全文获取类型
收费全文 | 553篇 |
免费 | 40篇 |
专业分类
593篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 35篇 |
2012年 | 38篇 |
2011年 | 35篇 |
2010年 | 25篇 |
2009年 | 22篇 |
2008年 | 56篇 |
2007年 | 47篇 |
2006年 | 30篇 |
2005年 | 50篇 |
2004年 | 46篇 |
2003年 | 44篇 |
2002年 | 33篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有593条查询结果,搜索用时 0 毫秒
81.
Neuronal interactions between neuropeptide W- and orexin- or melanin-concentrating hormone-containing neurons in the rat hypothalamus 总被引:1,自引:0,他引:1
Takenoya F Kitamura S Kageyama H Nonaka N Seki M Itabashi K Date Y Nakazato M Shioda S 《Regulatory peptides》2008,145(1-3):159-164
Neuropeptide W (NPW) was recently discovered as the endogenous ligand for GPR7 and GPR8, which are orphan G protein-coupled receptors isolated from the porcine brain. These receptors are assumed to be involved in feeding regulation and/or energy homeostasis. Recent anatomical studies have revealed that high levels of GPR7 mRNA are distributed in the brain, including the hypothalamus and amygdala. However immunohistochemical studies on the distribution and localization of NPW have revealed differing results concerning whether or not NPW-containing cell bodies and their processes are present in the hypothalamus. Only a few immunohistochemical reports have been published concerning the presence of NPW-containing neurons in the brains of rodents, while there have been no anatomical studies of the co-localization of this neuropeptide with other transmitters. On this basis, we used a specific antiserum against NPW to determine immunohistochemically the presence of NPW-containing neurons in the rat hypothalamus. Many NPW-like immunoreactive cell bodies and their processes could be detected in the caudal region of the lateral hypothalamus but not in its anterior or middle regions. Given this positive identification of NPW-containing neurons in the lateral hypothalamus, we further studied the nature of interaction between NPW-containing neurons and neurons containing feeding regulating peptides such as orexin- and melanin-concentrating hormone (MCH). Very close interactions between NPW-containing nerve processes and orexin- and MCH-containing neuronal cell bodies and processes could be observed. These morphological findings strongly suggest that NPW is involved in the regulation of feeding and/or sleep/arousal behavior through orexin- and/or MCH-mediated neuronal pathways. 相似文献
82.
Okumura T Nagai F Yamamoto S Hashimoto T Ito M Sawada H 《Bioscience, biotechnology, and biochemistry》2008,72(2):360-367
This report describes a new immunological method for the detection and quantification of Nitrospira populations using the reverse passive latex agglutination (RPLA). The numbers of the genus Nitrospira have been quantified only by molecular biological techniques such as FISH and quantitative PCR to date. Using high-density latex particles and a specific polyclonal antibody, Nitrospira populations in the wastewater treatment process were quantified in the shortest 4 h of incubation. The minimum detectable number of Nitrospira cells was 7.0x10(5) (log(10) 5.85) cells/ml. It is thought that the RPLA method can quantify Nitrospira populations more simply, economically, and speedily than molecular biological techniques or the culture method, because this procedure has a simple protocol and does not require the use of specialized equipment, expensive reagents, or technical skill. Therefore it is applicable for use in the everyday control and maintenance of water quality in wastewater treatment facilities where equipment is not sufficient or in the field. 相似文献
83.
84.
Ogishima T Mitani F Suematsu M 《The Journal of steroid biochemistry and molecular biology》2008,111(1-2):80-86
We have found cytochrome P-450(17alpha) in the islets of Langerhans of rat pancreas. Its existence coincided with that of insulin and demarcated those of glucagon and somatostatin, demonstrating the localization in beta-cells. The enzyme has not only 17alpha-hydroxylase activity but also lyase one, which is a prerequisite for androgen biosynthesis. The pancreatic microsomes converted progesterone mainly to androstenedione with a minor production of 17alpha-hydroxyprogesterone. Due to a low activity of the built-in lyase, cytochrome P-450(17alpha) requires a sufficient electron-transfer from P-450 reductase or presence of an activator to promote the C-C bond cleavage. In beta-cells, P-450 reductase was abundant and could efficiently transfer electrons to P-450(17alpha). Actually, inhibition with anti-P-450 reductase or limitation of NADPH preferentially reduced the lyase activity. Androstenedione was accumulated when its further metabolism was suppressed. We also found localization of cytochrome P-450scc and 3beta-hydroxysteroid dehydrogenase in beta-cells. These results indicate that the immediate substrate for androgen formation, progesterone, is intracellularly produced and is converted mainly to androstenedione with support by an efficient electron supply from P-450 reductase. The product was supposed to be further metabolized to the reduced derivatives such as testosterone, 5alpha-androstanedione, and dihydrotestosterone, which would act as local steroids in the islets of Langerhans. 相似文献
85.
Yoshida Y Sakai N Masuda H Furuichi M Nishikawa F Nishikawa S Mizuno H Waga I 《Analytical biochemistry》2008,375(2):217-222
Antibody-based detection systems are widely used, but in the cases of immunoprecipitations and enzyme-linked immunoassays, they can be laborious. These techniques require the preparation of at least two kinds of non-cross-reactive immunoglobulin Gs (IgGs), usually made from different species against the single target molecule. Aptamers composed of nucleic acids possess strict recognition ability for the target molecule's three-dimensional structure and, thus, are considered to act like IgG. In this study, experimental trials were designed to combine the advantages of IgG and aptamers. For this purpose, aptamers against rabbit IgG were identified by in vitro selection. One of the obtained aptamers had a dissociation constant lower than 15 pM to the rabbit IgG. It bound specifically to the constant region of the rabbit IgG, and no binding was observed with mouse or goat IgG. Moreover, this aptamer recognized only the native form of rabbit IgG and could not bind the sodium dodecyl sulfate (SDS)-denatured form. These features show the advantage of using the aptamer as a secondary probing agent rather than the usual secondary antibodies. 相似文献
86.
