全文获取类型
收费全文 | 4633篇 |
免费 | 359篇 |
出版年
2023年 | 26篇 |
2022年 | 70篇 |
2021年 | 131篇 |
2020年 | 81篇 |
2019年 | 97篇 |
2018年 | 133篇 |
2017年 | 110篇 |
2016年 | 177篇 |
2015年 | 255篇 |
2014年 | 269篇 |
2013年 | 376篇 |
2012年 | 410篇 |
2011年 | 395篇 |
2010年 | 243篇 |
2009年 | 237篇 |
2008年 | 302篇 |
2007年 | 255篇 |
2006年 | 218篇 |
2005年 | 230篇 |
2004年 | 204篇 |
2003年 | 187篇 |
2002年 | 149篇 |
2001年 | 39篇 |
2000年 | 20篇 |
1999年 | 34篇 |
1998年 | 24篇 |
1997年 | 30篇 |
1996年 | 30篇 |
1995年 | 24篇 |
1994年 | 27篇 |
1993年 | 16篇 |
1992年 | 24篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有4992条查询结果,搜索用时 15 毫秒
31.
Daniele Castiglia Alessandro Cestelli Maria Scaturro Tommaso Nastasi Italia Di Liegro 《Neurochemical research》1994,19(12):1531-1537
Two overlapping rat cDNAs, covering a continuous region of 1107 base pairs, have been isolated and sequenced. The clones contain identical open reading frames, encoding a 136 amino acid long polypeptide which exhibits 100% identity to other mammalian H3.3 histone variants. We show that the inserts derive, in particular, from the H3.3B gene. We used these inserts and an insert from an H1° encoding clone, previously described (6), as probes to study the accumulation of mRNAs encoding the corresponding histone replacement variants (namely, H1° and H3.3) during rat brain development. We found that the concentration of both H1° and H3.3B mRNAs decreases from the embryonal day 18 (E18) to the postnatal day 10 (P10), with inverse correlation to protein accumulation.This paper is dedicated to our friend Paolo Carbone who devoted his life to research and teaching in Genetics. We will always remember him for scientific honesty and for his unique qualities of humanity. 相似文献
32.
Efficient extracellular production of hybrid E. coli heat-labile enterotoxin B subunits in a marine vibrio 总被引:1,自引:0,他引:1
Alessandro Marcello Arianna Loregian Giorgio Palù Timothy R. Hirst 《FEMS microbiology letters》1994,117(1):47-51
Abstract Escherichia coli heat-labile enterotoxin B subunit (EtxB) has been proposed as a potential protein carrier for the delivery of heterologous peptides to target cells, particularly for the oral delivery of epitopes to the mucosal immune system. In this study, two extensions to the C-terminus of EtxB were genetically engineered that correspond to a well-characterized neutralising epitope of glycoprotein D from herpes simplex virus (EtxB-gD) and to the C-terminal nine amino acids from the 38 kDa subunit of HSV-encoded ribonucleotide reductase (EtxB-R2). Here we describe the extracellular secretion of the two hybrid EtxBs from a marine Vibrio harbouring a broad-host range inducible expression vector containing the hybrid genes. Large amounts of intact fusion proteins (15–20 mg per liter of culture) were secreted into the medium upon induction. These hybrid proteins maintained the receptor-binding activity of the native toxin as well as being cross-reactive with anti-EtxB and anti-heterologous peptide monoclonal antibodies. 相似文献
33.
Jean-François Manen Alessandro Natali Friedrich Ehrendorfer 《Plant Systematics and Evolution》1994,190(3-4):195-211
A phylogenetic analysis of 25 species, representing eight genera of theRubieae tribe (Rubiaceae), has been made using the DNA sequence of the chloroplastatp B-rbc L intergene region. Six tropical genera from other tribes ofRubiaceae have been used as outgroups. Whatever the method of analysis (distance, parsimony or maximum likelihood), five groups are clearly separated and described as informal clades. Their relative relationships are not clearly resolved by the parsimony analysis, resulting in eight equally parsimonious trees, 327 steps long, with a consistency index (CI) of 0.749 (excluding uninformative sites). TheRubieae tribe appears monophyletic from the data available. Some new and partly unexpected phylogenetic relationships are suggested. The genusRubia forms a separate clade and appears to be the relatively advanced sister group of the remaining taxa. TheSherardia clade also includes the generaCrucianella andPhuopsis. Galium sect.Aparinoides appears closely attached to theAsperula sect.Glabella clade. The remaining taxa ofGalium are paraphyletic:Galium sect.Platygalium (in theCruciata clade) is linked to the advanced generaCruciata andValantia; the more apomorphic groups ofGalium form theGalium sect.Galium clade, including the perennial sectionsGalium, Leiogalium, andLeptogalium as well as the annual (and possibly polyphyletic) sect.Kolgyda. 相似文献
34.
