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131.
132.
CSVD: clustering and singular value decomposition for approximate similarity search in high-dimensional spaces 总被引:1,自引:0,他引:1
Castelli V. Thomasian A. Chung-Sheng Li 《Knowledge and Data Engineering, IEEE Transactions on》2003,15(3):671-685
Nearest-neighbor search of high-dimensionality spaces is critical for many applications, such as content-based retrieval from multimedia databases, similarity search of patterns in data mining, and nearest-neighbor classification. Unfortunately, even with the aid of the commonly used indexing schemes, the performance of nearest-neighbor (NN) queries deteriorates rapidly with the number of dimensions. We propose a method, called Clustering with Singular Value Decomposition (CSVD), which supports efficient approximate processing of NN queries, while maintaining good precision-recall characteristics. CSVD groups homogeneous points into clusters and separately reduces the dimensionality of each cluster using SVD. Cluster selection for NN queries relies on a branch-and-bound algorithm and within-cluster searches can be performed with traditional or in-memory indexing methods. Experiments with texture vectors extracted from satellite images show that CSVD achieves significantly higher dimensionality reduction than plain SVD for the same normalized mean squared error (NMSE), which translates into a higher efficiency in processing approximate NN queries. 相似文献
133.
Clara Silvestre Sossio Cimmino Maria Raimo Donatella Duraccio Bernardo del Amo Fernandez Pilar Lafuente Virginia Leal Sanz 《大分子材料与工程》2006,291(12):1477-1485
Summary: In this work the analysis of the structure orientation, morphology, relaxation time and optical properties of blown films of mLLDPE, LDPE and their blends were performed by using WAXD, SALS, AFM, DSC and rheological and haze tests. For mLLDPE film, the crystals do not present “a”‐axis orientation along the machine direction; a distinct spherulite like superstructure is seen. The film surface is very rough. The values of bulk and surface haze are higher than LDPE and blends, whereas the relaxation time is lower. For LDPE film the (110) planes are parallel and at same time twisted with respect to the layer of the film with the “a”‐axis well oriented along the machine direction. No spherulite superstructure is observed and the surface of the film is more regular. High values of relaxation time are observed. The surface haze is the predominant contribution to the total haze. For the blend films no clear and distinct spherulite structures are observed. The orientation degree increases with composition never approaching that of LDPE. The surface is very more regular and smooth than that of the pure polymers. The haze values are below the values of pure materials. It was underlined that bulk and surface morphology and orientation degree of the crystalline planes along the machine direction dictate the optical properties of the films. Moreover both orientation and morphology are defined by the PE molecular and melt rheology characteristics, processing conditions and blend composition.
134.
Aida Benhamida Mustapha Kaci Sossio Cimmino Clara Silvestre Donatella Duraccio 《大分子材料与工程》2009,294(2):122-129
The chemical modification by melt‐mixing of an EBAGMA terpolymer with LDPE and PET was investigated with the aim to use these EBAGMA/LDPE and EBAGMA/PET blends (in equal weight quantities) as compatibilizer master batches to improve the compatibility of the LDPE/PET system. It is shown that when the EBAGMA terpolymer is melt blended with LDPE, almost 40% of the initial amount of EBAGMA is linked to the LDPE backbone. In contrast, in the case of EBAGMA/PET, FT‐IR spectra indicate the total reactivity between the two components through the reaction of the epoxy group of EBAGMA with the PET terminal groups. SEM analysis shows that both master batches present two well‐interconnected phases.
135.
L Rivoltini M Radrizzani P Accornero P Squarcina C Chiodoni A Mazzocchi C Castelli P Tarsini V Viggiano F Belli MP Colombo G Parmiani 《Canadian Metallurgical Quarterly》1998,161(3):1220-1230
Tumor cells have been shown recently to escape immune recognition by developing resistance to Fas-mediated apoptosis and acquiring expression of Fas ligand (FasL) molecule that they may use for eliminating activated Fas+ lymphocytes. In this study, we report that tumor-specific T lymphocytes isolated from tumor lesions by repeated in vitro TCR stimulation with relevant Ags (mostly represented by normal self proteins, such as MART-1/Melan A and gp100) can develop strategies for overcoming these escape mechanisms. Melanoma cells (and normal melanocytes) express heterogeneous levels of Fas molecule, but they result homogeneously resistant to Fas-induced apoptosis. However, CD4+ and CD8+ CTL clones kill melanoma cells through Fas/FasL-independent, granule-dependent lytic pathway. In these lymphocytes, Ag/MHC complex interaction with TCR does not lead to functional involvement of FasL, triggered, on the contrary, by T cell activation with nonspecific stimuli such as PMA/ionomycin. Additionally, melanoma cells express significant levels of FasL (detectable on the cell surface only after treatment with metalloprotease inhibitors), although to a lesser extent than professional immune cells such as Thl clones. Nevertheless, antimelanoma CTL clones resist apoptosis mediated by FasL either in soluble form or expressed by Thl lymphocytes or FasL+ melanoma cells. These results demonstrate that CD4+ and CD8+ antimelanoma T cell clones can be protected against Fas-dependent apoptosis, and thus be useful reagents of immunotherapeutic strategies aimed to potentiate tumor-specific T cell responses. 相似文献
136.
137.
New iodoacetamide derivatives, containing a dodecyl or a squalenyl moiety, were synthesized. The effect of these new thiol-reacting
molecules was studied on two mutants of Alicyclobacillus acidocaldarius squalene-hopene cyclase constructed especially for this purpose. In the quintuple mutant, all five cysteine residues of the
enzyme are substituted with serine; in the sextuple mutant, this quintuple substitution is accompanied by the substitution
of aspartate D376, located at the enzyme’s active site, with a cysteine. N-Dodecyliodoacetamide had little activity toward either mutant, whereas N-squalenyliodoacetamide showed a stronger effect on the sextuple than on the quintuple mutant, as expected. 相似文献
138.
E. J. Parks F. E. Brinckman C. E. Mullin D. M. Andersen V. J. Castelli 《应用聚合物科学杂志》1981,26(9):2967-2974
Copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) comprise an important class of biocidal slow-release organometallic polymers (OMPs). Little is known of the kinetics and mechanism of copolymerization. TBTM and MMA were copolymerized in the presence of a free radical initiator (benzoyl peroxide) at 80.1°C. Aliquots, taken at preselected intervals from 0 to 1440 min, were fractionated by size exclusion chromatography (SEC) coupled with ultraviolet (UV) and tin-specific graphite furnace atomic absorption (GFAA) detectors. A UV absorbance observed at 254 nm was associated with low-molecular-weight species, decreasing in concentration continuously with time of reaction. Tin-specific GFAA indicated a decrease in low-molecular-weight species (ca. 350 daltons) with concurrent increases in high-molecular-weight species (ca. 40,000 daltons). The fraction of high molecular-weight increased as a linear function of the logarithm of the time of reaction. SEC–UV–GFAA thus provides a tool of major importance for characterizing the time dependence and continuity of the process by which monomers of TBTM are converted to a useful bioactive slow-release coating material. 相似文献
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140.