全文获取类型
收费全文 | 399篇 |
免费 | 22篇 |
专业分类
421篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 7篇 |
2015年 | 20篇 |
2014年 | 15篇 |
2013年 | 15篇 |
2012年 | 45篇 |
2011年 | 29篇 |
2010年 | 16篇 |
2009年 | 15篇 |
2008年 | 20篇 |
2007年 | 33篇 |
2006年 | 28篇 |
2005年 | 16篇 |
2004年 | 16篇 |
2003年 | 31篇 |
2002年 | 14篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1978年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有421条查询结果,搜索用时 15 毫秒
111.
Any biocontrol agent used against stored grain insects will have to interact with insecticides used as grain protectants due
to their heavy use especially in tropical areas. Therefore, the interaction between the pyrethroid insecticides bifenthrin
and deltamethrin and Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae), an egg parasite of the stored cereal pest Rhyzopertha dominica(F.) (Coleoptera: Bostrichidae), was assessed in a range of mite densities and insecticide doses for each compound. Despite
the mite species presence on all insecticide doses, the lowest instantaneous rate of increase of A.lacunatus was recorded with the highest doses of insecticides. The presence of the biological control agent at all doses of both insecticides
suggests its tolerance to these compounds. A. lacunatusshowed higher parasitism rate with bifenthrin than with deltamethrin indicating a higher selectivity of the first compound
to the biocontrol agent.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
112.
The N-terminal propeptides of cysteine proteinases play regulatory roles in the folding and stability of their catalytic domains, as well as being potent and highly specific inhibitors of their parental mature enzymes. Cysteine proteinases play a major role in the biology of the parasitic trematode Fasciola hepatica; in particular, this organism secretes significant amounts of cathepsin L enzymes. The isolated propeptide of F. hepatica cathepsin L1 functioned as a chaperone for the mature enzyme in renaturation experiments. A double point mutation (N701/F721) within the GxNxFxD motif of the propeptide affected its conformation and markedly decreased its affinity for the mature enzyme. When this mutation was introduced into preprocathepsin L1 expressed in yeast, the secretion of active enzyme dropped dramatically. However, significant enzyme activity was recovered from the culture supernatants after denaturation and renaturation in the presence of native propeptide. Thus, the variant prosegment gave rise to an enzyme with altered conformation, which could be refolded to the active form with the assistance of the native propeptide. 相似文献
113.
Luciano F. Huergo Marcelo C. Assumpo Emanuel M. Souza M. Berenice R. Steffens M. Geoffrey Yates Leda S. Chubatsu Fbio O. Pedrosa 《Applied microbiology》2004,70(10):6320-6323
The Azospirillum brasilense mutant strains FP8 and FP9, after treatment with nitrosoguanidine, showed a null Nif phenotype and were unable to use nitrate as their sole nitrogen source. Sequencing of the ntrC genes revealed single nucleotide mutations in the NtrC nucleotide-binding site. The phenotypes of these strains are discussed in relation to their genotypes. 相似文献
114.
115.
Ramnarayan S. Randad Lucyna Lubkowska Michael A. Eissenstat Sergei V. Gulnik Betty Yu T. Narayana Bhat David J. Clanton Tyra House Sherman F. Stinson John W. Erickson 《Bioorganic & medicinal chemistry letters》1998,8(24):1679-3542
A series of novel unsymmetrical anthranilamide-containing HIV protease inhibitors was designed. The structure-activity studies revealed a series of potent P2–P3′ inhibitors that incorporate an anthranilamide group at the P2′ position. A reduction in molecular weight and lipophilicity is achieved by a judicious choice of P2 ligands (i.e., aromatic, heteroaromatic, carbamate, and peptidic). A systematic investigation led to the 5-thiazolyl carbamate analog 8m, which exhibited a favorable Cmax/EC50 ratio (>30), plasma half-life (>8 h), and potent in vitro antiviral activity (EC50 = 0.2 uM). 相似文献
116.
Michal Krawczyk Izabela Burzynska-Pedziwiatr Lucyna Alicja Wozniak Malgorzata Bukowiecka-Matusiak 《Current issues in molecular biology》2022,44(2):699
In vitro and animal model studies are of great interest for selecting new phytochemicals, including polyphenols with antioxidative properties, as candidates for antidiabetic drugs. This review provides evidence from a critical literature data analysis on the effects of plant extract supplementation in diabetes mellitus management. We considered and meta-analyzed the efficacy of oral supplementation of plant extracts in animal model studies and examined physiological and oxidative stress parameters. Finally, 23 articles were included in the meta-analysis, revealing three plants with experimentally confirmed in vivo and in vitro antidiabetic properties: Gymnema montanum, Momordica charantia and Moringa oleifera. The following parameter changes resulted from an investigation of the supplementation: reduced oxidative stress, decreased insulin resistance, increased insulin release, reduced adiposity, and a modulatory effect on glycolysis and gluconeogenesis, as well as attenuation of diabetes-associated weight loss, reduced fasting blood glucose and lowered oxidative status. A comparison of Gymnema montanum versus Glybenclamide revealed the superiority of extracts over drug administration in some aspects. Although the analyzed extracts are promising candidates for antidiabetic treatment, there is much inconsistent data in the literature. Therefore, ultimate references for using these compounds in the prevention of diabetes are currently not applicable. 相似文献
117.
de Menezes JE Machado FE Lemos TL Silveira ER Braz Filho R Pessoa OD 《Zeitschrift für Naturforschung. C, Journal of biosciences》2004,59(1-2):19-22
Two new secondary metabolites, the phenylpropanoid 3-(2',4',5'-trimethoxyphenyl)propanoic acid (1) and the sesquiterpene (+)-1beta,4beta,6alpha-trihydroxyeudesmane (2) were isolated from the heartwood of Cordia trichotoma Vell., along with the known sesquiterpenes (-)-1beta,4beta,7alpha-trihydroxyeudesmane (3) and (+)-1beta,4beta,11-trihydroxyoppositane (4). Their structures were elucidated by means of spectroscopic data interpretation, mainly 1D and 2D NMR and mass spectrometry. 相似文献
118.
Genetic immunization of ducks for production of antibodies specific to Helicobacter pylori UreB in egg yolks 总被引:4,自引:0,他引:4
Kazimierczuk K Cova L Ndeboko B Szczyrk U Targosz A Brzozowski T Sirko A 《Acta biochimica Polonica》2005,52(1):261-266
Following genetic immunization of laying ducks with a plasmid expressing Helicobacter pylori UreB (large subunit of urease), IgY against UreB were obtained from egg yolks. These polyclonal and monospecific IgY antibodies are of higher-titer and specifically recognize recombinant H. pylori urease purified from Escherichia coli. To our knowledge this is the first report describing generation of IgY antibodies directed against antigens of H. pylori by DNA-based immunization. 相似文献
119.
120.