全文获取类型
收费全文 | 49607篇 |
免费 | 3083篇 |
国内免费 | 14篇 |
出版年
2023年 | 278篇 |
2022年 | 288篇 |
2021年 | 672篇 |
2020年 | 560篇 |
2019年 | 559篇 |
2018年 | 1374篇 |
2017年 | 1165篇 |
2016年 | 1699篇 |
2015年 | 2303篇 |
2014年 | 2379篇 |
2013年 | 3161篇 |
2012年 | 3685篇 |
2011年 | 3425篇 |
2010年 | 2149篇 |
2009年 | 1675篇 |
2008年 | 2540篇 |
2007年 | 2551篇 |
2006年 | 2530篇 |
2005年 | 2117篇 |
2004年 | 2080篇 |
2003年 | 1820篇 |
2002年 | 1785篇 |
2001年 | 1132篇 |
2000年 | 1083篇 |
1999年 | 849篇 |
1998年 | 392篇 |
1997年 | 244篇 |
1996年 | 280篇 |
1995年 | 282篇 |
1994年 | 228篇 |
1993年 | 199篇 |
1992年 | 518篇 |
1991年 | 455篇 |
1990年 | 433篇 |
1989年 | 412篇 |
1988年 | 377篇 |
1987年 | 381篇 |
1986年 | 331篇 |
1985年 | 339篇 |
1984年 | 274篇 |
1983年 | 270篇 |
1982年 | 212篇 |
1981年 | 180篇 |
1979年 | 302篇 |
1977年 | 185篇 |
1974年 | 205篇 |
1973年 | 197篇 |
1972年 | 178篇 |
1970年 | 180篇 |
1969年 | 178篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
Y S López-Boado P Herrero T Fernández R Fernández F Moreno 《Journal of general microbiology》1988,134(9):2499-2505
Incorporation of 32P into Saccharomyces cerevisiae isocitrate lyase was observed after addition of glucose to a culture incubated with [32P]orthophosphoric acid. A band of 32P-labelled protein was coincident with the enzyme band when immunoprecipitates were subjected to SDS-PAGE and autoradiography. No label was found in the band corresponding to the isocitrate lyase when immunoprecipitation was done with a control pre-immune serum or in the presence of excess pure unlabelled enzyme. The incorporation of phosphate was associated with a decrease in enzyme activity. Phosphorylated isocitrate lyase was not proteolytically degraded when cells were cultured in mineral medium. The loss of protein antigenicity only took place when the yeast was grown in a complex medium containing glucose. 相似文献
232.
Rogelio O. Arellano Fidel Ramón Amelia Rivera Guido A. Zampighi 《The Journal of membrane biology》1988,101(1):119-131
Summary Lateral axons from the abdominal nerve cord of cray-fish were internally perfused with the calcium receptor calmodulin (CaM) in solutions with low (pCa>7.0) or high (pCa 5.5) calcium concentrations and studied electrophysiologically and morphologically. Results from these experiments show that when the internal solution contains calcium-activated calmodulin (Ca2+-CaM) the junctional resistance between the axons increases from control values of about 60 to 500–600 k in 60 min. In contrast, axons perfused with calmodulin in low calcium solutions maintain their junctional resistance at control levels during the 60-min perfusion. Similar results are obtained when only one or both coupled axons are perfused.The morphological study shows that in the perfused axons the axoplasmic organelles are replaced or grossly perturbed by the perfusion solution up to the region of the synapses. Additionally, in axons perfused with Ca2+-CaM there are regions where the synaptic gap between the membranes decreases from a control 4–6 to 2–3 nm. Both electrophysiological and morphological results can be interpreted as indicating that calcium-activated calmodulin acts directly on the junctional channels to induce their closure. 相似文献
233.
