全文获取类型
收费全文 | 519篇 |
免费 | 42篇 |
专业分类
林业 | 59篇 |
农学 | 18篇 |
基础科学 | 16篇 |
107篇 | |
综合类 | 13篇 |
农作物 | 93篇 |
水产渔业 | 95篇 |
畜牧兽医 | 122篇 |
园艺 | 11篇 |
植物保护 | 27篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 24篇 |
2020年 | 22篇 |
2019年 | 36篇 |
2018年 | 53篇 |
2017年 | 50篇 |
2016年 | 44篇 |
2015年 | 14篇 |
2014年 | 25篇 |
2013年 | 60篇 |
2012年 | 27篇 |
2011年 | 42篇 |
2010年 | 28篇 |
2009年 | 14篇 |
2008年 | 31篇 |
2007年 | 17篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 9篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有561条查询结果,搜索用时 15 毫秒
81.
Isa Esfandiarpour-Borujeni Seyed Javad Hosseinifard Hossein Shirani Maryam Zeinadini Ali Asghar Besalatpour 《Communications in Soil Science and Plant Analysis》2018,49(12):1474-1490
The main objective of this study was to evaluate the potential use of a hybrid Genetic Algorithm-Artificial Neural Network (GA–ANN) method for predicting pistachio yield and for identifying the determinant factors affecting pistachio yield in Rafsanjan region, Iran. A total of 142 pistachio orchards were selected randomly and soil samples were taken at three depths. Besides, water samples and leaves from branches without fruit were taken in each sampling point. Management information and pistachio yields were achieved by completing a questionnaire. Primarily, 58 variables affecting pistachio yield were measured, and then 26 out of them were selected by minimizing mean square error (MSE) using a feature selection (FS) method. The results showed that the accuracy of the method was acceptable. Furthermore, the sensitivity analysis showed that the main determinant features affecting the pistachio yield were the irrigation water amount, leaf phosphorus, soil soluble magnesium, electrical conductivity (EC), and leaf nitrogen. 相似文献
82.
Sidra Kanwal Sumera Shabir Maimona Saeed Robina Gul Maryum Zahoor 《Journal of plant nutrition》2018,41(4):526-538
Salinity is a major abiotic stress that affects crop production throughout the world. Biochar is an activated carbon soil conditioner that can alleviate the negative impacts of salinity. The research was conducted to evaluate the ameliorative effect of 1% and 2% of biochar application on wheat seed germination and growth attributes under salinity. Both levels of biochar improved the germination and growth conditions under salinity; however, 2% biochar level was more effective compared to 1% level. Root and shoot length increased up to 23% and11% with 2% biochar, respectively. The maximum increase of 16% and 10% in leaf water potential and osmotic potential was noted with 2% biochar at 150 mM salt. The decrease in proline content and soluble sugar at 2% biochar was 51% and 27%, respectively. Decrease in superoxide dismutase activity was 15.3% at 2% level of biochar under stress biochar mitigates the negative effects of salinity and improved wheat productivity. 相似文献
83.
Edris Shabani Sahebali Bolandnazar Seyed Jalal Tabatabaei Nosratollah Najafi Saeedeh Alizadeh-Salteh Youssef Rouphael 《Journal of plant nutrition》2018,41(13):1662-1673
A greenhouse experiment was conducted to assess the effects of magnetic field, arbuscular mycorrhizal fungi (AMF), and phosphorus (P) concentration in the nutrient solution (0, 5, 10, 20, or 40 mg L?1) on the mobility and accumulation of P in soil and plant tissues of basil (Ocimum basilicum L.). The experiment was designed as a factorial combination and treatments were arranged in a completely randomized design with four replicates. Magnetic field increased water-soluble P in the soil and P concentration in plant shoot by 30.0% and 13.0%, respectively, in comparison to the control. The application of magnetic field and inoculation of AMF at 10 mg P L?1 increased the P translocation efficiency by 23.3% and 17.8%, respectively. Overall, our results demonstrated that the use of magnetic field and AMF could be an effective tool for enhancing of uptake and movement efficiency of P even at low concentrations. 相似文献
84.
