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   3422篇
  免费   182篇
  国内免费   18篇
耳鼻咽喉   45篇
儿科学   120篇
妇产科学   107篇
基础医学   270篇
口腔科学   47篇
临床医学   335篇
内科学   898篇
皮肤病学   35篇
神经病学   344篇
特种医学   108篇
外科学   610篇
综合类   83篇
一般理论   1篇
预防医学   143篇
眼科学   92篇
药学   197篇
中国医学   9篇
肿瘤学   178篇
  2024年   4篇
  2023年   20篇
  2022年   60篇
  2021年   114篇
  2020年   79篇
  2019年   118篇
  2018年   136篇
  2017年   88篇
  2016年   103篇
  2015年   119篇
  2014年   163篇
  2013年   194篇
  2012年   273篇
  2011年   300篇
  2010年   148篇
  2009年   149篇
  2008年   229篇
  2007年   239篇
  2006年   203篇
  2005年   226篇
  2004年   178篇
  2003年   179篇
  2002年   141篇
  2001年   20篇
  2000年   15篇
  1999年   18篇
  1998年   18篇
  1997年   11篇
  1996年   8篇
  1995年   8篇
  1994年   6篇
  1993年   6篇
  1992年   7篇
  1991年   3篇
  1990年   2篇
  1989年   3篇
  1988年   4篇
  1987年   2篇
  1985年   2篇
  1983年   2篇
  1981年   3篇
  1980年   4篇
  1979年   4篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1972年   4篇
  1971年   1篇
  1970年   1篇
  1965年   1篇
排序方式: 共有3622条查询结果,搜索用时 15 毫秒
81.
BackgroundThis study compares two latest-generation self-expanding transcatheter heart valves (THV), the supra-annular ACURATE neo (Boston Scientific) and the intra-annular Centera THV (Edwards Lifesciences).MethodsIn this single center observational cohort trial 317 patients treated with the ACURATE neo and 78 patients treated with the Centera TVH were included. The main endpoints were device success and the early safety endpoint at 30 days.ResultsBesides higher incidence of diabetes mellitus and higher body mass index in patients treated with the ACURATE neo THV, there were no baseline differences between the groups. Device success was similar in both groups (neo: 91.8% vs. Centera: 93.6%; P=0.598), with numerically higher rates of moderate to severe paravalvular leakage in the ACURATE neo group (4.7% vs. 1.3%; P=0.214). At 30 days all-cause mortality rates were low in both groups (0.3% vs. 0%; P=0.620) and no difference occurred in the early safety at 30 days (19.3% vs. 16.7%; P=0.599). However, all-cause stroke rates were significantly higher in patients treated with the Centera THV (6.4 vs. 1.6%; P=0.015).ConclusionsThe ACURATE neo and the Centera THV show low mortality rates as well as comparable, favorable hemodynamics. The finding of higher stroke rates at 30 days with the repositionable Centera SE-THV needs further assessment.  相似文献   
82.
The purpose of this study was to compare the serum interleukin (IL)-23 levels between rheumatoid arthritis (RA) patients and healthy controls and to determine the correlation of IL-23 levels with disease activity, joint damage and functional disability in RA. Serum samples were obtained from 45 patients with RA and 45 healthy controls. The enzyme-linked immunosorbent assay method was used for quantitative analysis of IL-23. All the RA patients were assessed for disease activity based on the 28-joint disease activity score, joint damage based on modified Sharp score, and functional ability using the Health Assessment Questionnaire–Disability Index. The mean serum IL-23 level was much higher among the RA patients (24.50 ± 13.98 pg/mL) compared to the controls (5.98 ± 3.40 pg/mL; p < 0.01). There was a significant positive relationship between IL-23 levels and disease activity and questionnaire scores (p = 0.003 and 0.020, respectively). On logistic regression analysis, IL-23 levels were significantly higher in patients with moderate to high disease activity (p = 0.008, odds ratio = 1.073, 95% confidence interval = 1.019–1.130) and patients with significant functional disability (p = 0.008, odds ratio = 1.085, 95% confidence interval = 1.021–1.153). RA patients have significantly higher levels of serum IL-23. The IL-23 levels correlate well with disease activity and functional disability but not with radiographic joint damage.  相似文献   
83.
