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   4556篇
  免费   223篇
  国内免费   9篇
耳鼻咽喉   91篇
儿科学   167篇
妇产科学   184篇
基础医学   633篇
口腔科学   65篇
临床医学   395篇
内科学   921篇
皮肤病学   19篇
神经病学   532篇
特种医学   239篇
外科学   581篇
综合类   27篇
一般理论   2篇
预防医学   349篇
眼科学   128篇
药学   266篇
中国医学   1篇
肿瘤学   188篇
  2023年   8篇
  2022年   22篇
  2021年   48篇
  2020年   59篇
  2019年   68篇
  2018年   89篇
  2017年   73篇
  2016年   85篇
  2015年   80篇
  2014年   109篇
  2013年   181篇
  2012年   273篇
  2011年   322篇
  2010年   180篇
  2009年   156篇
  2008年   319篇
  2007年   366篇
  2006年   346篇
  2005年   350篇
  2004年   288篇
  2003年   290篇
  2002年   268篇
  2001年   45篇
  2000年   45篇
  1999年   57篇
  1998年   51篇
  1997年   53篇
  1996年   67篇
  1995年   56篇
  1994年   49篇
  1993年   46篇
  1992年   30篇
  1991年   37篇
  1990年   23篇
  1989年   25篇
  1988年   17篇
  1987年   17篇
  1986年   21篇
  1985年   25篇
  1984年   17篇
  1983年   20篇
  1982年   19篇
  1981年   10篇
  1980年   9篇
  1979年   6篇
  1978年   6篇
  1976年   12篇
  1975年   7篇
  1973年   4篇
  1969年   6篇
排序方式: 共有4788条查询结果,搜索用时 234 毫秒
71.
Allergic diseases are common and frequently coexist. Allergen immunotherapy (AIT) is a disease‐modifying treatment for IgE‐mediated allergic disease with effects beyond cessation of AIT that may include important preventive effects. The European Academy of Allergy and Clinical Immunology (EAACI) has developed a clinical practice guideline to provide evidence‐based recommendations for AIT for the prevention of (i) development of allergic comorbidities in those with established allergic diseases, (ii) development of first allergic condition, and (iii) allergic sensitization. This guideline has been developed using the Appraisal of Guidelines for Research & Evaluation (AGREE II) framework, which involved a multidisciplinary expert working group, a systematic review of the underpinning evidence, and external peer‐review of draft recommendations. Our key recommendation is that a 3‐year course of subcutaneous or sublingual AIT can be recommended for children and adolescents with moderate‐to‐severe allergic rhinitis (AR) triggered by grass/birch pollen allergy to prevent asthma for up to 2 years post‐AIT in addition to its sustained effect on AR symptoms and medication. Some trial data even suggest a preventive effect on asthma symptoms and medication more than 2 years post‐AIT. We need more evidence concerning AIT for prevention in individuals with AR triggered by house dust mites or other allergens and for the prevention of allergic sensitization, the first allergic disease, or for the prevention of allergic comorbidities in those with other allergic conditions. Evidence for the preventive potential of AIT as disease‐modifying treatment exists but there is an urgent need for more high‐quality clinical trials.  相似文献   
72.
73.
Purpose: The aim of the study was to investigate the molecular mechanisms involved in apoptosis of human promyelocytic cells (HL60) induced by hyperthermia and to compare this to radiation-induced apoptosis as a reference model.

Materials and methods: Apoptosis of HL60 cells was induced by heat-treatment (43°C during 1?h) or by γ-radiation (8?Gy) and followed at increasing time periods after treatment with Annexin V binding to phosphatidylserine (PS). The transition of the mitochondrial membrane potential (Δψm) was estimated by the extent of mitochondrial JC-1 uptake. Bcl-2 and Bax protein expression levels were monitored using fluorescent-labelled antibodies. Caspase activation was studied using a fluorochrome-labelled pan-caspase inhibitor (FLICA), which also allowed one to study the kinetics of the apoptotic cascade.

