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   12658篇
  免费   458篇
  国内免费   12篇
电工技术   121篇
综合类   16篇
化学工业   2483篇
金属工艺   221篇
机械仪表   240篇
建筑科学   730篇
矿业工程   23篇
能源动力   314篇
轻工业   1013篇
水利工程   89篇
石油天然气   41篇
武器工业   1篇
无线电   701篇
一般工业技术   2235篇
冶金工业   2913篇
原子能技术   147篇
自动化技术   1840篇
  2023年   60篇
  2022年   119篇
  2021年   197篇
  2020年   127篇
  2019年   167篇
  2018年   213篇
  2017年   218篇
  2016年   253篇
  2015年   205篇
  2014年   324篇
  2013年   817篇
  2012年   489篇
  2011年   696篇
  2010年   471篇
  2009年   527篇
  2008年   583篇
  2007年   603篇
  2006年   559篇
  2005年   497篇
  2004年   406篇
  2003年   390篇
  2002年   355篇
  2001年   237篇
  2000年   228篇
  1999年   255篇
  1998年   381篇
  1997年   284篇
  1996年   272篇
  1995年   248篇
  1994年   216篇
  1993年   190篇
  1992年   185篇
  1991年   126篇
  1990年   135篇
  1989年   161篇
  1988年   144篇
  1987年   137篇
  1986年   143篇
  1985年   155篇
  1984年   135篇
  1983年   126篇
  1982年   107篇
  1981年   113篇
  1980年   82篇
  1979年   95篇
  1978年   106篇
  1977年   95篇
  1976年   102篇
  1975年   70篇
  1974年   63篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
This study investigated the Stages of Change Readiness and Treatment Eagerness Scale (SOCRATES: W. R. Miller & J. S. Tonigan, 1996) in adolescents presenting for treatment of alcohol use disorder (AUD). The participants were 80 males and 43 females (mean age=16.8 years) who presented for AUD treatment (95.1% outpatient, 4.9% inpatient). Participants completed assessments at baseline and 1 year and provided information on alcohol use and related variables monthly between these 2 assessments. Principal-components and confirmatory factor analyses of the baseline SOCRATES identified 2 factors, Taking Steps and Recognition, which showed good internal consistency and concurrent and predictive evidence of validity. The results were interpreted as supporting the use of the SOCRATES with clinical samples of adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
52.
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents.  相似文献   
53.
The Euler equations associated with diffeomorphism groups have received much recent study because of their links with fluid dynamics, computer vision, and mechanics. In this article, we consider the dynamics of N point particles or “blobs” moving under the action of the Euler equations associated with the group of diffeomorphisms of the plane in a variety of different metrics. This dynamical system is already in widespread use in the field of image registration, where the point particles correspond to image landmarks, but its dynamical behavior has not previously been studied. The 2-body problem is always integrable, and we analyze its phase portrait under different metrics. In particular, we show that 2-body capturing orbits (in which the distances between the particles tend to 0 as t  → ∞) can occur when the kernel is sufficiently smooth and the relative initial velocity of the particles is sufficiently large. We compute the dynamics of these “dipoles” with respect to other test particles, and supplement the calculations with simulations for larger N that illustrate the different regimes.  相似文献   
54.
It has been reported that it is harder to switch to a strong, well-practiced task from a weaker, less-practiced task than vice versa. Three experiments replicated this surprising asymmetry and investigated how it is affected by a reduction in interference between tasks. Experiment 1 progressively delayed the onset of the stimulus attribute associated with the stronger task. Experiments 2 and 3 separated the response sets of the tasks. Both manipulations reduced, without eliminating, interference of the stronger with the weaker task but reversed the asymmetry of switch costs, resulting in a larger cost of switching to the weaker task. The results are interpreted in terms of a model of the interactions between control input, task strength, and task priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
55.
This article examines the psychological impact of participating in sigmoidoscopy screening for colorectal cancer prevention. The 1st study examined psychological well-being at 3 months, in relation to screening outcome, in 4,153 individuals. The 2nd study used longitudinal data to examine changes in psychological functioning from before to after screening in relation both to screening outcome and baseline indicators of vulnerability. There were few psychological differences between those who had received negative results or had polyps detected. These findings were confirmed in the longitudinal study, which also found no evidence for vulnerability to adverse effects among those who were initially most anxious or who perceived their risk of cancer to be higher. The longitudinal data suggested that screening might produce transient positive effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
56.
57.
58.
Over the last century, IQ scores have been steadily rising, a phenomenon dubbed the Flynn effect. Because of the Flynn effect, IQ tests are periodically renormed, making them harder. Given that eligibility for mental retardation (MR) services relies heavily on IQ scores, renormed tests could have a significant impact on MR placements. In longitudinal IQ records from 9 sites around the country, students in the borderline and mild MR range lost an average of 5.6 points when retested on a renormed test and were more likely to be classified MR compared with peers retested on the same test. The magnitude of the effect is large and affects national policies on education, social security, the death penalty, and the military. This paper reports the perceptions of professionals as they relate to IQ score fluctuations in normal, borderline, and/or MR populations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
59.
60.
This paper reports a method to produce networks of crystalline gallium oxide comprised of one‐dimensional (1D) nanostructures. Because of the unique arrangement of wires, these crystalline networks are termed as ‘nanowebs’. Nanowebs are of great technological interest since they contain wire densities of the order of 109 cm–2. A possible mechanism for the fast self‐assembly of crystalline metal oxide nanowires involves multiple nucleation and coalescence via oxidation–reduction reactions at the molecular level. The preferential growth of nanowires parallel to the substrate enabled them to coalesce into regular polygonal networks. The individual segments of the polygonal network consist of both nanowires and nanotubules of β‐gallium oxide. Individual wire properties contribute to a nanoweb’s overall capacity and the implications for devices based on nanowebs are expected to be enormous.  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