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   3719篇
  免费   223篇
  国内免费   2篇
电工技术   112篇
综合类   4篇
化学工业   873篇
金属工艺   73篇
机械仪表   116篇
建筑科学   123篇
矿业工程   8篇
能源动力   137篇
轻工业   527篇
水利工程   17篇
石油天然气   13篇
无线电   293篇
一般工业技术   909篇
冶金工业   64篇
原子能技术   11篇
自动化技术   664篇
  2023年   28篇
  2022年   43篇
  2021年   102篇
  2020年   89篇
  2019年   99篇
  2018年   143篇
  2017年   127篇
  2016年   168篇
  2015年   119篇
  2014年   185篇
  2013年   379篇
  2012年   263篇
  2011年   278篇
  2010年   217篇
  2009年   176篇
  2008年   180篇
  2007年   156篇
  2006年   124篇
  2005年   85篇
  2004年   59篇
  2003年   68篇
  2002年   52篇
  2001年   39篇
  2000年   40篇
  1999年   41篇
  1998年   38篇
  1997年   18篇
  1996年   37篇
  1995年   25篇
  1994年   33篇
  1993年   25篇
  1992年   25篇
  1991年   20篇
  1990年   21篇
  1989年   20篇
  1988年   15篇
  1985年   37篇
  1984年   35篇
  1983年   28篇
  1982年   25篇
  1981年   38篇
  1980年   33篇
  1979年   26篇
  1978年   24篇
  1977年   18篇
  1976年   20篇
  1975年   13篇
  1974年   12篇
  1973年   15篇
  1972年   14篇
排序方式: 共有3944条查询结果,搜索用时 15 毫秒
91.
Far infrared reflectivity spectra of polycrystalline In1?xGaxSb were measured and numerically analyzed using the classical dispersion formula and also a fitting procedure based on the modified plasmon-phonon interaction model in the temperature range from 10 K to 300 K. Optical parameters were calculated and discussed. A local mode belonging to the GaSb rich end and two-mode behavior were observed at low temperatures.  相似文献   
92.
Production of extrudates from cereals is an often-used technological process in today’s world food industry. Extrudates from corn flour produced using the twin-screw extrusion process and enriched with whey protein concentrate represent high-quality source of proteins and fats. Whey protein concentrate (WPC) as a valuable source of proteins and minerals is one of the highest-quality components for possible extrudate enrichment. In this paper, the influence of various WPC addition and some extrusion process parameters such as feed moisture content ( QtextHtext2 textO Q_{{{text{H}}_{text{2}} {text{O}}}} ) on physicochemical properties of directly expanded corn flour extrudates manufactured in twin-screw co-rotating extruder was investigated. Whey protein concentrate was added in the following ratios 7.5%, 15% and 22.5% and water in 10.08, 12.18 and 14.28 L/h. Final composition of products is determined with measuring of protein, fat and water shares, water absorption index (WAI) and water solubility index (WSI). With added WPC and with increase of water volume flow, there was a significant rise in total protein, fat and water content in final products, as well as lowering of WSI and rising of WAI indexes. The statistical analysis of the obtained data shows that the lowest WSI and the highest WAI had samples with the largest share of WPC (22.5%) and water volume flow of 14.28 L/h. Colour is measured for each sample, and results were represented with hue angle (H), chroma (C) and lightness (L) values. Process parameters, WPC and QtextHtext2 textO Q_{{{text{H}}_{text{2}} {text{O}}}} influence the increase of saturation of C and lightness of L colour value, while H value stays unchanged. Mean value of H was 90.14 ± 1.06, which corresponds to dominance of yellow colour of samples.  相似文献   
93.
The octopus is an invertebrate sea animal, considered as an interesting model of inspiration in robotics, due to its high dexterity, variable stiffness, and very complex behaviours, if compared with its position in the evolutionary scale. This paper reports the design of an artificial muscular hydrostat for developing an octopus-like robot. The experimental study consists of the fabrication of a set of mock-ups demonstrating some of the key features and patterns of movement of the octopus arm.The experimental trials performed with the different mock-ups demonstrated the suitability of the silicone materials used and the patterns of actuators activation to replicate the typical octopus movements of elongation, shortening, bending, and reaching. They also confirm that control is simplified by the arrangement of muscles as well as by the mechanical properties of the muscular hydrostat.  相似文献   
94.
This paper reports the results of investigations on the influence of the so called thermal cycling treatment on the anneal hardening effect of the copper-based Cu–10 at.% Zn alloy. The quenched samples were subjected to cold rolling of 20, 40 and 60% in reduction, followed by annealing with and without thermocycling treatment below the recrystallization temperature. Anneal hardening effect was observed in both samples in the temperature range between 180 and 300 °C and was followed by an increase in the hardness and electrical conductivity. These investigations showed that the thermal cycling treatment some increased the intensity of anneal hardening effect.  相似文献   
95.
