全文获取类型
收费全文 | 11209篇 |
免费 | 944篇 |
国内免费 | 1606篇 |
专业分类
13759篇 |
出版年
2024年 | 52篇 |
2023年 | 214篇 |
2022年 | 472篇 |
2021年 | 696篇 |
2020年 | 524篇 |
2019年 | 628篇 |
2018年 | 504篇 |
2017年 | 394篇 |
2016年 | 521篇 |
2015年 | 749篇 |
2014年 | 890篇 |
2013年 | 885篇 |
2012年 | 1096篇 |
2011年 | 946篇 |
2010年 | 560篇 |
2009年 | 508篇 |
2008年 | 617篇 |
2007年 | 464篇 |
2006年 | 439篇 |
2005年 | 390篇 |
2004年 | 366篇 |
2003年 | 273篇 |
2002年 | 256篇 |
2001年 | 203篇 |
2000年 | 172篇 |
1999年 | 153篇 |
1998年 | 117篇 |
1997年 | 96篇 |
1996年 | 70篇 |
1995年 | 90篇 |
1994年 | 59篇 |
1993年 | 51篇 |
1992年 | 52篇 |
1991年 | 42篇 |
1990年 | 39篇 |
1989年 | 46篇 |
1988年 | 25篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1950年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
151.
152.
Qu XW Liu WP Qi ZY Duan ZJ Zheng LS Kuang ZZ Zhang WJ Hou YD 《Biochemical and biophysical research communications》2008,365(1):158-163
Human bocavirus (HBoV) is a new parvovirus first discovered in 2005, which is associated with acute respiratory infection. Analysis of sequence homology has revealed that a putative phospholipase A2 (PLA2) motif exists in the VP1 unique region of HBoV. However, little is known about whether the VP1 unique region of HBoV has PLA2 enzymatic activity and how these critical residues contribute to its PLA2 activity. To address these issues, the VP1 unique region protein and four of its mutants, were expressed in Eschericha coli. The purified VP1 unique protein (VP1U) showed a typical Ca2+-dependent secreted PLA2-like (sPLA2) activity, which was inhibited by sPLA2-specific inhibitors in a time-dependent manner. Mutation of one of the amino acids (21Pro, 41His, 42Asp or 63Asp) in VP1U almost eliminated the sPLA2 activity of HBoV VP1U. These data indicate that VP1U of HBoV has sPLA2-like enzymatic activity, and these residues are crucial for its sPLA2-like activity. Potentially, VP1U may be a target for the development of anti-viral drugs for HBoV. 相似文献
153.
154.
Min Wu Qi Shen Yong Yang Sheng Zhang Wen Qu Jing Chen Hongying Sun Shuqing Chen 《Journal of industrial microbiology & biotechnology》2013,40(6):589-599
Human serum albumin (HSA) and human parathyroid hormone (1-34) [PTH (1-34)] fusion protein [HSA/PTH (1-34)] is a promising long-acting form of PTH (1-34) for osteoporosis treatment. Secretory expression of intact HSA/PTH (1-34) in Pichia pastoris GS115 was accompanied by two degradation fragments, with molecular weights around 66 kDa, in addition to the well-known ~45 kDa HSA-truncated fragment, resulting in a low yield of intact protein. In this study, two internal cleavage sites were identified in the PTH (1-34) portion of the fusion protein by Western Blot analysis. To minimize proteolytic cleavages, several protease genes including PEP4 (encoding proteinase A), PRB1 (proteinase B) and seven YPSs genes (yapsin family members) were knocked out respectively by disruption of the individual genes and the selective combinations. Reduced degradation was observed by single disruption of either PEP4 gene or YPS1 gene, and the lowest level of degradation was observed in a pep4△yps1△ double disruptant. After 72 h of induction, more than 80 % of the HSA/PTH (1-34) secreted by the pep4△yps1△ double disruptant remained intact, in comparison to only 30 % with the wild-type strain. 相似文献
155.
微卫星(TATG)n基序在香菇菌种中的验证 总被引:10,自引:0,他引:10
以(TATG)4重复序列为引物对香菇属的3个种13个菌株的微卫星区DNA进行PCR扩增,15%的琼脂糖凝胶电泳,获得了25个条带,并且在供试菌株上表现出多态性,可以实现遗传分类研究。为了验证微卫星分子标记实验准确性,又用RAPD技术对13个供试菌株进行了实验。7个引物在13个菌株上共获得了102条多态性条带。通过聚类分析,RAPD获得的分类结果与微卫星分子标记获得的结果一致。此外,为了证明微卫星分子标记获得的条带不是假阳性,在实验中回收了No.10菌株的PCR扩增产物,进行克隆测序。测序结果显示有(TATG)n基序存在,并且达到了微卫星基序重复数量的最低限度。通过本实验可知,香菇中是存在微卫星(TATG)n基序的, 且基序的多态性可以用于香菇的遗传分类研究。 相似文献
156.
157.
158.
多胺作为生理活性物质与植物衰老关系密切。本文综述了近十多年来多胺对衰老的调控作用,从调节细胞膜的理化性质、生物大分子合成作用以及多胺与乙烯的关系等方面阐述了多胺延缓衰老的机制,比较了多胺和影响衰老的植物激素在信号转导过程中的作用。 相似文献
159.
广西陆栖兽类动物分布格局及区划探讨 总被引:3,自引:0,他引:3
根据广西陆栖兽类种类,数量和分布特点。结合自然地理条件,探讨了广西陆栖兽类支持发布格局,并将广西兽类地理区划为7个小区:Ⅰ桂西南缘山地小区;Ⅱ桂南沿海台地平原小区;Ⅲ桂西南丘陵盆地小区;Ⅳ桂中丘陵山地小区;Ⅴ桂中及桂东低丘台地,山地,谷地小区;Ⅵ桂西北岩溶山原盆坝小区;Ⅶ桂东北南岭山地小区。广西陆栖兽类区域分化不明显,而受地形因素的更显著,海拔较高的桂西,北边缘山地区系成分较为近似,而与东部和南部沿海低海拔的丘陵,低山及盆地形成较明显的差异。盆地内弧形山脉的动物区系别具特色。 相似文献
160.
Sun YN Pan JB Shi XL Du XY Wu Q Qi ZM Jiang HW Xin DW Liu CY Hu GH Chen QS 《Molecular biology reports》2012,39(10):9435-9443
100-Seed weight (100-SW) of soybean is an important but complicated quantitative trait to yield. This study was focus on the quantitative trait loci (QTLs) of soybean 100-SW from 2006 to 2010, using recombination inbred lines population that was derived from a cross between Charleston and Dongnong 594. A total of 23 QTLs for 100-SW were detected in the linkage group C2, D1a, F, G and O. Nine QTLs were identified by composite interval mapping including one QTL with the minimum confidence interval (CI) of 1.3?cM, while 14 QTLs by multiple interval mapping. Furthermore, 94 reported QTLs of 100-SW were integrated with our QTL mapping results using BioMercator. As a result, 15 consensus QTLs and their corresponding markers were identified. The minimum CI was reduced to 1.52?cM by the combination of meta-analysis. These findings may merit fine-mapping of these QTL in soybean. 相似文献