全文获取类型
收费全文 | 52442篇 |
免费 | 4620篇 |
国内免费 | 1615篇 |
出版年
2023年 | 745篇 |
2022年 | 727篇 |
2021年 | 1416篇 |
2020年 | 1889篇 |
2019年 | 2500篇 |
2018年 | 2191篇 |
2017年 | 1526篇 |
2016年 | 1502篇 |
2015年 | 1715篇 |
2014年 | 3343篇 |
2013年 | 3768篇 |
2012年 | 2454篇 |
2011年 | 3188篇 |
2010年 | 2355篇 |
2009年 | 2615篇 |
2008年 | 2807篇 |
2007年 | 2748篇 |
2006年 | 2286篇 |
2005年 | 2088篇 |
2004年 | 1859篇 |
2003年 | 1583篇 |
2002年 | 1386篇 |
2001年 | 933篇 |
2000年 | 730篇 |
1999年 | 724篇 |
1998年 | 616篇 |
1997年 | 519篇 |
1996年 | 489篇 |
1995年 | 585篇 |
1994年 | 572篇 |
1993年 | 459篇 |
1992年 | 435篇 |
1991年 | 393篇 |
1990年 | 303篇 |
1989年 | 280篇 |
1988年 | 238篇 |
1987年 | 250篇 |
1986年 | 196篇 |
1985年 | 350篇 |
1984年 | 509篇 |
1983年 | 449篇 |
1982年 | 474篇 |
1981年 | 387篇 |
1980年 | 388篇 |
1979年 | 316篇 |
1978年 | 244篇 |
1977年 | 238篇 |
1976年 | 231篇 |
1975年 | 187篇 |
1974年 | 180篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
《Journal of molecular biology》2021,433(5):166809
Macroautophagy is a bulk degradation mechanism in eukaryotic cells. Efficiency of an essential step of this process in yeast, Atg8 lipidation, relies on the presence of Atg16, a subunit of the Atg12–Atg5-Atg16 complex acting as the E3-like enzyme in the ubiquitination-like reaction. A current view on the functional structure of Atg16 in the yeast S. cerevisiae comes from the two crystal structures that reveal the Atg5-interacting α-helix linked via a flexible linker to another α-helix of Atg16, which then assembles into a homodimer. This view does not explain the results of previous in vitro studies revealing Atg16-dependent deformations of membranes and liposome-binding of the Atg12–Atg5 conjugate upon addition of Atg16. Here we show that Atg16 acts as both a homodimerizing and peripheral membrane-binding polypeptide. These two characteristics are imposed by the two distinct regions that are disordered in the nascent protein. Atg16 binds to membranes in vivo via the amphipathic α-helix (amino acid residues 113–131) that has a coiled-coil-like propensity and a strong hydrophobic face for insertion into the membrane. The other protein region (residues 64–99) possesses a coiled-coil propensity, but not amphipathicity, and is dispensable for membrane anchoring of Atg16. This region acts as a Leu-zipper essential for formation of the Atg16 homodimer. Mutagenic disruption in either of these two distinct domains renders Atg16 proteins that, in contrast to wild type, completely fail to rescue the autophagy-defective phenotype of atg16Δ cells. Together, the results of this study yield a model for the molecular mechanism of Atg16 function in macroautophagy. 相似文献
82.
83.
84.
85.
86.
Cláudia N. Santos Marta Alves António Oliveira Ricardo B. Ferreira 《Journal of plant physiology》2013
Glycosylation is an important post-translational modification involved in the modulation of a wide variety of cellular processes. Because glycosydases are central, the aim of this study was to investigate the glycosyl activity present in the cotyledons of the seeds of an important crop legume, Lupinus albus, as well as potential natural substrates of the detected enzymes. 相似文献
87.
Inhibition of the Bacterial Cell Wall Synthesis in vitro by Enduracidin,a New Polypeptide Antibiotic
Michio Matsuhashi Ikuko Ohara Yoshihiro Yoshiyama 《Bioscience, biotechnology, and biochemistry》2013,77(1):134-137
Adenosine 5′-phosphosulfate (APS) kinase from a thermophilic bacterium, Bacillus st ear other mophilus, was purified to apparent homogeneity. The apparent molecular weight was 50 kDa, consisting of two 26-kDa subunits. The enzyme was very thermostable and lacked cysteine and methionine residues. Enzyme activity was more stimulated with Mn2 + , Zn2 +, or Co2 + than with Mg2 + and the Km for ATP and APS were 220 µM and 42 µM, respectively. 相似文献
88.
