全文获取类型
收费全文 | 512篇 |
免费 | 30篇 |
专业分类
林业 | 20篇 |
农学 | 15篇 |
基础科学 | 8篇 |
101篇 | |
综合类 | 31篇 |
农作物 | 15篇 |
水产渔业 | 33篇 |
畜牧兽医 | 266篇 |
园艺 | 14篇 |
植物保护 | 39篇 |
出版年
2024年 | 6篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 8篇 |
2015年 | 18篇 |
2014年 | 17篇 |
2013年 | 28篇 |
2012年 | 37篇 |
2011年 | 35篇 |
2010年 | 28篇 |
2009年 | 30篇 |
2008年 | 40篇 |
2007年 | 43篇 |
2006年 | 29篇 |
2005年 | 27篇 |
2004年 | 21篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有542条查询结果,搜索用时 15 毫秒
81.
Sara Hueso Gennaro Brunetti Nicola Senesi Karam Farrag Teresa Hernández Carlos García 《Journal of Soils and Sediments》2012,12(4):503-512
Purpose
The objective of this work was to assess the effect of severe drought conditions on the characteristics of semiarid soil humic acids (HAs) as well as the effect of organic amendment on such changes. 相似文献82.
Daniele Zaccaria Nicola Lamaddalena Christopher M. U. Neale Gary P. Merkley 《Irrigation Science》2013,31(3):193-208
A deterministic–stochastic combined model named HydroGEN was developed, as described in a companion paper (Part I: Model development), to enable the simulation of demanded daily volumes and hourly flow rates during peak periods in pressurized irrigation delivery networks. The model was applied to a pilot large-scale irrigation system located in southern Italy for calibration and for testing its reliability in analyzing the operation of large-scale pressurized delivery systems through the simulated flow configurations. Daily input data on rainfall, temperature, solar radiation, wind speed and relative humidity were gathered from a meteorological station located within the study area, whereas information on local irrigation management practices were collected through interviews with farmers and from extension specialists. The model was tested at different management levels, from district to sector and hydrants. The model testing was supported by the use of high-resolution remote-sensing imagery acquired on a single overpass date in 2006 and then classified and recoded following a ground-truthing campaign conducted during the same year. Simulations were performed to identify the 10-day peak-demand period and to generate the hydrographs of daily volumes and of hourly flow rates. Results from the different simulations were compared with historical datasets of irrigation volumes and discharges recorded during the 2008 and 2009 seasons at the upstream end of the irrigation network under study, at a sector level during the 2007 season and at selected delivery hydrants during the 2005 season. Some discrepancies between simulated and recorded data were noted that can be related to small errors in estimating crop and soil parameters, application efficiency at field level, as well as to large variability in irrigation management practices followed by local farmers. Overall, the results from testing showed that the model is capable of forecasting with good accuracy the timing of peak-demand periods, the irrigation volumes demanded during the season, as well as the hydrographs of daily volumes and hourly flow rates withdrawn by farmers during these peak-demand periods, especially when it is applied to large multi-cropped command areas. 相似文献
83.
Prashanth SN Bianco G Cataldi TR Iacobellis NS 《Journal of agricultural and food chemistry》2011,59(21):11461-11472
The main bacterial pathogens of cultivated mushroom as well as mushroom-associated bacteria, which were isolated from Agaricus bisporus, Pleurotus ostreatus and Pleurotus eryngii mushroom niches, were evaluated for the production of N-acyl-L-homoserine lactones (AHLs) by using four bioreporters. Furthermore, identification of AHLs by LC-ESI-FTICR MS was performed on culture filtrates of selected pathogens and mushroom-associated bacteria strains, which resulted in inducing at least one of the four bioreporters. Strains of Burkolderia gladioli pv. agariciola, Pseudomonas agarici and Pseudomonas gingeri, but not those of Pseudomonas tolaasii and Pseudomonas reactans, produced an array of AHLs depending on the strain. This is the first report of AHL production by mushroom bacterial pathogens. Forty-four of 236 bacterial isolates obtained from different niches of cultivated mushrooms, in part identified by the Biolog identification system, were demonstrated to produce AHLs. Among them, seven mushroom-associated bacterial species were for the first time demonstrated to produce the above signal molecules. In the culture filtrates of a certain number of isolates/strains the AHL-hydrolyzed forms were also present. The minimal signal inducing concentration (MSIC) of selected pure AHLs was also determined for the four bioreporters used in this study. 相似文献
84.
