全文获取类型
收费全文 | 2171篇 |
免费 | 181篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 83篇 |
妇产科学 | 49篇 |
基础医学 | 243篇 |
口腔科学 | 59篇 |
临床医学 | 293篇 |
内科学 | 423篇 |
皮肤病学 | 35篇 |
神经病学 | 65篇 |
特种医学 | 434篇 |
外科学 | 292篇 |
综合类 | 69篇 |
一般理论 | 4篇 |
预防医学 | 112篇 |
眼科学 | 23篇 |
药学 | 92篇 |
1篇 | |
中国医学 | 1篇 |
肿瘤学 | 63篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 19篇 |
2018年 | 29篇 |
2017年 | 28篇 |
2016年 | 33篇 |
2015年 | 38篇 |
2014年 | 55篇 |
2013年 | 61篇 |
2012年 | 53篇 |
2011年 | 62篇 |
2010年 | 68篇 |
2009年 | 75篇 |
2008年 | 62篇 |
2007年 | 85篇 |
2006年 | 55篇 |
2005年 | 68篇 |
2004年 | 51篇 |
2003年 | 57篇 |
2002年 | 37篇 |
2001年 | 55篇 |
2000年 | 43篇 |
1999年 | 40篇 |
1998年 | 87篇 |
1997年 | 87篇 |
1996年 | 91篇 |
1995年 | 74篇 |
1994年 | 45篇 |
1993年 | 63篇 |
1992年 | 27篇 |
1991年 | 32篇 |
1990年 | 39篇 |
1989年 | 74篇 |
1988年 | 60篇 |
1987年 | 64篇 |
1986年 | 63篇 |
1985年 | 85篇 |
1984年 | 44篇 |
1983年 | 35篇 |
1982年 | 36篇 |
1981年 | 34篇 |
1980年 | 44篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 27篇 |
1976年 | 29篇 |
1975年 | 27篇 |
1974年 | 8篇 |
排序方式: 共有2356条查询结果,搜索用时 62 毫秒
31.
Characterization of RAFTK, a novel focal adhesion kinase, and its integrin-dependent phosphorylation and activation in megakaryocytes 总被引:19,自引:3,他引:16
We have recently isolated a cDNA encoding a novel human intracellular tyrosine kinase, termed RAFTK (for a related adhesion focal tyrosine kinase). The RAFTK cDNA, which encodes a polypeptide of 1,009 amino acids, shares 65% homology to the focal adhesion kinase (FAK), including several consensus motifs. In this report, we describe the biochemical characterization and functional analysis of the RAFTK protein. Coexpression of RAFTK and FAK proteins in megakaryocytic cells and blood platelets was observed. Using a specific antibody to RAFTK and the monoclonal antibody 2A7 to FAK, FAK and RAFTK could be distinguished antigenically. RAFTK had intrinsic tyrosine kinase and autokinase activities. It was phosphorylated on tyrosine in growing cultures of COS cells transfected with the pCDNAIII/flag-RAFTK expression vector containing the RAFTK cDNA ligated with the 8 amino acid flag peptide sequence. Similar to FAK, dephosphorylation of RAFTK was observed when adherent transfected COS cells were detached. Phosphorylation was regained upon replating of these cells on the fibronectincoated dishes. Analysis of tyrosine-phosphorylated RAFTK from adherent transfected COS cells showed that the Src homology 2 (SH2) domains of the Src and Fyn protein kinases as well as the Grb2 adaptor protein were able to specifically associate with RAFTK. Tyrosine phosphorylation of endogenous RAFTK was observed upon fibronectin-induced activation of human megakaryocytic cells. Furthermore, colocalization of RAFTK protein with vinculin, a focal adhesion protein, was observed by confocal microscopy in focal adhesion- like structures in adherent CMK cells and in transfected pCDNAIII/flag- RAFTK COS cells upon fibronectin activation. These data suggest that RAFTK is a novel member of the FAK family, that it localizes to focal adhesion-like structures in CMK megakaryocytic cells, that it participates in integrinmediated signaling pathways in megakaryocytes, and that it is able to associate with the tyrosine kinases Src and Fyn as well as the adaptor protein Grb2 via SH2-phosphotyrosine interactions. 相似文献
32.
