全文获取类型
收费全文 | 1402篇 |
免费 | 56篇 |
专业分类
1458篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 20篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 27篇 |
2017年 | 25篇 |
2016年 | 33篇 |
2015年 | 53篇 |
2014年 | 57篇 |
2013年 | 110篇 |
2012年 | 118篇 |
2011年 | 119篇 |
2010年 | 73篇 |
2009年 | 57篇 |
2008年 | 90篇 |
2007年 | 84篇 |
2006年 | 80篇 |
2005年 | 78篇 |
2004年 | 84篇 |
2003年 | 73篇 |
2002年 | 83篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 20篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 1篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1969年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有1458条查询结果,搜索用时 0 毫秒
11.
Yuichi Takeuchi Reiko Fukumoto Hirokazu Kasahara Takeshi Sakaki Mitsutoshi Kitao 《Plant cell reports》1995,14(9):566-570
Cotyledons excised from dark-grown seedlings of cucumber (Cucumis sativus L.) were cultured in vitro under UV radiation at different wavelengths, obtained by passage of light through cut-off filters with different transmittance properties. Growth and the synthesis of chlorophyll (Chl) in cotyledons were inhibited and malondialdehyde was accumulated upon irradiation at wavelengths below 320 nm. Exogenous application of scavengers of free radicals reversed the growth inhibition induced by UV-B. Measurement of the fluorescence of Chl a suggested that electron transfer in photosystems was affected by UV-B irradiation. On the basis of these results, the involvement is postulated of active species of oxygen in damages to thylakoid membranes and the growth inhibition that are induced by UV-B irradiation.Abbreviations Chl
chlorophyll
- Fm
maximal fluorescence (dark)
- Fm
maximal fluorescence (light)
- Fv
variable fluorescence (dark)
- Fv
variable fluorescence (light)
- MDA
malondialdehyde
- O2
Superoxide radical
- PS
photosystem
- qN
non-photochemical quenching of fluorescence
- qP
photochemical quenching of fluorescence
- UV-BBE
biologically effective UV-B radiation
- WL(T = 0.5)
wavelength at which 50% transmittance occurs 相似文献
12.
Takamichi Ichinose Akira K. Suzuki Hirokazu Tsubone Masaru Sagai 《Life sciences》1982,31(18):1963-1972
Strain differences of mice in their susceptibility to nitrogen dioxide (NO2) were examined by measuring the activities of antioxidative protective enzymes, and the amounts of antioxidants and lipid peroxides in lungs. Four strains of mice: ICR, BALB/c, ddy and C57BL/6 were used in this study and their LC50 values after exposure to NO2 for 16 hr were: 38, 49, 51 and 64 ppm, respectively (1).Genetic strain differences were observed in the enzyme activities, the antioxidant contents and lipid peroxide contents among these four different strains. The activities of glutathione peroxidase (GPx), glutathione S-transferase, and superoxide dismutase (SOD), and the contents of non-protein sulfhydryls (NPSH), α-tocopherol (α-Toc) and total lipids in lungs of the four strains were related to their LC50, while TBA reactants in lungs of the four strains were inversely related to their LC50.After exposure to 20 ppm NO2 for 16 hr, the activities of the protective enzymes and the contents of NPSH decreased, while the level of α-Toc increased markedly. The activities of GPx, 6-phosphogluconate dehydrogenase, SOD and disulfide reductase, and the contents of NPSH, α-Toc and total lipids were also related to their LC50. On the other hand, TBA reactants increased higher than those of the control groups and were inversely related to their LC50.These results suggest that the protective enzymes and the antioxidants are important factors as defence mechanism in lungs to NO2 and that the intensity of the protective systems in pigmented strains is generally greater than that in albino strains. 相似文献
13.
When methylmercury was incubated in the presence of selenite and reduced glutathione (GSH), the mercury which was extracted into benzene under acidic condition decreased gradually with the elapse of time. This decrease was due to the cleavage of mercury-carbon bond of methylmercury. The reaction did not proceed when selenite or GSH was singly added to the reaction mixture. L-Cysteine, 2-mercaptoethanol and sodium sulfide in place of GSH also were effective for decomposition of methylmercury in combination with selenite, but oxidized glutathione (GSSG) and L-cystine were not. This suggests that reduction of selenite is needed for the degradation of methylmercury. Thus, the effect of reduced metabolites of selenite produced by GSH was investigated. Glutathione selenotrisulfide (GSSeSG) requierd GSH for the degradation of methylmercury, whereas H2Se possessed a strong activity even in the absence of GSH. This may indicate that H2Se is involved directly in the conversion of methylmercury to inorganic mercury. This phenomenon found in experiments is discussed in relation to the biotransformation of methylmercury. 相似文献
14.
[35S]Methionine-labeled free subunits A and B of RuBP carboxylase were present in barely detectable amounts; the radioactivity in the free subunit B was approximately 1/150th of that in the subunit B contained in the holoenzyme of RuBP carboxylase. The turnover rates of subunits A and B in the holoenzyme were equal at each time during the incubation period. The ratio of subunit A to subunit B was constant throughout the incubation time both in quantity and in the level of [3H]leucine and [35S]methionine incorporated. CO2 contained in the incubation medium suppressed [35S]methionine incorporation into both subunits A and B equally. These results suggest that the biosynthesis of subunits A and B is completely synchronized and may be regulated by identical mechanisms. 相似文献
15.
