全文获取类型
收费全文 | 623篇 |
免费 | 37篇 |
专业分类
660篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 36篇 |
2014年 | 26篇 |
2013年 | 40篇 |
2012年 | 53篇 |
2011年 | 45篇 |
2010年 | 34篇 |
2009年 | 27篇 |
2008年 | 38篇 |
2007年 | 51篇 |
2006年 | 39篇 |
2005年 | 37篇 |
2004年 | 28篇 |
2003年 | 30篇 |
2002年 | 27篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1940年 | 1篇 |
1939年 | 6篇 |
1938年 | 10篇 |
排序方式: 共有660条查询结果,搜索用时 0 毫秒
91.
Chemo-enzymatic preparation of resveratrol derivatives 总被引:1,自引:0,他引:1
Giovanni Nicolosi Carmela Spatafora Corrado Tringali 《Journal of Molecular Catalysis .B, Enzymatic》2002,16(5-6):223-229
Regioselective derivatisation of resveratrol (1) at positions 3, 5 or 4′ was achieved by a chemo-enzymatic procedure based on standard chemical reactions and esterification or alcoholysis in organic solvents catalysed by the commercially available Pseudomonas cepacia (PcL) and Candida antarctica (CaL) lipases. 相似文献
92.
Status of the search for a major genetic locus for affective disorder in the Old Order Amish 总被引:2,自引:0,他引:2
Andrew J. Pakstis Judith R. Kidd Carmela M. Castiglione Kenneth K. Kidd 《Human genetics》1991,87(4):475-483
Summary We have resumed the search for an autosomal linkage with affective disorder in the Old Order Amish and report the pairwise linkage results after screening 185 marked loci. No positive evidence of genetic linkage was found, and we estimate that roughly 23% of the autosomal genome has been excluded from linkage. 相似文献
93.
94.
Long-Term Evolution of the Hypervariable Region of Hepatitis C Virus in a Common-Source-Infected Cohort 总被引:9,自引:2,他引:7 下载免费PDF全文
Jane McAllister Carmela Casino Fiona Davidson Joan Power Emer Lawlor Peng Lee Yap Peter Simmonds Donald B. Smith 《Journal of virology》1998,72(6):4893-4905
The long-term evolution of the hepatitis C virus hypervariable region (HVR) and flanking regions of the E1 and E2 envelope proteins have been studied in a cohort of women infected from a common source of anti-D immunoglobulin. Whereas virus sequences in the infectious source were relatively homogeneous, distinct HVR variants were observed in each anti-D recipient, indicating that this region can evolve in multiple directions from the same point. Where HVR variants with dissimilar sequences were present in a single individual, the frequency of synonymous substitution in the flanking regions suggested that the lineages diverged more than a decade previously. Even where a single major HVR variant was present in an infected individual, this lineage was usually several years old. Multiple lineages can therefore coexist during long periods of chronic infection without replacement. The characteristics of amino acid substitution in the HVR were not consistent with the random accumulation of mutations and imply that amino acid replacement in the HVR was strongly constrained. Another variable region of E2 centered on codon 60 shows similar constraints, while HVR2 was relatively unconstrained. Several of these features are difficult to explain if a neutralizing immune response against the HVR is the only selective force operating on E2. The impact of PCR artifacts such as nucleotide misincorporation and the shuffling of dissimilar templates is discussed. 相似文献
95.
Riassunto Gli AA riportano i dati morfologici, biochimici e colturali rilevati su 3 sottocolture di un ceppo diGlenosporella peralbida
Castellani 1964. I risultati ottenuti concordano con quell descritti dallo stessoCastellani (1964).
The Authors have investigated three cultures ofGlenosporella peralbida received fromCastellani. The date obtained by the Authors do not differ those reported byCastellani (1964).相似文献
96.
Nerve Growth factor regulation of cyclin D1 in PC12 cells through a p21RAS extracellular signal-regulated kinase pathway requires cooperative interactions between Sp1 and nuclear factor-kappaB 下载免费PDF全文
97.
