全文获取类型
收费全文 | 269篇 |
免费 | 33篇 |
专业分类
302篇 |
出版年
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 9篇 |
2012年 | 14篇 |
2011年 | 8篇 |
2010年 | 12篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 7篇 |
2006年 | 10篇 |
2005年 | 13篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 2篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 3篇 |
排序方式: 共有302条查询结果,搜索用时 15 毫秒
291.
Peter F. Favreau Joshua A. Deal Bradley Harris David S. Weber Thomas C. Rich Silas J. Leavesley 《Journal of biophotonics》2020,13(2)
A false‐colored and merged image of fresh, ex vivo rat kidney acquired using an excitation‐scanning hyperspectral imaging system. The spectral image was acquired using excitation wavelengths from 360 to 550 nm. Colors represent principal components extracted from a spectral image cube featuring no added labels or markers. Further details can be found in the article by Peter F. Favreau, Joshua A. Deal, Bradley Harris, et al. ( e201900183 ).
292.
Women's status in preindustrial communities has been the focus of a number of studies in the past two decades. However, very
few of these studies deal exclusively with hunter/gatherers, and none of the hunter/gatherer studies combine empirical tests
with explanations. Because of a number of differences with settled agricultural villagers, hunter/gatherers can be viewed
as the focus of distinctive substantive ecological theory. A cross-cultural materialist approach to the problem of why women's
status is high among some hunter/gatherers and low among others indicates that several factors are strongly related to differences
in women's status. Frequent and severe resource stress is the most strongly associated with low female status in the domestic
and political domain, while warfare exerts an independent but lesser effect. The importance of hunting constitutes a third
and still more weakly associated variable. Thus, women's political and domestic status among hunter/gatherers predominantly
appears to have resulted from techno-ecological conditions. In contrast, technoecological conditions appear to have had no
strong influence on women's status in ritual roles, including shamanism. Several possible ways that women's status might be
linked to techno-economic conditions are proposed. The results of this study demonstrate that Leacock's assumptions of systematic
bias in the ethnographic record, and of ubiquitous female equality among band level societies are unjustified. 相似文献
293.
Deal E. C. Jr; McFadden E. R. Jr; Ingram R. H. Jr; Strauss R. H.; Jaeger J. J. 《Journal of applied physiology》1979,46(3):467-475
294.
295.
A Oliven E C Deal S G Kelsen N S Cherniack 《Journal of applied physiology (Bethesda, Md. : 1985)》1984,56(6):1583-1588
The ability to maintain alveolar ventilation is compromised by respiratory muscle weakness. To examine the independent role of reflexly mediated neural mechanisms to decreases in the strength of contraction of respiratory muscles, we studied the effects of partial paralysis on the level and pattern of phrenic motor activity in 22 anesthetized spontaneously breathing dogs. Graded weakness induced with succinylcholine decreased tidal volume and prolonged both inspiratory and expiratory time causing hypoventilation and hypercapnia. Phrenic peak activity as well as the rate of rise of the integrated phrenic neurogram increased. However, when studied under isocapnic conditions, increases in the severity of paralysis, as assessed from the ratio of peak diaphragm electromyogram to peak phrenic activity, produced progressive increases in inspiratory time and phrenic peak activity but did not affect its rate of rise. After vagotomy, partial paralysis induced in 11 dogs with succinylcholine also prolonged the inspiratory burst of phrenic activity, indicating that vagal reflexes were not solely responsible for the alterations in respiratory timing. Muscle paresis was also induced with gallamine or dantrolene, causing similar responses of phrenic activity and respiratory timing. Thus, at constant levels of arterial CO2 in anesthetized dogs, respiratory muscle partial paralysis results in a decrease in breathing rate without changing the rate of rise of respiratory motor activity. This is not dependent solely on vagally mediated reflexes and occurs regardless of the pharmacological agent used. These observations in the anesthetized state are qualitatively different from the response to respiratory muscle paralysis or weakness observed in awake subjects.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
296.
The Jovian planets have environments apparently suitable for the evolution of life, but, nevertheless, present severe challenges to organisms. One such challenge arises from the presence of ammonia. Ammonia is an efficient biocide, its effect being dependent on pH as well as on concentration. The effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural environments of high pH and/or ammonia concentration. Escherichia coli andBacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, survival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is, nevertheless, two to three orders of magnitude longer than forE. coli. Our data support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible. 相似文献
297.
298.
299.
MS Nandhu Jes Paul Korah P Kuruvilla Anitha Malat Chinthu Romeo CS Paulose 《Journal of biomedical science》2011,18(1):5
Parkinson's disease is characterized by progressive cell death in the substantia nigra pars compacta, which leads to dopamine
depletion in the striatum and indirectly to cortical dysfunction. Increased glutamatergic transmission in the basal ganglia
is implicated in the pathophysiology of Parkinson's disease and glutamate receptor mediated excitotoxicity has been suggested
to be one of the possible causes of the neuronal degeneration. In the present study, the effects of serotonin, gamma-aminobutyric
acid and bone marrow cells infused intranigrally to substantia nigra individually and in combination on unilateral 6-hydroxydopamine
induced Parkinson's rat model was analyzed. Scatchard analysis of total glutamate and NMDA receptor binding parameters showed
a significant increase in Bmax (P < 0.001) in the cerebral cortex of 6-hydroxydopamine infused rat compared to control. Real Time PCR amplification of NMDA2B,
mGluR5, bax, and ubiquitin carboxy-terminal hydrolase were up regulated in cerebral cortex of 6-hydroxydopamine infused rats
compared to control. Gene expression studies of GLAST, ά-Synuclien and Cyclic AMP response element-binding protein showed
a significant (P < 0.001) down regulation in 6-OHDA infused rats compared to control. Behavioural studies were carried out
to confirm the biochemical and molecular studies. Serotonin and GABA along with bone marrow cells in combination showed reversal
of glutamate receptors and behaviour abnormality shown in the Parkinson's rat model. The therapeutic significance in Parkinson's
disease is of prominence. 相似文献
300.
Haxhiu M. A.; Deal E. C.; Van Lunteren E.; Cherniack N. S. 《Journal of applied physiology》1993,75(6):2353-2359