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   19213篇
  免费   1346篇
  国内免费   386篇
耳鼻咽喉   310篇
儿科学   504篇
妇产科学   877篇
基础医学   2231篇
口腔科学   2682篇
临床医学   1722篇
内科学   1386篇
皮肤病学   136篇
神经病学   2552篇
特种医学   552篇
外国民族医学   2篇
外科学   1981篇
综合类   2424篇
预防医学   676篇
眼科学   298篇
药学   1630篇
  7篇
中国医学   587篇
肿瘤学   388篇
  2023年   258篇
  2022年   349篇
  2021年   594篇
  2020年   627篇
  2019年   601篇
  2018年   548篇
  2017年   569篇
  2016年   588篇
  2015年   629篇
  2014年   988篇
  2013年   1179篇
  2012年   946篇
  2011年   1122篇
  2010年   923篇
  2009年   882篇
  2008年   857篇
  2007年   815篇
  2006年   798篇
  2005年   731篇
  2004年   637篇
  2003年   544篇
  2002年   445篇
  2001年   410篇
  2000年   371篇
  1999年   337篇
  1998年   302篇
  1997年   282篇
  1996年   309篇
  1995年   315篇
  1994年   309篇
  1993年   248篇
  1992年   237篇
  1991年   215篇
  1990年   185篇
  1989年   165篇
  1988年   171篇
  1987年   152篇
  1986年   156篇
  1985年   205篇
  1984年   169篇
  1983年   118篇
  1982年   148篇
  1981年   124篇
  1980年   83篇
  1979年   69篇
  1978年   80篇
  1977年   45篇
  1976年   29篇
  1975年   20篇
  1973年   19篇
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
1.
目的:探讨基于脉压变异度(PPV)的目标导向液体治疗(GDFT)在腹膜后巨大恶性肿瘤切除术患儿中的应用。方法:择期行腹膜后巨大恶性肿瘤切除术患儿64例,年龄0.5~3岁,ASA Ⅱ-Ⅲ级。随机将患儿分为目标导向液体治疗组(G组)和常规液体治疗组(C组),每组32例。G组以PPV为指导,根据GDFT方案进行液体管理,C组采用常规液体管理。记录手术开始(T1)、手术开始后1 h(T2)、手术结束(T3)的MAP、CVP、PPV、Lac值、TNF-α、IL-6浓度。记录术中输注晶体液量、胶体液量、液体总量、出血量、尿量、手术时间、多巴胺使用率以及排气时间、术后住院时间和恶心呕吐发生率。结果:G组输注晶体液量显著少于C组(P<0.05),而输注胶体液量显著多于C组(P<0.05)。两组术中输注液体总量、出血量、尿量与多巴胺使用率方面差异无统计学意义。T2、T3时刻,G组PPV、TNF-α、IL-6显著低于C组(P<0.05),而两组间MAP、CVP、Lac在各时点差异无统计学意义。G组术后排气时间明显短于C组(P<0.05),而在术后恶心呕吐发生率和住院时间方面两组差异无统计学意义。结论:PPV指导的GDFT可以应用于腹膜后巨大恶性肿瘤切除术患儿,能维持其血流动力学稳定,减少炎症因子IL-6、TNF-α释放,促进胃肠功能恢复,但对术后转归无明显影响。  相似文献   
2.
《Vaccine》2022,40(15):2274-2281
We evaluated compliance to the ACIP pneumococcal vaccination recommendations issued in 2014 for adults aged ≥ 65 years and in 2012 for adults with high-risk (HR) conditions. The MarketScan® Commercial and Medicare Supplemental databases (January 2007-June 2019) were used to identify the cohorts of interest. Analyses for adults aged ≥ 65 years were adjusted to account for missing vaccination history. Two HR cohorts were identified. The HR1 cohort included patients with immunocompromising conditions, functional or anatomic asplenia, cerebrospinal fluid leak, or cochlear implant. The HR2 cohort included patients with chronic heart, lung, or liver disease; diabetes mellitus; alcoholism; cirrhosis; or cigarette smoking. Full compliance for those aged ≥ 65 years or in the HR1 cohort was defined as receipt of PCV13 and PPSV23, and partial compliance was defined as receipt of PCV13 or PPSV23. For those in the HR2 cohort, full compliance was defined as receipt of PPSV23. Annual compliance rates were estimated using the Kaplan–Meier method.Among those aged ≥ 65 years, partial compliance at 4 years post index was 53% and full compliance was 17% in adjusted analyses. In subjects ≥ 65 years receiving the first vaccination, 42% received the second vaccination by year 4. For the HR1 cohort, partial compliance was 19% and full compliance was 5% at 6 years post index date. For the HR2 cohort, full compliance was 20% at 6 years, with the highest rate in patients with diabetes (27%) and the lowest rate in patients with alcoholism (8%).Additional efforts are needed to maximize compliance to the ACIP pneumococcal vaccine recommendations among adults ≥ 65 years of age and adults with HR conditions including streamlined recommendations and single-dose vaccines. These efforts may subsequently reduce the incidence and burden of pneumococcal disease.  相似文献   
3.
目的:对食管胃结合部腺癌近端胃切除术(PG)人工三角瓣成形后残胃食糜进行流体动力学数值模拟,并计算不同性质胃内食糜的流动特征。方法:构建常规PG和人工三角瓣成形术术后胃仿真模型,运用Fluent软件对不同粘度胃内食糜反流问题进行数值模拟。结果:站立位姿态时,相对常规PG方案,人工三角瓣成形手术方案表现出较好的抗反流作用;卧位姿态时,当胃内食糜粘度大于0.145 2 Pa[?s,且胃内食糜不超过人工三角瓣情况下,人工三角瓣成形抗反流手术表现出较好的抗反流效果;人工三角瓣抗反流成形手术方案数值模拟结果与临床上患者表现一致。结论:本研究仿真分析为人工三角瓣成形抗反流手术方案的有效性机理分析、临床患者术后饮食及手术方案的进一步改进提供理论及数值依据。 【关键词】食管胃结合部腺癌;抗反流;人工三角瓣;计算流体力学  相似文献   
4.
组织工程技术通过利用支架材料、种子细胞、生长因子以达到修复或再生组织器官的目的。支架材料的作用是为种子细胞提供机械支撑并且保护细胞免受体内有害微环境的影响。因此,选择或制备适当的支架材料是组织工程中的关键一步。近年来,将支架材料和牙龈间充质干细胞(gingival mesenchymal stem cells,GMSCs)联合应用于组织工程的研究逐渐走向成熟。本文就组织工程中牙龈间充质干细胞递送支架载体的研究现状进行综述,以期为GMSCs组织工程递送支架载体材料的开发和选择提供思路。  相似文献   
5.
We evaluated the diagnostic utility of sonication of antibiotic loaded cement spacers comparing with periprosthetic tissue cultures for the detection of persisting infection in 14 patients undergoing staged procedures. Sonication improved microbial detection of intraoperative cultures from 14.2% to 28.5% (P = 0.481). Routine sonication of spacers is recommended.  相似文献   
6.
7.
8.
Purpose: Hazelnut and birch pollen are known to destroy tear film components and attack ocular surface cells. We investigated further pollen species from different plant families, whether they show similar effects on human tear fluid and an epithelial cell line in vitro, to provide a broad basis for further research on pollen reactions affecting the tear film and ocular surface.

