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   2326篇
  免费   247篇
  国内免费   323篇
  2896篇
  2024年   12篇
  2023年   98篇
  2022年   93篇
  2021年   134篇
  2020年   120篇
  2019年   172篇
  2018年   125篇
  2017年   109篇
  2016年   133篇
  2015年   127篇
  2014年   146篇
  2013年   205篇
  2012年   162篇
  2011年   126篇
  2010年   96篇
  2009年   108篇
  2008年   105篇
  2007年   128篇
  2006年   98篇
  2005年   91篇
  2004年   61篇
  2003年   57篇
  2002年   60篇
  2001年   40篇
  2000年   32篇
  1999年   26篇
  1998年   24篇
  1997年   26篇
  1996年   25篇
  1995年   16篇
  1994年   20篇
  1993年   19篇
  1992年   11篇
  1991年   10篇
  1990年   8篇
  1989年   8篇
  1988年   7篇
  1987年   16篇
  1986年   4篇
  1985年   8篇
  1984年   7篇
  1983年   5篇
  1982年   4篇
  1981年   4篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   1篇
  1974年   2篇
排序方式: 共有2896条查询结果,搜索用时 0 毫秒
101.
Protecting confidentiality is an essential value in all human relationships, no less in medical practice and research.(1) Doctor-patient and researcher-participant relationships are built on trust and on the understanding those patients' secrets will not be disclosed.(2) However, this confidentiality can be breached in some situations where it is necessary to meet a strong conflicting duty.(3) Confidentiality, in a general sense, has received much interest in Islamic resources including the Qur'an, Sunnah and juristic writings. However, medical and research confidentiality have not been explored deeply. There are few fatwas about the issue, despite an increased effort by both individuals and Islamic medical organizations to use these institutional fatwas in their research. Infringements on confidentiality make up a significant portion of institutional fatwas, yet they have never been thoroughly investigated. Moreover, the efforts of organizations and authors in this regard still require further exploration, especially on the issue of research confidentiality. In this article, we explore medical and research confidentiality and potential conflicts with this practice as a result of fatwas released by international, regional, and national Islamic Sunni juristic councils. We discuss how these fatwas affect research and publication by Muslim doctors, researchers, and Islamic medical organizations. We argue that more specialized fatwas are needed to clarify Islamic juristic views about medical and research confidentiality, especially the circumstances in which infringements on this confidentiality are justified.  相似文献   
102.
Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway that polypeptide chain follows during co-translational folding to achieve its functional form is still an enigma. In order to understand this process and to determine the exact conformation of the co-translational folding intermediates, it is essential to develop techniques that allow the isolation of RNCs carrying nascent chains of predetermined sizes to allow their further structural analysis.SecM (secretion monitor) is a 170 amino acid E. coli protein that regulates expression of the downstream SecA (secretion driving) ATPase in the secM-secA operon6. Nakatogawa and Ito originally found that a 17 amino acid long sequence (150-FSTPVWISQAQGIRAGP-166) in the C-terminal region of the SecM protein is sufficient and necessary to cause stalling of SecM elongation at Gly165, thereby producing peptidyl-glycyl-tRNA stably bound to the ribosomal P-site7-9. More importantly, it was found that this 17 amino acid long sequence can be fused to the C-terminus of virtually any full-length and/or truncated protein thus allowing the production of RNCs carrying nascent chains of predetermined sizes7. Thus, when fused or inserted into the target protein, SecM stalling sequence produces arrest of the polypeptide chain elongation and generates stable RNCs both in vivo in E. coli cells and in vitro in a cell-free system. Sucrose gradient centrifugation is further utilized to isolate RNCs.The isolated RNCs can be used to analyze structural and functional features of the co-translational folding intermediates. Recently, this technique has been successfully used to gain insights into the structure of several ribosome bound nascent chains10,11. Here we describe the isolation of bovine Gamma-B Crystallin RNCs fused to SecM and generated in an in vitro translation system.  相似文献   
103.
104.
