全文获取类型
收费全文 | 270篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
280篇 |
出版年
2023年 | 1篇 |
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 25篇 |
2012年 | 24篇 |
2011年 | 17篇 |
2010年 | 19篇 |
2009年 | 12篇 |
2008年 | 20篇 |
2007年 | 18篇 |
2006年 | 10篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有280条查询结果,搜索用时 0 毫秒
11.
Dergilev KV Rubina KA Tsokolaeva ZI Sysoeva VIu Gmyzina AI Kalinina NI Beliavskaia TM Akchurin RS Parfenova EV Tkachuk VA 《Tsitologiia》2010,52(11):921-930
In the past few years it has been established that the heart contains a reservoir of stem and progenitor cells that have the ability to differentiate in vitro and in vivo toward vascular and cardiac lineages and that show cardiac regeneration potential in vivo following injection into the infracted myocardium. The aim of the present study was to characterize cardiac stem cells in the tissue of chronic left ventricular aneurism. It was shown that human c-kit positive cells were scattered in fibrous, muscle and adipose parts of aneurism tissue. C-kit positive cells localized mainly in fibrous tissue nearby large vessels, however, c-kit positive cells did not express endothelial, smooth muscle or cardiomyocyte cell markers. Co-localization experiments demonstrated that all c-kit positive cells were of non-hematopoietic origin, since they did not express markers such as CD34 and CD45. Majority of c-kit positive cells expressed MDR1, but showed no proliferation activity (Ki67). It thus appears that aneurism tissue could be an alternative source of autologous cardiac stem cells. However, their regeneration capacity should be further explored. 相似文献
12.
Hafsa Athar Jafree Muhammad Imtiaz Syed Inayatullah Fozia Hanif Khan Tajuddin Nizami 《PloS one》2014,9(2)
This paper presents new simple approaches for evaluating determinant and inverse of a matrix. The choice of pivot selection has been kept arbitrary thus they reduce the error while solving an ill conditioned system. Computation of determinant of a matrix has been made more efficient by saving unnecessary data storage and also by reducing the order of the matrix at each iteration, while dictionary notation [1] has been incorporated for computing the matrix inverse thereby saving unnecessary calculations. These algorithms are highly class room oriented, easy to use and implemented by students. By taking the advantage of flexibility in pivot selection, one may easily avoid development of the fractions by most. Unlike the matrix inversion method [2] and [3], the presented algorithms obviate the use of permutations and inverse permutations. 相似文献
13.
Moretto MM Weiss LM Combe CL Khan IA 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(4):2485-2492
The importance of intraepithelial lymphocytes (IEL) in immunoprotection against orally acquired pathogens is being increasingly recognized. Recent studies have demonstrated that Ag-specific IEL can be generated and can provide an important first line of defense against pathogens acquired via oral route. However, the mechanism involved in priming of IEL remains elusive. Our current study, using a microsporidial model of infection, demonstrates that priming of IEL is dependent on IFN-gamma-producing dendritic cells (DC) from mucosal sites. DC from mice lacking the IFN-gamma gene are unable to prime IEL, resulting in failure of these cells to proliferate and lyse pathogen-infected targets. Also, treatment of wild-type DC from Peyer's patches with Ab to IFN-gamma abrogates their ability to prime an IEL response against Encephalitozoon cuniculi in vitro. Moreover, when incubated with activated DC from IFN-gamma knockout mice, splenic CD8(+) T cells are not primed efficiently and exhibit reduced ability to home to the gut compartment. These data strongly suggest that IFN-gamma-producing DC from mucosal sites play an important role in the generation of an Ag-specific IEL response in the small intestine. To our knowledge, this report is the first demonstrating a role for IFN-gamma-producing DC from Peyer's patches in the development of Ag-specific IEL population and their trafficking to the gut epithelium. 相似文献
14.
15.
Leuck M Glare R Zien N Paul M Wolter A 《Nucleosides, nucleotides & nucleic acids》2005,24(5-7):989-992
The synthesis of a novel amino-ON CPG support and its application in the synthesis of 3'-aminoalkylated oligonucleotides is reported. The release of oligonucleotides with free 3'-amino groups is accomplished by treatment with concentrated ammonia for 2 h at 55 degrees C. 相似文献
16.
A low molecular weight acid phosphatase was purified to homogeneity from chicken heart with a specific activity of 42 U/mg
and a recovery of about 1%. Nearly 800 fold purification was achieved. The molecular weight was estimated to be 18 kDa by
SDS-polyacrylamide gel electrophoresis. Para-nitrophenyl phosphate, phenyl phosphate and flavin mononucleotide were efficiently hydrolysed by the enzyme and found to
be good substrates. Fluoride and tartrate had no inhibitory effect while phosphate, vanadate and molybdate strongly inhibited
the enzyme. The acid phosphatase was stimulated in the presence of glycerol, ethylene glycol, methanol, ethanol and acetone,
which reflected the phosphotransferase activity. When phosphate acceptors such as ethylene glycol concentrations were increased,
the ratio of phosphate transfer to hydrolysis was also increased, demonstrating the presence of a transphosphorylation reaction
where an acceptor can compete with water in the rate limiting step involving hydrolysis of a covalent phospho enzyme intermediate.
