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   2157篇
  免费   124篇
  国内免费   85篇
耳鼻咽喉   10篇
儿科学   68篇
妇产科学   19篇
基础医学   274篇
口腔科学   196篇
临床医学   180篇
内科学   298篇
皮肤病学   11篇
神经病学   42篇
特种医学   45篇
外科学   184篇
综合类   297篇
预防医学   135篇
眼科学   27篇
药学   368篇
中国医学   139篇
肿瘤学   73篇
  2023年   27篇
  2022年   36篇
  2021年   62篇
  2020年   65篇
  2019年   48篇
  2018年   53篇
  2017年   57篇
  2016年   65篇
  2015年   49篇
  2014年   121篇
  2013年   131篇
  2012年   136篇
  2011年   140篇
  2010年   81篇
  2009年   77篇
  2008年   91篇
  2007年   100篇
  2006年   87篇
  2005年   92篇
  2004年   71篇
  2003年   54篇
  2002年   62篇
  2001年   57篇
  2000年   56篇
  1999年   36篇
  1998年   45篇
  1997年   36篇
  1996年   45篇
  1995年   30篇
  1994年   28篇
  1993年   24篇
  1992年   26篇
  1991年   25篇
  1990年   17篇
  1989年   19篇
  1988年   18篇
  1987年   17篇
  1986年   12篇
  1985年   25篇
  1984年   18篇
  1983年   18篇
  1982年   11篇
  1981年   21篇
  1980年   18篇
  1979年   7篇
  1978年   6篇
  1977年   17篇
  1976年   9篇
  1975年   6篇
  1974年   6篇
排序方式: 共有2366条查询结果,搜索用时 15 毫秒
1.
A series of N-(5-(alkylthio)-1,3,4-oxadiazol-2-yl)methyl)benzamides 6a–i were synthesized as alkaline phosphatase inhibitors. The intermediate 5-substituted 1,3,4-oxadiazole-2-thione 4 was synthesized starting with hippuric acid. Hippuric acid in the first step was converted into corresponding methyl ester 2 which upon reaction with hydrazine hydrate furnished the formation of hydrazide 3 . The hippuric acid hydrazide was then cyclized into 5-substituted 1,3,4-oxadiazole-2-thione 4 . The intermediate 4 was then reacted with alkyl or aryl halides 5a–5i to afford the title compounds N-(5-(methylthio)-1,3,4-oxadiazol-2-yl)methyl)benzamides 6a–i . The bioassay results showed that compounds 6a–i exhibited good to excellent alkaline phosphatase inhibitory activity. The most potent activity was exhibited by the compound 6i having IC50 value 0.420 μM, whereas IC50 value of standard (KH2PO4) was 2.80 μM. Molecular docking studies was performed against alkaline phosphatase enzyme (PDBID 1EW2) to check binding affinity of the synthesized compounds 6a–i against target protein. The docking results showed that three compounds 6c , 6e , and 6i have maximum binding interactions with binding energy values of −8 kcal/mol. The compound 6i displayed the interactions of oxadiazole ring nitrogen with amino acid His265 having a binding distance 2.13 Ǻ. It was concluded from our results that synthesized compounds, especially compound 6i may serve as lead structure to design more potent inhibitors of human alkaline phosphatase.  相似文献   
2.
3.
PurposeTo compare the safety and efficacy of transarterial chemoembolization for hepatocellular carcinoma (HCC) in patients with and without transjugular intrahepatic portosystemic shunts (TIPS).Materials and MethodsThis single-institution study included a retrospective review of 50 patients who underwent transarterial chemoembolization for HCC between January 2010 and April 2017. Twenty-five patients had preexisting TIPS, and 25 patients were selected to control for age, sex, and target tumor size. Baseline median Model for End-Stage Liver Disease (MELD; 13 TIPS, 9 control; P < .001) and albumin-bilirubin (ALBI; 3 TIPS, 2 control; P < .001) differed between groups. Safety was assessed on the basis of Common Terminology Criteria for Adverse Events (CTCAE) and change in MELD and ALBI grade assessed between 3 and 6 months. Efficacy was assessed by tumor response and time to progression (TTP).ResultsThere was 1 severe adverse event (CTCAE grade >2) in the TIPS group. There was no difference in the change in MELD or ALBI grade. Although there was no difference in tumor response (P = .19), more patients achieved a complete response in the control group (19/25, 76%) than in the TIPS group (13/25, 52%). There was no difference in TTP (P = .82). At 1 year, 2 patients in the control group and 3 patients in the TIPS group received a liver transplant. Seven patients died in the TIPS group.ConclusionsTransarterial chemoembolization is as safe and effective in patients with TIPS as in patients without TIPS, despite worse baseline liver function. Severe adverse events are rare and may be transient.  相似文献   
4.