Colabufo NA Abate C Contino M Inglese C Ferorelli S Berardi F Perrone R 《Bioorganic & medicinal chemistry letters》2008,18(6):2183-2187
A potent sigma-2 receptor ligand, known as PB28, was tritium radiolabelled and biologically evaluated. The results showed that [(3)H]PB28 and the corresponding unlabelled PB28 had superimposed pharmacodynamic properties. This radioligand appears as a potential candidate for receptor binding and in living cells assays. 相似文献
98.
Urbani P Cascio MG Ramunno A Bisogno T Saturnino C Di Marzo V 《Bioorganic & medicinal chemistry》2008,16(15):7510-7515
In the present study, 11 novel N-(3,3-diphenyl)propyl-2,2-diphenylacetamide derivatives (4a-d and 9a-g) and six triphenylacetamides (10a-c and 11a-c) were synthesized and tested as ligands of cannabinoid CB(1) and CB(2) receptors. All compounds exhibited affinity for CB(1) and CB(2) receptors. Four compounds (4b, 9a, 9b, and 11a) showed selectivity for CB(1) versus CB(2) receptors, although only the N-(3,3-diphenyl)propyl-2,2-diphenylacetamide (4b) can be considered a potent CB(1) ligand (K(i)=58 nM). It was 140-fold selective over CB(2) receptors (K(i)=7800 nM) and behaved as an inverse agonist by stimulating forskolin-induced cAMP formation in mouse N18TG2 neuroblastoma cells. This compound is the first of a novel class of tetraphenyl CB(1) ligands that, in view of its easy synthesis and high affinity for CB(1) receptors and despite its sterical hindrance, will be useful for the design of new blockers of this therapeutically exploitable receptor type. 相似文献
99.
Patrizio Dimitri Ruggiero Caizzi Ennio Giordano Maria Carmela Accardo Giovanna Lattanzi Giuseppe Biamonti 《Chromosoma》2009,118(4):419-435
The organization of chromosomes into euchromatin and heterochromatin is amongst the most important and enigmatic aspects of
genome evolution. Constitutive heterochromatin is a basic yet still poorly understood component of eukaryotic chromosomes,
and its molecular characterization by means of standard genomic approaches is intrinsically difficult. Although recent evidence
indicates that the presence of transcribed genes in constitutive heterochromatin is a conserved trait that accompanies the
evolution of eukaryotic genomes, the term heterochromatin is still considered by many as synonymous of gene silencing. In
this paper, we comprehensively review data that provide a clearer picture of transcribed sequences within constitutive heterochromatin,
with a special emphasis on Drosophila and humans. 相似文献
100.
Paolo Galloni Vanni Lopresto Marta Parazzini Rosanna Pinto Marta Piscitelli Paolo Ravazzani Carmela Marino 《Bioelectromagnetics》2009,30(5):385-392
UMTS communication devices are becoming common in everyday use. This could raise public concern about their possible detrimental effects on human health. The aim of this study, in the framework of the EMF nEAR Project, was to evaluate possible influence of UMTS electromagnetic fields (EMF) exposure on cochlear outer hair cells' (OHCs) functionality in laboratory animals. Forty‐eight male Sprague–Dawley rats were locally exposed (right ear) or sham‐exposed to a controlled UMTS EMF, frequency of 1946 MHz, at SAR level of 10 W/kg, 2 h a day, 5 days a week, for 4 weeks. A group of 12 rats treated with kanamycin (KM) was also included as positive control. Rats were tested by recording Distortion Product Otaoacoustic Emissions (DPOAEs), a non‐invasive test capable of assessing the status of the OHCs in the inner ear. DPOAEs were performed before, during (one or three times a week) and after (1‐week) exposure to the EMF. The analysis of the data shows that no statistically significant differences were found between the audiological signals recorded from the different experimental groups. The ototoxic effect of KM has been confirmed. Bioelectromagnetics 30:385–392, 2009. © 2009 Wiley‐Liss, Inc. 相似文献