全文获取类型
收费全文 | 1663篇 |
免费 | 117篇 |
出版年
2022年 | 13篇 |
2021年 | 18篇 |
2020年 | 8篇 |
2019年 | 17篇 |
2018年 | 19篇 |
2017年 | 13篇 |
2016年 | 25篇 |
2015年 | 35篇 |
2014年 | 63篇 |
2013年 | 91篇 |
2012年 | 103篇 |
2011年 | 89篇 |
2010年 | 52篇 |
2009年 | 67篇 |
2008年 | 96篇 |
2007年 | 96篇 |
2006年 | 64篇 |
2005年 | 97篇 |
2004年 | 74篇 |
2003年 | 79篇 |
2002年 | 73篇 |
2001年 | 37篇 |
2000年 | 52篇 |
1999年 | 48篇 |
1998年 | 27篇 |
1997年 | 20篇 |
1996年 | 21篇 |
1995年 | 8篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 27篇 |
1991年 | 31篇 |
1990年 | 23篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1970年 | 7篇 |
1968年 | 6篇 |
排序方式: 共有1780条查询结果,搜索用时 15 毫秒
891.
Purification of Cytochrome P450 and Ferredoxin, Involved in Bisphenol A Degradation, from Sphingomonas sp. Strain AO1 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Miho Sasaki Ayako Akahira Ko-ichi Oshiman Tetsuaki Tsuchido Yoshinobu Matsumura 《Applied microbiology》2005,71(12):8024-8030
In a previous study (M. Sasaki, J. Maki, K. Oshiman, Y. Matsumura, and T. Tsuchido, Biodegradation 16:449-459, 2005), the cytochrome P450 monooxygenase system was shown to be involved in bisphenol A (BPA) degradation by Sphingomonas sp. strain AO1. In the present investigation, we purified the components of this monooxygenase, cytochrome P450 (P450bisd), ferredoxin (Fdbisd), and ferredoxin reductase (Redbisd). We demonstrated that P450bisd and Fdbisd are homodimeric proteins with molecular masses of 102.3 and 19.1 kDa, respectively, by gel filtration chromatography analysis. Spectroscopic analysis of Fdbisd revealed the presence of a putidaredoxin-type [2Fe-2S] cluster. P450bisd, in the presence of Fdbisd, Redbisd, and NADH, was able to convert BPA. The Km and kcat values for BPA degradation were 85 ± 4.7 μM and 3.9 ± 0.04 min−1, respectively. NADPH, spinach ferredoxin, and spinach ferredoxin reductase resulted in weak monooxygenase activity. These results indicated that the electron transport system of P450bisd might exhibit strict specificity. Two BPA degradation products of the P450bisd system were detected by high-performance liquid chromatography analysis and were thought to be 1,2-bis(4-hydroxyphenyl)-2-propanol and 2,2-bis(4-hydroxyphenyl)-1-propanol based on mass spectrometry-mass spectrometry analysis. This is the first report demonstrating that the cytochrome P450 monooxygenase system in bacteria is involved in BPA degradation. 相似文献
892.
Comparison of Whole System of Carbon and Nitrogen Accumulation Between Two Maize Hybrids Differing in Leaf Senescence 总被引:2,自引:0,他引:2
A field experiment was conducted to investigate the carbon (C) and nitrogen (N) balance in relation to grain formation and leaf senescence in two different senescent types of maize (Zea mays L.), one stay-green (cv. P3845) and one earlier senescent (cv. Hokkou 55). In comparison with Hokkou 55, P3845 had a higher N concentration (Nc) in the leaves and a higher specific N absorption rate by roots (SARN), which indicated that a large amount of N was supplied to the leaves from the roots during maturation. This resulted in a higher photosynthetic rate, which supports saccharide distribution to roots. Thus, stay-green plants maintained a more balanced C and N metabolism between shoots and roots. Moreover, the coefficients of the relationship between the relative growth rate (RGR) and Nc, and between the photon-saturated photo-synthetic rate (P
sat) and Nc were lower in P3845. The P
sat per unit Nc in leaves was lower in the stay-green cultivars, which indicated that high yield was attained by longer green area duration and not by a high P
sat per unit Nc in the leaf. Consequently, a high Psat caused a high leaf senescence rate because C and N compounds will translocate actively from the leaves. 相似文献
893.
