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   1423篇
  免费   50篇
  国内免费   4篇
电工技术   31篇
综合类   3篇
化学工业   250篇
金属工艺   38篇
机械仪表   14篇
建筑科学   48篇
矿业工程   2篇
能源动力   36篇
轻工业   90篇
水利工程   12篇
石油天然气   2篇
无线电   148篇
一般工业技术   218篇
冶金工业   407篇
原子能技术   9篇
自动化技术   169篇
  2023年   15篇
  2022年   25篇
  2021年   39篇
  2020年   29篇
  2019年   33篇
  2018年   37篇
  2017年   38篇
  2016年   29篇
  2015年   18篇
  2014年   34篇
  2013年   68篇
  2012年   56篇
  2011年   61篇
  2010年   46篇
  2009年   45篇
  2008年   62篇
  2007年   44篇
  2006年   28篇
  2005年   35篇
  2004年   30篇
  2003年   27篇
  2002年   21篇
  2001年   26篇
  2000年   17篇
  1999年   31篇
  1998年   99篇
  1997年   69篇
  1996年   34篇
  1995年   34篇
  1994年   22篇
  1993年   25篇
  1992年   8篇
  1991年   18篇
  1990年   16篇
  1989年   9篇
  1988年   7篇
  1987年   15篇
  1986年   11篇
  1984年   14篇
  1983年   13篇
  1982年   10篇
  1981年   13篇
  1980年   12篇
  1979年   8篇
  1978年   12篇
  1977年   18篇
  1976年   26篇
  1975年   8篇
  1974年   12篇
  1973年   8篇
排序方式: 共有1477条查询结果,搜索用时 15 毫秒
101.
Examined the effects of 3 variables on reports of psychological functioning in 28 obese women (mean age 42.1 yrs) who lost an average of 19.2 kg in 6 mo. Analysis of the 1st variable, frequency of assessment, showed that although Ss experienced improvements in mood from pre- to posttreatment, more than 50% showed worsening in mood during 1 or more wks. Analysis of the 2nd variable, time of assessment, revealed that retrospective reports of depression and anxiety were greater than were concurrent reports. Analysis of the 3rd variable, method of assessment, showed that Ss reported several symptoms in response to an open-ended interview that were not measured by objective tests. Data indicate that the method of mood assessment determines the answer to the question of whether dieting is associated with adverse psychological consequences. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
Complex resonances of conducting spheres with lossy coatings   总被引:1,自引:0,他引:1  
The electromagnetic scattering amplitude for metal objects coated with a lossless dielectric exhibits a large number of resonances versus real frequency. These resonances are a function of the object shape and size, coating thickness, and coating electrical properties. Previously, it was shown that for coated spheres and nonspherical bare objects, these resonances can be understood in terms of phase matched circumnavigating surface waves and the objects' complex eigenfrequencies. The effect of dielectric loss in the coating on the complex eigenfrequencies and phase velocities of these surface waves is presented for a metal sphere coated with a uniform homogeneous dielectric coating. It is seen that the positions of the complex resonance frequencies move away from the real frequency axis under the influence of dielectric loss in the coating. The effect of this is shown to correspond to the changes in the backscatter spectrum versus real frequency as computed using a Mie series expansion. The significant difference between the lossless and lossy dielectric-coated sphere cases is seen to be due to a modification of the phase velocities of surface waves, particularly the whispering gallery types, and the increased attenuation of the surface wave modes  相似文献   
103.
104.

Background  

High-intensity interval training has been shown to be a time-efficient way to induce physiological adaptations similar to those of traditional endurance training. Creatine supplementation may enhance high-intensity interval training, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of high-intensity interval training (HIIT) and creatine supplementation on cardiorespiratory fitness and endurance performance (maximal oxygen consumption (VO2PEAK), time-to-exhaustion (VO2PEAKTTE), ventilatory threshold (VT), and total work done (TWD)) in college-aged men.  相似文献   
105.
Power allocation across users in two adjacent cells is studied for a code-division multiple access (CDMA) data service. The forward link is considered and cells are modeled as one-dimensional with uniformly distributed users and orthogonal signatures within each cell. Each user is assumed to have a utility function that describes the user's received utility, or willingness to pay, for a received signal-to-interference-plus-noise ratio (SINR). The objective is to allocate the transmitted power to maximize the total utility summed over all users subject to power constraints in each cell. It is first shown that this optimization can be achieved by a pricing scheme in which each base station announces a price per unit transmitted power to the users, and each user requests power to maximize individual surplus (utility minus cost). Setting prices to maximize total revenue over both cells is also considered, and it is shown that, in general, the solution is different from the one obtained by maximizing total utility. Conditions are given for which independent optimization in each cell, which leads to a Nash equilibrium (NE), is globally optimal. It is shown that, in general, coordination between the two cells is needed to achieve the maximum utility or revenue.  相似文献   
106.
