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   110篇
  免费   23篇
农学   14篇
基础科学   3篇
  5篇
综合类   10篇
农作物   7篇
畜牧兽医   84篇
园艺   2篇
植物保护   8篇
  2022年   1篇
  2021年   2篇
  2020年   7篇
  2019年   5篇
  2018年   4篇
  2017年   6篇
  2016年   7篇
  2015年   6篇
  2014年   7篇
  2013年   8篇
  2012年   1篇
  2011年   2篇
  2010年   6篇
  2009年   6篇
  2008年   5篇
  2007年   10篇
  2006年   2篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  2000年   1篇
  1999年   3篇
  1998年   5篇
  1997年   5篇
  1996年   2篇
  1995年   4篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1988年   4篇
  1987年   1篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1981年   1篇
  1980年   2篇
  1978年   1篇
  1976年   1篇
  1974年   1篇
  1972年   1篇
排序方式: 共有133条查询结果,搜索用时 46 毫秒
1.
Manipulated Mouse Embryos as Bioassay System for Water Quality Control   总被引:1,自引:0,他引:1  
Mouse pronuclear stage embryos with intact slit zona pellucida (manipulated) were cultured in vitro until the hatched blastocyst stage in simplex optimized medium with higher K+ concentration (KSOM) prepared with three different water types: tap, deionized reverse osmosis (D‐O) water and Milli‐Q system (M‐Q) water. The culture media were supplemented with or without protein and ethylenediaminetetraacetic acid (EDTA, disodium salt). The rates of hatched blastocysts were significantly affected (p < 0.01) by micromanipulation, protein supplement and water source. The water source has no influence (p > 0.05) on development in EDTA‐supplemented protein‐free culture media, whereas in EDTA‐ and protein‐free culture media, the water quality significantly (p < 0.001) affected the rates of development, with higher rates in media prepared with M‐Q water. The micromanipulated embryos showed higher sensitivity to the water quality (p < 0.01). It worth mentioning that the rates of hatched blastocysts in protein‐free culture media were very low (0–7.5%). Furthermore, the three different water types were analysed by measuring the electrical conductivity, inorganic ions, total organic carbon and endotoxins to evaluate the purity. M‐Q water showed the lowest levels of inorganic ion, total organic carbon and endotoxin concentrations. We concluded that manipulated mouse embryos are good system to evaluate the quality of water used in biological system.  相似文献   
2.
To assess the effect of the angiotensin‐converting enzyme (ACE) inhibition on the efficiency of the fixed‐time artificial insemination (TAI), 69 goats were divided randomly into two groups: enalapril (n = 35) and control (n = 34). In the experiment, all animals underwent the protocol of fixed‐time artificial insemination for 12 days. Enalapril group received enalapril maleate dissolved in saline (Enalapril, Lab Teuto Ltda) subcutaneously at the following doses: 0.2 mg/kg/day in D0‐D2; 0.3 mg/kg/day in D3‐D6 and 0.4 mg/kg/day in D7‐D11. The control group received the corresponding volume of 0.9% saline solution. We performed a single insemination 36 hr after sponge removal using frozen semen from two adult male goats with recognized fertility. The ultrasound pregnancy diagnosis was 30 days after the artificial insemination (AI). There was significant increase in pregnancy rates and twinning as well as a decrease in foetal loss in animals receiving enalapril (p < .01). The use of ACE inhibitors during the TAI protocol was shown to be a promising alternative to increase the efficiency of such reproductive biotechnology.  相似文献   
3.
Summary Standard local practice in Northern India is to continue irrigation of winter wheat crop almost up to harvest, based on the farmer's belief that this treatment increases grain weight and yield. The effect of an early cut-off of irrigation on the water use was studied in a three-year experiment on a deep, sandy-loam soil.Wheat, sown during the second or third week of November, received its first irrigation four weeks later. Subsequently treatments included irrigations of 7.5 cm water depth applied after 10 cm of cumulative pan evaporation minus rainfall had elapsed since the previous irrigation up till mid-April; irrigations of 7.5 cm up till mid-February and thereafter irrigation equal to 75 and 100% soil-water deficit in the 0–180 cm profile around March 10 with no later irrigation; and a similar treatment with one additional irrigation after making up the water deficit.Least irrigation water was used from the treatment in which 75% water deficit was restored around March 10 and no further irrigation was applied. This treatment increased the average extraction of profile water by 4 cm compared to treatments in which irrigation was continued until mid-April. Profile water depletion was inversely related to the amount of irrigation. Grain weight and yields from the various treatments harvested in the last week of April were unaffected by the treatments.The authors are grateful to the ICAR for financing this research  相似文献   
4.
Irrigation water is a limited resource, and therefore irrigation practices must be rationalized for high water-use efficiency. Little is known about the influence of stored water in deep soils on the water needs and the post-sowing irrigation requirements of crops. A 3-year field experiment was conducted to determine the effects of combinations of light and heavy pre-sowing irrigations with two post-sowing irrigation regimes on yield, root growth, water use and water-use efficiency of wheat on a deep alluvial sandy loam soil. Post-sowing treatments consisted of (i) five 75-mm irrigations at five growth stages, and (ii) irrigations based on pan evaporation, i.e. at IW/PAN-E ratio of 0.75 (75 mm of irrigation water were provided as soon as the open-pan evaporation minus rainfall since previous irrigation was 100 mm).The latter regime required 175 mm less water than that with irrigation at growth stages. Profile water utilization was inversely related to post-sowing irrigation water. Where pre-sowing irrigation was light, post-sowing irrigations based on pan evaporation yielded significantly less than those based on growth stages. With heavy pre-sowing irrigation, irrigation based on the pan evaporation yielded as much as five irrigations at growth stages. The former decreased the mean water application by 153 mm and increased the water-use efficiency by 26%. Irrigation based on pan evaporation stimulated greater utilization of stored water by increasing the rooting density in deeper layers.It is indicated that for higher water-use efficiency and yield, wheat should be sown after a heavy pre-sowing irrigation, and post-sowing irrigation should be based on 0.75 pan evaporation.  相似文献   
5.
