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   337146篇
  免费   23482篇
  国内免费   7385篇
耳鼻咽喉   4063篇
儿科学   9498篇
妇产科学   6545篇
基础医学   27149篇
口腔科学   7947篇
临床医学   36933篇
内科学   41612篇
皮肤病学   4567篇
神经病学   19137篇
特种医学   7818篇
外国民族医学   31篇
外科学   35956篇
综合类   50918篇
现状与发展   13篇
一般理论   30篇
预防医学   34015篇
眼科学   5212篇
药学   31104篇
  373篇
中国医学   31770篇
肿瘤学   13322篇
  2023年   5306篇
  2022年   7868篇
  2021年   12623篇
  2020年   12348篇
  2019年   18214篇
  2018年   15909篇
  2017年   12869篇
  2016年   10415篇
  2015年   9669篇
  2014年   19941篇
  2013年   21530篇
  2012年   18319篇
  2011年   19779篇
  2010年   15869篇
  2009年   14533篇
  2008年   14147篇
  2007年   14640篇
  2006年   12762篇
  2005年   11091篇
  2004年   9009篇
  2003年   7930篇
  2002年   6216篇
  2001年   5582篇
  2000年   4589篇
  1999年   3948篇
  1998年   3030篇
  1997年   2885篇
  1996年   2499篇
  1995年   2570篇
  1994年   2483篇
  1993年   1973篇
  1992年   2006篇
  1991年   1736篇
  1990年   1545篇
  1989年   1375篇
  1988年   1302篇
  1987年   1118篇
  1985年   3785篇
  1984年   4794篇
  1983年   3342篇
  1982年   3800篇
  1981年   3545篇
  1980年   3156篇
  1979年   2905篇
  1978年   2534篇
  1977年   1906篇
  1976年   2150篇
  1975年   1631篇
  1974年   1429篇
  1973年   1277篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
PurposeTo evaluate in vivo parameters as biomarkers of limbal stem cell function and to establish an objective system that detects and stage limbal stem cell deficiency (LSCD).MethodsA total of 126 patients (172 eyes) with LSCD and 67 normal subjects (99 eyes) were included in this observational cross-sectional comparative study. Slit-lamp biomicroscopy, in vivo laser scanning confocal microscopy (IVCM), and anterior segment optical coherence tomography (AS-OCT) were performed to obtain the following: clinical score, cell morphology score, basal cell density (BCD), central corneal epithelial thickness (CET), limbal epithelial thickness (LET), total corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and tortuosity coefficient. Their potential correlations with the severity of LSCD were investigated, and cutoff values were determined.ResultsAn increase clinical score correlated with a decrease in central cornea BCD, limbal BCD, CET, mean LET, maximum LET, CNFL, CNFD, CNBD, and tortuosity coefficient. Regression analyses showed that central cornea BCD, CET and CNFL were the best parameters to differentiate LSCD from normal eyes (Coef = 3.123, 3.379, and 2.223; all p < 0.05). The rank correlation analysis showed a similar outcome between the clinical scores and the central cornea BCD (ρ = 0.79), CET (ρ = 0.82), and CNFL (ρ = 0.71). A comprehensive LSCD grading formula based on a combination of these parameters was established.ConclusionsA comprehensive staging system combining clinical presentation, central cornea BCD, CET, and CNFL is established to accurately and objectively diagnose LSCD and stage its severity.  相似文献   
75.
In recent years, there has been increased global advocacy for the use of a collaborative, multisectoral, and transdisciplinary approach: a One Health approach, with the goal to achieve optimal health outcomes for people, animals and their shared environment. This study explored One Health implementation and practice in Kenya. Further, I used a case study of Nthongoni, a remote rural area in Eastern Kenya, to help us to understand and think about implementation of One Health in an area where mainstream biomedical system runs parallel to or is in conflict with, a deeply entrenched indigenous health system. I used a qualitative research approach including participant observation, and key informant and general respondents' in-depth interviews. Data was transcribed verbatim, translated, checked for consistency and coded for content and thematic analysis. The findings indicate that although Kenya's One Health approach was hailed as a key strategy and a model for other countries in the region, the approach faced significant challenges including insufficient funding, competing priorities and concerns over its sustainability. But while the formal One Health is embroiled in structural and politico-economic influences that curtail its operationalization and success, this study illuminates a lay one health that is part of lived realities in Nthongoni, inviting us to reflect on the place for and status of traditional healers, and meaning of health for people and animals. The study further provokes our thoughts over whether One Health should integrate or do away with traditional health systems, or be abandoned altogether. I argue that incorporating traditional health knowledge and practitioners in One Health might help to make health care more robust and culturally responsive. The work contributes to debates on anthropology of health in general and to anthropological understanding of both the lay one health and the institutional One Health agenda.  相似文献   
76.
BackgroundIn the United States nearly 20% of children ages 12–17 have developmental disorders. Some attain population-based developmental milestones after a delay, or increase functioning through special education, medication, technology, or therapy. Others have severe lasting impairments. An indicator identifying those groups in surveys of adults could help shape policies to improve lives.HypothesesWe hypothesized that survey histories of special education could indicate functional status levels.MethodsData were from the nationally representative Panel Study of Income Dynamics (1997–2017, n = 2745). With measures of diagnoses, behaviors, functional status, service use, and adult outcomes, we tested three special education groups as indicators of: (1) no impairment (no special education), (2) disorders, developmental diagnoses that adversely affect educational performance, but with development after a period of delay or only moderate disability, indicated by transfer from special education; and (3) severe lasting disability, the diagnoses combined with life-long needs for supports or services, with limitations in areas including self-care, mobility, and capacity for independent living, indicated by special education in the individual's final year of school.ResultsAcross the special education groups, from no impairment to severe lasting disability, there were trends of: increasing severe and lasting disability (respectively 4.8%, 35.6%, 76.4%); increasing special services use (13.5%, 43.1%, 83.7%); increasing severe emotional disorders (2.3%, 11.3%, 17.9%); lower percentages attaining at least an associate's degree by age 25 (42.1%, 20.7%, and 8.9%); and more chronic diseases.ConclusionsSpecial education histories provide a useful indicator of developmental disability impairment levels in adults.  相似文献   
77.
