全文获取类型
收费全文 | 106259篇 |
免费 | 6356篇 |
国内免费 | 4876篇 |
出版年
2023年 | 1341篇 |
2022年 | 2188篇 |
2021年 | 2898篇 |
2020年 | 2875篇 |
2019年 | 3295篇 |
2018年 | 3225篇 |
2017年 | 2504篇 |
2016年 | 2526篇 |
2015年 | 2985篇 |
2014年 | 5647篇 |
2013年 | 7995篇 |
2012年 | 4208篇 |
2011年 | 5805篇 |
2010年 | 4372篇 |
2009年 | 5230篇 |
2008年 | 5483篇 |
2007年 | 5526篇 |
2006年 | 4872篇 |
2005年 | 4453篇 |
2004年 | 3867篇 |
2003年 | 3404篇 |
2002年 | 3000篇 |
2001年 | 2176篇 |
2000年 | 1884篇 |
1999年 | 1871篇 |
1998年 | 1798篇 |
1997年 | 1623篇 |
1996年 | 1557篇 |
1995年 | 1443篇 |
1994年 | 1368篇 |
1993年 | 1265篇 |
1992年 | 1136篇 |
1991年 | 1028篇 |
1990年 | 885篇 |
1989年 | 824篇 |
1988年 | 763篇 |
1987年 | 749篇 |
1986年 | 588篇 |
1985年 | 978篇 |
1984年 | 1329篇 |
1983年 | 941篇 |
1982年 | 1068篇 |
1981年 | 829篇 |
1980年 | 754篇 |
1979年 | 657篇 |
1978年 | 449篇 |
1977年 | 401篇 |
1976年 | 333篇 |
1975年 | 275篇 |
1974年 | 271篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
141.
When hemolymph is taken from Ascaris lumbricoides at the time the worm is collected from pigs, it contains acetic, propionic, 2-methylbutyric, n-valeric, 2-methylvaleric, and succinic acid radicals; tiglic acid is absent. 相似文献
142.
143.
144.
Abstract: Phenylacetic acid, the major metabolite of phenylethylamine, has been identified and quantitated in rat brain regions by capillary column high-resolution gas chromatography mass spectrometry. Its distribution is heterogeneous and correlates with that of phenylethylamine. The values obtained were (ng/g ± SEM): whole brain, 31.2 ± 2.7; caudate nucleus, 64.6 ± 6.5; hypothalamus, 60.1 ± 7.4; cerebellum, 31.3 ± 2.9; brainstem, 33.1 ± 3.3, and the "rest," 27.6 ± 3.0. 相似文献
145.
Aquaspirillum magnetotacticum MS-1 cells cultured microaerobically (dissolved O2 tension 1% of saturation), expressed proteins with superoxide dismutase (SOD) activity. The majority (roughly 95%) of total cell superoxide dismutase activity was located in the cell periplasm with little or no activity in the cell cytoplasm. Irontype SOD (FeSOD) contributed 88% of the total activity activity detected, although a manganese-type SOD (MnSOD) was present in the periplasm as well. Cells cultured at a higher dissolved O2 tension (10% of saturation) expressed increased activity of the MnSOD relative to that of the FeSOD. 相似文献
146.
Novel 2D van der Waals heterostructures with innovative bimetallic oxychloride (Bi‐ and Sb‐based oxychloride) nanosheets that are well dispersed on reduced graphene oxide nanosheets, are established through element engineering for superior potassium ion battery (PIBs) anodes. This material displays an exceptional electrochemical performance, obtaining a discharge capacity as high as 360 mAh g?1 at 100 mA g?1 after running 1000 cycles for over 9 months with a capacity preservation percentage of 88.5% and achieving a discharge capacity as high as 319 mAh g?1 at 1000 mA g?1, in addition to the low charge/discharge plateaus for anodes and promising full cell performance. More significantly, the nature of such 2D van der Waals heterostructures, including the element engineering for morphology control, the function of each component of heterostructures, the mechanism of potassium ion storage, and the process of K+ intercalation accompanied with the lattice distortion and chemical bond breakages, is explored in depth. This study is critical for not only paving the way for the practical application of PIBs but also shedding light on fundamentals of potassium ion storage in 2D van der Waals heterostructures. 相似文献
147.
A possibly physiologically significant inhibition of yeast enolase by fluoride occurs in the absence of inorganic phosphate. The inhibition increases with time, is strongly dependent on fluoride concentration and requires substrate and “catalytic” Mg2+. The inhibition increases more slowly in the presence of product (phosphoenolpyruvate) than substrate (2-phosphoglycerate). The dependence on fluoride concentration and the spans of substrate analogue displacement titrations suggest the inhibition is produced by two moles of fluoride per active site. 相似文献
148.
149.
150.
《Current biology : CB》2020,30(5):827-839.e4
- Download : Download high-res image (204KB)
- Download : Download full-size image