全文获取类型
收费全文 | 190篇 |
免费 | 19篇 |
专业分类
209篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 9篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1913年 | 2篇 |
1912年 | 2篇 |
1909年 | 1篇 |
1906年 | 2篇 |
排序方式: 共有209条查询结果,搜索用时 0 毫秒
71.
In order to survey the behaviour of choosing the alley area instead of a cubicle as a lying place (cubicle refusal), a questionnaire was sent to the 273 dairy farms in Norway known to keep cows in cubicle housing systems. Sixty-six percent of the farmers contacted were included in the study. The median herd size was 18 cows (range 7–118). More than 85% of the herds had sheds providing one or more cubicles per cow. The mean herd occurrence of cubicle refusal was 6%, but showed great variation (range 0–55%). Regression analysis showed a significant association between rearing heifers in slatted floor pens and an increased cubicle refusal occurrence (p = 0.02, R2 = 0.05), while herd size, use of litter, or cubicle-to-animal ratio were not found to be associated with cubicle refusal. The practice of rearing heifers in slatted floor pens accounted for about one half of the observed cubicle refusal (etiologic fraction = 0.51). 相似文献
72.
NF-kappaB and IkappaB proteins have central roles in regulation of inflammation and innate immunity in mammals. Homologues of these proteins also play an important role in regulation of the Drosophila immune response. Here we present a molecular population genetic analysis of Relish, a Drosophila NF-kappaB/IkappaB protein, in Drosophila simulans and D. melanogaster. We find strong evidence for adaptive protein evolution in D. simulans, but not in D. melanogaster. The adaptive evolution appears to be restricted to the IkappaB domain. A possible explanation for these results is that Relish is a site of evolutionary conflict between flies and their microbial pathogens. 相似文献
73.
An overview of the serpin superfamily 总被引:1,自引:1,他引:1
Law RH Zhang Q McGowan S Buckle AM Silverman GA Wong W Rosado CJ Langendorf CG Pike RN Bird PI Whisstock JC 《Genome biology》2006,7(5):216-11
Serpins are a broadly distributed family of protease inhibitors that use a conformational change to inhibit target enzymes. They are central in controlling many important proteolytic cascades, including the mammalian coagulation pathways. Serpins are conformationally labile and many of the disease-linked mutations of serpins result in misfolding or in pathogenic, inactive polymers. 相似文献
74.
A. McGready A. Stevens M. Lipkin B. D. Hudson D. C. Whitley M. G. Ford 《Journal of molecular modeling》2009,15(5):489-498
Vicinity analysis (VA) is a new methodology developed to identify similarities between protein binding sites based on their three-dimensional structure and the chemical similarity of matching residues. The major objective is to enable searching of the Protein Data Bank (PDB) for similar sub-pockets, especially in proteins from different structural and biochemical series. Inspection of the ligands bound in these pockets should allow ligand functionality to be identified, thus suggesting novel monomers for use in library synthesis. VA has been developed initially using the ATP binding site in kinases, an important class of protein targets involved in cell signalling and growth regulation. This paper defines the VA procedure and describes matches to the phosphate binding sub-pocket of cyclin-dependent protein kinase 2 that were found by searching a small test database that has also been used to parameterise the methodology. 相似文献
75.
Tight junctions consist of many proteins, including transmembrane and associated cytoplasmic proteins, which act to provide a barrier regulating transport across epithelial and endothelial tissues. These junctions are dynamic structures that are able to maintain barrier function during tissue remodelling and rapidly alter it in response to extracellular signals. Individual components of tight junctions also show dynamic behaviour, including migration within the junction and exchange in and out of the junctions. In addition, it is becoming clear that some tight junction proteins undergo continuous endocytosis and recycling back to the plasma membrane. Regulation of endocytic trafficking of junctional proteins may provide a way of rapidly remodelling junctions and will be the focus of this chapter. 相似文献
76.
Few loci have been measured for DNA polymorphism and divergence in several species. Here we report such data from the protein-coding region of xanthine dehydrogenase (Xdh) in 22 species of Drosophila. Many of our samples were from closely related species, allowing us to confidently assign substitutions to individual lineages. Surprisingly, Xdh appears to be fixing more A/T mutations than G/C mutations in most lineages, leading to evolution of higher A/T content in the recent past. We found no compelling evidence for selection on protein variation, though some aspects of the data support the notion that a significant fraction of amino acid polymorphisms are slightly deleterious. Finally, we found no convincing evidence that levels of silent heterozygosity are associated with rates of protein evolution. 相似文献
77.