Hirokazu Yamamoto Kunimoto Hotta Yoshiro Okami Hamao Umezawa 《Biochemical and biophysical research communications》1981,100(3):1396-1401
SS-939 was resistant to its own aminoglycoside antibiotics, istamycins, as well as kanamycin A, neamine, ribostamycin and butirosin A, but was susceptible to neomycin B, lividomycin A and streptomycin. This resistance to these antibiotics was found to be due to ribosomes of the strain. 相似文献
16.
Temperature-sensitive (ts) mutants of rat 3Y1 fibroblasts representing four separate complementation groups (3Y1tsD123, 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) are arrested mainly in the G1 phase when cells of randomly proliferating population at 33.8 degrees C are shifted to 39.8 degrees C (temperature arrest). We examined the time lag of the cellular entry into the S phase after release at 33.8 degrees C, both from the temperature arrest and from the arrest at 33.8 degrees C at a confluent cell density (density arrest). In the temperature-arrested cells, as the duration of temperature arrest increased, the time lag of entry into S phase after shift down to 33.8 degrees C was prolonged, in all four mutants. These observations suggest that the four different functional lesions, each causing arrest in the G1 phase, are also responsible for prolongation of the time lag of entry into the S phase in cells arrested in the G1 phase. The prolongation of the time lag in the temperature-arrested cultures was accelerated at a higher cell density, in medium supplemented with a lower concentration of serum, and at a higher restrictive temperature. In the density-arrested cells, as the duration of pre-exposure to 39.8 degrees C was increased, the time lag of entry into S phase at 33.8 degrees C after release from the arrest was drastically prolonged, in all four mutants. In 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203, when the density-arrested cells were prestimulated by serum at 39.8 degrees C for various periods of time, the time lag of entry into S phase after release from the density arrest at 33.8 degrees C was initially shortened, and then, prolonged progressively as the period of prestimulation increased. These findings, taken together with other data, show that all four ts defects affect cells in states ranging from the deeper resting to mid- or late-G1 phase. It is suggested that events represented by these four mutants are required for entry into the S phase and normally operate in parallel but not in sequence in cells in states ranging from the deeper resting to the mid- or late-G1 phases, though they may affect each other. 相似文献
17.
18.
Characterization of the Replication, Maintenance, and Transfer Features of the IncP-7 Plasmid pCAR1, Which Carries Genes Involved in Carbazole and Dioxin Degradation 总被引:4,自引:0,他引:4 下载免费PDF全文
Masaki Shintani Hirokazu Yano Hiroshi Habe Toshio Omori Hisakazu Yamane Masataka Tsuda Hideaki Nojiri 《Applied microbiology》2006,72(5):3206-3216
Isolated from Pseudomonas resinovorans CA10, pCAR1 is a 199-kb plasmid that carries genes involved in the degradation of carbazole and dioxin. The nucleotide sequence of pCAR1 has been determined previously. In this study, we characterized pCAR1 in terms of its replication, maintenance, and conjugation. By constructing miniplasmids of pCAR1 and testing their establishment in Pseudomonas putida DS1, we show that pCAR1 replication is due to the repA gene and its upstream DNA region. The repA gene and putative oriV region could be separated in P. putida DS1, and the oriV region was determined to be located within the 345-bp region between the repA and parW genes. Incompatibility testing using the minireplicon of pCAR1 and IncP plasmids indicated that pCAR1 belongs to the IncP-7 group. Monitoring of the maintenance properties of serial miniplasmids in nonselective medium, and mutation and complementation analyses of the parWABC genes, showed that the stability of pCAR1 is attributable to the products of the parWAB genes. In mating assays, the transfer of pCAR1 from CA10 was detected in a CA10 derivative that was cured of pCAR1 (CA10dm4) and in P. putida KT2440 at frequencies of 3 × 10−1 and 3 × 10−3 per donor strain, respectively. This is the first report of the characterization of this completely sequenced IncP-7 plasmid. 相似文献
19.
20.
Yoshikazu Hashida Katsuaki Takechi Tomomi Abiru Noriyuki Yabe Hiroaki Nagase Koro Hattori Susumu Takio Yoshikatsu Sato Mitsuyasu Hasebe Hirokazu Tsukaya Hiroyoshi Takano 《The Plant journal : for cell and molecular biology》2020,101(6):1318-1330
In Arabidopsis thaliana the ANGUSTIFOLIA (AN) gene regulates the width of leaves by controlling the diffuse growth of leaf cells in the medio‐lateral direction. In the genome of the moss Physcomitrella patens, we found two normal ANs (PpAN1‐1 and 1‐2). Both PpAN1 genes complemented the A. thaliana an‐1 mutant phenotypes. An analysis of spatiotemporal promoter activity of each PpAN1 gene, using transgenic lines that contained each PpAN1‐promoter– uidA (GUS) gene, showed that both promoters are mainly active in the stems of haploid gametophores and in the middle to basal region of the young sporophyte that develops into the seta and foot. Analyses of the knockout lines for PpAN1‐1 and PpAN1‐2 genes suggested that these genes have partially redundant functions and regulate gametophore height by controlling diffuse cell growth in gametophore stems. In addition, the seta and foot were shorter and thicker in diploid sporophytes, suggesting that cell elongation was reduced in the longitudinal direction, whereas no defects were detected in tip‐growing protonemata. These results indicate that both PpAN1 genes in P. patens function in diffuse growth of the haploid and diploid generations but not in tip growth. To visualize microtubule distribution in gametophore cells of P. patens, transformed lines expressing P. patens α‐tubulin fused to sGFP were generated. Contrary to expectations, the orientation of microtubules in the tips of gametophores in the PpAN1‐1/1‐2 double‐knockout lines was unchanged. The relationships among diffuse cell growth, cortical microtubules and AN proteins are discussed. 相似文献