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排序方式: 共有792条查询结果,搜索用时 15 毫秒
81.
Wood samples and veneers of Hevea brasiliensis (Rubber wood) and Acacia auriculaeformis treated with aqueous solutions of chromium trioxide, ferric chloride and ferric nitrate were studied for water repellency and their reaction with wood constituents. FTIR spectra obtained from wood surface treated with chromium trioxide indicate the formation of a water insoluble complex between chromium trioxide and aromatic ring of lignin, whereas no reaction takes place with ferric salts. Treatment of wood by chromium trioxide was found to be effective in imparting water repellency in wood. 相似文献
82.
Anu Bajaj Atul Khanna Narendra K. Kulkarni Suresh K. Aggarwal 《Journal of the American Ceramic Society》2009,92(5):1036-1041
Bismuth borate glasses from the system: 40Bi2 O3 –59B2 O3 –1Tv2 O3 (where Tv=Al, Y, Nd, Sm, and Eu) and three glasses of composition: 40Bi2 O3 –60B2 O3 , 37.5Bi2 O3 –62.5B2 O3 and 38Bi2 O3 –60B2 O3 –2Al2 O3 were prepared by melt quenching and characterized by density, UV-visible absorption spectroscopy and differential thermal analysis (DTA) studies. Bismuth borate glasses exhibit a very strong optical absorption band just below their absorption edge. Glasses were devitrified by heat treatment at temperatures above their glass transition temperatures and the crystalline phases produced in them were characterized by Fourier transform infrared (FTIR) absorption spectroscopy and X-ray diffraction (XRD). Bi3 B5 O12 was found to be the most abundant phase in all devitrified samples. DTA studies on glasses and FTIR and XRD analysis on crystallized samples revealed that very small amounts of trivalent ion doping causes significant changes in the devitrification properties of bismuth borate glasses; rare-earth ions promote the formation of metastable BiBO3 –I and BiBO3 –II phases during glass crystallization. 相似文献
83.
Collaborative filtering (CF), the most successful and widely used technique, recommends items based on the preferences of similar users. The main potentials of CF are its cross‐genre recommendation ability, and that it is completely independent of representation of the items being recommended. However, CF suffers from sparsity and cold start problems. On the other hand, a highly effective variant of content‐based filtering (CBF), reclusive methods (RMs) based on the preference of the single individual for whom recommendations to be made, provides a methodology that considers uncertainty and the multivalued nature of item features as well as user preferences in a content‐based framework using fuzzy logic approaches. The adoption of RM paradigm has several advantages when compared to CF such as sparsity and new item problem, but it suffers from overspecialization and limited content analysis. In view of the complementary nature of CF and RM, we develop a hybrid recommender system (RS) that helps in alleviating aforementioned problems in each approach. First, we propose fuzzy naïve Bayesian classifier based CF (FNB‐CF) and RM (FNB‐RM) for handling correlation‐based similarity problems. To overcome individual weaknesses of FNB‐CF and FNB‐RM, we develop a hybrid RS, FNB‐CF‐RM. Effectiveness of our proposed hybrid RS is demonstrated through experimental results using the MovieLens and IMDb data sets. 相似文献
84.
Manoj K. Sharma Arvind S. Ambolikar Suresh K. Aggarwal 《Journal of Materials Science》2011,46(17):5715-5722
In situ one-step chemical synthesis route for the preparation of a gold–polyaniline composite in nanopores of polycarbonate
(PC) membrane is reported. PC membrane, which was placed in a specially designed two-compartment cell, separated the aqueous
solution of aniline from HAuCl4 solution. Concentration gradient across the membrane caused movement of AuCl4
− and anilinium ions in the pores of polycarbonate membrane. Nanopores in PC membrane acted as reaction vessels where aniline
and HAuCl4 were allowed to mix together, and the redox reaction between aniline and HAuCl4 led to the formation of gold–polyaniline composite. The gold–polyaniline composite in PC membrane was characterised by EDXRF,
XRD, UV–Vis spectroscopy, FTIR and TEM. Peak broadening in XRD suggests that Au particles formed in the membrane are nanocrystallites
and average crystallite size is (24 ± 4) nm. TEM studies show that gold nanoparticles are randomly dispersed in polyaniline
clusters formed in the nanopores of PC membrane. Characterisation results show that the surfaces of the PC membrane exposed
to HAuCl4 and aniline have significantly higher concentrations of Au nanoparticles and polyaniline, respectively. 相似文献
85.
