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   11544篇
  免费   723篇
  国内免费   104篇
耳鼻咽喉   77篇
儿科学   354篇
妇产科学   173篇
基础医学   1319篇
口腔科学   473篇
临床医学   1044篇
内科学   2707篇
皮肤病学   271篇
神经病学   888篇
特种医学   561篇
外科学   2020篇
综合类   49篇
一般理论   1篇
预防医学   645篇
眼科学   111篇
药学   574篇
中国医学   12篇
肿瘤学   1092篇
  2023年   132篇
  2022年   102篇
  2021年   464篇
  2020年   231篇
  2019年   356篇
  2018年   435篇
  2017年   296篇
  2016年   288篇
  2015年   331篇
  2014年   431篇
  2013年   527篇
  2012年   755篇
  2011年   847篇
  2010年   477篇
  2009年   447篇
  2008年   711篇
  2007年   689篇
  2006年   663篇
  2005年   638篇
  2004年   557篇
  2003年   516篇
  2002年   419篇
  2001年   218篇
  2000年   202篇
  1999年   155篇
  1998年   99篇
  1997年   84篇
  1996年   71篇
  1995年   55篇
  1994年   61篇
  1993年   47篇
  1992年   114篇
  1991年   92篇
  1990年   83篇
  1989年   79篇
  1988年   61篇
  1987年   54篇
  1986年   65篇
  1985年   52篇
  1984年   43篇
  1983年   46篇
  1982年   27篇
  1979年   30篇
  1978年   23篇
  1977年   29篇
  1975年   24篇
  1974年   31篇
  1973年   23篇
  1968年   23篇
  1967年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
ABSTRACT: Short-chain fatty acids, such as butyrate and propionate, induce fetal globin gene expression and are under clinical investigation in the β-hemoglobinopathies. Limitations of the short-chain fatty acids as therapeutics include their rapid metabolism and a tendency to induce cell growth arrest if administered for prolonged periods. In studies described here, the cellular effects of other inducers of fetal globin, phenoxyacetic acid and derivatives of short-chain fatty acids and cinnamic acids, were investigated in the human erythroid cell line K562, the IL-3 dependent multi-lineage cell line (32D), and in mice and primates. Several test compounds supported 32D cell proliferation despite a 50-fold depletion of IL-3, which resulted in growth arrest and apoptotic death in control cells. The degree of proliferation induced by certain test compounds was similar to the degree of proliferation induced by Erythropoietin and G-CSF in the cells. Eight of ten compounds induced γ globin mRNA in K562 cells. A 2.5 to 6-fold increase in reticulocytosis was observedin vivoin mice treated with two prototype compounds. Pharmacokinetic studies of three prototype compounds demonstrated millimolar plasma concentrations after single oral doses for many hours in primates. These findings identify orally bioavailable compounds which induce γ globin gene expression and hematopoietic cell proliferation through an activity which partially abrogates requirements for IL-3. Such compounds provide potential for oral therapeutics which stimulate proliferation of hematopoietic cells of multiple lineages, as well as inducing fetal globin.  相似文献   
52.
OBJECTIVES: The aim of the study was to analyze the behavior of oxidative stress and its interplay with CD40L, a protein that is implicated in atherosclerosis, in hypercholesterolemic children. BACKGROUND: Oxidative stress has been suggested to play a major role in premature atherosclerosis. METHODS: Forty-one children with hypercholesterolemia (mean age 9.28 +/- 0.5 years) and 40 children with normocholesterolemia (mean age 9.02 +/- 0.69 years) were matched for gender and age. Within each group, children were classified as having or not having a family history of cardiovascular disease. Serum levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative stress, and plasma levels of soluble CD40L (sCD40L) were measured in each child. In a subgroup of children with high (n = 8) or normal (n = 8) levels of serum cholesterol, platelet p38 mitogen-activated protein (MAP) kinase phosphorylation, a protein involved in the activation of nicotinamide adenine dinucleotide phosphate oxidase, was determined. RESULTS: Children with hypercholesterolemia had higher values of 8-OHdG and sCD40L compared with control subjects (0.55 +/- 0.06 ng/ml vs. 0.21 +/- 0.02 ng/ml, p < 0.001 and 0.55 +/- 0.04 ng/ml vs. 0.19 +/- 0.03 ng/ml, p < 0.001, respectively). A significant correlation between 8-OHdG and sCD40L was observed in children with high (r = 0.676, p < 0.001) or normal (r = 0.878, p < 0.001) levels of cholesterol. Children with a family history of cardiovascular disease tended to have higher values of 8-OHdG and sCD40L, but the difference was not significant. Analysis of platelet p38 MAP kinase showed that it was phosphorylated more in children with hypercholesterolemia compared with control subjects (36.8 +/- 5.8 AU vs. 8.0 +/- 4.5 AU, p < 0.001 respectively). CONCLUSIONS: Children with hypercholesterolemia have an early increase of oxidative stress that may be responsible for up-regulation of CD40L and potentially predispose to premature atherosclerosis.  相似文献   
53.
