全文获取类型
收费全文 | 362篇 |
免费 | 25篇 |
国内免费 | 71篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 10篇 |
2014年 | 27篇 |
2013年 | 29篇 |
2012年 | 9篇 |
2011年 | 16篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 25篇 |
2007年 | 25篇 |
2006年 | 15篇 |
2005年 | 8篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有458条查询结果,搜索用时 643 毫秒
81.
Individuals ofSitobion avenae (F.) (Homoptera: Aphididae) were marked with the stable isotope 15N through feeding on cereal seedlings which were immersed in a15N-enriched nutrient solution. Increased 15N-contents were obtained in all aphids with no detrimental effect on survival and fertility. When 15N-marked aphids were transferred to non 15N-enriched seedlings, after a short initial decreasing phase, 15N-contents remained nearly constant in time. A content of 10% 15N in the nutrient solution of the seedlings was sufficient for marking the aphids. 相似文献
82.
M. P. Walton H. D. Loxdale L. Allen Williams 《Biological journal of the Linnean Society. Linnean Society of London》1990,40(4):333-346
Polyacrylamide gel electrophoresis was used to construct electrophoretic 'keys' for identifying larval, pupal and adult hymenopterous parasitoids of Sitobion avenae (F.). In general, for each parasitoid and enzyme system tested, all life stages gave similar banding patterns. Although five enzyme systems were tested, esterase was found to be the most useful single system. Using laboratory-reared parasitoids and staining for esterase activity, all species examined, except Aphidius rhopalosiphi and A. ervi could be readily distinguished with the aid of the appropriate key. 相似文献
83.
The effects of photoperiod and temperature on the production of sexual forms by two clones of Sitobion avenae, the grain aphid, were examined. One clone did not produce sexual forms, whereas the other did under conditions of short light (<14 h) and low temperature (15°C). Temperature and photoperiod interacted to some extent both in the production of oviparae and of males. Even when the sexual forms were produced there was always a proportion of virginoparae.
Production de sexués par Sitobion avenae, puceron monoécique
Résumé Un clone de Sitobion avenae a produit sans difficulté jusqu'à 7 générations de sexués en réaction à des photopériodes courtes (<14 h) et à de faibles températures (15°C) tandis qu'un autre clone n'en produit aucune.La proportion de sexués différait suivant les parents. La production de mâles avait une nette tendance à apparaître lors des reproduction les plus tardives. Dans les générations tardives avec jours courts, les vivipares (virginopares et gynopares) avaient eu tendance à être produits à la fin de la période de reproduction.Les gynopares (c'est à dire les parents d'ovipares) de S. avenae étaient surtout aptères, mais comprenaient beaucoup plus d'ailés que les virginopares obtenus dans les mêmes conditions. Un vivipare était induit comme gynopare (ou ses embryons étaient déterminés comme ovipares) avant la naissance, mais cette détermination pouvait apparemment encore être inversée en soumettant l'insecte à de longues photopériodes et à de hautes températures jusqu'à deux jours après la naissance.Aucun S. avenae ovipare n'a été produit jusqu'à la troisième génération. Aucun ovipare n'a été produit avec des photopériodes supérieures à 13 H 30 à 10°C, 13 H à 15°C et 8 H à 20°C. La proportion d'individus produisant des ovipares à 15°C a été plus faible qu'à 10°C pour toutes les photopériodes, et à cette dernière température beaucoup plus de vivipares étaient gynopares que virginopares.Les basses températures ont été vraisemblablement le facteur dominant de stimulation de la production de mâles de S. avenae, mais cependant il semble qu'un plus grand nombre de mâles a été produit aux températures et photopériodes intermédiaires qu'aux extrêmes.La capture de mâles ailés de S. avenae dans des pièges à succion a été généralement limitée à Octobre-soit à peu prés le moment prévu par les expériences de laboratoire. Des mâles de S. avenae sont aussi capturés fréquemment et été, ce qui peut être lié à des hivers précédents doux.相似文献
84.
Lucas J. Bailey Kimberly M. Sheehy Pawel K. Dominik Wenguang G. Liang Huan Rui Michael Clark Mateusz Jaskolowski Yejoon Kim Dawid Deneka Wei-Jen Tang Anthony A. Kossiakoff 《Journal of molecular biology》2018,430(3):337-347
Antibody Fab fragments have been exploited with significant success to facilitate the structure determination of challenging macromolecules as crystallization chaperones and as molecular fiducial marks for single particle cryo-electron microscopy approaches. However, the inherent flexibility of the “elbow” regions, which link the constant and variable domains of the Fab, can introduce disorder and thus diminish their effectiveness. We have developed a phage display engineering strategy to generate synthetic Fab variants that significantly reduces elbow flexibility, while maintaining their high affinity and stability. This strategy was validated using previously recalcitrant Fab–antigen complexes where introduction of an engineered elbow region enhanced crystallization and diffraction resolution. Furthermore, incorporation of the mutations appears to be generally portable to other synthetic antibodies and may serve as a universal strategy to enhance the success rates of Fabs as structure determination chaperones. 相似文献
85.
