全文获取类型
收费全文 | 4064篇 |
免费 | 295篇 |
国内免费 | 4篇 |
出版年
2021年 | 32篇 |
2020年 | 21篇 |
2019年 | 27篇 |
2018年 | 37篇 |
2017年 | 29篇 |
2016年 | 68篇 |
2015年 | 102篇 |
2014年 | 126篇 |
2013年 | 204篇 |
2012年 | 236篇 |
2011年 | 204篇 |
2010年 | 113篇 |
2009年 | 101篇 |
2008年 | 198篇 |
2007年 | 201篇 |
2006年 | 160篇 |
2005年 | 183篇 |
2004年 | 183篇 |
2003年 | 162篇 |
2002年 | 185篇 |
2001年 | 132篇 |
2000年 | 143篇 |
1999年 | 116篇 |
1998年 | 63篇 |
1997年 | 53篇 |
1996年 | 36篇 |
1995年 | 44篇 |
1994年 | 35篇 |
1993年 | 49篇 |
1992年 | 77篇 |
1991年 | 76篇 |
1990年 | 70篇 |
1989年 | 90篇 |
1988年 | 56篇 |
1987年 | 63篇 |
1986年 | 56篇 |
1985年 | 71篇 |
1984年 | 67篇 |
1983年 | 40篇 |
1982年 | 39篇 |
1981年 | 29篇 |
1979年 | 44篇 |
1978年 | 29篇 |
1977年 | 36篇 |
1976年 | 22篇 |
1975年 | 25篇 |
1974年 | 26篇 |
1973年 | 26篇 |
1972年 | 24篇 |
1970年 | 23篇 |
排序方式: 共有4363条查询结果,搜索用时 15 毫秒
981.
982.
A culture of BALB/c 3T3 cells grown in the presence of 40 microM of the ceramide analog compound RV538 (2-decanolyamino-3-morpholino-1-phenylpropanol) for several passages caused a substantial decrease in the level of all glycosphingolipids and an accumulation of ceramide and sphingomyelin. Associated with these chemical changes of sphingolipid composition and metabolism, the following phenotypic changes were observed: (i) loss of the cobblestone appearance at cell density saturation and development of fibroblastic appearance with partial overlapping of cells; (ii) reduction of cell growth rate; (iii) enhanced production of lactic acid; (iv) enhanced rate of glucose transport; and (v) higher incidence of large colony formation with infiltrating appearance in soft agar. Cell morphology changes, lactate production, and enhanced sugar uptake were reversed by co-culturing cells with gangliosides, particularly trisialogangliosides. Thus, these phenotypic changes mimicking those of oncogenically transformed cells are closely related to the blocked synthesis of glycolipids in these cells, whereas other changes may be caused by an accumulation of ceramide and sphingomyelin. 相似文献
983.
984.
Atsushi Takeda Jinko Sawashita Sachiyo Takefuta Shoji Okada 《Biological trace element research》1998,61(1):71-78
To study the relationship between tissue accumulation of Zinc (Zn) and neurodegeneration in the nigrostriatal dopaminergic
pathway,65Zn distribution in this pathway was examined after unilateral injection of 6-hydroxydopamine (6-OHDA) into the substantia
nigra of rats. When65ZnCl2 was intravenously injected 4 days after treatment with 6-OHDA,65Zn was concentrated in the ipsilateral substantia nigra 6 days after65Zn injection. On the other hand, 19 d after treatment with 6-OHDA,65Zn distribution in the ipsilateral substantia nigra was decreased to the level of the contralateral one. When NH4
99TcO4, which cannot go through the blood-brain barrier, was injected into rats 4 d after treatment with 6-OHDA,99Tc was concentrated in the ipsilateral substantia nigra 30 min after99Tc injection, but no longer detectable 6 d after injection. These results suggest that Zn is necessary for a repair process
called replacement gliosis after the death of neurons and that excess Zn does not accumulate in the lesion after completion
of the gliosis. 相似文献
985.
Tsutomu Takayanagi Gentaro Okada Seiya Chiba 《Bioscience, biotechnology, and biochemistry》2013,77(9):2337-2341
A gas-liquid chromatographic method was applied to the determination of anomeric forms of isomaltose and glucose produced by Arthrobacter globiformis isomalto-dextranase and glucodex- tranase. The anomeric forms of products released from isomaltotriose, panose and dextran were quantitatively determined. The isomalto-dextranase that was also capable of splitting the α-1,4- glucosidic linkage of panose was found to exclusively produce α-isomaltose from these substrates, and the glucodextranase, ^-glucose. 相似文献
986.
987.
988.
Kenichi Tomi Makiko Kitao Norihiro Konishi Hiroshi Murakami Yasuki Matsumura Takahiro Hayashi 《Bioscience, biotechnology, and biochemistry》2016,80(5):840-847
Essential oils and hydrosols were extracted from rosemary harvested in different seasons, and the chemical compositions of volatile components in the two fractions were analyzed by gas chromatography–mass spectrometry (GC–MS). Enantiomers of some volatile components were also analyzed by enantioselective GC–MS. Classification of aroma components based on chemical groups revealed that essential oils contained high levels of monoterpene hydrocarbons but hydrosols did not. Furthermore, the enantiomeric ratios within some volatile components were different from each other; for example, only the (S)-form was observed for limonene and the (R)-form was dominant for verbenone. These indicate the importance of determining the enantiomer composition of volatile components for investigating the physiological and psychological effects on humans. Overall, enantiomeric ratios were determined by volatile components, with no difference between essential oils and hydrosols or between seasons. 相似文献
989.
990.