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111.
L. JONES 《Grass and Forage Science》1990,45(1):83-90
The drying rates of grasses and lucerne, following treatment with 1% formic acid, were compared with those of untreated crops. Material was fully exposed to a flow of air in a ventilated laboratory oven set at 23 °C. Treatment with formic acid initially enhanced the rate of drying of grass, but this was followed by retardation. This reduction in the rate of drying was caused by the rapid desiccation of laminae, which reduced their effectiveness in providing a pathway for water loss from the stem. The rate of water loss directly from the stem surface was not increased by formic acid treatment, probably because the enveloping leaf sheaths acted as a protective layer. In contrast, formic acid increased drying rate in lucerne. whose stems have no such protective layer. The results suggest that chemical desiccants. which have a contact action are unlikely to have any application in making hay from grass. 相似文献
112.
The use of sward height as a criterion for determining the time and extent of stocking-rate changes on continuously grazed swards was investigated over a 2-year period (1985–86) in a sheep production experiment. Swards of three contrasting perennial ryegrass ( Lolium perenne L.) varieties were established with and without Aberystwyth S184 small-leaved white clover ( Trifolium repens L.) at an upland site (310–363 m) in mid-Wales. From spring (late April) until weaning (mid-July) the pastures were continuously stocked with Beulah Speckled Face ewes and Suffolk cross lambs. During this period sward heights of 4 ± 0.5 cm were obtained and maintained by regular adjustment of animal number on individual paddocks. Grass-only swards received 160 and 200 kg N ha−1 and the grass clover swards were given 80 and 75 kg N ha−1 in 1985 and 1986 respectively.
Differences were observed between the treatments in sward height profiles over the season necessitating contrasting adjustments to stocking rates. Mean stocking rate necessary on early flowering Aurora (22 6 ewes ha−1 ) was respectively 27% and 17% higher than on late-flowering Aberystwyth S23 and Meltra (tetraploid) ryegrasses; mean stocking rate on grass-only swards was 19% higher than on the grass-clover pastures.
It is concluded that sward height is a useful criterion on which to make adjustments to stocking rates to compare the potential performance of contrasting swards, under continuous grazing. The infrequent adjustments required to maintain a constant sward height, especially on the late flowering diploid perennial ryegrass variety on which many upland pastures are based, suggest that the criterion of sward height could be successfully employed on farms as an aid to efficient grazing management. 相似文献
Differences were observed between the treatments in sward height profiles over the season necessitating contrasting adjustments to stocking rates. Mean stocking rate necessary on early flowering Aurora (22 6 ewes ha
It is concluded that sward height is a useful criterion on which to make adjustments to stocking rates to compare the potential performance of contrasting swards, under continuous grazing. The infrequent adjustments required to maintain a constant sward height, especially on the late flowering diploid perennial ryegrass variety on which many upland pastures are based, suggest that the criterion of sward height could be successfully employed on farms as an aid to efficient grazing management. 相似文献
113.
We report a case of a layer hen (Gallus gallus forma domestica) with deviation in the morphology of the caecum, and unique opportunity to investigate the digestive performance of the animal compared with normal hens. In a study investigating digestive and reproductive performance, an atypical caecal arrangement was found in a hen that was unremarkable in regards to body mass, digestive performance and egg productivity in comparison to other hens fed a similar diet. Examination of the gastrointestinal tract revealed a singular tubular outgrowth from the ileo‐caecal junction, rather than the typical paired outgrowths. The single caecal duct bifurcated into two separate blind‐ended sacs. Similar caecal deviations have been described in adult and juveniles, but no indications of animal performance were reported in these cases. We conclude that if the presence of an abnormal caecal arrangement reduces digestive abilities they were not obvious, and some compensatory mechanism/s may exist. Alternatively, the abnormal caecal arrangement of our hen might function adequately, such that no compensation in feed intakes or reduced egg productivity was required or observed. 相似文献
114.
T. THANUTHONG D.S. FRANCIS S.P.S.D. SENADHEERA P.L. JONES G.M. TURCHINI 《Aquaculture Nutrition》2012,18(4):441-456
This study aimed to test the hypothesis that the efficiency of a finishing period can be improved by reducing the initial fat content of fish fillets, by means of a period of food deprivation. Two groups of rainbow trout (Oncorhynchus mykiss) were fed for an 18‐week grow‐out period on a vegetable oil‐based diet (VO) or a fish oil‐based diet (FO). VO fed fish were then split into two sub groups: one (VO/FO) was shifted to the FO diet for 8 weeks, whilst the other (UF/FO) was deprived of food (unfed) for 2 weeks and then fed the FO diet for the remaining 6 weeks. The control treatment (FO/FO) was represented by fish continuously fed FO. The subsequent reduction of total fat in the UF/FO treatment was then responsible for a much faster recovery towards a FO‐like fatty acid profile, validating the proposed hypothesis. However, the modification of the fatty acid composition of fish fillets during the feed withholding period, coupled with the postponement of the finishing diet, resulted in only minor beneficial effects of this strategy, and the loss of potential weight gain. However, the n‐3 LC‐PUFA content in UF/VO fish fillets was significantly higher than fish subjected to the VO/FO treatment. 相似文献
115.
