全文获取类型
收费全文 | 100篇 |
免费 | 2篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1997年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有102条查询结果,搜索用时 31 毫秒
91.
92.
Recent finds of 36 ceramic artifacts from the archaeological site of Vela Spila, Croatia, offer the first evidence of ceramic figurative art in late Upper Palaeolithic Europe, c. 17,500-15,000 years before present (BP). The size and diversity of this artistic ceramic assemblage indicate the emergence of a social tradition, rather than more ephemeral experimentation with a new material. Vela Spila ceramics offer compelling technological and stylistic comparisons with the only other evidence of a developed Palaeolithic ceramic tradition found at the sites of Pavlov I and Dolní Věstonice I, in the Czech Republic, c. 31,000-27,000 cal BP. Because of the 10,000-year gap between the two assemblages, the Vela Spila ceramics are interpreted as evidence of an independent invention of this technology. Consequently, these artifacts provide evidence of a new social context in which ceramics developed and were used to make art in the Upper Palaeolithic. 相似文献
93.
Derek Shirley Cris Oppert Todd B. Reynolds Bethany Miracle Brenda Oppert William E. Klingeman Juan Luis Jurat‐Fuentes 《Insect Science》2014,21(5):609-618
Insects are a largely unexploited resource in prospecting for novel cellulolytic enzymes to improve the production of ethanol fuel from lignocellulosic biomass. The cost of lignocellulosic ethanol production is expected to decrease by the combination of cellulose degradation (saccharification) and fermentation of the resulting glucose to ethanol in a single process, catalyzed by the yeast Saccharomyces cerevisiae transformed to express efficient cellulases. While S. cerevisiae is an established heterologous expression system, there are no available data on the functional expression of insect cellulolytic enzymes for this species. To address this knowledge gap, S. cerevisiae was transformed to express the full‐length cDNA encoding an endoglucanase from the red flour beetle, Tribolium castaneum (TcEG1), and evaluated the activity of the transgenic product (rTcEG1). Expression of the TcEG1 cDNA in S. cerevisiae was under control of the strong glyceraldehyde‐3 phosphate dehydrogenase promoter. Cultured transformed yeast secreted rTcEG1 protein as a functional β‐1,4‐endoglucanase, which allowed transformants to survive on selective media containing cellulose as the only available carbon source. Evaluation of substrate specificity for secreted rTcEG1 demonstrated endoglucanase activity, although some activity was also detected against complex cellulose substrates. Potentially relevant to uses in biofuel production rTcEG1 activity increased with pH conditions, with the highest activity detected at pH 12. Our results demonstrate the potential for functional production of an insect cellulase in S. cerevisiae and confirm the stability of rTcEG1 activity in strong alkaline environments. 相似文献
94.
The fruit pulp of Tetrapleura tetraptera has yielded aridanin, a novel 3-O-[β-D-glucopyranosyl-2′-acetamido-2′-deoxy]-oleanolic acid. Hentriacontane, phenylpropanoids and carbohydrate residues were also isolated and identified. 相似文献
95.
Modupe F. Adesina Rita Grosch Antje Lembke Tzenko D. Vatchev & Kornelia Smalla 《FEMS microbiology ecology》2009,69(1):62-74
The rhizosphere competence of 15 in vitro antagonists of Rhizoctonia solani was determined 4 weeks after sowing inoculated lettuce seeds into nonsterile soil. Based on the colonization ability determined by selective plating, eight strains were selected for growth chamber experiments to determine their efficacy in controlling bottom rot caused by R. solani on lettuce. Although in the first experiment all antagonists colonized the rhizosphere of lettuce with CFU counts above 2 × 106 g−1 of root fresh weight, only four isolates significantly reduced disease severity. In subsequent experiments involving these four antagonists, only Pseudomonas jessenii RU47 showed effective and consistent disease suppression. Plate counts and denaturing gradient gel electrophoresis (DGGE) fingerprints of Pseudomonas -specific gacA genes amplified from total community DNA confirmed that RU47 established as the dominant Pseudomonas population in the rhizosphere of inoculated lettuce plants. Furthermore, the DGGE fingerprint revealed that R. solani AG1-IB inoculation severely affected the bacterial and fungal community structure in the rhizosphere of lettuce and that these effects were much less pronounced in the presence of RU47. Although the exact mechanism of antagonistic activity and the ecology of RU47 remain to be further explored, our results suggest that RU47 is a promising agent to control bottom rot of lettuce. 相似文献
96.
The anthropogenic impact on wetlands has increased during the last centuries when infrastructures such as canals or dams,
have proliferated. In this article, we have used cladoceran sub-fossils to investigate the effects of a canal on lake El Tobar
(Spain). The canal has been transferring water from a reservoir, built in another valley, into this lake since its construction
in the mid-1960s. Cladoceran remains were analyzed in two sediment profiles from each of the two sub-basins of the lake. The
sedimentary sequences showed that the mentioned human activity provoked a clear shift in the cladoceran community. A PCA was
performed with samples from both sub-basins to detect the direction and nature of the changes. Before water transference,
the phytophilous chydorid community, represented by Acroperus angustatus in one sub-basin and by both A. angustatus and Graptoleberis testudinaria in the other sub-basin, were well developed. After the construction of the canal and the inflow of additional yet different
water from the reservoir, the proportion of chydorids relative to total cladoceran diminished considerably; this was mainly
due to the invasion of Bosmina longirostris. These results indicate that the hydrological alteration caused a shift from an oligotrophic, shallower lake with a rich plant-associated
cladoceran community to a more eutrophic lake with a predominant planktonic cladoceran community; and that cladoceran remains
are a powerful tool to detect hydrological changes and eutrophication. 相似文献
97.