Friedrich Ehrendorfer Jean-François Manen Alessandro Natali 《Plant Systematics and Evolution》1994,190(3-4):245-248
Representatives of seven genera from five tribes ofRubiaceae have been compared in respect to a non-coding intergene cpDNA region of about 1000 bp, situated between the atpB and the rbcL genes. The resulting most parsimonious PAUP cladogram corresponds very well with one based on total cpDNA restriction site data obtained byBremer & Jansen (1991). The two different molecular analyses thus corroborate each other and contribute to an improved systematic arrangement of the large family, e.g., in respect to placing the tribeHedyotideae clearly into the subfamilyRubioideae, closer toRubieae than toPsychotrieae. 相似文献
35.
36.
Alessandro Negro Vincenza Corsa Stephen D. Skaper Lanfranco Callegaro 《Neurochemical research》1993,18(6):705-709
The immunological properties of the neurotrophins NGF, BDNF, and NT-3 were compared using polyclonal and monoclonal antibodies against the subunit of mouse NGF. Affinity-purified anti-NGF IgG consistently recognized NGF and NT-3 on Western blots, and inhibited the trophic activity of NGF and NT-3 but not BDNF. In contrast, anti-NGF monoclonal antibodies did not block the trophic activity of either NT-3 or BDNF. These results are consistent with the greater structural overlap between NGF and NT-3 than between NGF and BDNF. 相似文献
37.
38.
Pietro Cugini Loredana Di Palma Salvatore Di Simone Piernatale Lucia Paola Battisti Alessandro Coppola Giuseppe Leone 《Chronobiology international》1993,10(1):73-78
This study aimed to explore the 24-h patterns of stroke volume, cardiac output, and peripheral vascular resistance along with other correlated variables, such as left ventricular ejection time, ejection velocity index, thoracic fluid index, heart rate, and blood pressure. The study was performed on 12 clinically healthy subjects by means of a noninvasive beat-to-beat monitoring using the thoracic electric bioimpedance technique associated with the automated sphygmomano-metric recording. Time data series were analyzed by means of chronobiological procedures. The results documented the occurrence of a circadian rhythm for all the variables investigated, giving relevance to the beat-to-beat bioperiodicity of cardiac output and peripheral vascular resistance. Temporal quantification of the investigated variables may be useful for a better insight of the chronophysiology of the cardiovascular apparatus. 相似文献
39.
Alessandro Bulfone Hee-Joong Kim Luis Puelles Matthew H. Porteus Joseph F. Grippo John L.R. Rubenstein 《Mechanisms of development》1993,40(3):129-140
The pattern of RNA expression of the murine Dlx-2 (Tes-1) homeobox gene is described in embryos ranging in age from E8.5 through E11.5. Dlx-2 is a vertebrate homologue of the Drosophila Distal-less (Dll) gene. Dll expression in the Drosophila embryo is principally limited to the primordia of the brain, head and limbs. Dlx-2 is also expressed principally in the primordia of the forebrain, head and limbs. Within these regions it is expressed in spatially restricted domains. These include two discontinuous regions of the forebrain (basal telencephalon and ventral diencephalon), the branchial arches, facial ectoderm, cranial ganglia and limb ectoderm. Several mouse and human disorders have phenotypes which potentially are the result of mutations in the Dlx genes. 相似文献
40.
Franco Alessandro Buoso Sara Zanin Laura Pinton Roberto Tomasi Nicola 《Journal of Plant Growth Regulation》2023,42(3):1567-1581
Journal of Plant Growth Regulation - The wide use of copper (Cu)-based fungicide has caused a stepwise accumulation of Cu in the environment increasing the occurrence of phytotoxicity in crops. To... 相似文献