全文获取类型
收费全文 | 191篇 |
免费 | 2篇 |
专业分类
193篇 |
出版年
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2007年 | 2篇 |
2005年 | 6篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1977年 | 2篇 |
1972年 | 2篇 |
1960年 | 4篇 |
1959年 | 3篇 |
1957年 | 2篇 |
1953年 | 3篇 |
1947年 | 2篇 |
1940年 | 2篇 |
1938年 | 4篇 |
1937年 | 2篇 |
1936年 | 9篇 |
1935年 | 5篇 |
1934年 | 2篇 |
1933年 | 8篇 |
1932年 | 9篇 |
1931年 | 9篇 |
1930年 | 2篇 |
1929年 | 7篇 |
1924年 | 2篇 |
1923年 | 3篇 |
1920年 | 2篇 |
1919年 | 1篇 |
1918年 | 3篇 |
1916年 | 1篇 |
1914年 | 1篇 |
1910年 | 2篇 |
1909年 | 1篇 |
1907年 | 1篇 |
排序方式: 共有193条查询结果,搜索用时 10 毫秒
1.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
2.
C. H. Wearing 《New Zealand journal of zoology.》2013,40(1):135-148
A technique is described whereby 5th‐instar larvae of the codling moth (Laspeyresia pomonella) which have finished feeding can be tagged externally with cobalt‐58 and released on apple trees, where they seek cocooning sites. Two μCi 58Co per insect did not significantly affect larval survival in the field, or subsequent pupation, emergence, mating, and oviposition in the laboratory. Tagging was more efficient than whole‐tree scraping for the location of cocoons, and was non‐destructive of both the insects and their cocooning sites.Relocation and observation of the tagged larvae in their cocoons permitted accurate estimation of mortality from when they left the fruit (= release) until adult emergence in the following spring. Natural mortality of larvae seeking cocooning sites was attributed mainly to insect predators, and varied significantly between trees and blocks, averaging 57% over 6 years. Avian predation by the silvereye (Zosterops lateralis) was the greatest hazard to cocooned larvae; this, too, varied significantly between blocks, and averaged 53% over the same period. Both mortalities appeared to be density‐related. 相似文献
3.
Julie?Webber Margaret?E.?JohnstonEmail author Alan?H.?Wearing 《In vitro cellular & developmental biology. Plant》2003,39(2):139-141
Summary
Caustis blakei is an attractive cut foliage plant harvested from the wild in Australia and marketed under the name of koala fern. Previous
attempts to propagate large numbers of this plant have been unsuccessful. The effect of four light irradiances on organogenesis
from compact and friable callus of C. blakei was studied for 21 wk. Both callus types produced numerous primordial shoots but many failed to develop into green plantlets.
However, significantly more primordial shoots and green plantlets developed on the friable callus than on the compact callus,
and significantly more green plantlets were regenerated under the higher photon irradiances of 200 and 300 μmol m−2s−1 than under the lower irradiances of 100 and 150 μmol m−2s−1. The compact callus produced its maximum number of green plantlets early in the experiment (after 9 wk), while the friable
callus continued to produce primordial shoots and green plantelets throughout the period of the experiment, and reached its
maximum production of green plantlets at 21 wk under the irradiance of 300 μmol m−2s−1. Organogenesis from friable callus under high irradiance (300 μmol m−2s−1) offers an efficient propagation method for C. blakei. 相似文献
4.
Spatial pattern formation is one of the key issues in developmental biology. Some patterns arising in early development have
a very small spatial scale and a natural explanation is that they arise by direct cell—cell signalling in epithelia. This
necessitates the use of a spatially discrete model, in contrast to the continuum-based approach of the widely studied Turing
and mechanochemical models. In this work, we consider the pattern-forming potential of a model for juxtacrine communication,
in which signalling molecules anchored in the cell membrane bind to and activate receptors on the surface of immediately neighbouring
cells. The key assumption is that ligand and receptor production are both up-regulated by binding. By linear analysis, we
show that conditions for pattern formation are dependent on the feedback functions of the model. We investigate the form of
the pattern: specifically, we look at how the range of unstable wavenumbers varies with the parameter regime and find an estimate
for the wavenumber associated with the fastest growing mode. A previous juxtacrine model for Delta-Notch signalling studied
by Collier et al. (1996, J. Theor. Biol.
