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   1211篇
  免费   3篇
  国内免费   1篇
电工技术   2篇
化学工业   7篇
金属工艺   2篇
建筑科学   1篇
能源动力   1篇
轻工业   2篇
无线电   6篇
一般工业技术   5篇
冶金工业   1183篇
原子能技术   1篇
自动化技术   5篇
  2021年   1篇
  2018年   1篇
  2017年   2篇
  2016年   1篇
  2014年   2篇
  2012年   1篇
  2011年   2篇
  2009年   1篇
  2007年   1篇
  2006年   2篇
  2005年   1篇
  2003年   5篇
  2002年   1篇
  1999年   44篇
  1998年   341篇
  1997年   204篇
  1996年   142篇
  1995年   58篇
  1994年   59篇
  1993年   73篇
  1992年   12篇
  1991年   15篇
  1990年   22篇
  1989年   20篇
  1988年   21篇
  1987年   20篇
  1986年   20篇
  1985年   8篇
  1983年   4篇
  1982年   3篇
  1981年   4篇
  1980年   9篇
  1979年   1篇
  1978年   4篇
  1977年   32篇
  1976年   66篇
  1975年   5篇
  1973年   1篇
  1972年   1篇
  1968年   1篇
  1967年   3篇
  1966年   1篇
排序方式: 共有1215条查询结果,搜索用时 427 毫秒
101.
102.
The coexistence of infrarenal aortic aneurysm and internal iliac artery aneurysm may represent a management problem with regard to preservation of the pelvic blood supply. In this article, we review the methods available for maintaining the pelvic blood flow and describe a useful technique that we have successfully utilized in seven patients to preserve the hypogastric artery blood flow.  相似文献   
103.
104.
105.
106.
107.
The metabolic effects during myocardial ischemia and sustained reperfusion of the antianginal agents diltiazem (n = 10) and propranolol (n = 10) were monitored with noninvasive phosphorus nuclear magnetic resonance spectroscopy to establish any correlation between metabolic changes and infarct size. Spectroscopy followed changes in high-energy phosphate concentrations and myocardial intracellular pH during 2 h of left anterior descending coronary artery occlusion and 3 subsequent weeks of reperfusion, in a closed chest canine infarct model. Gadolinium-DTPA enhanced magnetic resonance imaging was used to assess the extent of myocardial injury (infarct size). Microspheres were used to document the zone at risk and the success of reperfusion. Whereas diltiazem appeared to reduce the derangement in high-energy phosphates during coronary occlusion, there was no significant change in infarct size when compared with a previously studied control group. Propranolol, which produced a lesser decline in pH during occlusion and smaller pH changes during early reperfusion, was associated with a significant reduction in the degree of tissue necrosis (compared with controls). There was an inverse correlation (r = -0.51) between the change in myocardial pH (occlusion end to immediate reperfusion) and the recovery index (an index of myocardial salvage). By 1 h into reperfusion, there was a stronger inverse correlation between pH and infarct size (r = -0.75), implying a protective effect of delaying pH recovery during early reperfusion and indicating the potential use of this parameter as a predictor of tissue viability.  相似文献   
108.
The histologic diagnosis of adult renal epithelial neoplasms with prominent eosinophilic cytoplasm (renal oncocytoma, chromophobe renal-cell carcinoma (RCC), eosinophilic variant of clear-cell RCC, eosinophilic variant of papillary RCC, and collecting duct carcinoma), could be problematic in some cases because of overlapping morphologic features. Precise diagnosis is essential, however, because it often connotes a distinct biologic behavior. Proliferative activity has not been specifically investigated in this spectrum of renal tumors, so we studied the MIB-1 proliferation index in 20 renal oncocytomas, 12 chromophobe RCCs, 9 eosinophilic variants of papillary RCCs, and 13 eosinophilic variants of clear-cell RCCs. Our purpose was to identify the biologic potential of these renal tumors on the basis of MIB-1 tumor proliferation index and to ascertain whether that index had diagnostic value. Overall, nuclear grade correlated with MIB-1 tumor proliferation index (P=.03). The mean proliferation index progressively increased from renal oncocytomas (0.3) to chromophobe RCCs (0.8) to eosinophilic variants of papillary RCCs (2.2) to eosinophilic variants of clear-cell RCCs (4.1) (P=.002). None of the renal oncocytomas or chromophobe RCCs had an index greater than 2, whereas 8 of 13 eosinophilic variants of clear-cell RCCs had an index greater than 2; in 5 of these, it was more than 3. Thus, in the differential diagnosis between renal oncocytoma/chromophobe RCC and eosinophilic variant of RCC, an MIB-1 index of greater than 3 with appropriate morphologic correlation would strongly support the diagnosis of the latter. We also concluded that the progressive increase in MIB-1 tumor proliferation index across the spectrum of granular renal-cell neoplasms parallels the emerging data in the current literature concerning the biologic potential of adult renal epithelial tumors and justifies histologic categorization of adult renal epithelial neoplasms.  相似文献   
109.
Factors that influence colony morphology are of crucial importance for drug development as well as for understanding the virulence of Mycobacterium avium complex (MAC) strains. The MAC 101 strain used in the present study grows as smooth transparent (SmT) colonies that tend to become opaque and pigmented when incubated for long periods of time. However, when MAC was passaged in animals, two types of colonies were recovered. The new rough transparent (RgT) colony morphology appeared more flat and transparent, having a central spot, irregular edges at times, and a dry, granular appearance like that of the rough mutants. In animal studies, the RgT bacilli multiplied at a much faster rate than that of the SmT bacilli, causing 60-80% mortality compared with the 10% mortality observed in mice infected with SmT. In vitro studies indicated that the SmT MAC did not grow and multiply as well in resident peritoneal macrophages as the RgT MAC did. The two morphotypes did not differ in their growth ratesin vitro but the RgT MAC failed to reduce dimethylthiazol-diphenyltetrazolium bromide (MTT), alamar blue and neutral red, suggesting that there might be significant changes in the cell wall or elsewhere causing changes in cellular permeability. These two morphotypes could serve as models for studying the biochemical markers or the identification of factors responsible for the virulence of the MAC.  相似文献   
110.
N-Phthaloyl 3-amino-3-arylpropionic acid analogs of thalidomide that are potent inhibitors of tumor necrosis factor-alpha are reported. These compounds were found to be potent inhibitors of phosphodiesterase 4.  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