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   1807篇
  免费   183篇
  国内免费   293篇
  2024年   5篇
  2023年   83篇
  2022年   61篇
  2021年   102篇
  2020年   96篇
  2019年   137篇
  2018年   90篇
  2017年   87篇
  2016年   111篇
  2015年   97篇
  2014年   119篇
  2013年   163篇
  2012年   123篇
  2011年   108篇
  2010年   70篇
  2009年   83篇
  2008年   84篇
  2007年   110篇
  2006年   90篇
  2005年   71篇
  2004年   54篇
  2003年   41篇
  2002年   43篇
  2001年   32篇
  2000年   27篇
  1999年   17篇
  1998年   21篇
  1997年   16篇
  1996年   13篇
  1995年   14篇
  1994年   11篇
  1993年   10篇
  1992年   9篇
  1991年   10篇
  1990年   8篇
  1989年   7篇
  1988年   3篇
  1987年   15篇
  1986年   2篇
  1985年   3篇
  1983年   7篇
  1982年   6篇
  1981年   3篇
  1980年   2篇
  1979年   2篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1974年   3篇
  1952年   1篇
排序方式: 共有2283条查询结果,搜索用时 15 毫秒
41.
Alec Walen 《Bioethics》2020,34(9):899-905
Subjects in studies on humans are used as a means of conducting the research and achieving whatever good would justify putting them at risk. Accordingly, consent must normally be obtained before subjects are exposed to any substantial risks to their welfare. Bystanders are also often put at risk, but they are not used as a means. Accordingly—or so I argue—consent is more often unnecessary before bystanders are exposed to similar substantial risks to their welfare.  相似文献   
42.
Daniel Wikler 《Bioethics》2020,34(9):937-940
Scientists seeking to conduct research with human subjects must first submit their proposals to research ethics committees (Institutional Review Boards [IRBs], in the United States). Some of these studies pose risks to “bystanders,” i.e., people who may be affected by the research but who are not enrolled as study subjects. Should IRBs expand their scope to include oversight over possible harms to bystanders as well as research subjects? This paper presents arguments against this step. Prior review of research with human subjects, despite its evident burden on the research enterprise, is a necessary caution, because the tension between the objectives of humane treatment of research subjects and sound scientific design and procedure has in the past led to serious abuses. This rationale is inapplicable in the case of bystanders. Moreover, in view of the many and varied effects of both research practices and scientific advances on the broader public over time, those who may be considered to be “bystanders” may potentially expand without limit; requiring IRBs to anticipate these distant and long-term effects as part of prior ethical review could greatly increase its burden and its deterrent effect on research. While conducting research without concern for serious potential harm to bystanders may be irresponsible and unethical, expanding the scope of prior review by IRBs to include risks to bystanders is not required by the principles governing human subjects research, and the costs and burdens of this expansion may outweigh any expected gains.  相似文献   
43.
蝉花是我国重要药用真菌,但长期以来其名称特别是学名的使用一直混乱。本文从古代医药典籍记载确认,“蝉花”是历史最久、使用最广的中名,对于其他中名具有优先权。其学名Isaria cicadae系Miquel(1838)根据巴西标本命名,但模式标本已失,原描述文字及插图均极其简单,与蝉花形态差异较大。其有性型迄今未发现,曾先后被认为是小蝉草Ophiocordyceps sobolifera和大蝉草Tolypocladium dujiaolongae (=Cordyceps cicadae Shing)。本文根据文献考证澄清了国内外关于小蝉草和大蝉草的误用,分析了长期以来大量日本文献中的命名混乱对我国认知蝉花的影响,并质疑I. cicadae在中国及其他地区的分布,提出它是一复合种,因此蝉花的分类地位及学名需要进一步研究。  相似文献   
44.
Psychiatric genomics research with African populations comes with a range of practical challenges around translation of psychiatric genomics research concepts, procedures, and nosology. These challenges raise deep ethical issues particularly around legitimacy of informed consent, a core foundation of research ethics. Through a consideration of the constitutive function of language, the paper problematises like‐for‐like, designative translations which often involve the ‘indigenization’ of English terms or use of metaphors which misrepresent the risks and benefits of research. This paper argues that effective translation of psychiatric genomics research terminology in African contexts demands substantive engagement with African conceptual schemas and values. In developing attenuated forms of translational thinking, researchers may recognise the deeper motivational reasons behind participation in research, highlighting the possibility that such reasons may depart from the original meaning implied within informed consent forms. These translational issues might be ameliorated with a critical re‐examination of how researchers develop and present protocols to institutional ethics review boards.  相似文献   
45.
在武汉发生的由新型冠状病毒SARS-CoV-2引发的人类冠状病毒病COVID-19,仅仅2个多月时间在我国及国际上70多个国家出现迅速传播,致病和死亡率高,人类生命受到了极大威胁。一些科学家火速投入研究,对SARS-CoV-2的来源和进化、形态特征和基因结构、感染和致病分子机制开展深入研究,取得了重大进展,为科学防控COVID-19提供了重要依据。根据上述研究的基础,文中对COVID-19病毒疫苗、抗体和抑制剂研发提出了设想,在研究防控COVID-19核心技术上具有一定的参考价值。  相似文献   
46.