85.
Duarte Mde S Paulino PV Valadares Filho Sde C Paulino MF Detmann E Zervoudakis JT Monnerat JP Viana Gda S Silva LH Serão NV 《Tropical animal health and production》2011,43(4):877-886
The effects of two levels of concentrate and ruminally undegradable protein (RUP) on performance, intake, digestibility, carcass
characteristics, meat quality traits, and commercial cuts yield were assessed. Twenty crossbred heifers (240 kg average body
weight) were used. At the beginning of the trial, four animals were slaughtered as reference group and the 16 remaining animals
were randomly assigned to four treatments, in a 2 × 2 factorial design: two levels of concentrate (40% and 80%, dry matter
(DM) basis) and two levels of RUP (48.79% and 27.19% of CP). At the end of the trial, all the animals were slaughtered. There
was no interaction (P > 0.05) between concentrate and RUP levels. Dry matter intake and nutrients digestibility was not affected (P > 0.05) by RUP level. Heifers fed the highest RUP level had greater (P < 0.05) average daily gain (ADG). Concentrate level did not affect (P > 0.05) DMI and ADG. Heifers fed diets with 80% concentrate had greater intake of TDN and EE, and lower intake of NDF (P < 0.05). The digestibilities of all nutrients, except the NDF, were greater (P < 0.05) for the 80% concentrate diets. The RUP levels did not affect (P > 0.05) the carcass characteristics and carcass gain composition. Heifers fed 80% concentrate diets had larger (P < 0.05) longissimus muscle area and lower gain of bones (P < 0.05). Concentrate level did not affect (P > 0.05) the composition of carcass gain. There was no effect (P > 0.05) of RUP and concentrate levels on meat quality traits and commercial cut yields. 相似文献
86.
Sibeko KP Collins NE Oosthuizen MC Troskie M Potgieter FT Coetzer JA Geysen D 《Veterinary parasitology》2011,181(2-4):120-130
Restriction fragment length polymorphism analysis of PCR products (PCR-RFLP) and sequencing of the variable region of the p104 and PIM genes was performed on samples obtained from South African T. parva parasites originating from cattle on farms with suspected theileriosis and from buffalo. p104 and PIM PCR-RFLP profiles similar to those of the T. parva Muguga stock, an isolate that causes ECF in Kenya, were obtained from three of seven cattle samples collected on a farm near Ladysmith in KwaZulu-Natal Province. Amino acid sequences of the p104 and PIM genes from two of these samples were almost identical to the T. parva Muguga p104 and PIM sequences. This result supports findings from a recent p67 study in which p67 alleles similar to those of the T. parva Muguga stock were identified from the same samples. While these results suggest the presence of a cattle-derived T. parva parasite, reports of cattle-to-cattle transmission could not be substantiated and ECF was not diagnosed on this farm. Although extensive diversity of p104 and PIM gene sequences from South African T. parva isolates was demonstrated, no sequences identical to known cattle-type p104 and PIM alleles were identified from any of the buffalo T. parva samples analyzed. 'Mixed' PIM alleles containing both cattle- and buffalo-type amino acid motifs were identified for the first time, and there appeared to be selection of cattle-type and 'mixed'-type PIM sequences in the cattle samples examined. 相似文献
87.
88.
89.
90.
The harvested biomass of switchgrass (Panicum virgatum L.) is generally much lower than its potential; this may be due to several factors including not recovering all the biomass at harvest, weed competition, pests, disease and spatial variation of soil features. The objective of this research was to quantify the yield spatial variation of switchgrass and relate it to soil parameters, in a field of about 5 ha, in 2004 and 2005. Several thematic maps of soil parameters and biomass yield were produced using GIS and geostatistical methods. Soil parameters changed consistently within very short distances and biomass yield varied from 3 to more than 20 Mg ha−1. This remarkable variation indicates that the potential for increasing switchgrass productivity is a real prospect. Furthermore, spatial variation of yield showed similar patterns in the 2 years (r = 0.38**), and therefore a major influence of site characteristics on switchgrass yield can be assumed to occur. Significant correlations were found between biomass yield and soil N, P, moisture and pH as well as between soil parameters. Some soil parameters such as sand content showed patchy spatial distribution. Conversely, a reliable spatial dependence could not be identified for other parameters such as P. Further research is needed. 相似文献