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   1361篇
  免费   74篇
  国内免费   4篇
耳鼻咽喉   21篇
儿科学   76篇
妇产科学   21篇
基础医学   147篇
口腔科学   93篇
临床医学   101篇
内科学   445篇
皮肤病学   10篇
神经病学   105篇
特种医学   57篇
外科学   99篇
综合类   39篇
预防医学   72篇
眼科学   42篇
药学   64篇
肿瘤学   47篇
  2021年   13篇
  2020年   6篇
  2019年   20篇
  2018年   23篇
  2017年   13篇
  2016年   18篇
  2015年   21篇
  2014年   27篇
  2013年   25篇
  2012年   54篇
  2011年   71篇
  2010年   26篇
  2009年   41篇
  2008年   58篇
  2007年   88篇
  2006年   79篇
  2005年   66篇
  2004年   66篇
  2003年   61篇
  2002年   61篇
  2001年   67篇
  2000年   57篇
  1999年   34篇
  1998年   19篇
  1997年   20篇
  1996年   10篇
  1995年   12篇
  1994年   10篇
  1993年   8篇
  1992年   30篇
  1991年   24篇
  1990年   24篇
  1989年   31篇
  1988年   27篇
  1987年   26篇
  1986年   36篇
  1985年   19篇
  1984年   16篇
  1983年   8篇
  1982年   18篇
  1981年   8篇
  1980年   10篇
  1979年   12篇
  1978年   7篇
  1976年   6篇
  1975年   5篇
  1974年   6篇
  1973年   6篇
  1972年   5篇
  1932年   4篇
排序方式: 共有1439条查询结果,搜索用时 187 毫秒
41.
The addition of epinephrine in dental local anaesthesia results in a longer and deeper anaesthesia under almost ischemic conditions. For short-time dental treatments, epinephrine-reduced anaesthetics may offer shorter and more individual anaesthesia with reduced potential side effects. The aim of this study was a clinical evaluation of anaesthetic potency and adverse effects of an epinephrine-reduced articaine formulation in dental patients undergoing short-time routine treatment. In a prospective clinical, not interventional, study between January 2008 and February 2009, 908 patients undergoing short-time dental treatment in five medical centers were anaesthetized with 4% articaine 1:400,000 epinephrine (Ubistesin, 3M/ESPE, Seefeld, Germany). Efficacy and safety in clinical use were evaluated. A follow-up after 1 day was conducted by telephone survey. A mean amount of 1.3-ml anaesthetic solution was needed to achieve a complete or sufficient anaesthesia in 97% (n = 876) of cases. A second injection had to be done in 3.7% (n = 34) before and in 11.9% (n = 108) during treatment. Here, the second injection had to be applied after a mean of 48.6 min. The mean duration of soft tissue anaesthesia after infiltration was 146.6 min, after nerve block 187.7 min. The painful treatment took a mean of 50.2 min and the total treatment time summed up to 68.8 min. In 1.7% cases (n = 15), unwanted side effects were observed. The results indicate that a lower concentration of epinephrine in combination with the 4% articaine solution leads to a high success rate of efficacy. The clinical use of a 4% articaine 1:400,000 epinephrine solution can be stated as safe and effective in short dental routine treatments. Reconsiderations concerning limitations of indication or additional contraindications are not necessary.  相似文献   
42.
Objective To explore the treatment, procedure related risks, and outcomes of patients older than 90 years of age undergoing cardiac catheterization. Methods We retrospectively studied 32 patients ≥ 90 years (93.0 ± 1.2 years) who underwent cardiac catheterisation in a tertiary specialist hospital (0.2% of 14,892 procedures during three years). The results were compared to a patient cohort younger than 90 years of age. Results Baseline characteristics revealed a higher prevalence of diabetes (P < 0.001), chronic obstructive pulmonary disease (P < 0.04), previous myocardial infarction (P < 0.02), and complex coronary anatomy (SYNTAX score 33 vs. 19) in nonagenarians. Patients < 90 years of age showed more hyperlipidemia (P < 0.01) and previous percutaneous coronary interventions (P < 0.015). Nonagenarians underwent coronary angiography more often for acute coronary syndrome (ACS) (P < 0.003), were presented more often in cardiogenic shock (P < 0.003), and were transferred faster to coronary angiography in cases of ACS (P < 0.0001). The observed in-hospital mortality rate (13% study group vs. 1% control group; P < 0.003) in nonagenarians was lower than the calculated rate of thrombolysis in myocardial infarction (TIMI) and global registry of acute cardiac events (GRACE) mortality and strongly influenced by the severity of clinical presentation and the presence of co-morbidities. Conclusions Despite the common scepticism that cardiac catheterisation exposes patients ≥ 90 years to an unwarranted risk, our data demonstrate an acceptable incidence of complications and mortality in this group of patients.  相似文献   
43.
Abstract

Background/Objective: Children with spinal cord injury (SCI) are at risk for musculoskeletal and cardiovascular complications. Stationary cycling using functional electrical stimulation (FES) or passive motion has been suggested to address these complications. The purpose of this case series is to report the outcomes of a 6-month at-home cycling program for 4 children with SCI.

