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   4834篇
  免费   206篇
  国内免费   6篇
电工技术   37篇
综合类   14篇
化学工业   471篇
金属工艺   55篇
机械仪表   31篇
建筑科学   152篇
矿业工程   2篇
能源动力   51篇
轻工业   67篇
水利工程   7篇
石油天然气   2篇
无线电   189篇
一般工业技术   416篇
冶金工业   3092篇
原子能技术   9篇
自动化技术   451篇
  2024年   5篇
  2023年   50篇
  2022年   60篇
  2021年   99篇
  2020年   86篇
  2019年   79篇
  2018年   85篇
  2017年   70篇
  2016年   99篇
  2015年   98篇
  2014年   117篇
  2013年   133篇
  2012年   149篇
  2011年   161篇
  2010年   135篇
  2009年   93篇
  2008年   99篇
  2007年   88篇
  2006年   75篇
  2005年   53篇
  2004年   30篇
  2003年   19篇
  2002年   20篇
  2001年   16篇
  2000年   8篇
  1999年   100篇
  1998年   908篇
  1997年   507篇
  1996年   322篇
  1995年   176篇
  1994年   155篇
  1993年   174篇
  1992年   25篇
  1991年   39篇
  1990年   38篇
  1989年   46篇
  1988年   54篇
  1987年   55篇
  1986年   40篇
  1985年   35篇
  1983年   13篇
  1982年   15篇
  1981年   24篇
  1980年   41篇
  1979年   6篇
  1978年   14篇
  1977年   95篇
  1976年   221篇
  1975年   10篇
  1955年   1篇
排序方式: 共有5046条查询结果,搜索用时 15 毫秒
31.
The need for frequent injections and monitoring, the possibility of multiple gestations, and the higher cost compared to clomiphene citrate, prevents many clinicians from using human menopausal gonadotrophin (HMG) for ovulation induction. A sequential medication regimen, in which HMG is taken after clomiphene, overcomes these problems. We retrospectively compared per cycle fecundity and birth rates in 119 cycles of clomiphene-HMG, 524 cycles of clomiphene alone, 57 cycles of HMG alone, and 79 cycles of concurrent HMG and clomiphene in patients receiving intra-uterine insemination (IUI), who were free of endometriosis or tubal disease. Per cycle fecundity for clomiphene-HMG was 22% [95% confidence interval (CI) 12-34%], double that of clomiphene alone (11%) (95% CI 8-14%) (P < 0.01), and equal to HMG alone (18%) (95% CI 7-29%) or HMG and clomiphene together (19%) (95% CI 10-28%). The multiple birth rate for clomiphene-HMG (7/21) equalled that for HMG alone (3/12) and HMG and clomiphene together (3/8). The average number of ampoules of HMG required [follicle stimulating hormone (FSH) 75 mIU, luteinizing hormone (LH) 75 mIU] was decreased by 65% from 24.5 +/- 1.0 for HMG or HMG and clomiphene together to 8.6 +/- 0.3 for clomiphene-HMG (P < 0.001). Per cycle fecundity was identical when one, two or three ampoules of HMG per day were administered after clomiphene. We conclude that ovulation induction with sequential clomiphene-HMG results in fecundity double that of clomiphene alone and equal to HMG alone or concurrent with clomiphene, thereby reducing the requirement for HMG.  相似文献   
32.
33.
34.
Forty-eight patients with non-resectable cancer of the oesophagus and oesophagogastric junction (Group A: Stage I/II, 32; Group B: Stage III/IV, 16) underwent intraluminal Iridium-192 high dose-rate afterloading therapy (5-7 Gy/session, total dose: 5-21 Gy, mean: 12.4 Gy) and external beam irradiation (Karnofsky > or = 80% 50-60 Gy/2 Gy per day; Karnofsky 60-79%: 30 Gy/3 Gy per day). Durable satisfactory palliation (intake of at least semi-solid food) was demonstrated in 96% of patients. The mean survival for group A was 19.1 months and that for group B, 6.9 months, with a 12-month survival rate of 66% (group A) and 0% (group B) (P < 0.001). Local tumour response and complication rate were significantly dose-related with a predicted response rate of 70.5%, and a complication rate of 50% at ERD 129.3 Gy.  相似文献   
35.
We reported an operative case of bilateral coronary artery fistulae to pulmonary artery associated with a giant saccular aneurysm, the largest of which measured 30 x 30 mm. The patient was a 75 year old female who had anginal pain due to coronary steal phenomenon. A continuous murmur was detected. After establishing total cardiopulmonary bypass, two distal orifices of the fistula connected to the main pulmonary artery were closed with 5-0 polypropylene plegeted sutures. Aneurysmorrhaphy was then performed for giant saccular aneurysm. Postoperative course was uneventful.  相似文献   
36.
37.
38.
Obliterative or constrictive bronchiolitis is characterized by narrowing of the small airways, due to submucosal and peribronchiolar fibrosis, with chronic obstruction. The vast majority of cases of bronchiolitis obliterans are associated with other diseases and only few cases are idiopathic. We report on the main computed tomography (CT) methods used study obliterative bronchiolitis, the CT findings and the differential diagnosis with other diseases. The dynamic study of alveolar ventilation with CT uses inspiratory and expiratory CT or high-resolution CT (HRCT), spiral dynamic CT or HRCT with advanced image display, ultrafast CT. In abnormal cases HRCT shows direct and indirect signs of small airways disease. The most common (> 80%) sign of obliterative bronchiolitis is the so-called mosaic oligohemia, with low attenuating lobules, caused by air trapping and best seen on expiratory CT, associated with blood flow redistribution to more normal lobules; this finding simulates the ground-glass pattern from infiltrative lung disease. Differential diagnosis is more difficult in the presence of true ground-glass patterns associated with diffuse bronchiolar obstruction and also with mosaic oligohemia due to pulmonary vascular disease and pulmonary emphysema. HRCT can distinguish these diseases and dynamic CT is more sensitive than functional tests in detecting regional abnormalities and air trapping. The combination of HRCT, rapid volumetric scanning and advanced image display is a powerful tool study the normal and abnormal features of bronchiolar function and alveolar ventilation.  相似文献   
39.
40.
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