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   1008篇
  免费   9篇
电工技术   1篇
化学工业   26篇
金属工艺   4篇
机械仪表   11篇
建筑科学   5篇
能源动力   1篇
轻工业   10篇
水利工程   1篇
无线电   53篇
一般工业技术   54篇
冶金工业   828篇
原子能技术   3篇
自动化技术   20篇
  2021年   2篇
  2020年   3篇
  2019年   4篇
  2018年   6篇
  2017年   3篇
  2016年   5篇
  2014年   6篇
  2013年   9篇
  2012年   5篇
  2011年   8篇
  2010年   9篇
  2009年   10篇
  2008年   15篇
  2007年   11篇
  2006年   11篇
  2005年   12篇
  2004年   2篇
  2003年   5篇
  2002年   8篇
  2001年   9篇
  2000年   3篇
  1999年   31篇
  1998年   265篇
  1997年   134篇
  1996年   89篇
  1995年   58篇
  1994年   60篇
  1993年   55篇
  1992年   3篇
  1991年   8篇
  1990年   6篇
  1989年   5篇
  1988年   8篇
  1987年   9篇
  1986年   12篇
  1985年   6篇
  1984年   3篇
  1983年   3篇
  1982年   4篇
  1981年   3篇
  1980年   10篇
  1978年   1篇
  1977年   24篇
  1976年   61篇
  1975年   2篇
  1973年   1篇
  1971年   2篇
  1966年   1篇
  1960年   1篇
  1955年   3篇
排序方式: 共有1017条查询结果,搜索用时 31 毫秒
91.
Human herpesvirus 8 (HHV-8) DNA sequences were examined in peripheral blood mononuclear cell (PBMC) DNA samples of 56 children, 15 healthy adults, and 10 renal transplant patients by the polymerase chain reaction (PCR). The PCR amplification was carried out using the published KS330(233) primer pairs to amplify HHV-8 DNA sequences. The PCR-amplified products were confirmed by Southern blot hybridization with radiolabeled 233 bp HHV-8 DNA fragment, which was cloned and sequenced from the PCR-amplified product of Kaposi's sarcoma tissue. Six PCR-amplified product of four children and two renal transplant patients were cloned and sequenced. HHV-8 DNA sequences were detected in 36 of 56 (64%) normal children, in 12 of 15 (80%) healthy adults, and in all 10 renal transplant patients by Southern blot hybridization of PCR-amplified products. Six PCR-amplified products were confirmed by sequencing. These results suggest that HHV-8 infection is prevalent in the Japanese population with infection occurring in early childhood.  相似文献   
92.
The ribonucleoprotein (RNP) enzyme telomerase is required for replication of eukaryotic chromosomal termini. The RNA moiety of telomerase is essential for enzyme function and provides the template for telomeric DNA synthesis. However, the roles of its nontemplate domains have not been explored. Here we demonstrate that a novel interspecies telomerase RNA swap in vivo creates a functional but aberrant telomerase. Telomerase RNA from the ciliate Glaucoma chattoni was expressed in Tetrahymena thermophila cells. The telomerase RNAs from these two species have almost superimposable secondary structures. The template region base sequence is identical in the two RNAs, but elsewhere their sequences differ by 49%. This hybrid telomerase RNP was enzymatically active but added only short stretches of telomeric repeat tracts in vivo and in vitro. This new enzyme also had a strong, aberrant DNA cleavage activity in vitro. Thus, molecular interactions in the RNP involving nontemplate RNA domains affect specific aspects of telomerase enzyme function, raising the possibility that they may regulate telomerase activity.  相似文献   
93.
94.
95.
The dual-wall zirconia induction furnace consists of an inner susceptor tube and an outer insulation tube. The centre piece of the inner tube is coated with a thin silica film. The performance of the newly designed furnace was evaluated in terms of the strength of drawn fibres. The proof test of 47 km length of fibre demonstrated superb strength results, yielding the average survival length at 1·4 GN/m2 (200 klb in?2) to be ~8 km.  相似文献   
96.
97.
Recent developments in video camera technology, new instruments, and advanced surgical techniques have increased the importance of video-assisted thoracoscopic surgery (VATS). Currently, VATS offers a new approach in the diagnosis and treatment of many thoracic conditions previously treated only by standard thoracotomy. In our experience, VATS is a safe, reliable, and effective alternative to thoracic surgery. With further improvements and refinements in video imaging and endoscopic instruments, more procedures will be technically feasible. The long-term results of VATS compared to open thoracotomy will require extensive follow up and prospective trials to determine its true value.  相似文献   
98.
