全文获取类型
收费全文 | 1077篇 |
免费 | 10篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 51篇 |
金属工艺 | 6篇 |
机械仪表 | 6篇 |
建筑科学 | 31篇 |
能源动力 | 12篇 |
轻工业 | 31篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 82篇 |
一般工业技术 | 80篇 |
冶金工业 | 646篇 |
原子能技术 | 13篇 |
自动化技术 | 113篇 |
出版年
2020年 | 6篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2013年 | 29篇 |
2012年 | 21篇 |
2011年 | 12篇 |
2010年 | 17篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 19篇 |
2006年 | 27篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 16篇 |
2002年 | 12篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 33篇 |
1998年 | 148篇 |
1997年 | 84篇 |
1996年 | 57篇 |
1995年 | 33篇 |
1994年 | 30篇 |
1993年 | 45篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 12篇 |
1983年 | 20篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 29篇 |
1976年 | 34篇 |
1975年 | 11篇 |
1974年 | 15篇 |
1973年 | 17篇 |
1972年 | 7篇 |
1971年 | 7篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1967年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有1087条查询结果,搜索用时 0 毫秒
21.
MR Harrison GB Mychaliska CT Albanese RW Jennings JA Farrell S Hawgood P Sandberg AH Levine E Lobo RA Filly 《Canadian Metallurgical Quarterly》1998,33(7):1017-22; discussion 1022-3
BACKGROUND/PURPOSE: Fetuses with congenital diaphragmatic hernia (CDH) who have a "poor prognosis" with postnatal treatment now can be identified on the basis of liver herniation, early diagnosis (before 25 weeks' gestation) and a low lung-to-head ratio (LHR). Because complete in utero repair proved unsuccessful for this group, the strategy of temporary tracheal occlusion was developed to gradually enlarge the hypoplastic fetal lung. The purpose of this study is to compare the outcome of patients in the poor-prognosis group treated by one of three methods: (1) standard postnatal care, (2) fetal tracheal occlusion via open hysterotomy, and (3) the recently developed video-fetoscopic (Fetendo) technique of tracheal occlusion without hysterotomy. METHODS: In the past 3 years, 34 of 86 fetuses with an isolated left CDH met criteria for the poor-prognosis group. Thirteen families chose postnatal treatment at an extracorporeal membrane oxygenation (ECMO) center, 13 underwent open fetal tracheal occlusion, and eight underwent fetoscopic tracheal occlusion. RESULTS: The survival rate was 38% in the group treated by standard postnatal therapy, 15% in the open tracheal occlusion group, and 75% in the Fetendo group. There were less postoperative pulmonary complications noted in mothers who underwent the Fetendo procedure versus the open tracheal occlusion. All but one Fetendo clip patient had a striking physiological response demonstrated by sonographic enlargement of the small left lung that was documented postnatally by plain radiographs and its subjective appearance during repair of the CDH. In contrast, only 5 of the 13 open tracheal occlusion patients demonstrated lung growth. CONCLUSION: Fetuses with a left CDH who have liver herniation and a low LHR are at high risk of neonatal demise and appear to benefit from temporary tracheal occlusion when performed fetoscopically, but not when performed by open fetal surgery. 相似文献
22.
Shah S. Levine M.D. 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》1996,26(2):259-274
At the retinal level, the strategies utilized by biological visual systems allow them to outperform machine vision systems, serving to motivate the design of electronic or "smart" sensors based on similar principles. Design of such sensors in silicon first requires a model of retinal information processing which captures the essential features exhibited by biological retinas. In this paper, a simple retinal model is presented, which qualitatively accounts for the achromatic information processing in the primate cone system. The computer retina model exhibits many of the properties found in biological retinas such as data reduction through nonuniform sampling, adaptation to a large dynamic range of illumination levels, variation of visual acuity with illumination level, and enhancement of spatiotemporal contrast information. The main emphasis of the model presented here is to demonstrate how different adaptation mechanisms play a role in extending the operating range of the primate retina. 相似文献
23.
