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   1613672篇
  免费   126271篇
  国内免费   5384篇
耳鼻咽喉   20997篇
儿科学   52191篇
妇产科学   45188篇
基础医学   229713篇
口腔科学   42374篇
临床医学   143831篇
内科学   326911篇
皮肤病学   38286篇
神经病学   134630篇
特种医学   59802篇
外国民族医学   567篇
外科学   236111篇
综合类   36866篇
现状与发展   9篇
一般理论   540篇
预防医学   128783篇
眼科学   35679篇
药学   114078篇
  14篇
中国医学   4897篇
肿瘤学   93860篇
  2021年   14630篇
  2019年   15402篇
  2018年   23235篇
  2017年   17155篇
  2016年   18777篇
  2015年   21232篇
  2014年   28263篇
  2013年   41643篇
  2012年   59925篇
  2011年   62493篇
  2010年   35532篇
  2009年   32567篇
  2008年   56698篇
  2007年   59947篇
  2006年   59546篇
  2005年   58034篇
  2004年   54758篇
  2003年   51822篇
  2002年   49665篇
  2001年   77175篇
  2000年   78977篇
  1999年   65618篇
  1998年   18071篇
  1997年   16408篇
  1996年   16437篇
  1995年   15585篇
  1994年   14050篇
  1993年   13134篇
  1992年   48186篇
  1991年   45560篇
  1990年   43506篇
  1989年   41424篇
  1988年   38001篇
  1987年   37037篇
  1986年   34481篇
  1985年   32755篇
  1984年   24891篇
  1983年   20954篇
  1982年   12742篇
  1981年   11223篇
  1979年   21619篇
  1978年   15236篇
  1977年   12723篇
  1976年   11870篇
  1975年   12263篇
  1974年   14787篇
  1973年   14352篇
  1972年   13382篇
  1971年   12191篇
  1970年   11595篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.

Purpose

Chest wall pain is an uncommon but bothersome late complication following lung stereotactic body radiation therapy. Despite numerous studies investigating predictors of chest wall pain, no clear consensus has been established for a chest wall constraint. The aim of our study was to investigate factors related to chest wall pain in a homogeneous group of patients treated at our institution.

Patients and methods

All 122 patients were treated with the same stereotactic body radiation therapy regimen of 48 Gy in three fractions, seen for at least 6 months of follow-up, and planned with heterogeneity correction. Chest wall pain was scored according to the Common Terminology Criteria for Adverse Events classification v3.0. Patient (age, sex, diabetes, osteoporosis), tumour (planning target volume, volume of the overlapping region between planning target volume and chest wall) and chest wall dosimetric parameters (volumes receiving at least 30, 40, and 50 Gy, the minimal doses received by the highest irradiated 1, 2, and 5 cm3, and maximum dose) were collected. The correlation between chest wall pain (grade 2 or higher) and the different parameters was evaluated using univariate and multivariate logistic regression.

Results

Median follow-up was 18 months (range: 6–56 months). Twelve patients out of 122 developed chest wall pain of any grade (seven with grade 1, three with grade 2 and two with grade 3 pain). In univariate analysis, only the volume receiving 30 Gy or more (P = 0.034) and the volume of the overlapping region between the planning target volume and chest wall (P = 0.038) significantly predicted chest wall pain, but these variables were later proved non-significant in multivariate regression.

