首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7821篇
  免费   635篇
  国内免费   64篇
电工技术   135篇
综合类   90篇
化学工业   1774篇
金属工艺   311篇
机械仪表   521篇
建筑科学   162篇
矿业工程   10篇
能源动力   391篇
轻工业   769篇
水利工程   22篇
石油天然气   46篇
武器工业   2篇
无线电   1312篇
一般工业技术   1715篇
冶金工业   353篇
原子能技术   117篇
自动化技术   790篇
  2024年   14篇
  2023年   128篇
  2022年   170篇
  2021年   317篇
  2020年   241篇
  2019年   243篇
  2018年   312篇
  2017年   288篇
  2016年   342篇
  2015年   301篇
  2014年   384篇
  2013年   550篇
  2012年   517篇
  2011年   642篇
  2010年   498篇
  2009年   519篇
  2008年   417篇
  2007年   296篇
  2006年   320篇
  2005年   231篇
  2004年   237篇
  2003年   231篇
  2002年   222篇
  2001年   171篇
  2000年   140篇
  1999年   114篇
  1998年   150篇
  1997年   108篇
  1996年   92篇
  1995年   77篇
  1994年   35篇
  1993年   33篇
  1992年   35篇
  1991年   24篇
  1990年   24篇
  1989年   18篇
  1988年   11篇
  1987年   10篇
  1986年   8篇
  1985年   10篇
  1984年   4篇
  1983年   3篇
  1981年   6篇
  1980年   6篇
  1979年   3篇
  1977年   4篇
  1976年   5篇
  1975年   2篇
  1974年   2篇
  1967年   1篇
排序方式: 共有8520条查询结果,搜索用时 15 毫秒
41.
We develop a miniaturized batch-type screw mixer (BSM) for uniform mixing of polymer resin and nanoparticles, based on the stretching of material elements. This stretching is induced by the combination of recirculating cross-sectional flows in deep channels of the screw and high shear stress developed at flight regions. The BSM is used to produce a polymer nano-composite composed of multi-walled carbon nanotubes and polydimethylsiloxane resin. The mixing performance of the BSM is characterized quantitatively by estimating two different types of mixing efficiencies (i.e., dispersive mixing and distributive mixing) via transmitted light microscope images. The developed BSM highly improves the mixing performance rather than that of a conventional ultrasonic mixing device.  相似文献   
42.
The High-Performance Computing (HPC) is an infrastructure to support various research fields. The research using HPC requires big storage for large-scale of raw data and the huge computing resources to analyze. The consolidated operations of the computing center for supporting various researches using HPC are a very effective organization. The consolidated operations are able to increase the utilization. The computing center has to be re-organized continuously in order to support the various fields of research effectively and flexibly. Re-organization to reuse the limited resources enforces the update of the information for verification of the computing resources after the re-allocation of computing resources and the re-distribution of trusted connection between computing resources. Consequently, to maintain effective research support we need automated resource re-organization environment. In this paper, we build an automated update of the trusted connection for re-organized computing resource using puppet which is automated system management platform. Finally, we provide a unified verification point and efficient environment for the re-allocation and re-organization of the integrated computing center.  相似文献   
43.
The effects of estrogen-induced hyperlipidemia on plasma lipid peroxidation, fatty acid composition and osmotic fragility of erythrocytes in chickens were studied. Young male chickens implanted with estrogen for three wk developed a marked hyperlipidemia. Plasma levels of triglyceride, cholesterol and phospholipid were elevated 68-, four- and 24-fold, respectively, over controls. There was also a two-fold increase in plasma lipid peroxidation measured by the thiobarbituric acid test. Vitamin E supplement (1,000 IU/kg diet) reduced the plasma lipid peroxidation to the control level, but had no effect on the plasma lipid content. Estrogen-induced hyperlipidemia resulted in changes in the fatty acid composition of membrane lipids of erythrocytes. The major changes were an increase in oleic acid from 10.0% to 14.2% and a decrease in linoleic acid from 31.3% to 26.0%. The erytrocytes with an altered membrane fatty acid composition were found to have an increased osmotic fragility. It was apparent that there was a direct correlation between the oleic acid content and the osmotic fragility of erythrocytes.  相似文献   
44.
