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   2437篇
  免费   103篇
  国内免费   9篇
耳鼻咽喉   52篇
儿科学   66篇
妇产科学   24篇
基础医学   297篇
口腔科学   173篇
临床医学   286篇
内科学   401篇
皮肤病学   15篇
神经病学   267篇
特种医学   87篇
外科学   282篇
综合类   10篇
一般理论   3篇
预防医学   177篇
眼科学   40篇
药学   297篇
肿瘤学   72篇
  2023年   13篇
  2022年   28篇
  2021年   40篇
  2020年   24篇
  2019年   34篇
  2018年   40篇
  2017年   48篇
  2016年   50篇
  2015年   49篇
  2014年   82篇
  2013年   152篇
  2012年   128篇
  2011年   150篇
  2010年   96篇
  2009年   99篇
  2008年   160篇
  2007年   168篇
  2006年   152篇
  2005年   168篇
  2004年   156篇
  2003年   145篇
  2002年   151篇
  2001年   32篇
  2000年   25篇
  1999年   29篇
  1998年   35篇
  1997年   21篇
  1996年   20篇
  1995年   16篇
  1994年   16篇
  1993年   17篇
  1992年   13篇
  1991年   17篇
  1990年   16篇
  1989年   14篇
  1988年   16篇
  1987年   11篇
  1986年   12篇
  1985年   10篇
  1984年   20篇
  1983年   7篇
  1982年   8篇
  1981年   10篇
  1980年   9篇
  1979年   6篇
  1978年   3篇
  1977年   15篇
  1976年   6篇
  1975年   3篇
  1973年   3篇
排序方式: 共有2549条查询结果,搜索用时 0 毫秒
81.
82.
The International League Against Epilepsy (ILAE) presents a revised operational classification of seizure types. The purpose of such a revision is to recognize that some seizure types can have either a focal or generalized onset, to allow classification when the onset is unobserved, to include some missing seizure types, and to adopt more transparent names. Because current knowledge is insufficient to form a scientifically based classification, the 2017 Classification is operational (practical) and based on the 1981 Classification, extended in 2010. Changes include the following: (1) “partial” becomes “focal”; (2) awareness is used as a classifier of focal seizures; (3) the terms dyscognitive, simple partial, complex partial, psychic, and secondarily generalized are eliminated; (4) new focal seizure types include automatisms, behavior arrest, hyperkinetic, autonomic, cognitive, and emotional; (5) atonic, clonic, epileptic spasms, myoclonic, and tonic seizures can be of either focal or generalized onset; (6) focal to bilateral tonic–clonic seizure replaces secondarily generalized seizure; (7) new generalized seizure types are absence with eyelid myoclonia, myoclonic absence, myoclonic–atonic, myoclonic–tonic–clonic; and (8) seizures of unknown onset may have features that can still be classified. The new classification does not represent a fundamental change, but allows greater flexibility and transparency in naming seizure types.  相似文献   
83.

Objectives

To review the literature about oral symptoms and signs at the menopause with an emphasis on hormone replacement therapy (HRT). To give practical guidelines for women and their physicians in menopause-related oral health problems.

Methods

The PubMed and Cochrane databases was searched until mid January 2009 with key words such as “menopause”, “menopausal complaints”, “postmenopausal complaints” and “oral diseases”, “oral discomfort”, “dental health”, “dental diseases”, “saliva”, “burning mouth syndrome”, “dry mouth”, “xerostomia”. Because of a scarcity of controlled studies no systematic review could be conducted.

Results

Oral discomfort is found in many menopausal women in addition to more general climacteric complaints. The principal peri- and postmenopausal symptoms are dry mouth and burning mouth (glossodynia) which, in turn, may increase the occurrence of oral mucosal and dental diseases, such as candidiasis. The mechanisms of hormone-related oral symptoms and signs are not known although oestrogen receptors, for example, have been detected in the oral mucosa and salivary glands. In principle, the histology of oral and vaginal mucosa is very similar and thus their symptoms might share a common cause. Yet, hormone replacement therapy use does not necessarily prevent or help women with oral symptoms.

