脉冲激光产生高温高密度等离子体的最新研究成果及其在分子物理和辐射约束高温高密度等离子体物理中的应用。 相似文献
64.
Networks and Spatial Economics - 相似文献
65.
We have experimentally studied the distribution of contact forces within two-dimensional granular packings with binary size distribution, composed of water-softener salt disks of uniform thickness, under an oedometric compression. We propose a simple experimental method based on the measurement of contact area to determine the forces that act at the point of contact between disks loaded in their plane. We confirm experimentally the results of numerical simulations on contact force distributions within two-dimensional packings of disks under an oedometric compression. 相似文献
66.
Nahla Noureddine Naima Zerrouk Ioannis Nicolis Patrick Allain Souad Sfar Jean-Claude Chaumeil 《Drug development and industrial pharmacy》2005,31(4):397-404
After oral administration, drug absorption rate is recognized to be dependent on two major factors: dissolution and intestinal cells permeability. Caco-2 monolayer cells have been largely used as a permeation study model. In this study, a numerical approach funded on an exponential first-order time relationship was tested to compare immediate- and controlled-release tablets of theophylline using a dissolution-permeation system. The dissolution performance using USP II paddle apparatus was coupled to the permeability studies investigated in Caco-2 cell monolayers. The dissolved samples were taken at different times; their pH and osmolarity were adjusted to render them suitable to Caco-2 permeability studies (osmolarity = 300 mosm, pH = 7.4). The experimental data show that the dissolution fits the exponential first-order relationship rate. The permeability values were in a range of 4.45 10- 6-5.28 10- 6 cm/s, and percentages of absorbed drug dose were dependent on the fraction initially present in the donor compartment, indicating that absorption of theophylline was dissolution rate limited. Plotting experimental absorbed fractions (Fa) against experimental dissolved fractions (Fd) show that permeation is the rate-limiting step in drug absorption process in the extended release form of theophylline. Our results demonstrate a general agreement between observed Fa/Fd relationships and theoretical Fa/Fd relationships obtained with our approach funded on dissolution and permeation behavior. We concluded that the couple dissolution-caco-2 system could be a useful tool to characterize intestinal permeation for a new formulation of a drug compared with the conventional one. 相似文献
67.
Martina Aigner Jean-Claude Fardeau Felipe Zapata 《Nutrient Cycling in Agroecosystems》2002,63(1):49-58
Experiments have been carried out in acid soils developed under tropical climates with and without phosphate rock (PR) addition to assess the ability of the Pi strip method to extract available soil P compared with the Isotopic Exchange Kinetics method (IEK). In the Pi strip method strips of filter paper, previously impregnated with iron hydroxide acting as a sink for phosphate ions from soil components, are added to an aqueous soil suspension. The extracted phosphate ions are eluted in diluted sulfuric acid and quantified by a colorimetric method. Available soil P, defined as the amount of phosphate ions that can move from the soil particles to soil solution, is described by three factors: an intensity factor, a quantity factor and a capacity factor. These three factors were determined by the IEK-method. Following the addition of carrier-free 32PO4-ions to soil, the ability of the Pi strip to extract available soil P was assessed: (i) by comparing the quantity of instantaneously exchangeable P (E1) to the quantity extracted with the Pi strip; (ii) by determining the fraction of 32P extracted with the Pi strip, and (iii) by comparing the specific activity (SA) of P present as phosphate ions extracted by the Pi strip to the specific activity of P in the soil solution. It was observed that (i) E1 and the amount extracted with the Pi strip are highly correlated, (ii) the recovery of 32P extracted by the Pi strip varies between 17 and 66%, and (iii) the specific activity of P extracted by the Pi strip is of the same order of magnitude as that of P in the soil solution. In acid soils low in available P, part of the P in aqueous KCl-extracts is presumably not only present as free phosphate ions but also occluded in the form of a soluble complex, whose isotopic exchangeability is significantly lower than that of phosphate ions transferred to the Pi strip. It is concluded from the results that the Pi strip method can be recommended in routine analysis for the determination of the quantity factor. However, this method cannot provide intensity or capacity factors and therefore needs to be complemented by the IEK-method for full characterization of the available soil P status. 相似文献
68.
Michel Bayard Jean-Claude Grenier Michel Pouchard Paul Hagenmuller 《Materials Research Bulletin》1974,9(9):1137-1142
Magnetic susceptibility and magnetization measurements on V3O7 from 4,2 to 600 K characterize a paramagnetic behaviour above 18 K : the samples follow a Curie-Weiss law with a Curie constant in good agreement with a spin only value per V4+. At lower temperature the magnetic ordering may be attributed to a metamagnetic behaviour resulting from the layer type structure. 相似文献
69.
Jean-Pierre Larpin Jean-Claude Colson Denise Delafosse 《Materials Research Bulletin》1976,11(6):713-719
The sulfurisation of cuprous bromides and iodides in hydrogen sulfide, at low pressure, leads to the formation of a porous chalcosine layer, as already investigated in the case of chlorides. The step which fixes the conversion rate is the diffusion of the gaseous reagents in the pores of the sulfide formed. Experimental activation energies are 15 and 34 kcal.Mole?1 respectively, at every step of the reaction. 相似文献
70.