全文获取类型
收费全文 | 8992篇 |
免费 | 440篇 |
国内免费 | 844篇 |
出版年
2024年 | 12篇 |
2023年 | 93篇 |
2022年 | 127篇 |
2021年 | 145篇 |
2020年 | 146篇 |
2019年 | 159篇 |
2018年 | 180篇 |
2017年 | 124篇 |
2016年 | 180篇 |
2015年 | 189篇 |
2014年 | 442篇 |
2013年 | 526篇 |
2012年 | 348篇 |
2011年 | 360篇 |
2010年 | 303篇 |
2009年 | 410篇 |
2008年 | 446篇 |
2007年 | 453篇 |
2006年 | 453篇 |
2005年 | 452篇 |
2004年 | 395篇 |
2003年 | 410篇 |
2002年 | 395篇 |
2001年 | 303篇 |
2000年 | 255篇 |
1999年 | 270篇 |
1998年 | 240篇 |
1997年 | 234篇 |
1996年 | 197篇 |
1995年 | 219篇 |
1994年 | 202篇 |
1993年 | 187篇 |
1992年 | 212篇 |
1991年 | 156篇 |
1990年 | 142篇 |
1989年 | 124篇 |
1988年 | 138篇 |
1987年 | 105篇 |
1986年 | 99篇 |
1985年 | 98篇 |
1984年 | 110篇 |
1983年 | 58篇 |
1982年 | 69篇 |
1981年 | 33篇 |
1980年 | 17篇 |
1979年 | 20篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Isabelle Matricon 《Cell and tissue research》1973,136(4):569-578
Résumé L'épithélium pharyngien d'Alcyonidium polyoum possède des cellules pourvues d'une très grande vacuole. L'incompressibilité du liquide vacuolaire permet un élargissement brusque de l'organe lors de la contraction du manchon musculaire strié qui enserre cette vacuole. Les fibres musculaires sont insérées sur le plasmalemme apical par des filaments unitifs. Le point d'attache est relié à la lame amorphe du cell-coat qui entoure les microvillosités par des fibrilles, réalisant probablement une liaison mécamique plus efficace. Le reticulum sarcoplasmique porte des ribosomes. Le cytoplasme apical renferme des vésicules de diverses catégories.
Some ultrastructural data about a myoepithelium: The pharynx of a bryozoan
Summary Pharyngeal cells of Alcyonidium polyoum (Bryozoa) are provided with very large vacuoles. Each vacuole is enveloped by a thin layer of striated muscle, whose contraction enlarges the organ. Filaments join the muscular elements to the apical plasmalemma. This point of muscular insertion is connected by fibrils with the amorphic lamina of cell-coat which surrounds the microvilli. Ribosomes are often found on dyads. Various vesicles are located in the apical cytoplasm.相似文献
12.
B. K. Pierson S. J. Giovannoni D. A. Stahl R. W. Castenholz 《Archives of microbiology》1985,142(2):164-167
An unusual filamentous, gliding bacterium was found in a few hot springs in Oregon where it formed a nearly unispecific top layer of microbial mats. It contained a bacteriochlorophyll a-like pigment and an abundance of carotenoids. There were no chlorosomes or additional chlorophylls. The organism was aerotolerant and appeared to be photoheterotrophic. It was successfully co-cultured with an aerobic chemoheterotroph in a medium containing glucose and casamino acids. Although it has many characteristics in common with the genus Chloroflexus, the lack of chlorosomes and bacteriochlorophyll c and the aerobic nature of this organism indicate that it should be placed in a new genus. This conclusion is supported by 5S rRNA nucleotide sequence data. 相似文献
13.
Abstract Transposon Tn 501 , which encodes resistance to mercuric ions, was introduced into Rhizobium japonicum 110 and 31 by conjugal transfer. The transposon donor plasmid (pMD100) was able to mobilize into R. japonicum , but could not be maintained. Hg2+ -resistant colonies were recovered at a frequency of 1.9 × 10−8 /recipient for strain 110, and 1.7 × 10−7 /recipient for strain 31. Presence of Tn 501 in Hg-resistant isolates was verified by Southern analysis and demonstrating transposition of Hg resistance. Transposon mutagenesis has been used to generate auxotrophic mutations at low frequency. 相似文献
14.
