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   116679篇
  免费   8512篇
  国内免费   557篇
耳鼻咽喉   1421篇
儿科学   3139篇
妇产科学   2140篇
基础医学   15061篇
口腔科学   2533篇
临床医学   12184篇
内科学   24375篇
皮肤病学   2017篇
神经病学   11318篇
特种医学   4340篇
外国民族医学   1篇
外科学   18195篇
综合类   1019篇
一般理论   228篇
预防医学   9458篇
眼科学   2099篇
药学   7243篇
中国医学   159篇
肿瘤学   8818篇
  2023年   1015篇
  2022年   704篇
  2021年   3974篇
  2020年   2282篇
  2019年   3589篇
  2018年   4093篇
  2017年   2938篇
  2016年   3160篇
  2015年   3491篇
  2014年   4833篇
  2013年   6352篇
  2012年   9611篇
  2011年   9834篇
  2010年   5349篇
  2009年   4672篇
  2008年   7890篇
  2007年   7755篇
  2006年   7414篇
  2005年   7144篇
  2004年   6399篇
  2003年   5830篇
  2002年   5239篇
  2001年   726篇
  2000年   542篇
  1999年   766篇
  1998年   1038篇
  1997年   793篇
  1996年   641篇
  1995年   607篇
  1994年   481篇
  1993年   471篇
  1992年   382篇
  1991年   348篇
  1990年   311篇
  1989年   294篇
  1988年   303篇
  1987年   284篇
  1986年   307篇
  1985年   302篇
  1984年   365篇
  1983年   314篇
  1982年   342篇
  1981年   334篇
  1980年   262篇
  1979年   147篇
  1978年   192篇
  1977年   170篇
  1976年   130篇
  1975年   133篇
  1974年   137篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
1.
2.
Intratumor heterogeneity is a main cause of the dismal prognosis of glioblastoma (GBM). Yet, there remains a lack of a uniform assessment of the degree of heterogeneity. With a multiscale approach, we addressed the hypothesis that intratumor heterogeneity exists on different levels comprising traditional regional analyses, but also innovative methods including computer-assisted analysis of tumor morphology combined with epigenomic data. With this aim, 157 biopsies of 37 patients with therapy-naive IDH-wildtype GBM were analyzed regarding the intratumor variance of protein expression of glial marker GFAP, microglia marker Iba1 and proliferation marker Mib1. Hematoxylin and eosin stained slides were evaluated for tumor vascularization. For the estimation of pixel intensity and nuclear profiling, automated analysis was used. Additionally, DNA methylation profiling was conducted separately for the single biopsies. Scoring systems were established to integrate several parameters into one score for the four examined modalities of heterogeneity (regional, cellular, pixel-level and epigenomic). As a result, we could show that heterogeneity was detected in all four modalities. Furthermore, for the regional, cellular and epigenomic level, we confirmed the results of earlier studies stating that a higher degree of heterogeneity is associated with poorer overall survival. To integrate all modalities into one score, we designed a predictor of longer survival, which showed a highly significant separation regarding the OS. In conclusion, multiscale intratumor heterogeneity exists in glioblastoma and its degree has an impact on overall survival. In future studies, the implementation of a broadly feasible heterogeneity index should be considered.  相似文献   
3.
4.
5.
6.
7.
Among the chief limitations in achieving early detection and control of animal‐origin influenza of pandemic potential in high‐risk livestock populations is the existing lag time between sample collection and diagnostic result. Advances in molecular diagnostics are permitting deployment of affordable, rapid, highly sensitive, and specific point‐of‐capture assays, providing opportunities for targeted surveillance driving containment strategies with potentially compelling returns on investment. Interrupting disease transmission at source holds promise of disrupting cycles of animal‐origin influenza incursion to endemicity and limiting impact on animal production, food security, and public health. Adoption of new point‐of‐capture diagnostics should be undertaken in the context of promoting robust veterinary services systems and parallel support for operationalizing pre‐authorized plans and communication strategies that will ensure that the full potential of these new platforms is realized.  相似文献   
8.
9.
Dietary assessment in infants is challenging but necessary to understand the relationship between nutrition and growth and development. Currently no simple, validated methods exist to assess nutrient intake in New Zealand (NZ) infants. Therefore, this study aimed to assess the relative validity and reproducibility of a Complementary Food Frequency Questionnaire (CFFQ) to determine nutrient intakes of NZ infants. Ninety‐five parent–infant pairs (infant age 10 ± 1 months) completed the CFFQ twice (CFFQ‐1 and CFFQ‐2), 4 weeks apart (to assess reproducibility). A 4‐day weighed food record (4dWFR) was collected between CFFQ administrations (to assess validity). Validity and reproducibility were assessed for intakes of energy and 18 nutrients using Bland–Altman analysis, Pearson's correlation coefficients, cross‐classification, and weighted Kappa (κ). The CFFQ showed acceptable validity: Nutrients from the CFFQ were comparable with the 4dWFR (bias, 9–28%), correlation between methods ranged from r = .18 (saturated fat) to r = .81 (iron; mean r = .52), 54% (mean) of participants were correctly classified (range 39% to 67%), and 7.1% (mean) misclassified into opposite tertiles (range 2.1% to 14.7%). There was acceptable agreement between the CFFQ and 4dWFR (κ = 0.20–0.60). The CFFQ showed good reproducibility: Correlations ranged from r = .34 (folate) to r = .80 (zinc); for 16 nutrients, >50% of participants were correctly classified, and for all nutrients, <10% of participants were grossly misclassified. All nutrients showed acceptable to good agreement (κ > 0.20). The CFFQ has acceptable relative validity and good reproducibility for assessing nutrient intake in NZ infants aged 9–12 months, making it a useful tool for use in future research.  相似文献   
10.
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