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   45423篇
  免费   3493篇
  国内免费   1384篇
耳鼻咽喉   278篇
儿科学   741篇
妇产科学   442篇
基础医学   6977篇
口腔科学   569篇
临床医学   2391篇
内科学   5961篇
皮肤病学   953篇
神经病学   4804篇
特种医学   661篇
外国民族医学   4篇
外科学   3917篇
综合类   4300篇
现状与发展   2篇
预防医学   2116篇
眼科学   542篇
药学   9788篇
  6篇
中国医学   1666篇
肿瘤学   4182篇
  2023年   893篇
  2022年   1147篇
  2021年   1688篇
  2020年   1553篇
  2019年   1896篇
  2018年   1721篇
  2017年   1578篇
  2016年   1255篇
  2015年   1454篇
  2014年   2238篇
  2013年   2733篇
  2012年   2158篇
  2011年   2640篇
  2010年   2239篇
  2009年   2131篇
  2008年   2187篇
  2007年   2025篇
  2006年   1853篇
  2005年   1567篇
  2004年   1507篇
  2003年   1340篇
  2002年   985篇
  2001年   755篇
  2000年   815篇
  1999年   662篇
  1998年   623篇
  1997年   572篇
  1996年   499篇
  1995年   513篇
  1994年   444篇
  1993年   428篇
  1992年   418篇
  1991年   370篇
  1990年   317篇
  1989年   295篇
  1988年   240篇
  1987年   244篇
  1986年   231篇
  1985年   490篇
  1984年   596篇
  1983年   390篇
  1982年   447篇
  1981年   401篇
  1980年   347篇
  1979年   320篇
  1978年   273篇
  1977年   184篇
  1976年   165篇
  1975年   132篇
  1974年   103篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
Epidermolysis bullosa simplex (EBS) is a skin fragility disorder resulting from mutations of structural proteins in the epidermis. We provide a brief report of long‐term survival and reproduction in a mother with EBS due to keratin 5 (KRT5) c.1429G > A (p.E477K) mutation, which causes a particularly severe form of the disease.  相似文献   
103.
Objective: To determine serotonin system abnormalities related to major depression or previous suicidal behavior.

Methods: [11C]WAY100635, [18F]altanserin and positron emission tomography were used to compare 5-HT1A and 5-HT2A binding in MDD patients divided into eight past suicide attempters (>4yrs prior to scanning) and eight lifetime non-attempters, and both groups were compared to eight healthy volunteers.

Results: The two receptor types differed in binding pattern across brain regions from each other, but there were no differences in binding between healthy volunteers and the two depressed groups or between depressed suicide attempters and non-attempters. No effects of depression severity or lifetime aggression were observed for either receptor.

Conclusion: Limitations of this study include small sample size and absence of high lethality suicide attempts in the depressed attempter group. No trait-like binding correlations with past suicide attempt or current depression were observed. Given the heterogeneity of nonfatal suicidal behavior, a larger sample study emphasizing higher lethality suicide attempts may find the serotonin biological phenotype seen in suicide decedents.  相似文献   

104.
Background: Extracellular matrix molecular components, previously linked to multisystem syndromes include collagens, fibrillins and laminins. Recently, we described a novel multisystem syndrome caused by the c.9418G>A p.(V3140M) mutation in the laminin alpha-5 (LAMA5) gene, which affects connective tissues of all organs and apparatus in a three generation family. In the same family, we have also reported a myopic trait, which, however, was linked to the Prolyl 4-hydroxylase subunit alpha-2 (P4HA2) gene. Results of investigation on vitreous changes and their pathogenesis are reported in the present study.Materials and Methods: Nineteen family individuals underwent complete ophthalmic examination including best-corrected visual acuity (BCVA), fundus examination, fundus photography, intraocular pressure measurement, axial length measurement using ocular biometry, Goldmann visual field examination, standard electroretinogram, SD-OCT. Segregation analysis of LAMA5 and P4HA2 mutations was performed in enrolled members.Results: The vitreous alterations fully segregated with LAMA5 mutation in both young and adult family members. Slight reduction of retinal thickness and peripheral retinal degeneration in only two patients were reported.Conclusions: In this work we showed that PVD is a common trait of LAMA5 multisystem syndrome, therefore occurring as an age-unrelated trait. We hypothesize that the p.(V3140M) mutation results in a reduction of retinal inner limiting membrane (ILM) stability, leading to a derangement in the macromolecular structure of the vitreous gel, and PVD. Further investigations will be necessary to elucidate the role of wild type and mutated LAMA5 in the pathogenesis of PVD.  相似文献   
105.

