首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   105篇
  免费   9篇
林业   8篇
农学   9篇
基础科学   3篇
  34篇
综合类   4篇
农作物   4篇
水产渔业   2篇
畜牧兽医   36篇
园艺   1篇
植物保护   13篇
  2023年   4篇
  2022年   3篇
  2021年   2篇
  2020年   4篇
  2019年   5篇
  2018年   3篇
  2017年   5篇
  2016年   5篇
  2015年   1篇
  2014年   6篇
  2013年   14篇
  2012年   5篇
  2011年   8篇
  2010年   5篇
  2009年   2篇
  2008年   6篇
  2007年   2篇
  2006年   6篇
  2005年   1篇
  2004年   1篇
  2003年   4篇
  2002年   2篇
  2001年   3篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1995年   1篇
  1993年   1篇
  1992年   1篇
  1991年   3篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1969年   1篇
排序方式: 共有114条查询结果,搜索用时 15 毫秒
61.
Studies on parthenogenetic activation of oocytes are important to improve the efficiency of nuclear transfer as artificial activation of oocytes is an essential component of nuclear transfer protocol. The present study was carried out to investigate the effects of different activation methods, culture systems and culture media on in vitro development of zona-free and with-zona parthenogenetic embryos in goat. In case of zona-free parthenogenesis, there was a significant (p < 0.05) increase in cleavage rate and blastocyst yield when oocytes were activated by electrical pulse (76.29 ± 0.52% and 19.07 ± 0.39% respectively) than when Ca-ionophore was used for activation (63.45 ± 0.73% and 14.09 ± 0.65% respectively). The quality of blastocysts was evaluated by determination of cell number and by expression profile of pluripotent related gene Oct-4. No significant (p < 0.05) difference was found in quality of blastocysts produced by different activation methods. In culturing of zona-free parthenogenetic embryos, flat surface (FS) was proved to be the best system. A significant (p < 0.05) decrease in cleavage rate and blastocyst yield was found in Microdrop culture of zona-free embryos (43.67 ± 2.08% and 0.72 ± 0.72% respectively) in comparison to WOW of zona-free embryos (73.88 ± 1.70% and 15.51 ± 1.34% respectively) and FS of zona-free (75.14 ± 0.81% and 23.93 ± 2.71% respectively) as well as with-zona (72.16 ± 1.55% and 18.16 ± 0.68%) embryos. Zona-free flat culture system yielded significantly (p < 0.05) higher blastocyst rate than zona-free WOW system as well as with-zona flat culture system. The zona-free and with-zona parthenogenetic embryos were cultured in three different media — Research Vitro Cleave media from Cook® Australia (RVCL), Embryo Development Medium (EDM) and Modified Synthetic Oviductal Fluid (mSOF). In case of zona-free parthenogenesis, significant (p < 0.05) increase was found in blastocyst development rate in RVCL medium (18.61 ± 1.52%) than EDM (11.29 ± 0.77%) or mSOF (11.53 ± 1.86%). In case of with-zona parthenogenesis, RVCL medium and EDM were found superior to mSOF. The results of the study will be helpful to improve the efficiency of nuclear transfer in goat.  相似文献   
62.
A series of five azo acid dyes were synthesized using different diazotized aromatic amine sulfonic and carboxylic acids followed by coupling with 2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione. The dyes were characterized by 1H-NMR, 13CNMR, FTIR, and elemental analysis. They were applied on nylon, silk, and wool. Their fastness properties were evaluated and color on the fabric was assessed. Yellow, brown, and crimson dyeings with good fastness properties were obtained. The dyes are water soluble and showed absorption from 380 nm to 550 nm. Acid dyes from diazo component 4- aminonaphthalene-1-sulfonic acid (naphthionic acid) and 4-amino-5-hydroxynaphthalene-2,7-disulfonic acid (H-Acid) were found to be more red shifted as compared to the other dyes. More red shifted absorption maximum was observed in acidic pH than in alkaline pH. The trends in vertical excitations obtained from Time Dependent Density Functional Theory calculations are in good agreement with the experimental absorptions.  相似文献   
63.
