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   4311篇
  免费   191篇
  国内免费   12篇
耳鼻咽喉   103篇
儿科学   193篇
妇产科学   210篇
基础医学   675篇
口腔科学   45篇
临床医学   257篇
内科学   948篇
皮肤病学   69篇
神经病学   382篇
特种医学   69篇
外科学   190篇
综合类   27篇
预防医学   359篇
眼科学   112篇
药学   580篇
中国医学   14篇
肿瘤学   281篇
  2024年   2篇
  2023年   24篇
  2022年   157篇
  2021年   302篇
  2020年   104篇
  2019年   134篇
  2018年   142篇
  2017年   129篇
  2016年   152篇
  2015年   154篇
  2014年   200篇
  2013年   285篇
  2012年   359篇
  2011年   369篇
  2010年   196篇
  2009年   147篇
  2008年   234篇
  2007年   304篇
  2006年   273篇
  2005年   255篇
  2004年   188篇
  2003年   184篇
  2002年   143篇
  2001年   12篇
  2000年   4篇
  1999年   4篇
  1998年   5篇
  1997年   10篇
  1996年   7篇
  1995年   4篇
  1992年   3篇
  1988年   4篇
  1985年   3篇
  1981年   3篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1970年   2篇
  1969年   4篇
  1968年   1篇
  1966年   3篇
  1965年   1篇
  1960年   1篇
排序方式: 共有4514条查询结果,搜索用时 31 毫秒
51.
52.
Background: Atopic dermatitis (AD) is a chronic, relapsing skin disorder which is strictly determined by the epidermal barrier function. In previous studies, there is conclusive evidence that normal‐looking, nonlesional skin presents meaningful barrier function defect and a sub‐clinical eczematous skin reaction. Aim: The authors intended to visualize nonlesional AD skin with the use of high frequency ultrasonography to show that the normal‐looking, nonlesional skin may present significant abnormalities in USG examination. Methods: We have performed analysis with the use of high‐frequency 20 MHz skin sonography in the cases of 15 AD patients of the Department of Dermatology, Medical University, Poznań, Poland. The clinical score has been evaluated on the basis of W‐AZS index and EASI. The results were presented in the form of ultrasonographic images. Results: High frequency ultrasonography revealed an echopoor band within nonlesional skin of six (40%) examined AD patients and in all cases within skin lesions. Conclusion: Our results indicate the significant role of skin ultrasonography in the complete clinical evaluation of patients with AD, which may serve as an element in selection of the most appropriate topical treatment. An echopoor band beneath the echo entry within nonlesional skin of some AD patients may reflect subclinical eczematous reaction and the readiness for the development of typical skin lesions. For this purpose, we suggest to name an intact skin in AD as seemingly healthy skin.  相似文献   
53.
54.
55.
BACKGROUND: Cardiac resynchronisation therapy (CRT) has become a valuable therapeutic tool in patients with advanced chronic heart failure (CHF). The search for optimal methods for the assessment of CRT efficacy is still underway. AIM: To evaluate the impact of implantation of CRT devices in patients with CHF on adaptation of circulatory and respiratory systems to maximal exercise assessed by cardiopulmonary exercise tests (CPX) and 6-minute walking tests (6MWT). METHODS: We investigated 27 patients (22 males, 5 females, 61.2+/-9.1 years) with a CRT device implanted due to advanced CHF, which resulted from ischaemic or dilated cardiomyopathy. All patients before implantation underwent echocardiography, CPX with expired gas analysis and 6MWT. Investigations were repeated at 3-6 months after CRT implantation. In CPX we evaluated peak oxygen uptake (peak VO2), oxygen pulse, maximal minute ventilation-carbon dioxide production (VE/VCO2 (max)), and its slope (VE/VCO2 slope) and VE/VO2 slope, VO2 in anaerobic threshold (AT), and cardiac and respiratory reserve. In 6MWT we evaluated walking distance and heart rate and blood pressure response to exercise. RESULTS: We noted statistically higher mean peak VO2 after CRT implantation