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21.
Vapour-phase reactions of, in situ, prepared formaldehyde with methyl propionate were studied using X, Y and ZSM-5 zeolite catalysts. Base properties of these zeolites were enhanced by KOH or NaN3 treatment. The niobium and molybdenum ZSM-5 zeolite supported oxides were also tested for their catalytic activity. The results are discussed in terms of an ability of zeolite catalysts to synthesize methyl methacrylate. 相似文献
22.
Radosław Michalski Tomasz Kajdanowicz Piotr Bródka Przemysław Kazienko 《New Generation Computing》2014,32(3-4):213-235
The problem of finding optimal set of users for influencing others in the social network has been widely studied. Because it is NP-hard, some heuristics were proposed to find sub-optimal solutions. Still, one of the commonly used assumption is the one that seeds are chosen on the static network, not the dynamic one. This static approach is in fact far from the real-world networks, where new nodes may appear and old ones dynamically disappear in course of time. The main purpose of this paper is to analyse how the results of one of the typical models for spread of influence - linear threshold - differ depending on the strategy of building the social network used later for choosing seeds. To show the impact of network creation strategy on the final number of influenced nodes - outcome of spread of influence, the results for three approaches were studied: one static and two temporal with different granularities, i.e. various number of time windows. Social networks for each time window encapsulated dynamic changes in the network structure. Calculation of various node structural measures like degree or betweenness respected these changes by means of forgetting mechanism - more recent data had greater influence on node measure values. These measures were, in turn, used for node ranking and their selection for seeding. All concepts were applied to experimental verification on five real datasets. The results revealed that temporal approach is always better than static and the higher granularity in the temporal social network while seeding, the more finally influenced nodes. Additionally, outdegree measure with exponential forgetting typically outperformed other time-dependent structural measures, if used for seed candidate ranking. 相似文献
23.
Piotr Hońko 《国际智能系统杂志》2014,29(5):407-438
One of the popular methods to develop an algorithm for mining data stored in a relational structure is to upgrade an existing attribute‐value algorithm to a relational case. Current approaches to this problem have some shortcomings such as (1) a dependence on the upgrading process of the algorithm to be extended, (2) complicated redefinitions of crucial notions (e.g., pattern generality, pattern refinement), and (3) a tolerant limitation of the search space for pattern discovery. In this paper, we propose and evaluate a general methodology for upgrading a data mining framework to a relational case. This methodology is defined in a granular computing environment. Thanks to our relational extension of a granular computing based data mining framework, the three above problems can be overcome. 相似文献
24.
Lucjan Chmielarz Piotr Kutrowski Alicja Rafalska-asocha Roman Dziembaj 《Applied catalysis. B, Environmental》2005,58(3-4):235-244
The selective catalytic oxidation of ammonia to nitrogen (NH3-SCO) has been studied over hydrotalcite derived mixed metal oxides containing Cu, Co, Fe or Ni. XRD, BET, NH3-TPD and TPR techniques were used for catalysts characterization. Results of NH3-SCO were compared with those of selective catalytic reduction of NO with NH3 (NO-SCR). Reaction mechanism was studied by temperature-programmed surface reaction (TPSR) and activity tests with a various contact time. Catalytic performance of the studied samples depends on both kind and loading of transition metals in the mixed metal oxide system. The Cu-containing samples have been found to be the most active catalysts of the NH3-SCO process. Transition metal loading strongly influences distribution of ammonia oxidation products. The highest selectivity to N2 was measured for the catalysts with the lowest transition metal content. 相似文献
25.
Effect of Mode of Drying on Microstructure of Potato 总被引:2,自引:0,他引:2
Potato v. Irga was subjected to blanching, and thereafter was dried by convection, puff-drying, and freeze-drying. Microstructure of raw, blanched, and dried tissue was analyzed under the light microscope using computer image analysis. It was found that the tissue of the investigated variety is built up from cells much smaller than those described in literature for other cultivars. Blanching caused starch gelatinization and increase of cross-sectional area of cells. There was no evidence of broken cell walls. Convective drying resulted in cell shrinkage and some breaking of cell walls. It was estimated that some 12% of cells lost integrity during drying. Limited disintegration of the tissue caused by convective drying is attributed to small size of cells, large contact area, and high cohesive forces between cells. Puff-drying damaged the tissue much more than the convective drying. The most devastating to tissue microstructure was freeze-drying, probably freezing per se. 相似文献
26.
