全文获取类型
收费全文 | 5136篇 |
免费 | 332篇 |
国内免费 | 2篇 |
出版年
2023年 | 28篇 |
2022年 | 50篇 |
2021年 | 94篇 |
2020年 | 60篇 |
2019年 | 92篇 |
2018年 | 119篇 |
2017年 | 106篇 |
2016年 | 135篇 |
2015年 | 262篇 |
2014年 | 261篇 |
2013年 | 406篇 |
2012年 | 429篇 |
2011年 | 403篇 |
2010年 | 244篇 |
2009年 | 204篇 |
2008年 | 341篇 |
2007年 | 318篇 |
2006年 | 269篇 |
2005年 | 267篇 |
2004年 | 230篇 |
2003年 | 232篇 |
2002年 | 212篇 |
2001年 | 32篇 |
2000年 | 25篇 |
1999年 | 50篇 |
1998年 | 55篇 |
1997年 | 37篇 |
1996年 | 38篇 |
1995年 | 40篇 |
1994年 | 35篇 |
1993年 | 22篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 27篇 |
1989年 | 28篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 22篇 |
1985年 | 13篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 11篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1977年 | 15篇 |
1976年 | 14篇 |
1975年 | 15篇 |
1974年 | 8篇 |
1971年 | 8篇 |
排序方式: 共有5470条查询结果,搜索用时 46 毫秒
1.
2.
3.
4.
Giovanni Murtas 《Systems and synthetic biology》2010,4(2):85-93
One of the major properties of the semi-synthetic minimal cell, as a model for early living cells, is the ability to self-reproduce
itself, and the reproduction of the boundary layer or vesicle compartment is part of this process. A minimal bio-molecular
mechanism based on the activity of one single enzyme, the FAS-B (Fatty Acid Synthase) Type I enzyme from Brevibacterium ammoniagenes, is encapsulated in 1-palmitoyl-2oleoyl-sn-glycero-3-phosphatidylcholine (POPC) liposomes to control lipid synthesis. Consequently molecules of palmitic acid released
from the FAS catalysis, within the internal lumen, move toward the membrane compartment and become incorporated into the phospholipid
bilayer. As a result the vesicle membranes change in lipid composition and liposome growth can be monitored. Here we report
the first experiments showing vesicles growth by catalysis of one enzyme only that produces cell boundary from within. This
is the prototype of the simplest autopoietic minimal cell. 相似文献
5.
Sequence complexity and diversity of polyadenylated RNA molecules transcribed in human myeloid cells
6.
Sergio Davinelli Mariano Intrieri Claudio Russo Alfonso Di Costanzo Davide Zella Paolo Bosco Giovanni Scapagnini 《Immunity & ageing : I & A》2011,8(1):1-10
Alzheimer's disease is a progressive and neurodegenerative disorder which involves multiple molecular mechanisms. Intense research during the last years has accumulated a large body of data and the search for sensitive and specific biomarkers has undergone a rapid evolution. However, the diagnosis remains problematic and the current tests do not accurately detect the process leading to neurodegeneration. Biomarkers discovery and validation are considered the key aspects to support clinical diagnosis and provide discriminatory power between different stages of the disorder. A considerable challenge is to integrate different types of data from new potent approach to reach a common interpretation and replicate the findings across studies and populations. Furthermore, long-term clinical follow-up and combined analysis of several biomarkers are among the most promising perspectives to diagnose and manage the disease. The present review will focus on the recent published data providing an updated overview of the main achievements in the genetic and biochemical research of the Alzheimer's disease. We also discuss the latest and most significant results that will help to define a specific disease signature whose validity might be clinically relevant for future AD diagnosis. 相似文献
7.
8.
The voltage-sensitive Na+ channel is responsible for the action potential of membrane electrical excitability in neuronal tissue. Three methods were used to demonstrate the presence of neurotoxin-responsive Na+ channels in two hybrid cell lines resulting from the fusion of excitable human neuroblastoma cells with mouse fibroblasts. Only one of the two electrically active hybrid cell lines maintained the sensitivity of the neuroblastoma parent to tetrodotoxin (TTX). The other hybrid, although electrically active, was not responsive to TTX or scorpion venom. Comparisons of the patterns of expression of membrane excitability and of chromosome complements in these human neuroblastoma cell hybrids suggest that the phenotype of membrane excitability is composed of genetically distinct elements. 相似文献
9.
Protein damage and degradation by oxygen radicals. IV. Degradation of denatured protein 总被引:11,自引:0,他引:11
Proteolytic degradation of oxidatively damaged [3H] bovine serum albumin [( 3H]BSA) was studied during incubation with cell-free erythrocyte extracts and a wide variety (14) of purified proteases. [3H]BSA was pretreated by exposure (60Co radiation) to the hydroxyl radical (.OH), the superoxide anion radical (O2-), or the combination of .OH + O2- + oxygen. Treated (and untreated) samples were dialyzed and then incubated with erythrocyte extract or proteases for measurements of proteolytic susceptibility (release of acid-soluble counts). Both .OH and .OH + O2- + caused severalfold increases in proteolytic susceptibility (with extract and proteases), but O2- alone had no effect. Proteolytic susceptibility reached a maximum at 15 nmol of .OH/nmol of BSA and declined thereafter. In contrast, proteolytic susceptibility was still increasing at an .OH + O2-/BSA molar ratio of 100 (50% .OH + 50% O2-). Degradation in erythrocyte extracts was conducted by a novel ATP- and Ca2+-independent pathway, with maximal activity at pH 7.8. Inhibitor profiles indicate that this pathway may involve metalloproteases and serine proteases. Comparisons of proteolytic susceptibility with multiple modifications to BSA primary, secondary, and tertiary structure revealed a high correlation (r = 0.98) with denaturation/increased hydrophobicity by low concentrations of .OH. Covalent aggregation reactions (BSA cross-linking) may explain the declining proteolytic susceptibility observed at .OH/BSA molar ratios greater than 20. Protein denaturation may also have caused the increased proteolytic susceptibility induced by .OH + O2- + O2, but no simple correlation could be obtained. Results with .OH + O2- + O2 appear to have been complicated by direct BSA fragmentation reactions involving (.OH-induced) protein radicals and oxygen. These data indicate a direct and quantitative relationship between protein damage by oxygen radicals and increased proteolytic susceptibility. Oxidative denaturation may exemplify a simple, yet effective inherent mechanism for intracellular proteolysis. 相似文献
10.
Influence of Hydrocortisone on Chick Embryo Retina Development 总被引:1,自引:1,他引:0
Renza Vento Giuseppina D'Ancona Michela Giuliano Gennaro Taibi Giovanni Tesoriere 《Journal of neurochemistry》1987,48(6):1693-1698
Treatment of chick embryos in ovo with hydrocortisone-21-phosphate (a single dose of 150 micrograms) caused a marked reduction of retinal thymidine kinase activity 24 h later. The inhibitory effect was highest (65-70%) in 8-10-day-old embryos and declined with age, disappearing after day 15. It was accompanied by a reduction in thickness of the retinal layers. Adrenocorticotropic hormone (ACTH) treatment (10 micrograms daily for 2 days) also produced an age-dependent inhibitory effect on retinal thymidine kinase, whereas treatment with a single dose of 200 micrograms of metopirone, a compound that prevents the 11 beta-hydroxylation of steroid molecules in the adrenal glands, impeded the decrease in thymidine kinase activity that normally occurs in chick embryo retina after day 9 of development. In addition, metopirone prevented the inhibition exerted by ACTH on thymidine kinase activity but had no effect on the action of hydrocortisone. 相似文献