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991.
Generalized transforms for decomposing a signal in terms of discrete orthogonal transformation are developed. General relationships for factoring the transform matrices into a product of sparse matrices are derived. Efficient algorithms for fast computation of these transforms is a consequence of these sparse matrices. The flow graphs and hence the sequence of computations are identical for all the transforms with only the multipliers as the variables for the different transforms. 相似文献
992.
The work of adhesion, depending solely on the contact angle and surface tension, is unreliable as a guide to the strength of a joint. The kinetics of joint formation, exemplified by the rate of wetting, is also important and can be measured by rate of change of contact angle, a process for which an empirical equation has previously been suggested. A proposed mechanism introduces a viscosity term into the differential form of this equation.
A series of metal lacquers was prepared from epoxy, U/F and M/F resins in various ratios and also epoxy/P/F and epoxy/acrylic mixtures. Stainless steel substrates, coated with these lacquers were then cemented together using polyethylene as an adhesive. It is shown that joint strength correlates better with a high wetting constant (γ/ηL) than with a low contact angle except where this is very low. 相似文献
A series of metal lacquers was prepared from epoxy, U/F and M/F resins in various ratios and also epoxy/P/F and epoxy/acrylic mixtures. Stainless steel substrates, coated with these lacquers were then cemented together using polyethylene as an adhesive. It is shown that joint strength correlates better with a high wetting constant (γ/ηL) than with a low contact angle except where this is very low. 相似文献
993.
Pro- and Antioxidants in the Field of Fats XXVI: Anthochlores of Dahlia variabilis and Cosmos sulphureus The authors have determined the antioxidative activity of the anthochlor pigments of Dahlia variabilis and Cosmos sulphureus on methyl linoleate. It was found that the aglycones butein and sulphuretin exhibit stronger antioxidative action than the chalkone aglycone 2″,4,4″-trihydroxy chalcone. During the treatment of the two flowers, a splitting of the glycosides was observed. In the freshly cut Cosmos sulphureus variety no aglycones could be detected. Furthermore, the distribution of anthochlores in the various series of petals in Dahlia variabilis and Helichrysum bracteatum was studied. 相似文献
994.
A. H. M. Ahmed L. S. Dent Glasser 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1971,21(4):109-112
Two compounds of formula BaO.Al2O3.2H2O have been synthesised and studied by infra-red, X-ray and thermal analytical techniques. One form yielded another crystalline product, BaO.Al2O3.0.5H2O, as an intermediate during dehydration. The results are interpreted in terms of the known crystal structure of one of the forms of the dihydrate. 相似文献
995.
The relationship of parental psychosocial competence to parent interaction behaviors in a joint problem-solving/play session was studied in 23 adult–preschool child pairs. Parents were assessed using self-report questionnaires to determine degrees of self-efficacy, optimistic trust, and an active, competent coping style. Children and parents participated in a semistructured problem-solving/play task with observers rating the parental behaviors in the interactions; child responses were not specifically studied. More competent parents treated the child as being more capable and resourceful, showed generally warm and positive feelings, and were more helpful with problem solving. Thus, these parental competence attributes are confirmed as significant variables relating to parental behavior and to their styles of interaction, which are part of the socialization context of their children. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
996.
Effect of extrusion temperature, screw speed and moisture content on the gelatinisation properties of extruded corn starch using a single-screw extruder were studied using response surface methodology. The degree of gelatinisation can be effectively controlled by controlling the moisture content of the raw material and the extrusion temperature; control by manipulation of screw speed is also possible when the raw material has a high moisture content. The extrudate produced from starch with a low moisture content exhibited a very low retrogradation capacity, which was independent of the screw speed. It was evident that variation of operating conditions permits the production of an extrudate with various technological characteristics to meet varying food and industrial applications, and the use of response surface analysis seems to be an effective means of studying and optimising these conditions for extrusion technology. 相似文献
997.
Ahmed K. Noor Jeanne M. Peters 《Computer Methods in Applied Mechanics and Engineering》1981,28(2):217-240
A reduced basis technique and a problem-adaptive computational algorithm are presented for predicting the post-limit-point paths of structures. In the proposed approach the structure is discretized by using displacement finite element models. The nodal displacement vector is expressed as a linear combination of a small number of vectors and a Rayleigh-Ritz technique is used to approximate the finite element equations by a small system of nonlinear algebraic equations.To circumvent the difficulties associated with the singularity of the stiffness matrix at limit points, a constraint equation, defining a generalized arc-length in the solution space, is added to the system of nonlinear algebraic equations and the Rayleigh-Ritz approximation functions (or basis vectors) are chosen to consist of a nonlinear solution of the discretized structure and its various order derivatives with respect to the generalized arc-length. The potential of the proposed approach and its advantages over the reduced basis-load control technique are outlined. The effectiveness of the proposed approach is demonstrated by means of numerical examples of structural problems with snap-through and snap-back phenomena. 相似文献
998.
Diketostearic acid 9:10 is readily and speedily oxidized by peracetic acid, at low temperatures to high yields of azaleic
acid and nonanoic acids. 相似文献
999.
Multiple steady states are known to be possible in many types of chemical reactor due to the non-linear dependence of reaction rate on either temperature or reactant concentration. It is reasoned in this study that multiple steady states can also exist in a gas-solid fluidised bed reactor. The calculations are based on the two-phase theory of fluidisation and on the important assumption that the interstitial phase gas in completely mixed. Both thermal and concentration multiplicites are shown to be possible. 相似文献
1000.
M.?Abo-ZahhadEmail author A.?Al-Smadi S.?M.?Ahmed 《Electrical Engineering (Archiv fur Elektrotechnik)》2004,86(4):219-227
Wavelets have recently emerged as a powerful tool for signal compression, particularly in the areas of image, video, and audio compression. In this paper, we present a low-complexity wavelet-based audio compression algorithm that is capable of handling fairly arbitrary audio sources. The algorithm transforms the incoming audio data into the wavelet domain, and compresses data by exploring redundancy in the wavelet coefficients and exploiting the large runs of zeros in the transformed signal. Also there is a possibility of applying a threshold to the non-zero coefficients, thus a further increase in the number of zeros is expected. The audio signal is first preprocessed to scale down the wavelet coefficients. Then the preprocessed signal is wavelet transformed using a bi-orthogonal discrete wavelet transform (DWT) and threshold by applying energy compaction strategy. Encoding represents the threshold coefficients in compact form. A new encoding technique that is easy to implement, and that provides a reasonable compression ratio for a certain acceptable distortion level has been developed to encode the threshold DWT. So, a bit rate can be controlled such that the algorithm operates at virtually any pre-selected bit rate. The motivation of using the bi-orthogonal wavelet transform is that it permits the use of a much broader class of filters, and this class includes symmetric linear phase filters. The superior performance of this algorithm is also demonstrated by comparing it with two other popular audio compression techniques and this meets the requirements of multimedia computing. 相似文献