全文获取类型
收费全文 | 342篇 |
免费 | 37篇 |
专业分类
379篇 |
出版年
2021年 | 3篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 24篇 |
2012年 | 9篇 |
2011年 | 19篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 4篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 13篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1978年 | 14篇 |
1977年 | 3篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1969年 | 5篇 |
1968年 | 6篇 |
1967年 | 8篇 |
1966年 | 4篇 |
1965年 | 3篇 |
1962年 | 2篇 |
1961年 | 4篇 |
1951年 | 2篇 |
1932年 | 2篇 |
排序方式: 共有379条查询结果,搜索用时 0 毫秒
1.
2.
Effects of fire on vesicular-arbuscular mycorrhizal fungi were tested using microcosms constructed from soil, litter, and duff collected beneath canopies of pinyon pine, Utah juniper, and in the open space (interspace). Burning was conducted over wet and dry soils. Soil temperatures were monitored continuously throughout the microcosms during burning. Plants grown in soils burned when dry had a lower VAM colonization than soils burned when wet. Juniper soils demonstrated the greatest reduction, over 95%, compared to their respective controls. Plants grown in interspace soils burned when wet were least affected. There was a positive correlation (r2=0.90) between the decrease in VAM colonization and the soil temperature as a result of the fire. Temperature effects, and associated reductions in VAM, were related to amount of litter burned in each microcosm and the moisture content of the soils. 相似文献
3.
Serially propagated with 3T3 feeder layer support, epithelial cells derived from normal rat endometrium expressed estrogen receptor activity. Specific binding of 17-beta-estradiol was in the range of 30-60 fmol/mg of protein and was of high affinity (Kd = 0.3 nM). A survey of cell lines derived from several other normal epithelia showed that rat vaginal and human cervical cultures also had high-affinity estrogen receptors (6-13 fmol/mg of protein), while rat epidermal and esophageal cells had no detectable activity. In the endometrial cultures, receptor levels were elevated nearly two- to fourfold by cholera toxin or forskolin in the medium. This effect was detectable after 4 hr but not 1 hr of treatment and did not occur in the presence of cycloheximide. We conclude that serially cultivated rat endometrial cells retain hormonal properties expressed in vivo while exhibiting some keratinocyte character. These cells may provide a useful model for study of receptor modulation. 相似文献
4.
Plastids affected by either iojap or chloroplast mutator fail to green, and altered plastids are maternally transmitted to subsequent generations. The ultrastructure of iojap-affected plastids indicates that these plastids contain no ribosomes and are capable of supporting little internal membrane organization in either light or dark-grown plants. Chloroplast mutator-affected plastids of light-grown plants contain some organized internal membrane structures. In dark-grown plants, chloroplast mutator-aftected plastids contain a crystalline prolamellar body, numerous vesicles, and osmiophilic granules. The chloroplast mutator-affecled etioplasts display an abnormal distribution of lamellar membranes; these membranes, rather than radiating in a spokelike pattern from the prolamellar body, are condensed into a portion of the organelle. Light causes disruption of the prolamellar body in chloroplast mutator-affected plastids without promoting the organization of a normal thylakoid membrane system. The effects of iojap and chloroplast mutator are cell autonomous and apparently influence the individual plastid, as evidenced by the persistence of heteroplastidic cells containing normal and affected plastids. 相似文献
5.
6.
Book reviewed in this article:
ARCHEOLOGY: Papers of the New World Archaeological Foundation
No. 6. The Carved Human Femurs from Tomb 1, Chiapa de Corzo, Chiapas, Mexico . P ierre A grinier
No. 7. Archaeological Explorations in the Region of the Frailesca, Chiapas, Mexico . C arlos N avarrete
Nos. 8–11. Excavations at Chiapa de Corzo, Chiapas, Mexico . G areth W. L owe
No. 12. Mound 5 and Minor Excavations, Chiapa de Corzo, Chiapas, Mexico . G areth W. L owe
No. 13. Ceramic Stratigraphy at Santa Cruz, Chiapas, Mexico . W illiam T. S anders
No. 14. The Santa Marta Rock Shelter, Ocozocoautla, Chiapas, Mexico . R ichard S. M ac N eish and F redrick A. P eterson 相似文献
ARCHEOLOGY: Papers of the New World Archaeological Foundation
No. 6. The Carved Human Femurs from Tomb 1, Chiapa de Corzo, Chiapas, Mexico . P ierre A grinier
No. 7. Archaeological Explorations in the Region of the Frailesca, Chiapas, Mexico . C arlos N avarrete
Nos. 8–11. Excavations at Chiapa de Corzo, Chiapas, Mexico . G areth W. L owe
No. 12. Mound 5 and Minor Excavations, Chiapa de Corzo, Chiapas, Mexico . G areth W. L owe
No. 13. Ceramic Stratigraphy at Santa Cruz, Chiapas, Mexico . W illiam T. S anders
No. 14. The Santa Marta Rock Shelter, Ocozocoautla, Chiapas, Mexico . R ichard S. M ac N eish and F redrick A. P eterson 相似文献
7.
The properties, origin, and mechanism of conversion-type inheritance at the B locus in maize 总被引:4,自引:3,他引:1
下载免费PDF全文
![点击此处可从《Genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Coe EH 《Genetics》1966,53(6):1035-1063
8.
9.
Book reviewed in this article:
LINGUISTICS: Pis'mennost'
LINGUISTICS: Pis'mennost'
10.
Previous references to "necking" behaviour, and the main features of the study area are briefly outlined.
"Necking" behaviour in giraffe takes place only in all male herds. When the animals are in a head to head posture the intensity is either high or low, but when animals take up a head to tail posture the actions are always of high intensity and appear to have greater sexual significance.
The significance of "necking" is discussed, and it is suggested that these ritualized actions form an important sexuo-social bonding mechanism whereby a hierarchy is created amongst the males, and movement between strictly bachelor and mixed herds helps to maintain contact between the sexes in this polygamous mammal. 相似文献
"Necking" behaviour in giraffe takes place only in all male herds. When the animals are in a head to head posture the intensity is either high or low, but when animals take up a head to tail posture the actions are always of high intensity and appear to have greater sexual significance.
The significance of "necking" is discussed, and it is suggested that these ritualized actions form an important sexuo-social bonding mechanism whereby a hierarchy is created amongst the males, and movement between strictly bachelor and mixed herds helps to maintain contact between the sexes in this polygamous mammal. 相似文献