Conclusion

Properly controlled long-term randomized studies are needed to assess the effect of HRT on oral discomfort. Future gene profiling could identify women who may or may not benefit from HRT with regard to oral symptoms.  相似文献   
84.
85.
Even in experienced hands, a common problem at endoscopic retrograde cholangiopancreatography (ERCP) is difficulty in reaching a selective cannulation of the common bile duct or pancreatic duct. The success rate of biliary cannulation has improved markedly in many centers after the adoption of double-guidewire-assisted cannulation technique in cases in which the guidewire repeatedly passes into the pancreatic duct although the common bile duct is intended. Here, we describe 2 novel applications of the double-guidewire technique for difficult cannulation in ERCP. In particular, we emphasize that in addition to difficult biliary cannulation, double-guidewire technique may prove useful in difficult pancreatic cannulation. The double-guidewire technique is feasible also in cases in which the guidewire repeatedly passes into the cystic duct instead of the intended common hepatic duct and intrahepatic radicals. ERCP endoscopists should be aware of all modifications of double-guidewire technique to further increase the success rates of selective cannulations in ERCP.  相似文献   
86.
Puumala hantavirus (PUUV) causes hemorrhagic fever with renal syndrome. Characteristic clinical findings include acute kidney injury (AKI), thrombocytopenia, and capillary leakage. Smoking increases the risk of severe AKI, but it is not known whether alcohol consumption predisposes patients to a more severe infection. Liver and pancreatic enzymes, as well as biomarkers of alcohol consumption (gamma-glutamyl transferase, GGT; carbohydrate-deficient transferrin, CDT; GGT-CDT combination; and ethyl glucuronide, EtG), were measured from 66 patients with acute PUUV infection during hospitalization and at the convalescence phase. Alcohol consumption was present in 41% of the study population, 15% showing signs of heavy drinking. Alcohol use did not affect the severity of PUUV induced AKI nor the overall clinical picture of the infection. Liver enzyme levels (GGT or alanine aminotransferase, ALT) were elevated in 64% of the patients, but the levels did not associate with the markers reflecting the severity of the disease. Serum amylase activities at the convalescent stage were higher than those at the acute phase (p < 0.001). No cases with acute pancreatitis were found. In conclusion, our findings indicate that alcohol consumption does not seem to affect the clinical course of an acute PUUV infection.  相似文献   
87.
The change in augmentation index following salbutamol inhalation has been applied to evaluate endothelial function. We examined the contribution of salbutamol‐induced increase in heart rate to the observed decrease in augmentation index. Haemodynamics were recorded using whole‐body impedance cardiography and continuous pulse wave analysis from tonometric radial blood pressure. All subjects (n = 335, mean age 46, body mass index 26, 48% men) were without medications with cardiovascular influences. The effects of salbutamol inhalation (0.4 mg) versus the endothelium‐independent agent nitroglycerin resoriblet (0.25 mg) were examined during passive head‐up tilt, as the haemodynamic influences of these compounds depend on body position. Salbutamol decreased augmentation index by ~3‐4% units in supine and upright positions. Although salbutamol moderately increased cardiac index (+4.5%) and decreased systemic vascular resistance (?8.5%), the significant haemodynamic explanatory factors for decreased augmentation index in multivariate analysis were increased supine heart rate, and increased upright heart rate and decreased ejection duration (< 0.001 for all, r= 0.36–0.37). Sublingual nitroglycerin decreased supine and upright augmentation index by ~15% units and ~23% units, respectively. The haemodynamic explanatory factors for these changes in multivariate analysis were increased heart rate, reduced ejection duration and reduced systemic vascular resistance ( 0.021 for all, r2 = 0.22–0.34). In conclusion, the lowering influence of salbutamol on augmentation index may be largely explained by increased heart rate, suggesting that this effect may not predominantly reflect endothelial function.  相似文献   
88.
