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   2001篇
  免费   266篇
  国内免费   1篇
  2021年   20篇
  2020年   16篇
  2019年   19篇
  2018年   20篇
  2017年   24篇
  2016年   31篇
  2015年   56篇
  2014年   47篇
  2013年   83篇
  2012年   92篇
  2011年   78篇
  2010年   71篇
  2009年   59篇
  2008年   66篇
  2007年   75篇
  2006年   71篇
  2005年   69篇
  2004年   71篇
  2003年   64篇
  2002年   79篇
  2001年   60篇
  2000年   67篇
  1999年   61篇
  1998年   37篇
  1997年   34篇
  1996年   22篇
  1995年   28篇
  1994年   20篇
  1993年   30篇
  1992年   48篇
  1991年   46篇
  1990年   44篇
  1989年   41篇
  1988年   38篇
  1987年   41篇
  1986年   46篇
  1985年   28篇
  1984年   21篇
  1983年   27篇
  1982年   23篇
  1981年   26篇
  1980年   24篇
  1979年   36篇
  1978年   17篇
  1977年   20篇
  1975年   28篇
  1974年   25篇
  1973年   27篇
  1971年   18篇
  1970年   20篇
排序方式: 共有2268条查询结果,搜索用时 15 毫秒
961.
Lysinuric protein intolerance (LPI) is a recessively inherited amino acid disorder characterized by defective efflux of cationic amino acids at the basolateral membrane of the intestinal and renal tubular epithelium. Recently, cDNAs encoding the related proteins hCAT-2A and hCAT-2B have been cloned. These two carrier proteins are most likely the product of the same gene, hCAT-2. Using the hCAT-2B cDNA, we assigned the hCAT-2 gene to chromosome 8p22. Furthermore, by linkage analysis in Finnish LPI families, we ruled out that hCAT-2B is involved in LPI disease. Received: 28 October 1996 / Accepted: 20 January 1997  相似文献   
962.
963.
964.
Echovirus 1 interaction with the isolated VLA-2 I domain.   总被引:2,自引:2,他引:0       下载免费PDF全文
The isolated I domain of the integrin VLA-2, produced as a bacterial fusion protein, specifically bound echovirus 1 and prevented virus attachment to cells. These results demonstrate that the receptor structures critical for virus attachment are contained solely within the VLA-2 I domain and that soluble receptor fragments are capable of preventing infection.  相似文献   
965.
966.
The present work provides the first information concerning the chemoattractant activity of trout recombinant IL-1beta and its derived peptides, referred to as P1, P2 and P3. The predicted rainbow trout mature interleukin-1beta peptide was produced as a recombinant protein in Escherichia coli. The first peptide, P1, corresponded to fragment 146-157 (YVTPVPIETEAR) of the trout sequence and had an MW of 137 kDa. It was equivalent to a region known to be part of the receptor binding domain from the mammalian crystal structure of IL-1beta complexed to its receptor. P2 was used as control peptide, consisting of the same 12 amino acids as P1, but arranged in a random sequence (VVEEYIRAPPTT). P3 was synthesised to complex with an adjacent region of the IL-1 receptor, and corresponded to fragment 207-216 (YRRNTGVDIS) of the trout sequence, with an MW of 1.18 kDa. Migration was stimulated when leucocytes were exposed to concentrations of > or = 10 ng ml(-1) rIL-1beta. Peptide P3 also induced leucocyte migration, with an optimal dose of 0.25 mM being recorded. While P1 had no effect on cell migration when used alone, synergism was evident as a consequence of combining P1 with a suboptimal dose (0.01 mM) of P3. No synergism occurred when cells were exposed to a combination of P3 and the control peptide P2.  相似文献   
967.
Coexistent cardiovascular disease is common in patients presenting for repair of aortic aneurysms. However, preoperative cardiac evaluation prior to abdominal aortic aneurysm (AAA) surgery remains contentious with significant variations in practice between countries, institutions and individual anesthetists. The following case report raises some everyday issues confronting clinical anesthetists.  相似文献   
968.
Isolation of a new foamy retrovirus from orangutans.   总被引:8,自引:4,他引:4       下载免费PDF全文
We have isolated a new foamy virus from blood samples taken from two apparently healthy orangutans (Pongo pygmaeus). The older orangutan has since died with encephalopathy after a brief acute illness, while the younger one, his grandson, remains well. These animals and 12 other orangutans had specific antibodies to foamy virus as measured by immunofluorescence. The new foamy virus and the antisera showed strong and specific neutralization, with only weak cross-reaction with other simian foamy virus strains. Southern blotting with gag and env probes of human foamy virus and PCR amplification showed that the new foamy virus, designated SFV-11, is related to, yet distinct from, previously characterized strains from humans, chimpanzees, and monkeys.  相似文献   
969.
OBJECTIVE--To characterise clinical, investigative, and prognostic features of women referred with chest pain who subsequently underwent coronary angiography. DESIGN--Analysis of all women with angina referred to one consultant during 1987-91 who subsequently underwent coronary angiography, with follow up to present day. SETTING--Cardiothoracic centre. SUBJECTS--Women with normal coronary arteries; women with coronary artery disease shown on angiography; men with coronary artery disease matched for age; men referred with chest pain during the same period subsequently found to have normal coronary arteries. MAIN OUTCOME MEASURES--Risk factor analysis; results of exercise testing and coronary angiography; intervention; morbidity and mortality. RESULTS--Women comprised 23% (202/886) of patients referred with chest pain who subsequently underwent angiography. 83/202 women had normal coronary angiograms compared with 55/684 men (41% v 8%, P < 0.01). Diabetes mellitus was the only risk factor more frequently encountered in women with coronary artery disease (P = 0.001). The specificity and positive predictive value of exercise testing before angiography were significantly lower in women than men (71% v 93%, P < 0.001 and 76% v 95%, P < 0.001, respectively). Revascularisation procedures were as common in women with coronary artery disease as in men (81 (68%) v 70 (59%)), and there was no difference in event rate during follow up. Many patients with normal coronary arteries, irrespective of sex, had symptoms during follow up (61 (73%) women, 36 (65%) men) and continued to take antianginal drugs (27 (33%) women, 14 (28%) men); 14 (17%) women and six (11%) men required hospital readmission for severe symptoms. CONCLUSIONS--In this series, although women comprised the minority of patients referred with chest pain, a diagnosis of normal coronary arteries was five times more common in women than men. Risk factor analysis and exercise testing were of limited value in predicting coronary artery disease in women. There was no sex bias regarding revascularisation procedures, and outcome was similar. A diagnosis of non-cardiac chest pain in patients with normal coronary arteries was of little benefit to the patient with regard to morbidity.  相似文献   
970.
Three species of the family Enterobacteriaceae that biochemically reduced hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were isolated from nitramine explosive-contaminated soil. Two isolates, identified as Morganella morganii and Providencia rettgeri, completely transformed both RDX and the nitroso-RDX reduction intermediates. The third isolate, identified as Citrobacter freundii, partially transformed RDX and generated high concentrations of nitroso-RDX intermediates. All three isolates produced 14CO2 from labeled RDX under O2-depleted culture conditions. While all three isolates transformed HMX, only M. morganii transformed HMX in the presence of RDX.  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