A workshop on 'Improving translation of animal models for nervous system disorders' held at the National Academy of Sciences, Institute of Medicine, in Washington, DC, 28-29 March 2012, was organized to discuss the issues that contribute to the poor translation of results from animal models to human nervous system disorders, to consider strategies to increase the scientific rigor of preclinical testing, to identify methods to maximize bidirectional translation between basic and clinical research, and to determine the next steps for improvement of the development and testing of animal models of nervous system disorders. The proceedings of this workshop will be of great interest to those doing research in genes, brain and behaviour.  相似文献   
105.
肠道是机体最大的生物库,定植着以细菌为主的种类繁多的微生物,共同构成肠道菌群。正常情况下肠道菌群与机体处于动态平衡,当各种原因引起肠道屏障功能损坏,致使细菌的数量、比例发生改变或空间上发生转移将引起肠道细菌移位,最终导致机体各种功能障碍。本文对肠道细菌移位的研究进行综述,为其防治提供相应的理论依据。  相似文献   
106.
107.
Elger BS 《Bioethics》2008,22(4):224-238
This article examines international and European regulations on research involving prisoners for consensus, differences, and their consequences, and offers a critical evaluation of the various approaches. Agreement exists that prisoners are at risk of coercion, which might interfere with their ability to provide voluntary informed consent to research. Controversy exists about the magnitude of this risk and the consequences that should follow from this risk. Two strategies are proposed for a method of protecting prisoners that does not lead to discrimination: first, more caution to assure non-coerced consent and second, restrictions on the type of research. Most regulations stress the importance of the principle of equivalence of healthcare in places of detention as part of an efficient protection against research risks and discrimination.
All the presented approaches have shortcomings. While 'over-use' of prisoners for research as compared to the general population is ethically unjustified, not granting prisoners access to studies beneficial to their own health because of over-strict regulations is equally unjustified. A middle solution should be preferred, one that grants a minimum of protection together with the lowest possible barriers. Research that does not entail a direct benefit for the individual detainee should be restricted to types of research that have a benefit for detainees as a group and that are of low risk. What will ultimately protect prisoners best, while producing the greatest benefit for them, is access to the same healthcare available to members of the community including research as a true option.  相似文献   
108.
Ehni HJ  Wiesing U 《Bioethics》2008,22(1):64-74
The ethical aspects of placebo control in clinical trials have been extensively and controversially debated in the last decade. However, a thorough analytical comparison of the different existing international regulations, their terminologies and their ethical principles concerning placebo, is still missing. The central issue in the ongoing controversy is the justification of placebo-use, if proven treatment exists. All present versions of the examined guidelines propose such justifications, but each guideline differs from the others in relevant details. Therefore the conditions justifying placebo-use according to each guideline are the focus of our attention. We will first propose a formalized general principle that defines the ethical acceptability of placebo-use. Then we will analyse three categories of conditions put forward by the different documents: the risk of harm or burden, compelling scientific reasons, and the availability of proven treatment. The analysis shows important normative discrepancies and contradictions between the examined guidelines. Especially striking is the fact that some guidelines allow the participants in clinical trials to be exposed to a risk of serious harm, while others do not. Finally, we try to show how the normative difference of each guideline could influence the decision of researchers or IRBs concerning the ethical acceptability of placebo-use.  相似文献   
109.
Di Jin  Porter Hoagland   《Harmful algae》2008,7(6):772-781
In this study, we develop a framework for measuring the value of harmful algal bloom (HAB) predictions. The framework captures the effects of both private and public responses to HABs. Using data from the New England nearshore commercial shellfish fishery and impact estimates for a large-scale HAB event in 2005, we illustrate how the potential value of HAB forecasts may be estimated. The results of our study suggest that the long-term value of a HAB prediction and tracking system for the Gulf of Maine is sensitive to the frequency of HAB events, the accuracy of predictions, the choice of HAB impact measures, and the effectiveness of public and private responses.  相似文献   
110.
Gene Ontology (GO) vocabularies are an established standard for linking functional information to genes and gene products (www.geneontology.org/). A recent collaboration between University College London and the European Bioinformatics Institute is providing GO annotation to human cardiovascular-associated genes (http://www.ucl.ac.uk/medicine/cardiovascular-genetics/geneontology.html). This report outlines the aims of this collaboration and summarizes how the cardiovascular community can help improve the quality and quantity of GO annotations. This new initiative is funded by the British Heart Foundation and fully supported by the GO Consortium.  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