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   5175篇
  免费   265篇
  国内免费   82篇
耳鼻咽喉   74篇
儿科学   102篇
妇产科学   47篇
基础医学   176篇
口腔科学   59篇
临床医学   988篇
内科学   435篇
皮肤病学   24篇
神经病学   431篇
特种医学   537篇
外科学   962篇
综合类   870篇
预防医学   206篇
眼科学   49篇
药学   288篇
  12篇
中国医学   167篇
肿瘤学   95篇
  2024年   6篇
  2023年   69篇
  2022年   136篇
  2021年   195篇
  2020年   218篇
  2019年   128篇
  2018年   129篇
  2017年   158篇
  2016年   160篇
  2015年   196篇
  2014年   361篇
  2013年   331篇
  2012年   315篇
  2011年   312篇
  2010年   270篇
  2009年   275篇
  2008年   243篇
  2007年   239篇
  2006年   220篇
  2005年   229篇
  2004年   176篇
  2003年   138篇
  2002年   120篇
  2001年   126篇
  2000年   80篇
  1999年   61篇
  1998年   64篇
  1997年   50篇
  1996年   52篇
  1995年   57篇
  1994年   58篇
  1993年   51篇
  1992年   25篇
  1991年   26篇
  1990年   25篇
  1989年   30篇
  1988年   26篇
  1987年   23篇
  1986年   32篇
  1985年   23篇
  1984年   16篇
  1983年   7篇
  1982年   17篇
  1981年   4篇
  1980年   10篇
  1979年   10篇
  1978年   12篇
  1977年   5篇
  1976年   3篇
  1971年   2篇
排序方式: 共有5522条查询结果,搜索用时 15 毫秒
1.
BackgroundOur meta-analysis from 2013 showed that inserting a catheter intrathecally after an observed accidental dural puncture can reduce the need for epidural blood patch in labouring women requesting epidural analgesia. We updated our conventional meta-analysis and added a trial-sequential analysis (TSA).MethodsA systematic literature search was conducted to identify studies that compared inserting the catheter intrathecally with an epidural catheter re-site or with no intervention. The extracted data were pooled and the risk ratio (RR) and 95% confidence interval (95%CI) for the incidence of post-dural puncture headache (PDPH) was calculated, using the random effects model. A contour-enhanced funnel plot was constructed. A TSA was performed and the cumulative Z score, monitoring and futility boundaries were constructed.ResultsOur search identified 13 studies, reporting on 1653 patients, with a low risk of bias. The RR for the incidence of PDPH was 0.82 (95%CI 0.71 to 0.95) and the RR for the need for epidural blood patch was 0.62 (95%CI 0.49 to 0.79); heterogeneity of both analyses was high. The TSA showed that the monitoring or futility boundaries were not crossed, indicating insufficient data to exclude a type I error of statistical analysis. Contour-enhanced funnel plots were symmetric, suggesting no publication bias.ConclusionsConventional meta-analyses showed for the first time that intrathecal catheterisation can reduce the incidence of PDPH. However, TSA did not corroborate this finding. Despite increasing use in clinical practice there is no firm evidence on which to base a definite conclusion.  相似文献   
2.

Objective

The advantage of arteriovenous fistulas (AVFs) in older patients requiring dialysis is controversial. We reviewed our vascular access experience in patients ≥70 years of age (older group) compared with younger patients.

Methods

We analyzed consecutive patients who underwent access surgery between 2013 and 2016. Primary success (PS) and primary patency (PP) data were analyzed between the older and younger groups before and after propensity score matching of the patients' characteristics and access composition. PS was defined as the achievement of access function that was amenable to two sessions of successful cannulation without early occlusion or maturation failure requiring revision. PP was defined as the time with uninterrupted patency without intervention.

