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   18153篇
  免费   980篇
  国内免费   168篇
耳鼻咽喉   228篇
儿科学   359篇
妇产科学   383篇
基础医学   2124篇
口腔科学   657篇
临床医学   1397篇
内科学   4687篇
皮肤病学   224篇
神经病学   2112篇
特种医学   680篇
外科学   2985篇
综合类   47篇
一般理论   2篇
预防医学   694篇
眼科学   278篇
药学   993篇
中国医学   17篇
肿瘤学   1434篇
  2024年   14篇
  2023年   195篇
  2022年   466篇
  2021年   719篇
  2020年   421篇
  2019年   583篇
  2018年   637篇
  2017年   480篇
  2016年   535篇
  2015年   598篇
  2014年   784篇
  2013年   1040篇
  2012年   1480篇
  2011年   1541篇
  2010年   813篇
  2009年   780篇
  2008年   1130篇
  2007年   1131篇
  2006年   980篇
  2005年   962篇
  2004年   938篇
  2003年   728篇
  2002年   686篇
  2001年   128篇
  2000年   93篇
  1999年   111篇
  1998年   143篇
  1997年   132篇
  1996年   105篇
  1995年   87篇
  1994年   76篇
  1993年   59篇
  1992年   65篇
  1991年   74篇
  1990年   70篇
  1989年   57篇
  1988年   35篇
  1987年   36篇
  1986年   36篇
  1985年   25篇
  1984年   38篇
  1983年   35篇
  1982年   37篇
  1981年   20篇
  1980年   25篇
  1979年   21篇
  1978年   15篇
  1976年   13篇
  1973年   16篇
  1970年   11篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
We analyzed in advanced ovarian serous G3 carcinoma the correlation between epidermal growth factor receptor (EGFR) overexpression and tumor angiogenesis and their relation with clinical outcome. Microvessel density (MVD) and vascular endothelial growth factor (VEGF) were statistically correlated with disease-free interval and death from disease both in univariate and multivariate analyses while EGFR expression was not correlated with clinical outcome. MVD was significantly associated with progression of disease during chemotherapy while VEGF and EGFR expression were not correlated with responsiveness to chemotherapy (Fisher's exact test). VEGF expression was correlated with MVD (Fisher's exact test). EGFR showed a trend to correlation with MVD. Further studies focusing on the use of angiogenesis inhibitors in addition to EGFR inhibitors on ovarian carcinoma cells may produce therapeutic strategies in the selection of tailored therapies in ovarian cancer patients.  相似文献   
83.
OBJECTIVE: To evaluate the effects of soy isoflavone administration on endothelial function in healthy postmenopausal women. DESIGN: Sixty naturally postmenopausal women were randomly assigned to receive isoflavone or placebo tablets for 6 months. Endothelium-dependent vasodilatation was measured by brachial reactivity technique along with levels of plasma soluble intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, P-selectin and soluble thrombomodulin, von Willebrand factor, and tissue plasminogen activator. Differences between endothelium-dependent and endothelium-independent vasodilatation were assessed by evaluating brachial reactivity parameters after reactive hyperemia and after sublingual administration of nitroglycerin; furthermore, in the active group, the effect of isoflavones was also evaluated during the intra-arterial infusion of N-monomethyl-L-arginine. Serum levels of lipids [high-density lipoprotein and low-density lipoprotein cholesterol, triglycerides and lipoprotein(a)] and hemostatic factors (prothrombin, fibrinogen, plasminogen activator inhibitor-1, and fibrin D-dimer) were also measured. To confirm the absorption of isoflavones, their blood concentrations were determined. RESULTS: Isoflavone treatment versus placebo was associated with a significant improvement in endothelium-dependent vasodilatation but had no impact on endothelial-independent arterial diameter and flow. Intra-arterial infusion of N-monomethyl-L-arginine inhibited the significant effect of isoflavones on endothelium-mediated vasodilatation. Furthermore, isoflavone group experienced statistically significant reductions in plasma concentrations of ICAM-1, VCAM-1, and E-selectin. Levels of soluble thrombomodulin, von Willebrand factor, tissue plasminogen activator, lipids, and hemostatic factors did not change significantly throughout the study in both groups. CONCLUSIONS: Our findings suggest a positive influence of soy isoflavones on endothelial function in healthy postmenopausal women as evidenced by an improvement in endothelium-dependent vasodilatation and a reduction in plasma adhesion molecule levels.  相似文献   
84.
