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   615篇
  免费   17篇
  国内免费   3篇
电工技术   5篇
综合类   5篇
化学工业   192篇
金属工艺   8篇
机械仪表   7篇
建筑科学   7篇
能源动力   24篇
轻工业   43篇
水利工程   2篇
石油天然气   2篇
无线电   62篇
一般工业技术   137篇
冶金工业   56篇
原子能技术   6篇
自动化技术   79篇
  2024年   2篇
  2023年   16篇
  2022年   36篇
  2021年   28篇
  2020年   35篇
  2019年   27篇
  2018年   39篇
  2017年   25篇
  2016年   18篇
  2015年   7篇
  2014年   20篇
  2013年   36篇
  2012年   27篇
  2011年   37篇
  2010年   20篇
  2009年   30篇
  2008年   23篇
  2007年   18篇
  2006年   7篇
  2005年   8篇
  2004年   8篇
  2003年   13篇
  2002年   11篇
  2001年   10篇
  2000年   7篇
  1999年   7篇
  1998年   17篇
  1997年   13篇
  1996年   13篇
  1995年   9篇
  1994年   6篇
  1993年   10篇
  1992年   4篇
  1991年   4篇
  1990年   1篇
  1989年   2篇
  1988年   4篇
  1987年   4篇
  1986年   4篇
  1985年   7篇
  1984年   6篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1977年   4篇
  1976年   3篇
  1971年   1篇
排序方式: 共有635条查询结果,搜索用时 15 毫秒
61.
62.
A 35 year-old man developed a syndrome with muscle cramp, myokimia, generalized, fasciculations, excessive sweating, sleep disorders and severe impairment. It was a syndrome of continuous muscle fiber activity--or Isaacs syndrome--with central disorders (this may be called "Maladie de Morvan"). Previous reports have suggested that Isaac's syndrome might be an autoimmune disorder. Moreover, high doses intravenous immunoglobulins were given resulting in a substantial improvement six months after the onset of this treatment.  相似文献   
63.
The Journal of Supercomputing - Wireless sensor networks (WSN) are expected to cover the major portion of the earth’s surface in the coming years. In the era of IoT, the WSN is the major data...  相似文献   
64.
In this paper we propose a methodology to mine concepts from documents and use these concepts to generate an objective summary of all relevant documents. We use the conceptual graph (CG) formalism as proposed by Sowa to represent the concepts and their relationships in the documents. In the present work we have modified and extended the definition of the concept given by Sowa. The modified and extended definition is discussed in detail in section 2 of this paper. A CG of a set of relevant documents can be considered as a semantic network. The semantic network is generated by automatically extracting CG for each document and merging them into one. We discuss (i) generation of semantic network using CGs and (ii) generation of multi-document summary. Here we use restricted Boltzmann machines, a deep learning technique, for automatically extracting CGs. We have tested our methodology using MultiLing 2015 corpus. We have obtained encouraging results, which are comparable to those from the state of the art systems.  相似文献   
65.
A series of polymer supported cobalt complexes have been synthesized by the reaction of Co(II)‐SALEN (salicylaldehyde ethylenediimine) and other variations thereof with the chelating resin containing vinyl pyridine. The polymer supported complexes have been characterized by electronic and infrared spectra. The presence of polymer supports has a marked influence on the UV–visible bands observed in the electronic spectra of cobalt complexes. These polymer supported complexes are also investigated by cyclic voltammetry. The electronic spectral data and cyclic voltammetric data for free complexes and polymer supported complexes are compared. The discernible differences in the spectral and electrochemical data suggest the presence of pentacoordinate cobalt in the polymer matrix. © 2000 Society of Chemical Industry  相似文献   
66.
The polymer systems of vinyl latex, epoxy latex/resin, and phenol formaldehyde were used to modify sand-cement mortar at room temperature. The compressive strength increased with an increase of the latex/resin concentration, with the addition of CaCl2 or CaCO3, and with the addition of superplasticizer. Tensile and flexural strengths also increased with polymer incorporation. The porosity of the modified mortar decreased with the addition of resin. The percentage of water absorption and acid solubility were found to decrease for the latex/resin modified samples. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1251–1257, 1997  相似文献   
67.
