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   7450篇
  免费   448篇
  国内免费   60篇
耳鼻咽喉   66篇
儿科学   209篇
妇产科学   127篇
基础医学   1234篇
口腔科学   402篇
临床医学   560篇
内科学   1689篇
皮肤病学   213篇
神经病学   639篇
特种医学   134篇
外科学   832篇
综合类   60篇
一般理论   2篇
预防医学   609篇
眼科学   136篇
药学   510篇
中国医学   52篇
肿瘤学   484篇
  2024年   8篇
  2023年   120篇
  2022年   245篇
  2021年   388篇
  2020年   219篇
  2019年   321篇
  2018年   306篇
  2017年   212篇
  2016年   278篇
  2015年   276篇
  2014年   320篇
  2013年   415篇
  2012年   610篇
  2011年   644篇
  2010年   333篇
  2009年   264篇
  2008年   442篇
  2007年   432篇
  2006年   376篇
  2005年   370篇
  2004年   303篇
  2003年   287篇
  2002年   237篇
  2001年   57篇
  2000年   74篇
  1999年   53篇
  1998年   59篇
  1997年   34篇
  1996年   19篇
  1995年   15篇
  1994年   12篇
  1993年   11篇
  1992年   32篇
  1991年   23篇
  1990年   14篇
  1989年   11篇
  1988年   16篇
  1987年   9篇
  1986年   10篇
  1985年   20篇
  1984年   8篇
  1983年   11篇
  1982年   8篇
  1981年   9篇
  1980年   5篇
  1979年   6篇
  1977年   4篇
  1974年   4篇
  1969年   4篇
  1967年   4篇
排序方式: 共有7958条查询结果,搜索用时 11 毫秒
1.
BACKGROUND/AIMS: Spontaneous bacterial peritonitis (SBP) is an important complication in cirrhotic patients. The aim of the present study was to assess the incidence, predictive factors and prognosis for renal impairment (RI) after SBP in cirrhotic patients from southern Brazil. METHODS: Of the 1030 hospitalizations evaluated, 114 episodes of SBP were diagnosed in 94 patients (mean age 49 years; 76.59% men). SBP diagnosis was established when the ascitic fluid polymorphonuclear cell count was equal to or greater than 250 cells/mm3. Five cases were excluded. The variables assessed as possible predictors of steady or progressive RI were blood urea nitrogen and creatinine levels before the diagnosis of SBP; type of infection, antibiotic prophylaxis, first episode or recurrent SBP, presence of gastrointestinal bleeding and hepatic encephalopathy during hospitalization, SBP resolution, Child-Pugh classification, levels of blood pressure, ascitic fluid and blood polymorphonuclear cell count, bacteriological data (positive and negative ascitic fluid culture), albumin, bilirubin, sodium and prothrombin time at the moment of diagnosis. RESULTS: The incidence of SBP was 11.07%. In 61 (55.96%) episodes, SBP was associated with RI (transient in 57.37%; steady in 19.67%; and progressive in 22.95%). The mortality rate associated with progressive RI was 100%; 58.33% with steady RI; and 2.85% with transient RI. The mortality rate in patients with or without RI was 36.07% and 6.25%, respectively (P<0.001). The level of creatinine (greater than or equal to 1.3mg/dL) before the diagnosis of SBP and the rate of infection resolution were the only predictors of RI in the multivariate analysis. CONCLUSIONS: RI after SBP is a common complication, and indicates a poor prognosis for this infection. High levels of creatinine before infection and the rate of infection resolution are independent predictors of RI.  相似文献   
2.
We compared the functional status of the hypothalamic dopaminergic tone in patients given an allogeneic hematopoietic stem cell transplantation (allo-HSCT) with chronic graft-versus-host disease (GVHD) with that observed in patients with allo-HSCT without chronic GVHD and in healthy controls. The effect of acute dopaminergic blockade with intravenous metoclopramide on serum prolactin (PRL) concentrations was evaluated. Twenty volunteers, 20 to 52 years of age, seronegative for both hepatitis C virus and the human immunodeficiency virus, were studied: (1) 10 clinically healthy men (group 1), and (2) 9 patients with leukemia, and 1 patient with refractory aplastic anemia who underwent allo-HSCT, 5 of whom (3 men and 2 women) developed chronic GVHD (group 2), and 5 (3 men and 2 women) who did not develop chronic GVHD (group 3). Serum PRL concentrations were measured both fasting and after intravenous administration of metoclopramide (10-mg bolus). The area under the PRL curve was calculated. Patients in group 2 were older than those in groups 1 and 3 (P<.018), but their body mass index was similar. Fasting serum PRL concentrations were similar among the 3 groups; however, group 2 had higher PRL concentrations throughout the test (P<.001) and a greater area under the PRL curve than groups 1 and 3 (P<.001), without differences between the last 2 groups. The differences remained significant after adjustment for age (P<.01). Our results in a small group of patients with chronic GVHD after allo-HSCT suggest the existence of an increased functional level of their hypothalamic dopamine tone, which would favor a tendency toward a diminished endogenous production, release of pituitary PRL, or both. This could represent an adaptive mechanism aiming to maintain circulating PRL concentrations within a physiological range.  相似文献   
3.
4.
Background: Neuraxial blockade is used as primary anesthetic technique in one third of surgical procedures. The authors tested whether bisoprolol would protect patients at risk for cardiovascular complications undergoing surgery with spinal block.

