全文获取类型
收费全文 | 255篇 |
免费 | 11篇 |
专业分类
266篇 |
出版年
2021年 | 4篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 7篇 |
1968年 | 6篇 |
1957年 | 1篇 |
排序方式: 共有266条查询结果,搜索用时 15 毫秒
61.
During 2 years spent conducting ecological fieldwork on Siberut, the largest and most northerly of the four Mentawai Islands in Indonesia, incidental observations were made of the Mentawai macaque. The Mentawai macaque has been considered variously as a full species similar in some respects to the long-tailed macaque and as a subspecies of the pig-tailed macaque. Evidence is presented that a hitherto undescribed form of the Mentawai macaque occurs on Siberut, and aspects of its ecology and behavior are described. 相似文献
62.
63.
64.
65.
66.
67.
The respiratory burst is an NADPH oxidase-driven reduction of molecular oxygen to superoxide, which can occur in phagocytic cells as part of an antimicrobial defence, and is well documented among the vertebrates. This paper describes a process resembling the respiratory burst, which occurs in the haemolymph and haemocytes of the cockroach, Blaberus discoidalis. The in vitro reduction of nitroblue tetrazolium by superoxide to formazan was measured spectrophotometrically in B. discoidalis haemolymph in response to various immune elicitors. Nitroblue tetrazolium reduction was partly impeded in the presence of superoxide dismutase, a specific antioxidant which converts superoxide to hydrogen peroxide, as well as by chemicals known to inhibit the respiratory burst in vertebrates (trifluoperazine, diphenylene iodonium, and N-ethylmaleimide). This suggests the generation of superoxide anions by haemolymph as part of an immune response. Furthermore, formazan staining of elicitor-treated haemocytes was observed microscopically, with less intense staining in the presence of superoxide dismutase. Finally, respiratory burst inhibitors and superoxide dismutase enhanced the growth of E. coli incubated in whole haemolymph, implying a role for haemolymph-derived superoxide in antibacterial defence. 相似文献
68.
Background and Aims Within Oncidiinae, there are severalgroups of species that are effectively annuals, and we wishedto see if these species had smaller genome sizes than averagefor the subtribe. Methods Fifty-four genome size estimates (50 of whichare new) for species in subtribe Oncidiinae (Orchidaceae) wereexamined for the first time in a phylogenetic context to evaluatehypotheses concerning genome sizes and life history traits. Results and Conclusions Within the limits of still relativelysparse sampling, the species that are effectively annuals doappear to have smaller genome sizes than average. However, thegenome sizes of their immediate sister group are also small,indicating that changes in genome size preceded the change inlife history traits. Genome sizes and chromosome numbers alsodo not correlate; some slowly growing species have lower chromosomenumbers but large genomes and vice versa. Based on a surveyof the literature on orchids, it is also clear that epiphyticspecies have smaller genome sizes than do terrestrial species,which could be an effect of different water relations or thefact that most terrestrial orchids are geophytic or have distinctgrowth and dormancy phases. 相似文献
69.
Ecological imagery among the Upper Amazonian Canelos Quichua native peoples of eastern Ecuador provides a paradigmatic, symbolic template organized by sets of cosmological premises. This template, anchored by traditional shamanism and ceramic manufacture, is invoked in emotionally charged ceremonial and juropolitical contexts to express resistance to normative culture bearers who have a potential or real impact on the ecosystem and indigenous political economy. The imagery is described as it exists within a system of radical change. Mechanisms are discussed whereby ecosystem knowledge and social structure are systemically linked to cosmological premises within a dynamic system of indigenous cultural adaptability . [Ecuador, symbolism of Canelos Quichua, Amazonian cosmology, cultural adaptability, ecological imagery] 相似文献
70.
Patricia L. Whitten Ronda Stavisky Filippo Aureli Elizabeth Russell 《American journal of primatology》1998,44(1):57-69
This study examined whether fecal cortisol could be used as an index of stress responses. The stress responsiveness of fecal cortisol was tested with a stressor known to stimulate adrenal activity, the stress of anesthesia. Daily fecal and urine samples were collected from four captive chimpanzees (Pan troglodytes) before and after anesthetizations with Telazol®/Ketasat®. Tests of assay validity indicated that cortisol was measurable in chimpanzee fecal extracts. Fecal cortisol concentrations were significantly elevated 2 days after anesthetization, with elevations in seven of the eight treatments. The posttreatment peak was significantly greater than baseline values in three of the four subjects. Both fecal concentrations and proportionate increases in response to stress were significantly correlated with the corresponding values in urinary cortisol, confirming the stressfulness of these procedures and the stress responsiveness of fecal cortisol. These findings provide evidence for the application of fecal cortisol as a noninvasive index of physiologic stress in nonhuman primates. Am. J. Primatol. 44:57–69, 1998. © 1998 Wiley-Liss, Inc. 相似文献