Naoto Matsumura Naoko Yoshida Aya Ohta Yusei Miyamoto Tatsuhiro Hisatsune 《Cytotechnology》2003,43(1-3):19-25
Recent findings concerning adult neurogenesis in two selected structures of the mammalian brain, the olfactory bulb and dentate gyrus of the hippocampus, present the possibility that this mechanism of neurogenesis applies for all brain regions, including the cerebral neocortex. In this way, a small number of potential neural precursor cells may exist in the cerebral neocortex, but they do not normally differentiate into cortical neurons in vivo. It has, however, been reported recently that cycling cells isolated from non-neurogenic areas of adult rat cerebral cortex could generate neurons in vitro. In this study, we analyzed the lineage potential of cycling cells from the adult mouse neocortex. For the dissection of the cerebral cortex from the adult mouse, which is significantly smaller than that of the adult rat, we have modified the previous dissection protocol developed for the rat neocortex. As a result, cycling cells from adult mouse neocortex gave rise to neurons and oligodendrocytes, but not to astrocytes, whereas when the previous dissection method was used, cycling cells gave rise to neurons, oligodendrocytes and astrocytes. This discrepancy might stem from slight contamination of the dissected mouse neocortical tissue in the previous protocol used for the dissection of rat neocortex by cells from the surrounding subependymal zone, where typical adult neural stem cells exist. The results presented here will contribute to our understanding of the nature of cycling cells in the adult mammalian neocortex, and for which future stem cell research will provide new possibilities for cell replacement therapy to be used in the treatment of neurodegenerative conditions. 相似文献
894.
895.
Wheat catalase expressed in transgenic rice can improve tolerance against low temperature stress 总被引:2,自引:0,他引:2
Takeshi Matsumura Noriko Tabayashi Yasuyo Kamagata Chihiro Souma Haruo Saruyama 《Physiologia plantarum》2002,116(3):317-327
We examined whether the expression of wheat catalase (EC 1.11.1.6) cDNA in transgenic rice ( Oryza sativa L.) could enhance tolerance against low temperature injury. Transgenic rice plants expressing wheat CAT protein showed an increase of activities in leaves at 25°C, 2- to 5-fold that in non-transgenic rice. At 5°C, catalase activities were about 4–15 times higher than those in non-transgenic rice were. A comparison of damage observed in leaves as they withered due to chilling at 5°C showed that transgenic rice displayed an increased capability to resist low temperature stress. The exposure of these plants to low temperature at 5°C for 8 days resulted in decreased catalase activities in leaves at 25°C, but the transgenic plants indicated 4 times higher residual catalase activities than those of non-transgenic ones. The concentration of H2 O2 in leaves was kept lower in transgenic rice than that of the control plants during the 8 days chilling. These results suggest that the improved tolerance against low temperature stress in genetically engineered rice plants be attributed to the effective detoxification of H2 O2 by the enhanced catalase activities. 相似文献
896.
Takuro Kobayashi Daisuke Yasuda Yu-You Li Kengo Kubota Hideki Harada Han-Qing Yu 《Bioresource technology》2009,100(21):4981-4988
Successful start-up strategy for anaerobic digestion of waste-activated sludge using internal inoculum and relationship between the shift of methanogenic community and the digester performance during start-up was investigated. Combination of TS control of inoculum and batch operation during early days enabled the successful start-up operation without serious volatile fatty acid accumulation, followed by the stable continuous operation. However, the propionate degradation was rate-limiting step during the batch operation. The results of real-time quantitative polymerase chain reaction analysis suggested that there was a correlation between the population of the genus Methanosarcina and the methane production rate coupled with acetate consumption during batch operation, and the results of terminal-restriction fragment length polymorphism (T-RFLP) revealed that the increasing intensity of T-RF peaks of hydrogenotrophic methanogens was associated with a decrease in the level of C3-acids. 相似文献
897.
In the field of animal breeding, estimation of genetic parameters and prediction of breeding values are routinely conducted by analyzing quantitative traits. Using an animal model and including the direct inverse of a numerator relationship matrix (NRM) into a mixed model has made these analyses possible. However, a method including a genetically identical animal (GIA) in NRM if genetic relationships between pairs of GIAs are not perfect, is still lacking. Here, we describe a method to incorporate GIAs into NRM using a K matrix in which diagonal elements are set to 1.0, off-diagonal elements between pairs of GIAs to (1-x) and the other elements to 0, where x is a constant less than 0.05. The inverse of the K matrix is then calculated directly by a simple formula. Thus, the inverse of the NRM is calculated by the products of the lower triangular matrix that identifies the parents of each individual, its transpose matrix, the inverse of the K matrix and the inverse of diagonal matrix D, in which the diagonal elements comprise a number of known parents and their inbreeding coefficients. The computing method is adaptable to the analysis of a data set including pairs of GIAs with imperfect relationships. 相似文献
898.
899.
900.