全文获取类型
收费全文 | 459篇 |
免费 | 26篇 |
专业分类
林业 | 9篇 |
农学 | 33篇 |
60篇 | |
综合类 | 32篇 |
农作物 | 26篇 |
水产渔业 | 28篇 |
畜牧兽医 | 283篇 |
植物保护 | 14篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 12篇 |
2016年 | 5篇 |
2015年 | 14篇 |
2014年 | 12篇 |
2013年 | 20篇 |
2012年 | 29篇 |
2011年 | 22篇 |
2010年 | 21篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 23篇 |
2006年 | 15篇 |
2005年 | 18篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有485条查询结果,搜索用时 31 毫秒
81.
Effect of cross-linking agent structure on the shape memory property of polyurethane block copolymer
Effect of cross-linking agent on the shape memory and mechanical property of polyurethane (PU) block copolymer is comprehensively
investigated. The selected chemical cross-linking agents are glycerol, 1,2,6-trihydroxyhexane, and 2,4,6-trihydroxybenzaldehyde
that are differentiated from each other in having remote hydroxyl group and aromatic ring. Significant increase in maximum
stress was observed for all of the cross-linked PUs, although the cross-linker structure was different. Structural change
of PU after cross-linking as evidenced by differential scanning calorimetry and infrared spectra was not detected, suggesting
that interaction between PU chains remained intact. Shape recovery went to as high as 95 % after cross-linking for all of
the cross-linking agents, and shape retention did not improve even if cross-linker was used. The remarkable increase in shape
recovery and maximum stress definitely originated from the employment of a cross-linking agent, and the effect of different
cross-linker structure on shape memory and mechanical property is discussed. 相似文献
82.
Genome-wide analysis of root hair-preferential genes in rice 总被引:1,自引:0,他引:1
83.
Hyunwoo Kang Jongpil Moon Yongchul Shin Jichul Ryu Dong Hyuk Kum Chunhwa Jang Joongdae Choi Dong Soo Kong Kyoung Jae Lim 《Paddy and Water Environment》2016,14(4):499-508
To secure accuracy in the Soil and Water Assessment Tool (SWAT) simulation for various hydrology and water quality studies, calibration and validation should be performed. When calibrating and validating the SWAT model with measured data, the Nash–Sutcliffe efficiency (NSE) is widely used, and is also used as a goal function of auto-calibration in the current SWAT model (SWAT ver. 2009). However, the NSE value has been known to be influenced by high values within a given dataset, at the cost of the accuracy in estimated lower flow values. Furthermore, the NSE is unable to consider direct runoff and baseflow separately. In this study, the existing SWAT auto-calibration was modified with direct runoff separation and flow clustering calibration, and current and modified SWAT auto-calibration were applied to the Soyanggang-dam watershed in South Korea. As a result, the NSE values for total streamflow, high flow, and low flow groups in direct runoff, and baseflow estimated through modified SWAT auto-calibration were 0.84, 0.34, 0.09, and 0.90, respectively. The NSE values of current SWAT auto-calibration were 0.83, 0.47, ?0.14, and 0.90, respectively. As shown in this study, the modified SWAT auto-calibration shows better calibration results than current SWAT auto-calibration. With these capabilities, the SWAT-estimated flow matched the measured flow data well for the entire flow regime. The modified SWAT auto-calibration module developed in this study will provide a very efficient tool for the accurate simulation of hydrology, sediment transport, and water quality with no additional input datasets. 相似文献
84.
85.
Objective To determine the prevalence of mastitis pathogens in high‐producing intensive dairy herds in New South Wales. Design Field survey. Procedure Milk samples from the mastitis‐affected quarter were collected from cows on five high‐producing dairy farms in NSW. The 820 samples were cultured using standard microbiological culture techniques. Results Bacteria or fungi were isolated from 83.3% of samples (683/820). More than two colony types were isolated from 16.7% of samples (137/820), two types from 6.6% (54/820), and one type from 52.3% (429/820). No bacteria were isolated from 24.4% (200/820) of the primary cultures, but enrichment cultures of these samples yielded single colony type bacterial isolates from 36.5% (73/200) of samples. Environmental pathogens, including coliforms, environmental Streptococcus and Staphylococcus spp., made up 91% (555/610) of isolates and accounted for 33.6% (205/610), 41.6% (254/610) and 15.7% (96/610), respectively, of isolates. Escherichia coli accounted for 76.1% (156/205) of the coliform isolates, Streptococcus uberis and Streptococcus dysgalactiae accounted for 32.3% (82/254) and 28.0% (71/254), respectively, of the environmental streptococcal isolates. Contagious pathogens were uncommon, comprising only 2.5% (15/610) of the total isolates. Conclusion The incidence and causes of mastitis are largely influenced by farm management. The relatively high prevalence of coliform mastitis in the intensive high‐producing herds in this survey contrasts with the low incidence reported in surveys of pasture‐based herds in Victoria. If the Australian dairy industry continues its current trend of intensification, coliform intra‐mammary infections may emerge as an increasingly important cause of mastitis. 相似文献
86.
