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   2442篇
  免费   158篇
  国内免费   18篇
耳鼻咽喉   7篇
儿科学   42篇
妇产科学   34篇
基础医学   267篇
口腔科学   50篇
临床医学   167篇
内科学   598篇
皮肤病学   25篇
神经病学   242篇
特种医学   122篇
外科学   316篇
综合类   3篇
预防医学   247篇
眼科学   52篇
药学   166篇
中国医学   8篇
肿瘤学   272篇
  2024年   6篇
  2023年   41篇
  2022年   99篇
  2021年   172篇
  2020年   87篇
  2019年   113篇
  2018年   106篇
  2017年   89篇
  2016年   88篇
  2015年   119篇
  2014年   109篇
  2013年   139篇
  2012年   192篇
  2011年   175篇
  2010年   105篇
  2009年   101篇
  2008年   129篇
  2007年   134篇
  2006年   118篇
  2005年   88篇
  2004年   100篇
  2003年   62篇
  2002年   55篇
  2001年   19篇
  2000年   19篇
  1999年   18篇
  1998年   16篇
  1997年   3篇
  1996年   9篇
  1995年   6篇
  1994年   2篇
  1993年   8篇
  1992年   18篇
  1991年   8篇
  1990年   6篇
  1989年   10篇
  1988年   7篇
  1987年   3篇
  1986年   3篇
  1985年   6篇
  1984年   2篇
  1977年   2篇
  1976年   3篇
  1974年   1篇
  1973年   3篇
  1972年   4篇
  1971年   3篇
  1970年   1篇
  1969年   4篇
  1968年   4篇
排序方式: 共有2618条查询结果,搜索用时 15 毫秒
1.
2.
Laparoscopic colectomy is a difficult procedure with a long learning curve. We describe in this study our technique for right- and left-sided laparoscopic medial-to-lateral colectomy. The medial approach involves division of the vascular pedicle first, followed by mobilization of the mesentery toward the abdominal wall, and finally freeing of the colon along the white line of Toldt. This approach allows immediate identification of the plane between the mesocolon and the retroperitoneum and renders the dissection fast and safe. Our series of 50 consecutive laparoscopic colectomies supports this concept. We believe that surgeons familiar with this technique will have an important tool in their armamentarium to circumvent some of the challenges of laparoscopic colectomy.  相似文献   
3.
In dual-modality PET/CT systems, the CT scan provides the attenuation map for PET attenuation correction. The current clinical practice of obtaining a single helical CT scan provides only a snapshot of the respiratory cycle, whereas PET occurs over multiple respiratory cycles. Misalignment of the attenuation map and emission image because of respiratory motion causes errors in the attenuation correction factors and artifacts in the attenuation-corrected PET image. To rectify this problem, we evaluated the use of cine CT, which acquires multiple low-dose CT images during a respiratory cycle. We evaluated the average and the intensity-maximum image of cine CT for cardiac PET attenuation correction. METHODS: Cine CT data and cardiac PET data were acquired from a cardiac phantom and from multiple patient studies. The conventional helical CT, cine CT, and PET data of an axially translating phantom were evaluated with and without respiratory motion. For the patient studies, we acquired 2 cine CT studies for each PET acquisition in a rest-stress (13)N-ammonia protocol. Three readers visually evaluated the alignment of 74 attenuation image sets versus the corresponding emission image and determined whether the alignment provided acceptable or unacceptable attenuation-corrected PET images. RESULTS: In the phantom study, the attenuation correction from helical CT caused a major artifactual defect in the lateral wall on the PET image. The attenuation correction from the average and from the intensity-maximum cine CT images reduced the defect by 20% and 60%, respectively. In the patient studies, 77% of the cases using the average of the cine CT images had acceptable alignment and 88% of the cases using the intensity maximum of the cine CT images had acceptable alignment. CONCLUSION: Cine CT offers an alternative to helical CT for compensating for respiratory motion in the attenuation correction of cardiac PET studies. Phantom studies suggest that the average and the intensity maximum of the cine CT images can reduce potential respiration-induced misalignment errors in attenuation correction. Patient studies reveal that cine CT provides acceptable alignment in most cases and suggest that the intensity-maximum cine image offers a more robust alternative to the average cine image.  相似文献   
4.
