全文获取类型
收费全文 | 512篇 |
免费 | 29篇 |
出版年
2023年 | 7篇 |
2022年 | 36篇 |
2021年 | 28篇 |
2020年 | 10篇 |
2019年 | 22篇 |
2018年 | 15篇 |
2017年 | 18篇 |
2016年 | 20篇 |
2015年 | 24篇 |
2014年 | 34篇 |
2013年 | 37篇 |
2012年 | 40篇 |
2011年 | 35篇 |
2010年 | 19篇 |
2009年 | 12篇 |
2008年 | 30篇 |
2007年 | 22篇 |
2006年 | 16篇 |
2005年 | 14篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 3篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有541条查询结果,搜索用时 187 毫秒
61.
Sarah O. Makled Amira M. Hamdan Abdel-Fattah M. El-Sayed 《Probiotics and antimicrobial proteins》2020,12(2):365-374
A 50-day feeding trial was conducted to evaluate the effects of dietary supplementation of a novel marine psychrotrophic bacterium, Psychrobacter maritimus 相似文献
62.
Nava R. Shochet Amira Rudi Yoel Kashman Yaacov Hod M. Raafat El-Maghrabi Ilan Spector 《Journal of cellular physiology》1993,157(3):481-492
Six novel alkaloids that contain a fused tetracyclic pyrido[2,3,4-kl]acridine ring system were purified recently from the Red Sea purple tunicate Eudistoma sp. Evaluation of the effects of these alkaloids on cultured neuroblastoma and fibroblast cells revealed that they possess potent growth regulatory properties, and affect cell shape and adhesion. In mouse neuroblastoma cells, the Eudistoma alkaloids inhibited cell proliferation and induced a process of differentiation during which the cels flattened onto the surface, increased considerably in size, and extended long neurites. In hamster fibroblasts the alkaloids slowed down cell multiplication, and caused an exceptional cell flattening or elongation. In a virustransformed derivative of the hamster fibroblasts the alkaloids restored many aspects of normal cell growth and morphology. In addition, several of the alkaloids mimicked the effects of cAMP analogs on two well-characterized cAMP-mediated processes involved in hepatic glucose metabolism–inhibition of pyruvate kinase (PK) activity and induction of mRNA for phosphoenolpyruvate carboxykinase (PEPCK). All these effects suggest that the Eudistoma alkaloids may act on the cAMP signaling system. However, a single application of these compounds was sufficient to completely block cell multiplication and to induce and sustain differentiation and “reverse transformation”. Furthermore, these effects were not readily reversible following removal of the drugs. In contrast, a single application of agents that mimic or elevate cAMP induced a transient response that waned with time in culture, and the effects induced by constant elevation of cAMP reverse rapidly following drug removal. We propose that the Eudistoma alkaloids cause growth inhibition, differentiation, and reverse transformation by modifying the activity state of proteins that are involved in the regulation of cell shape and adhesion and serve as a target for the cAMP and/or other second messenger systems. © 1993 Wiley-Liss, Inc. 相似文献
63.
64.
E. S. H. El Ashry N. Rashed A. Abdel-Rahman L. F. Awad H. A. Rasheed 《Nucleosides, nucleotides & nucleic acids》2013,32(8):925-939
Alkylation of 2-methylthiopyrimidin-4(1H)-one (1a) and its 5(6)-alkyl derivatives 1b–d as well as theophylline (7) with 2,2-bis(bromomethyl)-1,3-diacetoxypropane (2) under microwave irradia-tion gave the corresponding acyclonucleosides 1-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]-2-methyl-thio pyrmidin-4(1H)-ones 3a–d and 7-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]theophylline (8), which upon further irradiation gave the double-headed acyclonucleosides 1,1 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis[(2-(methylthio)-pyrimidin-4(1H)-ones] 4a–c, and 7,7 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis(theophylline) (9). The deacetylated derivatives were obtained by the action of sodium methoxide. The activity of deacetylated nucleosides against Hepatitis B virus was evaluated. Compound 5b showed moderate inhibition activity against HBV with mild cytotoxicity. 相似文献
65.
Pharmacokinetic evaluation of daclatasvir and ledipasvir in healthy volunteers using a validated highly sensitive spectrofluorimetric method
下载免费PDF全文
![点击此处可从《Luminescence》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A simple, highly sensitive and selective spectrofluorimetric method has been developed and fully validated for the determination of daclatasvir (DAC) and ledipasvir (LED) in tablets and human plasma. The method is based on measurement of the native fluorescence in methanol at λem 384 nm after excitation at λex 318 nm for DAC and in acetonitrile at λem 402 nm after excitation at λex 340 nm for LED. The fluorescence intensity (FI) concentration plot was rectilinear over the ranges 1.2–12, 0.1–18 ng ml?1 and 9–90, 1–100 ng ml?1 with a good correlation of r = 0.9994 to r = 0.9997 in standard solution and human plasma for DAC and LED, respectively. The extraction of analytes from plasma was performed using methanol and acetonitrile as a precipitating agent with lower limit of quantification (LLOQ) of 0.1 and 1.0 ng ml?1 for DAC and LED; respectively. The proposed method was validated according to the US Food and Drug Administration (FDA) guidelines and successfully applied for estimating the pharmacokinetic parameters of DAC and LED following oral administrations of their tablets. 相似文献
66.
