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   725篇
  免费   25篇
  国内免费   1篇
电工技术   1篇
化学工业   153篇
金属工艺   10篇
机械仪表   20篇
建筑科学   41篇
矿业工程   3篇
能源动力   13篇
轻工业   78篇
水利工程   6篇
石油天然气   1篇
无线电   34篇
一般工业技术   107篇
冶金工业   144篇
原子能技术   4篇
自动化技术   136篇
  2023年   4篇
  2022年   9篇
  2021年   21篇
  2020年   10篇
  2019年   11篇
  2018年   8篇
  2017年   12篇
  2016年   17篇
  2015年   11篇
  2014年   21篇
  2013年   41篇
  2012年   35篇
  2011年   45篇
  2010年   24篇
  2009年   34篇
  2008年   29篇
  2007年   25篇
  2006年   26篇
  2005年   20篇
  2004年   13篇
  2003年   18篇
  2002年   15篇
  2001年   8篇
  2000年   17篇
  1999年   12篇
  1998年   32篇
  1997年   22篇
  1996年   14篇
  1995年   14篇
  1994年   15篇
  1993年   10篇
  1992年   11篇
  1991年   4篇
  1990年   5篇
  1989年   8篇
  1988年   11篇
  1987年   7篇
  1985年   7篇
  1984年   8篇
  1983年   10篇
  1982年   7篇
  1981年   7篇
  1980年   10篇
  1979年   9篇
  1978年   5篇
  1977年   9篇
  1976年   12篇
  1974年   3篇
  1973年   3篇
  1969年   3篇
排序方式: 共有751条查询结果,搜索用时 62 毫秒
1.
A standard method for the extraction of tiger nut milk has been introduced. It has been shown that, although milling duration improves the yield of tiger nut milk solids and its nutrient composition, there is a quantifiable loss of nutrient in the pressing residue during milk extraction. Milling duration improved the colloidal stability of the milk against creaming during 16 h of storage. A higher milling intensity resulted in the aggregation of biological polymers which resulted in colloidal destabilisation. Milling improved the lightness and stability and reduced browning rate of the tiger nut milk during storage. This report is important for the production of tiger nut milk of consistent and comparable characteristics. Milling has been introduced as a processing method for the qualitative and quantitative modulation of the properties of tiger nut milk. It is recommended to develop further strategies to improve the colloidal stability of tiger nut milk as a beverage.  相似文献   
2.
3.
The dehydroalkylation of toluene with ethane to the isomeric ethyltoluenes was studied on 0.4Pt/H-ZSM-5 at varying contact times (1/WHSV). At a high contact time of 1.0 h, toluene disproportionation and hydrogenolysis reactions dominate, resulting in low selectivity to the desired ethyltoluenes via the alkylation reaction. However, at a low contact time of 0.12 h side reactions are eliminated, resulting in maximum selectivities to the kinetically favored ethyltoluenes and hydrogen. Results at high selectivities to ethyltoluenes provide significant insight into reaction pathways.  相似文献   
4.