Results: After heat-treatment or irradiation of HL60 cells, a decreased Δψm as well as PS membrane expression were detectable after 8?h. Bcl-2 and Bax protein expression levels were decreased and increased, respectively, 1?h after heat-treatment or irradiation. The apoptotic rate of HL60 cells, as measured by the FLICA binding, was faster with heat-treatment as compared to γ-irradiation. Addition of a pan-caspase inhibitor prevented PS externalization after heat-treatment but not after irradiation. The presence of a pan-caspase inhibitor did not influence the decrease of Δψm both after heat-treatment and γ-irradiation. However, the addition of the specific caspase-2 inhibitor zVDVAD-fmk prevented the mitochondrial breakdown after heat-treatment. Inhibition of caspase-2 had no effect on the γ-irradiation induced apoptosis.

Conclusion: These results suggest that the commitment to apoptosis in HL60 cells after heat-treatment is started by mitochondrial membrane transition involving the Bcl-2 family members and is mainly executed in a caspase-dependent pathway. The results suggest that caspase-2 plays a key role in the heat-induced apoptosis.  相似文献   
74.
75.
Introduction In many Western countries, a vast amount of interventions exist that aim to facilitate return to work (RTW) after sickness absence. These interventions are usually focused on specific target populations such as employees with low back pain, stress-related complaints or adjustment disorders. The aim of the present study is to detect and identify characteristics of RTW interventions that generally facilitate return to work (i.e. in multiple target populations and across interventions). This type of knowledge is highly relevant to policy makers and health practitioners who want to deliver evidence based care that supports the employee??s health and participation in labour. Methods We performed a keyword search (systematic literature review) in seven databases (period: 1994?C2010). In total, 23 articles were included and assessed for their methodological quality. The characteristics of the interventions were evaluated as well. Results Early interventions, initiated in the first 6?weeks of the RTW process were scarce. These were effective to support RTW though. Multidisciplinary interventions appeared effective to support RTW in multiple target groups (e.g. back pain and adjustment disorders). Time contingent interventions in which activities followed a pre-defined schedule were effective in all physical complaints studied in this review. Activating interventions such as gradual RTW were effective in physical complaints. They have not been studied for people with psychological complaints. Conclusions Early- and multidisciplinary intervention and time-contingent-, activating interventions appear most effective to support RTW.  相似文献   
76.
OBJECTIVES: The goal of this study was to evaluate combinations of eptifibatide with reduced-dose tenecteplase (TNK) in ST-elevation myocardial infarction (STEMI). BACKGROUND: Glycoprotein IIb/IIIa inhibitors enhance thrombolysis. The role of combination therapy in clinical practice remains to be established. METHODS: Patients (n = 438) with STEMI <6 h were enrolled. In dose-finding, 189 patients were randomized to different combinations of double-bolus eptifibatide and reduced-dose TNK. In dose-confirmation, 249 patients were randomized 1:1 to eptifibatide 180 microg/kg bolus, 2 microg/kg/min infusion, and 180 microg/kg bolus 10 min later (180/2/180) plus half-dose TNK (0.27 mg/kg) or standard-dose (0.53 mg/kg) TNK monotherapy. All patients received aspirin and unfractionated heparin (60 U/kg bolus; infusion 7 U/kg/h [combination], 12 U/kg/h [monotherapy]). The primary end point was Thrombolysis In Myocardial Infarction (TIMI) grade 3 epicardial flow at 60 min. RESULTS: In dose-finding, TIMI grade 3 flow rates were similar across groups (64% to 68%). Arterial patency was highest for eptifibatide 180/2/180 plus half-dose TNK (96%, p = 0.02 vs. eptifibatide 180/2/90 plus half-dose TNK). In dose-confirmation, this combination, compared with TNK monotherapy, tended to achieve more TIMI 3 flow (59% vs. 49%, p = 0.15), arterial patency (85% vs. 77%, p = 0.17), and ST-segment resolution (median 71% vs. 61%, p = 0.08) but was associated with more major hemorrhage (7.6% vs. 2.5%, p = 0.14) and transfusions (13.4% vs. 4.2%, p = 0.02). Intracranial hemorrhage occurred in 1.0%, 0.6%, and 1.7% of patients treated with any combination, eptifibatide 180/2/180 and half-dose TNK, and TNK monotherapy, respectively. CONCLUSIONS: Double-bolus eptifibatide (180/2/180) plus half-dose TNK tended to improve angiographic flow and ST-segment resolution compared with TNK monotherapy but was associated with more transfusions and non-cerebral bleeding. Further study is needed before this combination can be recommended for general use.  相似文献   
77.