Farmers’ precision pesticide technology adoption and its influencing factors: Evidence from apple production areas in China
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YUE Meng LI Wen-jing JIN Shan CHEN Jing CHANG Qian Glyn JONES CAO Yi-ying YANG Gui-jun LI Zhen-hong Lynn J. FREWER 《农业科学学报》2023,22(1):292-305
The research aimed to understand farmers’ willingness to adopt (WTA) and willingness to pay (WTP) for precision pesticide technologies and analyzed the determinants of farmers’ decision-making. We used a two-stage approach to consider farmers’ WTA and WTP for precision pesticide technologies. A survey of 545 apple farmers was administered in Bohai Bay and the Loess Plateau in China. The data were analyzed using the double-hurdle model. The results indicated that 78.72% of respondents were willing to apply precision pesticide technologies provided by service organizations such as cooperatives and dedicated enterprises, and 69.72% were willing to buy the equipment for using precision pesticide technologies. The results of the determinant analysis indicated that farmers’ perceived perceptions, farm scale, cooperative membership, access to digital information, and availability of financial services had significant and positive impacts on farmers’ WTA precision pesticide technologies. Cooperative membership, technical training, and adherence to environmental regulations increased farmers’ WTP for precision pesticide technologies. Moreover, nonlinear relationships between age, agricultural experience, and farmers’ WTA and WTP for precision pesticide technology services were found. 相似文献
116.
We conducted 30- and 60-d greenhouse experiments to compare functional traits of Bromus tectorum (invasive annual grass) and four perennial bunchgrasses under well-watered or drought conditions. Even under drought, B. tectorum experienced significantly less stress (i.e., higher xylem pressure potential and greater shoot water content, water use per day and water-use efficiency) and biomass production than the perennial grasses after 30 d. However, after 60 d, its superiority was reduced under infrequent watering. Differences among perennial grasses were more pronounced for physiological traits under infrequent watering and for morphological traits under frequent watering. Elymus multisetus (fast-growing species) had a higher transpiration rate, lower leaf temperature, and lower water-use efficiency than the other grasses after 30 d. In contrast, Pseudoroegneria spicata (slow-growing) had lower xylem pressure potential and higher leaf temperature than all other grasses under infrequent watering. Under frequent watering, shoot dry mass and specific leaf area of B. tectorum was matched by Elymus wawawaiensis (moderate-growing species). Our results indicate that multiple-species plantings or seedings are necessary to foster greater weed resistance against B. tectorum. We also emphasize that when choosing plant material for restoration, performance during both pulse (resource-rich) and inter-pulse (resource-poor) periods should be considered. 相似文献
117.
Is observed variability in the long-term results of the Continuous Plankton Recorder survey a response to climate change? 总被引:10,自引:1,他引:9
In the more than 50 years that the Continuous Plankton Recorder (CPR) survey has operated on a regular monthly basis in the north-east Atlantic and North Sea, large changes have been witnessed in the planktonic ecosystem. These changes have taken the form of long-term trends in abundance for certain species or stepwise changes for others, and in many cases are correlated with a mode of climatic variability in the North Atlantic, either: (1) the North Atlantic Oscillation (NAO), a basin-scale atmospheric alteration of the pressure field between the Azores high pressure cell and the Icelandic Low; or (2) the Gulf Stream Index (GSI), which measures the latitudinal position of the north wall of the Gulf Stream. Recent work has shown that the changes in the GSI are coupled with the NAO and Pacific Southern Oscillation with a 2 year lag. The plankton variability is also possibly linked to changes observed in the distribution and flux of water masses in the surface, intermediate and deep waters of the North Atlantic. For example, in the last two decades, the extent and location of the formation of North Atlantic Deep Water, Labrador Sea Intermediate Water and Norwegian Sea intermediate and upper-layer water has altered considerably. This paper discusses the extent to which observed changes in plankton abundance and distribution may be linked to this basin-scale variability in hydrodynamics. The results are also placed within the context of global climate warming and the possible effects of the observed melting of Arctic permafrost and sea ice on the subpolar North Atlantic. 相似文献
118.
119.
Antonius G. T. SCHUT Emily C. COOLEDGE Marc MORAINE Gerrie W. J. VAN DE VEN Davey L. JONES David R. CHADWICK 《农业科学与工程前沿(英文版)》2021,8(1):111-129
120.
Fate of low-molecular-weight organic phosphorus compounds in the P-rich and P-poor paddy soils
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LI Bao-zhen Anna GUNINA Mostafa ZHRAN Davey L. JONES Paul W. HILL HU Ya-jun GE Ti-da WU Jin-shui 《农业科学学报》2021,20(9):2526-2534
Continuous application of organic fertilizers can cause accumulation of organic phosphorus(P) in soil, especially in the lowmolecular-weight organic phosphorus(LMWOP) forms. This organic P pool represents a potentially important source of P for both plants and microorganisms. To understand the effect of long-term fertilization(30 years)(P-rich soil) vs. fallowing(P-poor soil) on the bioavailability and fate of LMWOP in subtropical paddy soils, we determined the sorption and mineralization of 14 C-labeled adenosine, adenosine monophosphate(AMP), adenosine diphosphate(ADP), and adenosine triphosphate(ATP) in each soil. The contents of carbon, nitrogen, and P in the P-rich soil were more than two times greater than those in the P-poor soil. The mineralization rates of the LMWOP compounds were faster in the P-rich soil compared to the P-poor soil, and followed the order AMPADPATP. Using sterilized soil, all forms of adenosine-P were strongly sorbed to the solid phase and reached saturation in a short time, with the adsorbance increasing with the number of phosphate groups. We concluded that the mineralization of LMWOP compounds was repressed slightly by sorption to the solid phase, but only in the short term. Thus, LMWOP compounds serve as readily available sources of C for microorganisms, making P available for themselves as well as for the plants. However, P accumulation and the progressive saturation of the P sorption sites in highly fertile soils may increase the potential risk of P runoff. 相似文献