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   248489篇
  免费   21244篇
  国内免费   14757篇
耳鼻咽喉   2215篇
儿科学   3107篇
妇产科学   4972篇
基础医学   28941篇
口腔科学   4298篇
临床医学   31639篇
内科学   40632篇
皮肤病学   2873篇
神经病学   13760篇
特种医学   8790篇
外国民族医学   97篇
外科学   27184篇
综合类   35510篇
现状与发展   48篇
一般理论   49篇
预防医学   15748篇
眼科学   6839篇
药学   24894篇
  171篇
中国医学   11570篇
肿瘤学   21153篇
  2024年   756篇
  2023年   3631篇
  2022年   9075篇
  2021年   11875篇
  2020年   8731篇
  2019年   7829篇
  2018年   8262篇
  2017年   7235篇
  2016年   6890篇
  2015年   10416篇
  2014年   13079篇
  2013年   12267篇
  2012年   18099篇
  2011年   19771篇
  2010年   12056篇
  2009年   9678篇
  2008年   13116篇
  2007年   13168篇
  2006年   12604篇
  2005年   12698篇
  2004年   8773篇
  2003年   7812篇
  2002年   6749篇
  2001年   6107篇
  2000年   6193篇
  1999年   6498篇
  1998年   3702篇
  1997年   3719篇
  1996年   2836篇
  1995年   2617篇
  1994年   2257篇
  1993年   1512篇
  1992年   2325篇
  1991年   2019篇
  1990年   1675篇
  1989年   1469篇
  1988年   1286篇
  1987年   1185篇
  1986年   956篇
  1985年   751篇
  1984年   492篇
  1983年   381篇
  1982年   229篇
  1981年   201篇
  1980年   191篇
  1979年   245篇
  1978年   142篇
  1977年   113篇
  1976年   98篇
  1974年   116篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Though distressing and potentially dangerous, sleep apnea may be an under-recognized disease in many countries. The obstructive type, which usually presents with loud snoring and excessive daytime sleepiness, is by far the commonest form. It causes a great deal of medical, social and psychological morbidity as well as an increased mortality. Doctors of different specialties have an important role in detecting and referring suspected patients for early assessment and treatment. Multidisciplinary management in a general hospital and accurate assessment with polysomnography are essential as modern and sometimes effective methods of treatment are becoming available.  相似文献   
63.
郑丽英  徐红英  陈华庆 《护理研究》2007,21(17):1568-1569
重睑成形术是眼睑美容手术之一。随着人民生活水平的提高,要求美容的人也越来越多[1]。由于该手术大部分需要切开剥离,去除眼轮匝肌或去脂去皮,容易引起皮下组织水肿、淤血,影响恢复和术后效果。2005年11月—2006年11月,笔者对124例重睑受术者进行术中冰生理盐水冷敷,在减轻水肿、淤血程度、缩短恢复期方面疗效显著。现报道如下。1资料与方法1.1临床资料本组共124例,其中女118例,男6例,年龄20岁~58岁。将受术者按手术时间先后顺序随机分为实验组和对照组各62例。1.2方法两组均使用电凝止血,5-0丝线缝合后用无菌纱布包扎伤口,口服5d抗生素。…  相似文献   
64.
在我国卫生资源总体不足和配置不合理。一方面,中国有13亿人口,占世界总人口的22%,而卫生总费用仅占世界卫生总费用的2%。更严重的是另一方面,据卫生部提供的数据,目前全国80%的医疗资源集中在大城市,其中的30%又集中在大医院。每年到大医院就诊的人群,有80%左右是在基层医院即可解决的常见病、多发病。  相似文献   
65.
66.
67.
To evaluate noninvasive measures of gene expression and tumor response in a gene-dependent enzyme prodrug therapy (GDEPT), a bifunctional fusion gene between Saccharomyces cerevisiae cytosine deaminase (CD) and Haemophilus influenzae uracil phosphoribosyltransferase (UPRT) was constructed. CD deaminates 5-fluorocytosine (5FC) to 5-fluorouracil (5FU), and UPRT subsequently converts 5FU to fluorouridine monophosphate, and both of these reactions can be monitored noninvasively in vitro and in vivo using 19F magnetic resonance spectroscopy (MRS). Following transient transfection the CD-UPRT fusion protein exhibited both UPRT and CD enzymatic activities as documented by 19F MRS. In addition, an increase in CD activity and thermal stability was witnessed for the fusion protein compared to native CD. Stable expression of CD-UPRT in 9L glioma cells increased both 5FC and 5FU sensitivity in vitro compared to CD-expressing and wild-type 9L cells. Noninvasive 19F MRS of both CD and UPRT gene function in vivo demonstrated that in animals bearing CD-expressing tumors there was limited conversion of 5FC to 5FU with no measurable accumulation of cytotoxic fluorinated nucleotides (F-nucs). In contrast, CD-UPRT-expressing tumors had increased CD gene activity with a threefold higher intratumoral accumulation of 5FU and significant generation of F-nucs. Finally, CD-UPRT yielded increased efficacy in an orthotopic animal model of high-grade glioma. More importantly, early changes in cellular water mobility, which are felt to reflect cellular death, as measured by diffusion-weighted MRI, were predictive of both durable response and increased animal survival. These results demonstrate the increased efficacy of the CD-UPRT GDEPT compared to CD alone both biochemically and in a preclinical model and validate both 19F MRS and diffusion-weighted MRI as tools to assess gene function and therapeutic efficacy.  相似文献   
68.
