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   634篇
  免费   26篇
  国内免费   8篇
  2023年   4篇
  2022年   4篇
  2021年   11篇
  2020年   11篇
  2019年   11篇
  2018年   15篇
  2017年   12篇
  2016年   13篇
  2015年   11篇
  2014年   22篇
  2013年   16篇
  2012年   20篇
  2011年   14篇
  2010年   12篇
  2009年   30篇
  2008年   24篇
  2007年   23篇
  2006年   18篇
  2005年   21篇
  2004年   21篇
  2003年   16篇
  2002年   13篇
  2001年   24篇
  2000年   12篇
  1999年   10篇
  1998年   23篇
  1997年   17篇
  1996年   15篇
  1995年   13篇
  1994年   20篇
  1993年   17篇
  1992年   10篇
  1991年   14篇
  1990年   7篇
  1989年   17篇
  1988年   14篇
  1987年   17篇
  1986年   16篇
  1985年   14篇
  1984年   12篇
  1983年   11篇
  1982年   15篇
  1981年   10篇
  1980年   3篇
  1979年   4篇
  1978年   2篇
  1976年   2篇
  1975年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有668条查询结果,搜索用时 967 毫秒
661.
From 1975 through 1991, three sets of twins were born from a total of 693 live and stillborn births (0.43%) at the UCLA/Sepulveda Veterans Administration Medical Center Nonhuman Primate Research Laboratory, CA. None of the twin's mothers were related. Positive patrilineal relationships have not been established; however, a brother (not a twin) of the first set of twins may have fathered the third set. All twins were born to multiparous females and, in each case, only one infant survived beyond 4 days. One set of twins was dizygotic; the genetic status of the others is unknown. © 1994 Wiley-Liss, Inc.  相似文献   
662.
The objective of this investigation was to determine the effect of prolonged restriction of motor activity (hypokinesia [HK]) on several parameters of water metabolism in primates. The studies were performed on 12 rhesus monkeys aged 4–5 yr (5.10–6.85 kg) during the hypokinetic period of 90 d and during the prehypokinetic period of 30 d. They were divided into two equal groups: the first group was placed under ordinary vivarium conditions (vivarium control animals) and the second group was subjected to 90 d of HK (hypokinetic animals). For the simulation of the hypokinetic effect, the primates were immobilized on their abdomens in special tables. The legs of the monkeys were immobilized with hip and knee joints extended. The primates retained freedom of movement at elbow, wrist, and ankle. During the preexperimental period of 30 d and during the experimental period of 90 d, the following variables were determined: body weight, total body fluid content, specific total body fluid, mean fluid consumed and eliminated in urine, specific plasma resistance, hematocrit level, and plasma concentrations of sodium (Na) and potassium (K). In the hypokinetic primates, body weight decreased significantly when compared to the controls. Mean fluid intake, total body fluid, and specific total body fluid decreased, whereas mean daily fluid loss and specific mean daily fluid elimination increased significantly. Specific plasma resistance, hematocrit level, and plasma electrolyte concentrations increased significantly when compared to the control primates. It was concluded that prolonged restriction of motor activity induces significant changes in water metabolic parameters of primates leading in decreased total water content of the body.  相似文献   
663.
The proximal portion of a subfossil monkey femur found in a Jamaican cave shares all the femoral characters of a mature male Cebus apella.The fragment alone, however, does not prove conspecificity. The Jamaican femur is also of a size that could belong to the extinct Xenothrix mcgregoriof the same island. In contrast, the distal portion of a monkey tibia recovered from a kitchen midden in the Dominican Republic cannot be identified with that of any known living platyrrhine or catarrhine monkey. Geological age, geographic locality, and size of fragment point to probable alignment of the tibia with the recently extinct cebid Saimiri bernensis.Although no conclusive identifications are made, the distinctive characters of the two limb bones are described on the basis of comparisons with femurs and tibias representing all genera of living platyrrhines, most genera of catarrhine monkeys, and some strepsirhines.  相似文献   
664.
Unique structures often accompany unusual feeding behaviors in erebid moths. We test whether self-medicating (e.g., pharmacophagous) adult tiger moths have specialized structures on their mouthparts. We examined mouthparts of pharmacophagous and non-pharmacophagous adults using scanning electron microscopy (SEM). Self-medicating adults had significantly higher numbers of chemosensory structures when compared with non-self-medicating adults. Putative olfactory sensilla are reported on the proboscis of Nyctemera coleta and pollen grains were found adhered to the proboscis of Nyctemera secundiana. Sensilla on the observed tiger moth proboscides may play a role in the recognition of pyrrolizidine alkaloid plants by pharmacophagous adults.  相似文献   
665.
666.
Generalizations about the rate of behavioral development and mother-infant relations in nonhuman primates are often based largely on observations of a few closely related species of macaques. Patas monkeys (Erythrocebus patas)are sufficiently distant phylogenetically and distinct in their social and ecological adaptations from the well-studied macaque species that observations of their patterns of infant development and mother-infant relations may indicate to what extent macaque patterns are typical of Old World monkey species. Eight patas infants living with their mothers in an established captive group were observed for 960 hr over the first year of life. These infants showed a rapid rate of behavioral development and attainment of independence from mothers. Patas also have one of the fastest rates of sexual maturation of any Old World monkey species. This pattern of rapid social and sexual development can be viewed as a response to a highly seasonal savannah environment in which there is a premium on ability to achieve nutritional, locomotor, and social self-sufficiency as quickly as possible and to reproduce as early and as often as developmental constraints will permit. Patterns of infant development and mother-infant relations may be best understood as an integral part of a species’ overall life history pattern.  相似文献   
667.
Locomotor behavior and substrate use of cage-reared golden lion tamarins (Leontopithecus rosalia), newly released and free-ranging on the grounds of the National Zoological Park, were studied to determine if locomotion changed following exposure to naturalistic conditions. The animals employed a predominantly quadrupedal locomotor profile, incorporating leaping and vertical climbing to a lesser degree. There was no clear evidence of a change in locomotion due to the high degree of variability in these behaviors. The locomotor repertoire of the free-ranging group differed from that of groups occupying unenriched but relatively large conventional enclosures, indicating that whereas locomotion is plastic with respect to environment, substrate characteristics influence locomotor behavior and may promote stereotypical behavior. However, due to anatomical constraints, the locomotor repertoire tended to be less variable than substrate use. Similar behaviors were used in moving through a variety of habitat features in spite of strong associations between specific locomotor styles and substrate classes. © 1994 Wiley-Liss, Inc.  相似文献   
668.
Four monkeys were found able to learn to raise and lower hand temperature and to reduce muscle tension to low levels using feedback from the target physiological system. The establishment of this model of biofeedback learning in monkeys enables work on mechanisms mediating the modes of biofeedback most used in clinical practice. Results suggest that biofeedback learning does not need to be mediated by the type of human-specific cognitive strategies employed by humans.  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