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   7496篇
  免费   739篇
  国内免费   13篇
耳鼻咽喉   132篇
儿科学   200篇
妇产科学   153篇
基础医学   1107篇
口腔科学   197篇
临床医学   823篇
内科学   1528篇
皮肤病学   149篇
神经病学   540篇
特种医学   354篇
外国民族医学   1篇
外科学   996篇
综合类   221篇
预防医学   735篇
眼科学   184篇
药学   411篇
中国医学   5篇
肿瘤学   512篇
  2021年   112篇
  2020年   61篇
  2019年   97篇
  2018年   113篇
  2017年   105篇
  2016年   116篇
  2015年   141篇
  2014年   157篇
  2013年   224篇
  2012年   380篇
  2011年   341篇
  2010年   211篇
  2009年   203篇
  2008年   298篇
  2007年   337篇
  2006年   284篇
  2005年   263篇
  2004年   286篇
  2003年   257篇
  2002年   218篇
  2001年   234篇
  2000年   224篇
  1999年   222篇
  1998年   124篇
  1997年   130篇
  1996年   109篇
  1995年   85篇
  1994年   89篇
  1993年   90篇
  1992年   160篇
  1991年   172篇
  1990年   176篇
  1989年   171篇
  1988年   174篇
  1987年   151篇
  1986年   166篇
  1985年   143篇
  1984年   119篇
  1983年   134篇
  1982年   77篇
  1980年   64篇
  1979年   88篇
  1978年   71篇
  1977年   54篇
  1976年   60篇
  1975年   51篇
  1974年   68篇
  1973年   55篇
  1971年   57篇
  1970年   51篇
排序方式: 共有8248条查询结果,搜索用时 31 毫秒
81.

Background

Thoracic aortic emergencies account for 10% of thoracic-related admissions in the United States and remain associated with high morbidity and mortality rates. Open repair has declined owing to the emergence of thoracic endovascular aortic repair (TEVAR), but data on emergency TEVAR use for acute aortic pathology remain limited. We therefore reviewed our experience.

Methods

We retrospectively evaluated emergency descending thoracic aortic endovascular interventions performed at a single academic level 1 trauma center between January 2005 and August 2013 including all cases of traumatic aortic injury, ruptured descending thoracic aneurysm, penetrating atherosclerotic ulcer, aortoenteric fistula, and acute complicated type B dissection. Demographics, clinical data, and outcomes were extracted. Stepwise logistic regression was used to identify independent risk factors for death.

Results

During the study period, 51 patients underwent TEVAR; 22 cases (43.1%) were performed emergently (11 patients [50.0%] traumatic aortic injury; 4 [18.2%] ruptured descending thoracic aneurysm; 4 [18.2%] complicated type B dissection; 2 [9.1%] penetrating aortic ulcer; and 1 [4.5%] aortoenteric fistula). Overall, 72.7% (n = 16) were male with a mean age of 54.8 ± 15.9 years. Nineteen patients (86.4%) required only a single TEVAR procedure, whereas 2 (9.1%) required additional endovascular therapy, and 1 (4.5%) open thoracotomy. Four traumatic aortic injury patients required exploratory laparotomy for concomitant intra-abdominal injuries. During a mean hospital length of stay of 18.9 days (range, 1 to 76 days), 3 patients (13.6%) developed major complications. In-hospital mortality was 27.2%, consisting of 6 deaths from traumatic brain injury (1); exsanguination in the operating room before repair could be achieved (2); bowel ischemia (1) and multisystem organ failure (1); and family withdrawal of care (1). A stepwise logistic regression model identified 24-hour packed red blood cell requirements ≥4 units, admission mean arterial pressure <60 mm Hg, and 24-hour fresh frozen plasma to packed red blood cell (pRBC) ratio <1:1.5 as independent risk factors for death in this cohort. During a mean follow-up of 369 days (range, 35 to 957 days), no subsequent major complications or deaths occurred. All patients underwent serial computed tomographic angiography surveillance, and no device-related problems were identified during intermediate follow-up.

