全文获取类型
收费全文 | 159篇 |
免费 | 4篇 |
国内免费 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2015年 | 8篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 5篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1991年 | 1篇 |
1990年 | 6篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有164条查询结果,搜索用时 15 毫秒
1.
Origin of bombesin-like peptides in human fetal lung 总被引:2,自引:0,他引:2
Four different forms of bombesin-like immunoreactive peaks were detected in extracts of human fetal lung by the use of reversed-phase high performance liquid chromatography (HPLC). Peaks I, II, III and IV, (increasing retention time), were eluted using a 14-38% of acetonitrile gradient containing 0.1% trifluoroacetic acid (TFA). Peak II was the major material found in the extract of human fetal lung obtained at 16-20 weeks gestation. None of the four compounds contained in the eluted peaks had the same retention time as amphibian bombesin or porcine gastrin releasing peptide (GRP). On reversed-phase HPLC using two different solvent systems TFA or heptafluorobutyric acid (HFBA) as a hydrophobic counter ion, and in gel filtration chromatography, the chromatographic behavior of the main peak (peak II) was the same as that of the carboxyl terminal fragments of GRP, GRP18-27 or GRP19-27. This suggested that the peptide(s) in peak II resembled in composition the carboxy terminal 9 or 10 amino acids of porcine GRP. Following tryptic digestion the material in peak IV was converted to the more polar compound present in peak II. Two other peptide peaks were eluted close to peak II and these were presumed to be a modification of this main peak. One of the possible biosynthetic steps in the formation of bombesin-like peptides in human fetal lung could be a tryptic conversion of a less polar peptide to a more polar form (peak IV to II). 相似文献
2.
This study compared Pundamilia nyererei and Pundamilia pundamilia males in routine metabolic rate (RR) and in the metabolic costs males pay during territorial interactions (active metabolic rate, RA). Pundamilia nyererei and P. pundamilia males housed in social isolation did not differ in RR. In contrast to expectation, however, P. nyererei males used less oxygen than P. pundamilia males, for a given mass and level of agonistic activity. This increased metabolic efficiency may be an adaptation to limit the metabolic cost that P. nyererei males pay for their higher rate of aggressiveness compared to P. pundamilia males. Thus, the divergence between the species in agonistic behaviour is correlated with metabolic differentiation. Such concerted divergence in physiology and behaviour might be widespread in the dramatically diverse cichlid radiations in East African lakes and may be an important factor in the remarkably rapid speciation of these fishes. The results did not support the hypothesis that higher metabolic rates caused a physiological cost to P. nyererei males that would offset their dominance advantage. 相似文献
3.
J. M. C. K Jayawardana Martin Westbrooke Michael Wilson Cameron Hurst 《Hydrobiologia》2006,568(1):169-185
Reed invasion is a common phenomenon of open streams with disturbed riparian vegetation in river catchments. Knowledge of
the effects of such vegetation change on aquatic communities is fundamental to river management. Macroinvertebrate fauna in
Phragmites australis (Cav.) Trin. ex Steud. and open bank habitats were examined in three rivers in central Victoria in order to understand the
effect of such littoral habitat on macroinvertebrates. Data were analysed using Partially Nested Factorial ANOVA with season,
river and habitats as main effects. Habitat structure had a significant effect (p<0.05) on macroinvertebrate species richness, however this was not seasonally consistent across the three rivers. There was
a significant increase (p<0.05) in macroinvertebrate taxa richness in Phragmites habitats during winter and spring seasons. Total abundance of taxa showed no consistent significant differences in the two
habitats. Results of Canonical Analysis of Principle Coordinates indicated significant differences (p<0.05) in macroinvertebrate assemblages between Phragmites and bare bank habitats in all seasons. Habitat selection by taxa could be related to the microphysical environment of the
habitats. This study suggests that reed beds create important littoral habitat structures which support diverse macroinvertebrate
assemblages. 相似文献
4.
Maan Martine E.; van der Spoel Michael; Jimenez Paloma Quesada; van Alphen Jacques J.M.; Seehausen Ole 《Behavioral ecology》2006,17(5):691-699
Sexual selection by female choice has contributed to the rapidevolution of phenotypic diversity in the cichlid fish speciesflocks of East Africa. Yet, very little is known about the ecologicalmechanisms that drive the evolution of female mating preferences.We studied fitness correlates of male nuptial coloration ina member of a diverse Lake Victoria cichlid lineage, Pundamilianyererei. In this species, male red coloration is subject tointraspecific sexual selection by female mate choice. Male nuptialcoloration plays a critical role also in reproductive isolationbetween this species and the closely related sympatric speciesP. pundamilia. Here, we show that P. nyererei male colorationis carotenoid based, illustrating the potential for honest signalingof individual quality. In a wild population, we found that variationin male coloration was not associated with variation in a setof strongly intercorrelated indicators of male dominance: malesize, territory size, and territory location. Instead, the 2male characters that predominantly determine female choice,territory size and red coloration, may be independent predictorsof male quality: males with bright red coloration and largeterritories had lower parasite infestation rates. As a result,female preferences tended to select against heavily parasitizedmales. Consistent with parasite-mediated sexual selection, maleshad higher and more variable parasite loads than females. 相似文献
5.