It is controversial whether gastrooesophageal reflux disease represents a spectrum disease from a nonerosive to a complicated one, or whether it is a categorial disease, i.e. it can be divided into three categories, such as nonerosive gastrooesophageal reflux disease, erosive gastrooesophageal reflux disease and Barrett's esophagus (BE) with little or no transition from one category to the other. This controversy might be of general interest, because it has some implications in the management of the patient. However, literature data concerning the natural history of gastrooesophageal reflux disease are very limited, and in particular very few papers have dealt with the issue of describing the natural history of patients with nonerosive gastrooesophageal reflux disease. Aim of the present review is to reassess these scanty data, and to try to demonstrate that progression from milder to more severe forms of gastrooesophageal reflux disease is possible and documented.  相似文献   
54.
AIMS: To evaluate the efficacy and safety of ezetimibe 10 mg administered with pravastatin in patients with primary hypercholesterolemia. METHODS AND RESULTS: After dietary stabilization, 2-12 week screening/washout period, and 4-week, single-blind, placebo lead-in period, 538 patients with baseline LDL-C > or =3.8 to < or =6.5 mmol/l and TG < or =4.0 mmol/l were randomized to one of eight possible treatments administered daily for 12 weeks: ezetimibe 10mg; pravastatin 10, 20, or 40 mg; ezetimibe 10 mg plus pravastatin 10, 20, or 40 mg; or placebo. The primary efficacy endpoint was percent reduction in LDL-C from baseline to study endpoint for ezetimibe 10 mg plus pravastatin (pooled doses) compared to pravastatin alone (pooled doses) and ezetimibe alone. The combined use of ezetimibe and pravastatin resulted in significant incremental reductions in LDL-C and TG compared to pooled pravastatin alone (p<0.01). Coadministration therapy reduced LDL-C by 34-41%, TG by 21-23%, and increased HDL-C by 7.8-8.4%, depending on the dose of pravastatin. The combined regimen was well tolerated, with a safety profile similar to pravastatin alone and placebo. CONCLUSIONS: When coadministered with pravastatin, ezetimibe provided significant incremental reductions in LDL-C and TG and was well tolerated with a safety profile similar to pravastatin alone.  相似文献   
55.
OBJECTIVE: To investigate the effect of improvement in erectile dysfunction (ED) on sexual function and satisfaction measures in heterosexual couples in which the woman reports that sexual intercourse is unsatisfactory at least half of the time. DESIGN: Multicentre, double-blind, placebo-controlled study. SETTING: Outpatient medical clinics. POPULATION: Hundred and eighty men with ED and their female partners in whom sexual intercourse was satisfactory about half the time or less (score of < or =3 on the Female Partner of ED Subject Questionnaire question 3 [FePEDS Q3]). METHODS: Men were randomised to flexible-dose sildenafil (25, 50, and 100 mg) or placebo as needed for 12 weeks. MAIN OUTCOME MEASURES: Primary: FePEDS Q3 ('Over the past four weeks, when you had sexual intercourse, how often was it satisfactory for you?') scored as 0 (no sexual activity) and 1 (almost never or never) to 5 (almost always or always). Secondary, partners: Sexual Function Questionnaire, Female Sexual Function Index (FSFI), and ED Inventory of Treatment Satisfaction (EDITS) partner version (EDITS-Partner). Secondary, men: International Index of Erectile Function (IIEF), General Efficacy Questions, event log data, Self-Esteem And Relationship questionnaire, and EDITS. Secondary, partners and men: Dyadic Adjustment Scale. RESULTS: The intention-to-treat population included 85 sildenafil recipients (mean age 59 +/- 12 years) and 91 placebo recipients (mean age 57 +/- 11 years). Most partners (aged 20-79 years; mean, 54 years) were postmenopausal. Sildenafil compared with placebo couples had greater improvement in the primary outcome (FePEDS Q3 [P < 0.0001]) and in sexual function, intercourse success rates, and secondary sexual satisfaction measures (FSFI satisfaction domain [P < 0.0001] and IIEF satisfaction domains [P < 0.001]) and had higher treatment satisfaction (EDITS and EDITS-Partner; P < 0.0001). Several predictors of improvement were identified, and improvement in one member of the couple correlated positively with improvement in the other member. CONCLUSIONS: The interdependence of sexual function and sexual satisfaction measures between members of couples consisting of men with ED and sexually healthy women reporting infrequent satisfactory sexual intercourse underscores the importance of including partners in ED treatment discussions.  相似文献   
56.
