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   43027篇
  免费   3336篇
  国内免费   184篇
耳鼻咽喉   379篇
儿科学   1305篇
妇产科学   904篇
基础医学   5541篇
口腔科学   806篇
临床医学   4217篇
内科学   9481篇
皮肤病学   612篇
神经病学   4462篇
特种医学   1380篇
外国民族医学   1篇
外科学   6200篇
综合类   635篇
一般理论   33篇
预防医学   3456篇
眼科学   1010篇
药学   3051篇
  1篇
中国医学   66篇
肿瘤学   3007篇
  2023年   237篇
  2022年   126篇
  2021年   774篇
  2020年   576篇
  2019年   858篇
  2018年   969篇
  2017年   737篇
  2016年   815篇
  2015年   972篇
  2014年   1372篇
  2013年   1896篇
  2012年   2832篇
  2011年   3195篇
  2010年   1768篇
  2009年   1611篇
  2008年   2732篇
  2007年   3101篇
  2006年   2897篇
  2005年   2963篇
  2004年   2750篇
  2003年   2546篇
  2002年   2351篇
  2001年   375篇
  2000年   286篇
  1999年   405篇
  1998年   464篇
  1997年   325篇
  1996年   319篇
  1995年   322篇
  1994年   302篇
  1993年   307篇
  1992年   254篇
  1991年   250篇
  1990年   200篇
  1989年   180篇
  1988年   194篇
  1987年   180篇
  1986年   149篇
  1985年   213篇
  1984年   266篇
  1983年   240篇
  1982年   293篇
  1981年   299篇
  1980年   282篇
  1979年   141篇
  1978年   169篇
  1977年   159篇
  1976年   141篇
  1974年   119篇
  1973年   98篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Although the reproductive calendar is the primary tool for measuring contraceptive dynamics in low-income settings, the reliability of calendar data has seldom been evaluated, primarily due to the lack of longitudinal panel data. In this research, we evaluated the reproductive calendar using data from the Performance Monitoring for Action Project. We used population-based longitudinal data from nine settings in seven countries: Burkina Faso, Nigeria (Kano and Lagos States), Democratic Republic of Congo (Kinshasa and Kongo Central Provinces), Kenya, Uganda, Cote d'Ivoire, and India. To evaluate reliability, we compared the baseline cross-sectional report of contraceptive use (overall and by contraceptive method), nonuse, or pregnancy with the retrospective reproductive calendar entry for the corresponding month, measured at follow-up. We use multivariable regressions to identify characteristics associated with reliability or reporting. Overall, we find that the reliability of the calendar is in the “moderate/substantial” range for nearly all geographies and tests (Kappa statistics between 0.58 and 0.81). Measures of the complexity of the calendar (number of contraceptive use episodes, using the long-acting method at baseline) are associated with reliability. We also find that women who were using contraception without their partners/husband's knowledge (i.e., covertly) were less likely to report reliably in several countries.  相似文献   
2.
3.
4.
The purpose of this study was to provide an evidence base for colorectal cancer research activity that might influence policy, mainly at the national level. Improvements in healthcare delivery have lengthened life expectancy, but within a situation of increased cancer incidence. The disease burden of CRC has risen significantly, particularly in Africa, Asia and Latin America. Research is key to its control and reduction, but few studies have delineated the volume and funding of global research on CRC. We identified research papers in the Web of Science (WoS) from 2007 to 2021, and determined the contributions of the leading countries, the research domains studied, and their sources of funding. We identified 62 716 papers, representing 5.7% of all cancer papers. This percentage was somewhat disproportionate to the disease burden (7.7% in 2015), especially in Eastern Europe. International collaboration increased over the time period in almost all countries except in China. Genetics, surgery and prognosis were the leading research domains. However, research on palliative care and quality-of-life in CRC was lacking. In Western Europe, the main funding source was the charity sector, particularly in the UK, but in most other countries government played the leading role, especially in China and the USA. There was little support from industry. Several Asian countries provided minimal contestable funding, which may have reduced the impact of their CRC research. Certain countries must perform more CRC research overall, especially in domains such as screening, palliative care and quality-of-life. The private-non-profit sector should be an alternative source of support.  相似文献   
5.
The Extracellular Vesicle Flow Cytometry Working Group ( http://www.evflowcytometry.org ) is formed by members of the International Society for Extracellular Vesicles (ISEV), the International Society for Advancement of Cytometry (ISAC), and the International Society on Thrombosis and Haemostasis (ISTH). This working group of flow cytometry experts develops guidelines for best practices regarding flow cytometry detection of extracellular vesicles. To improve rigor and standardization, this working group published a framework outlining the minimal information to report about a flow cytometry experiment on extracellular vesicles (MIFlowCyt-EV) in the Journal of Extracellular Vesicles, the ISEV journal, in 2020. In parallel, an article explaining MIFlowCyt-EV was published in Cytometry Part A, one of the ISAC journals, and now will be introduced to the ISTH as an SSC Communication in the Journal of Thrombosis and Haemostasis. The goal of this SSC Communication is to explain why flow cytometry is becoming the instrument of choice to characterize single extracellular vesicles, the obstacles that have been identified and (mostly) overcome by developing procedures to calibrate flow cytometers, and the relevance of reporting minimal information to improve reliability and reproducibility of experiments in which flow cytometers are used for characterization of extracellular vesicles.  相似文献   
6.
7.
8.
9.
Cancer Causes & Control - Congenital malformations are strong risk factors for childhood cancer. Our objective was to determine whether cancer survival differs by birth defect status among...  相似文献   
10.
Perinatal factors have been associated with soft tissue sarcomas (STS) in case-control studies. However, (i) the contributions of factors including fetal growth remain unknown, ( ii ) these factors have not been examined in cohort studies and (iii) few assessments have evaluated risk in specific STS subtypes. We sought to identify the role of perinatal and familial factors on the risk of STS in a large population-based birth cohort. We identified 4,023,436 individuals in the Swedish Birth Registry born during 1973–2012. Subjects were linked to the Swedish Cancer Registry, where incident STS cases were identified. We evaluated perinatal and familial factors obtained from Statistics Sweden, including fetal growth, gestational age, and presence of a congenital malformation. Poisson regression was used to estimate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for associations between perinatal factors and STS overall, as well as by common subtypes. There were 673 individuals diagnosed with STS in 77.5 million person-years of follow-up. Having a congenital malformation was associated with STS (IRR = 1.70, 95% CI: 1.23–2.35). This association was stronger (IRR = 2.90, 95% CI: 1.25–6.71) in recent years (2000–2012). Low fetal growth was also associated with STS during the same time period (IRR = 1.86, 95% CI: 1.05–3.29). Being born preterm was associated with rhabdomyosarcoma (IRR = 1.74, 95% CI: 1.08–2.79). In our cohort study, those with congenital malformations and other adverse birth outcomes were more likely to develop a STS compared to their unaffected contemporaries. These associations may point to disrupted developmental pathways and genetic factors influencing the risk of STS.  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