To provide context-based personalized services utilizing smart appliances in a smart home environment, we propose a framework for PersonAlized Service disCovery Using FuZZY-based CBR and Context Ontology (PASCUZZY). Basically, the PASCUZZY framework is implemented on case-based context ontology. To generate and manage the case instances on the case-based context ontology, we adopt the fuzzy set theory to transpose numerical-type context data sensed from the surrounding environment. The context is transposed to linguistic-type context instances on the context ontology. In addition, to formalize and manage the context and services as multi-attributed data, the context ontology was developed reflecting the structure of cases borrowed from case-based reasoning. Furthermore, we propose adaptation methods to adjust the generic fuzzy membership functions depending on the inhabitants’ context. It is performed by modifying the values of the membership number and/or modifying the numbers of the linguistic terms that are based on the inhabitants’ context to affect the membership numbers. The adapted membership functions return the personalized degree of memberships depending on the specialized context of a specific fuzzy variable. Inevitably, the number of cases on the case-based context ontology will be increased from time to time. We apply Ward’s method not only to reduce the search effort via a hierarchical clustering on the case-based context ontology but also to find the most similar service as a solution to the new context. To verify the superiority of the PASCUZZY framework, we perform two kinds of evaluations. First, we evaluate the effectiveness of the adaptation of the fuzzy membership functions. Second, we verify the effectiveness of the application of a clustering method to the case instances of the case-based context ontology to identify the most similar service. Results of the experiment verified the effectiveness and superiority of the PASCUZZY framework.  相似文献   
45.
Binary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH-62) and 71 (EVOH-71) mole percent vinyl alcohols, with nylons (nylon-6, nylon-6/12, and nylon-12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH-62/nylon-6 and EVOH-71/nylon-6 blends showed homogeneous phase morphologies in the nylon-6-rich region, and fine phase separations (c.a. 2 × 10?7 m) in the EVOH-rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH-71/nylon-6/12 and EVOH-71 /nylon-12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed.  相似文献   
46.
This paper proposes a method of exploring the local shape of an unknown object using the force and torque information obtained from active touch. In the first, we present a method to estimate an unknown curvature, using rolling and sliding motion with a force/torque sensor attached to the fingertip of the hand. Then, the normal curvature equation from 2D curvatures is obtained. Finally we present a reconstruction algorithm of local geometry by using a normal curvature equation, which is composed of principal curvatures and principal directions. The method is tested by using a hand-arm system consisting of an industrial robot arm and an anthropomorphic robot hand with 6-axis force/torque sensor. The feasibility of the proposed method is experimentally validated for objects with simple geometries such as cylinder, spheres etc.  相似文献   
47.
Verifiably encrypted signature schemes can convince a verifier that a given ciphertext is an encryption of an ordinary signature on a given message and the ordinary signature can be recovered by the third party, called adjudicator. In 2010, Rückert et al. proposed a general construction for the verifiably encrypted signatures, and then, they also showed that there exist the lattice-based verifiably encrypted signature schemes. Their constructions are very insightful, but their schemes need an extra adjudication setup phase and Merkle trees, so they have large parameters and keys, that is, they are inefficient. Also, their schemes provide only the limited signature capacity because the signing keys should be reissued after generating \(k\) th verifiably encrypted signatures. To overcome the weaknesses of Rückert et al.’s scheme, we construct a verifiably encrypted signature scheme based on the hard lattice problems. Our scheme provides the full functionality, i.e., the signatures can be generated without any limitations and does not need any extra adjudication setup phases. Moreover, the size of the secret keys in our scheme is constant. Our scheme provides unforgeability, opacity, extractability, and abuse-freeness in the random oracle model.  相似文献   
48.
介绍板壳式换热器的主要特点和应用。当壳体与板束温差较大时,笔者通过对产品开发的生产实践,提出解决板壳式换热器要否设置膨胀节的类似判定方法。  相似文献   
49.
The gapwise density distributions of the injection molded specimens of two engineering thermoplastics, i.e., poly(phenylene ether) and poly(ether imide), were characterized employing the density gradient column technique. The samples were molded using a 40t Van Dorn injection molding machine. The effects of the thermal history on the density distribution of unconstrained quenched specimens were also investigated. In addition, various material properties, such as pressure-volume-temperature, isothermal contraction, and pressure induced densification behavior were characterized, for the two resins employed in this study. The moldings of the two resins exhibited different trends in their density distributions. These findings were explained in terms of the competing effects of cooling rate and the pressure history experienced by the engineering plastic resins during the molding cycle. The data collected were also used as input to mathematical modeling of density distributions in injection molded articles, which is reported in Part II of this article.  相似文献   
50.
We study quantum teleportation between two different types of optical qubits using hybrid entanglement as a quantum channel under decoherence effects. One type of qubit employs the vacuum and single-photon states for the basis, called a single-rail single-photon qubit, and the other utilizes coherent states of opposite phases. We find that teleportation from a single-rail single-photon qubit to a coherent-state qubit is better than the opposite direction in terms of fidelity and success probability. We compare our results with those using a different type of hybrid entanglement between a polarized single-photon qubit and a coherent state.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号