ABE production from corn: a recent economic evaluation 总被引:2,自引:0,他引:2
This article details an economic assessment of butanol production from corn using the newly developed hyper-butanol-producing
strain of Clostridium beijerinckii BA101. Butanol is produced in batch reactors and recovered by distillation. For a plant with 153,000 metric tons of acetone,
butanol, and ethanol (ABE) production capacity, the production equipment cost and total working capital cost is US$33.47×106 and US$110.46×106, respectively. Based on a corn price (C
p) of US$79.23 ton−1 (US$2.01 bushel−1), an ABE yield of 0.42 (g ABE/g glucose) butanol price is projected to be US$0.34 kg−1. An improved yield of 0.50 will reduce this price to US$0.29 kg−1. Assumptions, such as by-product credit for gases and complete conversion of corn steep liquor (CSL) to fermentation by-products,
have been taken into consideration. An increased price of corn to US$197.10 ton−1 would result in a butanol price of US$0.47 kg−1. A grass-rooted plant would result in a butanol price of US$0.73 kg−1 (C
p US$79.23 ton−1). In a worst case scenario, the price of butanol would increase to US$1.07 kg−1 (C
p 197.10 ton−1 for a grass-rooted plant and assuming no credit for gases). This is based on the assumption that corn price would not increase
to more than US$197.10 ton−1.
Journal of Industrial Microbiology & Biotechnology (2001) 27, 292–297.
Received 12 September 2000/ Accepted in revised form 12 January 2001 相似文献
78.
Brigitte Boxma Guenola Ricard Angela HAM van Hoek Edouard Severing Seung-Yeo Moon-van der Staay Georg WM van der Staay Theo A van Alen Rob M de Graaf Geert Cremers Michiel Kwantes Neil R McEwan C Jamie Newbold Jean-Pierre Jouany Tadeusz Michalowski Peter Pristas Martijn A Huynen Johannes HP Hackstein 《BMC evolutionary biology》2007,7(1):1-12
Background
The hydrogenosomes of the anaerobic ciliate Nyctotherus ovalis show how mitochondria can evolve into hydrogenosomes because they possess a mitochondrial genome and parts of an electron-transport chain on the one hand, and a hydrogenase on the other hand. The hydrogenase permits direct reoxidation of NADH because it consists of a [FeFe] hydrogenase module that is fused to two modules, which are homologous to the 24 kDa and the 51 kDa subunits of a mitochondrial complex I.Results
The [FeFe] hydrogenase belongs to a clade of hydrogenases that are different from well-known eukaryotic hydrogenases. The 24 kDa and the 51 kDa modules are most closely related to homologous modules that function in bacterial [NiFe] hydrogenases. Paralogous, mitochondrial 24 kDa and 51 kDa modules function in the mitochondrial complex I in N. ovalis. The different hydrogenase modules have been fused to form a polyprotein that is targeted into the hydrogenosome.Conclusion
The hydrogenase and their associated modules have most likely been acquired by independent lateral gene transfer from different sources. This scenario for a concerted lateral gene transfer is in agreement with the evolution of the hydrogenosome from a genuine ciliate mitochondrion by evolutionary tinkering. 相似文献79.
Michael Mauer Emily Glynn Einar Svarstad Camilla T?ndel Marie-Claire Gubler Michael West Alexey Sokolovskiy Chester Whitley Behzad Najafian 《PloS one》2014,9(11)
Background
Fabry disease. an X-linked deficiency of α-galactosidase A coded by the GLA gene, leads to intracellular globotriaosylceramide (GL-3) accumulation. Although less common than in males, chronic kidney disease, occurs in ∼15% of females. Recent studies highlight the importance of podocyte injury in Fabry nephropathy development and progression. We hypothesized that the greater the % of podocytes with active wild-type GLA gene (due to X-inactivation of the mutant copy) the less is the overall podocyte injury.Methods
Kidney biopsies from 12 treatment-naive females with Fabry disease, ages 15 (8–63), median [range], years were studied by electron microscopy and compared with 4 treatment-naive male patients.Results
In females, 51 (13–100)% of podocytes (PC) per glomerulus had no GL-3 inclusions, this consistent with a non-Fabry podocyte phenotype (NFPC). In PC with GL-3 inclusions [Fabry podocyte phenotype (FPC)], GL-3 volume density per podocyte was virtually identical in females and males, consistent with little or no cross-correction between FPC and NFPC. %NFPC per glomerulus (%NFPC/glom) correlated with age in females (r = 0.65, p = 0.02), suggesting a survival disadvantage for FPC over time. Age-adjusted %NFPC/glom was inversely related to foot process width (FPW) (r = −0.75, p = 0.007), an indicator of PC injury. GL-3 volume density in FPC in females correlated directly with FPW.Conclusions
These findings support important relationships between podocyte mosaicism and podocyte injury in female Fabry patients. Kidney biopsy, by providing information about podocyte mosaicism, may help to stratify females with Fabry disease for kidney disease risk and to guide treatment decisions. 相似文献80.
Confocal Raman imaging of biological materials offers the opportunity to extract chemical information on histologically defined regions and on sub-cellular organelles. This article reviews the technology and some successful applications. The chemical contrast from vibrational Raman spectroscopy is derived from the specific atomic motion of every molecule as detected by the Raman phenomenon. Examples show the successful identification of foreign material in pathological specimens, identification of lipid-type and calcium mineral-type in a mouse model of atherosclerosis, and component mapping in a pharmaceutical tablet. It is suggested that these methods can even be useful in studying metabolic disorders. 相似文献