全文获取类型
收费全文 | 557篇 |
免费 | 46篇 |
国内免费 | 4篇 |
专业分类
林业 | 55篇 |
农学 | 28篇 |
基础科学 | 10篇 |
120篇 | |
综合类 | 40篇 |
农作物 | 51篇 |
水产渔业 | 93篇 |
畜牧兽医 | 160篇 |
园艺 | 12篇 |
植物保护 | 38篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 18篇 |
2021年 | 35篇 |
2020年 | 29篇 |
2019年 | 40篇 |
2018年 | 46篇 |
2017年 | 42篇 |
2016年 | 28篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 39篇 |
2012年 | 32篇 |
2011年 | 28篇 |
2010年 | 25篇 |
2009年 | 27篇 |
2008年 | 16篇 |
2007年 | 24篇 |
2006年 | 29篇 |
2005年 | 24篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1965年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有607条查询结果,搜索用时 15 毫秒
101.
Tatsuya Nakayama Michio Jinnai Ryuji Kawahara Khong Thi Diep Nguyen Nam Thang Tran Thi Hoa Le Kieu Hanh Pham Ngoc Khai Yoshinori Sumimura Yoshimasa Yamamoto 《Tropical animal health and production》2017,49(1):31-37
Reports of livestock infections with extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-E) are increasing. Based on interviews conducted over a 6-month period, we found that veterinarians in the Vietnamese province of Thai Binh prefer to prescribe colistin-based drugs (CBD) in chicken farms. We aimed to clarify whether CBD use selects for strains of colistin-resistant ESBL-E. With the cooperation of seven local households, we detected ESBL-E in chickens’ feces after treating chickens with CBD. Phylogenetic groupings and the presence of CTX-M/AmpC genes were determined, and the multi-antibiotic susceptibility of isolates was analyzed. Our results showed that ESBL-E presented in seven chickens’ feces from two households. Seventy-two percent of ESBL-E isolates harbored CTX-M9 and the phylogenetic group A; the colistin minimum inhibitory concentration (MIC) of all isolated ESBL-E ranged from 0.064 to 1 μg mL?1. Moreover, ESBL-E isolates were used to experimentally select for colistin resistance, and the effect of commercial CBD on ESBL-E was investigated. The results showed that an ESBL-E strain with a colistin MIC of 4 μg mL?1 was able to grow in media with CBD. Although CBD treatment was effective, in vitro experiments demonstrated that ESBL-E can easily acquire colistin resistance. Therefore, restrictions on colistin use are necessary to prevent the emergence of colistin-resistant bacteria. 相似文献
102.
A field experiment was conducted to investigate the impact of simulated rat damage on grain yield in irrigated lowland rice in An Giang province, in the Mekong Delta of Vietnam. Rat damage was simulated by making a 45° cut at the base of the rice tillers about 3–5 cm above the soil surface. 0% (control), 5%, 10%, 25% and 50% of the tillers were removed at the tillering (25 days after sowing, DAS), panicle initiation (43 DAS), flowering (72 DAS) and ripening (87 DAS) stages. The total number of mature tillers, immature tillers and percent filled grains, the weight of 1000 grains and grain yields were recorded. The rice crop completely compensated by increased tillering and yield for tillers damaged up to 50% at the tillering stage. However, the damage and yield loss were highly variable. The ability of the rice crop to compensate at later stages progressively reduced. The implications for managing rat damage to rice crops are (1) rodent control activities should be applied before 10% of tillers are damaged at the tillering stage, and (2) a well balanced nitrogen supply during the tillering stage could potentially assist the rice plants to better compensate for rat damage. 相似文献
103.
