全文获取类型
收费全文 | 2304篇 |
免费 | 140篇 |
国内免费 | 1篇 |
专业分类
2445篇 |
出版年
2023年 | 11篇 |
2022年 | 22篇 |
2021年 | 55篇 |
2020年 | 18篇 |
2019年 | 32篇 |
2018年 | 58篇 |
2017年 | 54篇 |
2016年 | 80篇 |
2015年 | 122篇 |
2014年 | 113篇 |
2013年 | 164篇 |
2012年 | 212篇 |
2011年 | 151篇 |
2010年 | 120篇 |
2009年 | 83篇 |
2008年 | 120篇 |
2007年 | 120篇 |
2006年 | 106篇 |
2005年 | 101篇 |
2004年 | 69篇 |
2003年 | 65篇 |
2002年 | 66篇 |
2001年 | 60篇 |
2000年 | 60篇 |
1999年 | 39篇 |
1998年 | 26篇 |
1997年 | 15篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 19篇 |
1991年 | 22篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1973年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有2445条查询结果,搜索用时 0 毫秒
81.
Ana Paula Kallaur Josiane Lopes Sayonara Rangel Oliveira Andrea Name Colado Simão Edna Maria Vissoci Reiche Elaine Regina Delicato de Almeida Helena Kaminami Morimoto Wildea Lice Carvalho Jennings de Pereira Daniele Frizon Alfieri Sueli Donizete Borelli Domacio Ramon Kaimen-Maciel Michael Maes 《Molecular neurobiology》2016,53(8):5191-5202
82.
83.
84.
Pereira Felipe Walter Vitule Jean Ricardo Simões 《Reviews in Fish Biology and Fisheries》2019,29(3):639-652
Reviews in Fish Biology and Fisheries - Biological invasions via anthropogenic vectors, intentional or not, are one of the main causes of ecological change in aquatic ecosystems. Micropterus... 相似文献
85.
The synthesis of chain-modified analogues of the naturally-occurring glycosidase inhibitor, salacinol, and its selenium analogue, blintol is described. The modification consists of a frame shift of the sulfate moiety by one carbon atom in the zwitterionic structures as well as an extension of the acyclic chain to five carbons. The target molecules were synthesized by alkylation of 1,4-anhydro-2,3,5-tri-O-p-methoxybenzyl-4-thio (or seleno)-D-arabinitol at the ring heteroatom by 2,3,5-tri-O-p-methoxybenzyl D- or L-xylitol-1,4-cyclic sulfate, followed by deprotection with trifluoroacetic acid. Two of the four compounds inhibit recombinant human maltase glucoamylase, one of the key intestinal enzymes involved in the breakdown of glucose oligosaccharides in the small intestine, with Ki values of 20+/-4 and 53+/-5 microM. 相似文献
86.
87.
Characterization of recombinant CDR1, an Arabidopsis aspartic proteinase involved in disease resistance 总被引:1,自引:0,他引:1
The Arabidopsis thaliana constitutive disease resistance 1 (CDR1) gene product is an aspartic proteinase that has been implicated in disease resistance signaling (Xia, Y., Suzuki, H., Borevitz, J., Blount, J., Guo, Z., Patel, K., Dixon, R. A., and Lamb, C. (2004) EMBO J. 23, 980-988). This apoplastic enzyme is a member of the group of "atypical" plant aspartic proteinases. As for other enzymes of this subtype, CDR1 has remained elusive until recently as a result of its unusual properties and localization. Here we report on the heterologous expression and characterization of recombinant CDR1, which displays unique enzymatic properties among plant aspartic proteinases. The highly restricted specificity requirements, insensitivity toward the typical aspartic proteinase inhibitor pepstatin A, an unusually high optimal pH of 6.0-6.5, proteinase activity without irreversible prosegment removal, and dependence of catalytic activity on formation of a homo-dimer are some of the unusual properties observed for recombinant CDR1. These findings unveil a pattern of unprecedented functional complexity for Arabidopsis CDR1 and are consistent with a highly specific and regulated biological function. 相似文献
88.
89.
A novel tandem solvent process of dodecane and methanol was developed for the selective extraction of free astaxanthin from red encysted Haematococcus culture. The process consists of dodecane extraction for astaxanthin mixture from the culture (stage 1) and methanol extraction for free astaxanthin from the dodecane extract (stage 2). In the first stage, astaxanthin mixture was directly extracted to dodecane from the culture broth without cell harvest process, followed by a rapid separation of the dodecane extract and the culture medium containing cell debris by simple settling. In the second stage, free astaxanthin was selectively collected to methanol from the dodecane extract, accompanied with saponification of astaxanthin-esters by the addition of NaOH to methanol. During saponification, use of the optimum NaOH concentration (0.02 M) and low temperature (4 degrees C) reaction minimized the degradation of free astaxanthin, resulting in a total recovery yield of free astaxanthin of over 85%. The free-astaxanthin-containing methanol extract was also simply separated from dodecane by gravity settling, after which the astaxanthin-free dodecane was effectively recycled to the first stage, yielding a stable extractability of astaxanthin mixture during repeated extraction. Our results indicate the potential of the proposed tandem solvent process as an alternative extraction technology for the high-value antioxidant Haematococcus astaxanthin. 相似文献
90.
de Jesus Santana Mayla Barbosa-Júnior Sebastião Martins Dias Lana Laene Lima Silva Lázara Aline Simões da Silva Givanildo Zildo Fortini Evandro Alexandre Batista Diego Silva Otoni Wagner Campos da Costa Netto Antônio Paulino Rocha Diego Ismael 《In vitro cellular & developmental biology. Plant》2022,58(6):865-875
In Vitro Cellular & Developmental Biology - Plant - The aim of this study was to establish a system of in vitro germination and propagation of Guazuma ulmifolia Lam. microcuttings (Malvaceae).... 相似文献