全文获取类型
收费全文 | 108695篇 |
免费 | 6364篇 |
国内免费 | 4310篇 |
出版年
2023年 | 1456篇 |
2022年 | 2173篇 |
2021年 | 2983篇 |
2020年 | 3069篇 |
2019年 | 4073篇 |
2018年 | 3602篇 |
2017年 | 2773篇 |
2016年 | 2779篇 |
2015年 | 3259篇 |
2014年 | 6153篇 |
2013年 | 8669篇 |
2012年 | 4666篇 |
2011年 | 6268篇 |
2010年 | 4724篇 |
2009年 | 5460篇 |
2008年 | 5688篇 |
2007年 | 5735篇 |
2006年 | 5063篇 |
2005年 | 4509篇 |
2004年 | 3909篇 |
2003年 | 3335篇 |
2002年 | 2921篇 |
2001年 | 2034篇 |
2000年 | 1680篇 |
1999年 | 1639篇 |
1998年 | 1679篇 |
1997年 | 1423篇 |
1996年 | 1335篇 |
1995年 | 1232篇 |
1994年 | 1183篇 |
1993年 | 1006篇 |
1992年 | 966篇 |
1991年 | 834篇 |
1990年 | 730篇 |
1989年 | 668篇 |
1988年 | 596篇 |
1987年 | 592篇 |
1986年 | 437篇 |
1985年 | 841篇 |
1984年 | 1206篇 |
1983年 | 856篇 |
1982年 | 971篇 |
1981年 | 768篇 |
1980年 | 652篇 |
1979年 | 585篇 |
1978年 | 420篇 |
1977年 | 389篇 |
1976年 | 322篇 |
1975年 | 274篇 |
1974年 | 269篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
11.
《Bioscience, biotechnology, and biochemistry》2013,77(1):188-190
Depolymerization of hyaluronic acid (HA) by low-molecular-weight Amadori-rearrangement products in the presence of Cu2 + was studied as an in vitro model for the glycated protein-mediated degradation of biopolymers. This oxygen radical-mediated depolymerization was found to be specifically accelerated by Cu2 + , and significantly inhibited by catalase, hydroxyl radical scavengers, and metal ion chelators. Glycated polylysine also depolymerized HA. The difference in depolymerization rate between low- and high-molecular-weight Amadori products is discussed. 相似文献
12.
Minjuan Shen Mingli Lin Mengqi Zhu Wenxin Zhang Danyang Lu Huanhuan Liu Jingjing Deng Kehua Que Xu Zhang 《Biochimica et Biophysica Acta (BBA)/General Subjects》2019,1863(1):167-181
Since their discovery, matrix vesicles (MVs) containing minerals have received considerable attention for their role in the mineralization of bone, dentin and calcified cartilage. Additionally, MVs' association with collagen fibrils, which serve as the scaffold for calcification in the organic matrix, has been repeatedly highlighted. The primary purpose of the present study was to establish a MVs–mimicking model (PEG-S-ACP/micelle) in vitro for studying the exact mechanism of MVs-mediated extra/intra fibrillar mineralization of collagen in vivo. In this study, high-concentration serine was used to stabilize the amorphous calcium phosphate (S-ACP), which was subsequently mixed with polyethylene glycol (PEG) to form PEG-S-ACP nanoparticles. The nanoparticles were loaded in the polysorbate 80 micelle through a micelle self-assembly process in an aqueous environment. This MVs–mimicking model is referred to as the PEG-S-ACP/micelle model. By adjusting the pH and surface tension of the PEG-S-ACP/micelle, two forms of minerals (crystalline mineral nodules and ACP nanoparticles) were released to achieve the extrafibrillar and intrafibrillar mineralization, respectively. This in vitro mineralization process reproduced the mineral nodules mediating in vivo extrafibrillar mineralization and provided key insights into a possible mechanism of biomineralization by which in vivo intrafibrillar mineralization could be induced by ACP nanoparticles released from MVs. Also, the PEG-S-ACP/micelle model provides a promising methodology to prepare mineralized collagen scaffolds for repairing bone defects in bone tissue engineering. 相似文献
13.
Defective transducing phages carrying aroG, the structural gene for phenylalanine (phe)-inhibitable phospho-2-keto-heptonate aldolase (EC 4.1.2.15; previously known as 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase[phe]), have been isolated, and DNA from two of these phages has been used to construct a restriction map of the region from att lambda to aroG. A 7.6-kb PstI-HindIII fragment from one of these phages was cloned into pBR322 and shown to contain aroG. The location of aroG within the 7.6 kb was established by subcloning and Tn3 transpositional mutagenesis. A fragment carrying the aroG promoter and operator has been cloned into a high copy number promoter-cloning vector (pMC489), and the resulting aroGpo-LacZ' (alpha) fusion subcloned in a low copy number vector. Strains with this fusion on the low copy number vector exhibit negative regulation of beta-galactosidase expression by both phenylalanine and tryptophan and positive regulation by tyrosine in a tyrR+ background. 相似文献
14.
FAB1/PIKfyve是介导PI(3,5)P2 (磷脂酰肌醇3,5-二磷酸)生物合成的磷酸肌醇激酶。在动物和酵母(Saccharomyces cerevisiae)中, PI(3,5)P2参与调控胞内膜运输, 但在植物中的研究较少。该文通过分析拟南芥(Arabidopsis thaliana) FAB1的T-DNA插入突变体的表型解析PI(3,5)P2的生物学功能。拟南芥FAB1基因家族包含FAB1A、FAB1B、FAB1C和FAB1D四个基因。研究发现, fab1a/b呈现雄配子体致死的表型。利用遗传杂交获得fab1b/c/d三突变体, 发现FAB1B、FAB1C和FAB1D功能缺失导致根毛相比野生型变短, 经FAB1特异性抑制剂YM201636处理后的野生型中也观察到相似的短根毛表型。此外, fab1b/c/d三突变体中DR5转录水平降低。同时, 外源施加生长素类似物2,4-D和NAA能部分恢复fab1b/c/d植株短根毛的表型, 但fab1b/c/d突变体对生长素转运抑制剂(1-NOA和TIBA)的敏感性与野生型相似。此外, FAB1B/C/D功能缺失使根毛中ROS的含量减少且影响肌动蛋白的表达。上述结果表明, FAB1B/C/D通过调控生长素分布、ROS含量和肌动蛋白的表达影响拟南芥根毛伸长。 相似文献
15.
16.
From three Fouquieria sp. 12 iridoid glucosides were isolated and identified. Eight of these were structurally related to galioside (monotropein methylester), while four were hydroxy substitution products of deoxyloganin. In three cases the glucoside occurred together with the corresponding 10-O-acetate. 相似文献
17.
18.
19.
20.