In the last years Home Automation systems gained new momentum, permeating many human-related environments, from homes to hospitals. The rapid evolution of such systems showed several interoperability pitfalls and a generally insufficient support for advanced user–home interaction. To tackle these emerging issues, recent research works defined the concept of Intelligent Domotic Environments (IDEs) where different automation systems, appliances and devices are integrated into a single powerful environment, capable of providing Ambient Intelligence (AmI) functionalities. IDEs represent one of the first attempts to define a framework for AmI environments based on off-the-shelf domotic systems. This paper contributes to extend IDE capabilities by supporting basic intelligence requirements through a rule-based reasoning mechanism. Starting from a formal model of IDE elements (DogOnt), rules are defined to evaluate environment properties. Property checking is done both off-line, for structural properties, i.e., properties involving the physical structure and configuration of the IDE, and on-line for properties dependent on current IDE states. Two rule languages, SWRL and JenaRules, are considered for rule formalization and their reasoning performance is evaluated by comparing two different rule engines, namely Jess and Jena. Results show that rule-based reasoning can deal with quite complex property checking, effectively addressing basic intelligence for IDEs and providing the basis for more advanced behaviors such as user adaptation and proactive interaction.  相似文献   
96.
97.
Coastal parts of Croatia are dominated by the SW‐verging Dinaric foldbelt, to the west and SW of which is the Adriatic Basin (the stable foreland). In both areas, the stratigraphic column is dominated by a thick carbonate succession ranging from Carboniferous to Miocene. Four megasequences have been identified: (i) a pre‐platform succession ranging in age from Late Carboniferous (Middle Pennsylvanian: Moscovian) to Early Jurassic (Early Toarcian; Bru?ane and Ba?ke Ostarije Formations); (ii) an Early Jurassic to Late Cretaceous platform megasequence (Mali Alan Formation); (iii) a Paleogene to Neogene post‐platform megasequence (Ra?a Formation); and (iv) a Neogene to Quaternary (Pliocene to Holocene) megasequence (Istra and Ivana Formations). A number of organic‐rich intervals with source rock potential have been identified on‐ and offshore Croatia: Middle and Upper Carboniferous, Upper Permian, Lower and Middle Triassic, Lower and Upper Jurassic, Lower and Upper Cretaceous, Eocene, and Pliocene – Pleistocene. Traps and potential plays have been identified from seismic data in the Dinaric belt and adjacent foreland. Evaporites of Permian, Triassic and Neogene (Messinian) ages form potential regional seals, and carbonates with secondary porosity form potential reservoirs. Oil and gas shows in wells in the Croatian part of the Adriatic Basin have been recorded but no oil accumulations of commercial value have yet been discovered. In the northern Adriatic offshore Croatia, Pliocene hemi‐pelagic marlstones and shales include source rocks which produce commercial volumes of biogenic gas. The gas is reservoired in unconsolidated sands of the Pleistocene Ivana Formation.  相似文献   
98.
Geographic information systems have the potential to aid planning functions in both data processing and decision making. Because the incorporation of GIS technology into local government is at an early stage, knowledge about GIS implementation and its impact on planning activities is scarce. Using a survey of local governments in four southeastern states, this paper explores how the new technology affects planning and whether it meets the expectations of the planning agencies using it. Most of the agencies surveyed report improvements in communication of information, data accessibility, and data accuracy. They report that more current data are available, and they have confidence in analyses performed with GIS technology. Political support, staffing, length of experience with GIS technology, system sharing, data-base contents, and number and type of GIS applications all exert some influence on either planning operations or decision making. While experience with GIS emerged as the most significant factor in achieving operational benefits, using GIS technology for analytical tasks positively affected improvements in decision making.  相似文献   
99.
Book reviews     
Whilst there have been numerous categorisations of high-rise buildings according to their function, architectural style, height or structural strategy, historically little work has been undertaken to classify them based on factors affecting their energy performance — their shape and form, façade, attitude to natural lighting, ventilation strategies, etc. These factors have been influenced by regulatory changes, developments in technology and materials, changes in architectural thinking and economic and commercial drivers. Developments such as the New York Zoning Law of 1916, the postwar innovations in curtain wall façades and the energy crises of the 1970s have all impacted on the way tall buildings of the time were designed and operated. These events also had a significant impact on the quantity of energy and the way in which it was consumed in tall buildings of the time. This paper examines the history of energy use in tall buildings, from their origins in North America in the late nineteenth century to the present day. In doing so, it categorises tall buildings into five chronological ‘generations’, based on their energy consumption characteristics.  相似文献   
100.
Supercritical (SC) CO2 extraction of dried Immortelle flowers was performed at different process parameters. The optimal extraction conditions related to the yield were determined by response surface methodology (yield 4.09% at 20 MPa and 52°C). The extracts were analyzed by GC-MS and tremetone derivatives dominated: bitalin A, 12-acetoxytremetone, gnaphaliol, 1-[2-(2-methyl-2,3-dihydroxypropyl)-2,3-dihydro-1-benzofuran-5-yl]ethanone, isobutyl bitalin A, and 1-[2-(acetylprop-1-en-2-yl)-3-hydroxy-2,3-dihydro-1-benzofuran-5-yl]ethanone. Striking differences were found among the essential oil and SC-CO2 extracts composition. The major oil compounds were γ-curcumene, α-pinene, β-selinene, α-selinene, and limonene. Mono- and sesquiterpene were found among minor constituents of the extracts. Neryl acetate was present in the extracts and essential oil.  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