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   209篇
  免费   4篇
电工技术   3篇
化学工业   22篇
金属工艺   1篇
机械仪表   1篇
建筑科学   3篇
能源动力   5篇
轻工业   7篇
水利工程   4篇
无线电   19篇
一般工业技术   24篇
冶金工业   89篇
原子能技术   2篇
自动化技术   33篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   1篇
  2018年   1篇
  2017年   1篇
  2016年   3篇
  2015年   4篇
  2014年   2篇
  2013年   9篇
  2012年   9篇
  2011年   10篇
  2010年   2篇
  2009年   7篇
  2008年   5篇
  2007年   11篇
  2006年   6篇
  2005年   5篇
  2004年   2篇
  2003年   2篇
  2002年   3篇
  2001年   2篇
  2000年   2篇
  1999年   4篇
  1998年   28篇
  1997年   19篇
  1996年   12篇
  1995年   8篇
  1994年   5篇
  1993年   5篇
  1992年   2篇
  1991年   3篇
  1989年   3篇
  1988年   2篇
  1986年   3篇
  1985年   5篇
  1984年   7篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1977年   1篇
  1976年   4篇
  1975年   1篇
  1971年   1篇
排序方式: 共有213条查询结果,搜索用时 125 毫秒
21.
Increased circulating levels of hepatotoxic bile acids may contribute to the cholestasis characteristic of cystic fibrosis-related liver disease. The aims of this study were to compare serum bile acid profiles in patients with cystic fibrosis with and without liver disease, and to evaluate the effect of treatment with ursodeoxycholic acid, a non-hepatotoxic bile acid, on liver biochemistry and serum bile acids in patients with cystic fibrosis-related liver disease. Fasting and postprandial serum bile acid levels were analysed in 15 patients (nine males; median age 18 years) with cystic fibrosis-related liver disease and compared with serum bile acid levels in 18 cystic fibrosis patients (12 males; median age 22 years) without liver disease and 10 control subjects. Fasting and postprandial serum levels of primary and secondary serum bile acids were analysed using high-performance liquid chromatography. Liver biochemistry and serum bile acids were measured in six cystic fibrosis patients with liver disease before and 6 months after treatment with ursodeoxycholic acid 20 mg/kg/day and compared with six control patients with cystic fibrosis-related liver disease. Total fasting and postprandial serum bile acid levels were significantly (P < 0.01) elevated in patients with liver disease compared to those without liver disease and controls. The fasting glycine conjugates of cholic acid, chenodeoxycholic acid and deoxycholic acid, and the fasting and postprandial taurine conjugates of cholic acid and chenodeoxycholic acid were significantly (P < 0.05) elevated in liver disease patients compared to patients without liver disease and controls. After 6 months' treatment with ursodeoxycholic acid, although the serum was significantly saturated with ursodeoxycholic acid and significant improvements in liver biochemistry were observed in the treatment group, there was no significant reduction in the levels of individual serum bile acids. Although circulating levels of potentially hepatotoxic serum bile acids are elevated in patients with cystic fibrosis-related liver disease, improvements in liver biochemistry associated with ursodeoxycholic acid treatment cannot be attributed solely to alterations in levels of endogenous bile acids.  相似文献   
22.
The effects of the indolehallucinogen psilocybin, a mixed 5-HT2 and 5-HT1 agonist, on regional cerebral glucose metabolism were investigated in 10 healthy volunteers with PET and [F-18]-fluorodeoxyglucose (FDG) prior to and following a 15- or 20-mg dose of psilocybin. Psychotomimetic doses of psilocybin were found to produce a global increase in cerebral metabolic rate of glucose (CMRglu) with significant and most marked increases in the frontomedial and frontolateral cortex (24.3%), anterior cingulate (24.9%), and temporomedial cortex (25.3%). Somewhat smaller increases of CMRglu were found in the basal ganglia (18.5%), and the smallest increases were found in the sensorimotor (14.7%) and occipital cortex (14.4%). The increases of CMRglu in the prefrontal cortex, anterior cingulate, temporomedial cortex, and putamen correlated positively with psychotic symptom formation, in particular with hallucinatory ego disintegration. The present data suggest that excessive 5-HT2 receptor activation results in a hyperfrontal metablic pattern that parallels comparable metabolic findings associated with acute psychotic episodes in chronic schizophrenics and contrasts with the hypofrontality in chronic schizophrenic patients.  相似文献   
23.
This paper presents a number of case histories illustrating the benefits and costs of certain types of engineering measurement and testing, with a focus on strain‐gauged land‐based structures. The benefits are described mainly in terms of safety, economy and environment. The costs are related to the amount of data collected and processed. The paper concludes with some technical and financial guidance for clients, owners, consultants and contractors who may be considering these types of activities.  相似文献   
24.
