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   7520篇
  免费   732篇
  国内免费   192篇
耳鼻咽喉   75篇
儿科学   182篇
妇产科学   93篇
基础医学   691篇
口腔科学   109篇
临床医学   905篇
内科学   1038篇
皮肤病学   91篇
神经病学   416篇
特种医学   219篇
外科学   712篇
综合类   1313篇
现状与发展   1篇
一般理论   2篇
预防医学   923篇
眼科学   167篇
药学   814篇
  3篇
中国医学   385篇
肿瘤学   305篇
  2024年   20篇
  2023年   54篇
  2022年   137篇
  2021年   268篇
  2020年   198篇
  2019年   125篇
  2018年   138篇
  2017年   171篇
  2016年   125篇
  2015年   259篇
  2014年   296篇
  2013年   394篇
  2012年   551篇
  2011年   556篇
  2010年   481篇
  2009年   395篇
  2008年   517篇
  2007年   546篇
  2006年   441篇
  2005年   324篇
  2004年   284篇
  2003年   272篇
  2002年   204篇
  2001年   170篇
  2000年   187篇
  1999年   122篇
  1998年   56篇
  1997年   66篇
  1996年   46篇
  1995年   42篇
  1994年   36篇
  1993年   42篇
  1992年   88篇
  1991年   71篇
  1990年   70篇
  1989年   63篇
  1988年   64篇
  1987年   50篇
  1986年   61篇
  1985年   48篇
  1984年   40篇
  1983年   34篇
  1982年   25篇
  1981年   28篇
  1980年   24篇
  1979年   33篇
  1978年   23篇
  1976年   20篇
  1975年   18篇
  1974年   16篇
排序方式: 共有8444条查询结果,搜索用时 484 毫秒
41.
42.
The Motivation Assessment Scale (MAS) has been proposed as an efficient questionnaire for identifying the source of reinforcement for an individual's self-injurious behavior (SIB). A previous reliability analysis of the MAS (Durand & Crimmins, 1988) reported interrater correlation coefficients ranging from .66 to .92, based on a comparison of responses provided by classroom teachers. In this study, the reliability of the MAS was reexamined with two independent groups of developmentally disabled individuals who exhibited SIB (N = 55). For the institutional sample (n = 39), the MAS was given to two staff members (a supervisor and therapy aide) who work with the individual daily. For the school sample (n = 16), the MAS was given to the teacher and teacher's aide who taught the student. The correlational analyses completed by Durand and Crimmins (1988) were repeated; in addition, a more precise analysis of interrater reliability was calculated based on the actual number of scoring agreements between the two raters. Results showed that only 16 of the 55 raters agreed on the category of reinforcement maintaining their client's or student's SIB, that only 15% of the correlation coefficients obtained were above .80, and that none of the reliability scores based on percent agreement between raters was above 80%.  相似文献   
43.
A continuous air monitor has been developed that includes provisions for improving the detection of alpha-emitting aerosol particles in the presence of radon/thoron progeny that are unattached to ambient aerosol particles. Wind tunnel tests show that 80% of 10-microns aerodynamic equivalent diameter particles penetrate the flow system from the ambient air to the collection filter when the flow rate is 57 L min-1 (2 cfm) and the wind speed is 1 m s-1. Uniformity of aerosol collection on the filter, as characterized by the coefficient of variation of the areal density deposits, is less than 15% for 10-microns aerodynamic-equivalent-diameter aerosol particles. Tests with unattached radon daughters in a flow-through chamber showed that approximately 99% of the 218Po was removed by an inlet screen that is designed to collect radon daughters that are in the size range of molecular clusters. The inlet screen offers the opportunity to improve the signal-to-noise ratio of energy spectra in the regions of interest (subranges of the energy spectrum) of transuranic elements and thereby enhance the performance of background compensation algorithms.  相似文献   
44.
