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   548篇
  免费   18篇
  国内免费   3篇
林业   58篇
农学   27篇
基础科学   3篇
  51篇
综合类   28篇
农作物   15篇
水产渔业   59篇
畜牧兽医   284篇
园艺   4篇
植物保护   40篇
  2023年   3篇
  2022年   17篇
  2021年   22篇
  2020年   10篇
  2019年   1篇
  2018年   17篇
  2017年   9篇
  2016年   13篇
  2015年   14篇
  2014年   32篇
  2013年   27篇
  2012年   27篇
  2011年   39篇
  2010年   13篇
  2009年   16篇
  2008年   35篇
  2007年   38篇
  2006年   30篇
  2005年   30篇
  2004年   27篇
  2003年   37篇
  2002年   14篇
  2001年   17篇
  2000年   9篇
  1999年   8篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
  1995年   3篇
  1994年   5篇
  1993年   2篇
  1992年   4篇
  1991年   6篇
  1990年   2篇
  1989年   4篇
  1988年   6篇
  1987年   4篇
  1986年   5篇
  1985年   5篇
  1984年   2篇
  1983年   4篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1966年   1篇
排序方式: 共有569条查询结果,搜索用时 15 毫秒
1.
Canine cationic trypsin was purified by salting-out, gel filtration and affinity chromatography. Purity was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight was ca. 28 kDa by SDS-PAGE.

Thirty hybridomas were obtained which produced mAb to canine cationic trypsin by the cell fusion technique. Twenty-two of these recognized cationic trypsin only, while eight hybridomas recognized both cationic and anionic trypsin. Several of the anti-canine cationic trypsin mAb were purified by salting-out and DEAE ion-change chromatography using ascites fluid of immunized BALB/c mice. The mAb proved to have very high specificity to canine cationic trypsin as shown by immunoblotting and it may be possible to use them to develop clinical assays.  相似文献   

2.
Inflammatory airway disease (IAD) is a common cause of poor performance, interruption of training and premature retirement in racehorses. It is also reported that up to 80% of horses are affected at some point in the first years of training in UK and Australia. However, no studies with regard to the information on occurrence of IAD in Japanese Thoroughbred racehorses have been reported. To investigate the occurrence and the characteristics of IAD, epidemic research including endoscopic examination of the airway tract and trachea wash was conducted for Thoroughbred racehorses presenting coughs or poor performance which airway tract disease was suspected stalled in training facility managed by Japan Racing Association. Fifty-six out of 76 Thoroughbred racehorses (73.7%) presenting coughing or poor performance were diagnosed as IAD. Mean incidence rate of IAD was 0.3% and it has been confirmed that constant number of IAD exists in Japan. Up to 35.7% of IAD horses showed upper airway abnormalities in some extent. There was a trend for IAD horses to use wood shavings for bedding and fed hay from the ground compared with the control group. Therefore, improvement of stabling environment may aid in preventing IAD. This study demonstrated that Japanese Thoroughbred racehorses are affected by IAD likewise other countries as well as demonstrated the characteristics of IAD which may contribute to the clarification of the pathogenesis of IAD.  相似文献   
3.
Photoperiod sensitivity is an important trait related to crop adaptation and ecological breeding in common buckwheat (Fagopyrum esculentum Moench). Although photoperiod sensitivity in this species is thought to be controlled by quantitative trait loci (QTLs), no genes or regions related to photoperiod sensitivity had been identified until now. Here, we identified QTLs controlling photoperiod sensitivity by QTL analysis in a segregating F4 population (n = 100) derived from a cross of two autogamous lines, 02AL113(Kyukei SC2)LH.self and C0408-0 RP. The F4 progenies were genotyped with three markers for photoperiod-sensitivity candidate genes, which were identified based on homology to photoperiod-sensitivity genes in Arabidopsis and 76 expressed sequence tag markers. Among the three photoperiod-sensitivity candidate genes (FeCCA1, FeELF3 and FeCOL3) identified in common buckwheat, FeELF3 was associated with photoperiod sensitivity. Two EST regions, Fest_L0606_4 and Fest_L0337_6, were associated with photoperiod sensitivity and explained 20.0% and 14.2% of the phenotypic variation, respectively. For both EST regions, the allele from 02AL113(Kyukei SC2)LH.self led to early flowering. An epistatic interaction was also confirmed between Fest_L0606_4 and Fest_L0337_6. These results demonstrate that photoperiod sensitivity in common buckwheat is controlled by a pathway consisting of photoperiod-sensitivity candidate genes as well as multiple gene action.  相似文献   
4.
