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   709篇
  免费   40篇
  749篇
  2022年   11篇
  2021年   8篇
  2020年   8篇
  2019年   8篇
  2018年   12篇
  2017年   7篇
  2016年   16篇
  2015年   17篇
  2014年   32篇
  2013年   27篇
  2012年   52篇
  2011年   38篇
  2010年   30篇
  2009年   13篇
  2008年   32篇
  2007年   30篇
  2006年   18篇
  2005年   32篇
  2004年   26篇
  2003年   34篇
  2002年   23篇
  2001年   12篇
  2000年   17篇
  1999年   7篇
  1998年   6篇
  1997年   5篇
  1996年   9篇
  1995年   4篇
  1994年   8篇
  1993年   6篇
  1992年   15篇
  1991年   16篇
  1990年   10篇
  1989年   11篇
  1988年   10篇
  1987年   6篇
  1986年   7篇
  1985年   8篇
  1984年   20篇
  1983年   8篇
  1982年   6篇
  1978年   6篇
  1977年   4篇
  1976年   4篇
  1975年   8篇
  1972年   5篇
  1971年   4篇
  1970年   6篇
  1963年   4篇
  1940年   3篇
排序方式: 共有749条查询结果,搜索用时 15 毫秒
21.
22.
This study evaluates the conflict between patient confidentiality and partner notification in sero‐discordant relationships, and argues the thesis that based on a theoretical formulation of Ubuntu, a health provider is obliged to facilitate friendly relationships in which individuals are true subjects and/or objects of communal friendship. In serodiscordant relationships, the health professional can fulfil this obligation by notifying “others” (particularly a partner with whom an HIV positive patient has a “present” and “actual relationship”) of their spouse's HIV seroconversion, since without such relevant information a partner (subject) of an HIV positive patient cannot “appropriately” care for the patient's condition (object). There is a need to move away from the medical traditional emphasis that has for so long put primacy on doctor‐patient confidentiality as is the case with the Health Professions Council of South Africa Guidelines (Booklet 12) which favours patient confidentiality over partner notification. Given empirical evidence to support effectiveness of partner notification amongst sero‐discordant couples, there is thus, a need to focus emphasis on latter. This shift is necessary for achieving the United Nations’ Sustainable Development of Goal of ending HIV/AIDS epidemic by 2030. I proposed in this study that African ethics, specifically Ubuntu, will do a better job than current ethical frameworks at ensuring that partner notification receives more emphasis in the care of serodiscordant couples. If this framework is integrated into ethical guidelines and codes, it would significantly enhance the care of serodiscordant couples, as well as further boost global effort at ending HIV/AIDS epidemic by 2030.  相似文献   
23.
Radiation and Environmental Biophysics - Ionizing radiation produces reactive oxygen species (ROS) leading to cellular DNA damage. Therefore, patients undergoing radiation therapy or first...  相似文献   
24.
The Na,K-ATPase is specifically inhibited by cardiotonic steroids (CTSs) like digoxin and is of significant therapeutic value in the treatment of congestive heart failure and arrhythmia. Recently, new interest has arisen in developing Na,K-ATPase inhibitors as anticancer agents. In the present study, we compare the potency and rate of inhibition as well as the reactivation of enzyme activity following inhibition by various cardiac glycosides and their aglycones at different pH values using shark Na,K-ATPase stabilized in the E2MgPi or in the E2BeFx conformations. The effects of the number and nature of various sugar residues as well as changes in the positions of hydroxyl groups on the β-side of the steroid core of cardiotonic steroids were investigated by comparing various cardiac glycoside compounds like ouabain, digoxin, digitoxin, and gitoxin with their aglycones. The results confirm our previous hypothesis that CTS binds primarily to the E2-P ground state through an extracellular access channel and that binding of extracellular Na+ ions to K+ binding sites relieved the CTS inhibition. This reactivation depended on the presence or absence of the sugar moiety on the CTS, and a single sugar is enough to impede reactivation. Finally, increasing the number of hydroxyl groups of the steroid was sterically unfavorable and was found to decrease the inhibitory potency and to confer high pH sensitivity, depending on their position on the steroid β-face. The results are discussed with reference to the recent crystal structures of Na,K-ATPase in the unbound and ouabain-bound states.  相似文献   
25.
