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   19924篇
  免费   1935篇
  国内免费   1280篇
耳鼻咽喉   210篇
儿科学   420篇
妇产科学   99篇
基础医学   1202篇
口腔科学   414篇
临床医学   2568篇
内科学   1688篇
皮肤病学   153篇
神经病学   349篇
特种医学   767篇
外科学   1797篇
综合类   5595篇
现状与发展   7篇
预防医学   2393篇
眼科学   231篇
药学   2402篇
  23篇
中国医学   2012篇
肿瘤学   809篇
  2024年   85篇
  2023年   216篇
  2022年   575篇
  2021年   787篇
  2020年   648篇
  2019年   348篇
  2018年   362篇
  2017年   579篇
  2016年   420篇
  2015年   760篇
  2014年   1037篇
  2013年   1262篇
  2012年   1886篇
  2011年   2032篇
  2010年   1784篇
  2009年   1602篇
  2008年   1743篇
  2007年   1647篇
  2006年   1480篇
  2005年   1114篇
  2004年   814篇
  2003年   677篇
  2002年   455篇
  2001年   354篇
  2000年   271篇
  1999年   105篇
  1998年   23篇
  1997年   17篇
  1996年   10篇
  1995年   3篇
  1994年   5篇
  1993年   5篇
  1992年   4篇
  1991年   2篇
  1990年   3篇
  1989年   4篇
  1988年   2篇
  1987年   5篇
  1986年   4篇
  1985年   6篇
  1984年   1篇
  1983年   1篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
目的 建立用于偏头痛疗效评价的症状条目,为制定基于偏头痛患者报告的结局评价(patient-reported outcome,PRO)量表奠定基础.方法 筛选102例近代头痛医案中出现频率≥5%的症状和218例偏头痛临床研究病例中出现频率≥5%且治疗后显著改善(P<0.05)的症状.以筛选结果为基础,采取专家单独访谈和研究小组讨论的方式,初步确定偏头痛临床疗效评价的症状条目池.结果 医案和临床研究病例共筛选出40条症状.经专家访谈和研究小组讨论,初步确定了23个症状条目可用于疗效评价,涉及头痛、躯体症状、心境/情感3个方面.结论 医案和临床研究病例可以作为偏头痛PRO量表症状条目池初步筛选的研究对象,筛选结果为制定专家咨询问卷和患者调研问卷提供了依据,为制定偏头痛PRO量表奠定了基础.  相似文献   
82.
目的 探讨模拟失重膳食 Fe摄入量及蛋白质含量的变化 .方法 受试者 - 6°头低位卧床 2 1d,用称量法观察其营养素及 Fe摄入量的变化 ,并于卧床前 2 d,卧床 1,11和 2 1d测定血红蛋白 (Hb) ;用双缩脲法及溴甲酚绿法分别测定血清总蛋白及白蛋白含量 .结果 膳食 Fe摄入量 2 wk开始降低 16 % ,3wk后基本恢复 ,血清总蛋白也在 2 wk降低 5 % (P<0 .0 5 ) ,3wk回升 ,Hb不受影响 .结论 模拟失重对膳食Fe摄入量及总蛋白含量有短期影响 ,经过适应期后可恢复到正常范围  相似文献   
83.
目的:观察自体胸腔积液上清作为培养液对肿瘤浸润淋巴细胞(TIL)生长的影响.方法:恶性胸腔积液中的TIL经贴壁法分离后,分别采用含有细胞因子白细胞介素-2(IL-2)、CD3单克隆抗体(OKT3)及植物血球凝集素(PHA)的自体胸腔积液上清及含10%人AB型血清的RPMIl640进行培养,比较两种培养液对TIL的增殖速度、培养前后免疫表型变化和对自体肿瘤细胞的杀伤活性。结果:培养2周,经统计学比较发现,自体胸腔积液上清作为培养液对TIL的生长速度、免疫表型和对自体肿瘤细胞杀伤活性的影响与应用含10%人AB型血清的RPMIl640培养液培养无差异。结论:自体胸腔积液上清作为培养液培养TIL是可行的。为自体TIL疗法治疗恶性胸腔积液提供理论基础。  相似文献   
84.
目的观察早期机械通气对重型颅脑损伤的临床研究。方法选择50例ICU收治的重型颅脑损伤患者作为研究对象,采取随机抽样法分为机械通气治疗组(A组)和吸氧治疗组(B组)两组,分别给以机械通气(每天FiO2100%2 h)和吸氧(低流量)治疗,每天监测患者生命体征、颅内压(ICP)、C一反应蛋白(CRP)、PO2、PCO2、氧合指数(PaO2/FiO2),比较两组患者脑水肿消退程度、脑水肿消退时间、平均ICU住院时间、死亡率的变化。结果两组治疗后比较.机械通气治疗组较吸氧治疗组生命体征更趋于稳定。各项监测指标提示机械通气治疗组PO2及氧合指数更佳,脑水肿消退快、程度轻,脑水肿持续时间短,c反应蛋白明显下降,说明颅脑损伤逐步恢复。表3示2周内死亡率比较.机械通气治疗组较吸氧治疗组明显下降。机械通气治疗组与吸氧治疗组比较,P<0.05,有统计学意义。结论早期机械通气能减轻脑水肿,降低颅内压,改善脑循环,改善脑供氧,防止氧自由基的产生减轻炎症损伤.防止并发症。降低病死率及ICU住院时间。  相似文献   
85.