Conclusions

Thoracic aortic emergencies remain challenging. Our experience in a moderate-volume center supports the utilization of TEVAR in the acute setting. Twenty-four-hour pRBC requirements ≥4 units, admission mean arterial pressure <60 mm Hg, and 24 hour fresh frozen plasma to pRBC ratio <1:1.5 were independently associated with death.  相似文献   
82.
By decreasing plaque burden, atherectomy provides an alternative to angioplasty and stenting as a means of revascularizing patients with peripheral arterial disease. A new atherectomy device (SilverHawk) has recently been approved by the Food and Drug Administration, but the results with its use are unclear. We analyzed a series of consecutive patients undergoing atherectomy. We retrospectively reviewed the charts of 35 patients undergoing infrainguinal (IF) atherectomy in 38 limbs. The Trans-Atlantic Inter-Society Consensus (TASC) classification and Society of Vascular Surgery runoff scores were calculated. Time to event analysis was performed using Kaplan-Meier estimates. Risk factors affecting patency were analyzed with a multivariate Cox model. Mean patient age was 70 +/- 9.6 years. Indications for intervention were claudication (26%), rest pain (21%), and tissue loss (53%). Femoropopliteal (FP) atherectomy was performed in 68% and tibial atherectomy in 32%. For FP lesions, the TASC distribution was A, 42%; B, 23%; C, 4%; and D, 15%. The average lesion treatment length was 9.4 +/- 10.6 cm (range 1-40), and the runoff score was 5.1 +/- 3.5. For tibial lesions, the TASC distribution was A, 0%; B, 17%; C, 8%; and D, 75%. The average lesion treatment length was 9.2 +/- 6.0 cm (range 2-20), with a runoff score of 5.4 +/- 2.4. A total of 39% of patients had prior IF interventions. Adjunctive angioplasty of the atherectomized lesion was performed in 55% of cases, stenting in 0%, and adjunctive therapy for tandem lesions in 39%. The postoperative ankle-brachial index increased by 0.30 +/- 0.14 and toe pressures increased by 40 +/- 32.4 mm Hg. Mean follow-up was 10 +/- 8 months (range 0.3-23). During the studied period, seven patients required major limb amputation and five open surgical revascularization. Total primary and secondary patency rates were 66% and 70% at 1 year, respectively. Primary and secondary patency rates for FP atherectomy were 68% and 73% at 1 year, respectively. The limb salvage rate was 74% at 6 months. Patients with prior interventions in the atherectomized segment had an almost 10-fold decrease in primary patency. Atherectomy produces acceptable results, similar to those in reported series of conventional balloon angioplasty/stenting. Patients with prior IF interventions had a nearly 10-fold decrease in primary patency. A greater than sixfold decrease in patency rates was noted in patients who underwent simultaneous inflow or outflow procedures, but this finding did not reach statistical significance (p = 0.082). Future studies should focus on cost comparisons with other treatments such as angioplasty and stenting, and prospective randomized trials should be performed to compare these treatment alternatives.  相似文献   
83.
Computed tomographic detection of nonbeta pancreatic islet cell tumors   总被引:6,自引:0,他引:6  
  相似文献   
84.
85.
High rates of sex and drug risk behaviors have been documented among Latino migrant men in the US. Whether these behaviors were established in the migrants’ home countries or were adopted in the US has not been described and has implications for prevention strategies. Quarterly surveys were conducted to gather information on selected sex and drug risk practices of Latino migrant men who arrived in New Orleans after Hurricane Katrina seeking work. Both kappa scores and McNemar’s tests were performed to determine if practice of these behaviors in home country was similar to practice post-emigration to the US. Female sex worker (FSW) patronage, same sex encounters (MSM), and crack cocaine use was more likely to occur post- rather than pre-emigration. Of those who ever engaged in these selected behaviors, most adopted the behavior in the US (i.e., 75.8 % of FSW patrons, 72.7 % of MSM participants, and 85.7 % of crack cocaine users), with the exception of binge drinking (26.8 %). Men who were living with a family member were less likely to adopt FSW patronage OR = 0.27, CI = 0.10–0.76, whereas men who earned >$465 per week were more likely to adopt crack cocaine use OR = 6.29 CI = 1.29, 30.57. Interventions that facilitate the maintenance of family cohesion and provide strategies for financial management may be useful for reducing sex and drug risk among newly arrived migrants.  相似文献   
86.
87.
88.
Alanine substitutions and selected deletions have been used to localize amino acids in QnrB essential for its protective activity. Essential amino acids are found at positions i and i−2 in the pentapeptide repeat module and in the larger of two loops, where deletion of only a single amino acid compromises activity. Deletion of 10 amino acids at the N terminus is tolerated, but removal of 3 amino acids in the C-terminal dimerization unit destroys activity.  相似文献   
89.
This paper has three aims. The first is to describe and critically evaluate two recent studies from the authors' centre. Study one is a retrospective, consecutive series case note audit of 76 children aged 3.01 – 9.11 years of age, aimed at examining the age at which children with 22q11 deletion syndrome (22q11DS) are able to achieve oral pressure in their speech, and providing an overview of presentation. Study two is a pilot study to investigate the prevalence of dyspraxic features in a consecutive series of 21 school age children with 22q11DS, aged 4.0 – 8.11 years of age. The second aim is to discuss these studies within the context of a critical review of the current knowledge about 22q11 deletion syndrome. The third aim is to challenge some common thinking around the management of velopharyngeal dysfunction ( VPD) in 22q11DS. This discussion highlights that it is sometimes possible to investigate and treat palate function with good outcomes in the preschool years based on limited speech and language and investigations. Areas for future research are discussed. This paper further underlines the complexity of the communication profile in this population, with confirmation of the unique speech and language phenotype.  相似文献   
90.
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