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental and occupational toxicants, which are a major human health concern in the U.S. and abroad. Previous research has focused on the genotoxic events caused by high molecular weight PAHs, but not on non-genotoxic events elicited by low molecular weight PAHs. We used an isomeric pair of low molecular weight PAHs, namely 1-Methylanthracene (1-MeA) and 2-Methylanthracene (2-MeA), in which only 1-MeA possessed a bay-like region, and hypothesized that 1-MeA, but not 2-MeA, would affect non-genotoxic endpoints relevant to tumor promotion in murine C10 lung cells, a non-tumorigenic type II alveolar pneumocyte and progenitor cell type of lung adenocarcinoma. The non-genotoxic endpoints assessed were dysregulation of gap junction intercellular communication function and changes in the major pulmonary connexin protein, connexin 43, using fluorescent redistribution and immunoblots, activation of mitogen activated protein kinases (MAPK) using phosphospecific MAPK antibodies for immunoblots, and induction of inflammatory genes using quantitative RT-PCR. 2-MeA had no effect on any of the endpoints, but 1-MeA dysregulated gap junctional communication in a dose and time dependent manner, reduced connexin 43 protein expression, and altered membrane localization. 1-MeA also activated ERK1/2 and p38 MAP kinases. Inflammatory genes, such as cyclooxygenase 2, and chemokine ligand 2 (macrophage chemoattractant 2), were also upregulated in response to 1-MeA only. These results indicate a possible structure-activity relationship of these low molecular weight PAHs relevant to non-genotoxic endpoints of the promoting aspects of cancer. Therefore, our novel findings may improve the ability to predict outcomes for future studies with additional toxicants and mixtures, identify novel targets for biomarkers and chemotherapeutics, and have possible implications for future risk assessment for these PAHs.  相似文献   
26.
BackgroundResearch on sleep after stroke has focused mainly on sleep disordered breathing. However, the extend to which sleep physiology is altered in stroke survivors, how these alterations compare to healthy volunteers, and how sleep changes might affect recovery as well as physical and mental health has yet to be fully researched. Motivated by the view that a deeper understanding of sleep in stroke is needed to account for its role in health and well-being as well as its relevance for recovery and rehabilitation, we conducted a systematic review and meta-analysis of polysomnographic studies comparing stroke to control populations.MethodMedline and PsycInfo databases were searched using "stroke" and words capturing polysomnographic parameters as search terms. This yielded 1692 abstracts for screening, with 15 meeting the criteria for systematic review and 9 for meta-analysis. Prisma best practice guidelines were followed for the systematic review; the Comprehensive Meta-Analysis software was used for random effects modelling.ResultsThe meta-analysis revealed that patients with stroke have poorer sleep than controls. Patients had lower sleep efficiency (mean 75% vs 84%), shorter total-sleep-time (309.4 vs 340.3 min) and more wake-after-sleep-onset (97.2 vs 53.8 min). Patients also spend more time in stage 1 (13% vs 10%) and less time in stage 2 sleep (36% vs 45%) and slow-wave-sleep (10% vs 12%). No group differences were identified for REM sleep. The systematic review revealed a strong bias towards studies in the early recovery phase of stroke, with no study reporting specifically on patients in the chronic state. Moreover, participants in the control groups included community samples as well as other patients groups.ConclusionsThese results indicate poorer sleep in patients with stroke than controls. While strongly suggestive in nature, the evidence base is limited and methodologically diverse, and hands a clear mandate for further research. A particular need regards polysomnographic studies in chronic community-dwelling patients compared to age-matched individuals.  相似文献   
27.