研究《本草图经》中记载的中药杜衡,通过查阅历代书籍和现代文献记载,对其名称、形态、地理分布、功效、药图进行考证,探究其原植物品种。结果表明,《本草图经》中记载的杜衡其原植物可能包含马兜铃科细辛属植物杜衡(Asarum forbesii Maxim)和小叶马蹄香(Asarum ichangense C. Y. Cheng et C. S. Yang)两种,该结果可为充分认识中药杜衡的基原植物提供新的佐证,为中药杜衡的临床应用提供参考。  相似文献   
47.
Agricultural management recommendations based on short‐term studies can produce findings inconsistent with long‐term reality. Here, we test the long‐term environmental sustainability and profitability of continuous no‐till agriculture on yield, soil water availability, and N2O fluxes. Using a moving window approach, we investigate the development and stability of several attributes of continuous no‐till as compared to conventional till agriculture over a 29‐year period at a site in the upper Midwest, US. Over a decade is needed to detect the consistent effects of no‐till. Both crop yield and soil water availability required 15 years or longer to generate patterns consistent with 29‐year trends. Only marginal trends for N2O fluxes appeared in this period. Relative profitability analysis suggests that after initial implementation, 86% of periods between 10 and 29 years recuperated the initial expense of no‐till implementation, with the probability of higher relative profit increasing with longevity. Importantly, statistically significant but misleading short‐term trends appeared in more than 20% of the periods examined. Results underscore the importance of decadal and longer studies for revealing consistent dynamics and emergent outcomes of no‐till agriculture, shown to be beneficial in the long term.  相似文献   
48.
Retention forestry, which retains a portion of the original stand at the time of harvesting to maintain continuity of structural and compositional diversity, has been originally developed to mitigate the impacts of clear‐cutting. Retention of habitat trees and deadwood has since become common practice also in continuous‐cover forests of Central Europe. While the use of retention in these forests is plausible, the evidence base for its application is lacking, trade‐offs have not been quantified, it is not clear what support it receives from forest owners and other stakeholders and how it is best integrated into forest management practices. The Research Training Group ConFoBi (Conservation of Forest Biodiversity in Multiple‐use Landscapes of Central Europe) focusses on the effectiveness of retention forestry, combining ecological studies on forest biodiversity with social and economic studies of biodiversity conservation across multiple spatial scales. The aim of ConFoBi is to assess whether and how structural retention measures are appropriate for the conservation of forest biodiversity in uneven‐aged and selectively harvested continuous‐cover forests of temperate Europe. The study design is based on a pool of 135 plots (1 ha) distributed along gradients of forest connectivity and structure. The main objectives are (a) to investigate the effects of structural elements and landscape context on multiple taxa, including different trophic and functional groups, to evaluate the effectiveness of retention practices for biodiversity conservation; (b) to analyze how forest biodiversity conservation is perceived and practiced, and what costs and benefits it creates; and (c) to identify how biodiversity conservation can be effectively integrated in multi‐functional forest management. ConFoBi will quantify retention levels required across the landscape, as well as the socio‐economic prerequisites for their implementation by forest owners and managers. ConFoBi's research results will provide an evidence base for integrating biodiversity conservation into forest management in temperate forests.  相似文献   
49.
Choosing what scientific project to pursue is the most important decision that scientists at all levels continually face. Time devoted to a project can further desirable knowledge and advance a career or cost years in lost opportunity. Knowing what to consider before embarking on a specific scientific journey, as well as when to drop a project and change course, offers a way of practicing science that keeps us mindful of what is relevant at a given time and place while preserving our freedom to explore the most exciting findings. This article explores both the pressures that restrict this delicate decision-making process and the processes that scientists can apply to overcome those pressures. Above all else, as it turns out, we must still love the pursuit of knowledge for its own sake – and this love directly impacts our results.  相似文献   
50.
课程思政是当前高校落实“立德树人”根本任务的重要形式。在抗击新型冠状病毒肺炎疫情中,中华民族同舟共济、守望相助,共同铸就了伟大的抗疫精神,为课程思政教学提供了最生动的元素。本文对“战疫”行动中的抗疫精神进行梳理和总结,将其内涵凝练为5项内容;以新型冠状病毒的“核酸检测、疫苗研制及其变异”中蕴含的“抗疫精神”为思政载体,甄选“基因工程”课程中对应的理论内容,开展聚焦抗疫精神的“基因工程”课程思政教学设计与实践研究,利用问卷法和深度访谈法对教学实施效果进行评价,旨在引导学生在学习专业理论知识的同时,感悟课程内容中蕴含的抗疫精神,并将其内化为价值追求,潜移默化中提升学生的思想意识和道德修养,同时为生物类其他专业课程思政教学提供参考和借鉴。  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