Partition experiments carried out with two substrates, para-nitrophenyl phosphate and phenyl phosphate, revealed a constant product ratio of 1.7 for phosphotransfer to ethylene glycol
versus hydrolysis, strongly supporting the existence of common covalent phospho enzyme intermediate. A constant ratio of K
cat/K
m, 4.3×104, found at different ethylene glycol concentrations, also supported the idea that the rate limiting step was the hydrolysis
of the phospho enzyme intermediate. 相似文献
17.
Hosaka K Rayner SE von der Weid PY Zhao J Imtiaz MS van Helden DF 《American journal of physiology. Heart and circulatory physiology》2006,290(2):H813-H822
The effects of calcitonin gene-related peptide (CGRP) on constriction frequency, smooth muscle membrane potential (V(m)), and endothelial V(m) of guinea pig mesenteric lymphatics were examined in vitro. CGRP (1-100 nM) caused an endothelium-dependent decrease in the constriction frequency of perfused lymphatic vessels. The endothelium-dependent CGRP response was abolished by the CGRP-1 receptor antagonist CGRP-(8-37) (1 microM) and pertussis toxin (100 ng/ml). This action of CGRP was also blocked by the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine (L-NNA; 10 microM), an action that was reversed by the addition of L-arginine (100 microM). cGMP, adenylate cyclase, cAMP-dependent protein kinase (PKA), and ATP-sensitive K+ (K+(ATP)) channels were all implicated in the endothelium-dependent CGRP response because it was abolished by methylene blue (20 microM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 microM), dideoxyadenosine (10 microM), N-[2-(p-bromociannamylamino)-ethyl]-5-isoquinolinesulfonamide-dichloride (H89; 1 microM) and glibenclamide (10 microM). CGRP (100 nM), unlike acetylcholine, did not alter endothelial intracellular Ca2+ concentration or V(m). CGRP (100 nM) hyperpolarized the smooth muscle V(m), an effect inhibited by L-NNA, H89, or glibenclamide. CGRP (500 nM) also caused a decrease in constriction frequency. However, this was no longer blocked by CGRP-(8-37). CGRP (500 nM) also caused smooth muscle hyperpolarization, an action that was now not blocked by L-NNA (100 microM). It was most likely mediated by the activation of the cAMP/PKA pathway and the opening of K+(ATP) channels because it was abolished by H89 or glibenclamide. We conclude that CGRP, at low to moderate concentrations (i.e., 1-100 nM), decreases lymphatic constriction frequency primarily by the stimulation of CGRP-1 receptors coupled to pertussis toxin-sensitive G proteins and the release of NO from the endothelium or enhancement of the actions of endogenous NO. At high concentrations (i.e., 500 nM), CGRP also directly activates the smooth muscle independent of NO. Both mechanisms of activation ultimately cause the PKA-mediated opening of K+(ATP) channels and resultant hyperpolarization. 相似文献
18.
19.
Gemechu Keneni Endashaw Bekele Muhammad Imtiaz Kifle Dagne Emana Getu Fassil Assefa 《Plant Molecular Biology Reporter》2012,30(3):654-665
Genetic diversity and population structure were studied in 155 chickpea (Cicer arietinum L.) entries using 33 polymorphic microsatellite (SSR) markers. Molecular analysis of variance showed variations of 73% within and 27% among populations. Introduced genotypes exhibited highest polymorphism (70.27%) than the landraces (36?C57%). Collections from Shewa, Harerge, W. Gojam and S. Gonder regions also showed higher polymorphism (50?C57%) than the rest of the local accessions (36?C45%). Analyses of pairwise population Nei genetic distance and PhiPT coefficients, expected heterozygosity (He) and unbiased expected heterozygosity (UHe), Shannon??s information index (I) and percent polymorphism (% P) showed existence of high genetic variation between geographical regions. Accessions from adjoining geographical regions mostly showed more genetic similarities than those from origins far isolated apart. This could be associated with the ease and likelihood of inter-regional gene flow and seed movement particularly during times of drought. The 155 entries were grouped into five clusters following analysis of population structure. The first cluster (C1) constituted accessions from Arsi; the second (C2) from Gojam and Gonder; the third (C3) from Harerge and E. and N. Shewa; and the fourth (C4) from W. Shewa, Tigray, and Wello regions. The fifth cluster (C5) was entirely consisted of improved genotypes. Improved genotypes of both Kabuli and Desi types distinctly fell into cluster five (C5) regardless of their difference in seed types. The result has firmly established that introduction of genetic materials from exotic sources has broadened the genetic base of the national chickpea breeding program. Further implications of the findings as regards to chickpea germplasm management and its utilization in breeding program are also discussed. 相似文献
20.