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991.
References: 《过程工程学报》2004,4(Z1):449-454
Arc Spray Nanoparticle Synthesis System (ASNSS) has been used to prepare the silver nanofluids in this study. The metal electrodes under the electrical discharge will melt and evaporate rapidly and condense to form the nanoparticles in the dielectric fluid at lower temperature and produce the suspended nanoparticle fluid. Thus, the mechanism of the ASNSS process is superheating the electrodes by plasma to form metallic nuclei and supercooling these nuclei by dielectric liquid to produce nanofluid. This study considers the different controlling parameters such as discharge current,discharge voltage, pulse-duration time, electrode diameter, and the temperature of dielectric liquid. The optimally operated parameters can be obtained to produce the finer particle size in nanofluid. The results indicate the silver electrodes in alcohol fluid will produce the spherical nanosilver particles. The mean particle size of silver in different dielectric liquid temperatures of-40, -20, 0, and 10℃ is about13.4, 15.8, 17.5, and 21.6 nm, respectively. This indicates that the well suspended fluid can be obtained by controlling the lower dielectric fluid temperature. 相似文献
992.
993.
994.
Chih-Sheng Chang Shun Lien Chuang 《IEEE journal of selected topics in quantum electronics》1995,1(2):218-229
A complete model with the spin-orbit coupling for strained quantum-well lasers is presented. Explicit formulas for the momentum-matrix elements are given. The improvement in the threshold current density of tensile strained quantum-well lasers, as compared with that of the unstrained quantum well, is shown to result from the enhanced momentum matrix. The differential gain and the linewidth enhancement factor are calculated. The theoretical results show a smaller linewidth enhancement factor for compressively and tensile strained quantum wells than that of the unstrained structure, as has been experimentally observed. The temperature behavior of both the radiative component and the Anger component of the threshold current density is shown. Due to a decrease of gain and differential gain with increasing temperature, the threshold carrier density in unstrained quantum wells is increased with a large increment of the Auger recombination current at high temperature. For strained quantum wells, this increment is moderate because of the smaller threshold carrier density 相似文献
995.
在负偏压设计过程中,采用变压器存在体积大、周期长、效率低等弊端;极性反转型控制器难于控制传导EMI线形传送所带来的干扰;充电泵电路则存在噪声较大、功率较小等缺点。介绍的新型CUK型变换器,旨在实现一种高效、低成本、输出电压纹波极低的负偏压设计方案。 相似文献
996.
Ying-Yu Chuang Rainer Schmid Y. Austin Chang 《Metallurgical and Materials Transactions A》1985,16(2):153-165
An empirical mathematical equation is proposed for the magnetic contribution to the specific heat of pure metals. The corresponding
functions for enthalpy, entropy, and Gibbs energy are of simple form. Two parameters used for each element are the critical
temperature,T
c, and the total magnetic entropy. The parameters have been determined from a careful separation of magnetic and nonmagnetic
contributions to the specific heat. Debye temperatures for Ni, Co, and Fe have been determined considering data to much higher
temperatures than other studies. The magnetic specific heats extracted from experimental data agree very well with the proposed
equation over the entire temperature range and for all three elements. Comparisons with different mathematical functions found
in the literature give agreement only for the case of iron. The total magnetic entropy given by a classical relation is found
to be high, and a quantitative correction is given. Various magnetic standard states are discussed. The lattice stabilities
of bcc- and fcc-iron are calculated assuming that the difference of the nonmagnetic specific heats is linear from 500 K to
1810 K. A simple equation is obtained in which the anomalous temperature dependence is explained by the independently determined
magnetic contribution. The calculated values agree very well with Orr and Chipman’s assessment. The stability of bcc iron
at low temperatures is quantitatively rationalized. 相似文献
997.
The majority of the GTP-binding proteins of the Ras superfamily hydrolyze GTP to GDP very slowly. A notable exception to this are the Rac proteins, which have intrinsic GTPase rates at least 50-fold those of Ras or Rho. A protein (or proteins) capable of inhibiting this GTPase activity exists in human neutrophil cytosol. Since Rac appears to exist normally in neutrophils as a cytosolic protein complexed to (Rho)GDI, we examined the ability of (Rho)GDI to inhibit GTP hydrolysis by Rac. (Rho)GDI produced a concentration-dependent inhibition of GTP hydrolysis by Rac1 that paralleled its ability to inhibit GDP dissociation from the Rac protein. Maximal inhibition occurred at or near equimolar concentrations of the GDI and the Rac substrate. The ability of two molecules exhibiting GTPase activating protein (GAP) activity toward Rac to stimulate GTP hydrolysis was also inhibited by the presence of (Rho)GDI. The inhibitory effect of the GDI could be overcome by increasing the GAP concentration to levels equal to that of the GDI. (Rho)GDI weakly, but consistently, inhibited GTP gamma S (guanosine 5'-3-O-(thio)triphosphate) dissociation from Rac1, confirming an interaction of (Rho)GDI with the GTP-bound form of the protein. These data describe an additional activity of (Rho)GDI and suggest a mechanism by which Rac might be maintained in an active form in vivo in the presence of regulatory GAPs. 相似文献
998.
Ying-Chu Hoh Wen-Shou Chuang Peng-Shiung Yueh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(1):41-47
The fundamental aspects of the extraction and stripping of platinum (II) from its chloride solution by Aliquat 336 diluted with toluene have been studied. The extraction and stripping was at 99.5 and 97.6% equilibrium within 30 s and 20 min respectively. The percentage extraction increased slightly with decreasing hydrochloric acid concentration. In 0.1 mol dm?3 hydrochloric acid, 1.0 volume percent Aliquat 336 in toluene could load 9.8 mmol dm?3 of platinum (II). The percentage stripping of platinum (II) from Pt(II)-load organic solvent increased with increasing sodium bisulphite concentration. The enthalpy changes of extraction and of stripping were 12.8 and 114.9 kJ mol?1 respectively. Both of the reactions were endothermic. 相似文献
999.
Yue Chen Letaief K.B. Chuang J.C.-I. 《Selected Areas in Communications, IEEE Journal on》1998,16(9):1679-1690
This paper investigates the use of a maximum a posteriori probability (MAP) algorithm to realize soft-output equalization in a concatenated equalization and trellis-coded modulation (TCM) decoding-based wireless communication system. Specifically, we first begin with a general MAP algorithm and then focus on studying Bahl's (1974) MAP and Lee's (1974) MAP algorithms. We then propose a modified version of Lee's MAP algorithm which is much simpler than the original, in terms of complexity, and is more practical. In particular, a very simple channel estimation method which employs orthogonal training sequences is proposed. In order to improve the system performance, equal-gain combining and selection diversity are also considered. Finally, we compare the performance of the MAP algorithm-based equalization with our previously proposed equalization scheme, which combines decision feedback equalization and TCM 相似文献
1000.
To achieve the optimal trade-off between economies and operability, simplifications of heat exchanger networks (HENs) are required. To do so, identifications of heat load loops and downstream paths are necessary. This paper proposes new methods for identifications of independent and dependent loops as well as downstream paths in HENs, respectively. Stream table and node adjacency matrix are defined in this paper to represent the structures of HENs. Based on graph theory, identification of loops in HENs is decomposed into three procedures: (a) finding a maximal tree, (b) identifying a maximal set of independent loops and (c) searching all loops. Locating the downstream paths in HENs is accomplished by finding directed trees which are generated by modifying the procedure for finding a maximal tree. A complex network with a splitting stream is used for detailed illustrations of the procedures. 相似文献