in the studied group: 11.34+/-3.38 vs. 14.56+/-3.99 ml/kg/min (p<0.0001) and 1.01 +/-0.44 vs. 1.4+/-0.55 l/min (p=0.003) and higher values of expired CO2: 1.00+/-0.43 vs. 1.43+/-0.67 l/min (p=0.004). The O2 pulse rose from 9.65+/-3.39 to 13.23+/-5.43 ml/beat (p=0.015). We also observed a significant reduction of VE/VCO2 slope from 42.34+/-13.35 before CRT to 34.77+/-6.04 after CRT (p=0.0196) and a significant decrease of VE/VO2 slope from 41.32 +/-15.46 to 34.01+/-6.27 (p=0.037). VE/VCO2 (max) fell from 58.02+/-15.86 to 50.1+/-13.14 (p=0.009). Patients estimated their dyspnoea on the Borg scale at peak exercise at 4.75+/-0.75 points before CRT and at 3.67+/-1.15 points (p=0.002) after CRT. Patients could walk a longer distance during 6MWT than before CRT (367+/-154.9 vs. 231.1+/-170.3 m, p<0.001). CONCLUSIONS: Cardiac resynchronisation therapy improves exercise tolerance measured by means of CPX and 6MWT, improves respiratory system efficiency and restores its adaptive mechanisms during exercise in patients with advanced CHF. Better exercise adaptation after CRT may be objectively measured with CPX parameters, and correlates with improvement of clinical symptoms. CPX seems to be a very helpful tool in assessing the results of CRT.  相似文献   
56.
Aim of this prospective study was to assess quality of life (QoL), left ventricular (LV) function and exercise performance in two groups of patients (pts) with atrial fibrillation (Af) treated with: radiofrequency catheter ablation (RFA) and antiarrhythmic drugs (AA). Between 1996 and 2000 - 74 patients, 28 women, with drug refractory Af were enrolled by clinical indications for two modes of therapy: RFA and AA. RFA group consisted of 38 pts, 63.7 +/- 11.5 years old: 28 pts with RF AV Node ablation and pacemaker implantation (PI) and 10 pts with AV Node modification or right atrial isthmus RF ablation due to Af conversion to atrial flutter (Aflu) during medical therapy. AA group consisted of 36 pts, aged 59.7 +/- 13.8 years. Patients from RFA group suffered significantly more serious diseases than pts from AA group. No significant (sign.) differences between two groups were found in age, gender, arrhythmia history and number of AA taken. Pts were analyzed before entry, after 3 and 12 months of follow-up (3 mo. FU, 12 mo. FU) with following indices: LV function (Echo: EF & FS), exercise performance (treadmill test), QoL questionnaires, number of hospital admissions connected to arrhythmia or procedures (RFA & PI), number of AA drugs taken in RFA group. RFA group: Two deaths occurred due to end stage respiratory insufficiency (COPD), one pt required reposition of pacemaker lead. AA group: 3 pts required RFA due to uncontrolled Af/Aflu (AV Node ablation with PI - 1 pt, right atrial isthmus ablation - 2 pts). Analysis of two patients groups: LV function: Sign. improvement (EF & FS) in both groups in 12 mo. FU; Exercise performance: no sign. changes in 3 and 12 mo. FU. QoL: Arrhythmia scale: 3 mo. FU sign. reduction in both groups; 12 mo. FU reduction in RFA group only; Anxiety scale: 3 and 12 mo. FU sign. reduction of anxiety level in RFA group; Exercise and activity scales: 3 and 12 mo. FU sign. improvement in RFA group. During 3 and 12 mo. FU sign. less pts from RFA group required hospital admission versus pts from AA group. Sign. reduction in AA was noted in RFA group. Patients with symptomatic Af treated with RFA benefit from this kind of therapy more than patients treated with AA. Quality of life improvement visible in short term observation in patients from RFA group is still present after one year observation. Improvement in LV function is observed after one year in both groups of pts with Af.  相似文献   
57.
