全文获取类型
收费全文 | 852篇 |
免费 | 79篇 |
专业分类
林业 | 43篇 |
农学 | 27篇 |
107篇 | |
综合类 | 95篇 |
农作物 | 17篇 |
水产渔业 | 65篇 |
畜牧兽医 | 492篇 |
园艺 | 21篇 |
植物保护 | 64篇 |
出版年
2024年 | 6篇 |
2023年 | 17篇 |
2022年 | 18篇 |
2021年 | 49篇 |
2020年 | 51篇 |
2019年 | 42篇 |
2018年 | 46篇 |
2017年 | 38篇 |
2016年 | 44篇 |
2015年 | 27篇 |
2014年 | 45篇 |
2013年 | 32篇 |
2012年 | 63篇 |
2011年 | 83篇 |
2010年 | 34篇 |
2009年 | 28篇 |
2008年 | 47篇 |
2007年 | 60篇 |
2006年 | 42篇 |
2005年 | 31篇 |
2004年 | 25篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 2篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1957年 | 1篇 |
1939年 | 1篇 |
1881年 | 3篇 |
1880年 | 1篇 |
排序方式: 共有931条查询结果,搜索用时 18 毫秒
921.
Yang YU Wen-sheng HOU Yael Hacham Shi SUN Cun-xiang WU Ifat Matityahu Shi-kui SONG Rachel Amir Tian-fu HAN 《农业科学学报》2018,17(1):54-62
Soybean(Glycine max(L.) Merr.) is a major crop that provides plant-origin protein and oil for humans and livestock.Although the soybean vegetative tissues and seeds provide a major source of high-quality protein,they suffer from low concentration of an essential sulfur-containing amino acid,methionine,which significantly limits their nutritional quality.The level of methionine is mainly controlled by the first unique enzyme of methionine synthesis,cystathione γ-synthase(CGS).Aiming to elevate methionine level in vegetative tissues and seeds,we constitutively over-expressed a feedback-insensitive Arabidopsis CGS(At D-CGS) in soybean cultivars,Zigongdongdou(ZD) and Jilinxiaoli 1(JX).The levels of soluble methionine increased remarkably in leaves of transgenic soybeans compared to wild-type plants(6.6-and 7.3-fold in two transgenic ZD lines,and 3.7-fold in one transgenic JX line).Furthermore,the total methionine contents were significantly increased in seeds of the transgenic ZD lines(1.5-to 4.8-fold increase) and the transgenic JX lines(1.3-to 2.3-fold increase) than in the wild type.The protein contents of the transgenic soybean seeds were significantly elevated compared to the wild type,suggesting that the scarcity of methionine in soybeans may limit protein accumulation in soybean seeds.The increased protein content did not alter the profile of major storage proteins in the seeds.Generally,this study provides a promising strategy to increase the levels of methionine and protein in soybean through the breeding programs. 相似文献
922.
Heather L. Matthees Yangbo He Rachel K. Owen David Hopkins Bob Deutsch John Lee 《Communications in Soil Science and Plant Analysis》2017,48(18):2148-2154
Since 1954, the electrical conductivity of the saturated paste extract (ECe) has been the preferred index for soil salinity. Based on this value, remediation strategies were developed and widely used but this approach is time consuming and not routinely offered by many soil testing facilities. However, many laboratories determine the EC1:1 value of a 1:1 soil to solution ratio extract. The objective of this study was to identify the relationship between ECe and EC1:1 and determine if EC1:1 can be used as a proxy in the northern Great Plains for ECe. Samples were collected across five studies and from AGVISE Laboratory. The samples were analyzed for EC1:1 and ECe. The relationship between the ECe and EC1:1 showed that soil parent materials need to be considered in the conversion of EC1:1 values to ECe values. A failure to consider parent materials in this conversion may have short and long-term sustainability ramifications. 相似文献
923.
