全文获取类型
收费全文 | 603篇 |
免费 | 31篇 |
国内免费 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 25篇 |
2014年 | 38篇 |
2013年 | 33篇 |
2012年 | 53篇 |
2011年 | 43篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 44篇 |
2007年 | 47篇 |
2006年 | 40篇 |
2005年 | 37篇 |
2004年 | 29篇 |
2003年 | 37篇 |
2002年 | 21篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有635条查询结果,搜索用时 672 毫秒
621.
Morphology of the teleost ampullary organs in marine salmontail catfish Neoarius graeffei (Pisces: Ariidae) with comparative analysis to freshwater and estuarine conspecifics
下载免费PDF全文
![点击此处可从《Journal of morphology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Arnault R.G. Gauthier Darryl L. Whitehead Michael B. Bennett Ian R. Tibbetts 《Journal of morphology》2015,276(9):1047-1054
We hypothesized that due to the relative conductivity of the environment, and to maintain sensory function, ampullary organs of marine Neoarius graeffei would differ morphologically from those described previously for estuarine and freshwater conspecifics. Unlike the ampullary systems of N. graeffei from freshwater and estuarine habitats, the ampullary pores of marine specimens occur in two distinct patterns; numerous pores seemingly randomly scattered on the head and ventro‐lateral regions of the body, and pores arranged in distinctive vertical lines above the lateral line on the dorso‐lateral body of the fish. Light and electron microscopy revealed that the ampullary organs also differed morphologically from estuarine and freshwater specimens in the presence of longer ampullary canals, a hitherto unreported canal wall composition, and in the collagen sheath surrounding both the canal and the ampulla proper within dermal connective tissues. Ampullary pores were wider in marine individuals and opened to the longest ampullary canals reported for this species. The canal wall was lined by cuboidal and squamous epithelial cells. Each ampullary canal opened into a single ampulla proper containing significantly more receptor cells than estuarine and freshwater conspecifics. The distribution of ampullary pores as well as the microstructure of the ampullary organs indicates that the electrosensory system of marine N. graeffei differs from those of estuarine and freshwater specimens in ways that would be expected to maintain the functionality of the system in a highly conductive, fully marine environment, and reveals the remarkable plasticity of this species’ ampullary system in response to habitat conductivity. J. Morphol. 276:1047–1054, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
622.
Wild bird feeding is one of the most common forms of human-wildlife interactions in the Western world. Originally a practice providing nutritional assistance to over-wintering birds, especially in more northern latitudes, birds throughout the cities of the world are now provided with considerable amounts and a variety of foods year-round. Despite the global nature of the practice, remarkably little is known about the outcomes and implications of what may be seen as a supplementary feeding experiment on a massive scale. Although many claims are made about the benefits of feeding, there are growing concerns about the spread of disease, poor nutrition, risk of dependency and many other important issues. Constructive debate among increasingly vigorous proponents and opponents is currently constrained by a lack of reliable information. Here we argue that bird feeding provides an important, if challenging, opportunity for fundamental research in urban ecology. 相似文献
623.
624.
625.
Yonnie Wu Richard C Laughlin David C Henry Darryl E Krueger JoAn S Hudson Cheng-Yi Kuan Jian He Jason Reppert Jeffrey P Tomkins 《BMC cell biology》2007,8(1):36
Background
Tubular shaped mammalian cells in response to dehydration have not been previously reported. This may be due to the invisibility of these cells in aqueous solution, and because sugars and salts added to the cell culture for manipulation of the osmotic conditions inhibit transformation of normal cells into tubular shaped structures. 相似文献626.
Rebecca E. Wagner Serena Mugnaini Richard Sniezko Darryl Hardie Brett Poulis Massimo Nepi Ettore Pacini Patrick von Aderkas 《Sexual plant reproduction》2007,20(4):181-189
The pollination droplet is a highly conservative pollination mechanism that is observed in all major gymnosperm taxa. Proteomics
analysis of the pollination drops was carried out on four gymnosperm species: Juniperus communis (common juniper), Juniperus oxycedrus (prickly juniper), Chamaecyparis lawsoniana (Port Orford cedar), and Welwitschia mirabilis. Pollination drop proteins were purified by SDS-PAGE, and the most abundant proteins were analyzed by mass spectrometry and
sequenced. Based on BLAST searching of combined amino acid sequences, the following proteins were identified in the following
species: an 83-kDa subtilisin-like proteinase, a 62-kDa glycosyl hydrolase, a 47.5-kDa glucan 1,3-β-glucosidase precursor,
a 30-kDa chitinase, and a 25-kDa thaumatin-like protein were identified in J. communis; a 30-kDa chitinase, a 25-kDa thaumatin-like protein, and a 32.5-kDa glucanase-like protein were identified in J. oxycedrus; an 83-kDa subtilisin-like proteinase, a 62-kDa β-d-glucan exohydrolase, a 47.5-kDa glucan 1,3-β-glucosidase, and two 25-kDa thaumatin-like proteins were identified in C. lawsoniana, and a 25-kDa chitinase was identified in W. mirabilis. Based on protein identifications, there is strong evidence that the pollination drop functions in both pathogen defense
and pollen development. The discovery of similarities in terms of peptide sequence and protein identifications indicates that
ovular secretions are functionally conservative, and that they are essential to reproductive success. 相似文献
627.
