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   524篇
  免费   83篇
耳鼻咽喉   4篇
儿科学   21篇
妇产科学   33篇
基础医学   80篇
口腔科学   13篇
临床医学   129篇
内科学   91篇
皮肤病学   12篇
神经病学   29篇
特种医学   14篇
外科学   44篇
预防医学   73篇
眼科学   15篇
药学   31篇
肿瘤学   18篇
  2023年   1篇
  2022年   1篇
  2021年   13篇
  2020年   11篇
  2019年   19篇
  2018年   11篇
  2017年   19篇
  2016年   18篇
  2015年   26篇
  2014年   20篇
  2013年   21篇
  2012年   30篇
  2011年   29篇
  2010年   20篇
  2009年   21篇
  2008年   26篇
  2007年   22篇
  2006年   24篇
  2005年   18篇
  2004年   31篇
  2003年   26篇
  2002年   22篇
  2001年   10篇
  2000年   12篇
  1999年   20篇
  1998年   15篇
  1997年   6篇
  1996年   4篇
  1995年   8篇
  1994年   10篇
  1993年   6篇
  1992年   6篇
  1991年   8篇
  1990年   8篇
  1989年   4篇
  1988年   6篇
  1987年   6篇
  1986年   3篇
  1985年   7篇
  1984年   5篇
  1983年   7篇
  1982年   6篇
  1981年   5篇
  1980年   4篇
  1979年   2篇
  1978年   3篇
  1976年   4篇
  1974年   1篇
  1973年   1篇
  1969年   1篇
排序方式: 共有607条查询结果,搜索用时 31 毫秒
91.
BACKGROUND: The characteristic feature of chronic rhinosinusitis with nasal polyposis (CRSwNP) is eosinophilic inflammation of the sinus mucosa; a type of inflammation also seen in asthmatic airways. Similar histopathologic findings of airway remodelling are present in both diseases. Remodelling is tightly controlled by matrix metalloproteinases (MMP). Increase of collagenase-2 (MMP-8) expression in the bronchial epithelial cells has been described in asthmatic patients, but it has not been studied in CRSwNP. METHODS: The concentrations and degree of activation of MMP-8 were analysed by immunofluorometric assay and Western blotting, respectively, in sinus mucus samples from CRSwNP patients and in nasal lavages from healthy controls in relation to inductive cytokines interleukin-8 (IL-8) and tumour necrosis factor-alpha (TNF-alpha). RESULTS: Significantly elevated levels of MMP-8 and IL-8 but not TNF-alpha were found in CRSwNP patients relative to controls. In particular, the activation of mesenchymal-type MMP-8 but not polymorphonuclear-type MMP-8 was associated with elevated IL-8 levels. CONCLUSIONS: The IL-8 and MMP-8 seemingly form an inductive cytokine-proteinase cascade in CRSwNP pathogenesis. Together they provide a target for novel therapies and a diagnostic tool for monitoring CRSwNP treatment.  相似文献   
92.
BACKGROUND: The reduction of multiple pregnancies by using elective single embryo transfers (eSET) requires critical and careful selection of the embryo for transfer. The current study was undertaken to assess whether early cleavage could be used as a marker of embryo competence in eSET procedures. METHODS: The study included analysis of 178 eSET procedures. All embryos were checked for early cleavage at 25-27 h post insemination or ICSI. The embryos that possessed two cells at 25-27 h post insemination or ICSI were designated as 'early cleavage' (EC) embryos and those that had not yet cleaved were classified as 'no early cleavage' (NEC) embryos. Selection of the embryo for transfer was based on embryo morphology and growth rate on day 2 and not early cleavage. Clinical parameters were compared between 72 EC and 106 NEC single embryo transfers. RESULTS: A significantly higher clinical pregnancy rate was observed after transfer of EC (50%) than NEC (26.4%) embryos. CONCLUSIONS: The current study provides compelling evidence that EC embryos possess significantly higher developmental competence than NEC embryos.  相似文献   
93.