Many everyday activities depend on the capacity to organize and smoothly execute motor sequences. The authors tested the hypothesis that a sequencing deficit is associated with schizophrenia. They used a new method to distinguish between lower and higher order mechanisms for the impairment. The 1st task involved triggered sequences in which sensory information from 1 movement was the cue for initiation of the following movement. Results showed that the motor sequences were performed as fluently in patients as in controls. The 2nd and 3rd tasks involved sequences in which the entire movement sequence could be preplanned. Patients executed the sequences less fluently than controls but only under the condition where action sequences were required. Furthermore, the patients' fluency deficit increased with sequence complexity. The high discrimination power of Task 3 gave the authors a means to control for a potential psychometric confound involving differential discriminating power and to argue in favor of a specific higher order motor fluency deficit in patients with schizophrenia. It is suggested that basic lower order mechanisms that integrate sensory information with outgoing motor commands are preserved in schizophrenia, whereas higher order integrative mechanisms that are required for the smooth coordination of motor sequences are impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
Alternative measures of pesticide use   总被引:2,自引:0,他引:2  
tRNA (m5U54)-methyltransferase (RUMT) catalyzes the S-adenosylmethionine-dependent methylation of uridine-54 in the T psi C-loop of all transfer RNAs in E. coli to form the 54-ribosylthymine residue. However, in all tRNA structures, residue 54 is completely buried and the question arises as to how RUMT gains access to the methylation site. A 17-mer RNA hairpin consisting of nucleotides 49-65 of the T psi-loop is a substrate for RUMT. Homonuclear NMR methods in conjunction with restrained molecular dynamics (MD) methods were used to determine the solution structure of the 17-mer T-arm fragment. The loop of the hairpin exhibits enhanced flexibility which renders the conventional NMR average structure less useful compared to the more commonly found situation where a molecule exists in predominantly one major conformation. However, when resorting to softer refinement methods such as MD with time-averaged restraints, the conflicting restraints in the loop can be satisfied much better. The dynamic structure of the T-arm is represented as an ensemble of 10 time-clusters. In all of these, U54 is completely exposed. The flexibility of the T psi-loop in solution in conjunction with extensive binding studies of RUMT with the T psi C-loop and tRNA suggest that the specificity of the RUMT/ tRNA recognition is associated with tRNA tertiary structure elements. For the methylation, RUMT would simply have to break the tertiary interactions between the D- and T-loops, leading to a melting of the T-arm structure and making U54 available for methylation.  相似文献   
6.
Hispanic children are the fastest growing segment of the population. Numerous factors place them at-risk for school success. This study examined the effects of Child-Centered Play Therapy (CCPT) compared to a curriculum-based small group intervention with 29 Hispanic children referred for school counseling due to behavior problems. Children were assigned to treatment groups by random drawing within grade levels. Treatment was provided by Hispanic bilingual counselors. Statistical analysis revealed that, according to parent report, children receiving CCPT showed statistically significant decreases in externalizing behavior problems, compared to the curriculum-based treatment group. Effect size calculations revealed that CCPT demonstrated a large treatment effect on externalizing behavior problems and a moderate treatment effect on internalizing behavior problems. Cultural considerations and recommendations for practice and future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
An expression is derived for the probability of error of an N th-order selection diversity system for the case where the receiver is forced to swell on one channel for several symbols before being allowed to make a decision regarding the best channel. It is found that the time-varying nature of a fading channel causes significant degradation of the probability of error when the dwell time becomes longer than about 10% of the inverse of the fading bandwidth of the channel. The onset of degradation is a function of the signal-to-noise ratio and of the order of diversity. Specific probabilities of error are calculated for differential phase-shift keyed modulation (DPSK). However, the calculations can be done for any other modulation technique  相似文献   
8.
Zusammenfassung  Der Wandel der Gesellschaft im Umgang mit personenbezogenen Daten sowie die stete Entwicklung technischer M?glichkeiten in der Datenverarbeitung haben l?ngst dazu beigetragen, dass Verbraucherinnen und Verbraucher im Wege der Erstellung umfassender Konsumentenprofile immer st?rker in die Rolle gl?serner Kunden gedr?ngt werden. Daten sammelnde Unternehmen stellen insoweit eine Gefahr für das Recht der Einzelnen auf informationelle Selbstbestimmung dar. Vor diesem Hintergrund befasst sich der Beitrag mit den datenschutzrechtlichen Anforderungen an Kundenbindungsprogramme und zeigt, wie sie datenschutzgerecht und verbraucherfreundlich gestaltet werden k?nnen.  相似文献   
9.
10.
A novel, unobtrusive and wearable, multiparameter ambulatory physiologic monitoring system for space and terrestrial applications, termed LifeGuard, is presented. The core element is a wearable monitor, the crew physiologic observation device (CPOD), that provides the capability to continuously record two standard electrocardiogram leads, respiration rate via impedance plethysmography, heart rate, hemoglobin oxygen saturation, ambient or body temperature, three axes of acceleration, and blood pressure. These parameters can be digitally recorded with high fidelity over a 9-h period with precise time stamps and user-defined event markers. Data can be continuously streamed to a base station using a built-in Bluetooth RF link or stored in 32 MB of on-board flash memory and downloaded to a personal computer using a serial port. The device is powered by two AAA batteries. The design, laboratory, and field testing of the wearable monitors are described.  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