全文获取类型
收费全文 | 111篇 |
免费 | 8篇 |
专业分类
119篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1992年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1966年 | 1篇 |
1931年 | 1篇 |
1930年 | 2篇 |
排序方式: 共有119条查询结果,搜索用时 0 毫秒
1.
A conditional developmental mutant of Mucor racemosus which is capable of oxidative energy metabolism is described. Unlike the wild-type strain the mutant was highly fermentative and exhibited the yeast morphology when grown aerobically in glucose-containing media. The high fermentative activity and yeast morphology under these conditions correlated well with maximal expression of glycolytic enzymes and with expression of some polypeptides characteristic of anaerobic growth. Aerobic growth of the mutant on amino acids as the sole carbon source resulted in growth in the mycelial morphology. The mutant was fully capable of oxidative metabolism as judged by its ability to grow on amino acids, respiratory capacity, and complement of tricarboxylic acid cycle enzymes. The results support the hypothesis that oxygen controls both the expression of glycolytic enzymes and the expression of proteins involved in morphogenesis. Moreover, they suggest that there are common regulatory elements in the control of these two classes of gene products. Abnormally high levels of aconitase and isocitrate dehydrogenase in the mutant are consistent with the proposal that pool sizes of citrate may act as a regulator of genes responsive to environmental oxygen concentration. 相似文献
2.
In the present study the whole sample of 772 desert gerbils was collected from the semi-arid areas in and around Jaipur (Rajasthan, India). The male exhibits active spermatogenesis and well maintained accessory reproductive organs at any time of the year. Reproductive organs of the male gerbil are briefly described. The vaginal and urinary openings are independent in the gerbil. There are four pairs of mammae. Follicular development takes place cyclically. Maximum atresia of follicles is noticed during metoestrus. A well developed Graafian follicle measures 590 μ across its widest diameter. The average diameter of the ovum is 65 μ. At the time of ovulation formation of stigma occurs which gives way to the ovum. The corpus luteum is formed from the remaining granulosa cells of the ovulated follicle. Fully formed corpus luteum of the cycle (during dioestrus) measures 740 μ. Maximum development of the corpus luteum is seen during late pregnancy (22–25 days) when it measures 1250 μ. During pregnancy large Graafian follicles are absent. After parturition the ovary shows corpora lutea of lactation. Histological changes in the uterus and vagina during the oestrous cycle of the gerbil are described. There is less proestrus distension of the uterus as compared with the rat. During oestrus the uterine endometrium hypertrophies and there are some degenerative changes in the epithelial lining. The changes in the vaginal epithelium are clear cut and are correlated with the ovarian activity. During proestrus proliferation of the epithelium occurs and at ‘heat period’ or oestrus the epithelium shows formation of the stratum corneum and the shedding of cornified cells. In the dioestrus the vaginal epithelium is heavily infiltrated by leucocytes. There are three peaks in the incidence of pregnancy rate, i.e., February to April, July, and September to November. Pregnancy rate is lowest during summer (May and June) and winter (December and January). Average monthly litter size shows almost similar changes. The average length of gestation period is 30 days. There is post-partum heat in this animal. Formation of a vaginal plug is noticed following copulation. Litter size varies from 2–7. The average body weight of the new born young is 3.5 and 3.4 gm respectively for the male and the female. Weaning of the young is observed after about 20 days. Descent of the testes into the scrotal sacs occurs around day 28. Vagina opens after about 75 days. 相似文献
3.
4.
5.