Surgical resection of a dysgerminoma in a mare 总被引:1,自引:1,他引:0
A mare was referred for further evaluation of a mass found in the left caudal abdomen during a routine postpartum reproductive palpation. The mare was clinically normal with no history of health problems. Ultrasonographic examination of the mass confirmed its presence, but the origin of the mass could not be accurately determined. Routine haematology and serum biochemistry results were within normal limits. The mare was initially treated conservatively with antibiotics, but the mass continued to increase in size, so it was surgically excised. The mass involved the left ovary. The mare showed transient abdominal pain after surgery, but developed no other complications and was in foal 7 months later. On histology, the mass was diagnosed as a dysgerminoma, a rare ovarian tumour of germ cell origin. 相似文献
87.
Hye Kwon Kim Jeong Sun Yang Hyoung Joon Moon Seong Jun Park Yuzi Luo Chul Seung Lee Dae Sub Song Bo Kyu Kang Soo Kyung Ann Chan Hyuk Jun Bong Kyun Park 《Journal of veterinary science (Suw?n-si, Korea)》2009,10(2):121-130
The 23 open reading frame (ORF) 5 sequences of Korean type II porcine reproductive and respiratory syndrome virus (PRRSV) were collected from viremic sera from the (modified live vaccine) MLV-vaccinating and non-vaccinating farms from 2007 to 2008. The samples were phylogenetically analyzed with previous ORF5 sequences, including type I Korean PRRSV, and previously reported or collected sequences from 1997 to 2008. A MN184-like subgroup of type II Korean PRRSV was newly identified in the viremic sera collected from 2007 to 2008. And of the type I PRRSVs, one subgroup had 87.2~88.9% similarity with the Lelystad virus, showing a close relationship with the 27~2003 strain of Spain. The maximum parsimony tree of type II PRRSV from 1997 to 2008 showed that they had evolved to four lineages, subgroups 1, 2, 3 and 4. Most of the recently collected type II PRRSVs belonged to subgroup 4 (48%). The region of three B-cell epitopes and two T-cell epitopes of ORF5 amino acids sequences was considerably different from the MLV in subgroups 3 and 4. In conclusion, the existence of type I PRRSV, which was genetically different from Lelystad virus (Prototype of type I PRRSV), and heterologous type II PRRSVs of viremic pigs detected even in the MLV-vaccinating farms indicated the need for new vaccine approaches for the control of PRRSV in Korea. 相似文献
88.
89.
90.
Tae Hwan Jun Min Ji Kim Sungyoun Kim Young Hwa Jung Hak-Ryong Moon Kwang-Soo Kim 《Water, air, and soil pollution》2017,228(3):110
Activated carbon-coated electrode was developed and applied in electrostatic precipitator to remove volatile organic compound gases simultaneously with dust particles from a contaminated air. The activated carbon coating mixture was made up of powdered activated carbon (AC), carbon black (CB), and polyvinyl acetate (PVA), and methanol was added as a solvent to control the thickness of the mixture for best coating performance. During the coating process, the Brunauer-Emmett-Teller (BET) surface decreased to 86% of the original AC while pore volume percentages of macro pore increased, compared to micro- and meso-sized pores. The adsorption isotherm of benzene, toluene, ethyl benzene, and xylene (BTEX) gases onto the original AC and AC coating mixture (AC thoroughly mixed with PVA and methanol for coating and powdered again after dry) were tested and compared to each other, and it was found that both isotherm were best fitted to Freundlich and Langmuir isotherm with the order of adsorption capacities; ethyl benzene?>?m-xylene?>?toluene?>?benzene. The difference between adsorption capacities was clearer with the absorbent AC but became little with the AC coating mixture. In removing BTEX at increasing linear velocities up to 6.7 cm/s, it appeared that the surface area of AC electrode was directly proportional to its removal rate of BTEX. The thermal desorption was applied to regenerate the AC electrode, and 200 °C was found to be most efficient for benzene desorption, but higher temperature would be required for entire BTEX gases desorption. 相似文献