Object recognition is one of the most important functions of the human visual system, yet one of the least understood, this despite the fact that vision is certainly the most studied function of the brain. We understand relatively well how several processes in the cortical visual areas that support recognition capabilities take place, such as orientation discrimination and color constancy. This paper proposes a model of the development of object recognition capability, based on two main theoretical principles. The first is that recognition does not imply any sort of geometrical reconstruction, it is instead fully driven by the two dimensional view captured by the retina. The second assumption is that all the processing functions involved in recognition are not genetically determined or hardwired in neural circuits, but are the result of interactions between epigenetic influences and basic neural plasticity mechanisms. The model is organized in modules roughly related to the main visual biological areas, and is implemented mainly using the LISSOM architecture, a recent neural self-organizing map model that simulates the effects of intercortical lateral connections. This paper shows how recognition capabilities, similar to those found in brain ventral visual areas, can develop spontaneously by exposure to natural images in an artificial cortical model.  相似文献   
5.
Several lines of evidence from neuroimaging, pharmacology and genetics support the involvement of the dopaminergic system in the etiology of Attention Deficit Hyperactivity Disorder (ADHD). Previous candidate gene studies have investigated the association between a dinucleotide (CA)n repeat polymorphism, located 18.5 kb from the start codon of the DRD5 gene, and ADHD. Association between the 148 bp allele and ADHD has been reported in some studies, however replication of the finding has not been consistent. We tested for an association between the (CA)n repeat and adult ADHD in a sample comprised of 119 families with adult ADHD probands and 88 unrelated adult ADHD cases with a corresponding number of controls matched for age, ethnicity and sex. In the family sample we found a non-significant trend for association between the 148 bp allele and ADHD (Z = 1.91, p = 0.055). An excess of non-transmissions was detected for the 150 and 152 bp alleles (Z = −2.26, p = 0.023; Z = −2.20, p = 0.028). Quantitative analysis performed using the Brown Attention Deficit Disorder Scale (BADDS) showed association between the 150 bp allele and lower total score (p = 0.011), and lower effort (p = 0.008), activation (p = 0.008) and attention (p = 0.01) cluster scores. We did not replicate association findings in the case–control group, likely due to the lack of statistical power of this sample. Our findings add to the literature suggesting DRD5 (CA)n repeat has a modest effect in modulating susceptibility to adult ADHD but further studies are required.  相似文献   
6.
Voluntary and forced exercise decrease morbidity and mortality in laboratory animals. Caloric restriction has similar effects on health and unique benefits on life span. Nonetheless, in most experiments, animals do not have access to physical activity and are fed ad libitum (AL). We hypothesized that with regular access to either unlimited running wheel exercise (EX) or limited physical activity (PA), key biomarkers of health would be enhanced enough to counter some consequences of a sedentary AL lifestyle. This 16-month study compared body weight, tumor number and size, tissue lesions, oxidative stress, and reactive stress in (1) sedentary animals with no access to physical activity (SED); (2) animals with access to hour-long, twice weekly activity in a large box (PA); and (3) animals with access every other day to a running wheel (EX). At the end of the study, EX body weight was 8-9% lower than PA and SED. In addition, EX had no kidney lesions versus 50% in PA and SED, and had smaller tumor size (10+/-2 vs. 14+/-4 and 30+/-4 mm). Exhaustive exercise lowered glutathione/oxidized glutathione ratio in EX and PA, but in SED, the ratio was depressed even in resting animals. In all treatments, prolactin (PRL) levels were lower in resting animals than in acutely exercised animals. In conclusion, EX had the most favorable health biomarkers while SED had the least. PA did not confer gross health benefits different than the SED group, but was biochemically more similar to EX animals.  相似文献   
7.
8.
