全文获取类型
收费全文 | 223篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
林业 | 25篇 |
农学 | 15篇 |
基础科学 | 2篇 |
48篇 | |
综合类 | 16篇 |
农作物 | 27篇 |
水产渔业 | 35篇 |
畜牧兽医 | 59篇 |
园艺 | 4篇 |
植物保护 | 10篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 22篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 20篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1982年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有241条查询结果,搜索用时 15 毫秒
71.
Zobel R Gereš D Pipal I Buić V Gračner D Tkalcic S 《Reproduction in domestic animals》2011,46(4):595-601
It has been suggested that the time of insemination has effect on the calves' sex ratio because of the differences in timing of capacitation, motility and survival time of the X and Y spermatozoa in the female reproductive tract. We have conducted a field trial to study the effects of different semen deposition sites on the sex ratio and fertility in cattle. Two groups of 450 cows were inseminated via artificial insemination: group A was inseminated into the uterine body and group B was inseminated deep into the uterine horn ipsilateral to the ovary with dominant follicle. After applying several exclusion criteria, a total of 607 pregnant cows were considered for data analysis (group A = 318 and group B = 289 cows). The conception rate was 7% higher (p < 0.05) in the group A, with 23% more of the male calf pregnancies (p < 0.001). At the same time, 18% more of the female calves were calved in the group B (p < 0.005). The difference in male calves between the two groups was 21% and in female calves was 20% (p < 0.001). We conclude that semen deposition site plays a significant role in differences in gender ratio observed after calving. Intracornual semen deposition resulted in a higher ratio of female calves, whereas uterine body deposition site resulted in higher male calves ratio, probably contributing physiologically to the differences in motility, capacitation time, the lifespan of X vs Y spermatozoa and to the pronounced shift of X spermatozoa in the female genital tract. 相似文献
72.
Pham Dinh Dzung Dang Van Phu Bui Duy Du Le Si Ngoc Nguyen Ngoc Duy Hoang Dac Hiet 《Plant Production Science》2017,20(4):389-395
Oligochitosan (OC) is effective biostimulant on growth promotion and elicitation against disease infection for plants. However, the range of OC molecular weight that exhibits the most effective activity is not fully understood and requires further investigation. In this study, OCs with different weight average molecular weight (Mw) were prepared by gamma Co-60 irradiation degradation of chitosan in solution and the effect on growth promotion and enhancement of fruit yield of chili plant (Capsicum frutescens L.) by foliar application of OCs particularly with Mw of 7.8, 5.0, and 2.5 kDa was investigated. Chili plants, cultivated in a greenhouse were sprayed with OC concentration of 50 mg/L for three times. Results indicated that among treatments, OC with 2.5 kDa proved to be the best, which increased the shoot fresh weight by 71.5%, shoot dry weight by 184%, total chlorophyll content by 12%, and fruit fresh weight by 49.8% for the control. Thus, OC with low Mw (2.5 kDa) that can be suitably produced on large scale by gamma Co-60 ray irradiation degradation of chitosan solution is potentially promising to apply as a biostimulant to enhance chili fruit yield significantly. 相似文献
73.
