全文获取类型
收费全文 | 10253篇 |
免费 | 1035篇 |
国内免费 | 1篇 |
专业分类
11289篇 |
出版年
2022年 | 76篇 |
2021年 | 143篇 |
2020年 | 75篇 |
2019年 | 107篇 |
2018年 | 110篇 |
2017年 | 127篇 |
2016年 | 222篇 |
2015年 | 321篇 |
2014年 | 367篇 |
2013年 | 430篇 |
2012年 | 551篇 |
2011年 | 534篇 |
2010年 | 331篇 |
2009年 | 306篇 |
2008年 | 459篇 |
2007年 | 507篇 |
2006年 | 428篇 |
2005年 | 424篇 |
2004年 | 408篇 |
2003年 | 412篇 |
2002年 | 362篇 |
2001年 | 223篇 |
2000年 | 216篇 |
1999年 | 171篇 |
1998年 | 122篇 |
1997年 | 115篇 |
1996年 | 95篇 |
1995年 | 98篇 |
1994年 | 87篇 |
1993年 | 109篇 |
1992年 | 181篇 |
1991年 | 156篇 |
1990年 | 183篇 |
1989年 | 159篇 |
1988年 | 171篇 |
1987年 | 123篇 |
1986年 | 127篇 |
1985年 | 148篇 |
1984年 | 134篇 |
1983年 | 112篇 |
1982年 | 92篇 |
1981年 | 101篇 |
1980年 | 82篇 |
1979年 | 116篇 |
1978年 | 95篇 |
1977年 | 93篇 |
1976年 | 87篇 |
1975年 | 81篇 |
1974年 | 88篇 |
1973年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A composite transposon 3'' to the cow fetal globin gene binds a sequence specific factor. 总被引:2,自引:2,他引:0 下载免费PDF全文
Two unusual sequence organizations were found within the beta-globin locus of the cow. Each was a composite, consisting of closely linked Alu-type repeats with a short stretch of genomic non-repetitive sequence, called a lagan, sandwiched between. One lagan was found 3' to the fetal globin gene, while the second lay between the adult globin gene and a globin pseudogene. Southern blot analysis indicated that both lagans appeared twice within the cow haploid genome, with the second copies lying outside the cow beta-globin locus. One of these non-globin locus homologues was cloned and subjected to sequence analysis. Comparison of the DNA sequence data showed that the lagan-Alu composite was transposed as a unit. The lagan 3' to the cow fetal globin gene contains the recognition site for a sequence specific DNA binding factor. This factor was present in extracts from fetal, but not from adult cow tissues. 相似文献
2.
Are we able to infer what happened to a person from a brief sample of his/her behaviour? It has been proposed that mentalising skills can be used to retrodict as well as predict behaviour, that is, to determine what mental states of a target have already occurred. The current study aimed to develop a paradigm to explore these processes, which takes into account the intricacies of real-life situations in which reasoning about mental states, as embodied in behaviour, may be utilised. A novel task was devised which involved observing subtle and naturalistic reactions of others in order to determine the event that had previously taken place. Thirty-five participants viewed videos of real individuals reacting to the researcher behaving in one of four possible ways, and were asked to judge which of the four ‘scenarios’ they thought the individual was responding to. Their eye movements were recorded to establish the visual strategies used. Participants were able to deduce successfully from a small sample of behaviour which scenario had previously occurred. Surprisingly, looking at the eye region was associated with poorer identification of the scenarios, and eye movement strategy varied depending on the event experienced by the person in the video. This suggests people flexibly deploy their attention using a retrodictive mindreading process to infer events. 相似文献
3.
4.