Martin Krajíček Jan Fott Maria R. Miracle Marc Ventura Ruben Sommaruga Philipp Kirschner Martin Černý 《Zoologica scripta》2016,45(6):671-682
Although copepods of the genus Cyclops are among the most common and dominant plankton taxa of lakes in the northern temperate zone, their taxonomy is still unclear. We analysed an extensive array of Cyclops populations from Europe by means of molecular methods and evaluated morphological characters. Altogether, 68 populations of Cyclops species were sampled, assigned to morphospecies and sequenced for the 12S rRNA gene. Selected populations of each morphospecies were additionally sequenced for three mitochondrial (16S rRNA, cytochrome b, COI) and two nuclear genes (18S rRNA, ITS1) and analysed for micromorphological traits. Our analysis revealed fifteen lineages that can be regarded as separate species. Thirteen of these match currently accepted species, while the remaining two lineages were distinct from the other described species. Thus, their taxonomic status is open to further studies. Besides taxonomy, our study gives new insights into the ecology, distribution and phylogenetic relationships of these species. Finally, a set of morphological traits was selected to facilitate identification. 相似文献
98.
F. A. Adesina W. O. Siyanbola F. A. Oketola D. A. Pelemo S. A. Momodu A. O. Adegbulugbe L. O. Ojo 《Global Ecology and Biogeography》1999,8(2):163-173
This paper attempts some preliminary evaluation of the potential of agroforestry techniques as a forestry strategy for controlling atmospheric CO2—a critical greenhouse gas. The end-use scenario that attempts to meet the wood and related needs of the nation while mitigating climate change was adopted. The net emission estimate for the Forestry Sector in 1990—the base year for the study—was 9.5 million tonnes of carbon (MtC). Based on this figure, projections into the year 2030 gave cumulative net emissions of 427.4 and 580.5 MtC at 1.3% and 2.6% deforestation rates respectively. However, mitigating with agroforestry techniques, assuming that about 76% of the estimated 39.5 million ha of farmland in the country is committed to a variety of agroforestry systems, the results show that a total of 1530 MtC can be withdrawn from the atmosphere by the year 2030. The paper concludes that there is a reasonable case for the use of agroforestry techniques in the country, both as a means of sustaining soil productivity and as a strategy for mitigating climate change. 相似文献
99.
Paolo Fusar-Poli Andrés Estradé Giovanni Stanghellini Cecilia Maria Esposito René Rosfort Milena Mancini Peter Norman Julieann Cullen Miracle Adesina Gema Benavides Jimenez Caroline da Cunha Lewin Esenam A. Drah Marc Julien Muskan Lamba Edwin M. Mutura Benny Prawira Agus Sugianto Jaleta Teressa Lawrence A. White Stefano Damiani Candida Vasconcelos Ilaria Bonoldi Pierluigi Politi Eduard Vieta Jennifer Radden Thomas Fuchs Matthew Ratcliffe Mario Maj 《World psychiatry》2023,22(3):352-365
We provide here the first bottom-up review of the lived experience of depression, co-written by experts by experience and academics. First-person accounts within and outside the medical field were screened and discussed in collaborative workshops involving numerous individuals with lived experience of depression, family members and carers, representing a global network of organizations. The material was enriched by phenomenologically informed perspectives and shared with all collaborators in a cloud-based system. The subjective world of depression was characterized by an altered experience of emotions and body (feeling overwhelmed by negative emotions, unable to experience positive emotions, stuck in a heavy aching body drained of energy, detached from the mind, the body and the world); an altered experience of the self (losing sense of purpose and existential hope, mismatch between the past and the depressed self, feeling painfully incarcerated, losing control over one's thoughts, losing the capacity to act on the world; feeling numb, empty, non-existent, dead, and dreaming of death as a possible escape route); and an altered experience of time (experiencing an alteration of vital biorhythms, an overwhelming past, a stagnation of the present, and the impossibility of the future). The experience of depression in the social and cultural context was characterized by altered interpersonal experiences (struggling with communication, feeling loneliness and estrangement, perceiving stigma and stereotypes), and varied across different cultures, ethnic or racial minorities, and genders. The subjective perception of recovery varied (feeling contrasting attitudes towards recovery, recognizing recovery as a journey, recognizing one's vulnerability and the need for professional help), as did the experience of receiving pharmacotherapy, psychotherapy, and social as well as physical health interventions. These findings can inform clinical practice, research and education. This journey in the lived experience of depression can also help us to understand the nature of our own emotions and feelings, what is to believe in something, what is to hope, and what is to be a living human being. 相似文献
100.
The future of cladoceran research 总被引:1,自引:1,他引:0