Zusammenfassung Für verschiedene Phasen- und Lochzahlen je Pol und Phase sind die Werte der abgeleiteten Beziehung, die auch für Phasenzahlen kleiner als 1 ihre Gültigkeit behält, in einer Tafel zusammengestellt. In Anbetracht der Vorteile von vielphasigen Wicklungen wird eine 12phasige Schaltung für 3phasigen Netzanschlu\ angegeben.Mit Rücksicht auf die Wichtigkeit für die Berechnung der Drehmomente von Oberfeldern sind für den Käfiganker die Werte der doppeltverketteten Streuung in Abhängigkeit von den Phasenzahlen (m=0,3 bis 40) in Kurvenform dargestellt. Diese gelten auch für die sogenannten oberfeldarmen Wicklungen, bei denen die Phasenzahl durch Kunstschaltungen soweit erhöht wird, da\ nur mehr die Lochzahlq=1 verbleibt.Bezeichnungen m Phasenzahl des Strombelages - q Stabzahl je Polpaar und Phase - d Koeffizient der doppeltverketteten Streuung - Ordnungszahl der Stäbe je Pol und Phase - Ordnungszahl der Phasen - v Ordnungszahl der Oberfelder - Abszisse des ersten Stabes der ersten Phase (Bogenma\) - x Abszisse der Feldkurve in elektrischen Graden - zeitlicher Phasenwinkel des Stromes der ersten Phase ( elektr.) - p Polpaarzahl - y Ordinate der Feldkurve - y 1 Amplitude der Grundwelle - v Amplitude desv-ten Kosinusgliedes - b v Amplitude desv-ten Sinusgliedes - Z Zähnezahl des Käfigläufers  相似文献   
107.
The Open Channel     
Jordan  R.F. Chesley  G. 《Computer》1987,20(3):80-80
  相似文献   
108.
Monoterpenoid content of sage grouse ingesta   总被引:1,自引:0,他引:1  
We tested the hypothesis that the monoterpenoid levels in the ingesta from various digestive organs of sage grouse are less than that expected from the big sagebrush leaves ingested. Results supported the hypothesis. Dramatic reductions occurred between the gizzard and duodenum. Monoterpenoid levels in the ceca were nil; thus adverse effects of monoterpenoids on ceca microbes would also be nil.The use of trade or firm names in this paper is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service.  相似文献   
109.
Nagourney  Tal  Jordan  Jonathan  Marsh  Laban  Scardino  Dennis  May  Brian M. 《Fire Technology》2022,58(2):1065-1066
Fire Technology - The original publication of the article unfortunately contained a mistake in Figure 2c.  相似文献   
110.
Published data on photovoltaic (PV) degradation measurements were aggregated and re‐examined. The subject has seen an increased interest in recent years resulting in more than 11 000 degradation rates in almost 200 studies from 40 different countries. As studies have grown in number and size, we found an impact from sampling bias attributable to size and accuracy. Because of the correlational nature of this study we examined the data in several ways to minimize this bias. We found median degradation for x‐Si technologies in the 0.5–0.6%/year range with the mean in the 0.8–0.9%/year range. Hetero‐interface technology (HIT) and microcrystalline silicon (µc‐Si) technologies, although not as plentiful, exhibit degradation around 1%/year and resemble thin‐film products more closely than x‐Si. Several studies showing low degradation for copper indium gallium selenide (CIGS) have emerged. Higher degradation for cadmium telluride (CdTe) has been reported, but these findings could reflect a convolution of less accurate studies and longer stabilization periods for some products. Significant deviations for beginning‐of‐life measurements with respect to nameplate rating have been documented over the last 35 years. Therefore, degradation rates that use nameplate rating as reference may be significantly impacted. Studies that used nameplate rating as reference but used solar simulators showed less variation than similar studies using outdoor measurements, even when accounting for different climates. This could be associated with confounding effects of measurement uncertainty and soiling that take place outdoors. Hotter climates and mounting configurations that lead to sustained higher temperatures may lead to higher degradation in some, but not all, products. Wear‐out non‐linearities for the worst performing modules have been documented in a few select studies that took multiple measurements of an ensemble of modules during the lifetime of the system. However, the majority of these modules exhibit a fairly linear decline. Modeling these non‐linearities, whether they occur at the beginning‐of‐life or end‐of‐life in the PV life cycle, has an important impact on the levelized cost of energy. Copyright © 2016 John Wiley & Sons, Ltd.  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