全文获取类型
| 收费全文 | 84篇 |
| 免费 | 11篇 |
| 国内免费 | 6篇 |
专业分类
| 101篇 |
出版年
| 2022年 | 1篇 |
| 2020年 | 1篇 |
| 2017年 | 1篇 |
| 2014年 | 2篇 |
| 2013年 | 3篇 |
| 2012年 | 5篇 |
| 2011年 | 4篇 |
| 2010年 | 8篇 |
| 2009年 | 4篇 |
| 2008年 | 8篇 |
| 2007年 | 6篇 |
| 2006年 | 4篇 |
| 2005年 | 6篇 |
| 2004年 | 4篇 |
| 2003年 | 3篇 |
| 2001年 | 2篇 |
| 2000年 | 1篇 |
| 1999年 | 2篇 |
| 1996年 | 1篇 |
| 1995年 | 2篇 |
| 1994年 | 1篇 |
| 1985年 | 1篇 |
| 1981年 | 1篇 |
| 1980年 | 1篇 |
| 1979年 | 1篇 |
| 1978年 | 4篇 |
| 1975年 | 1篇 |
| 1972年 | 1篇 |
| 1965年 | 2篇 |
| 1964年 | 1篇 |
| 1960年 | 1篇 |
| 1959年 | 4篇 |
| 1958年 | 1篇 |
| 1957年 | 4篇 |
| 1956年 | 4篇 |
| 1955年 | 1篇 |
| 1954年 | 1篇 |
| 1953年 | 3篇 |
排序方式： 共有101条查询结果，搜索用时 0 毫秒
1.
A. URBANEK M. PIOTROWICZ R. SZADZIEWSKI W. GI ŁKA 《Medical and veterinary entomology》2014,28(4):355-363
The distribution and morphology of antennal sensilla coeloconica in parasitic and predaceous biting midges were studied in females of Forcipomyia (feeding on the blood of frogs), Atrichopogon (feeding on haemolymph), Austroconops, Culicoides (feeding on the blood of birds and mammals) and Brachypogon (feeding on haemolymph and dissolved tissues of insects) (all: Diptera: Ceratopogonidae). A Lower Cretaceous female of Archiculicoides (Diptera: Ceratopogonidae) from Lebanese amber, which fed on the blood of unknown vertebrates, was also examined. In sensilla coeloconica ringed by microtrichia, the peg is grooved longitudinally and protrudes distinctly from the pit. We suggest that the microtrichia encircling the protruding peg form a structure resembling a picket fence in order to maintain a higher level of humidity, which facilitates the capture and transport of odour molecules through the channels in the peg wall. Sensilla coeloconica ringed by microtrichia function as very effective chemoreceptors in host‐ and prey‐seeking activity. During the evolution of Ceratopogonidae, sensilla coeloconica with a fence of microtrichia have evolved twice in groups feeding on the blood of vertebrates (i.e. in the basal lineage: Lower Cretaceous or earlier) and in the subgenus Lasiohelea of Forcipomyia (Palaeogene). Sensilla coeloconica ringed by microtrichia are described for the first time in the relict genus Austroconops. 相似文献
2.
3.
4.
5.
Abstract 1. The majority of general life‐history models treat the environment as being invariable through time, even though temporal variation in selective agents could dramatically change the outcomes, e.g. in terms of optimal size and time at maturity. For herbivorous insects, seasonal differences in food quality are reasonably well described, but seasonal dynamics of top‐down selective forces are poorly documented. 2. The present study attempted to quantify seasonal changes in predation risk of folivorous insect larvae in temperate forest habitats. In a series of field experiments, artificial larvae were exposed to predators, and the resulting bird‐inflicted damage was recorded. The trials were repeated regularly throughout the course of two summers. 3. A distinct peak of larval mortality was recorded in mid‐June (the nestling period for most insectivorous passerine birds), after which predation risk declined to a plateau of 20–30% below the peak value. 4. The recorded pattern is interpreted as a consequence of seasonal changes in the number and behaviour of insectivorous birds, and the abundance of alternative food resources for these predators. 5. A quantitative analysis based on field data indicated that considering temporal variation in mortality in life‐history models is crucial for obtaining realistic predictions concerning central life‐history traits, such as final body size in different generations. 相似文献
6.
7.