Methods: The authors performed a double-blinded, placebo-controlled, multicenter trial to compare the effect of bisoprolol with that of placebo on 1-yr composite outcome including cardiovascular mortality, nonfatal myocardial infarction, unstable angina, congestive heart failure, and cerebrovascular insult. Bisoprolol was given orally before and after surgery for a maximum of 10 days. Adrenergic receptor polymorphisms and safety outcome measures of bisoprolol therapy were also determined.

Results: A total of 224 patients were enrolled. Spinal block could not be established in 5 patients. One hundred ten patients were assigned to the bisoprolol group, and 109 patients were assigned to the placebo group. The mean duration of treatment was 4.9 days in the bisoprolol group and 5.1 days in the placebo group. Bisoprolol therapy reduced mean heart rate by 10 beats/min. The primary outcome was identical between treatment groups and occurred in 25 patients (22.7%) in the bisoprolol group and 24 patients (22.0%) in the placebo group during the 1-yr follow-up (hazard ratio, 0.97; 95% confidence interval, 0.55-1.69; P = 0.90). However, carriers of at least one Gly allele of the [beta]1-adrenergic receptor polymorphism Arg389Gly showed a higher number of adverse events than Arg homozygous (32.4% vs. 18.7%; hazard ratio, 1.87; 95% confidence interval, 1.04-3.35; P = 0.04).  相似文献   

5.
Ocotea quixos essential oil was shown to possess significant inhibitory activity of platelet aggregation and clot retraction in rodent plasma. This study is aimed at fully characterizing the antiplatelet activity of the whole essential oil and its main components trans-cinnamaldehyde and methyl cinnamate also in human plasma, at investigating the mechanism underlying such activity and at evaluating the potential antithrombotic activity of subacute treatment of mice with Ocotea essential oil. In vitro Ocotea essential oil and trans-cinnamaldehyde inhibited arachidonic acid-, U46619-, ADP-, phorbol12-myristate13-alcetate-, collagen-induced platelet aggregation and thrombin-induced clot retraction in human and rodent plasma; Ocotea oil and trans-cinnamaldehyde competitively antagonized contractions induced by thromboxane A2 receptor agonist U46619 in rat isolated aortic ring (K(B) = 18 and 3.2 microg ml(-1), respectively). In vivo Ocotea oil, orally administered in a subacute treatment (30-100 mg kg(-1) day(-1) for 5 days) to mice, prevented acute thrombosis induced by collagen-epinephrine intravenous injection. This antithrombotic activity was not accompanied by pro-haemorragic side effect, as detected by the inactivity in bleeding test, thus showing a favourable safety profile compared to the conventional antiplatelet agent, acetylsalicylic acid. Present findings indicate that Ocotea essential oil possesses potent and safe antithrombotic activity attributable to its antiplatelet and vasorelaxant effects. The main constituent trans-cinnamaldehyde seems to be the primary responsible for this activity through a putative mechanism involving the inhibition of thromboxane A2 receptors.  相似文献   
6.
To evaluate the correlation between persistent symptoms while stents are in place and final outcome in children with nasolacrimal duct obstruction (NLDO). A retrospective observational case series, with medical record review that included indications for surgery, surgical procedure, presence of symptoms while stents were in place, and final outcome after stent removal. Twenty-eight children with NLDO had nasolacrimal duct stents placed in 42 eyes. Twenty-one of the 42 eyes (50%) had minimal or no signs or symptoms of NLDO while stents were in place, and 18 of 21 (86%) were symptom-free after stent removal. Twenty-one of the 42 eyes (50%) remained symptomatic while stents were in place. Eleven of these 21 eyes (52%) had good outcomes after stent removal. Ten (48%) of these patients had persistent symptoms after stent removal requiring further treatment. The prognosis for a good outcome is excellent if symptoms of NLDO resolve while stents are in place. The prognosis is poorer if symptoms of NLDO persist, but more than half of such patients still have good outcomes. Careful counseling of parents regarding these outcomes should be performed before considering additional interventions.  相似文献   
7.
8.
9.
Body composition measured with isotopic dilution was compared with anthropometric measurements. The study was carried out in 47 subjects from both sexes, 65 to 92 years old. Total body water (TBW), anthropometric measurements, and dynamometry were assessed. TBW was significatively higher in men than women and decreased with age. Dynamometry and fatfree mass were well correlated (r=0.73 in males and r=0.58 in females) and significantly different between sexes. A negative correlation was found for dynamometry with age, being significant for women. Linear regression equations to predict TBW from anthropometric measurements in males and females were obtained: Males: TBW(I)=19.349+0.617 weight(kg) — 0.931 mid-arm circumference(cm)+0.122 dynamometry (kg) Females: TBW(l)=−5.531+0.343 weight(kg)-0.213 triceps skinfold (mm)+ 0.148 dynamometry(kg) + 3.424 wrist diameter (cm). This simple model is proposed for use in epidemiological and field studies where other more sophisticated methods can not be applied.  相似文献   
10.
OBJECTIVE: To test the hypothesis that short stature is associated with abdominal obesity, insulin resistance and lipid profile changes. METHODS: Anthropometric data were collected from 237 women (18-60 years old), residents of a shantytown in Maceió. Biochemical profiles of 60 individuals drawn from this population were determined. RESULTS: Total and low-density lipoprotein (LDL) cholesterol levels and insulin resistance rose with increasing waist : hip circumference ratio, particularly in women. Short, overweight individuals exhibited larger biochemical alterations than overweight individuals of average stature. CONCLUSION: Short stature, when associated with overweight, is a risk factor for increased insulin resistance and alterations in lipid profile.  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