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   131篇
  免费   7篇
  2023年   2篇
  2021年   4篇
  2019年   2篇
  2018年   4篇
  2017年   6篇
  2016年   8篇
  2015年   10篇
  2014年   5篇
  2013年   13篇
  2012年   14篇
  2011年   8篇
  2010年   4篇
  2009年   4篇
  2008年   5篇
  2007年   3篇
  2006年   2篇
  2005年   5篇
  2004年   1篇
  2003年   2篇
  2002年   3篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   3篇
  1994年   3篇
  1991年   1篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1981年   4篇
  1975年   1篇
  1972年   1篇
  1966年   1篇
排序方式: 共有138条查询结果,搜索用时 93 毫秒
41.

Background  

The accurate identification of Lactobacillus and other co-isolated bacteria during microbial ecological studies of ecosystems such as the human or animal intestinal tracts and food products is a hard task by phenotypic methods requiring additional tests such as protein and/or lipids profiling.  相似文献   
42.
The aim of this study is determining the different patterns of egg nests and the morphological differences between the specimens of Cicadatra persica Kirkalidy, 1909 (Hemiptera: Cicadidae) distributed in fruit orchards in Erneh located on AL-Sheikh mountain south west of Syria. The appearance of 80 egg nests was studied, and the results showed that there were two basic patterns of egg nests laid by Cicadatra persica, 90% of the egg nests were of the first pattern (consists of several adjacent slits), while 10% of them were of the second pattern (consists of several divergent slits). A random sample consisting of 300 specimens (150 males and 150 females) were also studied concentrating on the differences in the color of the supra-antennal plate and in the number of spurs on the tibia of the hind legs. The results showed that there were two basic patterns of individuals based on the differences in the color of supra-antennal plate. The first pattern (individuals with yellow supra-antennal plates), constituted more than 90%, and the second one (individuals with black supra-antennal plates) constituted less than 10%. The results also showed that there were 27 different patterns based on the number of spurs on the tibia of the hind legs. One of them was a common pattern (2, 3) whose individuals have 2 spurs on the upper side of the tibia of the hind legs and 3 spurs on the lateral side of the tibia of the hind legs. The total percent of this common pattern was 76%. The other 26 patterns were different from each other, and the total percent of all these different patterns was 24%.  相似文献   
43.
Reliable immunohistochemical detection of collagen in formalin fixed, paraffin embedded tissues requires protease digestion. While these pan-proteases (pepsin, trypsin, protease K, etc.) enhance collagen detection, they also digest many other tissue proteins and produce poor cellular morphology and unrecognizable cellular structures. Balancing the conditions (protease type, concentration, incubation time and temperature) to digest some, but not all, proteins in a tissue section while optimizing collagen detection requires one to compromise improved collagen immunolabeling with adequate cellular morphology. Furthermore, optimal conditions for digesting tissue proteins to enhance collagen detection vary among tissue types and their fixation. Although brain is not typically subject to these deleterious consequences, structures such as epithelium, spermatids, stroma etc. and other tissues with complicated histology are profoundly affected. To resolve this technical dilemma, we discovered a novel use for collagenase to enhance collagen immunodetection without affecting the noncollagen proteins, thereby preserving tissue morphology. Collagenase, which is typically used in vitro for disassociation of cells, has never been used reliably on formalin fixed, paraffin embedded tissue sections. This new use of collagenase for immunohistochemistry promotes increased collagen immunolabeling, is easy to use, is versatile, and allows preservation of tissue structure that provides maximal and accurate histological information.  相似文献   
44.
Aldawood AS  Sharaf MR 《ZooKeys》2011,(106):47-54
A new ant species, Monomorium dryhimi, is described based on workers from a single colony collected in Al Bahah, Asir Province, Saudi Arabia. This is the fourth species of the Monomorium monomorium-group collected from Arabian Peninsula, and appears to be closely related to Monomorium holothir Bolton, 1987, from Kenya. It can be distinguished by the following characters: head in profile with a weakly convex dorsal surface and a clearly convex ventral surface; eyes of moderate size with maximum diameter EL 0.19-0.25 × HW and with 6 ommatidia in the longest row; body colour yellow to light brownish yellow. In some individuals, head and gaster slightly but conspicuously darker than rest of body. Second halves of first and second gastral tergites with two characteristic brownish transverse bands. An identification key to the workers of the Arabian species of the Monomorium monomorium-group is presented. Scanning electron micrographs are given to illustrate the new species.  相似文献   
45.
Parkinson’s disease (PD) is characterized by the degeneration of dopaminergic neurons in the substantia nigra (SN) and the subsequent loss of striatal target innervation. Neuroinflammatory responses have been described for virtually all PD cases analysed. Microglia are the resident immune cells of the central nervous system and, thus, are the mediators of neuroinflammation. Approximately 12% of all central nervous system cells are microglia but the distribution and density of microglia differ within distinct brain regions. Interestingly, the SN has been shown to contain more microglia than adjacent structures. We have analysed changes in microglia numbers and in microglial morphology in the postnatal murine nigrostriatal system at various stages ranging from postnatal day 0 (P0) up to 24 months of age. We clearly show that the microglia numbers in the SN and in the striatum dramatically increase from P0 to P15 and significantly decrease in both areas in 18-month-old and 24-month-old animals. Moreover, microglia in the nigrostriatal system of aged mice show signs of dystrophy and degeneration, such as cytoplasmic inclusions, deramification of their processes and membrane blebbing. Our results support the hypothesis of microglial dystrophy during aging in the murine nigrostriatal system, accompanied by subsequent impairment of normal microglial functions. Microglial dysfunction during aging might be a potential risk factor for the development and/or progression of PD.  相似文献   
46.
