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   2303篇
  免费   2篇
电工技术   4篇
化学工业   38篇
金属工艺   4篇
机械仪表   5篇
建筑科学   10篇
矿业工程   2篇
能源动力   6篇
轻工业   22篇
石油天然气   1篇
无线电   21篇
一般工业技术   28篇
冶金工业   2127篇
原子能技术   1篇
自动化技术   36篇
  2023年   2篇
  2022年   3篇
  2019年   2篇
  2017年   1篇
  2016年   2篇
  2015年   2篇
  2014年   4篇
  2013年   4篇
  2012年   2篇
  2011年   8篇
  2010年   4篇
  2009年   6篇
  2008年   7篇
  2007年   10篇
  2006年   6篇
  2005年   6篇
  2004年   3篇
  2003年   10篇
  2002年   4篇
  2001年   6篇
  2000年   5篇
  1999年   59篇
  1998年   627篇
  1997年   417篇
  1996年   266篇
  1995年   155篇
  1994年   120篇
  1993年   135篇
  1992年   16篇
  1991年   29篇
  1990年   19篇
  1989年   21篇
  1988年   37篇
  1987年   28篇
  1986年   18篇
  1985年   15篇
  1984年   1篇
  1983年   3篇
  1982年   10篇
  1981年   16篇
  1980年   17篇
  1979年   7篇
  1978年   6篇
  1977年   50篇
  1976年   119篇
  1975年   2篇
  1974年   2篇
  1973年   4篇
  1970年   4篇
  1969年   2篇
排序方式: 共有2305条查询结果,搜索用时 15 毫秒
71.
72.
We report four cases of multiple symmetric lipomatosis in the Chinese population. We believe that multiple symmetric lipomatosis in the Chinese is not uncommon and may be related to the increasing incidence of alcoholism. The ultrasound appearances of these lipomatous masses are presented for the first time. Heterogeneous echogenic masses with fine fibrous strands that insinuate around fascial planes, lymph nodes and vascular tissues are typical findings. Unlike diseases affecting the Western population, multiple symmetric lipomatosis in the Chinese appears to be limited to the head and neck.  相似文献   
73.
74.
75.
A 23-year-old patient suffered from episodic angioedema of the face and neck, accompanied by diarrhea and abdominal pain. Additionally, the patient had bronchial asthma, recurrent nasal polyps and allergic rhinoconjunctivitis. Blood examination revealed leucocytosis with eosinophilia. Histological studies showed eosinophilic infiltrates in the skin and the gastrointestinal mucosa. Allergic food reactions and parasites were ruled out. With systemic corticosteroid treatment, the clinical symptoms and the eosinophilia disappeared. This case shows some parallels to previously described syndromes (eosinophilic gastroenteritis, Samter's syndrome, episodic angioedema with eosinophilia), but to the best of our knowledge this combination of symptoms has not yet been reported.  相似文献   
76.
OBJECTIVE: To describe a case of Leydig cell tumor of the testis, discuss the criteria for determining its benign or malignant nature and the clinical features according to patient age and the hormone profile. METHODS/RESULTS: Scrotal US evaluation for an associated pathology incidentally detected a hypoechoic, homogeneous mass with preserved borders. Biological testicular tumor markers were determined and the suspicion of a Leydig cell tumor prompted a hormone study. The diagnosis of Leydig cell tumor was confirmed by intraoperative biopsy and radical orchidectomy was performed. CONCLUSION: In the case described, the ultrasound findings prompted the etiological diagnosis given the characteristics of the lesion. The definitive diagnosis was based on the pathological findings. Although classified as benign Leydig cell tumor, radical orchidectomy is advocated.  相似文献   
77.
The type V transforming growth factor beta (TGF-beta) is a 400-kDa nonproteoglycan membrane protein that co-expresses with the type I, type II, and type III TGF-beta receptors in most cell types. The type V TGF-beta receptor exhibits a Ser/Thr-specific protein kinase activity with distinct substrate specificity (Liu, Q., Huang, S. S., and Huang, J. (1994) J. Biol. Chem. 269, 9221-9226). In mink lung epithelial cells, the type V TGF-beta receptor was found to form heterocomplexes with the type I TGF-beta receptor by immunoprecipitation with antiserum to the type V TGF-beta receptor after 125I-TGF-beta affinity labeling or Trans35S-label metabolic labeling of the cells. The kinase activity of the type V TGF-beta receptor was stimulated after treatment of mink lung epithelial cells with TGF-beta. TGF-beta stimulation resulted in the growth inhibition of wild-type mink lung epithelial cells and to a lesser extent of the type I and type II TGF-beta receptor-defective mutants, although higher concentrations of TGF-beta were required for the growth inhibition of these mutants. TGF-beta was unable to induce growth inhibition in human colorectal carcinoma cells lacking the type V TGF-beta receptor but expressing the type I and type II TGF-beta receptors. These results suggest that the type V TGF-beta receptor can mediate the TGF-beta-induced growth inhibitory response in the absence of the type I or type II TGF-beta receptor. These results also support the hypothesis that loss of the type V TGF-beta receptor may contribute to the malignancy of certain carcinoma cells.  相似文献   
78.
Transforming growth factor beta-1 (TGF-beta1) is a potent inhibitor of hepatocyte growth both in vivo and in vitro. In this study, we analyzed the effects of TGF-beta1 on both naturally occurring and diethylnitrosamine-induced hepatocarcinogenesis using single transgenic TGF-beta1 and double transgenic c-myc/TGF-beta1 mice in which the expression of both transgenes was targeted to the liver. Hepatocellular tumors developed spontaneously in 59% (10 of 17) of the TGF-beta1 mice by 16-18 months of age. Coexpression of TGF-beta1 and c-myc transgenes in the liver accelerated hepatic tumor growth in both the presence and absence of carcinogenic treatment. Moreover, diethylnitrosamine-initiated tumors in the c-myc/TGF-beta1 mice showed a high rate of malignant conversion associated with a reduced expression or lack of TGF-beta receptor type II. The results suggest that overexpression of TGF-beta1 may contribute to liver carcinogenesis and that loss of TGF-beta receptor type II transduced inhibitory growth signals and up-regulation of c-myc are critical steps in liver tumor progression.  相似文献   
79.
80.
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