BACKGROUND CONTEXT

Cervical laminectomy and fusion (CLF) is a common surgical option for multilevel cord compression. Postoperative C5 palsy occurrence after CLF has been a vexing problem for spine physicians. The posterior shift of the cord following laminectomy has been implicated as a major factor for postoperative C5 palsy, but attempts by spine surgeons to mitigate excessive shift while providing sufficient decompression have not been well reported.

PURPOSE

To compare the incidence of postoperative C5 palsy after performing selective blocking laminoplasty concurrently with CLF to those of conventional CLF.

STUDY DESIGN

A retrospective comparative study of prospectively collected data.

PATIENT SAMPLE

Of 116 cervical myelopathy patients with degenerative cervical myelopathy, ossification of the posterior longitudinal ligament, and multilevel disc herniation, 93 patients (69 in group A [CLF group] and 24 in group B [selective blocking laminoplasty with CLF, CLF-S group]) were included in the study.

OUTCOME MEASURES

The primary outcome measure was the occurrence of postoperative C5 palsy. Secondary end points included (1) clinical outcomes based on pain intensity, neck disability index (NDI), Japanese Orthopaedic Association (JOA) score, (2) radiologic outcomes including cervical alignment and fusion rate at 1 year and hardware complications, and (3) perioperative data (hospital stay, blood loss, and operative times).

METHODS

We compared the occurrence of postoperative C5 palsy, as well as clinical, radiologic, and surgical outcomes, between the two groups at 1-year follow-up.

RESULTS

The patients in both groups were statistically similar between the groups with respect to demographic characteristics such as age, sex, smoking status, body mass index, preoperative pathology, surgical segments, and the degree of the cervical lordosis. Postoperative C5 palsy developed in 9 of 61 patients (14%) in group A and in 0 of 24 patients (0%) in group B (CLF-S group) (p=.03). Postoperative neck pain, NDI, and JOA improvement were not significantly different between the two groups (p=.93, 0.90, and 0.79, respectively). Perioperative data did not differ significantly between the two groups.

CONCLUSIONS

This study showed that performing selective blocking laminoplasty might lead to reducing the incidence of postoperative C5 palsy in CLF surgery.  相似文献   
106.
107.

Background

Catheter ablation of ventricular tachycardia (VT) can reduce the burden of ventricular arrhythmia (VA) but its effect on health care utilization and costs after such therapy is poorly known. We sought to compare the rates of cardiovascular (CV)-related hospitalizations, survival, and health care costs in patients with recurrent VT treated either with VT ablation or with medical therapy.

Methods

One-hundred implantable cardioverter-defibrillator patients with structural heart disease who underwent VT ablation were included. Propensity score-matched patients with recurrent VT treated with medical therapy were identified from a prospective registry of approximately 7000 de novo implantable cardioverter-defibrillator patients. Outcomes and costs were ascertained using health administrative databases.

Results

Among patients who underwent VT ablation, the cumulative rates of VA-related hospitalizations were lower in the 2 years after their ablation procedure compared with the year before (rate ratio, 0.3; 95% confidence interval [CI], 0.22-0.43). Rates of CV-related hospitalization and hospitalization because of VA post index date were similar between the VT ablation and medical therapy groups (hazard ratio [HR], 0.94; 95% CI, 0.57-1.54 and HR, 1.04; 95% CI, 0.57-1.91, respectively). Health care costs in the VT ablation patients were not increased post-ablation compared with the medical management group. The risk of all-cause mortality was lower among patients in the VT ablation group relative to the medical therapy group (HR, 0.64; 95% CI, 0.4-0.99).

