首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   318篇
  免费   33篇
  2023年   2篇
  2022年   3篇
  2021年   6篇
  2020年   2篇
  2019年   6篇
  2018年   8篇
  2017年   6篇
  2016年   3篇
  2015年   16篇
  2014年   17篇
  2013年   13篇
  2012年   18篇
  2011年   16篇
  2010年   16篇
  2009年   7篇
  2008年   24篇
  2007年   22篇
  2006年   11篇
  2005年   12篇
  2004年   18篇
  2003年   15篇
  2002年   13篇
  2001年   12篇
  2000年   6篇
  1999年   9篇
  1998年   7篇
  1997年   13篇
  1996年   4篇
  1995年   4篇
  1994年   3篇
  1992年   6篇
  1990年   2篇
  1989年   2篇
  1988年   2篇
  1985年   5篇
  1983年   3篇
  1982年   3篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1976年   3篇
  1972年   1篇
  1971年   2篇
  1968年   1篇
  1961年   1篇
  1910年   1篇
  1900年   1篇
排序方式: 共有351条查询结果,搜索用时 278 毫秒
1.
In Saccharomyces cerevisiae, the unconventional myosin Myo2p is of fundamental importance in polarized growth. We explore the role of the neck region and its associated light chains in regulating Myo2p function. Surprisingly, we find that precise deletion of the six IQ sites in the neck region results in a myosin, Myo2-Δ6IQp, that can support the growth of a yeast strain at 90% the rate of a wild-type isogenic strain. We exploit this mutant in a characterization of the light chains of Myo2p. First, we demonstrate that the localization of calmodulin to sites of polarized growth largely depends on the IQ sites in the neck of Myo2p. Second, we demonstrate that a previously uncharacterized protein, Mlc1p, is a myosin light chain of Myo2p. MLC1 (YGL106w) is an essential gene that exhibits haploinsufficiency. Reduced levels of MYO2 overcome the haploinsufficiency of MLC1. The mutant MYO2-Δ6IQ is able to suppress haploinsufficiency but not deletion of MLC1. We used a modified gel overlay assay to demonstrate a direct interaction between Mlc1p and the neck of Myo2p. Overexpression of MYO2 is toxic, causing a severe decrease in growth rate. When MYO2 is overexpressed, Myo2p is fourfold less stable than in a wild-type strain. High copies of MLC1 completely overcome the growth defects and increase the stability of Myo2p. Our results suggest that Mlc1p is responsible for stabilizing this myosin by binding to the neck region.  相似文献   
2.
3.
We analysed clutch size versus nest size in 153 broods of the Northern Flicker Colaptes auratus , a woodpecker using natural cavities in British Columbia, Canada. Larger volume cavities were less susceptible to predation and cavity size was positively associated with the age and body size of males and with the body condition of female parents. Although clutches varied between 4 and 11 eggs, and the floor area of cavities varied about 5-fold, we found no relationship between clutch size and floor area or cavity volume. To see if there were fitness consequences to clutch size relative to nest size, we examined hatching success and nestling mortality in flicker broods. Hatching success was not related to cavity size, but crowding slightly reduced nestling survival even when clutch size was controlled statistically. However, there was no effect of cavity size on the total number of nestlings fledged. Newly excavated flicker cavities were smaller than reused cavities suggesting a cost to excavation. This cost, coupled with the minimal fitness consequences of overcrowding, may explain why flickers do not adjust clutch size to cavity size.  相似文献   
4.
The isolation and characterization of 10 isolates of six Fusarium spp. from plant and soil samples collected in Southeast Asia is reported. The ability of these isolates to produce trichothecenes both in liquid cultures (CZ, GYEP, and MYRO) and on rice was assessed, and their toxigenic potential was examined by skin assay and gavage studies with culture filtrates. Although culture filtrates of all the isolates caused minor damage to test animals, only that of F. equiseti DAOM 189762 produced trichothecenes.  相似文献   
5.
6.
The fall in ankle systolic pressure after exercise serves as an objective indicator of the severity of haemodynamically important peripheral arterial disease. Twenty-six patients were studied to establish the effects of different work loads on the pressure response and to develop a test to standardise these effects. The patients walked for one or two minutes at 4 km/h and one or two minutes at 6 km/h, and the fall in pressure was the same when measured immediately after exercise. The time taken for the pressure to return to the pre-exercise value varied. As the fall in pressure occurs after only one minute of exercise at 4 km/h on a 10% slope, this might be adopted as a standard test. It is acceptable to the patient, since claudication, angina, and shortness of breath rarely occur. It is sensitive enough to detect mild or asymptomatic disease and is useful in following up patients.  相似文献   
7.
  1. Freshwater conservation is vital to the maintenance of global biodiversity. Ponds are a critical, yet often under‐recognized, part of this, contributing to overall ecosystem functioning and diversity. They provide habitats for a range of aquatic, terrestrial, and amphibious life, often including rare and declining species.
  2. Effective, rapid, and accessible survey methods are needed to enable evidence‐based conservation action, but freshwater taxa are often viewed as “difficult”—and few specialist surveyors are available. Datasets on ponds are therefore limited in their spatiotemporal coverage.
  3. With the advent of new recording technologies, acoustic survey methods are becoming increasingly available to researchers, citizen scientists, and conservation practitioners. They can be an effective and noninvasive approach for gathering data on target species, assemblages, and environmental variables. However, freshwater applications are lagging behind those in terrestrial and marine spheres, and as an emergent method, research studies have employed a multitude of different sampling protocols.
  4. We propose the Pond Acoustic Sampling Scheme (PASS), a simple protocol to allow a standardized minimal sample to be collected rapidly from small waterbodies, alongside environmental and methodological metadata. This sampling scheme can be incorporated into a variety of survey designs and is intended to allow access to a wide range of participants, without requiring complicated or prohibitively expensive equipment.
  5. Adoption of this sampling protocol would enable consistent sound recordings to be gathered by researchers and conservation organizations, and allow the development of landscape‐scale surveys, data sharing, and collaboration within an expanding freshwater ecoacoustic community—rather than individual approaches that produce incompatible datasets. The compilation of standardized data would improve the prospects for effective research into the soundscapes of small waterbodies and aid freshwater conservation efforts.
  相似文献   
8.
9.
A new concept for filing medical records in general practice is described, based on an A4-size folder; in experimental use in 40 practices doctors were generally in favour of the new system.  相似文献   
10.
Twelve mature wethers were used in an experiment of change-over design to determine the effect of complete diet feeding on intake and digestibility of diets based on alkalitreated straw and a concentrate containing rolled barley and extracted soya bean meal. Two diets were used: D1 with a 50:50, and D2 with a 75:25 ratio of straw:concentrates on a dry matter basis. The straw and concentrates of each diet were given either separately (S) or as a complete diet (C). Complete diets gave a slightly, but not significantly higher intake (C, 86.5) and S, 82.5 g dry matter /kg W0.75 per day). The separate method gave a significantly higher digestibility coefficient for dry matter (C, 62.2 and S, 65.5; P < 0.05) and for crude fibre (C, 57.2 and S, 62.5; P < 0.01). Water intake increased by 42.7 ml g?1 Na derived from NaOH. There were no significant interactions between the method of feeding and the type of diet in intake and digestibility of the diets or in the intake of water.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号