全文获取类型
收费全文 | 628篇 |
免费 | 88篇 |
国内免费 | 7篇 |
出版年
2024年 | 4篇 |
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 21篇 |
2019年 | 27篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 39篇 |
2015年 | 40篇 |
2014年 | 45篇 |
2013年 | 70篇 |
2012年 | 32篇 |
2011年 | 25篇 |
2010年 | 20篇 |
2009年 | 32篇 |
2008年 | 18篇 |
2007年 | 35篇 |
2006年 | 31篇 |
2005年 | 24篇 |
2004年 | 31篇 |
2003年 | 16篇 |
2002年 | 11篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有723条查询结果,搜索用时 100 毫秒
1.
Richard G. Condon 《Human ecology: an interdisciplinary journal》1991,19(3):287-321
Birth seasonally at high latitudes is a complex phenomenon which is undoubtedly affected by a subtle interaction between environmental rhythmicity (most notably in photoperiod and temperature) and cultural adaption. There is intriguing evidence that human gonadotrophic activity (and hence fertility) may be affected by seasonal fluctuations in light intensity and duration. Nevertheless, cultural factors are important insofar as they mediate between environmental rhythmicity and human fertility/birth patterns. This article examines the distribution of births over several decades in an Inuit community located 300 miles north of the Arctic Circle. Several shifts in birth seasonality are noted, the most significant of which is a dramatic shift from pronounced seasonality in the 1970s to non-seasonality in the 1980s. Longitudinal ethnographic fieldwork has allowed an examination of social and economic changes accounting for the rather sudden disappearance of birth seasonality. These include increasing reliance upon wage employment and social assistance, decreased dependence upon subsistence hunting and trapping, changing attitudes on the part of young people entering their prime reproductive years, and the introduction of television, radio, and southern-style recreational activities. 相似文献
2.
Ramon J. Rhine Guy W. Norton Gail M. Wynn Roger D. Wynn 《International journal of primatology》1989,10(4):319-342
Focal-animal feeding data obtained from 64 adult baboons during a 3-year period were used together with equivalent data from
46 infants to evaluate hypotheses predicting selection for a birth peak and to study the baboon’s eclectic/selective feeding
adaptation, with emphasis on differential feeding by sex, developmental trends, and seasonal use of food classes (fruit, leaf,
flower, grass, etc.). The findings suggest that feeding conditions are better in the wet season than in the dry season. Despite
large sexual dimorphism, estimates of total amounts eaten were virtually identical for males and females. Infants used all
of the same plant-food classes as adults, but proportional differences occurred for some food classes in amounts eaten. Foods
eaten proportionately less by infants were probably harder for them to obtain and process or were chosen through inexperience
or for exploration. There was considerable between-year variation in amounts of food classes eaten, but the within-year standard
deviations were similar, as were also the mean amounts eaten per year. An eclectic/selective feeding adaptation has the advantage
of permitting long-run acquisition of adequate nutrition within a context of high feeding variation from season to season
and year to year. Mixed results were obtained from hypotheses about selection for a birth peak. Although a peak occurred in
the early dry season, this was not the optimal time of birth for survival. Survival was highest for individuals born in the
late wet season, when the availability and probably the quality of food for lactating mothers were greatest. 相似文献
3.
J. A. Horrocks 《International journal of primatology》1986,7(1):31-47
Life history data are presented for a population of vervets, Cercopithecusaethiops sabaeus, in Barbados, West Indies. The data were obtained from two habituated troops and from vervets captured during
a large-scale trapping program. Individuals of known age from one troop were weighed periodically, and separate growth curves
generated for males and females. The mean weight of captured adult females was 3.3 kg; that of adult males, 5.3 kg. The average
age at sexual maturity is estimated at 34 months for females and 60 months for males. Vervets give birth throughout the year,
but most infants are born between April and July. The average interbirth interval following a surviving infant is 11.8 months.
The mortality of juveniles is heaviest between birth and 2 years of age and decreases thereafter. Males emigrate from their
natal troops at sexual maturity and one incident of a juvenile female emigrating is reported. 相似文献
4.