Conclusions

Patients who underwent VT ablation experienced a significant reduction in their rate of VA-related hospitalizations. Patients treated with VT ablation had similar rates of CV-related hospitalization compared with those treated with medical therapy without increased health care-related costs.  相似文献   
108.
109.
BackgroundThe improved overall survival (OS) after short course preoperative radiotherapy (SCPRT) using 5 × 5 Gy reported in the early rectal cancer trials could not be replicated in subsequent phase III trials. This original survival advantage is attributed to poor quality of surgery and the large differential in local recurrence rates, with and without SCPRT. Immuno-modulation during and after SCPRT and its clinical implications have been poorly investigated. We propose an alternative explanation for this survival benefit in terms of immunological mechanisms induced by SCPRT and the timing of surgery, which may validate the concept of consolidation chemotherapy.Material and methodsWe reviewed randomized controlled trials (RCTs) and studies of SCPRT from 1985 to 2019. We aimed to examine the precise timing of surgery in days following SCPRT and identify evidence for immune modulation, neo-antigens and memory cell induction by radiation.ResultsConsiderable variability is reported in randomised trials for median overall treatment time (OTT) from start of SCPRT to surgery (8–14 days). Only three early trials showed a benefit in terms of OS from SCPRT, although the level of benefit in preventing local recurrence was consistent across all trials. Different patterns of immune effects are observed within days after SCPRT depending on the OTT, but human leukocyte antigen (HLA)-1 expression was not upregulated.ConclusionsSCPRT has a substantial immune-stimulatory potential. The importance of the timing of surgery after SCPRT may have been underestimated. An optimal interval for surgery after 5 × 5 Gy may lead to better outcomes, which is possibly exploited in total neoadjuvant therapy schedules using consolidation chemotherapy. Individual patient meta-analyses from appropriate SCPRT trials examining outcomes for each day and prospective trials are needed to clarify the validity of this hypothesis. The interaction of SCPRT with tumour adaptive immunology, in particular the kinetics and timing, should be examined further.  相似文献   
110.
目的探讨当归龙荟片联合普芦卡必利治疗慢性功能性便秘的临床疗效。方法选取2018年5月-2019年5月在北京市肛肠医院治疗的慢性功能性便秘患者122例,根据用药的差别分为对照组(61例)和治疗组(61例)。对照组口服琥珀酸普芦卡必利片,2mg/次,1次/d;治疗组在对照组基础上口服当归龙荟片,4片/次,2次/d。两组患者均经4周治疗。观察两组患者临床疗效,同时比较治疗前后两组患者临床症状评分、PAC-QOL积分、结肠传输试验积分、Bristol和SF-36评分,及血清5-羟色胺(5-HT)、血管活性肠肽(VIP)、P物质(SP)和一氧化氮(NO)水平。结果治疗后,对照组和治疗组临床有效率分别为80.33%和96.72%,两组比较差异具有统计学意义(P<0.05)。经治疗,两组症状积分均明显降低(P<0.05),且治疗组比对照组降低更明显(P<0.05)。经治疗,两组患者PAC-QOL积分和结肠传输试验积分明显降低(P<0.05),而Bristol和SF-36评分明显升高(P<0.05),且治疗组患者明显好于对照组(P<0.05)。经治疗,两组患者血清SP、5-HT水平均显著升高(P<0.05),而VIP和NO水平均明显降低(P<0.05),且治疗组患者SP、5-HT、VIP和NO水平明显优于对照组(P<0.05)。结论当归龙荟片联合普芦卡必利治疗慢性功能性便秘可有效改善患者临床症状,促进患者生活质量改善,具有一定的临床推广应用价值。  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