首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   128篇
  免费   16篇
林业   45篇
农学   11篇
  19篇
综合类   3篇
农作物   4篇
水产渔业   20篇
畜牧兽医   33篇
园艺   2篇
植物保护   7篇
  2022年   1篇
  2021年   4篇
  2020年   1篇
  2019年   4篇
  2018年   10篇
  2017年   6篇
  2016年   20篇
  2015年   7篇
  2014年   7篇
  2013年   6篇
  2012年   12篇
  2011年   8篇
  2010年   8篇
  2009年   5篇
  2008年   8篇
  2007年   4篇
  2006年   2篇
  2005年   9篇
  2004年   3篇
  2003年   2篇
  2001年   7篇
  2000年   3篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1985年   1篇
  1984年   1篇
  1968年   1篇
排序方式: 共有144条查询结果,搜索用时 46 毫秒
81.
During surveillance for bovine diarrhea of unknown causes in Japanese black cattle in Kagoshima Prefecture, Japan, we found two types of novel kobu-like viruses in fecal samples of calves. Sequence analyses revealed that they had L protein and 2A protein with H-box/NC sequence motif, which are present in kobuviruses. Phylogenetic analysis revealed that they were related to kobuviruses; however, they clustered apart from other kobuviruses. In the prevalence study of two types of novel kobu-like viruses, 16.9% and 10.4% prevalence of these viruses were observed in the feces of diarrheal calves in this area.  相似文献   
82.

The late-summer diel activity patterns and space utilization of five Japanese eels, Anguilla japonica, were investigated using an acoustic telemetry positioning system in a shallow brackish lake in western Japan. Eels were highly nocturnal and crepuscular, with 98.1% of positions detected between sunset and sunrise, and were more active during dusk and dawn compared with nighttime, and during full moons compared with other lunar periods. Most diurnal activity occurred during darker conditions, and two individuals extended their activity into the morning, suggesting that overcast skies reduced light intensity and prolonged nocturnal activity into daytime. Individual eels had different home-range patterns, but appeared to rest nearshore during the day, with space utilization expanding offshore at dusk and night, followed by returning to nearshore at dawn. Their home ranges and core activity areas were bordered by the shoreline, with eels tending to exhibit small activity spaces and strong site fidelity. This study provides valuable ecological knowledge about the individual behavior of eels inhabiting a small brackish lake at the northern limit of the natural distributional range of the species along the Sea of Japan, which can contribute to management and conservation of the species.

  相似文献   
83.
The relationship between the peripheral concentrations of estradiol-17β (E(2)) and the preovulatory characteristics of cumulus oocyte complexes (COCs) during superovulation treatment was investigated in Japanese Black cows. A superovulation regimen with FSH treatment in a descending manner was commenced on day 7 (n=3) or day 10 (n=2) of the estrous cycle (day 0=estrus). Peripheral blood was collected to measure E(2) concentrations twice a day throughout the treatment. Ovariectomies were performed at 100 h after the initial FSH treatment in five cows. Every follicle more than 8 mm in diameter was isolated from the ovaries, and cumulus-oocyte complexes (COCs) were gently aspirated. The COCs were then separated into three groups based on the characteristics of the cumulus (compact, expanded and denuded) and subgrouped based on the stage of the nucleus in the oocytes (GV, GVBD). Plasma E(2) concentrations tended to increase gradually and reached the peak level at around 84 h (E(2)-84: n=3) or 96 h (E(2)-96: n=2) after the initial FSH treatment. The ratio of COCs with expanded cumulus was significantly higher in E(2)-84 than in E(2)-96 (P<0.01). However, there was no difference in the ratio of oocytes showing GVBD between E(2)-84 and E(2)-96 (P=0.73), and the characteristics of the cumulus did not affect the stage of the nucleus in the oocytes in either groups (compact, expanded and nude; P=0.61, 0.81 and 1.00). It was possible that the time until the peak plasma E(2) concentrations after the FSH treatment could become an indicator for the maturation of follicles and oocytes in preovulatory follicles during superovulation treatment in Japanese Black cows.  相似文献   
84.
Bunching onion (Allium fistulosum L.) is one of the most important vegetables in Japan. To establish a genetic basis for molecular breeding of bunching onion, we isolated 1,796 simple sequence repeat (SSR) clones by large-scale sequencing of SSR-enriched genomic DNA libraries. Of these, 1,331 (74.1%) contained (GT) n repeats (n > 5), while 314 (17.5%) were (GA) n -containing clones. The average number of SSR repeats was 10.5 and 10.4 in the (GT) n - and (GA) n -containing clones, respectively. In a sample of five bunching onion inbred lines, an average of 3.2 alleles were detected in the 100 SSR loci investigated, with the polymorphic information content averaging 0.55. These results indicate that bunching onion SSRs are very rich sources of highly informative genetic markers.  相似文献   
85.
86.