The consumption of products made from Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) has increased in recent years in Japan. Increased consumer demand has led to recognition of the need for early varieties of this crop with high and stable yields. In order to accomplish this, more information is needed on the genetic mechanisms affecting earliness and yield. We conducted genetic analysis of 3 agronomic traits (days to flowering, plant height and total seed weight per plant) to segregate F2 and F3 populations derived from a cross between Tartary buckwheat cultivars ‘Hokuriku No. 4’ and ‘Ishisoba’. Broad-sense heritability estimates for days to flowering, plant height and total seed weight were 0.70, 0.62 and 0.75, respectively, in F3 population. Narrow-sense heritability for total seed weight (0.51) was highest, followed by heritability for days to flowering (0.37), with heritability for plant height (0.26) lowest. Later flowering was associated with increased plant height and higher yields. From the F4 generation, we identified twelve candidate plants with earlier maturity and reduced plant height compared to ‘Hokuriku No. 4’, but almost the same total seed weight. These results suggest that hybridization breeding using the single seed descent (SSD) method is an effective approach for improving agronomic characteristics of Tartary buckwheat.  相似文献   
5.
ABSTRACT

Understanding how maturity genes affect soybean yield formation will provide important information for crop management decisions. This study aimed to reveal how maturity genes E2 and E3 in the soybean cultivar ‘Enrei’ affect yields and yield formation in warm regions of Japan. ‘Enrei’ (e2e3) and three near-isogenic lines of ‘Enrei’ (e2E3, E2e3, and E2E3) were cultivated in 2016 and 2017 in Fukuyama, Japan (34°30′N, 133°23′E). Two sowing dates were set in each year (June sowing and July sowing). E2 extended the period from emergence to R1 and also the period from R1 to R7, whereas E3 extended only the period from emergence to R1. Interaction between E2 and E3 did not affect duration of the period from emergence to R1, but did affect the period from R1 to R7. Although seed yield did not differ between genotypes in the June sowings, the effects of E2 and E3 on seed yield in July sowing were both significant and interaction between E2 and E3 also observed. The total number of nodes increased in E3 genotypes in both sowing dates, especially in E2E3. Pod-set ratio was lower in E2 and E3 genotypes than in e2 and e3 genotypes in the June sowings, but did not differ between genotypes in the July sowings. The high yield of E2E3 genotypes in the July sowings was attributed to increased number of nodes and flower production while maintaining pod-set ratio. Appropriate choice of sowing date is suggested to be essential when using E3 genotypes.Abbreviations: HI: harvest index; NIL: near-isogenic line; RUE: radiation use efficiency; TDM: total above-ground dry matter; TRI: total solar radiation intercepted  相似文献   
6.
In this study, we developed a computer program for automatic prediction of watering time point by considering the environmental factors such as solar radiation, air temperature and relative humidity based on the multiple linear regression equation of leaf area and Penman Method. The experiments were carried out for a year in two watering experimental plots, one of which was controlled by pF value, and the other by the computer program. After comparing the results of the two plots, the following findings were obtained. In the computer program plot, the observed and predicted values of both leaf area and evapotranspiration indicated significant correlation at the 1% level, which suggested that the computer program had high prediction accuracy. In addition, no significant difference was observed between the two experimental plots with respects to the plant height, plant diameter, leaf area, leaf number, fresh weight, and dry weight, which demonstrated that the plants in the computer program plot had normal growth. On the other hand, although the number of flower buds and flowering shoots showed higher values at the end of certain cultivations in the computer program plot than those in pF value plot, we proposed that it was due to the effect of cumulative daily solar radiation in the greenhouse, rather than the watering. Thus, we have reached the conclusion that the computer program for automatic prediction of watering time point developed by this study has high applicability in miniature pot rose production.  相似文献   
7.