Luiz Carlos De Santana Ribeiro Morais Correia De Melo Assunção Laudenor Luiz Carlos Day Gama Amir B. Ferreira Neto 《Growth and change》2023,54(3):674-693
This paper aims at estimating the regional and sectoral impacts of the Covid-19 pandemic in the state of Sergipe, Brazil in 2020. We use an input-output model with partial hypothetical extraction. The main results suggest a significant reduction in economic activity in the state, particularly in the Transport and Industry sectors. On the other hand, the Real estate and Food and Accommodation sectors have a greater capacity for recovery with the introduction of an emergency aid program. The municipalities with the largest absolute impact on gross domestic product are Aracaju, Canindé de São Francisco and Nossa Senhora do Socorro, two of them located in the metropolitan area of Aracaju. 相似文献
924.
Emílio Mateus Costa Melo Simone Sühnel Ana Cristina Santos de Oliveira Brenda de Oliveira Lopes Gabriela Costa Bachi Claudio Manoel Rodrigues De Melo 《Aquaculture Research》2020,51(9):3631-3640
This work aimed to evaluate the whole weight (g), shell height (mm), mortality (%) and reproductive aspects (condition index and histology) of triploid (3N) Pacific oysters (Crassostrea gigas) cultivated in southern Brazil. To accomplish this, a comparative experiment was performed with a diploid (2N) control group in two cultivation sites on Santa Catarina Island: North Bay (NB) and South Bay (SB). Whole weight, height and cumulative mortality were evaluated monthly for eight months and condition index (CI) for six months. Histological analysis was performed every two weeks for four months to investigate reproductive aspects. At the end of the experiment, whole weight and height were similar for 3N and 2N oysters. However, while more growth in whole weight and height was observed in the initial phase of cultivation in NB, such growth was not detected in SB until intermediate and final grow‐out phase. At harvest, cumulative mortality in 3N oysters was similar that in 2N oysters. The results suggest that diploid and triploid oysters grown in southern Brazil have similar developmental patterns based on whole weight and height, as well as reproductive cycle. In addition, cultivation sites have more influence on growth and mortality than ploidy levels. 相似文献
925.
Renilde Cordeiro de Souza Elizngela Maria de Souza Mateus Matiuzzi da Costa Jos Fernando Bibiano Melo Bernardo Baldisserotto Carlos Eduardo Copatti 《Aquaculture Nutrition》2019,25(1):39-45
The objective of this study was to evaluate the effect of dietary addition of the essential oil from Lippia alba (EOLA) on growth performance, biochemical and haematological variables and survival after Aeromonas spp. infection of Nile tilapia juveniles (Oreochromis niloticus). Five diets were evaluated with increasing levels of EOLA (0.0 control; 0.25; 0.50; 1.0; and 2.0 ml/kg diet). After 45 days of feeding, the fish were infected with Aeromonas spp. followed by a 14‐day period of observation. There was no mortality during growth assessment. The addition of 2.0 ml EOLA/kg diet improved feed conversion ratio and condition factor and increased lysozyme activity and haematocrit (Hct), and decreased plasma globulin levels compared to the control group. The survival of fish infected with Aeromonas spp. was higher in those fed with 2.0 ml EOLA/kg diet than in fish fed with 0.0–0.5 ml EOLA/kg diet. We concluded that the inclusion of 2.0 ml EOLA/kg diet is recommended for Nile tilapia juveniles, because it improved feed conversion, Hct and immunological activity, did not provoke metabolic changes, and increased survival after Aeromonas spp. infection. 相似文献
926.
