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   244篇
  免费   4篇
  国内免费   7篇
  2023年   3篇
  2022年   4篇
  2021年   3篇
  2019年   2篇
  2018年   1篇
  2017年   5篇
  2016年   5篇
  2015年   1篇
  2014年   8篇
  2013年   7篇
  2012年   8篇
  2011年   5篇
  2010年   9篇
  2009年   19篇
  2008年   16篇
  2007年   8篇
  2006年   8篇
  2005年   8篇
  2004年   3篇
  2003年   6篇
  2002年   4篇
  2001年   3篇
  2000年   1篇
  1999年   5篇
  1998年   1篇
  1997年   1篇
  1996年   9篇
  1995年   10篇
  1994年   9篇
  1993年   10篇
  1992年   8篇
  1991年   6篇
  1990年   7篇
  1989年   7篇
  1988年   13篇
  1987年   2篇
  1986年   4篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
  1980年   4篇
  1979年   4篇
  1978年   2篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
排序方式: 共有255条查询结果,搜索用时 125 毫秒
101.
Domestic dogs (Canis familiaris) have been submitted to a vast process of artificial selection and to date, there are hundreds of breeds that differ in their physical and behavioral features. In addition, dogs possess important skills to communicate with humans. Previous evidence indicates that those abilities are related to the domestication process and are modulated by instrumental learning processes. Very few studies, however, have evaluated breed differences in the use and learning of interspecific communicative responses. In Study 1 Retrievers, German Shepherds and Poodles were compared in the acquisition and extinction of their gaze toward the human face, in a conflict situation involving food within sight but out of reach. The groups did not differ in the acquisition of the response, but throughout the extinction phase Retrievers gazed to the human significantly more than the other groups. In Study 2, similar results were obtained in a test without any previous explicit training. These results suggest that these three major popular breeds differ in gazing to humans in a communicative situation.  相似文献   
102.
The paper presents results of the charcoal analysis from the lakeshore settlement of Chalain 4 in the French Jura (Dép. Franche-Comté), dated by dendrochronology from 3040 to 3000 bc. The investigated material comes from waterlogged organic layers (excluding fire events) where charcoals are assumed to be the residues of domestic fires only. The anthracological (charcoal) analysis reveals a complex domestic firewood management in balance with the social organisation and the technical and economic systems of the settlement. This firewood economy is characterised by the avoidance of wood species intended for other activities, such as building or foddering, and by the preferential use of wood less than 10 cm in diameter. The areas from which firewood was obtained are also connected to woodland clearance for cultivated land, which suggests that firewood was gathered along the paths, which were travelled daily.  相似文献   
103.
Abstract: Imprinting in chicks is a form of juvenile learning that has been used to study the basic cellular mechanisms of learning and memory. The forebrain area mediorostral neostriatum/hyperstriatum ventrale (MNH) is a center for acoustic imprinting. Electrophysiological and pharmacological behavioral studies in the MNH have demonstrated that the glutamatergic system and the associated receptors are critically involved in auditory filial imprinting. Accordingly, we investigated the hypothesis that stimulus-evoked glutamate release may be altered after this learning process. Using an in vivo microdialysis technique, we observed a significantly higher increase of extracellular glutamate level in tone-imprinted chicks during exposure to the previously imprinted tone than in socially imprinted control chicks. In a further series of experiments, where we exposed animals from both experimental groups to handling distress, glutamate levels in MNH showed only a slight increase, whereas we observed a pronounced increase of extracellular glutamate in the lobus parolfactorius (LPO), the avian analogue of the basal ganglia. No difference of distress-evoked glutamate release was found in MNH and LPO between tone-imprinted and socially imprinted chicks. The tone-evoked enhanced glutamate response in tone-imprinted chicks suggests that during auditory imprinting glutamatergic synapses develop the potential to increase transmitter release in response to the imprinting stimulus.  相似文献   
104.
105.
为了解家兔(Oryctolagus curiculus)黄艾美耳球虫(Eimeria flavescens)的内生发育史,用不同接种剂量感染20只无球虫兔,采用常规石蜡切片技术进行研究。共观察到4代裂殖生殖和1代配子生殖。每一代裂殖生殖阶段都含有2种类型的裂殖体:粗型和细型。第1代裂殖生殖发生于感染后60~72h,主要位于空肠的腺上皮;第2代裂殖生殖发生于感染后84h,位于盲肠和结肠的腺上皮;第3代裂殖生殖发生于感染后96~120h,位于盲肠和结肠的绒毛上皮;第4代裂殖生殖发生于感染后144~153h,位于结肠和盲肠的腺上皮。感染后167h,开始配子生殖阶段,成熟卵囊出现于感染后215h。本研究中对于裂殖生殖代数划分与文献报道不同,并观察到2种形态的裂殖体。  相似文献   
106.
