全文获取类型
收费全文 | 4585篇 |
免费 | 335篇 |
国内免费 | 609篇 |
专业分类
5529篇 |
出版年
2024年 | 12篇 |
2023年 | 85篇 |
2022年 | 201篇 |
2021年 | 267篇 |
2020年 | 182篇 |
2019年 | 207篇 |
2018年 | 255篇 |
2017年 | 171篇 |
2016年 | 220篇 |
2015年 | 306篇 |
2014年 | 370篇 |
2013年 | 360篇 |
2012年 | 434篇 |
2011年 | 381篇 |
2010年 | 252篇 |
2009年 | 194篇 |
2008年 | 259篇 |
2007年 | 255篇 |
2006年 | 193篇 |
2005年 | 145篇 |
2004年 | 131篇 |
2003年 | 102篇 |
2002年 | 110篇 |
2001年 | 65篇 |
2000年 | 48篇 |
1999年 | 59篇 |
1998年 | 49篇 |
1997年 | 46篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 24篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有5529条查询结果,搜索用时 0 毫秒
121.
为了研究G蛋白Rab3a与神经生长抑制因子 (growthinhibitoryfactor,GIF ,原称金属硫蛋白 3,MT 3)相互作用对神经元细胞生长的影响 ,以嗜铬细胞瘤株 (pheochromocytoma)PC1 2充当神经元模型 .将hMT 3(humanMT 3)和Rab3a基因分别克隆至真核表达载体pFlag CMV 2和pSV HA中 ,质粒共同转染PC1 2细胞 ,观察转染后细胞的生长状态 .以共转染pFlag CMV 2 hMT 1和pSV HA Rab3a的细胞组作为对照 ,验证hMT 3与Rab3a相互作用对PC1 2影响的特异性 .结果发现 ,共转染pFlag CMV 2 hMT 3和pSV HA Rab3a的PC1 2细胞生长明显受到抑制 ,细胞生长抑制率与GIF在脑提取物存在F的神经元生长抑制作用接近 ,但转染两基因中的任何单个基因以及共转染pFlag CMV 2 hMT 1和pSV HA Rab3a对PC1 2细胞生长无影响 .进一步构建重组表达质粒pGEX 4T 1 Rab3a和pGEX 4T 1 hMT 3,转化大肠杆菌BL2 1 ,经谷胱甘肽 Sepharose 4B亲和层析、凝血酶酶切和SephacrylS 1 0 0纯化 ,得到纯度 95 %以上的Rab3a和hMT 3蛋白 .体外细胞生物学活性检测表明 ,表达的Rab3a蛋白与重组hMT 3蛋白共培养PC1 2 ,对细胞的生长产生了明显的特异性协同抑制作用 ,抑制曲线与GIF在脑提取物存在下的神经元生长抑制曲线极为相似 相似文献
122.
Spider venoms are complex mixtures of neurotoxicpeptides, proteins and low molecular mass organicmolecules. Their neurotoxic activity is due to the interac-tion of the venom components with cellular receptors, inparticular ion channels. Spider venoms have… 相似文献
123.
Xiaolong Xia Yafeng Shao Jiafu Jiang Xinping Du Liping Sheng Fadi Chen Weimin Fang Zhiyong Guan Sumei Chen 《PloS one》2015,10(12)
MicroRNAs (miRNAs) are important regulators of gene expression, affecting many biological processes. As yet, their roles in the response of chrysanthemum to aphid feeding have not been explored. Here, the identity and abundance of miRNAs induced by aphid infestation have been obtained using high-throughput Illumina sequencing platform. Three leaf small RNA libraries were generated, one from plants infested with the aphid Macrosiphoniella sanbourni (library A), one from plants with mock puncture treatment (library M), and the third from untreated control plants (library CK). A total of 7,944,797, 7,605,251 and 9,244,002 clean unique reads, ranging from 18 to 30 nucleotides (nt) in length, were obtained from library CK, A and M, respectively. As a result, 303 conserved miRNAs belonging to 276 miRNAs families and 234 potential novel miRNAs were detected in chrysanthemum leaf, out of which 80, 100 and 79 significantly differentially expressed miRNAs were identified in the comparison of CK-VS-A, CK-VS-M and M-VS-A, respectively. Several of the differentially abundant miRNAs (in particular miR159a, miR160a, miR393a) may be associated with the plant''s response to aphid infestation. 相似文献
124.
125.
126.
The Fruit Dropping Characters of Sweet Cherry and Its Interior Causes in Insufficient Chilling Zone 总被引:1,自引:0,他引:1
Guo K. B. Qiao G. Qiu Z. L. Wen Z. Yang H. Wen X. P. 《Russian Journal of Plant Physiology》2020,67(1):94-102
Russian Journal of Plant Physiology - Attempts had been made to provide evidences insight into the pattern and physiological mechanism of sweet cherry fruit dropping. However, the fruit abscission... 相似文献
127.
Dechuang Jiao Jingyang Zhang Ping Chen Xuhui Guo Jianghua Qiao Jiujun Zhu Lina Wang Zhenduo Lu Zhenzhen Liu 《Journal of cellular and molecular medicine》2021,25(1):397-410
Recent reports showed that haematological and neurological expressed 1-like (HN1L) gene participated in tumorigenesis and tumour invasion. However, the expression and role of HN1L in breast cancer remain to be investigated. Here, bioinformatics, western blot and immunohistochemistry were used to detect the expression of HN1L in breast cancer. Wound healing, transwell assay, immunofluorescence assay and mass spectrum were used to explore the role and mechanism of HN1L on the migration and invasion of breast cancer, which was confirmed in vivo using a nude mice model. Results showed that HN1L was significantly over-expressed in breast cancer tissues, which was positively correlated with M metastasis of breast cancer patients. Silencing HN1L significantly inhibited the invasion and metastasis of breast cancer cells in vitro and lung metastasis in nude mice metastasis model of breast cancer. Mechanistically, HN1L interacted with HSPA9 and affected the expression of HMGB1, playing a key role in promoting the invasion and metastasis of breast cancer cell. These results suggested that HN1L was an appealing drug target for breast cancer. 相似文献
128.
Beta‐diversity metrics of the upper digestive tract microbiome are associated with body mass index 下载免费PDF全文
129.
林可链霉菌黑色素生物合成基因的克隆与表达 总被引:2,自引:0,他引:2
以pIJ702的melCl-C2基因为探针杂交林可链霉菌(Streptomyceslincolnensis)78-11染色体DNA,呈现出3.2kb的BamHI片段和2.6kb的SphI片段等一系列阳性条带。构建了含3.0~3.5kbBamHI片段的林可链霉菌78-11基因文库,从中分离克隆了黑色素生物合成基因melCl和melC2,并测定了含有mel基因的重组子pRSB336插入片段的全部DNA顺序。3152bpBamHI片段含有5个开放阅读框架,其中melCl和melC2与链霉菌属三个种的相应基因具有较高的同源性。此外,林可链霉菌78-11的melC2基因产物与人和鼠的酪氨酸酶轻微同源,分别为17.3%和24.5%。种种迹象表明,melCl、melC2和orf3组成黑色素生物合成操纵子结构。为了进一步鉴定上述克隆的林可链霉菌78-11黑色素生物合成基因,构建了分别含有新霉素抗性基因启动子和正反方向mel基因的重组质粒pPZ518和pPZ519,并转化变铅青链霉菌TK23。随机挑选的12个pPZ518转化子在R2YE培养基上均能分泌淡褐色色素,而所有的pPZ519和pES1转化子则都呈白色。 相似文献
130.