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   1852篇
  免费   1篇
  国内免费   1篇
电工技术   1篇
化学工业   19篇
金属工艺   1篇
建筑科学   3篇
矿业工程   1篇
轻工业   5篇
无线电   6篇
一般工业技术   2篇
冶金工业   1806篇
自动化技术   10篇
  2020年   2篇
  2019年   3篇
  2018年   2篇
  2017年   1篇
  2014年   1篇
  2013年   2篇
  2012年   1篇
  2011年   2篇
  2010年   1篇
  2009年   3篇
  2008年   2篇
  2007年   4篇
  2006年   2篇
  2005年   5篇
  2004年   4篇
  2003年   6篇
  2001年   2篇
  2000年   1篇
  1999年   50篇
  1998年   597篇
  1997年   314篇
  1996年   224篇
  1995年   102篇
  1994年   93篇
  1993年   103篇
  1992年   11篇
  1991年   21篇
  1990年   23篇
  1989年   36篇
  1988年   28篇
  1987年   17篇
  1986年   24篇
  1985年   32篇
  1983年   2篇
  1982年   5篇
  1981年   4篇
  1980年   15篇
  1978年   2篇
  1977年   33篇
  1976年   67篇
  1975年   3篇
  1972年   1篇
  1955年   3篇
排序方式: 共有1854条查询结果,搜索用时 15 毫秒
51.
52.
We describe a female stillbirth with duplication of 3q21-->qter and deletion of 11q23-->qter resulting from an unbalanced segregation of a maternal t(3;11) reciprocal translocation. The proband had some of the clinical features consistent with those seen in patients with dup(3q) syndrome or distal del(11q) syndrome. Prenatal sonographic examination showed short limbs, intrauterine growth retardation, and an omphalocele containing the liver.  相似文献   
53.
54.
55.
OBJECTIVE: Our objective was to compare intravascular sonography with digital subtraction angiography (DSA) in the assessment of luminal dimension and morphologic features of endovascular stents and stent grafts. MATERIALS AND METHODS: Thirty-seven pelvic and 24 femoral stents (12 Wall-stents; 27 covered and 22 uncovered nitinol stents) in 50 patients were evaluated 15 +/- 10 months after implantation by DSA and intravascular sonography. The degree of maximum instent restenosis as revealed by DSA and intravascular sonography was compared for each location. Morphologic features of the stents and stenoses were also assessed. RESULTS: Intravascular sonography and DSA correlated well (R2 = .96) in determining in-stent restenosis. In-stent restenosis was underestimated by 13% +/- 6% by DSA compared with intravascular sonography. Differences in determining in-stent restenosis with intravascular sonography and DSA were not associated with severity of stenosis or type of stent. Intravascular sonography revealed incomplete expansion of stents in 21 cases, whereas DSA revealed incomplete expansion of stents in seven cases. The intra- and interobserver variabilities in our study were 4% and 5%, respectively. CONCLUSION: In-stent restenoses are underestimated with DSA. Intravascular sonography is superior to DSA for detection of incomplete stent expansion.  相似文献   
56.
57.
When exposed to diverse growth conditions in vitro, cells can respond by entering states of proliferation, quiescence, differentiation or apoptosis. While the choices among these states can be influenced by proto-oncogene expression, how these disparate outcomes are achieved remains poorly understood. To address these issues, we have generated rodent fibroblast cell lines that harbor a human c-myc gene under the control of a tetracycline-regulated promoter. When Myc-induced cells are deprived of serum growth factors, they rapidly become apoptotic with the onset of apoptosis preceded by a large, transient increase in cdk2 kinase activity that is associated with the induction of cdc25A phosphatase and the later accumulation of p27Kip1 kinase inhibitor. Surprisingly, serum starvation in the absence of myc overexpression, (which leads to quiescence instead of apoptosis) also causes a marked transient elevation in cdk2 kinase activity, an induction of cdc25A and a delayed increase in p27Kip1. Transient elevations in cdk2 kinase activity and cdc25A abundance are required for cell cycle progression, but it is evident that these changes also precede entry to either apoptosis or quiescence in serum-starved cells. These findings suggest that the pathways to both quiescence and apoptosis share regulatory machinery with cell cycle control mechanisms. In addition, the abundance of Myc protein can be critical in the choices among these cellular states.  相似文献   
58.
59.
We report a case of oesophageal disease as the first manifestation in a patient with CREST syndrome. A 46-year-old man with achalasia-like syndrome developed CREST syndrome 4 years later. A pneumatic dilatation of the cardia was performed. After pneumatic dilatation the dysphagia and regurgitation disappeared but the patient developed reflux oesophagitis. Four years after diagnosis of oesophageal disease he presented with a clinical picture of CREST syndrome. An acute ileus and constipation developed later. After receiving medical therapy with omeprazole and cisapride the patient is free of oesophageal symptoms and bowel movements are normal. Oesophageal disease is common in patients with limited and diffuse scleroderma, but to our knowledge achalasia-like syndrome has not been previously described as the first manifestation of the systemic disease.  相似文献   
60.
Prophylactic treatment with Bacillus Calmette-Guerin (BCG) is an established and effective therapy of bladder cancer. The antitumor effect of BCG seems to be largely related to cellular immunological mechanisms, although its precise mode of action is unknown. Antitumor response of BCG seems to be initiated by the attachment of BCG to bladder wall via Fibronectin (FN). The cellular immune response against Tuberculin PPD and the major secreted BCG antigen (Fibronectin-binding AG 85 complex) has been tested in a control group of 20 untreated bladder tumor patients and before and after 6 weekly intravesical BCG instillations in a group of 20 superficial bladder tumor patients. A major increase in the lymphoproliferative response against PPD and AG 85 was observed in respectively 66% and 57% of the treated patients. In contrast, no detectable antibody response (IgA, IgM, IgG) was observed against AG 85 complex after BCG treatment. On the other hand, antibodies against Tuberculin increased in 13 of 20 patients. This study seems to demonstrate a specific cellular immune activation against AG 85 Fibronectin-binding complex during BCG treatment of superficial bladder tumors. Humoral response against the AG 85 is not activated after BCG treatment. Further studies are needed to elucidate the role of AG 85 in the cellular intravesical penetration of BCG. Presence or absence of cellular response against this antigen could be of clinical value.  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