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   479篇
  免费   0篇
  国内免费   2篇
化学工业   4篇
机械仪表   4篇
轻工业   11篇
无线电   1篇
一般工业技术   1篇
冶金工业   456篇
自动化技术   4篇
  2022年   1篇
  2019年   1篇
  2014年   2篇
  2012年   1篇
  2011年   1篇
  2010年   1篇
  2008年   2篇
  2007年   2篇
  2006年   1篇
  2004年   2篇
  2003年   4篇
  1999年   13篇
  1998年   155篇
  1997年   89篇
  1996年   55篇
  1995年   19篇
  1994年   19篇
  1993年   24篇
  1992年   3篇
  1991年   9篇
  1990年   5篇
  1989年   4篇
  1988年   8篇
  1987年   5篇
  1986年   3篇
  1985年   6篇
  1984年   1篇
  1982年   4篇
  1981年   2篇
  1980年   4篇
  1979年   1篇
  1977年   9篇
  1976年   24篇
  1955年   1篇
排序方式: 共有481条查询结果,搜索用时 15 毫秒
101.
Deregulation of expression of the cell cycle regulator cyclin D1 (cD1) may be responsible for rapid proliferation of squamous cell carcinoma of the head and neck (SCCHN). We have studied the expression of cD1 in 46 SCCHNs using immunohistochemistry. Before biopsy, the patients received an in vivo infusion of iododeoxyuridine (IdUrd) for cell proliferation assessment. Additionally, the level of apoptosis was estimated using in situ end labeling (ISEL). Among 33 tumors, the proportion of cD1(+) cells varied from 0.5 to 51.3% (19.9 +/- 2.2%). Thirteen tumors did not express cD1. The fraction of S-phase (IdUrd-positive) cells was 26.3 +/- 1.8% in cD1(+) versus 20.0 +/- 2.4% in cD1(-) tumors (P = 0.06). The percentages of cD1(+) cells and of S-phase cells were not correlated (P = 0.37). Apoptosis was detected by ISEL in 15 of 33 tumors studied. ISEL-positive tumors contained a significantly higher proportion of cD1(+) cells (14.9 +/- 2.6%) than cD1(-) ones (7.9 +/- 2.8%; P = 0.03). There was a positive correlation between the percentage of cD1(+) cells and the degree of ISEL (r = 0.54; P < 0.001). In noninvolved oral mucosa, cD1(+) cells were located primarily in the suprabasal layers (29.3 +/- 3.8% versus 1.2 +/- 0. 2% in the basal layer). Only 23 of 44 mucosal specimens contained cD1(+) cells. All cD1(-) samples were proliferatively active and contained IdUrd-labeled cells. The percentage of cD1(+) cells in the oral epithelium from nontumor controls (uvula samples) was significantly higher than in the SCCHN group in both basal (2.4 +/- 0.4%; P = 0.008) and suprabasal (42.7 +/- 3.3%; P = 0.005) layers. Additionally, whereas in uvuli, cD1(+) cells were distributed evenly along the epithelial lining, in SCCHN samples the regions showing cD1 expression alternated with areas in which cD1 expression was undetectable. These data indicate that cD1 expression in SCCHN varies among tumors and is not correlated with cell proliferation. In noninvolved oral mucosa, cD1 expression differs from that in truly normal epithelium obtained from nontumor patients. A correlation between cD1 expression and the extent of ISEL positivity suggests a possible involvement of cD1 expression in the apoptotic pathways.  相似文献   
102.
