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   994篇
  免费   18篇
  国内免费   3篇
综合类   2篇
化学工业   60篇
金属工艺   5篇
机械仪表   4篇
建筑科学   9篇
能源动力   4篇
轻工业   32篇
水利工程   2篇
石油天然气   8篇
无线电   10篇
一般工业技术   44篇
冶金工业   807篇
原子能技术   3篇
自动化技术   25篇
  2024年   3篇
  2022年   5篇
  2021年   13篇
  2020年   6篇
  2019年   6篇
  2018年   10篇
  2017年   13篇
  2016年   7篇
  2015年   5篇
  2014年   5篇
  2013年   15篇
  2012年   11篇
  2011年   14篇
  2010年   12篇
  2009年   8篇
  2008年   13篇
  2007年   11篇
  2006年   6篇
  2005年   5篇
  2004年   4篇
  2003年   12篇
  2002年   10篇
  2001年   5篇
  2000年   6篇
  1999年   22篇
  1998年   270篇
  1997年   158篇
  1996年   89篇
  1995年   48篇
  1994年   35篇
  1993年   50篇
  1992年   4篇
  1991年   6篇
  1990年   6篇
  1989年   9篇
  1988年   5篇
  1986年   4篇
  1985年   3篇
  1983年   2篇
  1982年   2篇
  1981年   6篇
  1980年   5篇
  1978年   1篇
  1977年   30篇
  1976年   55篇
排序方式: 共有1015条查询结果,搜索用时 15 毫秒
61.
In this study the potential of cloud point extraction formed by a non-ionic surfactant was used in order to separate polyphenols from industrial residues of camu-camu. The effects of operational conditions of the cloud point extraction (CPE) on the polyphenol recovery and volumetric ratio were investigated. The results showed a maximum recovery of 95.71% that was obtained using 7.0 wt% Triton X-114, native pH (3.25), and 80 wt% polyphenol extract at 30 °C. The use of cloud point extraction was successful to recover the polyphenols from agroindustrial residue since it is a simple as well as of low-cost technique.  相似文献   
62.
63.
64.
Abstract

A previous recurrence formula using the resonant atom-field interaction for the generation of a field state in a cavity is extended to arbitrary states having even and odd numbers of photons in their photon-number distribution.  相似文献   
65.
Collagen-induced arthritis (CIA) is a T cell-dependent disease in which susceptibility is controlled by genes both within and outside the major histocompatibility complex (MHC). In the present study, we compared the humoral responses and kinetics of cytokine secretion patterns in the draining lymph nodes of arthritis-susceptible DA rats and arthritis-resistant F344 and DA MHC congenic PVG.1AV1 rats immunized with rat type II collagen (RCII) in incomplete Freund's adjuvant. The results demonstrate a marked humoral RCII response and a Th1 cytokine profile, with expression of interferon-gamma and interleukin (IL)-2 mRNA in DA rats; a limited humoral RCII response and a Th2 cytokine profile, with expression of IL-4 mRNA in arthritis-resistant F344 rats; and a marked humoral RCII response in arthritis-resistant PVG.1AV1 rats. However, in contrast to DA rats, PVG.1AV1 rats produce IgG1 autoantibodies which, together with strong expression of IL-4 mRNA, indicates the involvement of Th2 subsets. From these data, we conclude that non-MHC gene(s) determines the direction of the anti-RCII response towards a Th1 disease-promoting, or a Th2 disease-limiting response.  相似文献   
66.
67.
The sympathetic nervous system plays a role in the regulation of thyroid function. In FRTL-5 rat thyroid cells, norepinephrine (NE) acutely depresses intracellular I- by increasing I- efflux. The present study was undertaken to determine the effect of NE on iodide transport after a longer time period. NE inhibited the ability of thyrotropin (TSH) to induce iodide uptake by FRTL-5 cells after 48 or 72 hours, but not after 24 hours. The effect of NE was more evident with increasing concentrations of TSH. NE did not modify the rate of I- efflux. Inhibition was associated with a decrease in the Vmax and no change in the Km for iodide influx. To determine if this was a generalized effect of NE on thyroid cell membrane, the uptake of alpha-aminoisobutyric acid (a nonmetabolizable aminoacid) and of 2-deoxyglucose was measured. NE did not inhibit TSH stimulation of the uptake of the two compounds. NE inhibited the action of dibutyryl cAMP (dbcAMP) on iodide uptake in a similar manner to TSH, but did not alter the cyclic adenosine monophosphate (cAMP) levels increased by TSH. The effects of different adrenoreceptor agonists and antagonists demonstrated that norepinephrine acts through an alpha1-adrenergic receptor.  相似文献   
68.
LA Smith  DE Barker  CW Chase  LB Somberg  WB Brock  RP Burns 《Canadian Metallurgical Quarterly》1997,63(12):1102-7; discussion 1107-8
The purpose of this review is to present a 4-year experience with the vacuum pack technique of temporary abdominal closure. From April 1992 to December 1996, 171 vacuum packs were performed on 93 patients. Eighty-seven vacuum packs were performed on 38 general surgical patients, and 84 vacuum packs were performed on 55 trauma patients. Overall hospital mortality was 32 per cent. Methods of achieving permanent wound closure varied in 73 patients. Four patients (4.3%) developed enterocutaneous fistulae; four patients developed intra-abdominal abscesses (4.3%). There were no eviscerations. Management of the complicated intra-abdominal process is discussed: 1) the decision to manage the abdomen in an open fashion; 2) which method of temporary closure to use; 3) subsequent explorations; 4) when the abdomen should be closed; 5) which type of closure to use; and 6) when the abdominal wall should be revised (herniorrhaphy). The vacuum pack is the method of choice for open abdomen management and temporary abdominal closure at our institution. With careful subsequent management, good patient outcome can be achieved.  相似文献   
69.
70.
BACKGROUND: Investigations concerning the severity of respiratory syncytial virus (RSV) disease as related to (1) RSV type and genotype determined respectively by PCR and restriction enzyme analysis and (2) interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) values in samples of nasopharyngeal secretion (NPS) have not been previously reported. METHODS: We prospectively studied 105 RSV infections in the lower respiratory tract of infants and young children admitted to a pediatric department in Copenhagen during three winter seasons, 1993, 1994 and 1995. RSV strains were typed and genotyped, respectively, by PCR and nucleic acid restriction analysis and correlated to the severity of the disease. The ratio IL-6:TNF-alpha, determined from IL-6- and TNF-alpha values in samples of NPS, was related to the severity of the disease. Concentrations of IL-6 and of TNF-alpha were determined in serum samples taken during 5 weeks after the onset of illness. RESULTS: Type B infections produced more severe disease than did type A infections, as assessed on the length of the hospital stay, use of respiratory support and the presence of an infiltrate on a chest radiograph. This difference was age-related. It was observed in infants 0 to 5 months old, but not in older age groups. Type B genotype B1122 produced more severe disease than type A genotype A2311 in infants 0 to 11 months old. Increased serum concentrations of IL-6 and TNF-alpha were detected in samples taken 1 to 2 days after the onset of illness. Whereas TNF-alpha serum concentrations remained high, IL-6 serum concentrations decreased during the following 3 to 4 weeks. The IL-6:TNF-alpha ratio in samples of NPS was related to the severity of the disease. A high ratio was related to a low severity. CONCLUSIONS: The severity of disease in patients admitted with acute RSV infections can be correlated to the RSV type as determined by PCR, to the RSV genotype as determined by nucleic acid restriction analysis and to the ratio IL-6:TNF-alpha in NPS.  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