全文获取类型
收费全文 | 3394篇 |
免费 | 290篇 |
国内免费 | 366篇 |
专业分类
4050篇 |
出版年
2024年 | 9篇 |
2023年 | 44篇 |
2022年 | 127篇 |
2021年 | 185篇 |
2020年 | 128篇 |
2019年 | 185篇 |
2018年 | 166篇 |
2017年 | 107篇 |
2016年 | 146篇 |
2015年 | 191篇 |
2014年 | 273篇 |
2013年 | 262篇 |
2012年 | 291篇 |
2011年 | 273篇 |
2010年 | 178篇 |
2009年 | 142篇 |
2008年 | 178篇 |
2007年 | 142篇 |
2006年 | 128篇 |
2005年 | 119篇 |
2004年 | 102篇 |
2003年 | 101篇 |
2002年 | 92篇 |
2001年 | 64篇 |
2000年 | 49篇 |
1999年 | 57篇 |
1998年 | 39篇 |
1997年 | 39篇 |
1996年 | 27篇 |
1995年 | 28篇 |
1994年 | 28篇 |
1993年 | 16篇 |
1992年 | 20篇 |
1991年 | 29篇 |
1990年 | 21篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1973年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有4050条查询结果,搜索用时 15 毫秒
11.
Yu Shang Li Li Tengfei Zhang Qingping Luo Qingzhong Yu Zhe Zeng Lintao Li Miaomiao Jia Guoyi Tang Sanlin Fan Qin Lu Wenting Zhang Yuhan Xue Hongling Wang Wei Liu Hongcai Wang Rongrong Zhang Chan Ding Huabin Shao Guoyuan Wen 《PLoS pathogens》2022,18(6)
The development of thermostable vaccines can relieve the bottleneck of existing vaccines caused by thermal instability and subsequent poor efficacy, which is one of the predominant reasons for the millions of deaths caused by vaccine-preventable diseases. Research into the mechanism of viral thermostability may provide strategies for developing thermostable vaccines. Using Newcastle disease virus (NDV) as model, we identified the negative surface charge of attachment glycoprotein as a novel determinant of viral thermostability. It prevented the temperature-induced aggregation of glycoprotein and subsequent detachment from virion surface. Then structural stability of virion surface was improved and virus could bind to and infect cells efficiently after heat-treatment. Employing the approach of surface charge engineering, thermal stability of NDV and influenza A virus (IAV) vaccines was successfully improved. The increase in the level of vaccine thermal stability was determined by the value-added in the negative surface charge of the attachment glycoprotein. The engineered live and inactivated vaccines could be used efficiently after storage at 37°C for at least 10 and 60 days, respectively. Thus, our results revealed a novel surface-charge-mediated link between HN protein and NDV thermostability, which could be used to design thermal stable NDV and IAV vaccines rationally. 相似文献
12.
13.
捕食者-猎物关系的理论和应用研究 总被引:6,自引:0,他引:6
捕食者和猎物相互关系的研究,长期以来一直是动物生态学研究的中心课题之一。这种研究可区分为3种类型:第一是理论研究,即组建各种数学模型以便模拟捕食者和猎物间的相互关系;第二是实验种群研究,通常是在实验室内选用原生动物和节肢动物实验种群对捕食一猎物间的动态关系进行观察,并将观察结果与理论模型进行比较;第三是在田间对自然种群中的捕食者-猎物关系进行研究,并利用从理论研究和实验种群研究中所总结出来的各种基本原理对观察资料进行分析。在应用生态学领域中,常常靠引进新的更加有效的天敌来控制各种害虫。这些实际工作有些已获得成功,也有不少未取得预期效果,不管成功与否,它们都可被看作是对捕食者-猎物关系所进行的田间实验. 相似文献
14.
Hongchao Lv Yongshuai Jiang Jin Li Mingming Zhang Zhenwei Shang Jiajia Zheng Xin Wu Panpan Liu Ruijie Zhang Huimin Yu 《Molecular biology reports》2014,41(3):1299-1310
The aim of this study was to assess the association of polymorphisms in the promoter region of the IL-10 gene with the risk of inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC). Fifteen studies (3,693 cases and 4,574 controls) were included in a meta-analysis of association between IL-10 ?1082G/A, ?819C/T and ?592C/A polymorphisms, and IBD, CD and UC using allele contrast and the recessive, dominant, and additive models. Hardy–Weinberg equilibrium was confirmed for each study. Heterogeneity and study quality were investigated using stratification analyses and sensitivity analyses. Polymorphism ?1082G/A showed significant association with CD, with odds ratios (ORs) for the GG + GA genotype and GG versus AA genotype of 1.278 (1.004–1.627) and 1.238 (1.027–1.492) in all subjects. Significant associations were found in the Caucasian subgroup using the allele contrast, dominant, and additive models. C-allele carriers of the ?819C/T polymorphism were at increased risk of IBD (OR 1.093, 95 % CI 1.004–1.190). Association with the ?819C/T polymorphism was also found in Caucasians with CD (C vs. T: OR 1.104, 95 % CI 1.010–1.206; CC + CT vs. TT: OR 1.328, 95 % CI 1.006–1.754; CC vs. TT: OR 1.339, 95 % CI 1.008–1.778), and with UC (CC vs. CT + TT: OR 1.188, 95 % CI 1.019–1.385). No significant association was found between the ?592C/A polymorphism and IBD, CD or UC. In conclusion, the meta-analysis demonstrated clear association between the IL-10 polymorphisms ?1082G/A and ?819C/T and the risk of IBD. 相似文献
15.