Statement of problem. Controversy surrounds the use of hydrofluoric acid to prepare precementation surfaces of indirect composites.Purpose. This study was conducted to compare effects of combining hydrofluoric or orthophosphoric acid with microetching as precementation treatments.Material and methods. Nine specimens of three composite materials were prepared to simulate heat-cured indirect restorations. The specimen surfaces were prepared with one of three treatments. Adhesive Bond II and Twinlook cements were used to bond a phosphoric acid-etched disk of P50 to the treated surface. Analysis of variance and Scheffé tests were used to assess the bond strength data. Scanning electron microscopy and microscopic analysis of the fractured and treated surfaces were also performed.Results. Bond strengths for all surface treatments did not significantly differ. Hybrids had a higher bond strength with etching than microfills, and mechanical roughening produced the greatest bond strengths with microfills. Microetching with orthophosphoric acid produced higher bond strengths than microetching with hydrofluoric acid on hybrids.Conclusions. Acid etching alone is not sufficient to produce effective bond strengths, and hydrofluoric acid treatments are detrimental to the resin composite. (J Prosthet Dent 1997;77:568-72.)  相似文献   
57.
58.
To compare rest-injected thallium-201 (Tl) redistribution and resting technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) myocardial uptake in chronic coronary artery disease (CAD), 15 patients with angiographically proven CAD and left ventricular (LV) dysfunction (ejection fraction 34%±9%) were studied. All patients underwent rest-redistribution Tl and resting 99mTc-MIBI cardiac imaging. Gated 99mTc-MIBI images were also acquired to assess regional LV wall motion (WM). Myocardial segments (n=225) were divided into three groups on the basis of the degree of coronary artery stenosis: group 1 (total occlusion, n=82), group 2 (50%–99% of stenosis, n=84) and group 3 (<50% of stenosis, n=59). WM was significantly worse in groups 1 and 2 compared to group 3 (P<0.001), but no difference was observed between groups 1 and 2. TI and 99mTc-MIBI uptake were significantly lower in groups 1 and 2 compared to group 3 (P < 0.001), and in group 1 compared to group 2 (P<0.001). When TI and 99mTc-MIBI uptake were directly compared, TI uptake was higher than 99mTc-MIBI uptake in group 1 (P<0.001), while no significant difference was observed in groups 2 and 3. Thus, both rest-injected TI redistribution and resting 99mTc-MIBI uptake reflected the severity of coronary artery stenosis in CAD. However, in myocardial segments with total coronary occlusion T1 uptake was significantly higher than 99mTc-MIBI uptake. Our data suggest that rest-injected Tl redistribution cardiac imaging may identify, more accurately than resting 99mTc-MIBI imaging, the presence of viable myocardium in chronic CAD, particularly when the coronary blood flow is severely impaired.  相似文献   
59.
Substance abuse and psychopathology   总被引:1,自引:0,他引:1  
This report evaluates, using DSM III, the psychopathological profile of 226 heroin users taken in at the clinical centre of "Cascina Verde" Therapeutic Community (Milan, Italy) and admitted to a psychotherapeutic, retraining, integrated, both out-and-in-patient treatment. The outcome shows that 30% of subjects are to be diagnosed according to Axis I while 61% are to be considered among Axis II personality disorders. A portion of 16% is to be referred to the "schizophrenic spectrum", 25% has histrionic, narcissistic, antisocial and borderline personality disorders and the remaining are to be referred to an extremely heterogeneous category. The report shows also data concerning Axes IV and V, always according DSM III.  相似文献   
60.
In the course of a phase I trial, in which recombinant IL-2 (rIL-2) was infused intraperitoneally (i.p.) in patients with peritoneal carcinomatosis, we evaluated the effect on "tumor-associated lymphocytes" (TAL) isolated from the ascitic fluid. No major changes in the percentages of cells expressing the CD3, CD4, CD8, Leu-7, OKM1 and WT-31 antigens were detected either in TAL or in peripheral blood lymphocytes (PBL) after 7 days of rIL-2 infusion. In contrast the percentages of TAL (but not PBL) expressing surface IL-2 receptor (Tac), or LAK-1 antigen were sharply increased. Analysis of cytolytic functions showed a potentiation of the lytic activity against natural-killer (NK) sensitive K562 target cells and the de novo appearance of lytic activity against fresh melanoma cells. In one patient IFN-gamma was detected in the ascitic fluid following rIL-2 infusion. T-cell clones derived from the patient were analyzed for the IFN-gamma production. While only approximately 40% of PB-derived control clones produced medium to low amounts of IFN-gamma, all of the TAL-derived clones produced medium to high amounts of the lymphokine.  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