全文获取类型
收费全文 | 1155篇 |
免费 | 115篇 |
国内免费 | 1篇 |
出版年
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 40篇 |
2014年 | 39篇 |
2013年 | 48篇 |
2012年 | 72篇 |
2011年 | 67篇 |
2010年 | 51篇 |
2009年 | 42篇 |
2008年 | 54篇 |
2007年 | 73篇 |
2006年 | 55篇 |
2005年 | 75篇 |
2004年 | 68篇 |
2003年 | 69篇 |
2002年 | 54篇 |
2001年 | 16篇 |
2000年 | 23篇 |
1999年 | 32篇 |
1998年 | 13篇 |
1997年 | 16篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1976年 | 7篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 8篇 |
1970年 | 6篇 |
1953年 | 6篇 |
排序方式: 共有1271条查询结果,搜索用时 125 毫秒
941.
942.
Roderick A. Suthers 《Developmental neurobiology》1997,33(5):632-652
Recent studies on several species of oscine songbirds show that they achieve their varied vocal performances through coordinated activity of respiratory, syringeal, and other vocal tract muscles in ways that take maximum advantage of the acoustic flexibility made possible by the presence of two independently controlled sound sources in their bipartite syrinx (vocal organ). During song, special motor programs to respiratory muscles alter the pattern of ventilation to maintain the supply of respiratory air and oxygen to permit songs of long duration, high syllable repetition rates, or maximum spectral complexity. Each side of the syrinx receives its own motor program that, together with that sent to respiratory muscles, determines the acoustic properties of the ipsilaterally produced sound. The acoustic expression of these bilaterally distinct, phonetic motor patterns depends on the action of dorsal syringeal adductor muscles that, by opening or closing the ipsilateral side of the syrinx to airflow, determine the amount each side contributes to song. The syringeally generated sound is further modified by muscles that control the shape of the vocal tract. Different species have adopted different motor strategies that use the left and right sides of the syrinx in patterns of unilateral, bilateral, alternating, or sequential phonation to achieve the differing temporal and spectral characteristics of their songs. As a result, the degree of song lateralization probably varies between species to form a continuum from unilateral dominance to bilateral equality. © 1997 John Wiley & Sons, Inc. J Neurobiol 33: 632–652, 1997 相似文献
943.
Anna Lintunen Teemu Paljakka Yann Salmon Roderick Dewar Anu Riikonen Teemu Hölttä 《Plant, cell & environment》2020,43(3):532-547
Understanding stomatal regulation is fundamental to predicting the impact of changing environmental conditions on vegetation. However, the influence of soil temperature (ST) and soil water content (SWC) on canopy conductance (gs) through changes in belowground hydraulic conductance (kbg) remains poorly understood, because kbg has seldom been measured in field conditions. Our aim was to (a) examine the dependence of kbg on ST and SWC, (b) examine the dependence of gs on kbg and (c) test a recent stomatal optimization model according to which gs and soil-to-leaf hydraulic conductance are strongly coupled. We estimated kbg from continuous sap flow and xylem diameter measurements in three boreal species. kbg increased strongly with increasing ST when ST was below +8°C, and typically increased with increasing SWC when ST was not limiting. gs was correlated with kbg in all three species, and modelled and measured gs were well correlated in Pinus sylvestris (a model comparison was only possible for this species). These results imply an important role for kbg in mediating linkages between the soil environment and leaf gas exchange. In particular, our finding that ST strongly influences kbg in mature trees may help us to better understand tree behaviour in cold environments. 相似文献
944.
Roderick K. Clayton 《Archives of microbiology》1955,22(2):195-203
Summary In the presence of both light and air, the metabolism of Rhodospirillum rubrum can be partly respiratory and partly photosynthetic. The relative rates of these modes of metabolism have been measured at a variety of light intensities and oxygen tensions. 相似文献
945.
Male and female hamsters and gerbils were randomly assigned to one of three groups. The animals were tested under ad lib feeding conditions or food deprived until they had lost either 10% or 20% of their predeprivation body weight. They were given a 30-min. hoarding test for three consecutive days. The results indicated that although food-deprived gerbils ate more than control gerbils, deprivation had no significant effect on the food intake of hamsters. A sex difference was also evident in the food intake of gerbils; males ate more than did females. Although there was a sex and species difference in the amount of hoarding, deprivation had no significant effect on the amount of hoarding. The implications of these results for of different models of hoarding are discussed. These models contrast hoarding as a defensive response in the regulation of body weight or as an anticipatory activity that is influenced by other selection pressures. 相似文献
946.
947.
Jan-Willem Taanaman Robin E. Hall Chunlin Tang Michael F. Marusich Nancy G. Kennaway Roderick A. Capaldi 《生物化学与生物物理学报:疾病的分子基础》1993,1225(1):95-100
Monoclonal and polyclonal antibodies specific to the two isoforms of subunit VIa of bovine cytochrome c oxidase were generated and used to study the tissue distribution of this subunit pair in beef, human and rat. The so-called H-(heart) form was found exclusively in heart and skeletal muscle, whereas the so-called L-(liver) form was the only isoform present in brain, kidney, liver and smooth muscle. Little or no L-form was detected in skeletal muscle. In bovine heart no subunit VIa-L was detected, while in human heart the subunit VIa-H and VIa-L isoforms were present in roughly equal proportions. These results imply that, in humans, the deficiency of a subunit VIa isoform may have a different effect on the physiology of heart then on the physiology of skeletal muscle. 相似文献
948.
James E. Womack Norman L. Hawes Eugene R. Soares Thomas H. Roderick 《Biochemical genetics》1975,13(9-10):519-525
Malate dehydrogenase is present in most mammalian tissues in both supernatant and mitochondrial forms. Although genetic variation for the supernatant form has not been observed in the mouse, electrophoretic variants caused by alleles at the mitochondrial locus (Mor-1) have been previously described. We have located this locus 11.0 +/- 2.9 cM from the beta-glucuronidase structural gene, Gus, on chromosome 5. The gene order is Hm-Pgm-1-rd-bf-Gus-Mor-1. Thus Mor-1 is presently the most distal marker on chromosome 5. Three different nuclear loci for mitochondrial enzymes (Mod-2, Got-2, and Mor-1) have now been mapped in the mouse, all on different chromosomes. 相似文献
949.
950.
Evan Weiher Adrie van der Werf Ken Thompson Michael Roderick Eric Garnier Ove Eriksson 《植被学杂志》1999,10(5):609-620
Abstract. Ecologists need a common language of plant traits in order to make comparisons across regions and scales, pool data, and maximize the utility of the data. To develop such a set of traits we began with the primary challenges faced by plants: dispersal, establishment, and persistence in order to identify fundamental traits. Most of these traits are hard to measure, but advances in comparative ecology have suggested a number of easy to measure analogs. Unfortunately, some of the fundamental traits have no simple analog. The common core list includes: seed mass, seed shape, dispersal mode, clonality, specific leaf area, leaf water content, height, above-ground biomass, life history, onset of flowering, stem density, and resprouting ability. Most of the traits can be measured quantitatively, but several traits on the list must still be measured qualitatively due to logistical problems or lack of an easy analog. Key problem areas include: dispersal ability, capacity for vegetative spread, germination, palatability, plasticity, and all the various below-ground traits. Comparative studies need to address these problem areas. The common core list is suggested as a common starting point for studies of functional ecology. The idiosyncrasies of regional floras and specific research agendas will dictate which traits can be ignored and those that need to be added. 相似文献