Phytochemical analysis of dried twigs of Marsdenia roylei (family Asclepiadaceae) has resulted in the isolation of a trisaccharide, maryal, and a diglycoside, rolinose. Their structures were determined as O-beta-D-oleandropyranosyl-(1-->4)-O-beta-D-digitoxopyranosyl++ +-(1-->4)-D- cymaral and ethyl O-beta-D-oleandropyranosyl-(1-->4)-O-3-O-methyl-6-deoxy-beta-D- allopyranoside, respectively, by chemical degradation and spectroscopic methods. 相似文献
89.
Xiuyun Ye Shigeru Yoshida T. B. Ng 《The international journal of biochemistry & cell biology》2000,32(11-12)
A mild and rapid method is described for isolating various milk proteins from bovine rennet whey. β-Lactoglobulin from bovine rennet whey was easily adsorbed on and desorbed from a weak anion exchanger, diethylaminoethyl-Toyopearl. However, α-lactalbumin could not be adsorbed onto the resin. α-Lactalbumin and β-lactoglobulin from rennet whey could also be adsorbed and separated using a strong anion exchanger, quaternary aminoethyl-Toyopearl. The rennet whey was passed through a strong cation exchanger, sulphopropyl-Toyopearl, to separate lactoperoxidase and lactoferrin. α-Lactalbumin and β-lactoglobulin were adsorbed onto quaternary aminoethyl-Toyopearl. α-Lactalbumin was eluted using a linear (0–0.15 M) concentration gradient of NaCl in 0.05 M Tris–HCl buffer (pH 8.5). Subsequently, β-lactoglobulin B and β-lactoglobulin A were eluted from the column with 0.05 M Tris–HCl (pH 6.8), using a linear (0.1–0.25 M) concentration gradient of NaCl. The yields were 1260 mg α-lactalbumin, 1290 mg β-lactoglobulin B and 2280 mg β-lactoglobulin A from 1 l rennet whey. 相似文献
90.
S. Z. Whetzel Y. H. Shih L. M. Georgic H. C. Akunne T. A. Pugsley 《Journal of neurochemistry》1997,69(6):2363-2368
Abstract: The dopamine (DA) D3 receptor antagonist PD 58491 {3-[4-[1-[4-[2-[4-(3-diethylaminopropoxy)phenyl]-benzoimidazol-1-yl-butyl]-1 H -benzoimidazol-2-yl]-phenoxy]propyl]diethylamine} bound with high affinity and selectivity to recombinant human DA D3 versus D2L and D4.2 receptors transfected into Chinese hamster ovary cells: K i values of 19.5 n M versus 2,362 and >3,000 n M , respectively. In contrast, the putative DA D3 receptor antagonist (+)-AJ76 displayed low affinity and selectivity for D3 versus D2L and D4.2 receptors (91 n M vs. 253 and 193 n M , respectively). In vitro, PD 58491 (1 n M −1µ M ) exhibited D3 receptor antagonist activity, reversing the quinpirole (10 n M )-induced stimulation of [3 H]thymidine uptake in D3 CHOpro-5 cells, but did not have any significant intrinsic activity by itself in this assay. PD 58491 did not decrease the γ-butyrolactone-induced increase in DA synthesis ( l -3,4-dihydroxyphenylalanine accumulation) in rat striatum, indicating that the compound possessed no in vivo DA D2 /D3 receptor agonist action at DA autoreceptors. PD 58491 (3–30 mg/kg, i.p.) generally did not alter DA or serotonin synthesis in either the striatum or mesolimbic region of rat brain. The D3 -preferring agonist PD 128907 decreased DA synthesis in striatum and mesolimbic regions, and this effect was attenuated by pretreatment with PD 58491. These findings support the hypothesis that DA D3 autoreceptors may in part modulate the synthesis and release of DA in striatum and mesolimbic regions. 相似文献