107.
Domestic cats exhibit physiological proteinuria due to the excretion of cauxin, a carboxylesterase, into the urine. In the present report, we demonstrate that cauxin is excreted in a species-, sex-, and age-dependent manner. Although the cauxin gene is conserved in mammals, including human, mouse, and dog, urinary cauxin was found only in member of the genus Felis and lynx (bobcat, and lynx) and not in other Felidae (genus: Panthera and puma) tested. In mature cats, cauxin excretion was higher in intact males than in castrated males or in intact or spayed females. Daily cauxin excretion decreased immediately after castration. Immunohistochemistry confirmed that cauxin expression in the kidney proximal straight tubules was higher in intact males than in castrated males. Urinary cauxin was detectable by Western blotting in cats older than about 3 months, and its excretion increased with age. In a zymographic esterase assay, urine contained a major cauxin band; by contrast, kidney homogenates contained three major bands, comprising two carboxylesterases and an unidentified esterase, and one minor cauxin band. These results suggest that 1. cauxin excretion is regulated by sex hormones, such as testosterone, 2. cauxin functions as an esterase in the urine rather than in kidney cells, and 3. the decomposition products by cauxin are excreted in a species-, sex-, and age-dependent manner, as is cauxin itself.  相似文献   
108.
Summary In Morocco, shellfish sanitary quality analysis does not currently include enteric virus detection. Enteroviruses are classically detected by cell culture, but molecular methods such as RT-PCR are now broadly used alone or associated to cell culture. RT-PCR has the advantage of requiring less time and budget than cell culture. Bivalve mussels, being filter-feeders tend to accumulate viruses in contaminated seawater. In order to assess mussel contamination by enteroviruses, we screened samples of two origins, an aquaculture system and an area where wild mussels grow. Domestic sewage samples from an outlet near the above wild mussels growing area were also analysed. Viruses were concentrated from mussel meat by direct glycine elution and PEG 8000 precipitation. Total RNA was then extracted from the PEG precipitate by the guanidine thiocyanate method and used in RT-PCR. Enterovirus genomes were detected in 10% of wild shellfish samples, whilst none was present in the aquaculture samples. Since organisms harvested in both growing areas are used for human consumption, the enterovirus contamination observed in this study may highlight a potential public health risk and illustrate the importance of including routine virological analysis of shellfish in Morocco.  相似文献   
109.
Saida Hodžić 《Ethnos》2013,78(3):331-360
This article provides a new lens for analyzing power formations in human rights practices by examining Ghanaian struggles over a Domestic Violence Bill. While the hegemonic character of human rights advocacy is well-established, we know less about exercises of power in discourses and practices that oppose rights. I analyze how the Ghanaian government constructed the discourse of cultural sovereignty and deployed it against women's rights. The government legitimated this discourse by appropriating the voice of ‘the people’ and superimposing notions of ‘foreignness’ onto both the Bill and Ghanaian women's rights activists. Drawing on the historiography of colonialism and ethnography of political performance, I argue that this case illustrates how the discourse of cultural sovereignty is mobilized in a struggle over shifting configurations of gender, political activism, and state sovereignty.  相似文献   
110.
On a global scale, cereal grains and animal feed may be contaminated with trichothecenes, such as deoxynivalenol and T-2 toxin, zearalenone (ZEA), and fumonisins, the major mycotoxins of Fusarium fungi. Of these mycotoxins, ZEA is unequivocally implicated in reproductive disorders of swine and other domestic animals. Experiments in vivo and in vitro indicate that ZEA and its metabolites exert estrogenic effects resulting in functional and morphological alterations in reproductive organs. Recently, the potential of trichothecenes and fumonisins to cause reproductive disorders in domestic animals has been investigated. The present review summarizes the toxicological data on the effects of Fusarium mycotoxins on ovarian function, testicular function, placenta and fetus, and puberty/sexual maturity of domestic animals. The results of in vivo animal studies and in vitro tests are reported and discussed.  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