Methods: Two children cycled with FES and 2 cycled passively at home for 1 hour, 3 times per week.

Outcome Measures: Data collected included bone mineral density of the left femoral neck, distal femur, and proximaltibia; quadriceps and hamstring muscle volume; stimulated quadriceps and hamstring muscle strength; a fasting lipid profile; and heart rate and oxygen consumption during incremental upper extremity ergometry testing.

Results: The 2 children cycling with FES and 1 child cycling passively exhibited improved bone mineral density, muscle volume, stimulated quadriceps strength, and lower resting heart rate. For the second child cycling passively, few changes were realized. Overall, the lipid results were inconsistent, with some positive and some negative changes seen.

Conclusions: This case series suggests that cycling with or without FES may have positive health benefits and was a practical home exercise option for these children with SCI.  相似文献   
44.
Induction of organ-selective CD4+ regulatory T cell homing   总被引:2,自引:0,他引:2  
Compelling evidence suggests that Foxp3+CD25+CD4+ Treg play a fundamental role in immunoregulation. We have previously demonstrated that Treg have to enter peripheral tissues to suppress ongoing inflammation. However, relatively little is known about how Treg acquire the expression of homing receptors required for tissue‐ or inflammation‐specific migration. Migratory properties of conventional naïve T cells are shaped by the tissue microenvironment and organ‐specific dendritic cells during priming. Here, we show that this basic concept also holds true for CD25+CD4+ Treg: Priming of Treg within peripheral LN led to the expression of selectin ligands, which facilitate migration into inflamed skin, whereas activation within mesenteric LN led to induction of the integrin α4β7, which is required for migration into mucosal tissues. Furthermore, we could establish in vitro culture systems containing either dendritic cells from mesenteric and peripheral LN, or retinoic acid and IL‐12 as polarizing compounds to induce mucosa‐ and skin‐seeking Treg, respectively. Together, our results demonstrate that Treg, similarly to conventional T cells, can be configured with organ‐selective homing properties allowing efficient targeting into distinct tissues.  相似文献   
45.

Background

Road safety has been receiving increased attention through the United Nations Decade of Action on Road Safety, and is also now specifically addressed in the sustainable development goals 3.6 and 11.2. In an effort to enhance the response to Road Traffic Injuries (RTIs), this paper aims to examine the cost effectiveness of proven preventive interventions and forms part of an update of the WHO-CHOICE programme.

Methods

Generalized cost-effectiveness analysis (GCEA) approach was used for our analysis. GCEA applies a null reference case, in which the effects of currently implemented interventions are subtracted from current rates of burden, in order to identify the most efficient package of interventions. A population model was used to arrive at estimates of intervention effectiveness. All heath system costs required to deliver the intervention, regardless of payer, were included. Interventions are considered to be implemented for 100 years. The analysis was undertaken for eastern sub-Saharan Africa and Southeast Asia.

Results

In Southeast Asia, among individual interventions, drink driving legislation and its enforcement via random breath testing of drivers at roadside checkpoints, at 80% coverage, was found to be the most cost-effective intervention. Moreover, the combination of “speed limits?+?random breath testing?+?motorcycle helmet use”, at 90% coverage, was found to be the most cost-effective package. In eastern sub-Saharan Africa, enforcement of speed limits via mobile/handheld cameras, at 80% coverage, was found to be the most cost-effective single intervention. The combination of “seatbelt use?+?motorcycle helmet use?+?speed limits?+?random breath testing” at 90% coverage was found to be the most cost-effective intervention package.