Objective Branched polyethylene glycols (PEG) with different molecular weight were cross-linked to the porcine decellularized aortic valve (DAV) and the effects of PEG cross-linking on the mechanical properties were investigated. Methods A total of 25 porcine DAVs were randomly assigned into 5 groups: PEG3400, PEG8000, PEG12000, PEG20000 and control. The reactive time was 4 h at room temperature. The efficiency of crosslinking was calculated by measuring the residual thiol group. The mechanical properties were obtained by static tensile test. Results The efficiency of crosslinking was 92. 40% , 89. 88% , 87. 87% and 87. 46% in PEG3400, PEG8000, PEG12000, PEG20000 groups, respectively. As compared with other groups, the PEG3400 group had significantly greater increase in the crosslinking degree (P < 0. 05). Tensile test showed the tensile strength of PEG12000 and PEG20000 groups was (3. 22 ±0.41) and (3. 19 ±0. 15) MPa, respectively, and significantly different from that in control group (P < 0. 05). The tensile strength and young' s modulus had a positive correlation with the molecular weight of PEG. Conclusion Branched PEG with the molecular weight of 12 000 Da and 20 000 Dacan effectively crosslink to the porcine decellularized aortic valves and improve their mechanical behaviors, and has the potential to be used as the material of fabricating new hybrid scaffold of tissue engineering heart valves.  相似文献   
86.
目的 探讨采用锁定跟骨钢板治疗新鲜跟骨关节内移位骨折的临床疗效.方法 2004年10月至2006年10月,治疗34例男性闭合性跟骨关节内移位骨折患者,年龄19~42岁,平均34岁;左足14例,右足20例;高处坠落伤22例,车祸伤12例.受伤至手术时间7~21天,平均13天.术前均对伤足摄正、侧位X线片及跟骨的CT轴位片.根据Sanders分型,Ⅱ型16例,Ⅲ型18例.采用扩大外侧入路对34例患者进行手术,骨折复位后利用锁定跟骨钢板完成骨折内固定.结果 28例患者获得随访,随访时间6~40个月,平均20个月.切口均甲级愈合.B(o)hler角由术前平均7.41°±4.08°改善至术后第7天的29.74°±5.56°和术后3个月的30.00°±5.53°;Gissane角由术前平均163.71°±9.31°改善至术后第7天的122.59°±14.11°和术后3个月的125.85°±19.31°.骨折均愈合,愈合时间为6~12周.术后无一例患者发生撞击或神经、血管损伤等并发症,未出现骨折移位或内固定失败等情况.术前美国足踝外科学会(American Orthopaedic Foot & Ankle Society,AOFAS)评分系统的踝-后足评分为(17.68±9.34)分,术后3个月和6个月分别为(74.79±4.01)分和(74.28±17.92)分.结论 应用锁定跟骨钢板治疗新鲜跟骨骨折,可以获得满意的临床效果,利于患者的功能恢复.
Abstract:
Objective To evaluate the clinical outcome of operative management of displaced intraarticular fractures of the calcaneus using locking plates. Methods From October 2004 to October 2006, 34patients with close displaced intraarticular fractures of the calcaneus were fixed with Calcaneal locking Plates through the extensive lateral approach. The right foot was involved in 20 patients. The mean age was 34 yesrs with a range of 19 to 42 years. Accordiing to Sanders' classification system, there were 16 patients in style Ⅱ and 18 in style Ⅲ The mean interval between injury and operation was 13 days Standard reduction and fixation techniques were performed to realign all components of the intra-articular calcaneal fracture using a locking calcaneal fracture plate. The result were evaluated with AOFAS (American Orthopaedic Foot & Ankle Society) ankle-hindfoot scale. Results Twenty-eight patients were followed up. The follow-up duration ranged from six to forty months, with the mean of twenty months. angle and were measured at, The average B(o)hler angle was 29° and 30° and the average Gissane was 122° and 125° seven days and three months after operation. Bone union was achieved in all cases. All incisons had healed smoothly. No patient sustained lateral impingement syndrome or soft tissue complications The mean AOFAS scores that was measured three months and six months after operation was 74. Conclusion The application of the calcaneal locking plates through extended lateral approach is proved to be an effective treatment for displaced intra-articular calcaneal fracture, offering the combination of good reduction and early rehabilitation.  相似文献   
87.