The migration of mesencephalic dopaminergic (mDA) neurons from the subventricular zone to their final positions in the substantia nigra compacta (SNc), ventral tegmental area (VTA), and retrorubral field (RRF) is controlled by signalling from neurotrophic factors, cell adhesion molecules (CAMs) and extracellular matrix molecules (ECM). Reelin and the cytoplasmic adaptor protein Disabled-1 (Dab1) have been shown to play important roles in the migration and positioning of mDA neurons. Mice lacking Reelin and Dab1 both display phenotypes characterised by the failure of nigral mDA neurons to migrate properly. ApoER2 and VLDLr are receptors for Reelin signalling and are therefore part of the same signal transduction pathway as Dab1. Here we describe the roles of ApoER2 and VLDLr in the proper migration and positioning of mDA neurons in mice. Our results demonstrate that VLDLr- and ApoER2-mutant mice have both a reduction in and abnormal positioning of mDA neurons. This phenotype was more pronounced in VLDLr-mutant mice. Moreover, we provide evidence that ApoER2/VLDLr double-knockout mice show a phenotype comparable with the phenotypes observed for Reelin- and Dab1- mutant mice. Taken together, our results demonstrate that the Reelin receptors ApoER2 and VLDLr play essential roles in Reelin-mediated migration and positioning of mDA neurons.  相似文献   
47.
Atherosclerosis is the major cause of coronary artery disease (CAD), and oxidized LDL (oxLDL) is believed to play a key role in the initiation of the atherosclerotic process. Recent studies show that inflammation and autoimmune reactions are also relevant in atherosclerosis. In this study, we examined the association of antibodies against oxLDL (anti-oxLDL) with the severity of CAD in 558 Women's Ischemia Syndrome Evaluation (WISE) study samples (465 whites; 93 blacks) determined by coronary stenosis (< 20%, 20%-49%, > 50% stenosis). We also examined the relationship of anti-oxLDL with serum lipid levels and nine candidate genes including APOE, APOH, APOA5, LPL, LRP1, HL, CETP, PON1, and OLR1. IgM anti-oxLDL levels were significantly higher in the >20% stenosis group than in the ≥ 20% stenosis group in whites (0.69 ± 0.02 vs. 0.64 ± 0.01, respectively; P = 0.02). IgM anti-oxLDL levels correlated significantly with total cholesterol (r2 = 0.01; P = 0.03) and LDL cholesterol (r2 = 0.017; P = 0.004) in whites. Multiple regression analysis revealed a suggestive association of LPL/S447X single-nucleotide polymorphism (SNP) with both IgG anti-oxLDL (P = 0.02) and IgM anti-oxLDL (P = 0.07), as well as between IgM anti-oxLDL and the OLR1/3'UTR SNP (P = 0.020). Our data suggest that higher IgM anti-oxLDL levels may provide protection against coronary stenosis and that genetic variation in some candidate genes are determinants of anti-oxLDL levels.  相似文献   
48.
The seafloor is a unique environment, which allows insights into how geochemical processes affect the diversity of biological life. Among its diverse ecosystems are deep-sea brine pools - water bodies characterized by a unique combination of extreme conditions. The 'polyextremophiles' that constitute the microbial assemblage of these deep hot brines have not been comprehensively studied. We report a comparative taxonomic analysis of the prokaryotic communities of the sediments directly below the Red Sea brine pools, namely, Atlantis II, Discovery, Chain Deep, and an adjacent brine-influenced site. Analyses of sediment samples and high-throughput pyrosequencing of PCR-amplified environmental 16S ribosomal RNA genes (16S rDNA) revealed that one sulfur (S)-rich Atlantis II and one nitrogen (N)-rich Discovery Deep section contained distinct microbial populations that differed from those found in the other sediment samples examined. Proteobacteria, Actinobacteria, Cyanobacteria, Deferribacteres, and Euryarchaeota were the most abundant bacterial and archaeal phyla in both the S- and N-rich sections. Relative abundance-based hierarchical clustering of the 16S rDNA pyrotags assigned to major taxonomic groups allowed us to categorize the archaeal and bacterial communities into three major and distinct groups; group I was unique to the S-rich Atlantis II section (ATII-1), group II was characteristic for the N-rich Discovery sample (DD-1), and group III reflected the composition of the remaining sediments. Many of the groups detected in the S-rich Atlantis II section are likely to play a dominant role in the cycling of methane and sulfur due to their phylogenetic affiliations with bacteria and archaea involved in anaerobic methane oxidation and sulfate reduction.  相似文献   
49.
Tapinoma wilsonisp. n. is described and illustrated from Saudi Arabia based on the worker caste collected from Al Baha, Saudi Arabia. It closely resembles Tapinoma lugubre Santschi 1917, from Zimbabwe in body measurements but can be distinguished from the latter species by the yellowish brown color; the yellowish pubescence, the two pairs of hairs present on the anterior part of the head; and the distinctly concave anterior clypeal margin. Biological and ecological notes of the new species are presented. An identification key to the workers of the Arabian species of the genus Tapinoma is given.  相似文献   
50.
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