OBJECTIVES: This study sought to examine the effects of long-term estrogen therapy on vascular function in male to female transsexuals and to compare the findings with those observed in men and premenopausal women. BACKGROUND: Gender differences in coronary artery disease have largely been attributed to the beneficial effects of estrogen on vascular function and plasma lipids in women. However, the effects of estrogen on the male vasculature have not been widely studied. METHODS: We compared the effects of estrogen on vascular function in 14 male to female transsexuals, 14 age-matched men and 15 premenopausal women. Flow-mediated vasodilation and response to nitroglycerin were assessed in the brachial artery using noninvasive ultrasound. RESULTS: Flow-mediated vasodilation was similar in transsexuals and women but greater than that in men ([mean +/- SE] 11.5 +/- 1.3% and 9.4 +/- 1.1% vs. 5.2 +/- 1.0% respectively, p < 0.005). Responses to nitroglycerin were also greater in transsexuals and women than in men (21.6 +/- 1.7% and 21.0 +/- 0.9% vs. 14.5 +/- 1.2%, respectively, p = 0.0005). These differences persisted even after adjusting for vessel size. Despite similar total cholesterol levels, transsexuals had high density lipoprotein cholesterol levels similar to those in women and greater than those observed in men (1.76 +/- 0.12 and 1.82 +/- 0.11 mmol/liter vs. 1.35 +/- 0.07 mmol/liter, respectively, p < 0.005). Moreover, triglyceride levels were greater in transsexuals than in men and women, and low density lipoprotein cholesterol (LDL-C) particle size was smaller (25.7 +/- 0.2 nm vs. 26.2 +/- 0.1 and 26.6 +/- 0.1 nm, respectively, p = 0.0001). Serum testosterone (an index of estrogen therapy in transsexuals) was markedly suppressed in transsexuals and similar to that in women. Univariate analysis revealed that there was a strong inverse correlation between serum testosterone and flow-mediated vasodilation (r(s) = -0.48, p < 0.005). Multivariate analysis revealed that the best combination of predictors of flow-mediated vasodilation was serum testosterone, vessel size and LDL-C (R2 = 0.3, p < 0.005). CONCLUSIONS: Long-term estrogen therapy appears to improve vascular function in male to female transsexuals and occurs despite higher triglyceride levels and the presence of small, dense LDL-C. The beneficial effects of estrogen are not gender specific or solely mediated through endothelium-derived nitric oxide.  相似文献   
103.
104.
105.
106.
107.
We studied retrospectively 22 children who were managed for splenic injuries at Jos University Teaching Hospital between September 1988 and October 1995. Sixteen were males and six were females (M:F = 2.7:1) with their ages between five and 15 years and a mean of 10.3 years. Eleven were knocked down by vehicles while crossing the freeway, playing or hawking goods; seven fell from slippery mango trees after a downpour of rain while two were passengers in a vehicle that was involved in a head-on collision and another two were kicked in the abdomen as a result of assault. All had surgery. Four sustained Uphadhyaya and Simpson's Type 1 injuries while six sustained Type IV injuries. Twelve had total splenectomy, seven had total splenectomy with heterotopic autotransplantation of splenic wafers while three had splenorrhaphy augmented with omentoplasty. An average of 1.5 units of blood per patient were transfused. There was only one death. Considering that the majority (18) of these children sustained their splenic injuries while crossing the freeway (playing or hawking goods) and from falls from mango trees after the rains, we believe that there are preventable causes. Mandatory primary and junior secondary school education as well as legislature against child labour will help keep these children safe out of harm's way and thus drastically reduce the incidence of childhood splenic injuries in our environment.  相似文献   
108.
The 349-amino-acid major core protein VP7 of bluetongue virus (BTV) is both the most abundant viral structural protein and the major immunogenic serogroup-reactive viral antigen. Previous studies indicated that a conformation-dependent antigenic site, defined by the VP7-specific monoclonal antibody 20E9/B7/G2(20E9), was accessible from the virus surface and that the binding of the monoclonal antibody to this epitope could be blocked specifically by antisera raised against different serotypes of bluetongue virus, suggesting it is a serogroup-specific immunodominant epitope. Using a combination of three different mapping strategies, we have located the 20E9 binding site at the N-terminus of the molecule, between amino acids 30 and 48. The fine mapping of the 20E9 immunodominant epitope will facilitate structure-function analyses of the major core protein and provide new opportunities to improve existing BTV serodiagnosis methods based on this immunogenic site.  相似文献   
109.
Nurses who are searching for new positions can enhance their job employment potential with well-written resumes. Scholarship and award recognition also can be improved by creating well-written resumes and/or curricula vitae. Appropriate cover letters effectively introduce nurses to employers or review committees. This article presents a few basic suggestions that can simplify the creation of any of these documents and help nurses produce a quality product.  相似文献   
110.
A cDNA encoding a putative bovine intercellular adhesion molecule (ICAM)-3, a ligand of the leukocyte integrin LFA-1 (CD11a/CD18), was sequenced and compared with human ICAM sequences. The 1635-bp bovine sequence codes for a protein of 544 amino acids (aa). This putative bovine ICAM-3 has five immunoglobulin (Ig)-like domains similar to human ICAM-1 and ICAM-3, and belongs to the Ig gene superfamily. The overall identities of the deduced aa sequence with those of human ICAM-3 and ICAM-1 are 61% and 58%, respectively. The predicted number and positions of Cys residues are all conserved between the bovine and human ICAM 3 aa sequences.  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