Despite many studies on the prevalence of breakfast eating, we know little about factors that determine breakfast eating patterns. Our aim was to find out to which extent breakfast eating frequency is influenced by genetic and environmental factors using twin and twin-family models in a population sample of 16-year-old twins (n = 5250) and their parents (n = 4663). In common effects sex-limitation models, additive genetic effects explained 41% (95% CI: 21-63%) of the variance in breakfast eating in girls and 66% (95% CI: 47-79%) in boys, and common environmental effects 45% (95% CI: 23-62%) in girls and 14% (95% CI: 5-29%) in boys. Of twin-family models, phenotypic assortment models fitted the data best. Heritability estimates increased somewhat (72%, 95% CI: 46-98% in girls and 63%, 95% CI: 38-89%) in boys. Common family environment remained substantial in both sexes. Cultural transmission was nonsignificant. The relative influence of genetic and family factors on adolescent breakfast eating frequency differs by sex and is generation-specific.  相似文献   
94.
We evaluated the performance of new enzyme immunoassay (EIA) kits (Pyloriset; Orion Corporation, Orion Diagnostica, Espoo, Finland) for the detection of immunoglobulin G (IgG) and IgA antibodies to Helicobacter pylori in serum. Serum samples from 195 patients with upper abdominal complaints were collected. Biopsy specimens of the gastric mucosae were taken for histological analysis and bacterial culture. The sensitivity, specificity, and positive and negative predictive values, and efficacy of the Pyloriset EIA-G in detecting IgG antibodies to H. pylori were 92, 84, 88, 90, and 89%, respectively, when compared with those of the reference methods used. The corresponding data for detection of IgA antibodies were 80, 89, 89, 79, and 84%, respectively. The overall prevalence of defined H. pylori positivity was 54%. Moreover, the antibody tests showed a very good correlation with the biopsy findings. IgG antibodies were found in 93% of sera from patients with documented gastritis and H. pylori positivity, whereas only 4% of the sera from patients with documented gastritis and H. pylori-negative patients was positive. The results obtained for IgA antibodies were 81 and 6%, respectively. We conclude that the Pyloriset EIA-G, the test for IgG antibodies, is a good and reliable test for the detection of antibodies to H. pylori and as an indication of H. pylori infection. The determination of IgA antibodies may be used as a test that complements the IgG antibody assay.  相似文献   
95.
96.
97.
During aortic cross-clamping, the myocardium suffers from global ischemia, which is followed by reperfusion after declamping. The generation of free oxygen radicals increases during reperfusion, resulting in arrhythmias and impaired cardiac function. This study was conducted to evaluate the effect of a novel antioxidant nitecapone (NC) on cardiac reperfusion injuryin vivo. Twelve pigs were anesthetized and after sternotomy the aorta and the right atrium were cannulated for cardiopulmonary bypass. The heart was arrested with either +4°C crystalloid cardioplegia alone in the control group (n=6) or cardioplegia with NC (50 µM) added in the NC group (n=6). Cardioplegia was added every 20 minutes. After 1 hour of aortic crossclamping, blood samples for oxidative stress analysis were taken, and hemodynamic profile surveillance continued for 90 minutes. Heart rate (p=0.04) and left ventricular end diastolic pressure (LVEDP) (p=0.04) were significantly lower in the NC group than in the C group after aortic declamping. Cardiac output and myocardial contractility (dP/dtmax) were also enhanced in the group receiving NC, but the difference was not statistically significant. At 30 minutes after reperfusion, the coronary production (coronary sinus-aorta) of thiobarbituric acid reactive substances correlated inversely with cardiac output (r=–0.90,p=0.001) and stroke volume (r=–0.82,p=0.007). The effect of NC on lipid peroxidation seems to be modest and therefore the target of NC is unclear. NC would appear, however, to be a beneficial additive in the crystalloid cardioplegia in terms of functional recovery.  相似文献   
98.