Hyperaccumulating plants are increasingly investigated in combination with EDTA addition to soil for phytoremediation of heavy metal contaminated soils. A 60-day incubation experiment was carried out to investigate the effects of heavy metal release during the decomposition of Zn-rich (15.7 mg g?1 dry weight) Arabidopsis halleri litter on C mineralization, microbial biomass C, biomass N, ATP, and adenylate energy charge (AEC). These effects were investigated in two soils with different Zn, Cu, and Pb levels, with and without EDTA addition to soil. The sole addition of Zn-rich A. halleri litter to the two soils did not increase the contents of NH4NO3 extractable Zn, only with the combined additions of EDTA and litter was there a considerable increase, being equivalent to three times the added amount in the low metal soil and to 50% in the high metal soil. Litter amendment increased the CO2 evolved; being equivalent to 44% of the added C in the two soils, but EDTA addition had no significant effect on CO2 evolution. Litter amendment resulted also in an 18% increase in microbial biomass C, 27% increase in ATP and 6% increase in AEC in the two soils, but EDTA had again no effect on these indices at both metal levels. In contrast, the sole addition of litter had no effect on microbial biomass N, but EDTA addition increased microbial biomass N on average by 49%. The application of EDTA for chelate-assisted phytoextraction should in the future consider the risk of groundwater pollution, which is intensified by resistance of EDTA to microbial decomposition.  相似文献   
64.
A study at selected action sites in semi-arid region of Andhra Pradesh, India, showed widespread land degradation due to low levels of soil organic carbon (78% of fields) and deficiencies of available nutrients like phosphorus (34%), sulfur (93%), calcium (33%), zinc (84%), boron (73%), and copper (33%). Soil test-based addition of deficient micro- and macronutrients increased food grain production by 30–40% and straw (which is used as fodder) production by 10–30%. Micro-watershed scale low-cost cement-lined farm-ponds at smallholder farm level proved a scalable technology for drought-proofing of crops resulting into additional crop yield by more than 30% during 2015. Augmentation of water sources also facilitated farmers’ to successfully diversify the production system. Shared machinery resources improved the operational and economic efficiency of farm sowing operations through higher crop yields by around 10%. We conclude that a mix of low-cost critical interventions if out-scaled in a large number of dryland small holdings through policy support may not only improve productivity and livelihoods, but also enhance their abilities to effectively cope with the climatic aberrations.  相似文献   
65.
66.
67.
Investigations were carried out to determine the nutritional profile of Indian Ocean swimming crab Charybdis smithii, which is emerging as an unconventional resource in trawl discards of India. The average protein content was 9.38 g/100 g, fat 0.86 g/100 g, ash 0.34 g/100 g, fiber 0.13 g/100 g, and carbohydrate 1.8 g/100 g. One-way analysis of variance showed no significant variations of constituents except in dry matter and carbohydrate between sexes. Macronutrients, Na (317.1, 327.6/100 g), K (148, 177.40 mg/100 g), Ca (187.90, 285.80 mg/100 g), and Mg (34.31, 41.49 mg/100 g), showed significant variation between sexes. The composition of micronutrients in male and female were Cu (0.28, 0.15 mg/100 g), Fe (0.57, 0.71 mg/100 g), and Zn (1.71, 2.75 mg/100 g). Mineral content showed significant difference between sexes. Amino acid analysis showed that 12.04 and 11.47 g/100 g essential amino acid glycine was present in male and female, respectively, and lysine concentration was 13.96 and 12.65 g/100 g, respectively. The nutritional profile of the species was determined the first time and shows that it is comparable with any other edible crabs and could be exploited as a commercial resource to supplement nutritional demand.  相似文献   
68.
