全文获取类型
收费全文 | 589篇 |
免费 | 13篇 |
出版年
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 35篇 |
2012年 | 21篇 |
2011年 | 22篇 |
2010年 | 31篇 |
2009年 | 31篇 |
2008年 | 31篇 |
2007年 | 28篇 |
2006年 | 28篇 |
2005年 | 23篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 24篇 |
1996年 | 14篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1974年 | 8篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1957年 | 3篇 |
1953年 | 4篇 |
1951年 | 3篇 |
1950年 | 3篇 |
排序方式: 共有602条查询结果,搜索用时 15 毫秒
531.
532.
533.
MARIA ANGÉLICA CARRASCO YVETTE MOROT GAUDRY-TALARMAIN JORDI MOLGO 《Neurochemistry international》1996,29(6):637-643
The aim of the present study was to investigate possible changes of inositol 1,4,5-trisphosphate (IP3) mass in Torpedo cholinergic synaptosomes in conditions promoting stimulated acetylcholine (ACh) release. For this purpose, we used a radioreceptor IP3 mass assay and a chemiluminescent method for ACh detection. Torpedo cholinergic synaptosomes have consistent IP3 mass levels under resting conditions. The IP3 mass was neither modified by changes in external Ca2+ nor by a Ca2+-free medium containing EGTA. IP3 mass and ACh release, measured in the same conditions and in parallel, were increased by depolarization with high K+ and by the ionophores A-23187 and gramicidin-D in a manner dependent on external Ca2+ emphasizing that Ca2+ entry, independently of the influx mechanism involved, leads to an IP3 increase. The phospholipase Cβ inhibitors U-73122 and U-73343 reduced K+-stimulated IP3 levels while K+-evoked ACh release was almost completely blocked suggesting an additional effect of these drugs on depolarization-neurotransmitter secretion coupling. The effect reported showing an increase of IP3 by agents that stimulate ACh release may suggest a possible link between IP3 metabolism and the neurotransmitter release mechanism. However, such a link is probably not a direct one as implied by the results obtained with the inhibitors of phospholipase C. Copyright © 1996 Elsevier Science Ltd 相似文献
534.
MARIA LASMAN 《Development, growth & differentiation》1987,29(5):547-552
Acanthamoeba palestinensis grown in monolayer cultures encysted almost synchronously at a stationary phase, with a yield of about 80% cysts. Under these growth conditions an encystmentinducing factor was released into the medium by transforming amoebae. Cell-free supernatants induced encystment of amoebae from early-log phase cultures. The not dialyzable encystment factor was resistant to nuclease, protease and trypsin digestion, as well as to boiling, but the activity was almost completely destroyed by autoclaving. Isolation and further characterization of the factor will enable clarification of the mode of its action as a regulator of amoeba-cyst transformation. 相似文献
535.
MARIA REYMANÓWNA 《Botanical journal of the Linnean Society. Linnean Society of London》1968,61(384):147-152
Together with other plant remains of Upper Liassic-Aalenian age there were found in Grojec near Krakow, Poland, seeds known from the Yorkshire Gristhorpe Bed as Allicospermum relemirum Harris. On maceration these seeds showed in their pollen chamber and mieropyle, pollen of Eucommiidites troedssonii Erdtman which adds to similar evidence provided already by Hughes (1961) and Brenner (1966).
The structure of the seed is described, discussed and compared with that of Spermatites pettensis Hughes which contained pollen of Eucommiidites delcourtii Hughes. S. pettensis is shown to agree in structure with the macerated A. retemirum , but it is of a different size. A. retemirum is considered to be related to either the Ginkgoales, Cycadales or Pteridosperms, or else to a new, not yet known group of plants. Its affinity with the Chlamydospermales is considered less likely. 相似文献
The structure of the seed is described, discussed and compared with that of Spermatites pettensis Hughes which contained pollen of Eucommiidites delcourtii Hughes. S. pettensis is shown to agree in structure with the macerated A. retemirum , but it is of a different size. A. retemirum is considered to be related to either the Ginkgoales, Cycadales or Pteridosperms, or else to a new, not yet known group of plants. Its affinity with the Chlamydospermales is considered less likely. 相似文献
536.
537.
538.
THAINE ROBERT; de MARIA MARGARET E.; SARISALO H. I. MARJATTA 《Journal of experimental botany》1975,26(1):91-101
Transverse cryostat sections of rapidly frozen vascular bundlesof Cucurbita pepo were viewed in a microscope with Nomarskioptics. Structural bodies were frequently observed in sievetube lumina and filling the sieve plate pores. The bodies consistof an outer boundary ring and an inner core, often granularin appearance, and may represent transverse sections of boundedtubes filled by substructural material. This evidence is consistentwith earlier observations of strand-like structures with parallelsubstructural elements seen in longitudinal sections. 相似文献
539.
ANNA CERRA MARIA BYRNE OVE HOEGH-GULDBERG 《Invertebrate reproduction & development.》2013,57(1-3):337-343
Summary The hyaline layer (HL) around the embryos and larvae of Patiriella calcar is examined by transmission electron microscopy. P. calcar hatches at the gastrula stage and develops through a lecithotrophic planktonic brachiolaria. The hyaline layer of unhatched P. calcar is poorly developed and is comprised of wispy fibrils scattered among the epithelial microvilli. Fibrils are also occasionally seen associated with the inner surface of the fertilization envelope. By the hatched gastrula stage, the hyaline layer is organized into three strata: the intervillous layer, the supporting layer and the coarse outer meshwork layer. Seven-day-old brachiolaria also have a hyaline layer comprised of three strata. In these larvae the supporting layer elevates away from the epithelial surface due to the tuft-like organization of the underlying microvilli. This results in the formation of local outpockets giving the surface of the HL a lobed appearance. Bacteria are occassionally seen in the intervillous layer, particularly in association with the outpockets. These bacteria are phagocytosed by the epithelial cells and, in larvae that have bacteria, may play an augmentive role in larval nutrition. The structure of the hyaline layer of P. calcar is compared with that of the hyaline layer of other Patiriella species to determine if it is more similar to the external coats around its planktonic (P. regularis) or benthic (P. exigua) developing congeners. The comparison shows that the hyaline layer of P. calcar is virtually identical to that of P. regularis, a similarity that may reflect the pelagic life histories of these species. 相似文献
540.