全文获取类型
收费全文 | 9031篇 |
免费 | 540篇 |
国内免费 | 7篇 |
出版年
2021年 | 89篇 |
2020年 | 49篇 |
2019年 | 74篇 |
2018年 | 111篇 |
2017年 | 94篇 |
2016年 | 143篇 |
2015年 | 224篇 |
2014年 | 303篇 |
2013年 | 451篇 |
2012年 | 427篇 |
2011年 | 511篇 |
2010年 | 276篇 |
2009年 | 288篇 |
2008年 | 461篇 |
2007年 | 490篇 |
2006年 | 466篇 |
2005年 | 505篇 |
2004年 | 460篇 |
2003年 | 456篇 |
2002年 | 477篇 |
2001年 | 264篇 |
2000年 | 276篇 |
1999年 | 214篇 |
1998年 | 145篇 |
1997年 | 80篇 |
1996年 | 81篇 |
1995年 | 94篇 |
1994年 | 86篇 |
1993年 | 99篇 |
1992年 | 155篇 |
1991年 | 156篇 |
1990年 | 132篇 |
1989年 | 131篇 |
1988年 | 143篇 |
1987年 | 117篇 |
1986年 | 113篇 |
1985年 | 98篇 |
1984年 | 76篇 |
1983年 | 82篇 |
1982年 | 59篇 |
1981年 | 41篇 |
1980年 | 47篇 |
1979年 | 54篇 |
1978年 | 52篇 |
1977年 | 34篇 |
1976年 | 35篇 |
1975年 | 40篇 |
1974年 | 36篇 |
1973年 | 39篇 |
1971年 | 36篇 |
排序方式: 共有9578条查询结果,搜索用时 15 毫秒
1.
2.
Rat liver deflavoxanthine dehydrogenase has been prepared by incubating native enzyme with calcium chloride. On reconstitution with FAD, about 85% of the original activity is recovered, all which is the O2-dependent type. In contrast, when dithiothreitol-treated deflavoenzyme is incubated with FAD, the recovery of activity is almost the same as above, but most of the recovered activity is of the NAD-dependent type. Deflavoenzyme with or without previous treatment with dithiothreitol was also reconstituted with two artificial FAD analogues, 8-mercapto-FAD and 6-OH-FAD. The difference spectra between the reconstituted enzymes and the initial deflavoenzyme indicate that, in each case, the FAD analogue is bound in its neutral form in dithiothreitol-treated enzyme, whereas it is bound in the anionic form in enzyme without previous dithiothreitol treatment. Furthermore, the protonated forms can be converted into the anionic forms on storage with a concomitant change of activity from the NAD-dependent to the O2-dependent type. This clearly indicates different environments around FAD in the two types of enzyme protein, which are shown to be interconvertible through oxidation-reduction of enzyme cysteinyl residues. 相似文献
3.
Despite increasing interest in the behavior of zoo animals, studies of nocturnal behavior of zoo animals are limited. In this study, we investigated the relationship between parturition, season, and the sleep‐related behaviors in captive reticulated giraffes to better understand the nocturnal life in giraffes. The subjects were two adult reticulated giraffes living in Kyoto City Zoo, Japan. Observations were made via an infrared camera that was mounted in the indoor enclosure between June 2007 and August 2009. We analyzed video clips that were recorded between 16:30 and 09:00 the next morning, over a total of 199 days. Sleep‐related behaviors were classified into two categories based on the posture of the giraffes; recumbent posture and paradoxical sleep. We also recorded the laterality of recumbent posture, which was coded based on the direction of the legs against the torso (right or left). Seasonal differences in sleep behaviors between summer and winter were observed in both individuals. They tended to start to lie down earlier in the winter than in the summer. Parturition also affected the behaviors as both individuals decreased the behaviors before and after the parturition of the female. Additionally, the female lay on her left side less frequently than her right when resuming a recumbent posture in the pre‐parturition period, while such laterality was not observed in the baseline and post‐parturition period. These results suggested that season and parturition are important factors for determining the sleep‐related behaviors in giraffes. Further studies are needed to understand how these changes in sleep affect other welfare parameters. 相似文献
4.
Yoshinari Maeda Kiyoshi Yoshimura Hiroto Matsui Yoshitaro Shindo Takao Tamesa Yukio Tokumitsu Noriaki Hashimoto Yoshihiro Tokuhisa Kazuhiko Sakamoto Kouhei Sakai Yutaka Suehiro Yuji Hinoda Koji Tamada Shigefumi Yoshino Shoichi Hazama Masaaki Oka 《Cancer immunology, immunotherapy : CII》2015,64(8):1047-1056
5.
6.
Yuichi Mori Yoshitaka Miura Yutaka Oiso Seo Hisao Kozaki Takazumi 《Human genetics》1995,96(4):481-482
The human thyroxine-binding globulin (TBG) gene has been localized to X chromosome (Xq22.2) by in situ hybridization using a biotinylated gDNA probe. This is consistent with previous mapping of the TBG gene to chromosome Xq21-q22. 相似文献
7.
8.
9.
10.
Hoshino Atsushi; Abe Yukihide; Saito Norio; Inagaki Yoshishige; Iida Shigeru 《Plant & cell physiology》1997,38(8):970-974
The Japanese morning glory carrying the recessive mutable speckledallele with the dominant speckled-activator bears colorlessflowers with fine and round colored spots distributed over thecorolla whereas the plant without the speckled-activator producespale yellow flowers. Previous chemical analysis has indicatedthat a mutation in the gene for flavanone 3-hydroxylase (F3H)is a likely candidate for the speckled allele. However, theF3HmRNA without sequence alteration accumulates normally inthe pale yellow flowers, indicating that the speckled alleleis neither the F3H gene nor a regulatory gene acting on theF3H gene expression. (Received April 4, 1997; Accepted June 2, 1997) 相似文献