Marfan Syndrome (MFS) is an autosomal dominant disorder of the connective tissue due to mutations of Fibrillin-1 gene (FBN1) in more than 90% of cases and Transforming Growth Factor-Beta-Receptor2 gene (TGFB2R) in a minority of cases. Genotyping is relevant for diagnosis and genotype-phenotype correlations. We describe the FBN1 genotypes and related phenotypes of 81 patients who were referred to our attention for MFS or Marfan-like phenotypes. Patients underwent multidisciplinary pertinent evaluation in the adult or paediatric setting, according to their age. The diagnosis relied on Ghent criteria. To optimise DHPLC analysis of the FBN1 gene, all coding regions of the gene were directly sequenced in 19 cases and 10 controls: heterozygous amplicons were used as true positives. DHPLC sensitivity was 100%. Then, DHPLC was used to screen 62 other cases. We identified 74 FBN1 mutations in 81 patients: 64 were novel and 17 known. Of the 81 mutations, 41 were missense (50.6%), 27, either nonsense or frameshift mutations and predicted a premature termination codon (PTC) (33%), 11 affected splice sites (13.6%), and two predicted in-frame deletions (2.5%). Most mutations (67.9%) occurred in cbEGF-like modules. Genotype was clinically relevant for early diagnosis and conclusion of the diagnostic work-up in patients with incomplete or atypical phenotypes.  相似文献   
85.
Acylphosphatase (ATPase), an enzyme that modulates the activity of Ca2+-ATPase by hydrolysing its phosphorylated moiety, has been found to be significantly higher in cultured skin fibroblasts from donors affected by early onset familial Alzheimer's disease (EOFAD) with PS-1 and PS-2 gene mutations. Of the two known isoenzymes of acylphosphatase, only the erythrocyte one accounts for the total increase in activity. No relevant alteration was observed in phosphotyrosine phosphatase activity (PTPase), in Ca2+-ATPase and Na+,K+-ATPase activities of the same cells as compared to age-matched controls. This finding could suggest a possible explanation for the calcium-dependent biochemical alterations previously described in Alzheimer's disease fibroblasts.  相似文献   
86.
A 51-year-old woman suffered rapidly irreversible cardiogenic shock with left hemiparesis. Transesophageal echocardiography, which represents an essential imaging tool in the emergency room, ruled out aortic dissection involving branch vessels but did not allow an in vivo diagnosis of spontaneous coronary dissection. The in vivo diagnosis of spontaneous coronary dissection is rather difficult because of the dramatic clinical presentation and selective coronary angiography requirement.  相似文献   
87.
The co-segregation in one pedigree of bipolar affective disorder with Darier's disease whose gene is on chromosome 12q23-q24.1, and findings from linkage and association studies with the neighbouring gene of phospholipase A2 (PLA2) indicate that PLA2 may be considered as a candidate gene for affective disorders. All relevant genetic association studies, however, were conducted on bipolar patients. In the present study, the possible association between the PLA2 gene and unipolar affective disorder was examined on 321 unipolar patients and 604 controls (all personally interviewed), recruited from six countries (Belgium, Bulgaria, Croatia, Germany, Greece, and Italy) participating in the European Collaborative Project on Affective Disorders. After controlling for population group and gender, one of the eight alleles of the investigated marker (allele 7) was found to be more frequent among unipolar patients with more than three major depressive episodes than among controls (P<0.01); genotypic association was also observed, under the dominant model of genetic transmission (P<0.02). In addition, presence of allele 7 was correlated with a higher frequency of depressive episodes (P<0.02). These findings suggest that structural variations at the PLA2 gene or the chromosomal region around it may confer susceptibility for unipolar affective disorder.  相似文献   
88.
89.
The molecular basis of Natural Killer (NK) cell recognition and function   总被引:2,自引:0,他引:2  
Natural Killer cells are likely to play an important role in the host defenses because they kill virally infected or tumor cells but spare normal self-cells. The molecular mechanism that explains why NK cells do not kill indiscriminately has recently been elucidated. It is due to several specialized receptors that recognize major histocompatibility complex (MHC) class I molecules expressed on normal cells. The lack of expression of one or more HLA class I alleles leads to NK-mediated target cell lysis. Different types of receptors specific for groups of HLA-C, HLA-B, and, very recently, HLA-A alleles have been identified. While in most instances, they function as inhibitory receptors, an activatory form of the HLA-C-specific receptors has been identified in some donors. Molecular cloning of HLA-C-, HLA-B- or HLA-A-specific receptors has revealed new members of the immunoglobulin superfamily with two or three Ig-like domains, respectively, in their extracellular portion. While the inhibitory form is characterized by a long cytoplasmic tail associated with a non-polar transmembrane portion, the activatory one has a short tail asociated with a Lys-containing transmembrane portion. Thus, these human NK receptors are different from the murine Ly49, that is a type II transmembrane protein characterized by a C-type lectin domain. A subset of activated T lymphocytes expresses NK-type class I-specific receptors. These receptors exert an inhibiting activity on T cell receptor-mediated functions and may provide an important mechanism of downregulation of T cell responses.  相似文献   
90.
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