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   49061篇
  免费   3439篇
  国内免费   3098篇
耳鼻咽喉   220篇
儿科学   538篇
妇产科学   292篇
基础医学   2656篇
口腔科学   153篇
临床医学   5550篇
内科学   13091篇
皮肤病学   214篇
神经病学   440篇
特种医学   2856篇
外国民族医学   4篇
外科学   12463篇
综合类   6327篇
预防医学   1844篇
眼科学   140篇
药学   3472篇
  34篇
中国医学   1285篇
肿瘤学   4019篇
  2024年   99篇
  2023年   836篇
  2022年   1703篇
  2021年   2059篇
  2020年   1810篇
  2019年   1518篇
  2018年   1507篇
  2017年   1400篇
  2016年   1748篇
  2015年   1836篇
  2014年   3559篇
  2013年   3006篇
  2012年   3103篇
  2011年   3263篇
  2010年   2853篇
  2009年   2854篇
  2008年   2910篇
  2007年   2823篇
  2006年   2645篇
  2005年   2166篇
  2004年   1580篇
  2003年   1342篇
  2002年   1200篇
  2001年   1049篇
  2000年   882篇
  1999年   752篇
  1998年   649篇
  1997年   579篇
  1996年   499篇
  1995年   478篇
  1994年   474篇
  1993年   325篇
  1992年   279篇
  1991年   223篇
  1990年   180篇
  1989年   181篇
  1988年   167篇
  1987年   116篇
  1986年   120篇
  1985年   113篇
  1984年   100篇
  1983年   51篇
  1982年   85篇
  1981年   79篇
  1980年   57篇
  1979年   50篇
  1978年   61篇
  1977年   46篇
  1976年   39篇
  1974年   29篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.

Objectives

The aim of the study was to characterize the differences in the frequencies of NS3 and NS5A resistance-associated variants (RAVs) among Polish therapy-naive genotype 1 (G1) hepatitis C virus (HCV)-monoinfected and human immunodeficiency virus (HIV)/HCV-coinfected patients including clustering patterns and association of RAV frequency with liver fibrosis.

Methods

NS3/NS5A RAVs were identified by population sequencing in 387 directly acting antiviral treatment-naive G1-infected individuals (54 with genotype 1a (G1a) and 333 with genotype 1b (G1b)). Liver fibrosis was assessed based on histopathology or ultrasound elastography. Phylogenetic clusters were identified using maximum likelihood models. For statistics, chi-squared or two-sided Fisher's exact tests and multivariate logistic regression models were used, as appropriate.

Results

NS3 RAVs were found in 33.33% (18/54) for G1a and 2.62% (8/297) for G1b whereas NS5A variants were present in 5.55% (3/54) G1a and 9.31% (31/333) G1b sequences. Variations in NS5A 31 and 93 codon positions were found only in G1b (4.2% (14/333) for L31I/F/M and 5.39% (17/333) for Y93H). NS5A RAVs were more frequent among patients with advanced liver fibrosis (17.17% (17/99) for F3–F4 versus 6.94% (17/245) for F0–F2; p 0.004) or liver cirrhosis (20.34% (12/59) for F4 versus 7.72% (22/285) for F0–F3; p 0.003). Liver cirrhosis (F4) was associated with higher odds ratio of the NS5A RAVs among HCV-infected patients (odds ratio 2.34, 95% CI 1.004–5.291; p 0.049). NS5A RAVs were less frequent among sequences forming clusters and pairs (5.16% (8/155) versus 11.21% (26/232); p 0.039).