CHUNG‐JIAN LIN JIANG‐PING WANG HUNG‐DU LIN TZEN‐YUH CHIANG 《Molecular ecology resources》2007,7(5):788-790
A total of 10 polymorphic microsatellite loci from Hemibarbus labeo were isolated and characterized using an optimized protocol to construct a microsatellite‐enriched genomic library. The analysis of variability was performed in 24 specimens of mainland China. The mean number of alleles across loci was 3.10 ± 1.10 and the level of expected heterozygosity varied from 0.0417 to 0.7482. Frequencies of null alleles of the 10 loci are not significantly greater than zero. No linkage disequilibrium was detected between loci in either population. Five primer pairs cross‐amplify the microsatellites in other species, indicating transportability of the markers within the family Cyprinidae. 相似文献
8.
DONG‐SEOK KIM SOOK‐YOUNG KIM SEONG‐JOON MOON JIN‐HO CHUNG KYU‐HAN KIM KWANG‐HYUN CHO KYOUNG‐CHAN PARK 《Pigment cell & melanoma research》2001,14(2):110-115
Ceramide is a bioactive sphingolipid that mediates a variety of cell functions. However, the effects of ceramide on cell growth and the melanogenesis of melanocytes are not known. In the present study, we investigated the actions of cell‐permeable ceramide and its possible role in the signaling pathway of a spontaneously immortalized mouse melanocyte cell line, Mel‐Ab. Our results show that C2‐ceramide inhibits DNA synthesis in Mel‐Ab cells and G361 human melanoma cells in a dose‐dependent manner. Cell cycle analysis confirmed the inhibition of DNA synthesis by a reduction in the S phase. To investigate the ceramide signaling pathway, we studied whether C2‐ceramide is able to influence extracellular signal‐regulated kinase (ERK) and/or Akt/protein kinase B (PKB) activation. We demonstrated that phosphorylated Akt/PKB is decreased by C2‐ceramide, whereas phosphorylated ERK was only slightly affected. Therefore, the C2‐ceramide‐induced inactivation of Akt/PKB may be closely related to the reduced cell proliferation of Mel‐Ab cells. Furthermore, we assessed the effects of C2‐ceramide on the pigmentation of Mel‐Ab cells. The results obtained showed that the melanin content of cells was significantly reduced by C2‐ceramide at concentrations in the range of 1–10 μM, and that the pigmentation‐inhibiting effect of C2‐ceramide is much greater than that of kojic acid at 1–100 μM. In addition, we found that the activity of tyrosinase is reduced by C2‐ceramide treatment. Our results demonstrate that C2‐ceramide reduces the pigmentation of Mel‐Ab cells by inhibiting tyrosinase activity. 相似文献
9.
ZHENG Hu-Zhe LEE Hye-Ryun CUI Chun-Lan HWANG In-Wook
KWON Sun-Young CHUNG Shin-Kyo 《Plant Diversity》2008,30(1):125-128
KWON Sun-Young CHUNG Shin-Kyo 《Plant Diversity》2008,30(1):125-128
The amounts of flavonoid (myricetin , quercetin and kaempferol), antioxidant contents ( total phenolic and total flavonoid) and antioxidant activities (DPPH and FRAP) were analyzed in strawberry. Quantitative analysis of conjugated flavonoid contents were obtained after different hydrolysis concentration and reaction period . The highest yields of myricetin and quercetin were found with 1.0M HCl and a reaction period of 0.5 hr, however , for kaempferol was 1.0M HCl and a reaction period of 1hr , respectively. In the study, we also estimated the correlation coefficient of TPC, TFC, DPPH and FRAP. In addition , a positive correlation was observed ( r = 0.980, P < 0.05) between TPC and TFC, TPC and TFC are correlated to the DPPH activity (r = 0.913, P < 0.05 and r = 0.899 , P < 0.05 , respectively) , and to the FRAP activity ( r = 0.958, P < 0.05 and r = 0.936, P < 0.05, respectively), respectively. These results pointed out that strawberry generally possesses a high level of antioxidant activities, which could be linked to the levels of phenolic compounds in the fruit. 相似文献
10.
几种植物的杀虫效力测定 总被引：9，自引：0，他引：9
我国农民在几千年农业发展过程当中,因为和虫害斗争创造了许多办法,在这些经验中,曾发见许多可以杀虫的植物,远在1596年,李时珍所著的本草纲目中,已记述许多可以供杀虫用的植物,并分别说明其用途。在这些植物中,许多杀虫效力是很大的,如烟草等,而有许多植物的毒力是不大的或仅限於防治 相似文献