全文获取类型
收费全文 | 2388篇 |
免费 | 109篇 |
国内免费 | 3篇 |
出版年
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 26篇 |
2015年 | 38篇 |
2014年 | 73篇 |
2013年 | 389篇 |
2012年 | 93篇 |
2011年 | 121篇 |
2010年 | 90篇 |
2009年 | 62篇 |
2008年 | 136篇 |
2007年 | 136篇 |
2006年 | 124篇 |
2005年 | 154篇 |
2004年 | 160篇 |
2003年 | 139篇 |
2002年 | 147篇 |
2001年 | 22篇 |
2000年 | 10篇 |
1999年 | 26篇 |
1998年 | 28篇 |
1997年 | 25篇 |
1996年 | 32篇 |
1995年 | 24篇 |
1994年 | 13篇 |
1993年 | 22篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 30篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 6篇 |
1972年 | 5篇 |
排序方式: 共有2500条查询结果,搜索用时 15 毫秒
961.
Sister Chromatid Exchanges Are Mediated by Homologous Recombination in Vertebrate Cells 总被引:9,自引:0,他引:9 下载免费PDF全文
Eiichiro Sonoda Masao S. Sasaki Ciaran Morrison Yuko Yamaguchi-Iwai Minoru Takata Shunichi Takeda 《Molecular and cellular biology》1999,19(7):5166-5169
Sister chromatid exchange (SCE) frequency is a commonly used index of chromosomal stability in response to environmental or genetic mutagens. However, the mechanism generating cytologically detectable SCEs and, therefore, their prognostic value for chromosomal stability in mitotic cells remain unclear. We examined the role of the highly conserved homologous recombination (HR) pathway in SCE by measuring SCE levels in HR-defective vertebrate cells. Spontaneous and mitomycin C-induced SCE levels were significantly reduced for chicken DT40 B cells lacking the key HR genes RAD51 and RAD54 but not for nonhomologous DNA end-joining (NHEJ)-defective KU70(-/-) cells. As measured by targeted integration efficiency, reconstitution of HR activity by expression of a human RAD51 transgene restored SCE levels to normal, confirming that HR is the mechanism responsible for SCE. Our findings show that HR uses the nascent sister chromatid to repair potentially lethal DNA lesions accompanying replication, which might explain the lethality or tumorigenic potential associated with defects in HR or HR-associated proteins. 相似文献
962.
Rina Fujihara Naoyuki Uchida Toshiaki Tameshige Nozomi Kawamoto Yugo Hotokezaka Takumi Higaki Rüdiger Simon Keiko U Torii Masao Tasaka Mitsuhiro Aida 《Plant Biotechnology》2021,38(3):317
The shoot organ boundaries have important roles in plant growth and morphogenesis. It has been reported that a gene encoding a cysteine-rich secreted peptide of the EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) family, EPFL2, is expressed in the boundary domain between the two cotyledon primordia of Arabidopsis thaliana embryo. However, its developmental functions remain unknown. This study aimed to analyze the role of EPFL2 during embryogenesis. We found that cotyledon growth was reduced in its loss-of-function mutants, and this phenotype was associated with the reduction of auxin response peaks at the tips of the primordia. The reduced cotyledon size of the mutant embryo recovered in germinating seedlings, indicating the presence of a factor that acted redundantly with EPFL2 to promote cotyledon growth in late embryogenesis. Our analysis suggests that the boundary domain between the cotyledon primordia acts as a signaling center that organizes auxin response peaks and promotes cotyledon growth. 相似文献
963.
964.
965.
Hideo Ochiai Hitoshi Shibata Tetsu Matsuo Kenji Hashinokuchi Masao Yukawa 《Bioscience, biotechnology, and biochemistry》2013,77(4):721-722
Highly branched α-glucan molecules exhibit low digestibility for α-amylase and glucoamylase, and abundant in α-(1→3)-, α-(1→6)-glucosidic linkages and α-(1→6)-linked branch points where another glucosyl chain is initiated through an α-(1→3)-linkage. From a culture supernatant of Paenibacillus sp. PP710, we purified α-glucosidase (AGL) and α-amylase (AMY), which were involved in the production of highly branched α-glucan from maltodextrin. AGL catalyzed the transglucosylation reaction of a glucosyl residue to a nonreducing-end glucosyl residue by α-1,6-, α-1,4-, and α-1,3-linkages. AMY catalyzed the hydrolysis of the α-1,4-linkage and the intermolecular or intramolecular transfer of maltooligosaccharide like cyclodextrin glucanotransferase (CGTase). It also catalyzed the transfer of an α-1,4-glucosyl chain to a C3- or C4-hydroxyl group in the α-1,4- or α-1,6-linked nonreducing-end residue or the α-1,6-linked residue located in the other chains. Hence AMY was regarded as a novel enzyme. We think that the mechanism of formation of highly branched α-glucan from maltodextrin is as follows: α-1,6- and α-1,3-linked residues are generated by the transglucosylation of AGL at the nonreducing ends of glucosyl chains. Then AMY catalyzes the transfer of α-1,4-chains to C3- or C4-hydroxyl groups in the α-1,4- or α-1,6-linked residues generated by AGL. Thus the concerted reactions of both AGL and AMY are necessary to produce the highly branched α-glucan from maltodextrin. 相似文献
966.
967.
Hidehito Urata Masayuki Urata Masao Akagi Hidekazu Hiroaki Seiich Uesugi 《Nucleosides, nucleotides & nucleic acids》2013,32(6-7):1259-1269
Abstract We investigated the structure of a decadeoxynucleotide duplex which was modified with Dichloroethylenediamineplatinum(II) (PtCl2(en)) at the central GG site by using some spectroscopic techniques. The results suggest that the DNA structural changes induced by binding of PtCl2(en) are quite similar to those of cisplatin. 相似文献
968.
Sera Toshihiro Kobayashi Hiroaki Hoshino Masato Uesugi Kentaro Matsumoto Takeshi Tanaka Masao 《Biomechanics and modeling in mechanobiology》2019,18(2):375-385
Biomechanics and Modeling in Mechanobiology - In this study, based on the measurements of intracortical vascular canal structure, we investigated the disuse effect on local O2 supply in the... 相似文献
969.
970.