OBJECTIVE: The role of a deficiency of vitamin B1 in the development of alcoholic complaints is confined to the case of the Wernicke-Korsakov syndrome. Findings concerning a deficiency of thiamine in alcoholics in comparison with normal persons are contradictory and there are no differentiated tests in the case of delirium tremens. In this study the vitamin B1 absorption in patients with delirium tremens was of interest in connection with the presence or absence of hallucinations and autonomic symptoms. METHOD: Male patients (N = 70) with delirium tremens were compared with a group of 13 controls. The controls and patients were hospitalized in order to ensure abstinence from alcohol. The examination of the delirium patients was carried out with their consent after termination of the delirium tremens and again on discontinuance of drug therapy. In the case of 33 delirium patients the absorption of thiamine was tested again 4 weeks after the first examination. RESULTS: The absorption of vitamin B1 was in general only minimally lower in the case of the delirium patients in comparison with the nonalcoholics. The results showed, however, a considerably greater range of scattering of vitamin B1 absorption in the delirium patients. The absorption conditions showed marked improvement in the 4 weeks after delirium. The extent of absorption of vitamin B1 showed no influence on the duration of delirium. The patients with visual hallucinations, however, showed lower thiamine absorption than patients without such symptoms, whereas no dependence of autonomic symptoms on vitamin B1 absorption was seen. CONCLUSIONS: The disturbed absorption conditions in the delirium patients were obvious at the time of the examination as demonstrated by the wide range of absorption values. Improvement or near normal conditions were registered 4 weeks after the delirium. The absorption conditions had possibly already improved during the few days of alcohol abstinence in the course of the delirium treatment. The reduced vitamin B1 absorption of patients suffering from visual hallucination corresponds to observations of alcoholic hallucinosis.  相似文献   
99.
The purpose of this study was to examine differences in the way Britain and the United States invest in and deploy a new medical technology. We used structured interviews to obtain information on the technical sophistication and approximate replacement value of all hospital-based obstetrical ultrasound machines in every maternity hospital in Washington state and Wales. The supply of hospital-based ultrasound machines--approximately two machines per 1,000 births--was similar in both countries. Wales had fewer advanced ultrasound machines than Washington state, and they were based exclusively in high-volume district general hospitals; there were no obstetric ultrasound machines in the private sector. In Washington state, the majority of advanced machines were in small and medium-sized hospitals, and many private offices had ultrasound machines. The approximate replacement value of hospital-based machines was three times as high per birth in Washington state as in Wales. In the case of obstetrical ultrasound, centralization of facilities, a relatively small private sector, and global budgeting lead to lower expenditures per patient within the National Health Service without compromising access to care.  相似文献   
100.
Dot-immunoblotting assay (DIA) using five monoclonal antibodies (MAbs) to infectious bronchitis virus (IBV) was used to detect and classify the viruses propagated in embryonated chicken eggs. Using a group-specific MAb 3F5, 10 reference strains and 12 Korean isolates of IBV were successfully detected by DIA, and the lowest virus titer of IBV detected by DIA was approximately less than 10(3.8) mean embryo infective dose/ml. For evaluating the diagnostic efficiency, DIA was compared with the conventional infectious bronchitis (IB) diagnostic method. IBV antigens in allantoic fluid from embryonated eggs inoculated with IB-suspected field samples were specifically detected by DIA within only one or two egg passages, whereas the conventional embryonated egg inoculation method required four to seven egg passages for confirming IBV infection. These results indicated that DIA could significantly reduce time and cost for IB diagnosis. For examining the possibility of classifying IBV by DIA, four strain-specific MAbs, 3A4, 2A3, 6F7, and 2C6, were used. According to the MAb reacting patterns to the IBV antigens, the 10 IBV reference strains were classified into six groups; seven strains belonged to three different groups, and the other three strains each belonged to an individual group. In the case of 12 Korean isolates of IBV, they were classified in six groups. Among the six groups, the MAb reacting patterns of three groups matched those of the IBV reference strains, but the others did not. These data suggest that at least three variant serotypes of IBV exist in Korea.  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