PURPOSE: To determine whether treatment with an autologous whole-cell vaccine modified with the hapten dinitrophenyl (DNP vaccine) is an effective postsurgical adjuvant treatment for melanoma patients with clinically evident nodal metastases. PATIENTS AND METHODS: Eligible patients had regional nodal metastases that were large enough (> or = 3 cm diameter) to prepare vaccine. Following standard lymphadenectomy, patients were treated with DNP vaccine on a monthly or weekly schedule. RESULTS: Of 62 patients with metastasis in a single lymph node bed (stage III), 36 are alive after a median follow-up time of 55 months (range, 29 to 76); the projected 5-year relapse-free and overall survival rates are 45% and 58%, respectively. Of 15 patients with metastases in two nodal sites, five are alive with a median follow-up time of 73 months. An unexpected finding was the significantly better survival of older patients; the projected 5-year survival of patients greater than 50 versus < or = 50 years was 71% and 47%, respectively (P = .011, log-rank test). The development of a positive delayed-type hypersensitivity (DTH) response to unmodified autologous melanoma cells was associated with significantly longer 5-year survival (71% v 49%; P = .031). Finally, the median survival time from date of first recurrence was significantly longer for patients whose subcutaneous recurrence exhibited an inflammatory response (> 19.4 v 5.9 months; P < .001). CONCLUSION: Postsurgical adjuvant therapy with autologous DNP-modified vaccine appears to produce survival rates that are markedly higher than have been reported with surgery alone. Moreover, this approach has some intriguing immunobiologic features that might provide insights into the human tumor-host relationship.  相似文献   
25.
The gene content of the MHC class I telomerically adjacent region, in linkage disequilibrium with hereditary hemochromatosis, has not been well characterized yet. In the present work, we established three bacterial clone contigs, including mainly P1-derived artificial chromosomes. These contigs cover 89% of the 1.2-Mb 6p-subtelomeric region encompassing locus D6S105. Terminal exon trapping was applied to selected clones from these contigs. Forty-six independent terminal exons were identified and mapped within the region, 2 of which matched perfectly to expressed sequence tags. These 3' exons are all expressed in human fetal brain but differentially expressed in four tissues and two cell lines. The high number of exons identified indicates that the high gene density observed in the MHC class I region extends to this telomerically adjacent region.  相似文献   
26.
27.
At the University of Regina in Saskatchewan, an on-going R & D program, within the Mathesis Group is developing a computer assisted learning system for visually-handicapped University students. The program has grown around use of a speech synthesizer (a relatively-inexpensive, older Votrax unit was available), to provide, initially, a convenient and flexible audio toolfor blind persons tackling BASIC programming assignments. This CAL program has progressed through several stages: convenient Braille flowcharting was developed to assist programming analysis, the synthesized speech support component has evolved from micro-to minicomputer hardware, and now a convenient spelling/dictionary feature is being employed for the writing of essays.  相似文献   
28.
29.
Place cells, navigational accuracy, and the human hippocampus   总被引:1,自引:0,他引:1  
The hippocampal formation in both rats and humans is involved in spatial navigation. In the rat, cells coding for places, directions, and speed of movement have been recorded from the hippocampus proper and/or the neighbouring subicular complex. Place fields of a group of the hippocampal pyramidal cells cover the surface of an environment but do not appear to do so in any systematic fashion. That is, there is no topographical relation between the anatomical location of the cells within the hippocampus and the place fields of these cells in an environment. Recent work shows that place cells are responding to the summation of two or more Gaussian curves, each of which is fixed at a given distance to two or more walls in the environment. The walls themselves are probably identified by their allocentric direction relative to the rat and this information may be provided by the head direction cells. The right human hippocampus retains its role in spatial mapping as demonstrated by its activation during accurate navigation in imagined and virtual reality environments. In addition, it may have taken on wider memory functions, perhaps by the incorporation of a linear time tag which allows for the storage of the times of visits to particular locations. This extended system would serve as the basis for a spatio-temporal event or episodic memory system.  相似文献   
30.
Gene transfer to retinal cells may provide a means to retard photoreceptor cell death and thus prevent blindness in diseases such as retinitis pigmentosa. We tested the possibility of interfering with apoptotic photoreceptor cell death in the rd mouse through subretinal delivery of a recombinant replication-defective adenovirus containing the human cDNA for bcl-2, Ad.2.5HRPbcl-2. Photoreceptor-specific transgene expression was accomplished through incorporation of the 2.5 kb human rhodopsin upstream fragment (HRP). Ad.2.5HRPbcl-2 was injected alone or in combination with Ad.CMVPDE beta. Ad.CMVPDE beta contains a cDNA encoding the beta subunit of cGMP phosphodiesterase (PDE beta). Recombinant viruses containing lacZ (driven either by the cytomegalovirus (CMV) promoter/enhancer or HRP) and of Ad.CMVPDE beta and vehicle alone were injected in contralateral eyes as control. Injection of Ad.2.5HRPbcl-2 in the rd mouse resulted in histologically detectable rescue lasting 6 weeks after birth. Extent of rescue was not as large as after delivery of wildtype PDE beta, the gene defective in the rd mouse. However, delivery of genes which prevent apoptotic cell death may have broad application to gene therapy of retinal degenerative diseases.  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