This study argues the thesis that a set of guidelines ‐ firmly rooted in a particular interpretation of African moral theory, specifically, Ubuntu – will do a better job than current medical ethics frameworks, in addressing ethical challenges around misattributed parentage within the clinical context. Incidental information such as information with significant personal/health implications raises unique challenges for medical professionals. For example, withholding information of misattributed paternity accidentally discovered in clinical interactions may be seen by a patient as a violation of his/her right‐to‐know. Contrarily, disclosure where a patient has not requested information – or where establishing paternity is not the purpose of clinical visit/interaction – may be taken by the patient as a violation of his/her right ‘not‐to‐know’. Resolving these challenges remain a herculean task. African moral theory contains an under‐emphasized value for addressing such ethical challenges around misattributed parentage in the field of transplant. I seek to contribute this knowledge; and enhance clinician‐patient relationship. This study builds off three completed systematic reviews, which aimed to answer the following questions: “what are the ethical challenges regarding information health professionals face within the clinical contest?” and “what core aspects (or common themes) of Ubuntu can be identified in existing literature describing the same?” In this present study, I applied the definition of Ubuntu which captures the core aspects of the theory in ethical literature on the same, to address ethical issues around unsought information of misattributed parentage in the field of transplant.  相似文献   
28.
Expression of Hox genes located on different chromosomes is precisely regulated and synchronized during development. In order to test the hypothesis that the Hox loci might cluster in nuclear space in order to share regulatory components, we performed 3D FISH on cryosections of developing mouse embryos and differentiating embryoid bodies. We did not observe any instances of co-localization of 4 different Hox alleles. Instances of 2 different alleles touching each other were found in 20-47% of nuclei depending on the tissue. The frequency of such “kissing” events was not significantly different in cells expressing a high proportion of the Hox clusters when compared to cells expressing none or only a few Hox genes. We found that the HoxB and HoxC clusters, which are located in gene-rich regions, were involved more frequently in gene kissing in embryonic nuclei. In the case of HoxB, this observation correlated with the positioning of the corresponding chromosome towards the interior of the nucleus. Our results indicate that co-regulation of the different Hox clusters is not associated with co-localization of the loci at a single regulatory compartment and that the chromosomal context may influence the extent to which they contact each other in the nucleus.  相似文献   
29.
Research Methods and Procedures: High‐fat (HF) diet feeding can induce obesity and metabolic disorders in rodents that resemble the human metabolic syndrome. However, this dietary intervention is not standardized, and the HF‐induced phenotype varies distinctly among different studies. The question which HF diet type is best to model the metabolic deterioration seen in human obesity remains unclear. Therefore, in this review, metabolic data obtained with different HF diet approaches are compiled. Both whole‐body and organ‐specific diet effects are analyzed. Results: On the basis of these results, we conclude that animal fats and ω‐6/ω‐9‐containing plant oils can be used to generate an obese and insulin‐resistant phenotype in rodents, whereas fish oil‐fed animals do not develop these disorders. Discussion: Looking at the present data, it does not seem possible to define an ideal HF diet, and an exact definition of diet composition and a thorough metabolic characterization of the HF diet effects in a researcher's specific laboratory setting remains essential for metabolic studies with this model.  相似文献   
30.
1. Heme synthesis from delta-aminolevulinic acid (delta-ALA) in freshly isolated rat hepatocytes was maximal at 100 microM with a rate of approx. 7 nmol being synthesized per g wet weight cells. 2. Approximately 8% of synthesized heme was converted to bilirubin and 50% of the newly synthesized bilirubin was conjugated. 3. The ratio of di to monoconjugate was approx. 2.5. Incorporation of delta-ALA into bilirubin was increased by additional delta-ALA, heme and was also doubled in cells isolated from animals treated with CoCl2. 4. Bilirubin formation was inhibited approx. 90% by in vitro treatment with heme oxygenase inhibitors zinc and tin protoporphyrin.  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