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   2504篇
  免费   96篇
  国内免费   14篇
电工技术   53篇
综合类   5篇
化学工业   548篇
金属工艺   76篇
机械仪表   79篇
建筑科学   66篇
矿业工程   9篇
能源动力   74篇
轻工业   282篇
水利工程   22篇
石油天然气   8篇
无线电   146篇
一般工业技术   429篇
冶金工业   486篇
原子能技术   20篇
自动化技术   311篇
  2023年   27篇
  2022年   29篇
  2021年   70篇
  2020年   35篇
  2019年   54篇
  2018年   76篇
  2017年   71篇
  2016年   98篇
  2015年   76篇
  2014年   94篇
  2013年   160篇
  2012年   140篇
  2011年   154篇
  2010年   104篇
  2009年   97篇
  2008年   92篇
  2007年   91篇
  2006年   68篇
  2005年   63篇
  2004年   46篇
  2003年   33篇
  2002年   45篇
  2001年   27篇
  2000年   25篇
  1999年   34篇
  1998年   137篇
  1997年   89篇
  1996年   74篇
  1995年   39篇
  1994年   33篇
  1993年   31篇
  1992年   19篇
  1990年   16篇
  1989年   10篇
  1988年   17篇
  1987年   10篇
  1986年   12篇
  1985年   21篇
  1984年   21篇
  1983年   17篇
  1982年   12篇
  1981年   20篇
  1980年   18篇
  1979年   16篇
  1978年   12篇
  1977年   17篇
  1976年   36篇
  1974年   11篇
  1973年   17篇
  1940年   10篇
排序方式: 共有2614条查询结果,搜索用时 15 毫秒
11.
12.
Smokers with smoking-related diseases who are hospitalized in rehabilitation centers should be offered smoking cessation. This is the first study evaluating whether telephone booster sessions after intensive inpatient treatment are an effective strategy. The present study was conducted in 13 rehabilitation centers for somatic disorders as a prospective multicenter study with a randomized treatment-control group design. We compared abstinence rates after hospital discharge from treatment that included a group smoking cessation program with (treatment group) and without telephone booster sessions (control group). Data from 290 smokers were analyzed. After 6 and 12 months the treatment group achieved abstinence rates twice as high as those of the control group. Men profited more from telephone booster sessions than did women. Results indicated that telephone booster sessions were highly effective (even) after an inherently intensive group program during a hospital stay. Further research should focus on the special needs of women receiving telephone counseling.  相似文献   
13.
14.
Initiation and early propagation of pitting and filiform corrosion on bare alloy AZ91 (9% Al, 1% Zn) are investigated by natural immersion corrosion tests, electrochemical measurements and microanalytical studies. Initiation sites are few. Corrosion spreads from these sites first in the form of filiform corrosion for a limited period of time and pitting which later develops into a cellular type of etching. The important factors affecting filiform corrosion are temperature, material structure and degree of polarization at the anodic sites. Filiform attack on AZ91, unlike the classical mechanisms of filiform corrosion on coated metals, is driven by hydrogen evolution reaction on the cathodic sites of the surface, occurs under significant anodic control, propagates at a high, constant speed independent of degree of polarization along preferential paths determined by compositional and crystallographic factors, and is a temporary phenomenon under open circuit conditions. Pitting corrosion is more predominant with decreasing anodic polarization.  相似文献   
15.
PURPOSE: The clinical effect of high-dose-rate (HDR) interstitial brachytherapy combined with tumor resection was investigated in this retrospective study on patients with recurrent oral and oropharyngeal squamous cell carcinoma. PATIENTS AND METHODS: Oral and oropharyngeal squamous cell carcinoma in 38 patients were treated over a period of 7 years (1988-1994) by HDR interstitial brachytherapy using Gammamed 12i equipment. Pretreatment of patients in terms of irradiation and surgery differed (33 irradiated with a total dose between 60.0 and 75.6 Gy, including 8 patients with additional surgery; 1 patient with surgery alone, and 4 patients without any pretreatment). Indications for interstitial brachytherapy differed according to individual responses to treatment and medical histories. RESULTS: Interstitial brachytherapy was successful in the majority of patients, i.e. complete remission: 12, partial remission: 19, no change: 2, progression: 5. Local control and overall survival including patients with surgical treatment was 59% and 81% at 6 months and 47% and 49% after 12 months, respectively. CONCLUSION: Interstitial HDR brachytherapy with Iridium 192 is recommended in patients with local recurrences or second primary carcinomas after previous external radiotherapy in the head and neck region. Combination of interstitial brachytherapy and surgery is preferable for these patients.  相似文献   
16.
The development of plants and processes for the manufacture of wood based board products is reported in several papers. Within the belt-matforming system the pre-presses, the driving systems, the press controll system withouth, distance bars and the belt materials have been developed. The continuously working hotpress Contiroll may be seen as a completely new construction, which has now passed its proofing period and has gone into production. A new vaporpress-process and its possibilities is discribed and some innovations at the matforming machines and the pressing lines for the OSB-production are discussed.  相似文献   
17.
The aim of our study was to show the results of the Magnetic Resonance Angiography of pelvis and lower extremities. 21 patients with clinical signs of venous thrombosis were examined. The obtained results show the MRA is very useful in evaluation of venous flow.  相似文献   
18.
19.
We present a bead-based approach to microfluidic polymerase chain reaction (PCR), enabling fluorescent detection and sample conditioning in a single microchamber. Bead-based PCR, while not extensively investigated in microchip format, has been used in a variety of bioanalytical applications in recent years. We leverage the ability of bead-based PCR to accumulate fluorescent labels following DNA amplification to explore a novel DNA detection scheme on a microchip. The microchip uses an integrated microheater and temperature sensor for rapid control of thermal cycling temperatures, while the sample is held in a microchamber fabricated from (poly)dimethylsiloxane and coated with Parylene. The effects of key bead-based PCR parameters, including annealing temperature and concentration of microbeads in the reaction mixture, are studied to achieve optimized device sensitivity and detection time. The device is capable of detecting a synthetically prepared section of the Bordetella pertussis genome in as few as 10 temperature cycles with times as short as 15?min. We then demonstrate the use of the procedure in an integrated device; capturing, amplifying, detecting, and purifying template DNA in a single microfluidic chamber. These results show that this method is an effective method of DNA detection which is easily integrated in a microfluidic device to perform additional steps such as sample pre-conditioning.  相似文献   
20.
The influence of different centralised pre-packaging systems (PVC, modified atmosphere packaging (MAP), 25% CO(2) and 75% O(2), vacuum skin packaging (VSP) and the mother bag concept, 100% CO(2)) on the shelf-life (0, 7, 14 and 21 days at 0°C) of fresh pork was determined using microbiological, colour, odour and acceptability characteristics. All the packaging treatments were equally efficient for the first 4 days of retail display. In the extended shelf-life study (7, 14 and 21 days) the mother bag centralised packaging system gave the most promising shelf-life results (21 days) and was also judged superior in terms of odour. Modified atmosphere packaging (14 days) and VSP (7 days) may be considered as other possible options.  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