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   96篇
  免费   6篇
  2021年   2篇
  2020年   1篇
  2018年   3篇
  2017年   1篇
  2016年   3篇
  2015年   1篇
  2014年   4篇
  2013年   4篇
  2012年   6篇
  2011年   7篇
  2010年   3篇
  2009年   2篇
  2008年   2篇
  2007年   5篇
  2006年   2篇
  2005年   2篇
  2004年   4篇
  2003年   5篇
  2002年   4篇
  2001年   1篇
  1999年   7篇
  1998年   4篇
  1997年   5篇
  1996年   1篇
  1995年   3篇
  1993年   1篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1984年   1篇
  1979年   3篇
  1978年   1篇
  1976年   1篇
  1971年   2篇
  1968年   2篇
排序方式: 共有102条查询结果,搜索用时 15 毫秒
41.
Mariann Saur 《Hydrobiologia》1990,193(1):261-270
The ability of males of Littorina littorea and L. saxatilis to discriminate between mates of different sex, species and size was examined. In partner choice experiments males of L. littorea had the possibility to initiate a copulation with either a female or a male. The males did not show a preference for either sex. There was therefore no evidence that they could determine the sex of a conspecific prior to copulation. The duration of intrasexual copulation was considerably shorter than for intersexual copulation, both in the field and in laboratory experiments. For the two species, intersexual copulations were far more frequent than intrasexual ones. This can partly be explained by the difference in copulation time.Few interspecific copulating pairs were found on the shore. This may reflect a low interspecific encounter rate rather than a mechanism of species recognition. On all of these occasions, however, the active male was of L. saxatilis. It is argued that selection against precopulatory species and sex recognition is a more likely explanation than an hypothesis that states that the required mutations for precopulatory mate identification has not yet occurred. L. littorea males copulated longer with large than with small females. Copulation time was short with parasitized females, which are sterile or of low fecundity. The allocation of mating effort by males is discussed.  相似文献   
42.

Post-traumatic stress disorder (PTSD) is a psychiatric condition resulting from exposure to a traumatic event. It is characterized by several debilitating symptoms including re-experiencing the past trauma, avoidance behavior, increased fear, and hyperarousal. Key roles in the neuropathology of PTSD and its symptomatology have been attributed to the hippocampus and amygdala. These regions are involved in explicit memory processes and context encoding during fear conditioning. The aim of our study was to investigate whether PTSD is capable of altering the morphology, density and expression of glial fibrillary acidic protein (GFAP) in astrocytes from the CA1 region of the hippocampus and the medial amygdala and correlate the data obtained with the orientation index of the polarity of astrocytes. Thirty male rats were divided in two groups: control (n = 15) and PTSD (n = 15). The inescapable shock protocol, in which the animals are exposed to a single episode of footshock, was used to induce PTSD. Our results show that, in the hippocampus, PTSD is capable of decreasing the density of GFAP+ astrocytes as well as altering astrocytic morphology, as shown by the reductions observed in the total number of primary processes, in the number of primary processes in the lateral quadrants, and the degree of branching in the lateral quadrants. The analysis of the orientation index indicates that PTSD alters the polarity of hippocampal astrocytes. No alterations were observed in the amygdala astrocytes. Therefore, this study demonstrates notable changes in hippocampal astrocytes, supporting the concept that these cells play an important role in PTSD symptomatology.

  相似文献   
43.

Purpose

The article aims to test indicators for assessing the environmental and social impacts of biorefineries. Testing environmental and social impact categories and indicators, and selecting the most suitable ones, will simultaneously contribute to the further development of social life cycle assessment (S-LCA) methodologies while assessing several dimensions of sustainability at biorefineries.

Methods

The work applies two methodologies, environmental LCA (E-LCA) and social LCA (S-LCA), to two hypothetical production processes of second-generation bioethanol and biochemical in two alternative locations (Norway and the USA). Five impact categories were chosen for the E-LCA. The S-LCA was performed in two stages: a generic assessment (top-down approach) using the social hotspot database (SHDB 2013) to screen for potential social issues in the stakeholder group Worker in Norway and the USA and a specific assessment (bottom-up approach) for collecting data and confirming or refuting the SHDB results in the Norwegian case only.

Results and discussion

Bioethanol produced in the Norwegian biorefinery would perform relatively well in relation to climate change targets, with emissions of approximately 11 g CO2-eq/MJ. The same production process located in the USA would produce emissions of approximately 29 g CO2-eq/MJ. Other biorefinery products are difficult to compare because of a lack of clear alternatives. Bioethanol and biochemicals produced in the hypothetical USA production process have higher burdens than those from the Norwegian production process in all environmental categories assessed. For both production processes, the main social risks were in the category Health and safety followed by Labor rights and decent work. More detailed investigations in an existing Norwegian biorefinery value chain confirmed some of the risk issues but discarded others, demonstrating the necessity of providing specific data and results for the social dimension.

Conclusions

E-LCA and S-LCA make it possible to highlight the main environmental and social challenges when producing biochemicals. The SHDB has potential as a social screening tool although social indicators are not yet well established. Hence, specific assessment is necessary for validating the results in the social dimension. S-LCA is still in its infancy and needs to be applied in order to develop the best practice. The two methodologies addressed bioethanol and biochemical production performance in two different dimensions (environmental and social), and their combination makes it possible to achieve results that integrate the product-oriented approach with the more location-specific approach.
  相似文献   
44.
45.
W Nellen  C Silan  U Saur    R A Firtel 《The EMBO journal》1986,5(12):3367-3372
  相似文献   
46.
Mast cells are implicated in the pathogenesis of inflammatory and autoimmune diseases. However, this notion based on studies in mast cell-deficient mice is controversial. We therefore established an in vivo model for hyperactive mast cells by specifically ablating the NF-κB negative feedback regulator A20. While A20 deficiency did not affect mast cell degranulation, it resulted in amplified pro-inflammatory responses downstream of IgE/FcεRI, TLRs, IL-1R, and IL-33R. As a consequence house dust mite- and IL-33-driven lung inflammation, late phase cutaneous anaphylaxis, and collagen-induced arthritis were aggravated, in contrast to experimental autoimmune encephalomyelitis and immediate anaphylaxis. Our results provide in vivo evidence that hyperactive mast cells can exacerbate inflammatory disorders and define diseases that might benefit from therapeutic intervention with mast cell function.  相似文献   
47.
48.
Inhibition of platelet adenylate cyclase by epinephrine requires GTP   总被引:8,自引:0,他引:8  
K H Jakobs  W Saur  G Schultz 《FEBS letters》1978,85(1):167-170
  相似文献   
49.
50.

Introduction  

Stressful events are thought to contribute to the aetiology, maintenance and exacerbation of rheumatic diseases. Given the growing interest in acute stress responses and disease, this review investigates the impact of real-life experimental psychosocial, cognitive, exercise and sensory stressors on autonomic, neuroendocrine and immune function in patients with inflammatory rheumatic diseases.  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