Tran Ho Quang Nguyen Duc Kien Sara von Arnold Gunnar Jansson Ha Huy Thinh David Clapham 《New Forests》2010,39(3):301-312
Lignin and cellulose contents and wood basic density were related to diameter at breast height (DBH) in six fast-growing and
five slow-growing families from a combined progeny test and seedling seed orchard of Eucalyptus urophylla grown for 10 years in northern Vietnam. The mean cellulose content of the fast-growing families was significantly higher
than that of the slow growing-families (40.0 and 37.1%, respectively), and for individual trees cellulose content was significantly
correlated phenotypically with DBH. Wood basic density was significantly lower in the fast-growing group than in the slow-growing
group (0.506 and 0.535 g cm−3, respectively), and was significantly negatively correlated phenotypically with DBH. The lignin contents were not significantly
different between groups. Cellulose content and wood basic density were not correlated. The main conclusion is that there
is no obstacle to combining high growth rate with high cellulose content, for plantation of forests intended mainly for pulpwood. 相似文献
104.
Pham Thi Anh Ngoc Miranda P. M. Meuwissen Le Cong Tru Roel H. Bosma Johan Verreth Alfons Oude Lansink 《Aquaculture Economics & Management (Blackwell Science)》2016,20(2):185-200
This study aims to analyze the economic feasibility of recirculating aquaculture systems (RAS) in pangasius farming in Vietnam. The study uses a capital budgeting approach and accounts for uncertainty in key parameters. Stochastic simulation is used to simulate the economic performance of medium and large farms operating with a traditional system or RAS. Data are obtained through structured surveys and a workshop in the Mekong River Delta. Results show that for large farms, net present value increases from an average of 589,000 USD/ha to 916,000 USD/ha after implementing RAS. Overall, the probability that RAS is a profitable investment is found to be 99% for both farm sizes. With RAS, the crucial parameters determining profitability are price, yield, costs of fingerling, feed, and initial investment. Findings on the robustness of the economic performance of RAS are useful to support public and private decision making towards increasing the sustainability of pangasius production. 相似文献
105.
Hai Thi Hong Truong Hung Ngoc Tran Hak Soon Choi Pue Hee Park Hye Eun Lee 《European journal of plant pathology / European Foundation for Plant Pathology》2013,136(2):237-245
Random amplified polymorphism DNA (RAPD) and bulk segregant analysis (BSA) approaches were used to characterize the molecular marker linked to the Phytophthora infestans resistance gene Ph-3 in tomato. A total of 800 RAPD primers were screened. One RAPD marker UBC#602 was identified to be tightly linked to the Ph-3 gene. The marker was successfully converted into a co-dominant sequence characterized amplified region (SCAR) marker. The SCAR marker SCU602 was used to analyze 96 F2 progenies and fitted the expected 1:2:1 Mendelian segregation ratio. Forty one tomato inbred lines were screened using the SCAR marker in comparison with a reference marker linked to the Ph-3 gene and both markers gave the same results. SCU602 was further validated for association to resistance and its potential in MAS in 72 tomato lines and cultivars. The marker identified three genotypes harbouring the resistance allele. This SCAR marker can be used in breeding programs for the selection of the Ph-3 gene for Phytophthora infestans resistance. 相似文献
106.
Ostezan Alexandra McDonald Samuel Clay Tran Dung Thuy Souza Renan Silva E Li Zenglu 《Journal of Crop Science and Biotechnology》2021,24(1):13-26
Journal of Crop Science and Biotechnology - Fine mapping quantitative trait loci (QTL) and understanding the molecular mechanism and underlying functions of genes are vital to the advancement of... 相似文献
107.
