全文获取类型
收费全文 | 31652篇 |
免费 | 2368篇 |
国内免费 | 3篇 |
学科分类
生物科学 | 34023篇 |
出版年
2023年 | 236篇 |
2022年 | 389篇 |
2021年 | 764篇 |
2020年 | 567篇 |
2019年 | 768篇 |
2018年 | 969篇 |
2017年 | 934篇 |
2016年 | 1270篇 |
2015年 | 1614篇 |
2014年 | 1715篇 |
2013年 | 2278篇 |
2012年 | 2575篇 |
2011年 | 2407篇 |
2010年 | 1590篇 |
2009年 | 1319篇 |
2008年 | 1656篇 |
2007年 | 1589篇 |
2006年 | 1520篇 |
2005年 | 1240篇 |
2004年 | 1232篇 |
2003年 | 1125篇 |
2002年 | 1029篇 |
2001年 | 581篇 |
2000年 | 559篇 |
1999年 | 460篇 |
1998年 | 316篇 |
1997年 | 221篇 |
1996年 | 214篇 |
1995年 | 200篇 |
1994年 | 136篇 |
1993年 | 155篇 |
1992年 | 230篇 |
1991年 | 194篇 |
1990年 | 172篇 |
1989年 | 153篇 |
1988年 | 124篇 |
1987年 | 140篇 |
1986年 | 125篇 |
1985年 | 103篇 |
1984年 | 132篇 |
1983年 | 85篇 |
1982年 | 89篇 |
1981年 | 70篇 |
1980年 | 63篇 |
1979年 | 66篇 |
1978年 | 52篇 |
1974年 | 63篇 |
1973年 | 45篇 |
1970年 | 43篇 |
1969年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The protein synthesis activity of heart, skeletal muscle and liver polysomes from isoprotenerol-treated and control hamsters has been compared in an in vitro non-inititating translation system. Heart and skeletal muscle polysomes from treated hamsters were less active than controls and required a higher magnesium concentration for optimal protein synthesis. These results suggest that there is a conformational modification in heart and skeletal muscle ribosomes from isoprotenerol-treated hamsters. No such change was observed with ribosomes from the liver of isoproterenol-treated hamsters. 相似文献
82.
Effect of prolactin and glucocorticoids on P-enolpyruvate carboxykinase activity in liver and mammary gland from diabetic and lactating rats 总被引:1,自引:0,他引:1
María F. Lobato Mertxe Careche Manuel Ros Francisco J. Moreno Josefa P. García-Ruíz 《Molecular and cellular biochemistry》1985,67(1):19-23
Summary The administration of 2 bromo--ergocryptine, to reduce serum prolactin decreased the activity of cytosolic P-enolpyruvatc carboxykinase (GTP) (EC4.1.1.32) about 50% in both liver and mammary gland of lactating animals. Adrenalectomy had similar effects to those of bromo-a-ergocryptine. In contrast, there was a 50% increase in enzyme activity in the mammary gland of diabetic, lactating rats and a 10-fold increase in liver as compared with normal rats. P-enolpyruvate carboxykinase activity in mammary gland as liver is coordinately regulated by prolactin, glucocorticoids and insulin. 相似文献
83.
Photobiont cells of the lichen Evernia prunastri have completely been separated from their fungal partner by filtration through a bed of Sepharose 2B. Both mannitol and ribitol have been quantified by gas-liquid chromatography in the different steps of the isolation procedure. Absence of mannitol, which is exclusively produced by the mycobiont, has been used as the best probe to monitor isolation. 相似文献
84.
Extraction with dimethyl sulfoxide of wood-meal of the stem of bracatinga (Mimosa scabrella), a south Brazilian hardwood, that was defatted and delignified by treatment with aqueous chlorine at 0–5° followed by extraction with cold ethanol, gave a soluble O-acetylated 4-O-methyl-d-glucurono-d-xylan having (1→4)-linked β-d-xylopyranosyl residues that were unsubstituted (65%) and 2-O-(14%), 3-O- (16%), and 2,3-di-O-acetylated (5%), as determined by methylation analysis. Another preparation obtained by use of refluxing ethanol in the delignification process showed neither removal nor migration of acetyl groups. By comparison with synthetic, partly O-acetylated d-xylans of known composition, 13C-n.m.r. spectroscopy indicated that O-acetyl group migration does not occur during treatment with cold aqueous chlorine, refluxing ethanol, or water at 70°. Methyl 2-O-acetyl-4-O-methyl-β-d-xylopyranoside (6) was also unaffected by aqueous chlorine. O-Acetyl group migration took place more readily in aqueous and dimethyl sulfoxide solutions of 6 than of O-acetyl-d-xylans. The lowest temperatures at which migration was observed in monosaccharides was at 50 and 70° for solutions in D2O and (CD3)2SO, respectively. 相似文献
85.
Ramón F. Pinilla Amparo Cano Luis Boto Angel Pestan˜a 《Biochemical and biophysical research communications》1984,119(3):1141-1146
A transitory increase in ornithine decarboxylase activity has been observed soon after food removal from Dictyostelium discoideum amoeba. This increase can be prevented by supplementation of the differentiation buffer with the 11 amino acids known for their ability to retard the development of this slime mold. Lysine can replace the amino acid mixture with an apparent inhibition constant of 50 micromolar. This inhibition by lysine, which was only observed in vivo, took place within 5 min and was readily reversed upon lysine removal. 相似文献
86.
87.
F González Echeverría P S Cuasnicú A Piazza L Pi?eiro J A Blaquier 《Journal of reproduction and fertility》1984,71(2):433-437
The fertility of spermatozoa from the different epididymal segments of hamsters was tested by in-vivo insemination. Caput and proximal corpus spermatozoa were non-fertile; spermatozoa from the distal corpus epididymidis fertilized 13% (38/290) oocytes and those from the proximal and distal cauda epididymidis 71 and 87%, respectively. When tested by in-vitro insemination, distal corpus spermatozoa penetrated 44% of oocytes while those from the distal cauda fertilized 87% of oocytes. Spermatozoa from the distal corpus recovered in Medium BMOC fertilized 13% (28/219) of oocytes in vivo, while those mixed with an epididymal protein preparation (0.8 mg protein/ml) fertilized 24% (49/204; P less than 0.01) of oocytes. When distal corpus spermatozoa were inseminated in vivo with 0.8 mg epididymal protein preparation 34% (31/90) oocytes were fertilized and only 22% (23/103; P less than 0.05) oocytes were fertilized when the proteins were obtained from epididymides of animals castrated for 30 days. When distal corpus spermatozoa were preincubated for 5 h in medium without (control) or with protein preparation (0.8 or 1.6 mg protein/ml), a significant increase in in-vitro oocyte penetration was found (25 compared with 45%; P less than 0.05) when the protein was present at 1.6 mg/ml. These results confirm and extend previous observations suggesting a role for androgen-dependent glycoproteins secreted by the epididymis in the acquisition of fertilizing ability that occurs during sperm maturation. 相似文献
88.
The contribution deals with the phytocenological analysis of theRondeletio correifoliae-Andropogonetum multinervosi, an endemic savanna association occuring on the Siguanea Hills (Sierra de la Siguanea) near the Colony Hotel. 相似文献
89.
90.