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   445961篇
  免费   4963篇
  国内免费   1806篇
电工技术   7710篇
综合类   640篇
化学工业   65844篇
金属工艺   19381篇
机械仪表   13968篇
建筑科学   9736篇
矿业工程   3317篇
能源动力   10839篇
轻工业   32996篇
水利工程   5497篇
石油天然气   11939篇
武器工业   64篇
无线电   50625篇
一般工业技术   92662篇
冶金工业   80182篇
原子能技术   12246篇
自动化技术   35084篇
  2021年   3857篇
  2019年   3707篇
  2018年   6530篇
  2017年   6686篇
  2016年   7073篇
  2015年   4336篇
  2014年   7326篇
  2013年   19072篇
  2012年   11600篇
  2011年   15553篇
  2010年   12261篇
  2009年   13971篇
  2008年   14338篇
  2007年   14283篇
  2006年   12302篇
  2005年   11355篇
  2004年   10939篇
  2003年   10614篇
  2002年   10276篇
  2001年   10443篇
  2000年   9837篇
  1999年   10184篇
  1998年   25069篇
  1997年   17687篇
  1996年   13561篇
  1995年   10336篇
  1994年   9073篇
  1993年   9304篇
  1992年   6855篇
  1991年   6651篇
  1990年   6390篇
  1989年   6377篇
  1988年   6091篇
  1987年   5428篇
  1986年   5482篇
  1985年   6060篇
  1984年   5661篇
  1983年   5312篇
  1982年   4834篇
  1981年   4884篇
  1980年   4908篇
  1979年   4731篇
  1978年   4758篇
  1977年   5126篇
  1976年   6466篇
  1975年   4163篇
  1974年   4052篇
  1973年   4111篇
  1972年   3548篇
  1971年   3186篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
991.
992.
993.
The authors report a rare case of a large cystic cervical neurinoma. A 45-year-old female was admitted to our clinic because of motor weakness of the right upper extremity, numbness of the right fingers and right posterior cervical pain. Metrizamide CT myelography demonstrated the outline of a low density mass. MRI showed a mass revealing low signal intensity on T1-weighted image, high signal intensity on T2-weighted image and marginal enhancement on contrast image with Gd-DTPA. The mass which was diagnosed as cystic tumor, was located in the intradural extramedullary space between C4 to C5 segments. After C4 through C5 laminectomy, the tumor was found to originate from the C5 anterior motor root. The tumor consisted mostly of a cystic part with a very thin solid compartment beneath the capsule. Postoperative course of the patient was uneventful. Although spinal neurinoma is one of the most common spinal tumors, an almost completely degenerated large cystic spinal neurinoma is extremely rare. MRI with Gd-DTPA was useful for the diagnosis of the cystic neurinoma by clearly enhancing the margin of the tumor.  相似文献   
994.
Respiratory infections are the most common infection in children. They differ remarkably according to age, bacteria and viruses. Therefore a careful history of outbreak, age, former infections, involvement of surroundings, symptoms, etc are essential. The present study included 50 children, aged between 0.3 and 12 yrs, all treated ambulatorily. 21 received brodimoprim (B) and 29 erythromycin (E). Indications were: tonsillitis, bronchitis, otitis media, sinusitis and scarlet fever. Dosages were: B was given 10 mg/kg body weight (b.w.) initially followed by 5 mg/kg b.w., once-a-day. The duration of treatment varied between 4 and 14 days (mean 8.3 days). E was given 30.50 mg/kg b.w. 3 times per day; duration 4 to 14 days (mean 8.6 days). Overall results were: in group B:12 cures, 5 improvements, 3 failures; 1 not assessable. In group E: 20 cures, 8 improvements, 1 failure. Side effects: in group B: vomiting (1), skin reaction (2), discontinuation (2); in group E: skin reaction (1), diarrhea (5), diarrhea+vomiting (1); discontinuation (2). The differences in efficacy and tolerability in the two groups are not statistically significant. The improved compliance with a single versus t.i.d. dosages has to be taken into account.  相似文献   
995.
996.
In 28 dogs, oral malodor was assessed organoleptically (0-3 scale) and by measurement of volatile sulfur components (VSC), using two positions ('intraoral' and 'tooth surface') for sampling VSC. Significant correlations were found between: intraoral and tooth surface VSC collection positions (p < 0.0001) and between organoleptic and tooth surface VSC data (p < 0.0001). VSC measurement is a sensitive, repeatable and non-subjective method of assessing oral malodor in dogs.  相似文献   
997.
998.
A total of 700 patients who had carotid endarterectomy (CEA) in the UK and Ireland during a 6-month interval between March and August 1994 were studied prospectively. Some 108 patients (15.4 per cent) had a contralateral internal carotid artery occlusion. Previous reports have shown an associated stroke rate of about 10 per cent in these patients. This study assessed complications and outcome for patients undergoing CEA with contralateral internal carotid artery occlusion compared with those without. The indications for surgery were comparable between the two groups although the patients with occlusion had a slightly higher incidence of arrhythmia and stroke. Intraoperative shunts were used in a significantly higher proportion of those with occlusion (83.3 versus 64.7 per cent, P = 0.0001). The combined death and stroke rate for patients with occlusion was 5.6 per cent compared with 2.4 per cent for the remainder (P not significant). On the basis of the present data, CEA with a contralateral carotid artery occlusion carries only a slight increase in the rate of postoperative stroke and death. This increase was not statistically significant and is lower than that reported previously.  相似文献   
999.
1000.
We present a new approach to analyse the deformation of the left ventricle of the heart based on a parametric model that gives a compact representation of a set of points in a 3-D image. We present a strategy for tracking surfaces in a sequence of 3-D cardiac images. Following tracking, we then infer quantitative parameters which characterize: left ventricle motion, volume of left ventricle, ejection fraction, amplitude and twist component of cardiac motion. We explain the computation of these parameters using our model. Experimental results are shown in time sequences of two modalities of medical images, nuclear medicine and X-ray computed tomography (CT). Video sequences presenting these results are on the CD-ROM.  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