Muhammad Saeed Daryoush Babazadeh Muhammad Naveed Muhammad Asif Arain Faiz Ul Hassan Sun Chao 《Tropical animal health and production》2017,49(7):1329-1338
Betaine is found ubiquitously in plants, animals, microorganisms, and rich dietary sources including seafood, spinach, and wheat bran. The chief physiological role of betaine is to function as a methyl donor and an osmolyte. Betaine also acts as an osmolyte, to maintain the avian’s cellular water and ion balance to improve the avian’s capacity against heat stress via preventing dehydration and osmotic inactivation. It helps in maintaining the protective osmolytic activity, especially in heat-stressed birds. Betaine may promote various intestinal microbes against osmotic variations and thus improve microbial fermentation activity. Previous studies showed that dietary supplementation of betaine in poultry diets could positively affect nutrients’ digestibility, reduce abdominal fat weight, and increase breast meat yield. In addition, betaine has been reported to protect internal organs and boost their performance. Its inclusion in poultry diet is sparing essential amino acids like choline and methionine. In addition, it may play an important role in lean meat production by positively affecting the lipid metabolism with increased fatty acids catabolism and thus reducing carcass fat deposition. The aim of this review article was to broaden the knowledge regarding betaine and its importance in the poultry industry to cope with the heat stress problem. Moreover, it should be added to the diet as a natural anti-stressor through different routes (water/feed) to overcome the heat stress problem. However, further studies need to be conducted at the genetic and molecular basis to elucidate the mechanism behind the betaine as a natural anti-heat agent to decrease the heat stress problem in the poultry industry. 相似文献
85.
86.
87.
Polyculture of western white shrimp,Litopenaeus vannamei Boone, 1931 with Grey mullet,Mugil cephalus Linnaeus, 1758 controls external parasites of western white shrimp 下载免费PDF全文
Seyyed Hossein Hosseini Aghuzbeni Saeed Hajirezaee Hossein Khara 《Aquaculture Research》2016,47(9):2983-2988
The main aim of this study was to examine the effects of a polyculture system on the control of the external parasites of western white shrimp, Litopenaeus vannamei. To this end, the western white shrimp postlarvae (PLs) were stocked in nine earthen ponds (600 m2) at a density of 20 PLs m?2 and reared for 4 months. After 40 days of shrimp stocking, Mullets, Mugil cephalus, were stocked at various densities including: control (0 fish/100 m2 pond), treatment 1 (T1: 2 fish/100 m2 pond) and treatment 2 (T2: 4 fish/100 m2 pond). Over the course of the experiment, the external parasites of shrimps were investigated by the preparation of a wet mount from the gill tissue. Based on the obtained results, totally two genera of protozoan parasites, i.e. Zoothamnium sp. and Epistylis sp., were identified over the course of the experiment. In all experimental groups, the incidence and abundance of Zoothamnium sp. was significantly higher than Epistylis sp. (P < 0.05). Also, mean incidence per cent and mean abundance of Zoothamnium sp. and Epistylis sp. were significantly lower in the polyculture treatments (T1 and T2) compared to the monoculture group (control) (P < 0.05). Throughout this experiment, the total organic matter (TOM %) content of the bottom sediments and biological oxygen demand (BOD5 mg L?1) of water samples in the polyculture ponds were significantly lower than the monoculture group (P < 0.05). In contrast, the polyculture ponds had a higher concentration of water dissolved oxygen (O2 mg L?1) compared to the monoculture (P < 0.05). In conclusion, our results show that mullet as a secondary farmed species can reduce indirectly the parasitic pollution of western white shrimp probably through reducing the total organic matters in water and sediments and improving the water quality parameters. 相似文献
88.
Muhammad Saeed Akram Muhammad Ashraf Muhammad Shahbaz Nudrat Aisha Akram 《植物养料与土壤学杂志》2009,172(6):884-893
In order to assess the effectiveness of foliar‐applied potassium (K+, 1.25%) using different salts (KCl, KOH, K2CO3, KNO3, KH2PO4, and K2SO4) in ameliorating the inhibitory effect of salt stress on sunflower plants, a greenhouse experiment was conducted. Sodium chloride (150 mM) was applied through the rooting medium to 18 d–old plants and after 1 week of salt treatment; different K+‐containing salts were applied twice in 1‐week interval as a foliar spray. Salt stress adversely affected the growth, yield components, gas exchange, and water relations, and also caused nutrient imbalance in sunflower plants. However, foliar‐applied different sources of potassium improved shoot and root fresh and shoot dry weights, achene yield, 100‐achene weight, photosynthetic rate, transpiration rate, stomatal conductance, water‐use efficiency, relative water content, and leaf and root K+ concentrations of sunflower plants grown under saline conditions. Under nonsaline conditions, improvement in shoot fresh weight, achene yield, 100‐achene weight, photosynthetic and transpiration rates, and root Na+ concentration was observed due to foliar‐applied different K sources. Of the different salts, K2SO4, KH2PO4, KNO3, and K2CO3 were more effective than KCl and KOH in improving growth and some key physiological processes of sunflower plants. 相似文献
89.