Results

A total of 594 consecutive accesses were created among 563 patients, of whom 119 were allocated into each group after propensity score matching. In the whole cohort, 193 accesses (32.5%) were performed in older patients. AVFs were performed in 130 (67.4%) older patients and 293 (73.1%) younger patients. Regarding AVFs, the PS rate (83.6% in the older group vs 94.3% in the younger group; P = .001) and the overall PP at 6 and 12 months (73.1% and 57.1%, respectively, in the older group vs 86.7% and 77.7%, respectively, in the younger group; P = .009) were lower in the older group than in the younger group. However, no differences were found in the PS and PP rates for arteriovenous grafts between groups. Regarding the AVF location, the PS rate for forearm AVFs was significantly lower in the older group than in the younger group (76% vs 93%; P < .001); however, the PS rate of the upper arm was not different between the groups (94% vs 97%; P = .425). In the patients with PS, the PP rate of AVFs was similar between the two groups. In the older group with forearm AVFs, the median diameter of the radial artery was larger in the patients with PS than in the patients without PS (2.20 mm with PS vs 2.00 mm without PS; P = .008). The propensity score matching results demonstrated similar trends for the whole cohort, with lower PS (P = .042) and PP rates (P = .023) for AVF in the older group.

Conclusions

The outcomes after AVF were poorer in the older group than in the younger group, which was primarily due to unsatisfactory outcomes in patients with forearm AVFs. Thus, stricter criteria, especially regarding the radial artery diameter, should be applied for forearm AVFs in older patients, and additional research is necessary to delineate the risk factors for primary failure.  相似文献   
3.
IntroductionDural puncture epidural (DPE) analgesia is a modification of conventional epidural analgesia that involves the intentional puncture of the dura with a spinal needle through the needle placed in the epidural space, without a medication being injected intrathecally. There have been contradictory findings regarding better analgesia and better block quality.MethodsA systematic literature search was done to identify randomized controlled trials (RCT) comparing DPE with epidural analgesia. The risk of bias was assessed with the Cochrane tool. Risk ratio and 95% confidence intervals were calculated.ResultsFive RCTs including 581 patients were identified. One RCT on caesarean section was excluded. Single studies suggested slightly better analgesia by finding a median time to achieve sufficient analgesia of two minutes less in the DPE group, a higher number of women having a pain score <10/100 at 20 min, a reduction in the number of epidural top-ups and better sacral spread. The studies did not show a difference between DPE and epidural analgesia for catheter replacement or manipulation rates, the incidence of intravascular placement or unilateral block.ConclusionThere is a lack of clear evidence on either the benefits or the risks of the DPE technique, such that a recommendation for or against its routine use is premature. Two of the three studies showing a beneficial effect of DPE came from the same institution and replication of the findings by other groups is warranted.  相似文献   
4.