Conclusion

This study presents updated estimates on cost-effectiveness of practical, evidence-based strategies that countries can use to address the burden of RTIs. The combination of individual interventions that enforces simultaneously multiple road safety measures are proving to be the most cost-effective scenarios. It is important to note, however, that, in addition to enacting and enforcing legislation on the risk factors highlighted as part of this paper, countries need to have a coordinated, multi-faceted strategy to improve road safety.
  相似文献   
46.
The aim of this study was to assess the effects of residual stenosis after single-stent implantation on the rate of stent thrombosis, as well as restenosis within a 6-month follow-up period. Coronary angiograms of 2,157 patients with 2,523 lesions treated with a single stent were analyzed by quantitative coronary angiography before, immediately after stent implantation, and at a planned 6-month follow-up. Lesions were classified into 4 subgroups according to the degree of residual stenosis after stent implantation: group 1, gross oversizing <-15%; group 2, slight oversizing -15% to <0%; group 3, mild residual 0% to <15%; group 4, moderate residual 15% to <30%. Stent thrombosis rates were not significantly different among the 4 subgroups (group 1: 0 of 60 [0%]; group 2: 2 of 388 [0.5%]; group 3: 8 of 1,370 [0.6%]; group 4: 8 of 705 [1.1%]; p = NS for all). An adequate dosage of ticlopidine (250 mg twice daily) and aspirin (100 mg/day) led to a lower rate of stent thrombosis (6 of 2,189 cases) than inadequate dosages or missing therapy (12 of 343 cases). In 1,882 stenoses with angiographic follow-up (77.7%), gross oversizing of stents lead to a significantly higher increase of percent stenosis (p <0.001) associated with a higher restenosis rate (group 1: 34.7% vs groups 2, 3, and 4: 32.5%, 28.2%, and 29.6%, respectively). A multiple regression analysis was performed. Optimal results with regard to stent thrombosis and restenosis were achieved with mild residual stenoses between 0% and 15% after stent implantation. Oversizing of stents is no longer necessary with an adequate dosage of ticlopidine and aspirin.  相似文献   
47.
Effective allocation of medical resources in stable chest pain patients requires the accurate diagnosis of coronary artery disease and the stratification of future cardiac risk. We studied the relative predictive value for cardiac death of 3 commonly applied noninvasive strategies, clinical assessment, stress electrocardiography, and myocardial perfusion tomography, in a large, multicenter population of stable angina patients. The multicenter observational series comprised 7 community and academic medical centers and 8,411 stable chest pain patients. All patients underwent pretest clinical screening followed by stress (exercise 84% or pharmacologic 16%) electrocardiography and myocardial perfusion tomography. Risk-adjusted multivariable Cox proportional hazards models were developed to predict cardiac death. Kaplan-Meier rates of time to cardiac catheterization were also computed. Cardiac mortality was 3% during the 2.5 +/- 1.5 years of follow-up. The number of infarcted vascular territories and pretest clinical risk factors were strong predictors of cardiac mortality, whereas the number of ischemic vascular territories gained increasing importance when determining post-test resource use requirements (i.e., the decision to perform cardiac catheterization). Exertional ST-segment depression in a population with a high frequency of electrocardiographic abnormalities at rest was not a significant differentiator of cardiac death risk. Stable chest pain patients are accurately identified as being at high risk for near-term cardiac events by both physicians' screening clinical evaluation and by the results of stress myocardial perfusion imaging. Disease management strategies for stable chest pain patients aimed at risk reduction should incorporate knowledge of relevant end points in treatment and guideline development.  相似文献   
48.
Hyperdiploidy (greater than 50 chromosomes, or a DNA index greater than 1.16) confers a favorable prognosis in B-lineage acute lymphoblastic leukemia of childhood. Children with B-lineage acute lymphoblastic leukemia whose lymphoblasts at diagnosis accumulate high levels of methotrexate (MTX) and MTX polyglutamates (MTXPGs) in vitro experience a better event-free survival than those whose lymphoblasts do not (Blood 76:44, 1990). Lymphoblasts from 13 children with hyperdiploidy (greater than 50 chromosomes) accumulated high levels of MTX-PGs (1,095 and 571 to 2,346 pmol/10(9) cells [median and 25% to 75% intraquartile range]). These levels were higher than those in B-lineage lymphoblasts from 19 children with other aneuploidy (326 and 159 to 775 pmol/10(9) cells) and 15 children with diploidy (393 and 204 to 571 pmol/10(9) cells) (P = .0015). Chromosomal trisomies in hyperdiploid cases were highly nonrandom. Chromosome 9 was not one of the chromosomes involved in trisomies, even though this chromosome contains the gene for folate polyglutamate synthetase, which is the enzyme required for MTXPG synthesis. The correlation between MTXPG level and percentage of S-phase cells was weak, suggesting that increased levels of MTXPGs could not be attributed to elevated proportions of cells in active DNA synthesis. The ability of hyperdiploid lymphoblasts to accumulate high levels of MTXPGs may increase their sensitivity to MTX cytotoxicity, accounting in part for the improved outlook for hyperdiploid patients treated with regimens that emphasize MTX as a primary component of continuation therapy.  相似文献   
49.
50.
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