Joceline Barrios‐Sanmartín Emilie Bosquée María E. Rubio‐Meléndez Claudio C. Ramírez Frédéric Francis 《Physiological Entomology》2018,43(1):69-76
Benzoxazinoids are key defence chemicals in cereals that are known to affect several aspects of aphid biology. However, little is known about how they affect aphid physiology. In the present study, we report changes in the whole‐body proteomic profiles of a 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one (DIMBOA)‐susceptible genotype of the grain aphid Sitobion avenae (F.) after being exposed to wheat cultivars containing contrasting levels of DIMBOA. The proteome is analyzed after 14 days (short term) and 28 days (long term) of rearing on these cultivars. Seventy‐two proteins are differentially regulated among the treatments and 49 are identified. Exposure to high‐DIMBOA plants results in a higher number of proteins regulated long term. DIMBOA exposure in S. avenae initially generates greater cellular activities, mostly involving cytoskeleton function and possibly related to detoxification. This function appears to be unimportant at long term and is eventually replaced by effects on metabolism function and homeostasis. Taken together, the results of the present study show that the responses of aphids to the secondary plant compounds, such as DIMBOA, exhibit a temporal dynamic in the proteome, possibly helping aphids to overcome the effect of these toxic compounds. 相似文献
86.
Winged individuals of Rhopalosiphum padi and Sitobion avenae transmitted the PAV-like and MAV-like isolates of barley yellow dwarf virus respectively. Success of transmission after inoculation access periods of 2, 6, 12, 24, 48 and 72 h were examined and survival, reproduction and movement of the aphid vectors were recorded at these times. The experiment was done at four different temperatures: 6o C, 12o C, 18o C and 23o C. For both isolates the inoculation efficacy did not increase after a 24 h inoculation access period and there was no difference in inoculation efficiency at the three highest temperatures, that at 6o C being significantly lower than at 12o C to 23o C. The results suggest that autumn temperature is a critical factor for BYDV epidemiology in Britain with a small increase in autumn temperature leading to greatly increased infection rates. 相似文献
87.
Effects of honeydew and insecticide residues on the distribution of foraging aphid parasitoids under glasshouse and field conditions 总被引:1,自引:0,他引:1
The opposing effects of attraction to host-derived kairomones and repellency from the pyrethroid insecticide deltamethrin were investigated with aphid parasitoids from the genus Aphidius (Hymenoptera: Aphidiinae). The spatial distribution of female parasitoids was recorded in a series of experiments conducted in a small glasshouse containing wheat plants either infested with cereal aphids, Sitobion avenae (F.) (Homoptera: Aphididae), uninfested or treated with the recommended field concentration of deltamethrin. The number of parasitoids per plant were counted at 0.5 h, 1 h and then at one hourly intervals up to 8 h after release. Parasitoids showed a strong aggregation response to aphid-infested plants compared to adjacent uninfested plants. With the introduction of insecticidetreated plants around the aphid-infested plants, parasitoids showed a greater tendency to disperse away, resulting in fewer parasitoids on plants and significantly lower rates of aphid parasitism. The degree of aphid fall-off from plants was a good indicator of parasitoid foraging activity. In field studies, using sticky traps to measure the activity of parasitoids in plots sprayed with water, deltamethrin and/or an artificial honeydew solution, repellent properties were evident for up to 2 days after application. The attraction/arrestment stimuli associated with the honeydew solution were sufficient for parasitoids to continue searching insecticide-treated areas. The implications of these findings for parasitoids searching crops contaminated with aphid-derived kairomones and insecticides are discussed. 相似文献
88.
Effect of methoxyphenols on grain aphid feeding behaviour 总被引:2,自引:0,他引:2
B. Leszczynski W. F. Tjallingii A. F. G. Dixon R. Swiderski 《Entomologia Experimentalis et Applicata》1995,76(2):157-162
Methoxyphenols might be important in the resistance of cereals to aphids. Electrical penetration graph (EPG) recordings were
used to determine the effect of caffeic, ferulic and sinapic acids, and scopoletin on the feeding behaviour of the grain aphidSitobion avenae (F.). Aphids on wheat seedlings treated systemically with these phenols showed reduced ingestion of phloem sap and salivation
into sieve elements in most cases. The earlier pathway phases of probing were prolonged. Moreover increase in number of probes
as well as reduction of total time of probing was observed. In addition, no O-demethylase activity was found in homogenates
of aphids fed on moderately-resistant (phenolic rich) or susceptible (phenolic poor) wheat varieties. The significance of
these results for understanding the resistance of cereals to aphids is discussed. 相似文献
89.
J A. MANN G M. TATCHELL M J. DUPUCH R. HARRINGTON S J. CLARK H A. McCARTNEY 《The Annals of applied biology》1995,126(3):417-427
The effect of wind and rain on initiation of dispersal and subsequent distances moved by apterous Sitobion avenae was quantified in five laboratory experiments. Wind duration and type (steady and gusting), rain duration and intensity, and a combination of wind and rain were investigated. With increased duration of wind there was an increase in the average distance aphids moved. There was less movement when aphids were exposed to gentle gusting, than to steady wind or strong gusting. With increased duration of rain there was an increase in the proportion of aphids lost from plants. Under heavy rain, the proportion of aphids off the release plant, the distance moved by them and the proportion of aphids lost, was greater than for drizzle or light rain. When wind and rain were compared, rain had the greater impact on aphid dispersal. It was concluded that leaf disturbances caused by strong gusts of wind or large rain droplets are of considerable importance in the initiation of aphid dispersal, but that wetness alone is not. 相似文献
90.
构建了具有λPRPL启动子高效表达人鼠嵌合Fab片段的温度诱导表达型载体pHZ01,并在大肠杆功中表达了三种嵌合Fab片段:抗前列腺特异抗原(PSA)的嵌合Fab,抗溶菌酶(HEL)的嵌合Fab和抗破伤风类毒素(TT)的嵌合Fab,三种表达的可溶性嵌合Fab都具有特异结合抗原的能力,嵌合Fab的CH1和CK区均为人源的,较之鼠源Fab具有更好的应用前景。 相似文献