Mining associations with the collective strength approach 总被引:1,自引:0,他引:1
The large itemset model has been proposed in the literature for finding associations in a large database of sales transactions. A different method for evaluating and finding itemsets referred to as strongly collective itemsets is proposed. We propose a criterion stressing the importance of the actual correlation of the items with one another rather than their absolute level of presence. Previous techniques for finding correlated itemsets are not necessarily applicable to very large databases. We provide an algorithm which provides very good computational efficiency, while maintaining statistical robustness. The fact that this algorithm relies on relative measures rather than absolute measures such as support also implies that the method can be applied to find association rules in data sets in which items may appear in a sizeable percentage of the transactions (dense data sets), data sets in which the items have varying density, or even negative association rules 相似文献
86.
Theoretical and experimental study of the second-order polarizabilities of Schiff''s bases for nonlinear optical applications 总被引:1,自引:0,他引:1
K. Bhat J. Choi S.D. McCall M.D. Aggarwal B.H. Cardelino C.E. Moore Benjamin G. Penn D.O. Frazier M. Sanghadasa T.A. Barr N.B. Laxmeshwar 《Computational Materials Science》1997,8(4):309-316
A series of twenty-four Schiff's bases was synthesized and nonresonant static molecular second order polarizabilities (β) of these compounds were theoretically calculated and compared with experimental values. The computational method employed obtained: (a) values of polarization versus static electric fields using a semiempirical Hamiltonian; (b) all tensor elements of β by performing polynomial fits of the former data, within the finite-field approach. The experimental values were obtained using a modified electric field induced second harmonic generation (EFISH) experiment with 1,4-dioxane as the solvent. The measured quantities were the projection of β on μ (the permanent dipole moment), relative to MNA (2-methyl-4-nitroaniline). The correlation between the predicted static molecular quantities and their corresponding experimental values was 0.95 (based on a simple least-squares regression forced through the origin). A factor of 8.7 ± 0.3 was determined to be the adjustment parameter for Schiff's bases to account for the solvent and dispersion effects at the fundamental wavelength of 1064 nm. 相似文献
87.
88.
Using the methods of recombination and gene disruption, the effects of degUS gene in Bacillus subtilis Ki-2-132 were studied. The results showed that the gene could affect all protease-producing, competence formation, cell mobility and repression effects of glucose on protease-production. This implies that it is a pleitropic gene in Bacillus subtilis Ki-2-132. The disruption of the gene caused morphological changes and repressed the expression of aprE in vectors. 相似文献
89.
Al2O3-ZrO2 composites were prepared in two compositional ranges, 15 wt% ZrO2 and 29wt% ZrO2 with or without yttria or magnesia stabilizers. While 1.5 wt% Y2O3 produced tetragonal ZrO2 and fine grain microstructure, the 4.5 wt% Y2O3 developed cubic and tetragonal ZrO2 with similar microstructure. Al2O3 with 29.5wt% ZrO2-1.5wt% Y2O3 composition had the highest strength (3,300 kg/cm2). The bending strength remained more or less the same after the first thermal shock, and then it decreased gradually, but retained some strength after 20 cycles of quench. The load vs displacement curve became nonlinear after thermal shock possibly because of formation of microcracks which could be seen by microstructural studies. 相似文献
90.
ABSTRACTIn the present work, the self-organized pattern formation with simultaneous surface smoothing of Polyethylene terephthalate (PET) by 40 keV Ar+ ions irradiation has been discussed. The effect of most important experimental parameter i.e. ion beam incidence that control these processes has been discussed by varying off normal incidences from 300 to 500. The changes in surface topography have been studied using Atomic Force Microscopy (AFM). It has been investigated from AFM analysis that oblique ion beam induced sputtering significantly reduced the surface roughness with simultaneous formation of some hillock and hole like structures. 相似文献