Although nut consumption has been associated with several health benefits, it has not been investigated in individuals with type 1 diabetes. Therefore, our aim was to assess nut consumption and its association with metabolic syndrome in adult individuals with type 1 diabetes taking part in the Finnish Diabetic Nephropathy Study. The nut intake of the 1058 participants was assessed from 3-day food records that were completed twice, and the number of weekly servings, assuming a serving size of 28.4 g, was calculated. Metabolic syndrome was defined as the presence of ≥3 of the cardiovascular risk factors: central obesity, high blood pressure (≥130/85 mmHg or use of antihypertensive medication), high triglyceride concentration (≥1.70 mmol/L or use of lipid-lowering medication), low HDL-cholesterol concentration (<1.00 mmol/L in men and <1.30 mmol/L in women or use of lipid-lowering medication), and hyperglycaemia. Overweight/obesity was defined as a BMI ≥25 kg/m2. HbA1c > 59 mmol/mol (>7.5%) was used as a criterion for suboptimal glycaemic control. Of the 1058 (mean age 46 years, 41.6% men) participants, 689 (54.1%) reported no nut intake. In the remaining sample, the median weekly nut intake was 40.8 g. In the adjusted models, higher nut intake, as the continuous number of weekly servings and the comparison of those with <2 and ≥2 weekly servings, was associated with lower metabolic syndrome score, waist circumference, HbA1c, and BMI. Nut consumption as a continuous variable was negatively associated with the presence of metabolic syndrome, its blood pressure, triglyceride, and HDL-cholesterol components, and suboptimal glycaemic control. Consumption of ≥2 weekly servings was associated with lower odds of suboptimal glycaemic control (by 51.5%), overweight/obesity (by 33.4%), and metabolic syndrome (by 51.8%) and meeting the waist (by 37.3%), blood pressure (by 44.5%), triglyceride (by 37.7%), and HDL-cholesterol (by 36.2%) components of the metabolic syndrome. In conclusion, a weekly nut intake of ≥2 servings was beneficially associated with all the components of the metabolic syndrome in type 1 diabetes. The causality of this association will need to be investigated.  相似文献   
99.
The nucleotide sequence of the rat monocarboxylate transporter MCT2 was determined from brain-derived cDNA. A polyclonal antibody was raised in chickens against the carboxyl terminal end of the deduced amino acid sequence and affinity purified. The MCT2 antibody identified a 46-kDa band on immunoblots and labeled kidney, skeletal muscle, and stomach consistent with the reported cellular expression for this transporter. Light microscopic immunocytochemistry indicated that the MCT2 transporter was abundant in glial limiting membranes, ependymocytes, and neuropil, particularly in the lacunosum molecular layer of hippocampus and the molecular layer of cerebellum. Labeled astrocytes were commonly observed in white matter. The distribution of this transporter differed in several respects from that previously reported for MCT1. MCT2 was abundantly distributed in astrocyte foot processes and was usually not detected in other cells of the cerebrovasculature, including vascular smooth muscle cells, pericytes, and endothelium. In addition, the granular layer of cerebellum, which showed little MCT1 labeling, exhibited MCT2 labeling of cellular processes in the neuropil surrounding the granule and Purkinje cells. The results lend support to the concept that astrocytes play a significant role in cerebral energy metabolism by transporting lactate and other monocarboxylates. GLIA 22:272–281, 1998. © 1998 Wiley-Liss, Inc.  相似文献   
100.
Glioma is the commonest primary intracranial tumour and it has been the most predominant tumour in many studies.It accounts for 24.7% of all primary brain tumour and 74.6% of malignant brain tumour. Intraoperative diagnosisplays a crucial role in determining the patient management. Frozen section has been the established technique inproviding rapid and accurate intraoperative diagnosis. However due to some disadvantages like ice crystal artefact,high expenditure and requirement of skilled technician, there is increase usage of cytology smear either replacing orsupplementing frozen section technique. The aim of this review is to determine the diagnostic accuracy of cytologysmear and frozen section in glioma and to see whether there is significant difference between those techniques. Theoverall diagnostic accuracy for frozen section in glioma ranging from 78.4% to 95% while for cytology smear, thediagnostic accuracy ranging from 50% to 100%. Based on certain literatures, no statistically difference was observedin diagnostic accuracy of cytology smear and frozen section. Thus, cytology smear provides an alternative method inestablishing intraoperative diagnosis. Both cytology smear and frozen section are complimentary to each other. It isrecommended to use both techniques to improve the diagnostic accuracy in addition with adequate knowledge, clinicalhistory, neuroimaging and intraoperative findings.  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