Lisa Gould 《International journal of primatology》1996,17(3):331-347
I examined the vigilance behavior of adult males and females in two groups of ring-tailed lemurs(Lemur catta)during the birth and lactation season at the Beza-Mahafaly Reserve, southwestern Madagascar. I found no sex difference with
respect to the rates of overall vigilance, rates of vigilance toward a potential predator or unfamiliar sound, or rates of
vigilance toward conspecifics from other social groups, nor were there sex differences in the percentage of time spent vigilant
in any of the above categories. Higher-ranking females were vigilant significantly more often toward predators or potential
predators than lower-ranking females were. I detected no relationship between vigilance behavior and dominance rank among
adult males. The alpha female in each group exhibited significantly more vigilance behavior than all other members of her
group. It was predicted that males should exhibit more vigilance behavior than females do, particularly during the birth and
lactation season, when predator pressure is high, if they are benefiting females in this respect. I discuss the results in
the context of this prediction and in terms of how ring-tailed lemur males benefit females, and why they may be tolerated
in social groups. 相似文献
5.
Alexandra M. Birrell Annemarie Hennessy Adrian Gillin John Horvath David Tiller 《Journal of medical primatology》1996,25(4):287-293
Abstract: Baboons are widely used in biomedical research. Although it is widely held that Papio hamadryas breed well in captivity, each established colony has a different reproductive success often hypothesised to be due to husbandry practices. The National Baboon Colony in Australia is a unique colony that houses Papio hamadryas to mimic that structure seen in the wild. In this article; we have analysed their reproductive parameters and neonatal outcomes. The success of the colony husbandry practices was demonstrated by lack of maternal mortality, low foetal morbidity, and known maternal and paternal linage. 相似文献
6.
Joan Silk Jenny Short Jeffrey Roberts Jill Kusnitz 《International journal of primatology》1993,14(1):95-104
We describe some of the sources of variation in gestation length among rhesus macaques. the data were obtained from the timed-mating breeding program at the California Regional Primate Research Center (CRPRC). Information about approximately 700 pregnancies that resulted in spontaneous vaginal deliveries of liveborn young is presented. The average length of these pregnancies was 166.5 days. In this population, older females with higher parities had significantly longer pregnancies and significantly heavier infants than other females did. Other factors, including infant sex, month of conception, maternal reproductive history, and paternal identity, had no consistent effect upon gestation length. 相似文献
7.
8.
Photographic and visual aerial surveys to determine current pup production of Northwest Atlantic harp seals were conducted off Newfoundland and in the Gulf of St. Lawrence during March 1999-Photographic surveys were conducted on all whelping concentrations between 14 and 24 March, whereas a visual survey was made of the southern Gulf concentrations on 14 March. Pup production was estimated to be 739,100 (SE = 96,300, CV = 13.0%) at the Front, 82,600 (SE = 22,500, CV = 27.2%) in the northern Gulf, and 176,200 (SE = 25,400, CV = 14.4%) in the southern Gulf (Magdalen Island) for a total of 997,900 (SE = 102,100, 10.2%). Changes in aerial survey estimates indicate that pup production has increased since 1994. A new method to correct for the temporal change in the proportion of pups present on the ice was examined by fitting the percentage of pups observed in three age-dependent stages to a Normal distribution. The results were compared to those obtained from a more complex model used previously. The Simple model produced slightly higher, and hence more conservative, estimates of the proportion of births that had occurred before the time of the survey than the Complex model. When using the Simple model fewer assumptions regarding the start date of pupping and the proportion of older pups remaining on the ice were required, the herd had to be followed for a shorter period, and a more convenient means of calculating confidence limits was available. 相似文献
9.
G. J. Burton 《International journal of primatology》1984,5(2):183-195
The testicular histology of the dusky leaf monkey, Presbytis obscura,is described following a study of material from 16 adult males collected over a 13-month period in Peninsular Malaysia. The
histological appearances were similar to those of the other cercopithecines studied so far. No seasonal variation in the height
of the seminiferous epithelium was observed, and spermatogenesis was seen in all the adult testes. These findings suggest
that males of this species are capable of breeding throughout the year. These results are discussed in relation to field observations
of births of this species and to the birth patterns exhibited by other species of langur. 相似文献
10.
A probability model for the number of complete conceptions (that is, live births) taking into account foetal wastages, occurring
in a couple during a specified period of time (T0, T0+T) is developed assuming that the data was collected starting a long time after marriage. A method of estimating some of
the underlying parameters is given. The model is applied to data obtained in a Varanasi Survey in 1969–70. 相似文献