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   1804篇
  免费   36篇
电工技术   8篇
化学工业   229篇
金属工艺   130篇
机械仪表   23篇
建筑科学   64篇
能源动力   25篇
轻工业   234篇
水利工程   16篇
石油天然气   9篇
无线电   152篇
一般工业技术   199篇
冶金工业   565篇
原子能技术   21篇
自动化技术   165篇
  2023年   7篇
  2022年   19篇
  2021年   26篇
  2020年   12篇
  2019年   23篇
  2018年   25篇
  2017年   17篇
  2016年   34篇
  2015年   14篇
  2014年   35篇
  2013年   101篇
  2012年   55篇
  2011年   83篇
  2010年   64篇
  2009年   69篇
  2008年   92篇
  2007年   97篇
  2006年   60篇
  2005年   47篇
  2004年   56篇
  2003年   31篇
  2002年   37篇
  2001年   37篇
  2000年   41篇
  1999年   42篇
  1998年   101篇
  1997年   62篇
  1996年   44篇
  1995年   40篇
  1994年   33篇
  1993年   29篇
  1992年   27篇
  1991年   23篇
  1990年   14篇
  1989年   20篇
  1988年   27篇
  1987年   14篇
  1986年   24篇
  1985年   23篇
  1984年   23篇
  1983年   16篇
  1982年   21篇
  1981年   21篇
  1980年   14篇
  1979年   17篇
  1978年   13篇
  1977年   23篇
  1976年   27篇
  1975年   10篇
  1974年   13篇
排序方式: 共有1840条查询结果,搜索用时 318 毫秒
71.
随着家电行业国际化竞争的加剧,家电企业纷纷将注意力转向"创新"这个时下热门的词汇以期在竞争中能够取得领先。  相似文献   
72.
Brook trout (Salvelinus fontinalis) are found throughout Lake Superior, Lake Nipigon, and their tributaries. Lacustrine and adfluvial life history variants were historically popular with anglers and were called coasters; coaster brook trout populations are now severely reduced and are of conservation concern. Coasters were known to grow larger and mature later than their stream resident counterparts. This study compared movement patterns, age, size, condition, and relative weight of wild coaster and resident brook trout from the Hurricane River, Pictured Rocks National Lakeshore, Michigan. Wild brook trout ≥ 100 mm from the Hurricane River downstream from Hurricane Falls were tagged with passive integrated transponder tags and monitored for stream-lake movement behavior from May 2003 to November 2007. During 2006 and 2007, brook trout were scale sampled and aged to construct a regression that was then used to calculate the age of all brook trout tagged from 2003 to 2007. Most brook trout movement took place in the fall with October the peak month of emigration with a secondary peak in late spring/early summer and some activity nearly year round. There were no differences found in age structure, size or condition between coasters and residents while in the stream. Our data suggest that a priori growth differences are not determining the expression of coaster outmigration and that stream-lake movements made by coasters, likely driven by habitat requirements, may be highly flexible and facultative.  相似文献   
73.
As our elderly population increases in proportion with respect to the rest of society, age-related driving impairments are increasing in importance as a public health concern. In this context, health professionals play an important role in identifying impaired drivers. This situation is complicated for two reasons: discussion of driving cessation is a sensitive topic for both health professionals and the elderly, and physicians have limited familiarity with the current American Medical Association (AMA) screening guidelines or mandated reporting laws.  相似文献   
74.
Fetal alcohol syndrome (FAS) is the leading birth defect in the United States, yet few treatment options exist for children afflicted with this disorder. Although play therapy has demonstrated its efficacy with numerous special populations, as of today, no research has been conducted on its use with FAS. This article presents an overview of current data on FAS, an argument for the use of child-centered play therapy for children diagnosed FAS, and suggests areas of research needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
75.
76.
77.