Roberto Mattioli Marco Biancucci Amira El Shall Luciana Mosca Paolo Costantino Dietmar Funck Maurizio Trovato 《BMC plant biology》2018,18(1):356
Background
In many plants, the amino acid proline is strongly accumulated in pollen and disruption of proline synthesis caused abortion of microspore development in Arabidopsis. So far, it was unclear whether local biosynthesis or transport of proline determines the success of fertile pollen development.Results
We analyzed the expression pattern of the proline biosynthetic genes PYRROLINE-5-CARBOXYLATE SYNTHETASE 1 & 2 (P5CS1 & 2) in Arabidopsis anthers and both isoforms were strongly expressed in developing microspores and pollen grains but only inconsistently in surrounding sporophytic tissues. We introduced in a p5cs1/p5cs1 p5cs2/P5CS2 mutant background an additional copy of P5CS2 under the control of the Cauliflower Mosaic Virus (CaMV) 35S promoter, the tapetum-specific LIPID TRANSFER PROTEIN 12 (Ltp12) promoter or the pollen-specific At5g17340 promoter to determine in which site proline biosynthesis can restore the fertility of proline-deficient microspores. The specificity of these promoters was confirmed by β-glucuronidase (GUS) analysis, and by direct proline measurement in pollen grains and stage-9/10 anthers. Expression of P5CS2 under control of the At5g17340 promoter fully rescued proline content and normal morphology and fertility of mutant pollen. In contrast, expression of P5CS2 driven by either the Ltp12 or CaMV35S promoter caused only partial restoration of pollen development with little effect on pollen fertility.Conclusions
Overall, our results indicate that proline transport is not able to fulfill the demand of the cells of the male germ line. Pollen development and fertility depend on local proline biosynthesis during late stages of microspore development and in mature pollen grains.67.
Hesham Saeed Hadeer Soudan Amany El-Sharkawy Aida Farag Amira Embaby Farid Ataya 《The protein journal》2018,37(5):461-471
Recombinant l.asparaginase, L.ASNase, from Pseudomonas aeruginosa was purified using nickel affinity chromatography. The affinity purified L.ASNase exhibited a protein band with a molecular weight of 72.4 kDa on a native polyacrylamide gel and 36.276 kDa using SDS–PAGE. The activity of the purified L.ASNase was enhanced by Mg2+ and inhibited by Zn2+ at a concentration of 5 mM. The specificity of the recombinant L.ASNase towards different substrates was examined, and it was found that the enzyme showed the highest activity towards l.asparagine. Moreover, the enzyme showed lower activity towards other substrates such as L.glutamine, urea and acrylamide. The in vitro hemolysis assay revealed that the purified L.ASNase did not show hemolysis effect on blood erythrocytes. Serum and trypsin half-life of L.ASNase suggested that the recombinant L.ASNase retained 50% of its initial activity after 90 and 60 min incubation period in serum and trypsin separately. 相似文献
68.
Inhibition of yeast alcohol dehydrogenase by alkylating agents 总被引:2,自引:0,他引:2
69.
Romano Ngui Noor Amira Abdul Halim Yamuna Rajoo Yvonne AL Lim Stephen Ambu Komalaveni Rajoo Tey Siew Chang Lu Chan Woon Rohela Mahmud 《The Korean journal of parasitology》2016,54(5):673-678
Epidemiological study on strongyloidiasis in humans is currently lacking in Malaysia. Thus, a cross-sectional study was carried out to determine the prevalence of Strongyloides stercoralis infection among the inhabitants of longhouse indigenous communities in Sarawak. A single stool and blood sample were collected from each participant and subjected to microscopy, serological and molecular techniques. Five species of intestinal parasites were identified by stool microscopy. None of the stool samples were positive for S. stercoralis. However, 11% of 236 serum samples were seropositive for strongyloidiasis. Further confirmation using molecular technique on stool samples of the seropositive individuals successfully amplified 5 samples, suggesting current active infections. The prevalence was significantly higher in adult males and tended to increase with age. S. stercoralis should no longer be neglected in any intestinal parasitic survey. Combination of more than 1 diagnostic technique is necessary to increase the likelihood of estimating the ‘true’ prevalence of S. stercoralis. 相似文献
70.
Genetic and Functional Analysis of Polymorphisms in the Human Dopamine Receptor and Transporter Genes in Small Cell Lung Cancer
下载免费PDF全文
![点击此处可从《Journal of cellular physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)