183, 429–446) only gives rise to patterning with a length scale of one or two cells, consistent with the fine-grained patterns
seen in a number of developmental processes. However, there is evidence of longer range patterns in early development of the
fruit fly Drosophila. The analysis we carry out predicts that patterns longer than one or two cell lengths are possible with our positive feedback
mechanism, and numerical simulations confirm this. Our work shows that juxtacrine signalling provides a novel and robust mechanism
for the generation of spatial patterns. 相似文献
5.
Many signaling molecules in epithelia are now known to function in a membrane-bound form, binding to receptors on immediately neighbouring cells. This "juxtacrine" mode of communication has been well studied in the case of lateral inhibition, where ligand binding at the cell surface downregulates ligand and receptor expression, and is known to generate spatial patterns with a wavelength of exactly two cells. However, recent evidence shows that a number of juxtacrine signals can lead to the opposite phenomenon of lateral induction. Here, we use mathematical modeling to show that such positive feedback, in combination with juxtacrine communication, provides a novel mechanism for the generation of spatial patterns, with wavelengths that vary with parameters and can be many cell lengths. 相似文献
6.
JY Xiong SC Li YX Sun XS Zhang ZZ Dong P Zhong XR Sun 《Biology of sport / Institute of Sport》2015,32(4):295-300
Increasing evidence suggests that physical activity could delay or attenuate the symptoms of Alzheimer''s disease (AD). But the underlying mechanisms are still not fully understood. To investigate the effect of long-term treadmill exercise on the spatial memory of AD mice and the possible role of β-amyloid, brain-derived neurotrophic factor (BDNF) and microglia in the effect, male APPswe/PS1dE9 AD mice aged 4 months were subjected to treadmill exercise for 5 months with 6 sessions per week and gradually increased load. A Morris water maze was used to evaluate the spatial memory. Expression levels of β-amyloid, BDNF and Iba-1 (a microglia marker) in brain tissue were detected by immunohistochemistry. Sedentary AD mice and wildtype C57BL/6J mice served as controls. The results showed that 5-month treadmill exercise significantly decreased the escape latencies (P < 0.01 on the 4th day) and improved the spatial memory of the AD mice in the water maze test. Meanwhile, treadmill exercise significantly increased the number of BDNF-positive cells and decreased the ratios of activated microglia in both the cerebral cortex and the hippocampus. However, treadmill exercise did not significantly alleviate the accumulation of β-amyloid in either the cerebral cortex or the hippocampus of the AD mice (P > 0.05). The study suggested that long-term treadmill exercise could improve the spatial memory of the male APPswe/PS1dE9 AD mice. The increase in BDNF-positive cells and decrease in activated microglia might underpin the beneficial effect. 相似文献
7.
Darryl N. Jones Matthew Bakker Orphé Bichet Robert Coutts Tracy Wearing 《Ecological Management & Restoration》2011,12(1):76-79
The Compton Road overpass in southern Brisbane is known to be allowing passage by numerous birds, reptiles and amphibians; but what type of vegetation is providing habitat suitable for these movements? An evaluation of the reconstructed vegetation on the overpass shows that 45 species of plants were present after 4 years of growth. Most of these were in the original planting list but over 40% have almost certainly come from salvaged native topsoil used in the bypass construction. The resulting habitat, 4 years later, now appears similar to a typical coastal eucalypt forest secondary succession, although not yet identical to nearby forest. The current presence of a dense mid‐layer of small trees and shrubs may be an important factor in allowing even the edge‐avoiding species to cross the road. On‐going investigation of successional changes and the changing responses of the birds and other taxa will contribute to understanding the functionality of such crossing structures. 相似文献
8.
9.
10.