Conclusion

Our analysis could not find any correlation between the studied parameters and chest wall pain. Considering our present study and the wide range of differing results from the literature, a reasonable conclusion is that a constraint for chest wall pain is yet to be defined.  相似文献   
92.
文题释义:肱骨近端骨折:肱骨近端包括肱骨头及大结节、小结节,中老年人骨质疏松及低能量损伤可导致肱骨近端骨折。 同种异体腓骨:取自于人体异体,经过加工处理,去除其免疫原性,保留其骨性结构,可用于移植修复骨缺损,起到支撑作用。 背景:肱骨近端骨折是临床常见骨折,但对肱骨近端内侧柱缺乏支撑的骨折目前仍是治疗难点,并发症常见,失败率较高。 目的:比较解剖锁定钢板联合同种异体腓骨与单纯解剖锁定钢板治疗肱骨近端骨折的疗效。 方法:使用计算机检索PubMed、Embase、Cochrane Library、Google Scholar、中国知网、万方、维普数据库,检索时间均从建库到2020年2月。检索国内外关于对比研究解剖锁定钢板联合同种异体腓骨与单纯解剖锁定钢板治疗肱骨近端骨折疗效的文献。2名研究员根据纳入和排除标准分别独立筛选文献,提取数据,评估文献中的偏倚风险。纳入12篇相关文献使用RevMan 5.2软件将以下指标进行Meta分析,包括影像学数据、功能评分和并发症。结果与结论:①通过文献检索、根据纳入和排除标准,12篇文献纳入研究,其中11篇为回顾性队列研究,1篇为随机对照研究;纳入研究文献质量高,但GRADE证据质量级别较低。②共纳入958例患者,其中解剖锁定钢板联合同种异体腓骨组411例,单纯解剖锁定钢板组547例;③Meta分析结果显示,解剖锁定钢板联合同种异体腓骨组术后1年肱骨头高度差值(MD=-2.40,95%CI:-2.49至-2.31)、颈干角差值(MD= -6.14,95%CI:-6.62至-5.67)、目测类比评分(MD=-0.22,95%CI:-0.35至-0.08)、肩关节功能评分(MD=4.12,95%CI:2.18-6.06),上肢伤残评分(MD=-10.32,95%CI:-13.44至-7.19)、术后2年的目测类比评分(MD=-0.37,95%CI:-0.55至-0.19)、肩关节功能评分(MD=5.07,95%CI:2.86-7.27)、总体并发症(OR=0.31,95%CI:0.20-0.48)及肱骨头螺钉切出(OR=0.25,95%CI:0.11-0.55)均明显优于单纯解剖锁定钢板组(P < 0.05),肱骨头坏死(OR=0.94,95%CI:0.47-1.88),两组间差异无显著性意义(P > 0.05);④因此,较弱的证据提示,肱骨近端解剖锁定钢板联合同种异体腓骨治疗肱骨近端骨折的短期疗效优于解剖锁定钢板,可减少并发症的发生,促进功能恢复。ORCID: 0000-0002-8486-3932(阳运康) 中国组织工程研究杂志出版内容重点:人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程  相似文献   
93.
Porocarcinoma is an unusual, locally aggressive and potentially fatal neoplasm. Several cutaneous malignancies have been described in association with porocarcinoma, including squamous cell carcinoma, basal cell carcinoma and tricholemmal carcinoma. Previous reports have indicated that the occurrence of malignant tumours in combination with porocarcinoma is extremely rare, in particular with regard to Bowen disease (BD). We report an uncommon case of porocarcinoma occurring synchronously in a single BD lesion in a 63‐year‐old woman with multiple BD lesions. The clinical and histological findings confirmed this diagnosis.  相似文献   
94.
Children who expect they can bring about good outcomes and avoid bad outcomes tend to experience more personal successes. Little is known about factors that contribute to these ‘control expectancies’. The purpose of the present study was to determine whether children's internal control expectancies occur in the context of parents’ internal control expectancies, low family strain, and high family cohesiveness and whether these factors are more strongly related to daughters’ than sons’ control expectancies. A community sample of 85 children aged 9–11 years and their parents (85 mothers; 63 fathers) completed rating scales. Fathers’ more internal control expectancies and mothers’ reports of fewer family strains were associated with daughters’ but not sons’ greater internal control expectancies, and greater family cohesiveness was related to both daughters’ and sons’ internal control orientations. These findings suggest that family factors may contribute to children's, particularly daughters’, development of internal control expectancies.  相似文献   
95.
Objective: Polyunsaturated fatty acids n-3 (PUFA n-3) have shown effects in reducing tumor growth, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) abundantly present in fish oil (FO). When these fatty acids are provided in the diet, they alter the functions of the cells, particularly in tumor and immune cells. However, the effects of α-linolenic fatty acid (ALA), which is the precursor of EPA and DHA, are controversial. Thus, our objective was to test the effect of this parental fatty acid. Methods: Non-tumor-bearing and tumor-bearing Wistar rats (70 days) were supplemented with 1 g/kg body weight of FO or Oro Inca® (OI) oil (rich in ALA). Immune cells function, proliferation, cytokine production, and subpopulation profile were evaluated. Results: We have shown that innate immune cells enhanced phagocytosis capacity, and increased processing and elimination of antigens. Moreover, there was a decrease in production of pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6)) by macrophages. Lymphocytes showed decreased proliferation capacity, increased cluster of differentiation 8 (CD8+) subpopulation, and increased TNF-α production. Conclusions: Oil rich in ALA caused similar immune modulation in cancer when compared with FO.  相似文献   
96.
Reactive lymphoid infiltrates of the skin composed predominantly of gamma‐delta (γδ) T cells are not well described in the literature. Herein we report a case of an otherwise healthy 4‐year‐old male who presented with a waxing and waning papular rash characterized by small, discrete crusted papules spread across his trunk, face and extremities. Clinical evaluation revealed no evidence of systemic disease. Microscopic examination revealed a dermal, perivascular infiltrate of highly atypical lymphocytes with a γδ T cell phenotype, worrisome for primary cutaneous γδ T cell lymphoma. The clinical course, however, was that of a reactive condition and prompted consideration of a diagnosis of pityriasis lichenoides et varioliformis acuta (PLEVA) and lymphomatoid papulosis (LyP). In many ways, this case defies current classification schemes and seems to expand the spectrum of reactive γδ T cell infiltrates of the skin.  相似文献   
97.
98.
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.  相似文献   
99.
Background A high Mandard score implies a non-response to chemotherapy in oesophageal adenocarcinoma. However, some patients exhibit tumour volume reduction and a nodal response despite a high score. This study examines survival and recurrence patterns in these patients.Methods Clinicopathological factors were analysed using multivariable Cox regression assessing time to death and recurrence. Computed tomography-estimated tumour volume change was examined in a subgroup of consecutive patients.Results Five hundred and fifty-five patients were included. Median survival was 55 months (Mandard 1–3) and 21 months (Mandard 4 and 5). In the Mandard 4 and 5 group (332 patients), comparison between complete nodal responders and persistent nodal disease showed improved survival (90 vs 18 months), recurrence rates (locoregional 14.75 vs 28.74%, systemic 24.59 vs 48.42%) and circumferential resection margin positivity (22.95 vs 68.11%). Complete nodal response independently predicted improved survival (hazard ratio 0.34 (0.16–0.74). Post-chemotherapy tumour volume reduction was greater in patients with a complete nodal response (−16.3 vs −7.7 cm3, p = 0.033) with no significant difference between Mandard groups.Conclusion Patients with a complete nodal response to chemotherapy have significantly improved outcomes despite a poor Mandard score. High Mandard score does not correspond with a non-response to chemotherapy in all cases and patients with nodal downstaging may still benefit from adjuvant chemotherapy.Subject terms: Oesophageal cancer, Surgical oncology  相似文献   
100.
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