Anderson Miranda de Souza Adailton Thiago Silva Altiery Felix e Silva Daniela Ferraz Bacconi Campeche Jos Fernando Bibiano Melo Luiz Vítor Oliveira Vidal 《Aquaculture Research》2019,50(1):49-62
Two experiments were conducted to assess the nutritional value and potential use of mesquite bean (Prosopis juliflora) meal (MBM) to substitute corn in extruded diets for Nile tilapia (Oreochromis niloticus). Digestible energy and the content of protein, soluble carbohydrates and amino acids were measured for 160 Nile tilapia juveniles (average weight 25.58 ± 5.52 g), allocated to eight treatment groups (four fed the experimental diet, and four fed a reference diet). To determine the inclusion potential of MBM, 384 fish (average weight 21.85 ± 1.01 g) were used and allocated to 24 tanks (1,000 L capacity). The experimental design was completely randomized with six levels of substitution (0%, 20%, 40%, 60%, 80% and 100%), and four repetitions. After the feeding experiment, tissue samples (blood, liver, muscle and intestine) were used to analyse metabolic and haematological variables. MBM produced apparent digestibility coefficients (ADC) similar to those of traditional diet ingredients: 81.85% dry matter (DM), 83.02% crude energy, 88.57% crude protein, 82.88% lysine and 82.57% methionine. Differences were observed in the digestibility of soluble carbohydrates (p < 0.05), with MBM having higher levels of starch (72.19%) and sucrose (88.99%). A 20% substitution with MBM produced a decrease in zootechnical performance (p < 0.05). Enzymatic activity of amylase and sucrose seemed to be induced in response to the proportion of their respective substrate in the diets. We observed a reduction in the efficiency of dietary protein utilization, with reduced levels of plasma amino acids (p < 0.05), owing to the increase in the enzymatic activity of muscular alanine and aspartate transaminases (ALT and AST) and the deaminase glutamate dehydrogenase in the hepatic and muscular tissues. Haematological variables did not indicate any adverse effects of MBM on the health status or survival of the fish (100%). Therefore, we conclude that MBM may be a viable alternative to corn meal in the diet, enabling substitution of up to 20%. 相似文献
927.
928.
929.
Maíra Harumi Higa Lage Júlia Augusta Rocha Pozavski Alysson Rodrigo Lamounier Eliane Gonçalves de Melo 《Anatomia, histologia, embryologia》2023,52(2):197-203
A bilateral patellar agenesis is an extremely rare congenital condition in which the patient does not develop both patellas and can present secondary alterations as bone, muscle and postural changes. There are some hypotheses that it has a genetic background presenting dominant characteristic. It is not yet standardized a gold treatment for this affection, but according to rare reports, clinical and surgical treatments are possible. This is a case report based on imagining exams of a mix breed male puppy that was born with bilateral patellar agenesis, an affection not yet reported in canine species. 相似文献
930.
Rachel N. Hofer Allen Lin Benjamin C. House Christopher N. Purvis Bradley J. Harris Steven J. K. Symes David K. Giles 《Journal of fish diseases》2023,46(1):31-45
Aeromonas salmonicida is a Gram-negative bacterium that can infect a wide host range of fish populations, including salmonids and non-salmonids as well as freshwater and marine life. Some strains of A. salmonicida cause the disease furunculosis, which can cause lethargy, intestinal inflammation, ulcers, haemorrhaging and death. The infection is spread through fish-to-fish contact, and the presence of infection can have devastating effects on cultivated fish populations. The purpose of this study was to explore the ability of non-A-layer and A-layer A. salmonicida strains to incorporate polyunsaturated fatty acids (PUFAs) into their lipid profile and test the phenotypic effects thereof. Lipids were extracted from PUFA-exposed cultures and analysed for lipid modification by thin-layer chromatography and ultraperformance liquid chromatography-mass spectrometry, showing A. salmonicida, regardless of A-layer, capable of incorporating all seven of the PUFAs studied. Phenotypic effects were determined through the use of assays that tested for biofilm formation, membrane permeability and cyclic peptide susceptibility. Temperature-dependent effects on biofilm formation were observed, and PUFA exposure showed significant (p < .001) increases in membrane permeability as tested by the uptake of the hydrophobic compounds crystal violet and ethidium bromide. Additionally, some PUFAs elicited modest protection and vulnerability against the membrane-targeting cyclic peptides polymyxin B (PMB) and colistin. The diverse, strain-specific responses to exogenous PUFAs may allude to evolved adaptive strategies that enhance survival, persistence and virulence of non-pathogenic and pathogenic members of bacteria that oscillate between environmental and fish host niches. 相似文献