5.
6.
7.
8.
9.
文题释义:微弧氧化技术:是金属材料表面处理的一种技术,将金属材料(如,镁、铝、钛等)置于特定电解液中,通过弧光放电过程中瞬时的高温和高压条件产生结合于金属表面的陶瓷膜层,该种方法制备的涂层材料具有高硬度、耐磨的特点。  种植体:是针对于人体自身牙齿缺失而植入上下颌骨内的人工牙根。性能优良的种植体需要同时具备高强度、耐降解、生物相容性好的特性。目前复合材料类如金属表面添加陶瓷涂层材料,具有上述多种材料特性而被临床选择。 背景:采用普通电化学法可在钛及其合金表面制备纳米级羟基磷灰石涂层,但该涂层吸收降解缓慢,需要8-12周的时间。而微弧氧化可在复杂表面形成均匀薄膜,有利于细胞黏附和骨组织长入。 目的:探索微弧氧化羟基磷灰石涂层钛合金对成骨细胞增殖及骨向分化能力的影响。 方法:采用电化学法与微弧氧化法分别制备羟基磷灰石涂层钛合金材料,检测两种材料表面的接触角。将成骨细胞系hFOB1.19接种于两组羟基磷灰石涂层钛合金材料表面,培养48 h时,采用扫描电镜观察细胞在材料上的形态变化;培养1,12,24,48,72 h时,采用MTT法检测细胞增殖;培养1,3,5 d时,比较两组材料表面细胞计数与碱性磷酸活性;培养第5天,采用Western Blotting检测细胞内骨形态发生蛋白2和骨形态发生蛋白4表达。 结果与结论:①微弧氧化组材料表面的接触角小于电化学组[(66.5±2.2)°,(52.8±2.1)°,P=0.001 5)];②扫描电镜显示,电化学组成骨细胞形态不规则,胞体皱缩不饱满,与材料贴合较差;微弧氧化组细胞充分伸展,形态扁平,与材料贴合紧密;③微弧氧化组12-72 h的细胞增殖快于电化学组(P < 0.05),培养3,5 d的细胞计数多于电化学组(P < 0.05);④微弧氧化组培养1,3,5 d的细胞碱性磷酸酶活性高于电化学组(P < 0.05);⑤微弧氧化组骨形态发生蛋白2和骨形态发生蛋白4表达均高于电化学组(P < 0.05);⑥结果表明,微弧氧化羟基磷灰石涂层钛合金材料可促进成骨细胞的增殖及骨向分化能力。 ORCID: 0000-0003-2787-4667(王艳玲) 中国组织工程研究杂志出版内容重点:生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程  相似文献   
10.
The concept of the alkaline activity of powdered materials introduced into cement compositions has been proposed, along with methods for its determination. The possibility of using waste glass as an active additive to Portland cement was evaluated from the standpoint of alkaline activity. Replacing the Portland cement component with glass waste in the form of glass powder at amounts from 1 to 35% made it possible to maintain the cement composition’s alkaline activity at a level that met the standard requirements. The previously unknown effects of mixed alkali in Portland cement in the presence of glass waste are described. Portland cement has a high potassium alkaline activity; however, container glass has a high sodium alkaline activity and a fairly low potassium alkaline activity. When glass waste is introduced into the structure of cement compositions, potassium alkaline activity is reduced.  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