全文获取类型
收费全文 | 887篇 |
免费 | 102篇 |
国内免费 | 65篇 |
出版年
2024年 | 6篇 |
2023年 | 14篇 |
2022年 | 38篇 |
2021年 | 48篇 |
2020年 | 36篇 |
2019年 | 48篇 |
2018年 | 62篇 |
2017年 | 35篇 |
2016年 | 46篇 |
2015年 | 62篇 |
2014年 | 60篇 |
2013年 | 64篇 |
2012年 | 65篇 |
2011年 | 57篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 29篇 |
2007年 | 32篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 41篇 |
2003年 | 29篇 |
2002年 | 38篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有1054条查询结果,搜索用时 31 毫秒
61.
62.
Vascular leak syndrome (VLS) is a common and often fatal sequela of multiple bone traumas, and of infectious, toxic, and allergic insults in human patients. Although an animal model for VLS has not been fully established, rats have shown sensitivity to the syndrome that approximates that of the human population. We describe cases of VLS in three-month-old adult and one-month-old Sprague-Dawley rats in an osteogenesis study aimed at optimizing correction of bone hypoplasias and other craniofacial deformities in children, using a mandibular distraction device. In the study reported here, VLS was diagnosed in 40% of the rats that were necropsied after dying or being euthanized early, subsequent to mandibular osteotomy, a procedure that involves minimal bone trauma. The gross and histologic findings, as well as the clinical course of VLS in the rats of the osteogenesis study, were similar to those of documented human cases. Hence, the rat may be a useful animal model to h elp characterize the physiologic and molecular events that accompany this syndrome. 相似文献
63.
64.
Zi tara MS Arndt A Geets A Hellemans B Volckaert FA 《The Journal of parasitology》2000,86(6):1368-1373
The primary structure of the ribosomal DNA internal transcribed spacers (ITS-1 and ITS-2) and 5.8S rRNA gene were used to characterize and identify 2 monogenean species of Gyrodacrylus living externally on the threespine stickleback (Gasterosteus aculeatus). The ITS region was amplified by PCR from freshwater, brackish, and marine isolates of Gyrodactylus arcuatus and G. branchicus, and the ends of the coding regions were identified by comparative alignment. No intraspecific and very low interspecific variation were observed in the 5.8S rRNA gene; high inter- and low intraspecific variation were revealed in the ITS-1 and ITS-2 regions. The morphological species identification was in all cases confirmed by the molecular identification. Intraspecifically, samples from 2 locations in the North Sea could be differentiated, but the Baltic sample resembled North Sea genotypes. Our approach offers perspectives for a multimetric genetical, morphometrical, and ecological taxonomy of the genus Gyrodactylus. 相似文献
65.
东喜马拉雅地区雀儿豆属的修订 总被引:2,自引:0,他引:2
本文依据形态特征对分布于东喜马拉雅地区的雀区豆属植物进行了研究,认为荚果圆柱形,长圆形并且果皮具海绵状结构非该类植物所特有;垫状生活型则是植物对高山带,荒砾质带生态适应的结果。 相似文献
66.
67.
Zi Feng Yang Chris Ka Pun Mok Xiao Qing Liu Xiao Bo Li Jian Feng He Wen Da Guan Yong Hao Xu Wei Qi Pan Li Yan Chen Yong Ping Lin Shi Guan Wu Si Hua Pan Ji Cheng Huang Guo Yun Ding Kui Zheng Chang Wen Ke Jin Yan Lin Yong Hui Zhang Horace Hok Yeung Lee Wen Kuan Liu Chun Guang Yang Rong Zhou Joseph Sriyal Malik Peiris Yi Min Li Rong Chang Chen Ling Chen Nan Shan Zhong 《PloS one》2015,10(2)
BackgroundThe second wave of avian influenza H7N9 virus outbreak in humans spread to the Guangdong province of China by August of 2013 and this virus is now endemic in poultry in this region.MethodsFive patients with H7N9 virus infection admitted to our hospital during August 2013 to February 2014 were intensively investigated. Viral load in the respiratory tract was determined by quantitative polymerase chain reaction (Q-PCR) and cytokine levels were measured by bead-based flow cytometery.ResultsFour patients survived and one died. Viral load in different clinical specimens was correlated with cytokine levels in plasma and broncho-alveolar fluid (BALF), therapeutic modalities used and clinical outcome. Intravenous zanamivir appeared to be better than peramivir as salvage therapy in patients who failed to respond to oseltamivir. Higher and more prolonged viral load was found in the sputum or endotracheal aspirates compared to throat swabs. Upregulation of proinflammatory cytokines IP-10, MCP-1, MIG, MIP-1α/β, IL-1β and IL-8 was found in the plasma and BALF samples. The levels of cytokines in the plasma and viral load were correlated with disease severity. Reactivation of herpes simplex virus type 1(HSV-1) was found in three out of five patients (60%).ConclusionExpectorated sputum or endotracheal aspirate specimens are preferable to throat swabs for detecting and monitoring H7N9 virus. Severity of the disease was correlated to the viral load in the respiratory tract as well as the extents of cytokinemia. Reactivation of HSV-1 may contribute to clinical outcome. 相似文献
68.