Wen K Li G Zhang W Azevedo MS Saif LJ Liu F Bui T Yousef A Yuan L 《Veterinary immunology and immunopathology》2011,141(3-4):267-275
γδ T cell responses are induced by various viral and bacterial infections. Different γδ T cells contribute to activation and regulation of the inflammatory response and to epithelial repair. How γδ T cells respond to rotavirus infection and how the colonization of probiotics influences the γδ T cell response were unknown. In this study, we evaluated by multicolor flow cytometry the frequencies and distribution of total γδ T cells and three major subsets (CD2-CD8-, CD2+CD8- and CD2+CD8+) in ileum, spleen and blood of gnotobiotic (Gn) pigs at early (3-5 days) and late phases (28 days) after rotavirus infection. The Gn pigs were inoculated with the virulent human rotavirus Wa strain and colonized with a mixture of two strains of probiotics Lactobacillus acidophilus and Lactobacillus reuteri. In na?ve pigs, the highest frequency of total γδ T cells was found in blood, followed by spleen and ileum at the early age (8-10 days old) whereas in older pigs (32 days of age) the highest frequency of total γδ T cells was found in ileum and spleen followed by blood. Rotavirus infection significantly increased frequencies of intestinal total γδ T cells and the putatively regulatory CD2+CD8+ γδ T cell subset and decreased frequencies of the putatively proinflammatory CD8- subsets in ileum, spleen and blood at post-infection days (PID) 3 or 5. The three γδ T cell subsets distributed and responded differently after rotavirus infection and/or lactobacilli colonization. The CD2+CD8+ subset contributed the most to the expansion of total γδ T cells after rotavirus infection in ileum because more than 77% of the total γδ T cells there were CD2+CD8+ cells. There was an additive effect between lactobacilli and rotavirus in inducing total γδ T cell expansion in ileum at PID 5. The overall effect of lactobacilli colonization versus rotavirus infection on frequencies of the CD2+CD8+ γδ T cell subset in ileum was similar; however, rotavirus-infected pigs maintained significantly higher frequencies of CD8- subsets in ileum than lactobacilli-colonized pigs. The dynamic γδ T cell responses suggest that γδ T cell subsets may play important roles in different stages of immune responses after rotavirus infection and probiotic colonization. The knowledge on the kinetics and distribution patterns of γδ T cell subsets in na?ve pigs and after rotavirus infection or lactobacilli colonization provides the foundation for further mechanistic studies of their functions. 相似文献
74.
Abstract. The aim of this study was to investigate the effects of water submergence depth on radial oxygen loss (ROL), soil solution chemistry and rice growth performance in acid sulphate soils in southern Vietnam. ROL was measured in a solution culture. In a separate pot experiment the impact of water submergence depth on rice growth and soil solution chemistry was studied. Three submergence depths were used in the two experiments (5, 10 and 15 cm). ROL declined with submergence depth and was significantly greater in young roots (with no root hairs) than in older roots. In the pot experiment rice growth and soil solution chemistry were clearly affected by the submergence depth. During the first crop at 5 cm submergence, there was a significantly higher yield and a higher oxidation state (pe+pH) compared to 10 or 15 cm submergence. The Fe concentration was significantly greater at the 5 cm depth compared to the 10 or 15 cm depth. SO4 2– reduction was delayed at the 5 cm depth. Rice yield was c. 25% less at the 15 cm than at the 5 cm depth. During a second crop, there was a substantial SO4 2- reduction and H2 S formation and almost no significant effects of submergence depth on either soil solution chemistry or crop yield. In a field experiment with a dry-season rice crop, yield and Fe, Al and SO4 2– concentrations were higher at a shallow submergence depth than at greater depths in the same field, showing similar depth trends to those found during the first crop in the pot experiment. Farmers should be advised to use a shallow submergence depth and, if possible, avoid deep-rooted rice varieties. A conceptual model is suggested, which summarizes the relationships between ROL and soil solution chemistry. 相似文献
75.
