全文获取类型
收费全文 | 66712篇 |
免费 | 4181篇 |
国内免费 | 7篇 |
出版年
2023年 | 478篇 |
2022年 | 441篇 |
2021年 | 917篇 |
2020年 | 849篇 |
2019年 | 856篇 |
2018年 | 2122篇 |
2017年 | 1961篇 |
2016年 | 2564篇 |
2015年 | 3286篇 |
2014年 | 3300篇 |
2013年 | 4509篇 |
2012年 | 5272篇 |
2011年 | 4763篇 |
2010年 | 3014篇 |
2009年 | 2261篇 |
2008年 | 3581篇 |
2007年 | 3343篇 |
2006年 | 3144篇 |
2005年 | 2639篇 |
2004年 | 2563篇 |
2003年 | 2298篇 |
2002年 | 2104篇 |
2001年 | 1442篇 |
2000年 | 1439篇 |
1999年 | 1122篇 |
1998年 | 497篇 |
1997年 | 380篇 |
1996年 | 378篇 |
1995年 | 354篇 |
1994年 | 305篇 |
1993年 | 258篇 |
1992年 | 567篇 |
1991年 | 511篇 |
1990年 | 440篇 |
1989年 | 445篇 |
1988年 | 431篇 |
1987年 | 386篇 |
1986年 | 363篇 |
1985年 | 384篇 |
1984年 | 387篇 |
1983年 | 281篇 |
1982年 | 258篇 |
1981年 | 211篇 |
1980年 | 213篇 |
1979年 | 252篇 |
1978年 | 242篇 |
1975年 | 237篇 |
1974年 | 252篇 |
1973年 | 251篇 |
1972年 | 222篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A. Pons F.J. García A. Palou A. Alemany 《Journal of biochemical and biophysical methods》1981,5(3):153-156
A method for quantitative estimation of total radioactivity present in the free amino acid fraction of tissue samples has been described. Samples deproteinized with cold acetone were extracted, in acidic medium, with ethyl (peroxide free); after centrifugation, the aqueous phase was used for amino acid derivatization at 40°C for 15 h with 1-flouro-2,4-dinitrobenzene in bicarbonate-buffered medium. Aliquots of the derivatized samples were acidified and extracted twice again with ethyl ether. The combined organic phases were placed in glass scintilation vials, dried, and used for the determination of its radiactivity, corresponding to the radioactivity present in the free amino acid fraction of the sample. Deproteinized samples of rat blood plasma, as well as hen egg white and yolk were tested after addition of known quantities of 14C-labelled amino acids or glucose, for validation of the method. No glucose radioactivity was found in any of the extracted samples. All radioactivity added to the samples in the form of 14C-labelled alanine, glutamic acid, leucine and phenylalanine was quantitatively recovered in the derivatized fraction; only a fraction of arginine radioactivity was recovered. 相似文献
992.
A new species of Rhodotorula Harrison was recovered in May 1978 from Spanish powdered red pepper (Capsicum frutescens L.) in Madrid, Spain. It could not be identified with any hitherto described species of yeast and it was assigned to the genus Rhodotorula Harrison as representative of a new species on the bases of both its morphological and physiological characteristics, for which the name of Rhodotorula matritense is proposed. 相似文献
993.
994.
995.
996.
997.
998.
O A Orsingher E S Marichich V A Molina O A Ramírez 《Acta physiologica latino americana》1980,30(2):111-115
A sensitive and reliable fluorometric method for the simultaneous determination of dopamine, noradrenaline, 5-hydroxytryptamine and 5-hydroxy-indol acetic acid in small samples of brain tissues is described. The procedure is based on solvent extraction; catecholamines are oxidized by the Chang's method and 5-hydroxytryptamine and 5-hydroxy-indol acetic acid determined by reaction with o-phthalaldehyde, alpha-methyl-p-tyrosine causes a negligible interference with the procedure. Results of determination of these amines in different brain areas are reported. 相似文献
999.
Summary The effects of most frequently used carbohydrates and osmolalities of media on the growth and productivity ofClaviceps purpurea in submerged cultures were investigated. The maximum alkaloid yield was obtained with 20% mannitol as well as with 10% mannitol when 2% NaCl was added to the medium and the osmolality about 1 osmol/kg H2O was established at the end of fermentation. Increased or decreased osmolality of the medium had a negative influence on fungal growth and alkaloid production. Almost the same effect was observed with sucrose as with mannitol, whereas with glucose only maximal growth was achieved. 相似文献
1000.
On integrating experimental data published previously, the following picture of the mitochondrial adenine nucleotide (AdN) translocation system is being presented: 1. The AdN translocation system serves not only to transport ATP synthesized within mitochondria into the cytosol but also to transport cytosolic ATP into the mitochondria when oxidative phosphorylation is not functioning. 2. The AdN translocator is coded for by nuclear genes and the mitochondrial protein synthesis is not involved in its formation. 3. The AdN translocation system must be preserved and functioning even in cells which could dispense with oxidative phosphorylation. It assures appropriate concentrations of intramitochondrial ATP. 4. The intramitochondrial ATP is required for normal replication of mitochondrial DNA. Tis supports the view that the mitochondrion is a self-replicating semi-autonomous organelle. 5. The appropriate concentration of ATP must be present in mitochondria to make possible cell growth or multiplication. This points to a direct or indirect role of mitochondria in the control of cell proliferation. 相似文献