目的 研究9-硝基喜树碱及其脂质体对人肝癌细胞株HepG2和人正常肝细胞L02细胞周期、凋亡的影响及其可能的作用机制.方法 HepG2、L02细胞用含不同浓度9-硝基喜树碱及其脂质体的培养液孵育后,利用MTT法测定细胞活性,流式细胞术检测细胞周期及细胞凋亡,WesternBlot验证周期相关蛋白和凋亡相关蛋白的表达变化.结果 9-硝基喜树碱及其脂质体对两种细胞生长呈时间和剂量依赖性抑制.药物处理后S期和G2/M期细胞明显增多,浓度大于0.1 μmol/L时24 h后HepG2细胞完全阻滞于S期;0.1 μmol/L孵育72 h后,超过95%HepG2细胞阻滞于G2/M期.药物对细胞凋亡的诱导作用也呈明显的剂量和时间依赖关系.Western Blot显示:Bax、Caspase3表达增高,Cyclin A、Cdk2、Cyclin E、Bcl-2表达减低.与L02相比,HepG2细胞对药物更加敏感.结论 9-硝基喜树碱及其脂质体可以通过调控细胞周期和诱导凋亡有效抑制细胞生长,其对肿瘤细胞的抑制作用强于正常肝细胞.9-硝基喜树碱脂质体体外抗肿瘤效果略强于9-硝基喜树碱单体.
Abstract:
Objective To investigate the modulating effects and explore their mechanism of 9-nitrocamptothecin and its liposomes to induce apoptosis and inhibit cell cycle in HepG2 and L02 cell lines. Methods Cells were incubated with 9-nitrocamptothecin(9NC) or with 9-nitrocamptothecin liposomes for 24 h, 48 h and 72 h, then, the cell viability was measured via MTT assay; cell cycle and apoptosis was evaluated by flow cytometry after stained by PI and Annexin V-PE/7AAD. Additional, Western Blot was used to evaluate the expression of cell cycle and apoptosis related protein. Results Both cells viability were apparently inhibited by the 9-nitrocamptothecin and 9-nitrocamptothecin liposomes, the inhibitory effect showed a time-dependent and dose-dependent manner. Both S and G2/M phases arrest were observed after incubated with drugs. HepG2 cell was completely arrested in S phase when 9NC concentration over than 0. 1 μmol/L after incubation for 24 h, while more than 95% cells arrested in G2/M phase when 9NC concentration is 0. 1 μmol/L after incubation for 72 h. Apoptosis induction effect also showed a time-dependent and dose-dependent manner. Western Blot results showed the expression of Bax and Caspase-3 were upregulated while Cyclin A, Cdk2, Cyclin E and Bcl-2 were downregulated. More importantly, the compounds were more cytotoxic to the cancer cell lines than to the normal liver cell. Conclusions 9-nitrocamptothecin and 9-nitrocamptothecin liposomes can potently inhibit cell growth via regulation of cell cycle and induction of apoptosis, and this effect was preferentially in cancer cell. Inhibitory of 9-nitrocamptothecin liposomes was slightly better than the 9-nitrocamptothecin.  相似文献   
88.
目的:从组织学角度探讨尖锐湿疣condylomata acuminate(CA)的基本病变、发生发展过程、病因及病理特征的关系.方法:收集350例病理诊断为CA的病例,观察其病理形态学特征,部分病例做原位杂交、P53与S-100蛋白检测及TEM观察.结果:①CA主要是薄层表皮增殖单位(epidermal proliferation unit)的慢性病毒(HPV6、11)性增生性炎,病变特点是含HPV表皮细胞柱的特殊水变性(CA细胞群),乳头状曾殖、分化及凋亡,三者协同作用是本病的发病基础.②HPV感染DNA见于水变性表皮细胞柱的核中,偶见于胞浆及细胞的间质中.③潜伏在表皮内的HPV及宿主免疫反应低是本病慢性发展及反复发作的原因.结论:CA是表皮增殖单位的慢性病毒性增生性炎.  相似文献   
89.
Carcinoids of the pancreas are exceedingly rare tumors that originate from the enterochromaffin cells of the gastroenteropancreatic neuroendocrine system. According to a recent report, pancreatic carcinoids are found in only 0.58% (79/13 715 cases) of the entire carcinoid group. To date, very limited information regarding the detection and diagnosis of this entity has been reported in the available literature. Although pancreatic carcinoid tumors grow slowly and show an indolent clinical behavior, they are potentially malignant. Due to the late onset of clinical symptoms and delayed diagnosis of the tumor, there was a high incidence of distant metastases that hampered long-term survival for many patients, leading to an unfavorable overall prognosis.  相似文献   
90.
目的 探索近10年来孤独症谱系障碍(ASD)-小胶质细胞研究领域的热点及未来发展趋势,对ASD的神经炎症以及运动减轻ASD症状的免疫调控机制及可能的通路进行综述。方法 从Web of Science核心数据库中检索2012年1月至2021年12月ASD-小胶质细胞相关研究。采用CiteSpace 5.8.R3软件对纳入文献的年度发文量、高频关键词及关键词聚类等进行可视化分析。结果与结论 共纳入783篇文献,发文量总体呈上升趋势。神经炎症是ASD发病机制相关研究的热点,其中小胶质细胞的异常激活、炎性细胞因子水平的改变是ASD发生、发展的重要因素。运动是改善ASD的重要干预方法,可能通过减轻神经炎症或调控小胶质细胞介导的炎症通路实现。  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