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   12420篇
  免费   153篇
  国内免费   10篇
电工技术   90篇
综合类   4篇
化学工业   1236篇
金属工艺   162篇
机械仪表   227篇
建筑科学   282篇
矿业工程   55篇
能源动力   164篇
轻工业   695篇
水利工程   70篇
石油天然气   19篇
武器工业   1篇
无线电   748篇
一般工业技术   1341篇
冶金工业   6642篇
原子能技术   81篇
自动化技术   766篇
  2022年   48篇
  2021年   54篇
  2020年   40篇
  2019年   56篇
  2018年   78篇
  2017年   72篇
  2016年   84篇
  2015年   78篇
  2014年   99篇
  2013年   354篇
  2012年   193篇
  2011年   251篇
  2010年   252篇
  2009年   237篇
  2008年   255篇
  2007年   250篇
  2006年   214篇
  2005年   239篇
  2004年   177篇
  2003年   196篇
  2002年   189篇
  2001年   159篇
  2000年   172篇
  1999年   284篇
  1998年   2052篇
  1997年   1262篇
  1996年   854篇
  1995年   531篇
  1994年   465篇
  1993年   492篇
  1992年   142篇
  1991年   142篇
  1990年   150篇
  1989年   168篇
  1988年   160篇
  1987年   112篇
  1986年   101篇
  1985年   129篇
  1984年   116篇
  1983年   95篇
  1982年   84篇
  1981年   87篇
  1980年   117篇
  1979年   79篇
  1978年   92篇
  1977年   207篇
  1976年   395篇
  1975年   66篇
  1974年   63篇
  1973年   57篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Joint Accent Structure (JAS) is a construct that uses temporal relationships between different accents in a melodic pattern as indices of its complexity. The present study examines the role of different JASs in real time, attending to simple musical events. 39 adults with or without musical training were told to selectively attend to and synchronize finger taps with accents in 2 experiments that examined attentional tracking to musical patterns having a concordant or discordant JAS. Results indicate that tapping was more variable with discordant than with concordant JAS patterns, both with respect to produced inter-accent time periods and with respect to the phase of taps relative to accent onsets. These findings are interpreted in terms of real time attending and its control by event time structure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
1. In the present study, we evaluated the role of repeated administration on conditioning place preference (CPP) induced by fencamfamine (FCF) in male rats. 2. Repeated FCF (3.5 mg/kg) or saline once or daily for ten consecutive days enhanced sniffing duration and decreased locomotion and rearing duration. 3. At the 3.5 mg/kg dose, FCF produced a significant place-preference effect. 4. Repeated exposures to FCF intensified its reinforcing properties. 5. These results suggest that repeated FCF administration sensitizes its rewarding effects, as with other addictive substances.  相似文献   
103.
104.
105.
106.
Analytical ultracentrifugation is commonly used for the determination of molecular weights (sedimentation equilibrium) and sedimentation coefficients (sedimentation rate) of biological macromolecules in solution. A Turbo Pascal program for the analysis of sedimentation equilibrium centrifugation data produced by absorbance optical systems is described. The user may enter data from a scan of absorbance versus distance from the centre of rotation, via a graphics tablet (or ASCII file). This is subsequently manipulated to yield an apparent weight average molecular weight for the given sample. Plots of ln (absorbance) versus (radius2) may also be produced. The method described uses readily available computational equipment requiring only a graphics tablet in addition to an IBM PC compatible computer. This technique and the software developed have been used to investigate the molecular weight range of two International Humic Substances Society (IHSS) reference samples from the Suwannee River.  相似文献   
107.
D.P. Jones  D.C. Leach  D.R. Moore 《Polymer》1985,26(9):1385-1393
An outline of the characteristics of PEEK and the versatility of its compositional forms (micro and macro composites) are given to illustrate its wide potential for success in engineering applications. Although it is necessary to have particular tabulations of mechanical properties for engineering design, these are seldom available and consequently it is argued that an understanding of stiffness, toughness and strength properties are required to fully exploit available manufacturer's data and thus develop the full potential of PEEK and its composites. Stiffness characteristics are considered in terms of a modulus function which is dependent on time under load and temperature. In its composite forms, whether reinforced with short or continuous fibres, stiffness anistropy can be both considerable and complex, but some empirical ground-rules are apparent. For continuous fibre composites even in the form of complex lay-ups, it is also possible to attempt some stiffness prediction from certain pseudo-elastic constants. Toughness of PEEK and its composites is described in terms of both comparative and intrinsic properties. Instrumented falling weight impact data, particularly as a function of temperature enable some insight into ductile-brittle transitions for the unreinforced material, but crack initiation and crack propagation processes for the various fibre reinforced forms. Intrinsic toughness is described in terms of linear elastic fracture mechanics theory. Strength properties are described for static and dynamic loading configurations. In particular, PEEK and its composites are evaluated for increasing test severities for strength characteristics; stress concentration, loading form and test temperature are considered.  相似文献   
108.
109.
The noise generated by a ball mill during a batch grinding operation is investigated and the results show that, for a given ore, the noise levels may vary with time of grind, ore charge weight and mill speed. The role of the ore in absorbing noise energy is suggested as a possible control variable for the grinding process and as an indicator of product size distribution. The relationship between ore types and mill noise is also examined and, under conditions of wet grinding, it is demonstrated that mill noise analysis can indicate ore type and may have a possible use as a grindability-type parameter.  相似文献   
110.
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