Materials and methods: Regional pollen species from different plant families (Adoxaceae, Betulaceae, Fagaceae, Juglandaceae, Malvaceae, Oleaceae, Pinaceae, Plantaginaceae, Poaceae, Salicaceae, Sapindaceae) were collected. Their proteolytic activity was evaluated by Zymography. Human tear fluid and cells of an epithelial cell line were incubated with pollen extracts. Tear fluid was analyzed by Polyacrylamide gel electrophoresis (PAGE). Cytomorphology was assessed microscopically and cell viability by proliferation (MTS), water-soluble tetrazolium (WST-1) assay and the impedance-based xCELLigence real-time analysis (RTCA).

Results: Zymography revealed significant protease activity and PAGE showed the degradation of tear proteins by different pollen species. Cells incubated with pollen extracts presented dose- and time-dependent cytomorphological changes. MTS, WST-1, and RTCA revealed cytostatic as well as cytotoxic effects of pollen extracts.

Conclusions: Pollen species from different plant families exert proteolytic activity and degrade human tear fluid as well as epithelial cells, which may play a crucial role in the pathogenesis of allergic and non-allergic reactions affecting the ocular surface.  相似文献   

9.
《Alzheimer's & dementia》2019,15(9):1149-1159
IntroductionVascular factors increase the risk of Alzheimer's disease (AD). We investigated the associations between such factors, longitudinal AD cerebrospinal fluid biomarkers, and cognition.Methods433 cognitively normal participants were classified into four biomarker groups using their baseline amyloid (A+/−) and tau status (T+/−). 184 participants had undergone serial cerebrospinal fluid collection. Frequencies of risk factors and the Framingham Risk Score (FRS) were compared, and we tested the influence of risk factors on change in biomarker concentrations and cognition.ResultsThe absence of obesity, presence of hypertension, and a high FRS were associated with an increase in tau levels, particularly in A+T+ individuals. Risk factors were not associated with amyloid. Depression was associated with higher cognitive scores, whereas high FRS was associated with lower scores and a faster decline.DiscussionOur results demonstrate that vascular risk factors may enhance neurodegeneration but not amyloid accumulation in preclinical AD.  相似文献   
10.
Papillary tumor of the pineal region is a rare neuroepithelial tumor characterized by papillary architecture and epithelial cytology, immunopositivity for cytokeratin and ependymal differentiation. It is considered grade II–III by the World Health Organization and was first described by Jouvet in 2003. We present a 34-year-old male with headaches, blurred vision and normal examination. Radiological study showed a nodulocystic lesion in the pineal region compatible with pineocytoma. Surgery was performed using an infratentorial supracerebellar approach, finding a cystic tumor in the quadrigeminal cistern which was completely resected. Histopathology reported a papillary tumor of the pineal region. The patient made good progress without adjuvant therapy, and after 57 months of follow-up he remained asymptomatic and free of recurrence. A review of the literature was performed to collect all the cases published with gross total resection and no complementary treatment. In conclusion, there is still much to be learned about the pathogenesis, prognosis and management of this tumor.  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