Background: SARC-F and Mini Sarcopenia Risk Assessment (MSRA) questionnaires have been proposed as screening tools to identify patients at risk of sarcopenia. The aim of this study is to test the use of SARC-F and MSRA, alone and combined, as a pre-screening tool for sarcopenia in geriatric inpatients. Methods: 152 subjects, 94 men and 58 women, aged 70 to 94, underwent muscle mass evaluation by dual energy X-ray absorptiometry (DXA), muscle strength evaluation by handgrip, and completed the MSRA, SARC-F and Activity of daily living (ADL) questionnaires. Results: 66 subjects (43.4%) were classified as sarcopenic according to the European Working Group on Sarcopenia in Older People 2 (EWGSOP2) criteria. The 7-item SARC-F and MRSA and 5-item MSRA showed an area under the curve (AUC) of 0.666 (95% confidence interval (CI): 0.542–0.789), 0.730 (95% CI: 0.617–0.842) and 0.710 (95% CI: 0.593–0.827), respectively. The optimal cut-off points for sarcopenia detection were determined for each questionnaire using the Youden index method. The newly calculated cut-off points were ≤25 and ≤40 for MSRA 7- and 5-items, respectively. The ideal cut-off for the SARC-F was a score ≥3. Applying this new cut-off in our study population, sensitivity and specificity of the 7-item MSRA were 0.757 and 0.651, and 0.688 and 0.679 for the 5-item MSRA, respectively. Sensitivity and specificity of SARC-F were 0.524 and 0.765, respectively. The combined use of the 7-item SARC-F and MSRA improved the accuracy in sarcopenia diagnosis, with a specificity and sensitivity of 1.00 and 0.636. Conclusion: 7-item SARC-F and MSRA may be co-administered in hospital wards as an easy, feasible, first-line tool to identify sarcopenic subjects.  相似文献   
9.
BACKGROUND: AbobotulinumtoxinA (AboBoNT-A; Dysport®; Ipsen, Boulogne-Billancourt, France/Azzalure®; Galderma, Lausanne, Switzerland) is a botulinum neurotoxin type A approved for aesthetic use in the treatment of glabellar lines in adult patients under 65 years in Europe, the United States, and other countries. OBJECTIVE: We sought to analyze current literature on patient satisfaction with aboBoNT-A for upper facial aesthetic indications. METHODS: A systematic review of literature databases (PubMed/MEDLINE, Embase, the Cochrane Library, and Google Scholar) was performed to identify English-language publications reporting on patients with aesthetic indications (including glabellar lines and wrinkles) receiving aboBoNT-A, that assessed patient and/or physician satisfaction with treatment, with no restrictions on comparator studies. Structured data extraction was used to enable inter-study analysis. A post-hoc analysis was also performed to assess patient satisfaction by sex and age, using results from the noninterventional APPEAL study of patients’ satisfaction with aboBoNT-A for treating glabellar lines. RESULTS: Overall, 22 original research papers were identified. Patient satisfaction rates for aboBoNT-A treatment were significantly higher versus placebo from two weeks to between three and five months postinjection. At two to three weeks postinjection, patient satisfaction rates were 52% and 99% across studies. In studies with later time points, patient satisfaction rates were 85 to 87 percent at 5 months and between 25 and 100 percent at 6 months post-injection. Physician satisfaction was also high (97%–100%, across three treatments). No notable differences in patient satisfaction by sex or age were observed in the APPEAL study. CONCLUSION: High rates of patient satisfaction have been achieved with aboBoNT-A treatment for upper facial aesthetic indications. Despite the current recommended interval of ≥12 weeks, satisfaction with the aesthetic results of aboBoNT-A therapy is still evident up to 6 months post-injection in some patients.  相似文献   
10.
Influenza is a disease responsible for thousands of deaths every year. Although healthcare workers (HCWs) represent a way of contagion for patients, vaccination coverage among them is low. Mandatory vaccination has been proposed, but controversies remain. This systematic review and meta-analysis aimed to assess the acceptance of mandatory vaccination by HCWs, and to investigate associated characteristics. MEDLINE, Scopus, Embase, PsycInfo, CINAHL and Web of Science were used to search for studies assessing the topic. PRISMA statements were followed. Of the 13,457 univocal records found, 52 studies were included in the systematic review and 40 in the meta-analysis. The pooled proportion of HCWs accepting the policy was of 61% (95% CI: 53%- 68%) but with great heterogeneity between continents (from 54% in Europe to 69% in Asia) and in different professionals (from 40% in nurses to 80% in students). Vaccinated HCWs agreed more frequently with mandatory vaccination than non-vaccinated ones. More studies that consider mandatory vaccination acceptance as the main outcome are needed, but the results of this study confirm that in some settings the majority of HCWs favour mandatory vaccination. This, combined with effects that a flu epidemic could have if overlapped to pandemics with similar symptoms, requires renewed considerations on mandatory vaccination.  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