Infections caused by the spirochete Borrelia burgdorferi sensu lato may be accompanied by other microorganisms, such as Anaplasma, Ehrlichia and Babesia. These pathogens are transmitted by the ticks and are a risk to humans and animals. Ixodes ricinus ticks collected from recreational areas of Szczecin and northwestern Poland contained DNA of the pathogens mentioned above and cases of double and triple coinfection have been documented. The aim of this paper was to determine if dogs suspect to tick infestation in the area of study are a reservoir for these pathogens and to examine the possibility of coinfection. Canine blood was sampled, part of the material originated from dogs exhibiting symptoms of borreliosis. In an earlier study, the samples were screened for DNA from B. burgdorferi sensu lato. In order to screen for A. phagocytophila and Babesia sp. DNA, a PCR-based method was used with the following primers: EHR521/EHR747 for Anaplasma and FOR1/REV1 for Babesia. In 192 samples only two contained A. phagocytophila DNA. One of these samples originated from a healthy canine, the other from an individual with symptoms of borreliosis. The examined samples were not positive for Babesia sp. DNA. Coinfection was not discovered. The low level of A. phagocytophila infection may indicate that the domestic dog is not a reservoir for Anaplasma and Babesia in Szczecin and northwestern Poland. Moreover, this area does not have populations of the brown dog tick (Rhipicephalus sanguineus) or Dermacentor reticulates--both of which are vectors of E. canis and B. canis and commonly induce ehrlichiosis and babesiosis in canines.  相似文献   
58.
59.
Here we report a patient with 11p15.4p15.5 duplication and 13q34 deletion presenting with Beckwith–Wiedemann syndrome (BWS) and moderate deficiency of factor VII (FVII). The duplication was initially diagnosed on methylation‐sensitive multiplex ligation‐dependent probe amplification. Array comparative genome hybridization confirmed its presence and indicated a 13q34 distal deletion. The patient's clinical symptoms, including developmental delay and facial dysmorphism, were typical of BWS with paternal 11p15 trisomy. Partial 13q monosomy in this patient is associated with moderate deficiency of FVII and may also overlap with a few symptoms of paternal 11p15 trisomy such as developmental delay and some facial features. To our knowledge this is the first report of 11p15.4p15.5 duplication associated with deletion of 13q34 and FVII deficiency. Moreover, this report emphasizes the importance of detailed clinical as well as molecular examinations in patients with BWS features and developmental delay.  相似文献   
60.
AIMS: Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a nuclear receptor regulating cardiac metabolism that also has anti-inflammatory properties. Since the activation of inflammatory signalling pathways is considered to be important in cardiac hypertrophy and fibrosis, it is anticipated that PPARalpha modulates cardiac remodelling. Accordingly, in this study the hypothesis was tested that the absence of PPARalpha aggravates the cardiac hypertrophic response to pressure overload. METHODS AND RESULTS: Male PPARalpha-/- and wild-type mice were subjected to transverse aortic constriction (TAC) for 28 days. TAC resulted in a more pronounced increase in ventricular weight and left ventricular (LV) wall thickness in PPARalpha-/- than in wild-type mice. Compared with sham-operated mice, TAC did not affect cardiac function in wild-type mice, but significantly depressed LV ejection fraction and LV contractility in PPARalpha-/- mice. Moreover, after TAC mRNA levels of hypertrophic (atrial natriuretic factor, alpha-skeletal actin), fibrotic (collagen 1, matrix metalloproteinase-2), and inflammatory (interleukin-6, tumour necrosis factor-alpha, cyclo-oxygenase-2) marker genes were higher in PPARalpha-/- than in wild-type mice. The mRNA levels of genes involved in fatty acid metabolism (long-chain acyl-CoA synthetase, hydroxyacyl-CoA dehydrogenase) were decreased in PPARalpha-/- mice, but were not further compromised by TAC. CONCLUSION: The present findings show that the absence of PPARalpha results in a more pronounced hypertrophic growth response and cardiac dysfunction that are associated with an enhanced expression of markers of inflammation and extracellular matrix remodelling. These findings indicate that PPARalpha exerts salutary effects during cardiac hypertrophy.  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