The role and source of gibberellins (GAs) involved in the development of parthenocarpic fruits of Pisum sativum L. has been investigated. Gibberellins applied to the leaf adjacent to an emasculated ovary induced parthenocarpic fruit development on intact plants. The application of gibberellic acid (GA3) had to be done within 1 d of anthesis to be fully effective and the response was concentration-dependent. Gibberellin A1 and GA3 worked equally well and GA20 was less efficient. [3H]Gibberellin A1 applied to the leaf accumulated in the ovary and the accumulation was related to the growth response. These experiments show that GA applied to the leaf in high enough concentration is translocated to the ovary. Emasculated ovaries on decapitated pea plants develop without application of growth hormones. When [3H] GA1 was applied to the leaf adjacent to the ovary a substantial amount of radioactivity accumulated in the growing shoot of intact plants. In decapitated plants, however, this radioactivity was mainly found in the ovary. There it caused growth proportional to the accumulation of CA1. Application of LAB 150978, an inhibitor of GA biosynthesis, to decapitated plants inhibited parthenocarpic fruit development and this inhibition was counteracted by the application of GA3 (either to the fruit, or the leaf adjacent to the ovary, or through the lower cut end of the stem). All evidence taken together supports the view that parthenocarpic pea fruit development on topped plants depends on the import of gibberellins or their precursors, probably from the vegetative aerial parts of the plant.Abbreviations FW
flesh weight
- GAn
gibberellin An
- HPLC
high-performance liquid chromatography 相似文献
234.
F di Jeso A Truscello G Martinotti S Colli 《Comptes rendus des séances de la Société de biologie et de ses filiales》1988,182(3):266-269
In the last years our researches on neurotropic drugs follow our hypothesis that the strong effects on nervous system have always hidden more widespread effects on all tissues and cells. It is often required to employ local anesthetics in practising dentistry and orthodontics, particularly when children have to be treated. We have assayed in vitro one of these dental anesthetics, mepivacaine, on liver rat mitochondria: it depresses the respiration coupled to phosphorylation in mitochondria having a good respiratory control; so respiratory control too is depressed, but P/O ratio is unaffected; also respiration uncoupled by 2.4-dinitrophenol is depressed. Depressing respiration cooperates with anesthesia; unchanging P/O is good for the health of the cells and tissues treated by the mepivacaine. 相似文献
235.
236.
237.
Verónica Téllez Ariel Ahumada Juan Muro Soledad Sepúlveda Luis Izquierdo 《Development genes and evolution》1988,197(6):360-365
Summary Two-cell mouse ova, which were centrifuged for l h at 70 000–90 000xg, showed a precise stratification of the cytoplasm and an elongation of the nucleus. The ova were fixed at different times and observed by light and electron microscopy using cytochemical methods and detergent extractions. Within 40 min after centrifugation the normal-looking morphology was recovered except for the persisting lipid caps at the centripetal poles of the blastomeres. Cleavage, compaction and blastulation were not prevented by centrifugation. Treatments with colcemid or cytochalasin D delayed but did not impair recovery. These results suggest that a resilient cytoskeletal structure may be involved in this kind of embryonic regulation. 相似文献
238.
Summary By means of an experimental factorial design the role of several culture conditions is described and its values determined for the maximum yeast production in mixed cultures ofAspergillus oryzae andRhodotorula glutinis. 相似文献
239.
M. Pilar López M. Jose Gómez-Lechón Jose V. Castell 《In vitro cellular & developmental biology. Plant》1988,24(6):511-517
Summary This study examines the factors involved in the rapid glycolysis and glycogenolysis that occur during the first stages of
hepatocyte culture: a) Shortly after seeding glycolysis, estimated as lactate released to culture medium, increased 10 times
in comparison to that reported in vivo. By 8 to 9 h of culture, hepatocytes were nearly glycogen-depleted even in the presence
of insulin. b) 6-Phosphofructo-2-kinase remained 100% active during this period. The proportion of the initial active phosphorylase
(87%) decreased to 57% by 7 h of culture. c) Fructose 2,6-bisphosphate content was initially similar to that found in liver
of fed animals, decreased after seeding and increased thereafter up to four times the initial concentration. In spite of changes
in the concentration of this activator, the glycolytic rate remained high and constant. d) ADP and AMP increased sharply after
cell plating, reaching values 1.7 and 3.5 times higher. The rise in AMP levels may be involved in the activation of glycolysis
and glycogenolysis, because this metabolite is known to act as an allosteric activator of phosphofrucktokinase and glycogen
phosphorylase. This metabolic situation resembles that of cells under hypoxia.
Part of this work was presented at the 38th Annual Meeting of the Tissue Culture Association, Washington, DC, May 1987. 相似文献
240.