Elizabeth A. Nyboer Lauren J. Chapman 《Biological journal of the Linnean Society. Linnean Society of London》2013,110(2):449-465
Habitat‐associated trait divergence may vary across ontogeny if there are strong size‐related shifts in selection pressures. We quantified patterns of phenotypic divergence in Nile perch (Lates niloticus) from ecologically distinct wetland edge and forest edge habitats in Lake Nabugabo, Uganda, and we compared patterns of divergence across three size classes to determine whether trends are consistent through Nile perch ontogeny. We predicted that inter‐habitat variation in biotic (e.g. vegetation structure) and abiotic (e.g. dissolved oxygen concentration) variables may create divergent selective regimes. We compared body morphology using geometric morphometrics and found substantial differences between habitats, although not all trends were consistent across size classes. The most striking aspects of divergence in small Nile perch were in mouth orientation, head size, and development of the caudal region. Medium‐sized Nile perch also showed differences in mouth orientation. Differences in large individuals were related to eye size and orientation, as well as caudal length. The observed patterns of divergence are consistent with functional morphological predictions for fish across divergent trophic regimes, high and low predation environments, and complex and simple habitats. Although this suggests adaptive divergence, the source of phenotypic variation is unknown and may reflect phenotypic plasticity and/or genetic differences. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 449–465. 相似文献
6.
C. J. Cooksey 《Biotechnic & histochemistry》2013,88(7):527-532
ABSTRACTThe identities of 18 dyes whose names begin with “Victoria” are described using their chemical structures, names and numerical identifiers. All are synthetic dyes originally synthesized in Germany during the late 19th century as colorants for textiles. Brief manufacturing details are included. All the colors of the rainbow are represented except indigo. Unusual properties including explosive tendency or toxicity are noted. Some of the applications as stains and for food coloring, anti-obesity medication and pigments for ball pen inks also are discussed 相似文献
7.
Wang Nguitragool Stephan Karl Michael White Cristian Koepfli Ingrid Felger Pratap Singhasivanon Ivo Mueller Jetsumon Sattabongkot 《International journal for parasitology》2019,49(6):455-462
Over the past decades, the malaria burden in Thailand has substantially declined. Most infections now originate from the national border regions. In these areas, the prevalence of asymptomatic infections is still substantial and poses a challenge for the national malaria elimination program. To determine epidemiological parameters as well as risk factors for malaria infection in western Thailand, we carried out a cohort study in Kanchanaburi and Ratchaburi provinces on the Thailand-Myanmar border. Blood samples from 999 local participants were examined for malaria infection every 4 weeks between May 2013 and Jun 2014. Prevalence of Plasmodium falciparum and Plasmodium vivax was determined by quantitative PCR (qPCR) and showed a seasonal variation with values fluctuating from 1.7% to 4.2% for P. vivax and 0% to 1.3% for P. falciparum. Ninety percent of infections were asymptomatic. The annual molecular force of blood-stage infection (molFOB) was estimated by microsatellite genotyping to be 0.24 new infections per person-year for P. vivax and 0.02 new infections per person-year for P. falciparum. The distribution of infections was heterogenous, that is, the vast majority of infections (>80%) were found in a small number of individuals (<8% of the study population) who tested positive at multiple timepoints. Significant risk factors were detected for P. vivax infections, including previous clinical malaria, occupation in agriculture and travel to Myanmar. In contrast, indoor residual spraying was associated with a protection from infection. These findings provide a recent landscape of malaria epidemiology and emphasize the importance of novel strategies to target asymptomatic and imported infections. 相似文献
8.
Stream restoration has become a multibillion dollar industry worldwide, yet there are few clear success stories and the scientific basis for effective stream restoration remains uncertain. We compiled data on completed river restoration projects from four management authorities in Victoria, Australia, to examine how the available data could inform the science of restoration ecology in rivers, and thus improve future restoration efforts. We found that existing data sources are limited and much historical information has been lost through industry restructuring and poor data archiving. Examining records for 2,247 restoration projects, we found that riparian management projects were the most common, followed by bank stabilization and in‐stream habitat improvement. Only 14% of the project records indicated that some form of monitoring was carried out. It is evident that overall there is little scientific guidance and little or no monitoring and evaluation of the projects for which we had information. However, recent advances with mandatory, statewide reporting and an increased emphasis on project design and monitoring strongly suggest that the design, implementation, monitoring, and reporting of stream restoration projects have improved in recent years and will continue to do so. 相似文献
9.
10.