全文获取类型
收费全文 | 445961篇 |
免费 | 4963篇 |
国内免费 | 1806篇 |
专业分类
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 |
出版年
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.
M Sato A Kondo S Otsuka H Tanabe N Matsuura K Hasegawa M Chin M Saiki 《Canadian Metallurgical Quarterly》1993,21(12):1143-1147
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.
Y Shioda S Koizumi S Furuya S Akira N Kameyama N Hamano W Takahashi A Tokunaga N Tanaka M Onda 《Canadian Metallurgical Quarterly》1993,23(6):556-561
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.
AF da Silva P McCollum T Szymanska L de Cossart 《Canadian Metallurgical Quarterly》1996,83(10):1370-1372
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