全文获取类型
收费全文 | 490篇 |
免费 | 10篇 |
国内免费 | 313篇 |
出版年
2022年 | 18篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 23篇 |
2018年 | 12篇 |
2017年 | 57篇 |
2016年 | 54篇 |
2015年 | 37篇 |
2014年 | 25篇 |
2013年 | 3篇 |
2012年 | 41篇 |
2011年 | 32篇 |
2010年 | 29篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 26篇 |
2006年 | 26篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 22篇 |
2000年 | 34篇 |
1999年 | 40篇 |
1998年 | 19篇 |
1997年 | 26篇 |
1996年 | 20篇 |
1995年 | 28篇 |
1994年 | 31篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 47篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1970年 | 2篇 |
1964年 | 2篇 |
1963年 | 2篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有813条查询结果,搜索用时 15 毫秒
721.
722.
723.
Bolotin S Pebody R White PJ McMenamin J Perera L Nguyen-Van-Tam JS Barlow T Watson JM;UK Severe Influenza Surveillance System 《PloS one》2012,7(1):e30279
Background
The World Health Organization and European Centre for Disease Prevention and Control have highlighted the importance of establishing systems to monitor severe influenza. Following the H1N1 (2009) influenza pandemic, a sentinel network of 23 Trusts, the UK Severe Influenza Surveillance System (USISS), was established to monitor hospitalisations due to confirmed seasonal influenza in England. This article presents the results of the first season of operation of USISS in 2010/11.Methodology/Principal Findings
A case was defined as a person hospitalised with confirmed influenza of any type. Weekly aggregate numbers of hospitalised influenza cases, broken down by flu type and level of care, were submitted by participating Trusts. Cases in 2010/11 were compared to cases during the 2009 pandemic in hospitals with available surveillance data for both time periods (n = 19). An unexpected resurgence in seasonal A/H1N1 (2009) influenza activity in England was observed in December 2010 with reports of severe disease. Reported cases over the period of 4 October 2010 to 13 February 2011 were mostly due to influenza A/H1N1 (2009). One thousand and seventy-one cases of influenza A/H1N1 (2009) occurred over this period compared to 409 at the same Trusts over the 2009/10 pandemic period (1 April 2009 to 6 January 2010). Median age of influenza A/H1N1 (2009) cases in 2010/11 was 35 years, compared with 20 years during the pandemic (p = <0.0001).Conclusions/Significance
The Health Protection Agency successfully established a sentinel surveillance system for severe influenza in 2010/11, detecting a rise in influenza cases mirroring other surveillance indicators. The data indicate an upward shift in the age-distribution of influenza A/H1N1 (2009) during the 2010/11 influenza season as compared to the 2009/10 pandemic. Systems to enable the ongoing surveillance of severe influenza will be a key component in understanding and responding to the evolving epidemiology of influenza in the post-pandemic era. 相似文献724.
725.
726.
Hansen HV Christensen EM Dam H Gluud C Wetterslev J Kessing LV;Early Intervention Affective Disorders 《PloS one》2012,7(3):e32950
Background
Little is known on whether centralised and specialised combined pharmacological and psychological intervention in the early phase of severe unipolar depression improve prognosis. The aim of the present study was to assess the benefits and harms of centralised and specialised secondary care intervention in the early course of severe unipolar depression.Methods
A randomised multicentre trial with central randomisation and blinding in relation to the primary outcome comparing a centralised and specialised outpatient intervention program with standard decentralised psychiatric treatment. The interventions were offered at discharge from first, second, or third hospitalisation due to a single depressive episode or recurrent depressive disorder. The primary outcome was time to readmission to psychiatric hospital. The data on re-hospitalisation was obtained from the Danish Psychiatric Central Register. The secondary and tertiary outcomes were severity of depressive symptoms according to the Major Depression Inventory, adherence to medical treatment, and satisfaction with treatment according to the total score on the Verona Service Satisfaction Scale-Affective Disorder (VSSS-A). These outcomes were assessed using questionnaires one year after discharge from hospital.Results
A total of 268 patients with unipolar depression were included. There was no significant difference in the time to readmission (unadjusted hazard ratio 0.89, 95% confidence interval 0.60 to 1.32; log rank: χ2 = 0.3, d.f. = 1, p = 0.6); severity of depressive symptoms (mood disorder clinic: median 21.6, quartiles 9.7–31.2 versus standard treatment: median 20.2, quartiles 10.0–29.8; p = 0.7); or the prevalence of patients in antidepressant treatment (73.9% versus 80.0%, p = 0.2). Centralised and specialised secondary care intervention resulted in significantly higher satisfaction with treatment (131 (SD 31.8) versus 107 (SD 25.6); p<0.001).Conclusions
Centralised and specialised secondary care intervention in the early course of severe unipolar depression resulted in no significant effects on time to rehospitalisation, severity of symptoms, or use of antidepressants, but increased patient satisfaction.Trial Registration
ClinicalTrials.gov NCT00253071相似文献727.