In this paper, we report the development, characterization and bioefficacy evaluation of fipronil nanoformulations against brown plant hopper (BPH); Nilaparvata lugens in rice. Nanoformulations were characterized for nanosizing and stability under variable conditions. Bioefficacy of nanoformulations were evaluated under field condition at farms of Indian Agricultural Research Institute, New Delhi during Kharif 2015. At milking stage BPH populations were above economic threshold level; followed by foliar application of fipronil nanoformulations at four doses (viz., 30, 45, 60 and 90 g a.i./ha) along with commercial formulation of fipronil. The mean mortality clearly indicated that all the insecticidal treatments were significantly superior over untreated control where, highest mortalities were observed in nanodispersions followed by monolithic dispersion and commercial formulation of fipronil. Treated plots 7 days after application @ 60 g a.i./ha has shown 93.47%, 86.89% and 80.47% reduction BPH population in nanodispersion, encapsulated monolithic dispersion and commercial formulation treated plots respectively. In comparison to commercial formulation @ 60 g a.i./ha yield has increased by 0.56 t ha?1 (28.76%) and 0.26 t ha?1 (14.04%) in nanodispersion and monolithic dispersion.  相似文献   
69.
A long-term field experiment with rice-wheat cropping was started in the wet season of 1988 with four levels of lantana (Lantana camara L.) (0, 10, 20, and 30 Mg ha?1 on fresh weight basis) and three tillage practices (No puddling, puddling, and soil compaction). From wet season of 1997, however, three tillage practices were replaced with three levels of nitrogen (N) and potassium (K) to rice (33, 66, and 100% of recommended) and 66% of recommended N, phosphorus (P), and K to wheat. Phosphorus was totally omitted for the rice crop. The recommended N and K for rice was 90 and 40 kg ha?1, whereas the recommendations for N, P, and K for wheat were 120, 90 and 30 kg ha?1. Organic amendments are known to improve soil productivity under rice-wheat cropping by improving physical conditions and nutrient status of the soil, but their availability is restricted. There is a need to identify locally available and cost-effective organic materials that have minimal alternate uses as fodder and fuel. We evaluated Lantana camara L. residues, a fast-growing weed in nearby wastelands, as a potential soil organic amendment. Among the different fractions of K, nonexchangeable K was dominant followed by exchangeable and water soluble K. The incorporation of lantana (10 to 30 Mg ha?1) over the last 12 years has resulted in a significant build-up of all the K fractions, the maximum being in water-soluble K (10 to 32%) followed by exchangeable K (18 to 27%) and least in nonexchangeable K (5 to 7%) over no lantana incorporation. The increasing levels of these two inputs significantly and consistently increased ammonium acetate (NH4OAc)- extracted K (available K) content in soil and also resulted in significantly higher accumulation of K by the crops during the years of experimentation. Among different K fractions, exchangeable K was observed to be the most important K fraction contributing towards wheat and rice yields as well as K accumulation by wheat and rice. Stepwise multiple regression equations indicated that exchangeable K was the most important variable contributing towards total variation in grain yield and K accumulation by wheat or rice.  相似文献   
70.
In view of widespread deficiencies, a long-term experiment was started at the International Crops Research Institute for the Semi-Arid Tropics, Patancheru, India in 2007 to identify economically efficient application strategy (full or 50% dose every or every second year) of sulphur (S) (30 kg ha?1), boron (B) (0.5 kg ha?1) and zinc (Zn) (10 kg ha?1). During the fourth year in 2010, balanced fertilization through adding S, B and Zn increased maize grain yield by 13–52% and soybean yield by 16–28% compared to nitrogen (N) and phosphorus (P) fertilization alone. Balanced nutrition increased N and P uptake, utilization and use efficiency for grain yield and harvest index indicating improved grain nutritional quality. The N, P plus 50% of S, B and Zn application every year recorded highest crop yields and N and P efficiencies indices and increased rainwater use efficiency with a benefit:cost ratio of 11.9 for maize and 4.14 for soybean. This study showed the importance of a deficient secondary nutrient S and micronutrients B, Zn in improving N and P use efficiency while enhancing economic food production.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号