Elizabeth Storer Scholl Antonella Pirone Daniel H Cox R Keith Duncan Michele H Jacob 《Channels (Austin, Tex.)》2014,8(1):62-75
Small conductance Ca2+-sensitive potassium (SK2) channels are voltage-independent, Ca2+-activated ion channels that conduct potassium cations and thereby modulate the intrinsic excitability and synaptic transmission of neurons and sensory hair cells. In the cochlea, SK2 channels are functionally coupled to the highly Ca2+ permeant α9/10-nicotinic acetylcholine receptors (nAChRs) at olivocochlear postsynaptic sites. SK2 activation leads to outer hair cell hyperpolarization and frequency-selective suppression of afferent sound transmission. These inhibitory responses are essential for normal regulation of sound sensitivity, frequency selectivity, and suppression of background noise. However, little is known about the molecular interactions of these key functional channels. Here we show that SK2 channels co-precipitate with α9/10-nAChRs and with the actin-binding protein α-actinin-1. SK2 alternative splicing, resulting in a 3 amino acid insertion in the intracellular 3′ terminus, modulates these interactions. Further, relative abundance of the SK2 splice variants changes during developmental stages of synapse maturation in both the avian cochlea and the mammalian forebrain. Using heterologous cell expression to separately study the 2 distinct isoforms, we show that the variants differ in protein interactions and surface expression levels, and that Ca2+ and Ca2+-bound calmodulin differentially regulate their protein interactions. Our findings suggest that the SK2 isoforms may be distinctly modulated by activity-induced Ca2+ influx. Alternative splicing of SK2 may serve as a novel mechanism to differentially regulate the maturation and function of olivocochlear and neuronal synapses. 相似文献
5.
6.
7.
8.
9.
The baculovirus Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) initiates apoptosis in diverse insects through events triggered by virus DNA (vDNA) replication. To define the proapoptotic pathway and its role in antivirus defense, we investigated the link between the host''s DNA damage response (DDR) and apoptosis. We report here that AcMNPV elicits a DDR in the model insect Drosophila melanogaster. Replication of vDNA activated DDR kinases, as evidenced by ATM-driven phosphorylation of the Drosophila histone H2AX homolog (H2Av), a critical regulator of the DDR. Ablation or inhibition of ATM repressed H2Av phosphorylation and blocked virus-induced apoptosis. The DDR kinase inhibitors caffeine and KU55933 also prevented virus-induced apoptosis in cells derived from the permissive AcMNPV host, Spodoptera frugiperda. This block occurred at a step upstream of virus-mediated depletion of the cellular inhibitor-of-apoptosis protein, an event that initiates apoptosis in Spodoptera and Drosophila. Thus, the DDR is a conserved, proapoptotic response to baculovirus infection. DDR inhibition also repressed vDNA replication and reduced virus yields 100,000-fold, demonstrating that the DDR contributes to virus production, despite its recognized antivirus role. In contrast to virus-induced phosphorylation of Drosophila H2Av, AcMNPV blocked phosphorylation of the Spodoptera H2AX homolog (SfH2AX). Remarkably, AcMNPV also suppressed SfH2AX phosphorylation following pharmacologically induced DNA damage. These findings indicate that AcMNPV alters canonical DDR signaling in permissive cells. We conclude that AcMNPV triggers a proapoptotic DDR that is subsequently modified, presumably to stimulate vDNA replication. Thus, manipulation of the DDR to facilitate multiplication is an evolutionarily conserved strategy among DNA viruses of insects and mammals. 相似文献
10.
Ruth Duncan Pavla Rejmanova Jindrich Kopeček John B. Lloyd 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,678(1):143-150
Synthetic 125I-labelled N-(2-hydroxypropyl)methacrylamide copolymers containing four different, potentially degradable peptidyl side chains were incubated with rat visceral yolk sacs cultured in vitro. All copolymers were captured by fluid-phase pinocytosis and three of the side chains were susceptible to lysosomal hydrolysis, resulting in release of [125I]iodotyrosine back into the culture medium. Uptake and degradation was completely inhibited by 2,4-dinitrophenol. The thiol-proteinase inhibitor leupeptin did not affect the rate of pinocytosis, but caused different degrees of inhibition of hydrolysis depending on side chain composition. 相似文献