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71.
Evidence of independent gene duplications during the evolution of archaeal and eukaryotic family B DNA polymerases 总被引:1,自引:0,他引:1
Eukaryotes and archaea both possess multiple genes coding for family B DNA
polymerases. In animals and fungi, three family B DNA polymerases, alpha,
delta, and epsilon, are responsible for replication of nuclear DNA. We used
a PCR-based approach to amplify and sequence phylogenetically conserved
regions of these three DNA polymerases from Giardia intestinalis and
Trichomonas vaginalis, representatives of early-diverging eukaryotic
lineages. Phylogenetic analysis of eukaryotic and archaeal paralogs
suggests that the gene duplications that gave rise to the three replicative
paralogs occurred before the divergence of the earliest eukaryotic
lineages, and that all eukaryotes are likely to possess these paralogs. One
eukaryotic paralog, epsilon, consistently branches within archaeal
sequences to the exclusion of other eukaryotic paralogs, suggesting that an
epsilon-like family B DNA polymerase was ancestral to both archaea and
eukaryotes. Because crenarchaeote and euryarchaeote paralogs do not form
monophyletic groups in phylogenetic analysis, it is possible that archaeal
family B paralogs themselves evolved by a series of gene duplications
independent of the gene duplications that gave rise to eukaryotic paralogs.
相似文献
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Nara O. Vogado Michael J. Liddell Susan G. W. Laurance Mason J. Campbell Alexander W. Cheesman Jayden E. Engert Ana C. Palma Françoise Y. Ishida Lucas A. Cernusak 《Journal of Plant Ecology》2020,13(6):744
据预测,人为气候变化将季节性地增加平均温度和降雨。热带雨林物种将如何应对这种气候变化仍不确定。本研究分析了对澳大利
亚昆士兰北部丹特里雨林的一种澳大利亚特有棕榈(Normambya normanbyi)进行4年降雨实验的影响,目的是了解模拟降雨减少对物种生理
过程和果实物候的影响。我们考察了这种本地丰富的棕榈的果实物候和生理生态学特性,以确定该物种对干旱的生态响应。2015年5月,
通过排涝实验,降低了约30%的土壤水分有效性。我们总共监测了8年(2009–2018年)的月度果实活性,包括排涝实验开始之前的4年。在最
近几年的研究中,我们测量了干、湿两季幼嫩和成熟叶片的光合速率、气孔导度和碳稳定同位素等生理参数。研究结果表明,所有棕榈树
的月度果实活性主要受光周期、平均太阳辐射和平均温度的驱动。然而,暴露于较低土壤水分的植株,其果实活性、光合速率和气孔导度
均显著下降。我们还发现这些生理表现受到排涝实验、季节以及两者的相互作用的影响。2018年观察到排涝实验的棕榈的果实活力有所恢复,土壤浅层水分也有所增加(与前几年相比)。我们的研究结果表明,像N. normanbyi 这样的棕榈树对未来的气候变化非常敏感,建议对其
进行长期监测,以确定其对种群规模的影响。 相似文献
75.
Although large-scale biodiversity declines are ongoing, certain conservation actions have made a positive difference. Rates of extinction and endangerment of vertebrate species, for instance, have probably been reduced via conservation interventions. Such conservation actions operate at different spatial scales. Habitat preservation and endangered species recovery are examples of conservation successes at microscales. Mesoscale conservation includes regional cooperation among neighboring countries that has arrested population declines of endangered species, such as mountain gorillas. At macroscales, public pressure on multinational corporations has sometimes resulted in their abandoning environmentally damaging practices or suppliers with poor environmental records. Overall, conservation projects such as these need more long-term funding and greater political and popular support, and must also include provisions to evaluate and document their outcomes. As we discuss here, a focus on conservation successes achieved at different scales can help to promote these aims and guide future conservation victories. 相似文献
76.
Laurance V. Foye Jr. Forrest M. Willett Byron Hall Merall Roth 《The Western journal of medicine》1960,93(5):288-290
A preliminary study of the response of various inoperable malignant diseases to simultaneously administered 5-fluoro-uracil and orthovolt x-ray was performed. The 5-fluoro-uracil was given intravenously at a relatively nontoxic dosage level. The x-ray tumor dose was limited to 2,000 roentgens in every patient.Pronounced and rapid tumor regression occurred in 12 of 18 evaluable patients. Significant objective response was obtained in each of eight patients with epidermoid carcinoma of the lung.Toxicity occurred in half of the patients, manifested by pharyngitis, esophagitis, proctitis, leukopenia and thrombocytopenia. 相似文献
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4-Deoxy-4-fluoro-α-
-sorbose (6) was prepared in crystalline form by the action of potassium hydrogen fluoride on 3,4-anhydro-1,2-O-isopropylidene-β-
-psicopyranose (3) followed by deacetonation. Under identical conditions 3,4-anhydro-1,2-O-isopropylidene-β-
-tagatopyranose (7) underwent epoxide migration to give 4,5-anhydro- 1,2-O-isopropylidene-β-
-fructopyranose (12), which after deacetonation yielded 4-deoxy-4-fluoro-
-tagatose (15) 5-deoxy-5-fluoro-α-
-sorbopyranose (16) the latter as the crystalline free sugar. The action of glycol-cleavage reagents on the isopropylidene acetals of the deoxyfluoro sugars was consistent with the assigned structures. The structures were established by 13C n.m.r. studies of the free deoxyfluoro sugars 6 and 16 of the isopropylidene acetal 13, and by 1H n.m.r. studies on the acetylated isopropylidene acetals 5 diacetate, 13 diacetate, and 14 diacetate. 5-Deoxy-5-fluoro-
-sorbose (16) was biologically active producing in mice effects characteristic of deoxyfluorotrioses and of fluoroacetate. 4-Deoxy-4-fluoro-
-tagatose (15) and 4-deoxy-4-fluoro-
-sorbose (6) produced no apparent effects in mice up to a dose of 500 mg/kg. The implications of these findings with respect to transport phosphorylation, and the action of aldolase on ketohexoses are discussed. 相似文献
80.
Valter M. Azevedo-Santos Philip M. Fearnside Caroline S. Oliveira André A. Padial Fernando M. Pelicice Dilermando P. LimaJr Daniel Simberloff Thomas E. Lovejoy André L. B. Magalhães Mario L. Orsi Angelo A. Agostinho Francisco A. Esteves Paulo S. Pompeu William F. Laurance Miguel PetrereJr Roger P. Mormul Jean R. S. Vitule 《Biodiversity and Conservation》2017,26(7):1745-1752
The executive and legislative branches of Brazilian government have either proposed or taken a variety of initiatives that threaten biodiversity and ecosystems. Opposition by the scientific community has largely been ignored by decision-makers. In this short essay, we present recent examples of harmful policies that have great potential to erode biodiversity, and we suggest ways to communicate scientific knowledge to decision- makers. If the current gap between conservation science and policies is not filled, the country will threaten the maintenance of its natural capital and, consequently, the sustainability of essential societal activities in the long term. 相似文献