PurposeTo compare the characteristics of polidocanol (POL) and ethanolamine oleate (EO) sclerosing foams produced by a Shirasu porous glass membrane (SPGM) device with those made using a 3-way stopcock (3WSC).Materials and MethodsFoam half-life times were measured in an ex-vivo benchtop study. Computed tomography (CT) images of each foam were obtained over the time course, and a CT texture analysis was conducted. The bubble size in each foam was measured by an optical microscope.ResultsMedian foam half-life times were longer in the SPGM group than in the 3WSC group (POL: 198 vs 166 s, P = .02; EO: 640 vs 391 s, P < .01). In the CT texture analysis, median standard deviation (SD) and entropy (randomness) were lower, and median energy (uniformity) and gray-level cooccurrence matrix (GLCM) homogeneity were higher in the SPGM group than in the 3WSC group (POL SD: at 30 s and 50–300 s; POL entropy: at 0–60 s; EO SD: at 0–600 s; EO entropy: at 0–460 s; POL energy: at 0–40 s; POL GLCM homogeneity: at 0–250 s; EO energy: at 0–360 s; EO GLCM homogeneity: at 0–480 s; all P < .05). Median bubble diameters in the SPGM group and in the 3WSC group were 69 and 83 μm (P < .01), respectively, in the POL foam; and 36 and 36 μm (P = .45), respectively, in the EO foam.ConclusionsPOL and EO foams had greater uniformity and longer foam half-life time when prepared with an SPGM device than with a 3WSC.  相似文献   
78.
The Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network (NRN) maintains a database of extremely preterm infants known as the Generic Database (GDB). Begun in 1987, this database now includes more than 91,000 infants, most of whom are extremely preterm (<29 weeks gestation). The GDB has been the backbone of the NRN, providing high quality, prospectively collected data to study the changing epidemiology of extreme prematurity and its outcomes over time. In addition, GDB data have been used to generate hypotheses for prospective studies and to develop new clinical trials by providing information about the numbers and characteristics of available subjects and the expected event rates for conditions and complications to be studied. Since its inception, the GDB has been the basis of more than 200 publications in peer-reviewed journals, many of which have had a significant impact on the field of neonatology.  相似文献   
79.
Induction of labour is a common obstetrical procedure and is undertaken when the benefits of delivery are considered to outweigh the risks of continuation of pregnancy. However, more than one-fifth of induction cases fail to result in vaginal births and lead to unplanned caesarean deliveries, which compromise the birth experience and have negative clinical and resource implications. The need for accurate prediction of successful labour induction is increasingly recognised and many researchers have attempted to evaluate the potential predictability of different factors including maternal characteristics, Bishop score, various biochemical markers and ultrasound markers and derive predictive models to address this issue.  相似文献   
80.
目的 慢性牙周炎表现的病理性骨吸收非常常见,牙周膜干细胞(PDLSCs)的外泌体(Exo)对骨吸收的作用和影响尚不明确,本研究分析了该Exo蛋白组分对破骨细胞分化的影响。方法 分别从正畸前拔牙患者和慢性牙周炎患者的牙周膜组织中提取PDLSCs,通过流式细胞术检测表面标记物;通过差速离心分别提取2种细胞的Exo,即Exo-WT和Exo-CP,并通过Western blot、透射电子显微镜(TEM)、蛋白浓度检测、纳米粒径追踪检测Exo特征;通过蛋白质谱检测2种Exo的蛋白组分;通过酶联免疫吸附(ELISA)验证了差异表达蛋白肿瘤坏死因子α(TNF-α)、核因子κB受体活化因子配体(RANKL)、白细胞介素(IL)-1α、转化生长因子β(TGF-β)、骨形态发生蛋白2(BMP-2)表达水平;将10、100、1 000 μg·mL-1的Exo-CP或Exo-WT加入RAW264.7培养基中并于5 d时通过实时荧光定量聚合酶链反应(RT-qPCR)、Western blot、抗酒石酸酸性磷酸酶(TRAP)染色检测破骨分化相关指标表达情况;采用SPSS 24.0软件对实验数据进行统计学分析。结果 Exo-CP富集的差异表达蛋白主要与破骨细胞分化的TNF信号通路、核转录因子κB(NF-κB)信号通路相关;ELISA实验证实了Exo-CP中高表达TNF-α、RANKL、IL-1α,低表达TGF-β1、BMP-2(P<0.05);Exo-CP作用于RAW264.7,显著提高了细胞的破骨分化相关基因及蛋白的表达水平,TRAP染色可见分化的破骨细胞,且呈现浓度依赖性,100、1 000 μg·mL-1浓度Exo-CP对破骨细胞分化的促进作用显著高于10 μg·mL-1浓度组(P<0.05)。结论 慢性牙周炎的病理性骨吸收可能由炎性PDLSCs所分泌的Exo通过促进破骨细胞分化引起,Exo中主要的作用蛋白可能为RANKL和TNF-α,本研究为慢性牙周炎骨吸收的发病机制提供了新视角。  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