BACKGROUND CONTEXT: Postsurgical epidural adhesions and fibrosis after surgery for lumbar disc herniation are a consequence of normal wound healing. The presence of fibrosis renders reoperations risky, and in some patients fibrosis may lead to nerve root tethering. PURPOSE: One approach to minimizing the risk of developing epidural adhesions is to provide a barrier between the dural membrane and the healing connective tissues. The purpose of these studies was to evaluate such a barrier device. STUDY DESIGN/SETTING: In vivo investigation in an animal model at a university laboratory. PATIENT SAMPLE: Rabbit. OUTCOME MEASURES: Gross and histomorphic evaluation. METHODS: Barriers comprised of carboxymethylcellulose (CMC) and polyethylene oxide (PEO) (Oxiplex; FzioMed, Inc., San Luis Obispo, CA) were studied as devices to reduce epidural adhesion formation in rabbit laminotomy and laminectomy models. The barriers tested were either a gel alone (gel) or a gel covered with a film (gel/film combination). Two laminotomy or laminectomy sites (depending on the surgical method) were created in each rabbit at L4 and L6. One site was treated with a CMC/PEO gel, or CMC/PEO gel/film combination, and the other site served as a surgical control. Two surgical models that differed in the extent of adhesion formation at untreated injury sites and the method of injury generation were used. RESULTS: Model A, which did not incorporate dural abrasion, resulted in up to 40% adhesion-free laminectomy sites in controls. Model B, which did incorporate abrasion of the dural membrane, resulted in less than 10% adhesion-free laminotomy sites in controls. Compositions of CMC/PEO gels (2.5% to 10% PEO) and films (22.5% PEO) were tested in both models. Efficacy parameters included measuring the number of sites free of epidural fibrosis and reduction in the severity of fibrosis (adhesions). Both gels and gel/film combinations consistently reduced the frequency and the extent of epidural fibrosis in both models. Gels of CMC/PEO containing a higher content of PEO (10%) and a higher molecular weight of PEO (4.4 mD) were most effective in Model B and resulted in up to 84% laminotomy sites with minimal or no epidural fibrosis, whereas controls exhibited over 90% of the sites with epidural fibrosis. Histological evaluation of the surgical sites indicated that the reduction of epidural fibrosis was accompanied by normal bone healing. In addition, these experiments demonstrated that the gel/film combination provided no additional benefit to that obtained by the gel alone. CONCLUSIONS: Gels of CMC/PEO reduced epidural fibrosis and did not impair normal heal ing.  相似文献   
45.
46.
豚鼠爆震性聋耳蜗结构与功能的动态变化   总被引:1,自引:0,他引:1  
目的 探讨爆震性聋与耳蜗损伤之间的关系。方法 通过畸变产物耳声发射及扫描电镜进行研究。结果 豚鼠爆震后即刻出现听阈的提高,与爆震前相比,DPOAEs幅值于1kHz处开始出现非常显著的减低(P〈0.05),在8kHz处两者的差值更大(P〈0.05),DPOAEs幅值随频率升高而逐渐下降,以高频段更为严重。爆震后20天DPOAEs幅值在0.5、0.7、1kHz处基本恢复至爆震前水平,在1.5—8kHz处较爆震后即刻明显提高,但仍低于爆震前水平(各频率均P〈0.05)。爆震后40天DPOAEs幅值与爆震后20天无明显改变(各频率均P〉0.05)。扫描电镜下见豚鼠爆震后即刻出现IHC纤毛排列紊乱,第一排OHC形态基本正常,第二排OHC部分纤毛扭曲或倒伏,尚可看到鸟翼状结构,第三排OHC倒伏、分散,部分折断;20天组IHC纤毛排列仍然紊乱,第一排OHC纤毛基本正常,第二、第三排OHC纤毛排列极度扭曲,以第三排更为严重,少数OHC溶解变性,空位由支持细胞取代;40天组与20天组无明显差别。结论 爆震性聋出现耳蜗HC结构改变及功能减退,提示耳蜗损伤与爆震性聋紧密相关。  相似文献   
47.