PURPOSE: This study was undertaken to clarify the importance of bleeding vascular ectasia of the colon as the etiology of massive lower gastrointestinal hemorrhage in patients 40 years of age or younger. METHODS: An otherwise healthy 21-year-old male was admitted to a tertiary medical center with massive lower gastrointestinal hemorrhage. Technetium-labeled red blood cell scan, selective visceral angiography, and colonoscopy identified the source of bleeding as vascular abnormality of the descending colon. Segmental colonic resection was performed. RESULTS: Histologic review of the specimen demonstrated a vascular ectasia. The patient recovered uneventfully and has had no further stigmata of hemorrhage. A review of the literature was undertaken to make clear the significance of vascular ectasia as the source for massive colonic hemorrhage in the young adult. CONCLUSION: This is the first report that documents histologically a vascular ectasia as the source of massive lower gastrointestinal hemorrhage in an otherwise healthy patient less than 40 years of age. Vascular ectasia is an uncommon cause of lower gastrointestinal hemorrhage in the young adult.The Chief, Bureau of Medicine and Surgery, Navy Department, Washington, DC, Clinical Investigation Program sponsored this report #84-16-1968-532, as required by HSETCINST 6000.41A. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.  相似文献   
5.
带手套穿刺对留置套管针一次成功率的影响   总被引:1,自引:0,他引:1  
张昆 《护理研究》2002,16(5):259-260
为探讨戴手套与不戴手套穿刺对留置静脉套管针一次成功率的影响 ,为护理人员的自身防护提供科学依据 ,选取冠状动脉搭桥术病人 12 0例 ,随机分为实验组和对照组 ,实验组采用戴手套穿刺法 ,对照组采用常规洗手后不戴手套穿刺法。结果两组一次穿刺成功率经χ2 检验 ,无统计学意义( χ2 =0 .5 6 3,P >0 .0 5 )。说明戴手套留置套管针并不影响一次穿刺成功率。  相似文献   
6.
Summary Two contrasting cases of cervical intramedullary cavernous angioma in young female patients are reported. One patient had a 3-year course of step-wise progressive tetraparesis; at each of the five events intramedullary bleeding from a cryptic vascular malformation at C6–7 level was diagnosed by MRI. The other patient presented with one episode which led to MRI diagnosis of a vascular malformation at the C2 level. Both patients eventually underwent complete surgical excision of the angioma with subsequent steady improvement of the neurological deficit.  相似文献   
7.
Two young men with longstanding suprapatellar masses are presented. The initial clinical diagnosis was of a synovial or soft tissue tumour. Magnetic resonance imaging showed the features of an arteriovenous malformation (AVM). Surgical exploration and biopsy confirmed the diagnosis. AVMs, although rare, should be considered as a possible diagnosis of a peri-articular swelling of the knee.  相似文献   
8.
目的:探讨肝动脉栓塞治疗肝癌肝动脉-门静脉瘘(APF)所致大量腹腔积液的临床应用价值。方法:并发高流量APF和大量腹腔积液的肝癌患者9例,以明胶海绵颗粒栓塞载瘘动脉,消除或减少APF,用碘化油尽量栓塞肝癌病灶。结果:APF消失7例,少量残留2例;门静脉血流方向全部由逆肝转为向肝;肝癌病灶内碘化油沉积良好6例;术后2周内腹腔积液完全消失5例,少量残余4例;2周后肝功复查,5例肝功能原有明显损害者全部明显改善;全部病例原有腹胀、腹痛、厌食、乏力症状不同程度缓解。结论:对肝癌并高流量APF所致腹腔积液,动脉栓塞治疗简单、安全、有效。  相似文献   
9.
Bertalanffy  H.  Kretzschmar  H.  Gilsbach  J. M.  Ott  D.  Mohadjer  M. 《Acta neurochirurgica》1990,104(3-4):151-155
Summary This case report describes a patient presenting with symptoms of increased intracranial pressure, whose computerized tomographic (CT) scan was highly suggestive of a large low-grade glioma invading the basal ganglia. Magnetic resonance imaging (MRI) revealed a well-demarcated space-occupying mass of increased intensity in the left lateral ventricle and adjacent white matter. Following stereotactic biopsy, which yielded a homogeneous jelly-like material, the mass was removed microsurgically and was found to be most like a colloid cyst on histological examination. Discussion focusses on the clinical and differential diagnostic implications of this very unusual combination of findings.  相似文献   
10.
腹腔镜卵巢穿刺内凝治疗多囊卵巢不孕症的临床研究   总被引:2,自引:0,他引:2  
目的探讨腹腔镜卵巢穿刺内凝对多囊卵巢不孕症的治疗价值。方法151例腹腔镜卵巢穿刺内凝术(实验组)和151例开腹卵巢楔切术(对照组)治疗多囊卵巢不孕症配对对比研究。结果实验组的手术时间33.1±7.2min,术中失血15.6±4.7ml,总排卵率92.05%,总妊娠率49.67%,均优于对照组(P<0.01);术后雄激素、LH/FSH下降幅度小于对照组(P<0.01)。随时间推移,两组术后排卵巢、妊娠率均有下降倾向,而术后雄激素、LH/FSH则有逐渐回升的倾向。结论腹腔镜卵巢穿刺内凝术对多囊卵巢不孕症有较好的治疗效果  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