Seyed Saeid Hojjat 《Russian Agricultural Sciences》2013,39(2):134-142
One hundred lentil genotypes accessions of Mashhad Lentil Collection (MLC) were evaluated at Chenaran, Iran with three planting dates [10 Oct., 10 Nov. (fall) and 28 Mar. (spring) during 2008/09 growing seasons]. Evaluation based on winter survival percentage showed that in 2008/09 growing season, percentage of highly tolerant, tolerant, moderately tolerant, moderately susceptible and susceptible genotypes were 22, 61, 16, 1 and 0 respectively. In the first planting date more than 50% of genotypes were ranked as highly tolerant, however it was decreased to 12% and 5% of genotypes in the second and third planting dates, respectively, in this year. According to the fall plantings data, the length of growth duration of samples in fall plantings were 2.3 times higher than spring planting, and also in the first planting that was 5, 25 and 255 percent more than 2nd and 3rd planting dates, respectively. The height of fall plants were more than spring plants and in the first year fall planting genotypes were about 38% taller than the same planting. The number of pod per plant in fall planting was 2 times higher than spring planting. More than 22% of accessions had 125 pods per plant in 1st and 2nd planting in this year. In the 2008/09 growing seasons the yield of lentil genotypes in fall planting were more than 4 and about 2 times of spring planting, respectively. In the 2008/09 growing seasons 39% of spring planting samples produced less than 50 gr/m2 seed yield. It seems that the improvement of seed yield in the fall planting were due to suitable winter survival of plants fallowed by better usage of rainfall and escaping from drought and heat stress of the end of spring. Results showed that there were some cold tolerant accessions in MLC and it is possible to provide cold tolerant cultivars for fall planting in Mashhad conditions. 相似文献
90.
Sahar Hatami Saeed Zavareh Mojdeh Salehnia Taghi Lashkarbolouki Mohammad Taghi Ghorbanian Isaac Karimi 《Iranian Biomedical Journal》2014,18(3):181-188
Background: Cryopreservation of pre-antral follicles is a hopeful technique to preserve female fertility. The aim of the present study was to evaluate reactive oxygen species (ROS) and total antioxidant capacity (TAC) levels of mouse vitrified pre-antral follicles in the presence of alpha lipoic acid (ALA). Methods: Isolated pre-antral follicles (140–150 µm in diameter) were divided into vitrified–warmed and fresh groups. Each group was subjected to in vitro maturation with or without ALA for 12 days, followed by adding human chronic gonadotropin to induce ovulation. In vitro fertilization was performed to evaluate their developmental competence. In parallel, the amount of ROS and TAC were assessed after 0, 24, 48, 72, and 96 h of culture by 2'',7''-dichlorofluorescin assay and ferric reducing/antioxidant power assay, respectively. Results: The respective rates of survival, antrum formation, and metaphase II oocytes were significantly higher in ALA-supplemented groups compared to the groups not treated with ALA. TAC and ROS levels were significantly decreased and increased, respectively during the culture period up to 96 h in the absence of ALA in both vitrified and non-vitrified samples. However, with pretreatment of ALA, TAC levels were increased significantly and remained constant up to 96 h in vitrified-warmed pre-antral follicles, while ROS levels completely returned to the level of starting point after 96 h of culture in the presence of ALA. Conclusion: Pretreatment of ALA positively influences development of pre-antral follicles in vitrified and non-vitrified samples through increasing follicular TAC level and decreasing ROS levels. Key Words: Vitrification, Pre-antral follicle, Alpha lipoic acid (ALA), Reactive oxygen species (ROS), Total antioxidant capacity (TAC) 相似文献