Ding-Kwo Chang Shu-Fang Cheng Chi-Hui Lin EricAssen B. Kantchev Cheng-Wei Wu 《生物化学与生物物理学报:生物膜》2005,1712(1):37-51
Two glutamic acid-rich fusion peptide analogs of influenza hemagglutinin were synthesized to study the organization of the charged peptides in the membranous media. Fluorescence and gel electrophoresis experiments suggested a loose association between the monomers in the vesicles. A model was built which showed that a positional difference of 3, 7 and 4, 8 results in the exposure of Glu3 and Glu7 side chains to the apolar lipidic core. Supportive results include: first, pKa values of two pH units higher than reference value in aqueous medium for Glu3 and Glu7 CγH, whereas the deviation of pKa from the reference value for Glu4 and Glu8 CγH is substantially smaller; second, Hill coefficients of titration shift of these protons indicate anti-cooperativity for Glu3 and Glu7 side chain protons but less so for Glu4 and Glu8, implying a strong electrostatic interaction between Glu3 and Glu7 possibly resulting from their localization in an apolar environment; third, positive and larger titration shift for NH of Glu3 is observed compared to that of Glu4, suggesting stronger hydrogen bond between the NH and the carboxylic group of Glu3 than that of Glu4, consistent with higher degree of exposure to hydrophobic medium for the side chain of Glu3. 相似文献
15.
16.
17.
18.
Nicholas Cianciotto Terry Serwold-Davis Neal Groman Giulio Ratti Rino Rappuoli 《FEMS microbiology letters》1990,66(1-3):299-301
Chromosomal restriction fragments of Corynebacterium ulcerans and C. diphtheriae, containing an integration site for corynephages of the beta family, show homology on Southern blots. Homologous DNA in also found in the soil isolate C. glutamicum, although this strain is not susceptible to beta-corynephages. Three of these DNA fragments, one for each bacterial strain, and a fragment of gamma-corynephage DNA previously shown to contain the phage integration site, were cloned and sequenced. Alignment of the 3 bacterial sequences shows a very high degree of homology in a stretch of ca 120 nucleotides, whereas the rest of the sequences is generally non-homologous. Within this common bacterial portion, a segment of ca. 96 nucleotides (core sequence) is also highly homologous to the phage sequence. The first half (ca. 50 bp) of the core sequence is identical in all aligned sequences whereas the second half, which is largely occupied by a stem-and-loop structure, contains point mutations peculiar to each clone. The described sequences are likely to be involved in phage integration/excision processes. 相似文献
19.
《Bioscience, biotechnology, and biochemistry》2013,77(2):346-348
The carnivorous plant Dionaea muscipula (Venus’s flytrap) secretes proteinases into the digestive fluid to digest prey proteins. In this study, we obtained evidence that the digestive fluid contains a cysteine endopeptidase, presumably belonging to the papain family, through inhibitor studies and partial amino acid sequencing of the major SDS–PAGE band protein. The name “dionain” is proposed for the enzyme. 相似文献
20.
The family Fagaceae includes several species and presents huge genetic variability. In the last two decades, several genetic studies about phylogenetics and genetic diversity of Fagaceae have emerged. ISSR markers were used to evaluate the genetic diversity of 26 species of Fagaceae belonging to the genera Castanea, Fagus and Quercus. Among several primers tested, 17 were selected for the evaluation of diversity and estimation of genetic relationships. A total of 371 ISSR markers were produced and each primer revealed high polymorphism. Specific ISSR markers for the Quercus infrageneric groups were amplified. ISSRs proved to be a reliable tool for the discrimination of the analyzed species per genus, infrageneric group and/or ecological origin. 相似文献