全文获取类型
收费全文 | 4066篇 |
免费 | 391篇 |
出版年
2021年 | 52篇 |
2020年 | 45篇 |
2019年 | 55篇 |
2018年 | 61篇 |
2017年 | 61篇 |
2016年 | 77篇 |
2015年 | 161篇 |
2014年 | 155篇 |
2013年 | 212篇 |
2012年 | 236篇 |
2011年 | 262篇 |
2010年 | 165篇 |
2009年 | 152篇 |
2008年 | 189篇 |
2007年 | 220篇 |
2006年 | 199篇 |
2005年 | 202篇 |
2004年 | 242篇 |
2003年 | 206篇 |
2002年 | 160篇 |
2001年 | 73篇 |
2000年 | 80篇 |
1999年 | 59篇 |
1998年 | 66篇 |
1997年 | 37篇 |
1996年 | 33篇 |
1995年 | 27篇 |
1994年 | 40篇 |
1993年 | 35篇 |
1992年 | 35篇 |
1991年 | 40篇 |
1990年 | 29篇 |
1989年 | 33篇 |
1988年 | 30篇 |
1987年 | 45篇 |
1986年 | 48篇 |
1985年 | 41篇 |
1984年 | 35篇 |
1983年 | 48篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1980年 | 27篇 |
1979年 | 32篇 |
1978年 | 39篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1974年 | 27篇 |
1973年 | 18篇 |
1971年 | 24篇 |
排序方式: 共有4457条查询结果,搜索用时 31 毫秒
1.
2.
Jill Rafuse 《CMAJ》1995,153(5):655-656
The CMA hopes the Commission of Inquity on the Blood System, chaired by Mr. Justice Horace Krever, “will restore faith in a system that is essential for the health and safety of all Canadians.” However, the cost implications any recommendations may have for the health care system must also be taken into consideration. The CMA made several recommendations in response to the commission''s interim report. 相似文献
3.
4.
5.
C. Jill Stowe Michelle L. Kibler 《Journal of applied animal welfare science : JAAWS》2016,19(1):81-89
The unwanted horse issue continues to be a major concern in the U.S. equine industry. Nonprofit organizations dedicated to rescuing, retraining, and rehoming unwanted horses are critical in minimizing this problem. This study utilized data collected nationwide from organizations that provide these services for thoroughbreds retired from racing to identify individual horse characteristics that influenced length of stay at the adoption facility as well as characteristics that increased the probability that an adopted horse would be returned to the facility. The results suggested that horses with fewer activity limitations were rehomed more quickly (p < .01), as were gray horses (relative to bays, p < .03) and stallions (relative to geldings, p < .04). Older horses took longer to rehome (p < .05). Interestingly, the results also suggested that gray horses were more likely to be returned to the facility postadoption (p < .02). Results from this study could benefit thoroughbreds retired from racing, nonprofit organizations, end consumers, and the thoroughbred racing industry. 相似文献
6.
Jill S. Marty James P. Higham Elizabeth L. Gadsby Caroline Ross 《International journal of primatology》2009,30(6):807-823
Sexual selection has driven the evolution and elaboration of a wide variety of displays and ornaments in male nonhuman primates,
including capes, cheek flanges, and sexual coloration. Among the most sexually dimorphic of all primates is the drill (Mandrillus leucophaeus), the males of which can be 3 times the mass of females, possess large canines, and exhibit extremely bright sexual skin
coloration. However, the function of male coloration in this species has never been examined. Here, we present data on male
color (measured objectively using digital photography), dominance rank, measures of male-female association, and key sexual
behaviors, of adult male drills (n = 17) living in four semi free-ranging enclosures at the Drill Rehabilitation and Breeding Center in Nigeria. We test the
hypothesis that male coloration is a badge of status, indicating dominance rank, and the hypothesis that male coloration attracts
females. We found that male coloration did indicate rank, and that high ranking, strongly colored males were more likely to
associate with adult females, and more specifically with fully tumescent females. These males also engaged in more sexual
activity. However, measures of male-female association and sexual behaviors were not related to male color once rank had been
taken into consideration; i.e., for males of a given rank, females did not prefer those that were more colorful. We discuss
the results in light of what is known about the wild drill social system, in which unfamiliar individuals may come together
in “supergroups,” and in which quality indicators of competitive ability may be particularly important. 相似文献
7.
Shreaya Chakroborty Clark Briggs Megan B. Miller Ivan Goussakov Corinne Schneider Joyce Kim Jaime Wicks Jill C. Richardson Vincent Conklin Benjamin G. Cameransi Grace E. Stutzmann 《PloS one》2012,7(12)
Alzheimer’s disease (AD) is a devastating neurodegenerative condition with no known cure. While current therapies target late-stage amyloid formation and cholinergic tone, to date, these strategies have proven ineffective at preventing disease progression. The reasons for this may be varied, and could reflect late intervention, or, that earlier pathogenic mechanisms have been overlooked and permitted to accelerate the disease process. One such example would include synaptic pathology, the disease component strongly associated with cognitive impairment. Dysregulated Ca2+ homeostasis may be one of the critical factors driving synaptic dysfunction. One of the earliest pathophysiological indicators in mutant presenilin (PS) AD mice is increased intracellular Ca2+ signaling, predominantly through the ER-localized inositol triphosphate (IP3) and ryanodine receptors (RyR). In particular, the RyR-mediated Ca2+ upregulation within synaptic compartments is associated with altered synaptic homeostasis and network depression at early (presymptomatic) AD stages. Here, we offer an alternative approach to AD therapeutics by stabilizing early pathogenic mechanisms associated with synaptic abnormalities. We targeted the RyR as a means to prevent disease progression, and sub-chronically treated AD mouse models (4-weeks) with a novel formulation of the RyR inhibitor, dantrolene. Using 2-photon Ca2+ imaging and patch clamp recordings, we demonstrate that dantrolene treatment fully normalizes ER Ca2+ signaling within somatic and dendritic compartments in early and later-stage AD mice in hippocampal slices. Additionally, the elevated RyR2 levels in AD mice are restored to control levels with dantrolene treatment, as are synaptic transmission and synaptic plasticity. Aβ deposition within the cortex and hippocampus is also reduced in dantrolene-treated AD mice. In this study, we highlight the pivotal role of Ca2+ aberrations in AD, and propose a novel strategy to preserve synaptic function, and thereby cognitive function, in early AD patients. 相似文献
8.
9.
10.
Antibodies have been elicited to the nitroxide spin-label 4-maleimido-2,2,6,6-tetramethyl-piperidinyl-1-oxy conjugated, via protein sulfhydryl groups, to bovine serum albumin. Antibody-hapten cross-reactivity was demonstrated by double immunodiffusion and by a broadening of the nitroxide electron paramagnetic resonance spectrum. The specificity of the antibodies with respect to hapten structure was examined by means of a simple filter binding assay. Under these conditions, antibodies were shown to distinguish between the nitroxide and hydroxylamine derivatives and between spin-labels comprising either five- or six-membered ring structures. In addition, protein-bound nitroxide spin-labels were detected at the nanogram level by immunoblotting. By use of this method, the specificity of the antibody-hapten reaction predicted by the filter binding assay procedure was utilized to differentially detect various types of bound spin-label. Finally, antibodies were used to identify protein-bound nitroxide spin-label of protein fractionated by gel electrophoresis. 相似文献