Deng-Fu Guo Huxing Cui Qihong Zhang Donald A. Morgan Daniel R. Thedens Darryl Nishimura Justin L. Grobe Val C. Sheffield Kamal Rahmouni 《PLoS genetics》2016,12(2)
Bardet-Biedl syndrome (BBS) is a highly pleiotropic autosomal recessive disorder associated with a wide range of phenotypes including obesity. However, the underlying mechanism remains unclear. Here, we show that neuronal BBSome is a critical determinant of energy balance through its role in the regulation of the trafficking of the long signaling form of the leptin receptor (LRb). Targeted disruption of the BBSome by deleting the Bbs1 gene from the nervous system causes obesity in mice, and this phenotype is reproduced by ablation of the Bbs1 gene selectively in the LRb-expressing cells, but not from adipocytes. Obesity developed as a consequence of both increased food intake and decreased energy expenditure in mice lacking the Bbs1 gene in LRb-expressing cells. Strikingly, the well-known role of BBS proteins in the regulation of ciliary formation and function is unlikely to account for the obesogenic effect of BBS1 loss as disruption of the intraflagellar transport (IFT) machinery required for ciliogenesis by deleting the Ift88 gene in LRb-expressing cells caused a marginal increase in body weight and adiposity. Instead, we demonstrate that silencing BBS proteins, but not IFT88, impair the trafficking of the LRb to the plasma membrane leading to central leptin resistance in a manner independent of obesity. Our data also demonstrate that postnatal deletion of the Bbs1 gene in the mediobasal hypothalamus can cause obesity in mice, arguing against an early neurodevelopmental origin of obesity in BBS. Our results depict a novel mechanism underlying energy imbalance and obesity in BBS with potential implications in common forms of human obesity. 相似文献
628.
Objectives:The purpose of the current study was to firstly examine the effects of different whole-body vibration (WBV) frequencies in the lower-body muscles when applied simultaneously during a bridge exercise. Secondly, determine if there were any sex differences in the lower-body muscles of WBV during the bridge.Methods:Seven females and 7 males completed 2 familiarization and 1 test sessions. In the test session participants were randomized to complete one 30 s bout of a bridge exercise for 3 separate condition s followed by 3-min of rest. The 3 conditions (a) No-WBV (without WBV); (b) WBV-30 (30 Hz, low amplitude); (c) WBV-50 (50 Hz, low amplitude) were performed on a WBV platform. Muscle activity of the biceps femoris (BF), semitendinosus (ST), gluteus maximus (Gmax), multifidus muscle (MF) muscles were measured.Results:Muscle activity was increased with WBV in the BF and ST muscles at WBV-30 and WBV-50 conditions (p<0.05) vs. no-WBV. During No-WBV and WBV-50 conditions, males had a higher biceps femoris activity compared to females for (p<0.05) 45 and 27 %, respectively; however, during all conditions females had a high level of Gmax activity (57%) than males (p<0.05).Conclusion:Additional vibration at 30 and 50 Hz during the bridge exercise could be a useful method to enhance hamstring muscle activity. 相似文献
629.
Darryl L. Daley Jerry S. Vande Berg 《Biochimica et Biophysica Acta (BBA)/General Subjects》1976,437(1):211-220
Cyclic AMP and its dibutyryl derivative inhibit neuronal firing of the labellar sugar sensitive receptor of the blowfly when applied in conjunction with the stimulant sucrose. Furthermore, simultaneous application of aminophylline (phosphodiesterase inhibitor) and sucrose or in combination with cyclic AMP caused a similar depression of the sugar receptors response. In contrast, dibutyryl cyclic GMP elicited an increase in sugar receptor firing when applied with sucrose to the sugar receptor. Either 5′-AMP or 5′-GMP in combination with sucrose had no discernable effect on the sugar receptors response. Different ratio combinations of cyclic AMP and dibutyryl cyclic GMP showed the striking inhibitory effect of cyclic AMP upon the dibutyryl cyclic GMP elicited increases in receptor firing frequency. Therefore, it is suggested that these two nucleotides may be mediating different but complimentary aspects of sugar receptor function in a push-pull manner. 相似文献
630.
Darryl G. Stout 《Cryobiology》1981,18(5):521-527
A method for calculating the contraction strain (or the converse stress) to protoplasts of frozen multicellular plant tissues is described. The method requires (i) a nuclear magnetic resonance (NMR) measure of the quantity of bound water per gram dry weight (K), (ii) a gravimetric measure of grams of H2O per gram dry weight (L0), (iii) a measure of solute concentration in non-frozen cells (C0), (iv) an estimate of the specific volume of tissue dry matter (0.625 ml/g), (v) an NMR measure of the fraction of tissue water that is intracellular osmotic water (Pa), and (vi) a measure of the fraction of the dry weight that is cell wall (fcw). This method is a refinement of previous methods that calculate cell contraction strain from four (L0, K, C0, and 0.625) of the above six measurements. Comparison of the calculated protoplast strain to the calculated cell strain indicates that the two measures are quite similar, however, the measure of protoplast strain is, in theory, a more appropriate measure of the freezing strain. It is also demonstrated that derivation of a measure of strain from the parameters controlling it is useful, because it allows one to evaluate the relative contribution of each parameter in preventing the development of strain. 相似文献