Most lesions in FD and their attendant functional disability occur within the first decade; 90% of lesions are present by 15 years, and the median age when assistive devices are needed is 7 years. These findings have implications for prognosis and determining the timing and type of therapy. INTRODUCTION: Fibrous dysplasia of bone (FD) is an uncommon skeletal disorder in which normal bone is replaced by abnormal fibro-osseous tissue. Variable amounts of skeletal involvement and disability occur. The age at which lesions are established, the pace at which the disease progresses, if (or when) the disease plateaus, and how these parameters relate to the onset of disability are unknown. To answer these questions, we performed a retrospective analysis of a group of subjects with FD. MATERIALS AND METHODS: One hundred nine subjects with a spectrum of FD were studied for up to 32 years. Disease progression was assessed in serial (99)Tc-MDP bone scans by determining the location and extent of FD lesions using a validated bone scan scoring tool. Physical function and the need for ambulatory aids were assessed. RESULTS: Ninety percent of the total body disease skeletal burden was established by age 15. Disease was established in a region-specific pattern; in the craniofacial region, 90% of the lesions were present by 3.4 yr, in the extremities, 90% were present by 13.7 yr, and in the axial skeleton, 90% were present by 15.5 yr. Twenty-five of 103 subjects eventually needed ambulatory aids. The median age at which assistance was needed was 7 yr (range, 1-43 yr). The median bone scan score for subjects needing assistance was 64.3 (range, 18.6-75) compared with 23.1 (range, 0.5-63.5) in the unassisted subjects (p < 0.0001). Among subjects needing assistance with ambulation, 92% showed this need by 17 yr. CONCLUSIONS: The majority of skeletal lesions and the associated functional disability occur within the first decade of life. The implication is that the window of time for preventative therapies is narrow. Likewise, therapeutic interventions must be tailored to where the patient is in the natural history of the disease (i.e., progressive disease [young] versus established disease [older subjects]). These findings have implications for prognosis, the timing and type of therapy, and the development of trials of new therapies and their interpretation.  相似文献   
69.
目的:建立泰安市RhD抗原阴性无偿献血者表型库,保证临床需求.方法:应用微板血型血清学方法对献血者进行RhD抗原筛选,采用试管法进行RhD抗原阴性确认,用分型血清进行RhD阴性表型分型.结果:89 860名献血者中检出RhD抗原阴性者352名,占0.39%,RhD抗原变异者10名,占0.01%.d基因频率为0.062 6,D基因频率为0.937 4,以ccdee所占比例最多,为57.39%,cde基因频率为0.047 4,其次为Ccdee占33.80%,其他表型则少见或罕见,其分布特征为ccdee>Ccdee>CCdee>ccdEe>CcdEe>CCdEe>ccdEE.结论:进行RhD抗原阴性无偿献血者表型分型,对于安全输血具有重要意义.  相似文献   
70.
Preparation and characterization of porous hollow silica nanoparticles (PHSN) for controlled release applications were investigated. Through orthogonally designed experiments, the optimal synthesis conditions for the preparation of PHSN were obtained and the produced PHSN were characterized by BET, SEM, TEM and IR. Scanning and transmission electron microscopy images revealed their hollow shell-core structure and also demonstrated that the size and shape of PHSN are determined by the templating CaCO3 nanoparticles. The produced PHSN were applied as a carrier to study the controlled release behaviors of Brilliant Blue F (BB), which was used as a model drug. Being loaded into the inner core and on the surfaces of the nanoparticles, BB was released slowly into a bulk solution for about 1140 min as compared to only 10 min for the normal SiO2 nanoparticles, thus exhibited a typical sustained release pattern without any burst effect. In addition, higher BET of the carriers, lower pH value and lower temperature prolonged BB release from PHSN, while stirring speed showed little influence on the release behavior. It showed that PHSN have a promising future in controlled drug delivery applications.  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