The present study deals with the synthesis and subsequent application of Fe3O4@n-SiO2 nanoparticles for the removal of Cr(VI) from aqueous solutions. Rice husk, an agrowaste material, was used as a precursor for the synthesis of nanoparticles of silica. Synthesized nanoparticles were characterized by XRD and SEM to investigate their specific characteristics. Fe3O4@n-SiO2 nanoparticles were used as adsorbent for the removal of Cr(VI) from their aqueous solutions. The effects of various important parameters, such as initial Cr(VI) concentration, adsorbent dose, temperature, and pH, on the removal of Cr(VI) were analyzed and studied. A pH of 2.0 was found to be optimum for the higher removal of Cr(VI) ions. It was observed that removal (%) decreased by increasing initial Cr(VI) concentration from 1.36?×?10-2 to 2.4?×?10-2 M. The process of removal was found to be endothermic, and the removal increased with the rise in temperature from 25 to 45 °C. The kinetic data was better fitted in pseudo-second-order model in comparison to pseudo-first-order model. Langmuir and Freundlich adsorption capacities were determined and found to be 3.78 and 1.89 mg/g, respectively, at optimum conditions. The values of ΔG 0 were found to be negative at all temperatures, which confirm the feasibility of the process, while a positive value of ΔH 0 indicates the endothermic nature of the adsorption process. The present study revealed that Fe3O4@n-SiO2 nanoparticles can be used as an alternate for the costly adsorbents, and the outcome of this study may be helpful in designing treatment plants for treatment of Cr(VI)-rich effluents. 相似文献
76.
Robert Martin Sophouen Im Sophanara Phan Kimsinh Ly Saret Savan Stephanie Montgomery 《Archives of Agronomy and Soil Science》2013,59(6):843-850
A series of experiments was carried out in 2012–2014 in Pailin province, Cambodia, to determine the potential and agronomic requirements for a dry season sunflower crop. The research showed that the six high-oleic sunflower hybrids evaluated were similar for phenological development and yield but two varieties had <50% emergence and poor hybrid seed quality was seen as a constraint to planting under rainfed conditions. Sunflower receiving a basal application of 20:20:15 (N:P2O5:K2O) at 200 kg ha?1 produced achene yield of 2423 kg?1, while side-dressing with urea had no effect on yield. Application of s-metolachlor post-sowing pre-emergence was the most effective weed control treatment and significantly increased sunflower achene yield. Post-emergence weed control was not adequate to prevent yield loss from weed competition. The study showed that sunflower can be grown successfully as a dry season crop in North-West Cambodia when planted no-tillage on residual soil water remaining after maize harvest in October and November. The critical requirements for success are related to preservation and effective use of residual soil water and include minimal soil disturbance, adequate application of fertiliser at sowing, and pre-emergence control of weeds, especially grasses. 相似文献
77.
Effects of salt stress on plant growth characteristics and mineral content in diverse rice genotypes
Thieu Thi Phong Thu Hideshi Yasui Takeo Yamakawa 《Soil Science and Plant Nutrition》2013,59(3):264-273
ABSTRACTWhen rice is grown under moderate salinity (6?dS m?1), yields are reduced by up to 50%. The development of salt-tolerant varieties is a key strategy for increasing yields. We conducted an experiment using a hydroponic system with ion components similar to seawater to determine useful parameters for assessing salt tolerance. Two-week-old seedlings were grown for 7 days on Yoshida hydroponic solution. The treatment group then additionally received an artificial seawater solution (electrical conductivity, 12 dS m?1). After a 2-week period of salt stress, standard evaluation scores (SES) of visual salt injuries were assessed. The K, Na, Mg, and Ca contents were then determined in the roots, sheaths, and leaves of each plant. Following the SES results, we divided the 37 genotypes into four groups: salt-tolerant groups (STGs), moderately salt-tolerant groups, salt-sensitive groups (HSSGs), and highly salt-sensitive groups (HSSGs). In the control, STGs had the highest sheath K content (30.1 mg g?1 dried weight [DW]), whereas HSSGs had the lowest (21.4 mg g?1 DW). Sheath K was also highly and negatively correlated with SES. This suggests that sheath K may be useful for identifying salt-tolerant varieties under non-saline conditions. Plant growth was significantly affected under salt stress, but STGs had the smallest decrease in sheath DW. SES was significantly correlated with sheath and leaf Na, sheath K and Mg, and sheath and leaf Na/K and Na/Mg ratios. The results suggested that sheath K, Na/K, and Na/Mg may be useful indicators for genetic analyses of salt-tolerant varieties under salt-stress conditions. The salt-tolerant cultivars, KCR20, KCR124, and KCR136, are possible candidates for such studies because they had high sheath K content (31.19, 31.21, 29.44 mg g?1 DW, respectively) under non-saline conditions and low SES (3.3, 3.6, 3.9, respectively), and low sheath Na/K (0.64, 0.52, 0.92, respectively) and Na/Mg ratios (2.96, 2.27, 3.03, respectively) under salt-stress conditions. 相似文献
78.