One contributing factor to difficulty in quitting smoking may be task persistence, which can be viewed as a behavioral manifestation of distress tolerance, and describes the act of persisting in a difficult or effortful task. Task persistence was assessed in smokers with schizophrenia and schizoaffective disorder (SZ/SA; N = 71) and non-psychiatric controls (N = 78) before a quit attempt. These data support the hypothesis that smokers with SZ/SA display less task persistence than do non-psychiatric controls when persistence is measured via mirror tracing and a 2-item persistence measure. Lower persistence may partially explain the reduced smoking cessation successes of smokers with SZ/SA as compared to the general population. These data also replicate findings regarding relationships between histories of ability to quit smoking and task persistence and expand them to a new population of smokers. The absence of a diagnostic status by length of previous abstinence interaction suggests that the contribution of task persistence to smoking cessation is similar for smokers with and without schizophrenia. Future studies should evaluate the ability of task persistence to predict abstinence from cigarettes prospectively among smokers with schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
78.
Our objective was to determine if prepubertal rate of body weight (BW) gain, independent of diet, was related to mammary development of dairy heifers. Data from two studies recently conducted at Michigan State University were used to identify factors, within a dietary treatment group, that would account for variation in first lactation milk production or amount of mammary parenchymal DNA at the time of puberty. Factors analyzed for variation in milk production during first lactation were: postpartum BW, prepubertal BW gain, gestational BW gain, postpartum BW gain, body condition score (BCS) at breeding, and BCS at calving. Factors analyzed for variation in mammary parenchymal DNA at puberty were: BW at slaughter, age at puberty, prepubertal BW gain and body protein and body fat content at slaughter. For both analyses, prepubertal BW gain did not account for any of the variation in mammary development. The only significant covariate for the milk production model (r2 = 0.44) was BCS at breeding. Similarly, the only significant covariate in the parenchymal DNA model (r2 = 0.22) was body fat content at slaughter. These results suggest that, within a dietary treatment, heifers that grow faster do not have impaired mammary development, and increased body fatness may be a better predictor of impaired mammary development than BW gain.  相似文献   
79.
The electrode response time and the measured concentrations during dynamic catecholamine changes were compared using constant potential amperometry and fast-scan cyclic voltammetry. The amperometric response to a rectangular pulse of catecholamine is more rectangular than the cyclic voltammetric response; however, the response times are very similar when, during cyclic voltammetry, the temporal lag due to adsorption and desorption of catecholamine to the electrode is removed by deconvolution. Deconvolution of cyclic voltammetry data was applied to stimulated dopamine release in vivo, allowing for modeling of release and uptake kinetics and to measure catecholamine release from single cells, resulting in better resolution of peaks from single vesicles. In vitro postcalibrations were performed to calculate concentrations of catecholamine measured with cyclic voltammetry and amperometry. The addition of 600 microM ascorbic acid to the postcalibration buffer, allowing a catalytic reaction to regenerate dopamine, resulted in similar calculated concentrations for stimulated release of dopamine using amperometry and cyclic voltammetry. Using deconvoluted cyclic voltammetry to remove the response time lag and adding ascorbic acid to the calibration buffer, the shape and concentration of dynamic catecholamine changes are very similar when measured with constant potential amperometry and cyclic voltammetry.  相似文献   
80.
In hamsters, adolescent anabolic-androgenic steroid (AAS) exposure facilitates offensive aggression, in part by altering the development and activity of anterior hypothalamic arginine vasopressin (AH-AVP). This study assessed whether these effects were lasting by examining aggression and AH-AVP during AAS withdrawal. Adolescent hamsters administered AAS were tested as adults for aggression at 1, 4, 11, 18, or 25 days of withdrawal, sacrificed the following day, and examined for AH-AVP afferent innervation using immunohistochemistry. Through Day 12 of withdrawal, aggression and AVP were significantly higher in AAS-treated hamsters than in controls. These differences were no longer observable by Day 19 of withdrawal, at which point the behavior and neurobiology of AAS-treated hamsters reverted to that observed in controls. These data indicate that adolescent AAS exposure has short-term, reversible effects on both aggression and AH-AVP, correlating AH-AVP with the aggressive/nonaggressive behavioral phenotype during AAS withdrawal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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