Studies of proteins that inhibit tissue factor activity have generally been conducted using either an extracted tissue homogenate ("thromboplastin") or tissue factor protein reconstituted into phospholipid vesicles rather than with tissue factor expressed in cell membranes (its physiological environment). In the present study, a human fibroblast cell strain was used to evaluate the effects of lipoprotein associated coagulation inhibitor (LACI), placental anticoagulant protein (PAP), and apolipoprotein A-II (apo A-II) on human tissue factor in cell membranes. LACI was tested from 7.8 to 500 pmol/L on fibroblasts cultured at cell densities ranging from 3,500 to 9,925 cells/well, and caused a progressive inhibition of tissue factor activity. PAP was tested from 3.9 nmol/L to 1 mumol/L at cell densities ranging from 4,500 to 15,400 cells/well and caused up to 83% inhibition of tissue factor activity. Inhibition by these proteins appeared to be influenced by cell density as well as whether the cells were intact or disrupted. Apo A-II, up to 1 mumol/L, did not inhibit the tissue factor activity of intact or disrupted fibroblasts at any cell density examined even though it did inhibit the activity of tissue factor in phospholipid vesicles. Of these inhibitors of tissue factor-dependent activation of factor X, LACI was the most effective in suppressing the generation of factor Xa activity. The effects obtained with apo A-II are clearly dependent on the nature of the tissue factor preparation with which it is tested. The disparity between the inhibitory effect of apo A-II on the activity of tissue factor reconstituted into lipid vesicles and the absence of effect on the activity of tissue factor remaining in cell membranes serves to reemphasize the necessity of reexamining results obtained with model systems using as nearly physiological reagents as possible. 相似文献
33.
34.
35.
36.
37.
The reliability of prealbumin as a diagnostic marker was studied in 60 cases of bronchopulmonary carcinoid tumours. There were differences in the incidence of positivity between typical and atypical carcinoids (well differentiated neuroendocrine carcinomas). Seventy five per cent of the carcinoid tumours were positive for prealbumin; (86.7% typical and 63.3% atypical carcinoids). In 15 cases, which were Grimelius negative, 10 were prealbumin positive. Only 8.3% carcinoids were negative with both prealbumin and Grimelius stains. Ten squamous, 10 adeno- and 10 small cell carcinomas showed only occasional scattered prealbumin positive cells. It is concluded that prealbumin is a useful marker for bronchopulmonary carcinoid tumours. It is cheap, readily available, and should be considered part of routine diagnostic procedures for the diagnosis of carcinoid tumours. 相似文献
38.
Anderson RA; Wallace AM; Kicman AT; Wu FC 《Human reproduction (Oxford, England)》1997,12(8):1657-1662
Administration of supraphysiological doses of testosterone to normal men
causes inhibition of spermatogenesis, but while most become azoospermic,
30-55% maintain a low rate of spermatogenesis. We have investigated whether
there are differences in endogenous androgen production, of testicular and
adrenal origin, which may be related to the degree of suppression of
spermatogenesis. Thirty-three healthy Caucasian men were given weekly i.m.
injections of 200 mg testosterone oenanthate (TE), 18 became azoospermic,
while 15 remained oligozoospermic. Urinary excretion of epitestosterone, a
specific testicular product, was reduced to <10% of pretreatment values,
with no differences between the groups. Similar results were obtained for
other markers of testicular steroidogenesis. Urinary and plasma adrenal
androgens were also reduced during TE treatment: a statistically
significant decrease in both (P < 0.001 and P < 0.05 respectively)
was seen in the azoospermic but not oligozoospermic responders. These
results suggest that testicular steroidogenesis is decreased to <10% by
the administration of supraphysiological doses of exogenous testosterone.
Differences in the degree of ongoing steroidogenesis in the testis do not
appear to account for incomplete suppression of spermatogenesis, thus
differences in androgen metabolism may underlie this heterogeneous
response. A small but significant reduction in secretion of adrenal
androgens was also detectable, the relevance of which is unclear.
相似文献
39.
40.
RA Kumar 《Clinical genetics》2008,74(4):343-344
De novo mutations in the gene encoding STXBP1 (MUNC18‐1) cause early infantile epileptic encephalopathySaitsu et al. (2008)Nature Genetics 40: 782–788 相似文献