Hojo H Igawa K Ohba S Yano F Nakajima K Komiyama Y Ikeda T Lichtler AC Woo JT Yonezawa T Takato T Chung UI 《Biochemical and biophysical research communications》2008,376(2):375-379
To effectively treat osteoporosis and other bone-loss disorders, small compounds that potently induce bone formation are needed. The present study initially attempted to establish a monitoring system that could detect osteogenic differentiation easily, precisely, and noninvasively. For this purpose, we established pre-osteoblastic MC3T3E1 cells stably transfected with the GFP reporter gene driven by a 2.3 kb fragment of rat type I collagen promoter (Col1a1GFP-MC3T3E1). Among these cells, we selected a clone that fluoresced upon osteogenic stimulation by BMP2. The GFP fluorescence intensity corresponded well to the intensity of alkaline phosphatase (ALP) staining and to the level of osteocalcin (Oc) mRNA. Using this system, we screened natural and synthetic compound libraries and thus identified an isoflavone derivative, glabrisoflavone (GI). GI induced ALP staining and Oc mRNA in a dose-dependent manner. The Col1a1GFP-MC3T3E1 system may be useful for identifying novel osteogenic drugs. 相似文献
87.
Site-specific modification of functional groups in genomic hepatitis delta virus (HDV) ribozyme. 总被引:3,自引:0,他引:3
Fumiko Nishikawa Miho Shirai Satoshi Nishikawa 《European journal of biochemistry》2002,269(23):5792-5803
Human hepatitis delta (HDV) ribozyme is one of small ribozymes, such as hammerhead and hairpin ribozymes, etc. Its secondary structure shows pseudoknot structure composed of four stems (I to IV) and three single-stranded regions (SSrA, -B and -C). The 3D structure of 3'-cleaved product of genomic HDV ribozyme provided extensive information about tertiary hydrogen bonding interactions between nucleotide bases, phosphate oxygens and 2'OHs including new stem structure P1.1. To analyze the role of these hydrogen bond networks in the catalytic reaction, site-specific atomic-level modifications (such as deoxynucleotides, deoxyribosyl-2-aminopurine, deoxyribosylpurine, 7-deaza-ribonucleotide and inosine) were incorporated in the smallest trans-acting HDV ribozyme (47-mer). Kinetic analysis of these ribozyme variants demonstrated the importance of the two W-C base pairs of P1.1 for cleavage; in addition, the results suggest that all hydrogen bond interactions detected in the crystal structure involving 2'-OH and N7 atoms are present in the active ribozyme structure. In most of the variants, the relative reduction in kobs caused by substitution of the 2'-OH group correlated with the number of hydrogen bonds affected by the substitution. However G74 and C75 may have more than one hydrogen bond involving the 2'-OH in both the trans- and cis-acting HDV ribozyme. Moreover, in variants in which N7 was deleted, kobs was reduced 5- to 15-fold, it may suggest that N7 assists in coordinating Mg2+ ions or water molecules which bind with weak affinity in the active structure. 相似文献
88.
The effects of low concentrations of deoxynivalenol (DON) on structural and functional characteristics of human colonic adenocarcinoma
cell lines Caco-2 and T84 were examined. Scanning electron microscopic (SEM) analysis of the apical surfaces of Caco-2 cells
revealed reduction or abnormal formation of brush borders in the presence of 50, 100 and 200 ng/ml of DON. Monolayer integrity
of Caco-2 and T84 cells was studied using cells which were cultured on permeable membranes. The transepithelial electrical
resistance (TEER) of Caco-2 cells was significantly reduced at 50, 100 and 200 ng/ml of DON, significant increase in lucifer
yellow (LY) permeability was also observed in these cells at 100 ng/ml of DON. The TEER of T84 cells was significantly reduced
at 100 and 200 ng/ml of DON. LY permeability significantly increased at 200 ng/ml of DON in T84 cells. Enzyme activities in
Caco-2 cells were also examined. Alkaline phosphatase activity was reduced from the 6th to 15th day of culture in the presense
of 100 or 200 ng/ml of DON, whereas sucrase- isomaltase activity was significantly decreased by adding 50 or 100 ng/ml of
DON for 15 or 20 days. Protein content was attenuated only by treatment with 200 ng/ml of DON thoughout the experimental period.
The results indicate that DON interferes with structural and functional characteristics of differentiation in enterocytes
at low doses.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
89.
Efficient isolation of human parainfluenza viruses 1 and 3 using MNT‐1, a human malignant melanoma cell line system that exhibits an apparent cytopathic effect 下载免费PDF全文
Ko Sato Oshi Watanabe Suguru Ohmiya Fumiko Chiba Masahiro Hayashi Tamio Suzuki Kazuyoshi Kawakami Hidekazu Nishimura 《Microbiology and immunology》2016,60(11):801-805
Isolation of human parainfluenza virus (HPIV) serotypes 1 and 3 from clinical specimens is not very efficient because of the lack of a cell culture system capable of inducing CPE. In this study, the utility of a melanoma cell line, MNT‐1, that allows HPIV growth and displays CPE was demonstrated. In particularly, the efficiency of isolating HPIV1 and HPIV3 using MNT‐1 was greater than for cell lines conventionally used for HPIV isolation. Our demonstrated efficacy of HPIV1 and HPIV3 isolation with apparent CPE using the MNT‐1 cell culture system has the potential to improve virus isolation from clinical specimens. 相似文献
90.