Poly(vinyl alcohol) cross-linked with para-formaldehyde (PVA–F) and natural polysaccharide–chitosan in bead form and salicylic acid–resorcinol–formaldehyde polymeric resin (SRF) in powder form were used for immobilization of β-galactosidase through covalent linkages. Various activation processes and conditions were optimized. Immobilized enzyme showed very good storage stability at room temperature. Durability of the enzyme was also improved on immobilization. On repeated use of enzyme immobilized on chitosan beads, no loss was observed in enzyme activity even after 10 batches. Michaelis constant Km and maximum reaction velocity Vm were calculated for free and immobilized enzyme systems. Effect of pH and temperature on enzyme activity was estimated and energy of activation (Ea) and inactivation constant (Ki) for free and immobilized enzyme were calculated. © 1995 John Wiley & Sons, Inc.  相似文献   
68.
NCO‐terminated polyurethane membranes were prepared using diisocyanate, diol, and trimethylolpropane (TMP) using an NCO/OH ratio of 1.6 : 1. Prepolymer was chain‐extended using cellulose acetate butyrate (CAB) in the ratios of 2 : 1, 4 : 1, and 3 : 1 of NCO/OH. Polyurethane (PU) membranes were characterized by differential scanning calorimeter (DSC) and thermogravimetry (TGA) to investigate their thermal properties. Equilibrium sorption studies were carried out at 30°C in water and ethyl acetate media as well as in their binary mixtures. The influence of CAB on pervaporation (PV) separation of an ethyl acetate/water (92/8, w/w, i.e., azeotropic composition) mixture was investigated. Membranes in this study showed a selectivity of 42.42 with a flux value of 0.187 kg/m/h for 3 : 1% NCO/OH containing PU membrane. In order to gain a more detailed picture of the molecular transport phenomenon, we performed the sorption gravimetric experiments at 30°, 35°, 40°, and 50°C to compute diffusion, swelling, sorption, and permeability coefficients of PU membranes in the azeotropic mixture of ethyl acetate and water. Activation parameters for diffusion and permeation were computed from the Arrhenius equation to understand the polymer/solvent interactions. Sorption trends and diffusion anomalies were established through an empirical equation after estimating the diffusion parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3405–3414, 2007  相似文献   
69.
Chemical modification of pinewood was carried out by impregnating the wood with styrene as the impregnating monomer and in combination with a crosslinking monomer glycidyl methacrylate (GMA). Polymerization was carried out by catalyst heat treatment. Dimensional stability in terms of antiswell efficiency was determined and improved on treatment with polymer. Water uptake percentage was also improved for styrene‐GMA treated wood samples over styrene treated or untreated wood samples. Mechanical properties such as bending strength measured in terms of modulus of elasticity and modulus of rupture of polymer‐treated samples showed an improvement over untreated ones. Treatment also resulted an improvement in compressive strengths. Thermal properties of the wood samples were evaluated by thermogravimetric analyzer and differential scanning calorimeter. Biodegradability of the treated and untreated wood samples was determined and improvement was obtained on treatment. As a whole, styrene‐GMA treated wood samples showed more improvement over untreated or styrene‐treated samples. POLYM. COMPOS., 28:1–5, 2007. © 2007 Society of Plastics Engineers  相似文献   
70.
The structural changes produced by aqueous swelling and stretching in cotton is found to be irreversible. This article present the X-ray angle data of six varieties of cotton that belong to Gossypium hirsutum. A marked decrease in X-ray angles was found in all treated samples, thereby indicating better orientation. Improvement in the orientation is associated with ncrease in the stretch. The improvement is high in all tension-dried cottons, showing the impact of the tension drying. Similar improved orientation is found in all varieties, indicating the varietal response of G. hirsutum. © 1996 John Wiley & Sons, Inc.  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