Threats on the stability of a financial system may severely affect the functioning of the entire economy, and thus considerable emphasis is placed on the analyzing the cause and effect of such threats. The financial crisis in the current and past decade has shown that one important cause of instability in global markets is the so-called financial contagion, namely the spreadings of instabilities or failures of individual components of the network to other, perhaps healthier, components. This leads to a natural question of whether the regulatory authorities could have predicted and perhaps mitigated the current economic crisis by effective computations of some stability measure of the banking networks. Motivated by such observations, we consider the problem of defining and evaluating stabilities of both homogeneous and heterogeneous banking networks against propagation of synchronous idiosyncratic shocks given to a subset of banks. We formalize the homogeneous banking network model of Nier et al. (J. Econ. Dyn. Control 31:2033–2060, 2007) and its corresponding heterogeneous version, formalize the synchronous shock propagation procedures outlined in (Nier et al. J. Econ. Dyn. Control 31:2033–2060, 2007; M. Eboli Mimeo, 2004), define two appropriate stability measures and investigate the computational complexities of evaluating these measures for various network topologies and parameters of interest. Our results and proofs also shed some light on the properties of topologies and parameters of the network that may lead to higher or lower stabilities. 相似文献
27.
Ewa Kicko‐Walczak 《应用聚合物科学杂志》2003,88(13):2851-2857
In this article, the kinetics of thermal decomposition of unsaturated maleic–phthalic polyester resins, flame‐retarded with zinc hydroxystannate, was studied by thermogravimetric analysis at different heating rates. At the first stage, it was found, on the basis of isoconversional analysis by the methods of Friedman and of Ozawa–Flynn–Wall, that the value of the (apparent) activation energy (E) characteristically changes in three steps during the degradation. Further kinetic studies using nonlinear regression methods revealed the best fits for both pristine and stabilized resins. It was observed that the course of E versus the degree of conversion (α) during degradation of zinc hydroxystannate‐containing resins (α > 0.8) was characterized by higher values of E—this phenomenon can be explained in terms of the flame‐retardation action of zinc hydroxystannate, which is believed to operate primarily in the condensed phase. At the next stage, kinetic analysis by the nonregression method was performed to find the kinetic model [f(α) function] of the decomposition process; hence, for pristine resin, the best fit was found for the Avrami–Yerofeeyev model (nuclei growth), and for stabilized samples, the nth‐order function with catalysis proved to be the best approximation. The obtained kinetic parameters in the form of E, the preexponential factor A, and the model function f(α) allow a prediction of the polyester resin's thermal behavior in an extrapolated range of degree of conversion, time, and temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2851–2857, 2003 相似文献
28.
A Monte Carlo method was used for a computer simulation of radiation-induced solid state polymerization. The propagation of polymer chains was simulated by means of self-avoiding random walks on a tetrahedral lattice. The initiation and termination of the chains were modelled by pseudorandom processes. The influence of conditions of the in-source process on the post-polymerization kinetics and on the degree of polymerization of the polymers was studied. 相似文献
29.
Lucjan Janowski Piotr Kozłowski Remigiusz Baran Piotr Romaniak Andrzej Glowacz Tomasz Rusc 《Multimedia Tools and Applications》2014,68(1):23-40
Video transmission and analysis is often utilized in applications outside of the entertainment sector, and generally speaking this class of video is used to perform specific tasks. Examples of these applications include security and public safety. The Quality of Experience (QoE) concept for video content used for entertainment differs significantly from the QoE of surveillance video used for recognition tasks. This is because, in the latter case, the subjective satisfaction of the user depends on achieving a given functionality. Recognizing the growing importance of video in delivering a range of public safety services, we focused on developing critical quality thresholds in license plate recognition tasks based on videos streamed in constrained networking conditions. Since the number of surveillance cameras is still growing it is obvious that automatic systems will be used to do the tasks. Therefore, the presented research includes also analysis of automatic recognition algorithms. 相似文献
30.
Methanol adsorption and electro-oxidation on Pt-Rh alloys have been studied in aqueous 0.5 M H2SO4 for a broad range of alloy surface composition including the pure Pt and Rh metals. Adsorption results have been compared with equivalent data obtained for CO and CO2 adsorption on these alloys. Current densities of continuous methanol oxidation on Pt, Rh and a Pt-Rh alloy with optimum surface molar fraction of Rh have been measured.Although on the pure Pt and Rh metals the methanol adsorption products exhibit similar energetic stability, as judged from the peak potential of electro-desorption, on the Pt-Rh alloys, there is a lowering of the stability. Similar behavior is observed for the CO and CO2 adsorption products, however, the lowering for methanol is much less than for CO and CO2. In the case of methanol, the maximum lowering is obtained for a surface molar fraction of Rh equal to ca. 0.65 and it is the same alloy surface composition that results in maximum lowering of the stability of the CO2 adsorption products, but not of the CO adsorption products (optimal fraction of Rh equal ca. 0.10). Structural similarity of the methanol and the CO2 adsorption products finds support in similar values of the electrons-per-site parameter obtained.Pt-Rh alloys show insufficient electrode potential improvement over Pt in continuous methanol electro-oxidation due to the susceptibility of Rh to strong poisoning by the methanol adsorption products, which switches off the bi-functional mechanism of methanol electro-oxidation on this alloy. The presence of Rh in the alloy with Pt additionally strongly lowers the methanol electro-oxidation turnover rate of the Pt component. 相似文献