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   754篇
  免费   44篇
  国内免费   3篇
电工技术   13篇
综合类   1篇
化学工业   220篇
金属工艺   16篇
机械仪表   17篇
建筑科学   14篇
能源动力   25篇
轻工业   91篇
水利工程   5篇
石油天然气   7篇
无线电   91篇
一般工业技术   125篇
冶金工业   59篇
原子能技术   9篇
自动化技术   108篇
  2024年   4篇
  2023年   15篇
  2022年   42篇
  2021年   45篇
  2020年   42篇
  2019年   39篇
  2018年   34篇
  2017年   33篇
  2016年   30篇
  2015年   35篇
  2014年   41篇
  2013年   55篇
  2012年   53篇
  2011年   42篇
  2010年   26篇
  2009年   22篇
  2008年   26篇
  2007年   25篇
  2006年   15篇
  2005年   15篇
  2004年   12篇
  2003年   9篇
  2002年   13篇
  2001年   6篇
  2000年   10篇
  1999年   11篇
  1998年   9篇
  1997年   9篇
  1996年   10篇
  1995年   7篇
  1994年   6篇
  1993年   12篇
  1992年   6篇
  1991年   5篇
  1990年   3篇
  1989年   2篇
  1988年   5篇
  1987年   2篇
  1986年   3篇
  1985年   2篇
  1983年   3篇
  1982年   3篇
  1981年   4篇
  1980年   2篇
  1979年   4篇
  1977年   1篇
  1975年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有801条查询结果,搜索用时 15 毫秒
81.
Current distribution and input impedance of printed dipoles   总被引:5,自引:0,他引:5  
Printed dipole antennas find increasing use in microwave as well as far infrared frequencies. The current distribution, input impedance, and radiation pattern are computed for wire antennas printed on a dielectric substrate. The current distribution is obtained by solving Pocklington's equation by moment methods. The Green's function pertinent to the problem involves improper Sommerfeld-type integrals. These integrals are computed by a real-axis integration technique which involves analytical and numerical steps. The effect of surface modes is carefully taken into account.  相似文献   
82.
83.
84.
Presented herein are the studies of nutritional transport from capillary to tissues in normal and stenosed arteries. The model incorporates modified Casson's fluid representation for the blood and symmetric stenosis has been assumed at some distance from the entry. Assessment of the severity of the disease could be made possible through the variation of a parameter named as retention parameter. Nutritional flux at the capillary wall is affected by the growing stenosis and its variation has been observed through a decreasing trend of the retention parameter from 1 to 0. Results for local variation of viscosity contrary to Fahraeus-Lindquist effect have been explained. Symmetry of the distribution of the wall shearing stress and resistance to flow and their growth with the developing stenosis is another important feature of this analysis. Taylor diffusivity coefficient increases considerably with growing stenosis and the nutritional transport to the deeper cells of the tissue will naturally decrease.  相似文献   
85.
OBJECTIVE: To assess whether patients with deep vein thrombosis (DVT) could be satisfactorily treated on an outpatient basis with low molecular weight (LMW) heparin and warfarin. DESIGN: A 22 month prospective study of adults attending St Peter's Hospital accident and emergency department with DVT. RESULTS: 1093 patients were referred and assessed; 160 were venogram positive, of which 159 patients between the ages of 22 and 89 years of age have now been treated with LMW heparin as outpatients. Direct liaison with community nurses has minimised the impact on general practitioner workload. CONCLUSIONS: 1272 bed days were saved during this period (an estimated 320,000 pounds). The outpatient treatment of thromboembolism has been shown to be effective and safe.  相似文献   
86.
The problem of finding a minimum makespan permutation schedule in a deterministic flow-shop without intermediate queues is equivalent to the shortest distance routing traveling salesman problem. If the task system is semi-ordered, the associated distance matrix of the corresponding traveling salesman problem is found to exhibit some peculiar characteristics. Consequently, we are able to derive some important results which help us to eliminate permutations in the search of the minimum makespan permutation schedule. The most important result is that the optimal permutation schedule is pyramidal. An algorithm, having quadratic worst-case complexity in terms of the number of partial schedules explicitly enumerated, has been presented. Some particular cases of the semi-ordered flow-shop are also discussed.  相似文献   
87.
In this investigation, water side heat transfer coefficients without air flow from a single horizontal tubes are determined. Mass transfer coefficients are determined with water and air flow from the same tube. The total energy dissipated by inside hot fluid when only water is falling is compared with that when both the air and water flow past the tube. The water side heat transfer coefficient and mass transfer coefficient are given by empirical relations hw = 6.0(Rep)0.18(Rew)0.87 and K = 3.5(Rep)0.18(Rea)0.28 (Rew)0.54, respectively. The ratio of energies dissipated with water and air flow and with only water flow increases with Rew and Rea and its maximum value is 1.72 in the range of variables used.  相似文献   
88.
An analysis was made of a prospective database of 614 men with newly diagnosed carcinoma of the prostate who presented between January 1978 and December 1990; 3-monthly updates were available on their clinical, haematological and biochemical parameters and 6-monthly updates on chest X-rays, bone scans and skeletal X-rays. It was found that 107 men (mean age 73.5 years) had early disease at presentation. Their management was based on regular surveillance and the treatment deferred until disease progression or development of symptoms. The audit of outcome measured various clinical events. Four patients (3.7%) developed local failure, 11 (10.3%) developed bone metastases, 3 (2.8%) died of cancer with a median survival of 6.3 years, and 34 (31.8%) died of intercurrent disease with a median survival of 2.6 years. The observed survival for 12 years of the whole group was similar to the expected survival for an age-matched population in Scotland. The standardised mortality ratio was 81 (95% confidence limits 57-112).  相似文献   
89.
90.
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