Backgrounds
The psychological distress of medical students is a major concern of public health worldwide. However, few studies have been conducted to evaluate anxiety symptoms of medical students in China. The purpose of this study was to investigate the anxiety symptoms among Chinese medical students, to examine the relationships between big five personality traits and anxiety symptoms among medical students, and to explore the mediating role of resilience in these relationships.Methods
This multicenter cross-sectional study was conducted in June 2014. Self-reported questionnaires consisting of the Zung Self-Rating Anxiety Scale (SAS), Big Five Inventory (BFI), Wagnild and Young Resilience Scale (RS-14) and demographic section were distributed to the subjects. A stratified random cluster sampling method was used to select 2925 medical students (effective response rate: 83.57%) at four medical colleges and universities in Liaoning province, China. Asymptotic and resampling strategies were used to explore the mediating role of resilience.Results
The prevalence of anxiety symptoms was 47.3% (SAS index score≥50) among Chinese medical students. After adjusting for the demographic factors, the traits of agreeableness, conscientiousness and openness were all negatively associated with anxiety whereas neuroticism was positively associated with it. Resilience functioned as a mediator in the relationships between agreeableness/conscientiousness/openness and anxiety symptoms.Conclusions
Among Chinese medical students, the prevalence of anxiety symptoms was high and resilience mediated the relationships between big five personality traits and anxiety symptoms. Identifying at-risk individuals and undertaking appropriate intervention strategies that focus on both personality traits and resilience might be more effective to prevent and reduce anxiety symptoms. 相似文献69.
Inga Sandrock Natalia Zi?tara Marcin ?yszkiewicz Linda Oberd?rfer Katrin Witzlau Andreas Krueger Immo Prinz 《PloS one》2015,10(12)
Thymic development of αβ T lymphocytes into invariant natural killer (NK) T cells depends on their selection via agonistic lipid antigen presented by CD1d. If successful, newly selected NKT cells gain effector functions already in the thymus. Some γδ T cell subsets also acquire effector functions in the thymus. However, it is not clear whether agonistic TCR stimulation is involved in thymic γδ T cell selection and development. Here we combine two genetic models to address this question. MiR-181a/b-1–/–mice, which show impaired agonistic T cell selection of invariant αβ NKT cells, were crossed to Tcrd-H2BeGFP reporter mice to monitor selection, intra-thymic expansion and differentiation of γδ T cells. We found that miR-181a/b-1-deficiency had no effect on numbers of thymic γδ T cell or on their differentiation towards an IL-17- or IFN-γ-producing effector phenotype. Also, the composition of peripheral lymph node γδ T cells was not affected by miR-181a/b-1-deficiency. Dendritic epidermal γδ T cells were normally present in knock-out animals. However, we observed elevated frequencies and numbers of γδ NKT cells in the liver, possibly because γδ NKT cells can expand and replace missing αβ NKT cells in peripheral niches. In summary, we investigated the role of miR-181a/b-1 for selection, intrathymic development and homeostasis of γδ T cells. We conclude that miR-181a/b-1-dependent modulation of T cell selection is not critically required for innate development of γδ NKT cells or of any other γδ T cell subtypes. 相似文献
70.
Peng Xu Huiru Chen Ting Li Feng Xu Zhilei Mao Xiaoli Cao Langxi Miao Shasha Du Jie Hua Jiachen Zhao Tongtong Guo Shuang Kou Wenxiu Wang Hong-Quan Yang 《The Plant cell》2021,33(7):2375
Cryptochromes are blue light photoreceptors that mediate various light responses in plants and mammals. In Arabidopsis (Arabidopsis thaliana), cryptochrome 1 (CRY1) mediates blue light-induced photomorphogenesis, which is characterized by reduced hypocotyl elongation and enhanced anthocyanin production, whereas gibberellin (GA) signaling mediated by the GA receptor GA-INSENSITIVE DWARF1 (GID1) and DELLA proteins promotes hypocotyl elongation and inhibits anthocyanin accumulation. Whether CRY1 control of photomorphogenesis involves regulation of GA signaling is largely unknown. Here, we show that CRY1 signaling involves the inhibition of GA signaling through repression of GA-induced degradation of DELLA proteins. CRY1 physically interacts with DELLA proteins in a blue light-dependent manner, leading to their dissociation from SLEEPY1 (SLY1) and the inhibition of their ubiquitination. Moreover, CRY1 interacts directly with GID1 in a blue light-dependent but GA-independent manner, leading to the inhibition of the interaction between GID1 with DELLA proteins. These findings suggest that CRY1 controls photomorphogenesis through inhibition of GA-induced degradation of DELLA proteins and GA signaling, which is mediated by CRY1 inhibition of the interactions of DELLA proteins with GID1 and SCFSLY1, respectively.Blue light-dependent interactions of CRY1 with GID1 and DELLA proteins inhibit gibberellin (GA)-induced degradation of DELLA proteins to regulate GA signaling and photomorphogenesis. 相似文献