Improving the photon absorption in thin-film solar cells with plasmonic nanoparticles is essential for the realization of extremely efficient cells with substantial cost reduction. Here, a comprehensive study of solar energy enhancement in a cadmium telluride (CdTe) thin-film solar cell based on the simple design of a square array of plasmonic titanium nanoparticles, has been reported. The excitation of localized plasmons in the metallic nanostructures together with the antireflection coating (ARC) significantly enhances the absorption of photons in the active CdTe layer. The proposed structure attained super absorption with a mean absorbance of more than 97.27% covering a wide range from visible to near-infrared (i.e., from 300 nm to 1200 nm), presenting a 90% absorption bandwidth over 900 nm, and the peak absorption is up to 99.9%. For qualitative analysis, the photocurrent density is also estimated for AM 1.5 solar illumination (global tilt), whose value reaches 40.36 mA cm−2, indicating the highest value reported to date. The impact of nanoparticle dimensions, various metal materials, shapes, and random arrangement of nanoparticles on optical absorption are discussed in detail. Moreover, the angle insensitivity is essentially validated by examining the absorption performance with oblique incidences and it is found that the solar cell keeps high absorption efficiency even when the incidence angle is greater than 0°. Therefore, these findings suggest that the proposed broadband structure has good prospect in attaining high power conversion efficiency while reducing the device cost.

Improving the photon absorption in thin-film solar cells with plasmonic nanoparticles is essential for the realization of extremely efficient cells with substantial cost reduction.  相似文献   
84.
85.
ObjectiveThe association between uric acid and cardiovascular disease is poorly studied. We undertook this study to assess whether uric acid level predicts clinical outcome in patients with stable coronary artery disease (CAD) treated with percutaneous coronary intervention (PCI).Materials/MethodsThis study included 8149 patients with stable CAD who underwent PCI. Uric acid was measured before angiography. The primary end point was 1-year mortality. Quartiles of quartiles of uric acid were: 1.49 to < 5.49 mg/dl (1st quartile; n=2032 patients), 5.49 to < 6.40 mg/dl (2nd quartile; n=1981 patients), 6.40 to < 7.50 mg/dl (3rd quartile; n=2093 patients) and 7.50 to 21.90 mg/dl (4th quartile; n=2043 patients).ResultsThere were 196 deaths during the 1-year follow-up. The numbers of deaths (Kaplan-Meier estimates) according to uric acid quartiles were: 35 deaths (1.8%) in the 1st quartile, 30 deaths (1.6%) in the 2nd quartile, 45 deaths (2.2%) in the 3rd quartile and 86 deaths (4.3%) in the 4th quartile (unadjusted hazard ratio [HR]=1.60, 95% confidence interval [CI] 1.38-1.86, P < 0.001 for each standard deviation [SD] increase in the logarithmic scale). After adjustment for traditional cardiovascular risk factors, renal function and inflammatory status, the association between uric acid and 1-year mortality remained significant (adjusted HR=1.26, 95% CI 1.07-1.48; P=0.005 for each standard deviation increase in the logarithmic scale). Uric acid improved predictivity of the multivariable model regarding mortality (P=0.040).ConclusionsElevated level of uric acid is an independent predictor of 1-year mortality in patients with stable CAD treated with PCI.  相似文献   
86.
87.
The association between uric acid and cardiovascular disease is incompletely understood. In particular, the prognostic value of uric acid in patients with acute coronary syndromes who undergo percutaneous coronary intervention has not been studied. This study included 5,124 patients with acute coronary syndromes who underwent percutaneous coronary intervention: 1,629 with acute ST-segment elevation myocardial infarction, 1,332 with acute non-ST-segment elevation myocardial infarction, and 2,163 with unstable angina. The primary end point was 1-year mortality. Patients were divided into quartiles according to uric acid level as follows: quartile 1, 1.3 to <5.3 mg/dl; quartile 2, 5.3 to <6.3 mg/dl; quartile 3, 6.3 to <7.5 mg/dl; and quartile 4, 7.5 to 18.4 mg/dl. There were 450 deaths during follow-up: 80 deaths in quartile 1, 77deaths in quartile 2, 72 deaths in quartile 3, and 221 deaths in quartile 4 of uric acid (Kaplan-Meier estimates of 1-year mortality 6.4%, 6.2%, 5.6%, and 17.4%, respectively; unadjusted hazard ratio 3.05, 95% confidence interval 2.54 to 3.67, p <0.001 for fourth vs first quartile of uric acid). After adjustment for traditional cardiovascular risk factors, renal function, and inflammatory status, the association between uric acid and mortality remained significant, with a 12% increase in the adjusted risk for 1-year mortality for every 1 mg/dl increase in the uric acid level. Uric acid improved the discriminatory power of the predictive model regarding 1-year mortality (absolute integrated discrimination improvement 0.008, p = 0.005). In conclusion, elevated levels of uric acid are an independent predictor of 1-year mortality across the whole spectrum of patients with acute coronary syndromes treated with percutaneous coronary intervention.  相似文献   
88.
89.
90.
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