Lipid profile of the spinal cord myelin was studied in normal and vitamin B12 deficient chicks. The significant findings were a reduction in the total galactolipids and an increase in the total phospholipids of myelin in vitamin B12 deficiency. The altered molar ratios of these lipids suggest a relative immaturity of the myelin in this condition. These changes may initiate the degenerative changes in the central nervous system in vitamin B12 deficiency.Vitamin B12 is essential for normal functioning of both the hemopoietic and the nervous system. Sub-acute combined degeneration of the spinal cord is seen both in association with pernicious anemia and in megaloblastic anemia of dietary origin (1,2). Though many biochemical postulates (3, 4) have been advanced to explain the neurological changes, the role of vitamin B12 in maintaining the integrity of myelin is still obscure. So far only in two animal species the monkey (5) and the chick (6) has myelin degeneration been reported in vitamin B12 deficiency. However, in neither of these reports, have changes in the composition of myelin been described. The results of a study in chicks wherein the effects of vitamin B12 on the lipid profile of myelin were investigated are reported here. 相似文献
6.
Food action plans in many global cities articulate interest in multiple objectives including reducing in‐ and trans‐boundary environmental impacts (water, land, greenhouse gas (GHG)). However, there exist few standardized analytical tools to compare food system characteristics and actions across cities and countries to assess trade‐offs between multiple objectives (i.e., health, equity) with environmental outcomes. This paper demonstrates a streamlined model applied for analysis of four cities with varying characteristics across the United States and India, to quantify system‐wide water, energy/GHG, and land impacts associated with multiple food system actions to address health, equity, and environment. Baseline diet analysis finds key differences between countries in terms of meat consumption (Delhi 4; Pondicherry 16; United States 59, kg/capita/year), and environmental impact of processing of the average diet (21%, 19%, <1%, <1% of community‐wide GHG‐emissions for New York, Minneapolis, Delhi, and Pondicherry). Analysis of supply chains finds city average distance (food‐miles) varies (Delhi 420; Pondicherry 200; United States average 1,640 km/t‐food) and the sensitivity of GHG emissions of food demand to spatial variability of energy intensity of irrigation is greater in Indian than US cities. Analysis also finds greater pre‐consumer waste in India versus larger post‐consumer accumulations in the United States. Despite these differences in food system characteristics, food waste management and diet change consistently emerge as key strategies. Among diet scenarios, all vegetarian diets are not found equal in terms of environmental benefit, with the US Government's recommended vegetarian diet resulting in less benefit than other more focused targeted diet changes. 相似文献
7.
Rodrigues Vereena Kumar Amit Gokul Sivaraman Verma Ram S. Rahman Laiq ur Sundaresan Velusamy 《In vitro cellular & developmental biology. Plant》2020,56(4):526-537
In Vitro Cellular & Developmental Biology - Plant - An efficient in vitro propagation and synthetic seed production protocol was established for the conservation of Decalepis salicifolia (Bedd.... 相似文献
8.
Native species’ response to the presence of invasive species is context specific. This response cannot be studied in isolation from the prevailing environmental stresses in invaded habitats such as seasonal drought. We investigated the combined effects of an invasive shrub Lantana camara L. (lantana), seasonal rainfall and species’ microsite preferences on the growth and survival of 1,105 naturally established seedlings of native trees and shrubs in a seasonally dry tropical forest. Individuals were followed from April 2008 to February 2010, and growth and survival measured in relation to lantana density, seasonality of rainfall and species characteristics in a 50-ha permanent forest plot located in Mudumalai, southern India. We used a mixed effects modelling approach to examine seedling growth and generalized linear models to examine seedling survival. The overall relative height growth rate of established seedlings was found to be very low irrespective of the presence or absence of dense lantana. 22-month growth rate of dry forest species was lower under dense lantana while moist forest species were not affected by the presence of lantana thickets. 4-month growth rates of all species increased with increasing inter-census rainfall. Community results may be influenced by responses of the most abundant species, Catunaregam spinosa, whose growth rates were always lower under dense lantana. Overall seedling survival was high, increased with increasing rainfall and was higher for species with dry forest preference than for species with moist forest preference. The high survival rates of naturally established seedlings combined with their basal sprouting ability in this forest could enable the persistence of woody species in the face of invasive species. 相似文献
9.
10.