Anthony E. Okorodudu Leonidas Fegaras David Levine 《Universal Access in the Information Society》2011,10(2):207-216
There has been a great interest in publish/subscribe systems in recent years. This interest, coupled with the pervasiveness
of light-weight electronic devices, such as cellular phones and personal digital assistants, has opened a new arena in publish/subscribe
networks. Currently, many broker overlay networks are static and rarely change in structure. Often, a network overlay structure
is predefined or manually modified. This paper presents a dynamic broker network for disseminating critical lab and patient
information in a Healthcare information system. The reported work builds upon previous network optimization research on ad
hoc publish/subscribe networks. The underlying framework utilizes user-defined cost functions to satisfy quality of service
constraints. In essence, the broker network optimization problem is reduced to an incremental search problem to generate low
cost network configurations. Certain reliability issues are also addressed by providing a scheduling algorithm to selectively
retransmit information and handle broker connectivity failures. 相似文献
24.
How Internet software companies negotiate quality 总被引:1,自引:0,他引:1
In Internet speed development, innovation and time-to-market work against software quality. Browser giants like Microsoft Internet Explorer and Netscape Navigator are openly dealing with quality issues. The practices of application and smaller niche firms are less clear, but there are important trends 相似文献
25.
DA Danford BM McManus SM Nielsen MG Levine HW Needelman 《Canadian Metallurgical Quarterly》1993,14(4):242-246
Correlative echocardiographic and pathological findings in a thoracopagus with conjoined hearts are reported. One twin had tricuspid atresia with discordant atrioventricular connections and concordant ventriculoarterial connections. The morphologic right ventricle was hypoplastic and there was a large muscular ventricular septal defect. The other twin had hypoplasia of the mitral valve anulus and left ventricle with double-outlet right ventricle and pulmonary valve atresia. The tricuspid valve was severely insufficient in part because of a large orifice and redundant, elongated leaflets with abnormal chordal attachments. The left ventricles of these two twins shared a perforated common "free wall" with at least two large defects allowing mixing of the circulations at that level. Not all anatomic details were established conclusively by fetal echocardiography; however, sufficient diagnostic information was obtained to support a decision not to aggressively resuscitate these twins after elective cesarean delivery at 31 weeks' gestation. 相似文献
26.
This paper presents a novel approach for action recognition, localization and video matching based on a hierarchical codebook model of local spatio-temporal video volumes. Given a single example of an activity as a query video, the proposed method finds similar videos to the query in a target video dataset. The method is based on the bag of video words (BOV) representation and does not require prior knowledge about actions, background subtraction, motion estimation or tracking. It is also robust to spatial and temporal scale changes, as well as some deformations. The hierarchical algorithm codes a video as a compact set of spatio-temporal volumes, while considering their spatio-temporal compositions in order to account for spatial and temporal contextual information. This hierarchy is achieved by first constructing a codebook of spatio-temporal video volumes. Then a large contextual volume containing many spatio-temporal volumes (ensemble of volumes) is considered. These ensembles are used to construct a probabilistic model of video volumes and their spatio-temporal compositions. The algorithm was applied to three available video datasets for action recognition with different complexities (KTH, Weizmann, and MSR II) and the results were superior to other approaches, especially in the case of a single training example and cross-dataset1 action recognition. 相似文献
27.
Questions C. G. Watson's (see PA, Vol 52:Issue 3) attempt to explain apparent inconsistencies in findings between his and the present authors' studies in terms of sample differences. Despite Watson's reanalysis of his data by matched pairs, he fails adequately to control for differences in chronicity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
Recent research suggests that approximately one third of the population of homeless single adults suffer from severe mental illnesses. Despite multiple health, mental health, and social welfare needs, this population is often unable to obtain necessary housing and community-based services. For this reason, since 1982, the National Institute of Mental Health (NIMH) has undertaken a number of federal initiatives to encourage research and assist states and localities in improving services focused on this vulnerable subgroup of the homeless population. This article describes the target population, NIMH research findings, and current mental health programs—with particular emphasis on two mental health programs established under the Stewart B. McKinney Homeless Assistance Act. Proposed future directions for federal research and evaluation efforts in this area are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
30.