全文获取类型
收费全文 | 9071篇 |
免费 | 627篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 43篇 |
儿科学 | 259篇 |
妇产科学 | 259篇 |
基础医学 | 1377篇 |
口腔科学 | 181篇 |
临床医学 | 1062篇 |
内科学 | 1763篇 |
皮肤病学 | 241篇 |
神经病学 | 1202篇 |
特种医学 | 221篇 |
外科学 | 736篇 |
综合类 | 70篇 |
一般理论 | 9篇 |
预防医学 | 824篇 |
眼科学 | 305篇 |
药学 | 571篇 |
中国医学 | 20篇 |
肿瘤学 | 578篇 |
出版年
2023年 | 79篇 |
2022年 | 119篇 |
2021年 | 212篇 |
2020年 | 190篇 |
2019年 | 223篇 |
2018年 | 275篇 |
2017年 | 219篇 |
2016年 | 226篇 |
2015年 | 278篇 |
2014年 | 306篇 |
2013年 | 475篇 |
2012年 | 755篇 |
2011年 | 728篇 |
2010年 | 383篇 |
2009年 | 352篇 |
2008年 | 654篇 |
2007年 | 611篇 |
2006年 | 561篇 |
2005年 | 532篇 |
2004年 | 492篇 |
2003年 | 457篇 |
2002年 | 446篇 |
2001年 | 73篇 |
2000年 | 44篇 |
1999年 | 66篇 |
1998年 | 86篇 |
1997年 | 74篇 |
1996年 | 68篇 |
1995年 | 46篇 |
1994年 | 52篇 |
1993年 | 44篇 |
1992年 | 38篇 |
1991年 | 26篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 26篇 |
1987年 | 32篇 |
1986年 | 31篇 |
1985年 | 23篇 |
1984年 | 26篇 |
1983年 | 27篇 |
1982年 | 25篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1978年 | 28篇 |
1977年 | 16篇 |
1976年 | 18篇 |
1975年 | 17篇 |
1971年 | 17篇 |
1970年 | 18篇 |
排序方式: 共有9721条查询结果,搜索用时 0 毫秒
51.
Laura M. Carlson Michelle Angrish Avanti V. Shirke Elizabeth G. Radke Brittany Schulz Andrew Kraft Richard Judson Grace Patlewicz Robyn Blain Cynthia Lin Nicole Vetter Courtney Lemeris Pamela Hartman Heidi Hubbard Xabier Arzuaga Allen Davis Laura V. Dishaw Ingrid L. Druwe Hillary Hollinger Ryan Jones J. Phillip Kaiser Lucina Lizarraga Pamela D. Noyes Michele Taylor Andrew J. Shapiro Antony J. Williams Kristina A. Thayer 《Environmental health perspectives》2022,130(5)
Background: Per- and polyfluoroalkyl substances (PFAS) are a large class of synthetic (man-made) chemicals widely used in consumer products and industrial processes. Thousands of distinct PFAS exist in commerce. The 2019 U.S. Environmental Protection Agency (U.S. EPA) Per- and Polyfluoroalkyl Substances (PFAS) Action Plan outlines a multiprogram national research plan to address the challenge of PFAS. One component of this strategy involves the use of systematic evidence map (SEM) approaches to characterize the evidence base for hundreds of PFAS.Objective: SEM methods were used to summarize available epidemiological and animal bioassay evidence for a set of PFAS that were prioritized in 2019 by the U.S. EPA’s Center for Computational Toxicology and Exposure (CCTE) for in vitro toxicity and toxicokinetic assay testing.Methods: Systematic review methods were used to identify and screen literature using manual review and machine-learning software. The Populations, Exposures, Comparators, and Outcomes (PECO) criteria were kept broad to identify mammalian animal bioassay and epidemiological studies that could inform human hazard identification. A variety of supplemental content was also tracked, including information on in vitro model systems; exposure measurement–only studies in humans; and absorption, distribution, metabolism, and excretion (ADME). Animal bioassay and epidemiology studies meeting PECO criteria were summarized with respect to study design, and health system(s) were assessed. Because animal bioassay studies with exposure duration (or reproductive/developmental study design) were most useful to CCTE analyses, these studies underwent study evaluation and detailed data extraction. All data extraction is publicly available online as interactive visuals with downloadable metadata.Results: More than 40,000 studies were identified from scientific databases. Screening processes identified 44 animal and 148 epidemiology studies from the peer-reviewed literature and 95 animal and 50 epidemiology studies from gray literature that met PECO criteria. Epidemiological evidence (available for 15 PFAS) mostly assessed the reproductive, endocrine, developmental, metabolic, cardiovascular, and immune systems. Animal evidence (available for 40 PFAS) commonly assessed effects in the reproductive, developmental, urinary, immunological, and hepatic systems. Overall, 45 PFAS had evidence across animal and epidemiology data streams.Discussion: Many of the PFAS were data poor. Epidemiological and animal evidence were lacking for most of the PFAS included in our search. By disseminating this information, we hope to facilitate additional assessment work by providing the initial scoping literature survey and identifying key research needs. Future research on data-poor PFAS will help support a more complete understanding of the potential health effects from PFAS exposures. https://doi.org/10.1289/EHP10343 相似文献
52.
53.
Miethbauer S Günther W Schmidtke KU Heiser I Gräfe S Gitter B Liebermann B 《Journal of natural products》2008,71(8):1371-1375
Both the phytopathogenic fungus Ramularia collo-cygni and the hyperparasite R. uredinicola biosynthesize a number of red and yellow anthraquinone derivatives called rubellins. The new compounds uredinorubellins I and II, which were isolated from R. uredinicola, contribute to understanding the biosynthesis pathway that leads from simple anthraquinones to the rubellins. In addition, we isolated for the first time such simple compounds as chrysophanol and helminthsporin from both Ramularia species. A blue compound isolated from the mycelium of R. collo-cygni was revealed to be a unique 9,4-anthracenedione derivative. Structure elucidation by (1)H and (13)C NMR of the new but unstable compound caeruleoramularin was possible only by feeding the fungus different labeled (13)C acetates. The photodynamic activity of the uredinorubellins was comparable to rubellin D, whereas chrysophanol and caeruleoramularin did not display such activity. 相似文献
54.
55.
56.
57.
58.
AIMS: To analyze diagnosis and treatment of four advanced abdominal pregnancies in a low-resource setting of a developing country. METHODS: Extrauterine pregnancies occurring between 1997 and 2003 were identified from hospital records of the Mikumi Health Center in Tanzania/East Africa. RESULTS: A total of 45 extrauterine pregnancies were diagnosed four of which were advanced and located in the abdominal cavity. At the time of diagnosis, pregnancies were at 33, 34, 36 and 39 weeks of gestation, respectively. All four mothers survived but three of four fetuses died. One child is alive and well three years after delivery. CONCLUSION: Abdominal pregnancy is rather difficult to detect in a low-resource setting of a developing country. Persistent abdominal pain and tenderness, as well as fetal movements in the upper abdomen associated with abnormal fetal lie, may lead to its diagnosis. Localizing the fetal heart sounds in the maternal epigastrium especially in patients with abdominal pain may also be helpful in diagnosing an abdominal pregnancy. In addition, the lack of cervical changes or a displaced cervix should lead to the suspicion of an abdominal pregnancy. 相似文献
59.
60.