Atrial septal defects, atrio-ventricular septal defects, ventricular septal defects and the persistent arterial duct are the most common congenital heart defects which may cause, in the presence of a significant left-to-right shunt, chronic volume overload of the heart and lead to the development of pulmonary arterial hypertension. Repair is indicated to avoid these complications and evolution to right-to-left shunting (Eisenmenger syndrome). Although the long-term results of surgical interventions in uncomplicated congenital heart defects were excellent, percutaneous techniques to repair the defects became a focus of attention. The persistent arterial duct, the secundum type atrial septal defect, and, more recently, the muscular and perimembranous ventricular septal defect are currently eligible for percutaneous closure. By avoiding a sternotomy or a thoracotomy, complaints of pain become exceptional and the duration of hospitalisation is shortened. Percutaneous closure is not only better tolerated than surgery, it may also imply favourable economical aspects.  相似文献   
78.
79.
BACKGROUND: Brain natriuretic peptide (BNP) levels have been used to assess clinical status and predict prognosis of patients with chronic heart failure (CHF). However, BNP levels can only be measured in specialized laboratories which has hampered its use in daily clinical practice. We compared a new, rapid, BNP assay with a conventional BNP measurement and evaluated the applicability to current practice by comparing it with standard clinical parameters. METHODS: BNP levels were determined in 78 stable CHF patients and 20 controls. The severity of CHF was assessed by determination of New York Heart Association functional class (NYHA), left ventricular ejection fraction (LVEF) and peak oxygen consumption (peak VO(2)), and these parameters were compared to BNP levels. RESULTS: Overall, rapid BNP assessment was highly correlated with the conventional BNP assay (r=0.95, P<0.0001). In the higher ranges (>200 pmol/l), however, correlation was less accurate, and tended to overestimate. BNP levels also strongly correlated with both NYHA class, LVEF and peak VO(2) (all P<0.001). A cut-off value for BNP of 20 pmol/l yielded a sensitivity of 91% and a specificity of 92% to detect the presence of left ventricular systolic dysfunction. CONCLUSIONS: Rapid measurement of BNP levels is comparable to conventional BNP measurement and strongly correlated to clinical tests that are currently used to stratify CHF patients. Wider use of this method may yield a reduction of costly and time-consuming clinical tests and may reduce the medical burden of CHF.  相似文献   
80.
BACKGROUND: Determination of ST-segment deviation (STdev) and its resolution (STR) by reperfusion strategies have become important tools in the assessment of patients with acute myocardial infarction (AMI). STdev has been measured at different time-points, i.e. at 20-80 ms after the J-point. There are no data comparing STR at different time-points. METHODS AND RESULTS: STdev was measured using a new computer-assisted workflow. The intraclass correlation coefficients (ICC) for validity and agreement vs. classical manual measurements (n=1020) were both 0.996 (p<0.0001). The reliability indices were 0.991 (95% CI 0.990-0.992) for the manual vs. 0.995 (95% CI 0.995-0.996) for the computer-assisted method, indicating superiority of the latter. 12-lead STdev were determined on ECGs before (baseline) and 180 min after start of thrombolytic therapy, measured both at the J-point (STdev(J)) and 20 ms after the J-point (STdev(J20); n=2400). STdev(J20) was on average 0.01+/-0.03 mV higher than STdev(J) (p<0.0001) with a tendency towards larger differences for higher ST-elevations (p<0.001). Although the average STR calculated from STdev(J20) and STdev(J) was not statistically different in any infarct location group, in 26% of the patients the difference was >10%, and 11% of the patients were classified into another ST-resolution group. Analysing STdev only in the single lead with the highest ST-elevation at baseline (a simplified measurement which may eliminate the confounding effect of ST-depressions) showed an even higher classification discordance (14% of the patients). CONCLUSIONS: The time-point of STdev measurement is an important variable to be accounted for when evaluating ST resolution data. Uncontrolled extrapolation of classification schemes based on STdev(J20) to other time-points cannot be justified.  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