16.
杂交水稻及其“三系”线粒体DNA的AP—PCR指纹图谱 总被引:22,自引:1,他引:22
为了研究水稻(Oryza sativa L.)细胞质雄性不育(CMS)与线粒体基因组的关系,应用AP-PCR 分析,用7 个任意单引物对6 种水稻品系线粒体DNA 进行了扩增。水稻线粒体DNA 的AP-PCR 产物可分为三种类型:(1)所有供试品系均能扩增的片段,它们代表了线粒体DNA 在进化上的保守性序列。有4 个引物检测到这类片段。(2)2 个以上水稻品系共同出现而在全部供试材料间存在差异的扩增片段,这类片段是检测水稻线粒体DNA多态性的主要来源。(3)一种细胞质类型所特有的扩增片段,从引物R2 和V5 的扩增产物中发现了这类片段,它们可能与CMS有关联。另外,WA型不育系珍汕97A 与其杂种之间在6 个引物的扩增图谱上均存在不同程度的差异,说明两者的线粒体DNA序列结构可能存在某种差别 相似文献
17.
18.
Xun Li Junli Wang Jinpei Li Jifeng Wu Yonggang Li Huawei Zhu Ruifang Fan Wenfang Xu 《Bioorganic & medicinal chemistry》2009,17(8):3053-3060
Overexpression of zinc-dependent metalloproteinase, aminopeptidase N (APN/CD13), is considered to be involved in the process of tumor invasion and metastasis. Herein we describe the synthesis and in vitro enzymatic inhibition assay of antineoplaston AS2–5 scaffold peptidomimetic compounds. The results demonstrated that most of these l-iso-glutamine derivatives displayed selective inhibitory activity against APN as compared with MMP-2, with IC50 values in the micromole range. The structure–activity relationships were also briefly discussed. 相似文献
19.
Apple Sucrose Transporter SUT1 and Sorbitol Transporter SOT6 Interact with Cytochrome b5 to Regulate Their Affinity for Substrate Sugars 总被引:1,自引:0,他引:1
Ren-Chun Fan Chang-Cao Peng Yan-Hong Xu Xiao-Fang Wang Yan Li Yi Shang Shu-Yuan Du Rui Zhao Xiao-Yan Zhang Ling-Yun Zhang Da-Peng Zhang 《Plant physiology》2009,150(4):1880-1901
Sugar transporters are central machineries to mediate cross-membrane transport of sugars into the cells, and sugar availability may serve as a signal to regulate the sugar transporters. However, the mechanisms of sugar transport regulation by signal sugar availability remain unclear in plant and animal cells. Here, we report that a sucrose transporter, MdSUT1, and a sorbitol transporter, MdSOT6, both localized to plasma membrane, were identified from apple (Malus domestica) fruit. Using a combination of the split-ubiquitin yeast two-hybrid, immunocoprecipitation, and bimolecular fluorescence complementation assays, the two distinct sugar transporters were shown to interact physically with an apple endoplasmic reticulum-anchored cytochrome b5 MdCYB5 in vitro and in vivo. In the yeast systems, the two different interaction complexes function to up-regulate the affinity of the sugar transporters, allowing cells to adapt to sugar starvation. An Arabidopsis (Arabidopsis thaliana) homolog of MdCYB5, AtCYB5-A, also interacts with the two sugar transporters and functions similarly. The point mutations leucine-73 → proline in MdSUT1 and leucine-117 → proline in MdSOT6, disrupting the bimolecular interactions but without significantly affecting the transporter activities, abolish the stimulating effects of the sugar transporter-cytochrome b5 complex on the affinity of the sugar transporters. However, the yeast (Saccharomyces cerevisiae) cytochrome b5 ScCYB5, an additional interacting partner of the two plant sugar transporters, has no function in the regulation of the sugar transporters, indicating that the observed biological functions in the yeast systems are specific to plant cytochrome b5s. These findings suggest a novel mechanism by which the plant cells tailor sugar uptake to the surrounding sugar availability. 相似文献
20.
In the past three decades a lot of research has been done on the extended family of carbohydrate-binding proteins from Sambucus nigra, including several so-called type 2 RIPs as well as hololectins. Although all these proteins have been studied for their carbohydrate-binding properties using hapten inhibition assays, detailed carbohydrate specificity studies have only been performed for a few Sambucus proteins. In particular SNA-I, has been studied extensively. Because of its unique binding characteristics this lectin was developed as an important tool in glycoconjugate research to detect sialic acid containing glycoconjugates. At present much less information is available with respect to the detailed carbohydrate binding specificity of other S. nigra lectins and RIPs, and as a consequence their applications remain limited. In this paper we report a comparative analysis of several lectins from S. nigra using the glycan microarray technology. Ultimately a better understanding of the ligands for each lectin can contribute to new/more applications for these lectins in glycoconjugate research. Furthermore, the data from glycan microarray analyses combined with the previously obtained sequence information can help to explain how evolution within a single lectin family eventually yielded a set of carbohydrate-binding proteins with a very broad specificity range. 相似文献