Pascal Jouquet Ga?lle Huchet Nicolas Bottinelli Thuy Doan Thu Toan Tran Duc 《Biology and Fertility of Soils》2012,48(5):561-567
Soil compaction has a negative impact on both earthworm abundance and diversity. Recent studies, however, suggest that earthworm cast properties are not influenced by the initial soil bulk density. With time, earthworms could therefore transform soils with different bulk densities into a soil with the same physical state and thus with a similar ecological functioning. This study aimed to test this hypothesis in two laboratory incubation experiments. First, we measured the influence of soil bulk density (1.1 or 1.4?g?cm?3) on the production of cast by the endogeic earthworm species Metaphire posthuma. In a second experiment, we investigated the effect of M. posthuma on water infiltration, NH 4 + , and NO 3 ? leaching and soil respiration at the same two soil bulk densities. Although initially higher, earthworm casting activity in soil at 1.4?g?cm?3 decreased until it reached the same level of activity as earthworms in soil at 1.1?g?cm?3. This behavioral plasticity led to a transformation of compacted and loose soils, with their own functioning, to a third and similar state with similar hydraulic conductivity, nitrogen leaching, and soil respiration. The consequences for soil organization and soil functioning are discussed. 相似文献
108.
Do?Thi?XuanEmail author Vo?Thi?Guong Anna?Rosling Sadhna?Alstr?m Benli?Chai Nils?H?gberg 《Biology and Fertility of Soils》2012,48(2):217-225
Intensive cropping, especially of rice, is considered to contribute to negative effects not only on soil chemical and biological
properties but also on long-term grain yield. Appropriate crop rotation is often practiced as an alternative strategy to overcome
the negative side effects of intensive cropping. Although soil microbial diversity and community structure have been shown
to respond differently to altered agricultural management practices, little is known about possible links between crop rotation
and grain yield on bacterial communities in rice paddy soil. In this study, we investigated the impact of specific rotational
crops and compared it with intensive rice cultivation. The main crop rice (Oryza sativa) was rotated with maize (Zea mays) and mungbean (Phaseolus aureus) in different combinations in a system cultivating three crops per year. Soil bacterial communities were studied in two different
cropping periods using pyrosequencing of the variable V4 region of the 16S rRNA. Our results showed that rotation with alternative
crops increased rice yield by 24–46% depending on rotation structure and that bacterial community structure was altered in
the presence of mungbean and/or maize compared to that in rice monoculture. In the crop rotation systems, composition, abundance,
and diversity of soil bacterial communities were significantly different and higher than those in rice monoculture. Our results
show that effects of crop rotation relate to changes in soil bacterial community structure suggesting that appropriate crop
rotations provide a feasible practice to maintain the equilibrium in soil microbial environment for sustainable rice cultivation. 相似文献
109.
以毛竹Phyllostachys edulis集成材为研究对象,在不同条件下进行高频热压,通过对竹集成材板坯高频热压过程中芯层温度变化的统计分析,得到了竹集成材高频热压过程中板坯温度的变化规律。结果表明:在试验条件范围内,随着板坯含水率从6%增加到18%,涂胶量从200 g·m-2增加到300 g·m-2,板坯的温度明显升高。升温过程可以分为快速升温和慢速升温2个阶段。在快速升温阶段板坯内的温度随板坯初含水率、涂胶量及加热时间的提高而递增;在慢速升温阶段板坯初含水率及涂胶量对板坯内的温度的影响很小,板坯芯层升温速度随加热时间的增加而减少。通过试验数据分析,得出较优的高频热压胶合工艺条件为:涂胶量300 g·m-2,竹条含水率12%,高频热压时间7 min。 相似文献
110.
Le TT Miocinovic J Nguyen TM Rombaut R van Camp J Dewettinck K 《Journal of agricultural and food chemistry》2011,59(19):10407-10413
A normal-phase high-performance liquid chromatography-evaporative light-scattering detector method employing dichloromethane, methanol, and acetic acid/triethylamine buffer as the mobile phase was developed for analysis of polar lipids (PLs). This method was applicable for analysis of PLs from both dairy materials and soy lecithin. All of the PLs of interest such as glycolipids, phospholipids, and sphingomyelin were well separated with a total run time of 22.5 min and without necessitating the removal of neutral lipids beforehand. Peak retention times were stable, and the method was reproducible. In this study, a modified method of using solvents for extraction of PLs from dairy matrices was also investigated. The modified method offered higher extraction efficiency, consumed less time, and in some cases saved solvent use. 相似文献