全文获取类型
收费全文 | 15706篇 |
免费 | 1464篇 |
国内免费 | 2329篇 |
出版年
2024年 | 53篇 |
2023年 | 256篇 |
2022年 | 677篇 |
2021年 | 993篇 |
2020年 | 783篇 |
2019年 | 919篇 |
2018年 | 782篇 |
2017年 | 615篇 |
2016年 | 791篇 |
2015年 | 1135篇 |
2014年 | 1370篇 |
2013年 | 1376篇 |
2012年 | 1679篇 |
2011年 | 1594篇 |
2010年 | 963篇 |
2009年 | 828篇 |
2008年 | 909篇 |
2007年 | 754篇 |
2006年 | 624篇 |
2005年 | 478篇 |
2004年 | 366篇 |
2003年 | 323篇 |
2002年 | 242篇 |
2001年 | 125篇 |
2000年 | 134篇 |
1999年 | 137篇 |
1998年 | 90篇 |
1997年 | 73篇 |
1996年 | 67篇 |
1995年 | 57篇 |
1994年 | 47篇 |
1993年 | 33篇 |
1992年 | 41篇 |
1991年 | 42篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 26篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
Renke Dai Suoping Zhai Xiaoxiong Wei Matthew R. Pincus Robert E. Vestal Fred K. Friedman 《Journal of Protein Chemistry》1998,17(7):643-650
Cytochrome P450 1A2 metabolizes a number of important drugs, procarcinogens, and endogenous compounds. Several flavones, a
class of phytochemicals consumed in the human diet, have been shown to differentially inhibit human P450 1A2-mediated methoxyresorufin
demethylase. A molecular model of this P450 was constructed in order to elucidate the molecular basis of the P450-flavone
interaction. Flavone and its 3,5,7-trihydroxy and 3,5,7-trimethoxy derivatives were docked into the active site to assess
their mode of binding. The site is hydrophobic and includes several residues that hydrogen bond with substituents on the flavone
nucleus. The binding interactions of these flavones in the modeled active side are consistent with their relative inhibitory
potentials, namely 3,5,7-trihydroxylflavone > flavone >3,5,7-trimethoxylflavone, toward P450 1A2-mediated methoxyresorufin
demethylation. 相似文献
942.
943.
944.
945.
946.
947.
948.
Chitta Kasyapa Ting‐Lei Gu Lalitha Natarajan Roberto Polakiewicz John K. Cowell 《Proteomics》2009,9(16):3979-3988
The ZNF198‐fibroblast growth factor receptor‐1 (FGFR1) fusion kinase is a constitutively activated tyrosine kinase associated with a specific atypical myeloproliferative disease. The chimeric protein localizes to the cytoplasm, unlike the wild type FGFR1 receptor kinase, and presumably inappropriately phosphorylates specific targets as part of the oncogenic signaling cascade. Other than known targets of the FGFR1 kinase itself, few specific targets of ZNF198‐FGFR1 have been identified. Using a genetically engineered HEK 293 cell system, we have identified proteins that are specifically phosphorylated in the presence of the fusion kinase using anti‐phosphotyrosine immunoprecipitation and MS. Compared with 293 cells expressing exongenous wild type FGFR1, ZNF198‐FGFR1 is associated with phosphorylation of several proteins including SSBP2, ABL, FLJ14235, CALM and TRIM4 proteins. The specificity of the phosphorylation events in the SSBP2 and ABL proteins, which have previously been implicated in leukemogenesis, was further confirmed independently using immunoprecipitation with protein‐specific antibodies and Western blotting. The MS analysis also identified the phosphorylation events in the ZNF198 moiety in the chimeric protein that might be related to its function. These studies identify the intersection of several different leukemia‐related pathways in the development of this myeloproliferative disorder and provide new insights into the substrates of FGFR1 under defined conditions. 相似文献
949.
Triterpenoids and Flavonoids from the Leaves of Astragalus membranaceus and Their Inhibitory Effects on Nitric Oxide Production
下载免费PDF全文
![点击此处可从《化学与生物多样性》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhi‐Bin Wang Ya‐Dong Zhai Zhen‐Ping Ma Chun‐Juan Yang Rong Pan Jia‐Li Yu Qiu‐Hong Wang Bing‐You Yang Hai‐Xue Kuang 《化学与生物多样性》2015,12(10):1575-1584
Four new cycloartane triterpenes, named huangqiyegenins V and VI and huangqiyenins K and L ( 1 – 4 , resp.), together with nine known triterpenoids, 5 – 13 , and eight flavonoids, 14 – 21 , were isolated from a 70%‐EtOH extract of Astragalus membranaceus leaves. The structures of the new compounds were elucidated by detailed spectroscopic analyses, and the compounds were identified as (9β,11α,16β,20R,24S)‐11,16,25‐trihydroxy‐20,24‐epoxy‐9,19‐cyclolanostane‐3,6‐dione ( 1 ), (9β,16β,24S)‐16,24,25‐trihydroxy‐9,19‐cyclolanostane‐3,6‐dione ( 2 ), (3β,6α,9β,16β,20R,24R)‐16,25‐dihydroxy‐3‐(β‐D ‐xylopyranosyloxy)‐20,24‐epoxy‐9,19‐cyclolanostan‐6‐yl acetate ( 3 ), and (3β,6α,9β,16β,24E)‐26‐(β‐D ‐glucopyranosyloxy)‐16‐hydroxy‐3‐(β‐D ‐xylopyranosyloxy)‐9,19‐cyclolanost‐24‐en‐6‐yl acetate ( 4 ). All isolated compounds were evaluated for their inhibitory activities against LPS‐induced NO production in RAW264.7 macrophage cells. Compounds 1 – 3, 14, 15 , and 18 exhibited strong inhibition on LPS‐induced NO release by macrophages with IC50 values of 14.4–27.1 μM . 相似文献
950.