ABSTRACT

From a transaction cost perspective, this paper shows how the tradition of consuming marine fish by the majority of Hong Kong's Chinese citizens has shaped the means and modes of marketing seafood in Hong Kong. It is argued that consumer preferences stimulate aquaculture as a non-open access measure to bypass state fish marketing regulations. This has resulted in two outcomes. First, the transaction cost savings on metering output quantity and quality under private property have led not only to the collapse of the state monopoly on marine fish marketing, but also to the emergence of the (then new but) currently popular kind of Chinese seafood restaurant in Hong Kong. Second, consumer preferences for variety have shaped the form of coordination between the producer and the consumer. The advantage of market coordination has led to the emergence of a system of wholesaling and retailing rather than vertical integration. Issues concerning the emergence of Hong Kong as a regional live marine fish production and trading centre are discussed in terms of the contribution of local mariculture to sustainable development.  相似文献   
8.
<正>Dear Editor,Rice is an important staple food crop in Asia, but the anaerobic soil conditions in rice fields cause emission of the potent greenhouse gas, methane(CH4)(Le Mer and Roger,2001), and promote the accumulation of arsenic(As) in the grain(Le Mer and Roger, 2001; Khanam et al., 2020).To facilitate sustainable agriculture, using wastewater as an organic fertilizer is essential for reducing wastewater treatment-associated energy consumption and the recycling of wastewate...  相似文献   
9.
ABSTRACT:   Color vision, spectral sensitivity, accommodation, and visual acuity were examined in juvenile masu salmon Oncorhynchus masou masou to obtain fundamental information about the visual system. Two types of S-potentials were recorded from 415 horizontal cells in isolated retinas from 34 cultured freshwater masu salmon (114–219 mm standard length, SL). Although horizontal cells recording S-potentials were not identified, the horizontal cells were confirmed because their responses were maintained while the stimulus remained. The variety of chromaticity (C)-type S-potentials indicated well-developed color vision. The analysis of the luminosity (L)-type S-potentials indicated that the peak spectral sensitivity was at 522 nm. S-potentials were also recorded in response to ultraviolet light. The direction and extent of lens movement induced by electrical stimulation was measured in 12 cultured masu salmon (99.0–142.5 mm SL). The results indicated that the visual axis was upward and forward, and that the range of accommodation was from 0.79 × SL in front of the eye to infinity. In histological analysis of the retinas of five wild smolts (100–118 mm SL), the maximum cone densities (276–345 cones/0.01 mm2) were detected in the ventral to temporal regions. The visual acuities assessed by histological methods were 0.069–0.075.  相似文献   
10.
This study examines the optimal method to extract logging residues from small, fragmented and scattered forests separately from the mechanized operational systems used on aggregated forestry operation sites. First, small-scale logging systems operated by a private logging contractor and an individual forest owner were investigated. Regression equations for estimating felling and processing cycle times were established as a function of stem and log volumes, respectively. Equations to estimate the forwarding and transporting cycle times were established as a function of the forwarding and transporting distances using the forwarding and transporting velocities, respectively. Then, equations to estimate productivities and costs were established with the cycle times, volumes and hourly operational expenses consisting of labour and machinery expenses. Finally, costs of the small-scale systems—mini-forwarder and 4 t truck operated by a private logging contractor, and manual logging and light truck operated by an individual forest owner—were estimated and compared with the mechanized operation system operated by the Forest Owners’ Association. The mechanized operation system was found to have the highest cost and could not compete for small forestry operational sites and small stem volumes. The small-scale systems could be effective for harvesting small areas. This was especially true when conducting extracting operations without machines, as done by the individual forest owner, and transporting operations by a private logging contractor, in which the hourly income of the individual forest owner was higher than the hourly labour expenses.  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