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   3133篇
  免费   34篇
  国内免费   14篇
电工技术   41篇
综合类   28篇
化学工业   58篇
金属工艺   4篇
机械仪表   104篇
建筑科学   15篇
矿业工程   6篇
能源动力   6篇
轻工业   355篇
水利工程   2篇
无线电   15篇
一般工业技术   97篇
冶金工业   2325篇
原子能技术   3篇
自动化技术   122篇
  2022年   17篇
  2020年   18篇
  2019年   30篇
  2018年   5篇
  2014年   6篇
  2013年   155篇
  2012年   31篇
  2011年   23篇
  2010年   31篇
  2009年   28篇
  2008年   30篇
  2007年   34篇
  2006年   22篇
  2005年   24篇
  2004年   24篇
  2003年   22篇
  2002年   16篇
  2001年   4篇
  2000年   10篇
  1999年   81篇
  1998年   757篇
  1997年   435篇
  1996年   287篇
  1995年   156篇
  1994年   126篇
  1993年   150篇
  1992年   26篇
  1991年   31篇
  1990年   41篇
  1989年   40篇
  1988年   39篇
  1987年   54篇
  1986年   38篇
  1985年   38篇
  1984年   10篇
  1983年   6篇
  1982年   13篇
  1981年   22篇
  1980年   19篇
  1979年   8篇
  1978年   5篇
  1977年   60篇
  1976年   125篇
  1975年   6篇
  1974年   3篇
  1973年   5篇
  1969年   5篇
  1958年   4篇
  1955年   18篇
  1954年   16篇
排序方式: 共有3181条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
995.
996.
Radiofrequency (RF) energy has many advantages in thermal tumor ablation protocols. With the recent development of open MRI systems, interventional MRI procedures, including thermal ablation, have become the focus of great research interest. However, the significant interference between RF generators and MR imagers has prevented simultaneous imaging and RF ablation and, until now, has limited the role of RF-based thermal therapy in interventional MRI. Here, a simple switching circuit designed with consideration of patient safety provides compatibility between open MRI systems and RF thermal lesion generators. The experimental results show that the switching circuit allows imaging during RF ablation and opens new opportunity for MR-guided thermal therapy.  相似文献   
997.
OBJECTIVE: To determine the relationship of serum theophylline concentration with electrolyte and glucose abnormalities across a broad range of theophylline concentrations. DESIGN: Retrospective review of a computerized laboratory database between June 1, 1984 and June 1, 1986. SETTING: A midwestern university medical center. PATIENTS: Eight hundred sixty-nine patients with serum theophylline concentrations of > 5.5 mumol/L and a random unmatched sample (control group) of 350 in- and outpatient adults and children with no history of reactive airways disease or theophylline exposure. RESULTS: Patients with measurable theophylline had a higher risk of hypokalemia, hyponatremia, hyperglycemia, hypophosphatemia, and hypomagnesemia compared with the unexposed control group. Unadjusted odds ratios (OR) were: (1) hypokalemia OR = 4.2 (95 percent CI 2.2 to 7.9); (2) hyponatremia OR = 5.4 (95 percent CI 2.0 to 12.9); (3) hypomagnesemia OR = 1.6 (95 percent CI 1.0 to 2.5); (4) hyperglycemia OR = 2.3 (95 percent CI 1.7 to 3.0); and (5) hypophosphatemia OR = 2.7 (95 percent CI 1.2 to 5.3). A linear concentration-response relationship was documented between serum theophylline concentration and all metabolic disturbances. CONCLUSIONS: Measurable theophylline was associated with increased risk for glucose and electrolyte abnormalities in a concentration-related fashion across a broad range of theophylline concentrations from 5.5 to > or = 110 mumol/L.  相似文献   
998.
It was recently reported that Streptococcus iniae, a bacterial pathogen of aquatic animals, can cause serious disease in humans. Using the chaperonin 60 (Cpn60) gene identification method with reverse checkerboard hybridization and chemiluminescent detection, we identified correctly each of 12 S. iniae samples among 34 aerobic gram-positive isolates from animal and clinical human sources.  相似文献   
999.
1000.
The Hrp (type III protein secretion) system is essential for the plant parasitic ability of Pseudomonas syringae and most Gram-negative bacterial plant pathogens. AvrB and AvrPto are two P. syringae proteins that have biological activity when produced via heterologous gene expression inside plant cells or when produced by Hrp+ bacteria. Avr-like proteins, presumably injected by the Hrp system on bacterial contact with plant cells, appear to underlie pathogenic interactions, but none has been observed outside of the bacterial cytoplasm, and identifying novel genes encoding them is tedious and uncertain without a phenotype in culture. Here we describe a cloned Hrp secretion system that functions heterologously in Escherichia coli to secrete AvrB and AvrPto in culture and to promote AvrB and AvrPto biological activity in inoculated plants. The hrp gene cluster, carried on cosmid pCPP2156, was cloned from Erwinia chrysanthemi, a pathogen that differs from P. syringae in being host promiscuous. E. coli DH5alpha carrying pCPP2156, but not related Hrp-deficient cosmids, elicited a hypersensitive response in Nicotiana clevelandii only when also expressing avrB in trans. The use of pAVRB-FLAG2 and pAVRPTO-FLAG, which produce Avr proteins with a C-terminal FLAG-epitope fusion, enabled immunoblot detection of the secretion of these proteins to E. coli(pCPP2156) culture media. Secretion was Hrp dependent, occurred without leakage of a cytoplasmic marker, and did not occur with E. coli(pHIR11), which encodes a functional P. syringae Hrp system. E. coli(pCPP2156) will promote investigation of Avr protein secretion and systematic prospecting for the effector proteins underlying bacterial plant pathogenicity.  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