A series of two filtration experiments were conducted to evaluate the filtration function of forest soil experimentally. The first experiment evaluated the differences between the filtration capabilities of the A0 horizon and A horizon, and the effect of overstory species on the filtration function of the A0 horizon. Undisturbed A0, A and A0+A horizons were collected for the filter mediums with cylindrical samplers. Leaves ofQuercus serrata, Quercus myrsinaeforia, Sasa senanensis Pinus densiflora, Chamaecyparis obtusa, andCryptomeria japonica were also packed in the samplers. Various suspended sediment concentration of water were sprayed at constant intensity on the surface of samples. Filtering coefficients were not affected by SS concentration in all samples, and the order of filtering coefficient was: A0 horizons>A0+A horizons>A horizons in undisturbed forest soil samples, andQuercus serrata>Sasa senanensis>Quercus myrsinaeforia>Pinus densiflora”Chamaecyparis obtusa>Cryptomeria, japonica in leaf samples. These results led to the conclusion that SS from managed forests can best be prevented by buffer zones where a thick A0 horizon is maintained. The second experiment evaluated the effect of turbid water supply rate on the filtration capacity. Undisturbed A horizons and four leaf types,Quercus serrata, Pinus densiflora, Chamaecyparis obtusa, andCryptomeria japonica were used as filter mediums. Filtering coefficients were inversely proportional to supply rate of turbid water in all samples.  相似文献   
87.
In order to analyze the structural features of small lignin fragments that are closely associated to polysaccharides, lignin carbohydrate complex (LCC) with low lignin content was extracted with water from the residual wood meal (sugi, Cryptomeria japonica) of milled wood lignin (MWL) isolation. This LCC exhibited almost the same neutral sugar composition as those extracted by other LCC solvents (dimethylformamide, dimethylsulfoxide, and others) but the lignin content was only 5.3%, which was much lower than others. Gel filtration chromatography demonstrated that lignin in this LCC was found together with carbohydrates at the higher molecular weight region, but after the treatment with carbohydrate-degrading enzymes the apparent molecular weight of both lignin and carbo-hydrates decreased significantly. Using a mild alkaline treatment, the apparent molecular weight of lignin also decreased while that of polysaccharide was not affected. These data indicated that lignin in this LCC is present as small fragments attached to high molecular weight polysaccharide at least partly by alkali-unstable linkages. Structural analysis by ozonation method revealed that the lignin in this LCC was lower in erythro/threo ratio of -O-4 structure and relatively richer in the threo type structure carrying C-aryl linkages at -position (-5 and/or -1) than other lignin fractions present in MWL, LCCs extracted by other solvents, and their extraction residues. It was suggested that the chemical structure of lignin closely associated to carbohydrates was different from that of the main part of lignin.This paper was presented in part at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, Japan, April 2002, at the 47th Lignin Symposium, Gifu, Japan, October 2002, and at the 12th International Symposium on Wood and Pulping Chemistry, Madison, USA, June 2003  相似文献   
88.
To quantify the contribution of denitrification and autotrophic and heterotrophic nitrification to N2O production in Andosols with a relatively high organic matter content, we first examined the effect of C2H2 concentrations on N2O production and on changes in mineral N contents. The optimum C2H2 concentration for inhibiting autotrophic nitrification was 10 Pa. Secondly, and Andosol taken from an arable field was incubated for 32 days at 30°C at 60, 80, and 100% water-holding capacity with or without the addition of NH 4 + or NO inf3 sup- (200 mg N kg-1), and subsamples collected every 4–8 days were further incubated for 24 h with or without C2H2 (10 Pa). At 60 and 80% water-holding capacity with NH 4 + added, 87–92% of N2O produced (200–250 g N2O–N kg-1) was derived from autotrophic nitrification. In contrast, at 100% water-holding capacity with or without added NO inf3 sup- , enormous amounts of N2O (29–90 mg N2O–N kg-1) were produced rapidly, mostly by denitrification (96–98% of total production). Thirdly, to examine N2O production by heterotrophic nitrification, the Andosol was amended with peptone or NH 4 + (both 1000 mg N kg-1)+citric acid (20 g C kg-1) and with or without dicyandiamide (200 mg N kg-1). Treatment with citric acid alone or with citric acid+dicyandiamide suppressed N2O production. In contrast, peptone increased N2O production (5.66 mg N2O–N kg-1) mainly by denitrification (80% of total production). However, dicyandiamide reduced N2O production to 1.1 mg N2O–N kg-1. These results indicate that autotrophic nitrification was the main process for N2O production except at 100% water-holding capacity where denitrification became dominant and that heterotrophic nitrification had a lesser importance in the soils examine.Dedicated to Professor J. C. G. Ottow on the occasion of his 60th birthday  相似文献   
89.
90.
ABSTRACT: The surface-migratory myctophid fish, Myctophum asperum , of the western North Pacific was found to have daily growth increments of its sagittal otolith, which also exhibited lunar periodicity in the deposition of increments. Daily deposition of the otolith increments was verified because the width of the marginal increment increased during the night and early morning between 20.00 h and 08.00 h and its growth stopped during the day. An autocorrelation analysis of the increment widths, which were measured consecutively in 11 specimens covering 33 synodic months, also showed a lunar periodicity in increment deposition. The mean increment widths during five days around the time of a full moon were significantly narrower than those around a new moon in 18 of the 33 full moon cases ( P < 0.01: Student's t -test) and, on average, tended to be narrow in 29 cases. The cause of this tendency is thought to be slower growth caused by staying in deeper and colder habitat due to the suppression of diel vertical migration and/or lower food availability resulting from the possible dispersion of zooplankton during the full moon period.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号