Background: The aims of the present study include: 1) to localize human neutrophil defensin‐1 (HNP‐1) through HNP‐3 in gingiva and in neutrophil extract‐treated epithelial cell monolayers; 2) to determine the effects of HNP‐1 on the epithelial cell viability, attachment, and spreading; and 3) to analyze the effect of HNP‐1 on the bacterial adherence to epithelial cells. Methods: For localization of HNP‐1 through HNP‐3 in gingival tissue and in preincubated cell monolayers, immunohistochemical and immunocytochemical methods were used. Viability and proliferation of epithelial cells were determined with commercial kits after incubating the keratinocytes with different HNP‐1 concentrations (low, 1 to 5 μg/mL; moderate, 10 μg/mL; high, 20 to 50 μg/mL). Attachment and spreading of keratinocytes on fibronectin‐coated surfaces in the presence of HNP‐1 were evaluated under microscope. Attachment of Fusobacterium nucleatum ATCC25586 and Prevotella intermedia ATCC25611 on keratinocytes preincubated with HNP‐1 were determined with a standard antibiotic test. Results: HNP‐1 through HNP‐3 localized in the junctional epithelium of clinically healthy gingiva and in the pocket epithelium of gingiva with periodontitis. When keratinocyte monolayers were incubated with neutrophil extracts, HNP‐1 through HNP‐3 were bound to the periphery of the growing cell colonies. In low HNP‐1 concentrations, the keratinocyte proliferation enhanced. Moderate and high concentrations of HNP‐1 increased the cellular death significantly. HNP‐1 increased the attachment and spreading of keratinocytes on fibronectin‐coated surfaces and bacterial attachment to keratinocytes in a concentration‐dependent manner. Conclusion: HNP‐1 plays a role in the integrity of keratinocytes by stimulating their proliferation, attachment, and spreading, whereas higher doses increase the bacterial attachment and keratinocyte death.  相似文献   
89.
Few studies covering all patient groups and specialties are available regarding the outcome of nosocomial bloodstream infections (BSI). We analyzed the role of patient characteristics and causative pathogens of nosocomial BSIs reported by the hospitals participating in national surveillance in Finland during 1999–2014, in terms of outcome, with particular interest in those leading to death within 2 days (i.e. early death). National nosocomial BSI surveillance was laboratory-based and hospital-wide. Data on nosocomial BSIs was collected by infection control nurses, and dates of death were obtained from the national population registry with linkage to national identity codes. A total of 17,767 nosocomial BSIs were identified; 557 BSIs (3%) were fatal within 2 days and 1150 (6%) within 1 week. The 1-month case fatality was 14% (2460 BSIs), and 23% of the deaths occurred within 2 days and 47% within 1 week. The patients who died early were older than those who survived >?28 days, and their BSIs were more often related to intensive care. Gram-positive bacteria caused over half of the BSIs of patients who survived, whereas gram-negative bacteria, especially Pseudomonas aeruginosa, caused more often BSIs of patients who died early, and fungi BSIs of patients who died within 1 week. A significant portion of patients with nosocomial BSIs died early, which underlines the importance of rapid recognition of BSI. Hospital-wide surveillance data of causative pathogens can be utilized when composing recommendations for empiric antimicrobial treatment in collaboration with clinicians, as well as when promoting infection prevention.  相似文献   
90.
The degradation and erosion of solvent cast films and injection molded bars prepared from poly(epsilon-caprolactone) (PCL) and 2,2'-bis(2-oxazoline) linked poly(epsilon-caprolactone) (PCL-O) were evaluated in simulated gastric fluid (SGF) (pH 1.2, pepsin present) and in simulated intestinal fluid (SIF) (pH 7.5, pancreatin present). After incubation of the polymer films (10 mg) and bars (70 mg) in the medium, the resulting decrease in molecular weight (degradation) was determined by size exclusion chromatography and the weight loss of the preparations was measured. In addition, the effect of pancreatin on FITC-dextran (MW 4400) release from PCL and PCL-O microparticles, prepared by w/o/w double emulsion technique, was studied. No degradation or weight loss was observed for either PCL or PCL-O films in SGF (12 h incubation, 37 degrees C). When compared to PBS pH 7.4, pancreatin hardly enhanced the weight loss of PCL films and bars. In contrast, pancreatin enhanced substantially erosion of PCL-O films and bars. Unlike PCL preparations, the PCL-O preparations showed surface erosion in SIF. Pancreatin increased considerably FITC-dextran release from both PCL and PCL-O microparticles. In conclusion, the present results demonstrate the enzyme sensitivity of the novel PCL-O polymer. In addition, the results show that pancreatin present in intestinal fluid may substantially affect drug release from PCL based preparations.  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