Gyula O András B Zoltán B Katalin B Attila C Janos F Maria G Akos H Lászlo K Lászlo K Gabor K Gyorgy L Judit M Tamas MF Zsuzsa M Pál R Zsolt O János S Zoltán S István S Klára S Jozsef T Edina T;NEFMI - Nemzeti Erőforrás Minisztérium Department of Human Resources) 《Magyar onkologia》2012,56(2):114-132
728.
蛋白磷酸酶催化的蛋白质可逆磷酸化反应是叶片衰老的关键环节。该研究筛选并克隆了1个新的参与水稻(Oryza sativa)叶片衰老调控的PP2C基因OsSAPP3。研究表明, OsSAPP3的启动子在ProOsSAPP3-GUS转基因拟南芥(Arabidopsis thaliana)的莲座叶中有活性, 并且活性以依赖叶龄方式增加。利用CaMV 35S启动子驱动组成型异源过表达OsSAPP3导致转基因拟南芥无法正常生长。用可诱导型启动子GVG系统驱动OsSAPP3异源过表达导致转基因拟南芥出现莲座叶变小、数量增加、叶片早衰及抽薹开花提前等早衰表型。外源诱导OsSAPP3基因异源过表达后, 利用实时荧光定量PCR检测到SAG12、WRKY6和NAC2等衰老标志基因显著上调表达。研究结果表明, OsSAPP3是参与水稻叶片衰老的正向调控因子。 相似文献
729.
怀山药(Dioscorea opposita)遗传转化是对其进行基因功能分析和遗传改良的基础, 但目前国内外尚未见相关报道。以怀山药优良品种铁棍山药(D. opposita cv. ‘Tiegun’)的微型块茎为受体材料, 对影响遗传转化的因素进行优化, 建立了由根癌农杆菌介导的山药遗传转化体系。过表达质粒载体pCAMBIA1301-DoSERK2含GUS标记基因和潮霉素(Hyg)抗性筛选基因, 沉默质粒载体pART27-DoSERK2含卡那霉素(Kan)抗性筛选基因。根癌农杆菌抑制剂特美汀(Tim)的最佳浓度为500 mg·L -1; 再生芽和生根时, Hyg的最佳浓度分别为15和20 mg·L -1, Kan的最佳浓度分别为120和160 mg·L -1。对转化植株进行PCR和GUS组织化学检测, 结果显示外源基因已整合到铁棍山药转基因株系的基因组中并在细胞中表达。该研究建立了一套取材便利的铁棍山药遗传转化方法, 对其它品种山药的转化也具有参考价值。 相似文献
730.
为鉴定水稻(Oryza sativa)响应缺铁的根冠长距离信号转导物质, 采用TMT标记技术分析了不同浓度铁处理下水稻韧皮部汁液的蛋白质组学变化, 共鉴定出206个差异蛋白, 其中54个蛋白表达丰度上调, 152个蛋白表达丰度下调。差异蛋白的KEGG通路分类主要包括激素信号代谢、谷胱甘肽代谢、碳代谢以及mRNA转运等代谢途径。此外, 对差异蛋白对应的生理指标进行测定, 发现激素、蔗糖、谷胱甘肽和转运蛋白等在缺铁条件下变化显著, 后续对这些差异蛋白的功能研究有助于揭示水稻响应铁素营养的长距离信号途径。 相似文献