Conclusions

Presence of NS5A RAVs correlated with progression of liver fibrosis and represents de novo selection of variants rather than transmission of drug resistance. Hence, the presence of NS5A RAVs may be a predictor for a long-lasting HCV infection.  相似文献   
54.
Male Wistar rats were fed ad libitum four different diets containing fructose, sucrose, maltodextrins or starch as the source of carbohydrate (CH). One group was subjected to moderate physical training on a motor-driven treadmill for 10 weeks (trained rats). A second group received no training and acted as a control (sedentary rats). Glycogen metabolism was studied in the liver and skeletal muscle of these animals. In the sedentary rats, liver glycogen concentrations increased by 60%–90% with the administration of simple CH diets compared with complex CH diets, whereas skeletal muscle glycogen stores were not significantly affected by the diet. Physical training induced a marked decrease in the glycogen content in liver (20%–30% of the sedentary rats) and skeletal muscle (50%–80% of the sedentary rats) in animals fed simple (but not complex) CH diets. In liver this was accompanied by a two-fold increase of triacylglycerol concentrations. Compared with simple CH diets, complex CH feeding increased by 50%–150% glycogen synthase (GS) activity in liver, whereas only a slight increase in GS activity was observed in skeletal muscle. In all the animal groups, a direct relationship existed between tissue glucose 6-phosphate concentration and glycogen content (r = 0.9911 in liver, r = 0.7177 in skeletal muscle). In contrast, no relationship was evident between glycogen concentrations and either glycogen phosphorylase activity or adenosine 5-monophosphate tissue concentration. The results from this study thus suggest that for trained rats diets containing complex CH (compared with diets containing simple CH) improve the glycogenic capacity of liver and skeletal muscle, thus enabling the adequate regeneration of glycogen stores in these two tissues.  相似文献   
55.
Valledor AF 《Immunobiology》2005,210(2-4):127-132
Macrophages play essential roles in infection and resolution of inflammation. This review summarizes recent findings that suggest a relevant role for the nuclear receptor liver X receptor (LXR) in the evolution of immune responses. By exerting both positive and negative regulation of specific macrophage gene expression networks, LXRs display anti-inflammatory activities and promote macrophage survival in bacterial infection settings. Agonists that activate the LXR pathway may be used to enhance innate immunity to highly virulent pathogens that otherwise induce macrophage apoptosis as a means to subvert host immune defense.  相似文献   
56.
The physicochemical properties of mitochondria in liver tissue obtained from rats given 32% ethanol, 32% propanol or 6.9% butanol in drinking water for up to 3 months were investigated using differential scanning calo-rimetry and fluorescence polarization measurements. The results obtained were as follows: 1) Phospholipids extracted from mitochondria showed increases in the relative amounts of phosphatidylcholine, phosphatidylinositol and phosphatidylserine, and a decrease in the relative amount of phosphatidylethanolamine. An increase in the unsatu-rated/saturated fatty acid ratio of phospholipids was also observed. 2) Elevation of the thermotropic lipid phase transition temperature with a decrease in the enthalpy value (δ H ) was revealed by differential scanning calo-rimetry. 3) The elevation of the lipid phase transition temperature was detected also by fluorescence polarization measurements using 1,6 diphenyl 1, 3, 5 hexatriene (DPH) as a probe. Elevation of mitochondrial membrane fluidity was found in some of the experimental animals, but most showed no changes in comparison with the control. A possible role of membrane fusion in the mechanism of formation of ethanol-, propanol- and butanol induced hepatic megamitochondria is discussed on the basis of these results. Acta Pathol Jpn 42: 549–557, 1992.  相似文献   
57.
58.
Summary A prospective series of 45 liver biopsies taken from 22 renal transplant patients was investigated for the presence of hepatitis B antigen core (HBc) and surface (HBs) components by electron microscopy. At the time of each biopsy serum HBs Ag was sought by radioimmunoassay. Sections were taken for the detection of HBs Ag by immunofluorescence.In seropositive patients, intravesicular tubular structures resembling HBs Ag were found in 61% of biopsies while the intranuclear core HBc was present in 69%. No correlation could be made between the ultrastructural pattern of the viral components and the intensity of the histological liver damage. During the follow up, there was an accumulation of both HBs and HBc Ag even in a period as short as 1 year. The 9 liver specimens examined after three years of transplantation showed a marked accumulation of both antigens. Thus the expression of HB Ag at the hepatocellular level seems to correlate better with the duration of antigenaemia than with the histological pattern.Lastly, on matched semithin and ultrathin sections, the ground glass appearance of cytoplasm appeared to correlate with smooth endoplasmic reticulum distorsion, irrespective of the simultaneous presence or absence of intravesicular tubular structures. The sanded nuclei expressed a rare massive accumulation of core antigen.  相似文献   
59.
60.
Patients with liver failure can present both thrombotic and hemorragic complications because of the deficiency in coagulation factors and inhibitors (protein C and S, antithrombin III) and impairment of fibrinolytic balance. Here we report the case of a 63-year-old man with liver cirrhosis, recurrent thrombosis, and features of low-grade consumption coagulopathy, showing severe antithrombin III deficiency (about 30% of normal values). Treatment with antithrombin III (2000 U/day) and low doses of heparin (5000 U b.i.d.) was successful in modulating the coagulation system toward an antithrombotic effect. After discharge from hospital the ambulatory treatment with antithrombin III concentrates (2000 U twice a week) allowed the attainment of antithrombin III activity of about 60% and prevented the patient from recurrence of venous thrombosis.Abbreviations AT-III Antithrombin III - DIC Disseminated intravascular coagulation - TAT complexes Thrombin-antithrombin III complexes - PAI-1 Plasminogen activator inhibitor-1  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