柯敬东  魏威  田鸣 《临床麻醉学杂志》2008,24(12):1053-1055
目的探讨术毕应用芬太尼对丙泊酚-雷米芬太尼麻醉恢复的影响。方法45例实施腹腔镜胆囊切除术患者随机均分成F1、F1.5和F2三组,手术结束前10min分别给予芬太尼1、1.5和2μg/kg,评定拔管后疼痛和镇静程度,记录呼吸恢复、意识恢复和拔管时间以及拔管后的不良事件。结果F2组的VAS显著低于F1、F1.5组[(0.2±0.4)分vs.(2.1±1.2)分和(1.2±1.2)分](P<0.05);F2组Ramsay评分显著高于F1和F1.5组[(4.5±0.5)分vs.(3.1±0.3)分和(3.2±0.6)分](P<0.01)。F2组的呼吸恢复、意识恢复和拔管时间分别为(21.5±0.5)min,(19.5±1.5)min和(24.0±2.1)min,显著延长于F1组的(10.9±3.1)min,(12.2±3.1)min和(15.2±4.8)min和F1.5组的(11.9±3.2)min,(14.3±4.4)min和(16.7±4.5)min(P<0.01)。结论在腹腔镜胆囊切除术手术结束前10min应用1或1.5μg/kg芬太尼可减轻雷米芬太尼停药后的疼痛反应,但不显著延长苏醒和拔管时间。  相似文献   
48.
In the evolution of humans, many kinds of mutations in the human genome have been accumulated, providing credible genetic evidence for the study of human origins and migrations. The "out-of-Africa" hypothesis of modern human evolution and the genetic origin of the Japanese has come about by studying mitochondrial DNA.l,2 Recently, researchers have recognized the power of Y-chromosome markers in resolving migratory patterns of modern humans as more and more Y-chromosome single nucleotide polymorphism markers have been found. The markers on the nonrecombinant part of the Y-chromosome allows for the reconstruction of intact haplotypes which are probably the best genetic tools to study human migrations. We can analyze the paternal history of some people in different areas by Y-chromosome haplotypes.  相似文献   
49.
柯希煌  练克俭 《中国骨伤》2007,20(9):570-572
急性臂丛神经炎是一种少见病,但人们往往认识不足,在早期,易被误诊为神经根型颈椎病或胸廓出口综合征。为了提高对本病的认识,降低误诊和漏诊率,本文就急性臂丛神经炎的诊断、鉴别诊断与治疗进行综述。1诊断名词与病因急性臂丛神经炎,病因尚未明了,但却有典型的临床特征。最初由Parsonage等[1]和Turner等[2]报道为肩胛带综合征和麻痹性臂丛神经炎,后被称之为:Parsonage-Turner综合征。其他诊断名词有:急性臂丛神经炎,神经源性肌萎缩,术后原发性臂丛神经炎等[3,4]。  相似文献   
50.
目的初步观察用小分子干扰RNA(siRNA)沉默树突状细胞(DCs)恒定链(Ii)后,DCs疫苗的体外抗肿瘤效果。方法从小鼠骨髓分离骨髓前体细胞,细胞经100 ng/ml GM-CSF和100 ng/ml IL-4诱导培养6 d后,转染针对DCs Ii链特异的Ii-siRNA,转染后加用50 ng/ml TNF-α继续诱导细胞成熟48 h,然后分别用Western blot检测沉默效果及CCK-8试剂盒检测DCs刺激同种异体淋巴细胞增殖的能力;此外,DCs共转染Ii-siRNA和小鼠胃癌前体细胞MFC的总RNA后,与同种异体淋巴细胞共培养,通过ELISA检测培养上清IFN-γ/和IL-4的水平,并收集致敏淋巴细胞进行体外杀伤实验。结果Ii-siRNA明显抑制DCs Ii的表达。沉默Ii链能够增强DCs的淋巴细胞增殖能力,并促使淋巴细胞向Th1的方向漂移[IFN-γ:(5107±351)pg/ml,IL-4:(65±13)pg/ml,P<0.05]。淋巴细胞经共转染Ii-siRNA和MFC RNA的DCs激活后,明显而特异地杀伤靶肿瘤细胞(杀伤百分率: 66.94%±2.75%,P<0.05)。结论通过siRNA沉默DCs的Ii链可能是一种行之有效的增强抗肿瘤免疫的方法。  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