79.
Aye Aye Khaing Kyaw Thu Moe Jung‐Wook Chung Hyung‐Jin Baek Yong‐Jin Park 《Plant Breeding》2013,132(2):165-173
The genus Amaranthus has gained much attention, particularly for its high economic and nutritional value. It is a genus of taxonomic complexity with many interspecific hybrids. For effective conservation and management of the germplasm collected, the development of a core set of accessions is especially important. A core set of 63 accessions was successfully developed from an entire collection of 634 accessions using the powercore 1.0. Among the tested methods for developing the core set – the advanced M strategy using the modified heuristic method (HCC), randomly chosen collections and stratified random collections – HCC was found to be best, with 100% coverage of alleles and minimum redundancy. Allele frequency distribution of the core set developed with HCC was highly correlated with that of entire collections (r = 0.91). Model‐based structure analysis revealed the presence of three subpopulations and 11 admixtures in the selected core set, which is basically consistent with clustering based on the genetic distance. The results from this study will provide effective information for future germplasm conservation and improvement programmes in Amaranthus. 相似文献
80.
Effects of replacing fish meal with soy cake in a diet based on urea-treated rice straw on performance of growing Laisind beef cattle 总被引:1,自引:1,他引:0
Duong Van Nhiem Jan Berg Nils Petter Kjos Nguyen Xuan Trach Bui Quang Tuan 《Tropical animal health and production》2013,45(4):901-909
The present study was to test if different ratios of fish meal to soy cake as protein supplements in the diet are not significantly different in effects on feed intakes and performance of growing beef cattle fed urea-treated rice straw (URTRS) as basal diet under local conditions in North Vietnam. Thirty-six male cattle of Laisind (50 % local Yellow cattle and 50 % Sindhi, both Bos indicus) at around 12 months of age with an average live weight of 124?±?12 kg at start were used in six groups of the experiment. Six diets named A, B, C, D, E, and F used in the experiment were similar in crude protein (CP) level, except for diet A with no supplementation, but different in fish meal/soy cake ratio based on CP content as follows: diet A 0/0, diet B 100/0, diet C 75/25, diet D 50/50, diet E 25/75, and diet F 0/100. Following a 4-week adaptation period, a comparison period lasted 24 weeks. The total intakes of dry matter (DM), DM from roughage, metabolizable energy (ME), and CP were 6, 7, 6, and 20 % higher in diets B–F than diet A with P values ≤0.05, 0.05, 0.05, and 0.001, respectively. The average daily gain (ADG) was 50 % higher (P?<?0.001) in diets B–F than that in diet A. Compared to diet A, diets B–F had lower feed conversion ratio (FCR)DM, FCRME, and FCRCP by 30, 20, and 30 %, respectively (all at P?<?0.001). There were no significant differences between diets B–F in the intakes, FCRs, and ADG. The apparent digestibility of CP was 12 to 24 % higher (P?<?0.001) in diets B–F than that in diet A. There was a tendency that the apparent digestibilities of DM, CP, and CF were increasing with increasing level of soy cake in this study. The ratio of fish meal to soy cake did not significantly affect feed intakes, ADG, FCR, and apparent nutrient digestibilities of the cattle. Soy cake can therefore be used to partially or fully replace fish meal as a protein supplement in the diet of growing beef cattle fed URTRS without any negative effects on animal performance. 相似文献