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31.
The authors study the performance of a multichannel modulation method for asymmetric digital subscriber lines (ADSLs) and very high-speed digital subscriber lines (VHDSLs). In the ADSL case, over all unloaded North American subscriber lines in the test set, a unidirectional 1.536 Mb/s data rate service from the end office to the customer premises is possible on a single twisted pair at an error rate of 10-7 with at least a 6 dB margin used coded multichannel modulation with sufficient transmit power. In the VHDSL case, data rates in excess of 100 Mb/s can be transmitted reliably, at an error rate of 10-7, using uncoded multichannel modulation on a single twisted pair over a distance ⩽150 ft with a sufficiently high sampling rate (≈24 MHz) and transmit power. It is shown that a cost-effective multichannel transceiver design suggested for high-speed digital subscriber line (HDSL) service will also work well for ADSL and VHDSL services with only minimal modifications 相似文献
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An anisotropic theory of elasticity for continuum damage mechanics 总被引:47,自引:0,他引:47
This paper presents the development of an anisotropic elastic damage theory. This is achieved by deriving a modified damage effect tensor M(D) for the effective stress equations capable of including the effect of anisotropic material damage. The modified tensor removes the restriction of a priori knowledge of the directions of principal stresses imposed by a damage effect tensor developed earlier and can now be made for general practical engineering applications of failure analysis. Reduction of the proposed tensor to a scalar for isotropic damage is shown to be possible when it is expressed not only in the principal directions but also in any arbitrary coordinate system, a necessary condition to verify the validity of the proposed tensor. Uniaxial tension and pure torsion are chosen to illustrate the application of the theory as well as associated damage variables that may be experimentally determined using laboratory size specimens. The measured damage variables confirm the presence of anisotropic damage from an initially isotropic material specimen and the magnitude is more pronounced at higher stresses and strains.
Résumé On présente un développement d'une théorie sur l'endommagement élastique anisotrope en déduisant un tenseur modifié décrivant l'effet de l'endommagement pour un système d'équations de contraintes effectives susceptible d'inclure l'effet d'un endommagement dans un matériau anisotrope. Le tenseur modifié supprime la restriction de la connaissance a priori des directions des contraintes principales imposées par un tenseur d'effet d'endommagement développé précédemment; il peut à présent entrer dans les applications pratiques en construction de l'analyse des ruptures.On montre qu'il est possible de réduire le tenseur proposé à une valeur scalaire dans le cas d'un dommage isotrope, dès lors qu'il est exprimé non seulement suivant les directions principales, mais dans un système de coordonnées arbitraires, ce qui est une condition nécessaire pour en vérifier la validité.On choisit une traction multiaxiale et une torsion pure pour illustrer l'application de la théorie ainsi que des variables d'endommagement associées, susceptibles d'être déterminées expérimentalement à l'aide d'éprouvettes de laboratoire.Les variables d'endommagement mesurées confirment la présence d'un dommage anisotrope dans le cas d'une éprouvette d'un matériau initialement isotrope; son amplitude est plus prononcée à des contraintes ou des déformations plus importantes.相似文献
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Suk Lee Kyung Chang Lee Man Hyung Lee Harashima F. 《Industrial Electronics, IEEE Transactions on》2002,49(3):693-701
This paper focuses on a method to integrate mobile devices such as a mobile robot, automated guided vehicle, and unmanned container transporter to form an automated material handling system. In this paper, the stationary devices are connected via a Profibus network while the mobile devices are communicating via an IEEE 802.11 wireless LAN. In order to integrate these two networks, a protocol converter is developed on a PC platform that runs two interacting processes with shared internal buffers. The protocol converter performs a role of translator between two different protocols by converting the format of a data frame. In addition to this basic conversion function, the protocol converter has a virtual polling algorithm to reduce the uncertainty involved in accessing the wireless network. Finally, the integrated network. of Profibus and IEEE 802.11 is experimentally evaluated for its data latency and throughput, which shows the feasibility of the Profibus-IEEE 802.11 network for industrial applications involving mobile devices 相似文献
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A simple and accurate formula for calculating the grounding grid resistance is proposed in this paper. This method is based on a theoretical manipulation of the numerical moment method and of the current image. The formula is dependent on the substation grounding grid design, such as grid depth, grid size, number of meshes, grid-conductor diameter, etc. A comparison study is performed to check the accuracy of the proposed formula with respect to six different formulas and methods in the literature. An excellent agreement was found between the results of this formula and the results of a sophisticated computerized method 相似文献
40.
Sung Ho Jeong Joon Jeong Yi Jong Keun Kim Man Yeong Ha 《Journal of Mechanical Science and Technology》1991,5(1):16-21
A computer program to calculate the strip temperature heated in the continuous annealing furnace was developed, using the
zone method for radiative heat transfer analysis with the measured gas temperature in the furnace. Using theF
E Operator, the present study considered the effects of soot and transient species, in addition to the H2O−CO2 gas mixture on the gas radiative heat transfer. The predicted strip temperature distribution forF
E=1.05 represented well the measured data. The maximum difference in the heat flux transfered to the strip from the combustion
gas forF
E=1.0 (without soot and transient species gas radiation) and 1.05 (with soot and transient species gas radiation) was about
15%. The present study also investigated the effects of line speed and thickness variations on the strip temperature, establishing
the bases for the on-line computer model. 相似文献