The aim of this study was to evaluate the reproductive performance of three parities of gilts treated or not treated with gonadotropin to induce puberty. Sixty gilts received 600 IU of equine chorionic gonadotropin (eCG) followed by 2.5 mg of porcine luteinizing hormone (LH) 72 h later. Fifty‐nine other gilts were exposed only to a mature boar for 15 min twice daily. Artificial insemination (AI) was performed at 0, 12 and 24 h after the detection of oestrus, and gestation was confirmed by ultrasound after 35 days. Sows were inseminated at the first post‐weaning oestrus. The total numbers of piglets born, piglets born alive, stillborn, mummified foetuses, as well as pregnancy and farrowing rates were evaluated for each of the three parities. Culling rates, farrowing intervals and weaning‐to‐oestrous intervals (WEI) were also analysed. Mean age at puberty and oestrous manifestation were not significantly different between treatments (p = 0.0639; 179.20 ± 17.52 compared with 173.96 ± 16.94, 91.66% compared with 94.92%) across the experimental period. However, females that underwent puberty induction showed modest increases both in the number of total pigs born and in the number of piglets born alive. In conclusion, puberty induction through exogenous gonadotropin administration in field conditions did not induce a more concentrated first oestrous manifestation, but trended to a modest increase in the number of pigs born alive in the first parity and a reduced culling rate during the first gestation.  相似文献   
6.
A combination Escherichia coli serotype O78 and Pasteurella anatipestifer bacterin was developed and tested in white pekin ducks in laboratory and field trials. Inoculations with bacterin at 2 and 3 weeks of age provided significant protection against challenge with virulent E. coli O78 and Pasteurella anatipestifer serotypes 1, 2, and 5. No significant cross-protection was observed against heterologous E. coli serotypes, although there was a slight reduction in mortality in ducklings challenged with E. coli serotypes O2a and O119. In field trials, the E. coli-P. anatipestifer bacterin produced significant reduction of mortality in commercial white pekin ducks compared with P. anatipestifer bacterin.  相似文献   
7.
Summary A macro-mutant, E 100Y(M) in chickpea (Cicer arietinum L.) was found to affect several plant and seed characters. For plant type monogenic inheritance was observed. A single pair of recessive genes pt/pt was ascribed to this mutant. The mutant locus seemed to be exerting pleiotropic action. The utilization of this mutant for chickpea improvement has been discussed.  相似文献   
8.
Seventeen diverse clones of sugarcane (Saccharum spp.) (7 early, 6 mid season and 4 late) were planted in October 1991 and 1992 in flooded (FE) and non flooded (NFE) environments for evaluation of cane yield, commercial cane sugar (CCS), internode length, internode number, stalk length, stalk thickness (circumference), stalk number, sugar recovery, and stalk weight. Cane yield showed significant positive phenotypic correlation coefficient (PCC) with stalk number in FE (P ≤ 0.05) and NFE (P ≤ 0.01). Stalk length had a significant positive PCC with stalk weight in both environments, and with internode length in FE (P ≤ 0.05). Commercial cane sugar also expressed significant positive PCC with cane yield in both environments (P ≤ 0.01), but with stalk number only in NFE (P ≤ 0.05). Genotypic correlation coefficients were generally in the same direction as PCC but higher in magnitude. In both environments, stalk number and stalk weight had relatively high positive direct effects on cane yield. However, flooding tended to enhance the direct effect of stalk weight and diminish the direct effect of stalk number on cane yield. Only cane yield and sugar recovery had high direct effects on CCS. Selection for improvement of cane yield can be based on stalk number and stalk weight in both environments. High yielding clones can be further screened for more sugar recovery to improve CCS. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
9.
Identification of a small core germplasm set representing the available genetic diversity is essential for its proper evaluation and subsequent utilization in rice improvement programmes. For constituting a small diverse mini‐core panel of Indian rice germplasm, a representative set of 6912 accessions drawn based on their geographic origin from the whole rice germplasm collection available in the National Gene Bank was genotyped using 36 microsatellite markers. Automated fragment analysis of amplicons yielded a total of 435 alleles, with an average 12.4 and range of 3–29 alleles per locus. Polymorphism information content (PIC) ranged from 0.08 (RGNMS190) to 0.86 (RM552) with an average of 0.528. Based on genotyping data, a mini‐core consisting of 98 genotypes was identified. Ninety‐four per cent of the alleles present in the core set were present in the mini‐core. The identified small but diverse panel will be useful for further intensive trait‐specific evaluation and utilization in allele mining.  相似文献   
10.
A macroscopic plate test was found to be reliable and convenient for detection of Leptospira serotype pomona antibodies in bovine sera. However, the procedure was unreliable for detecting L. serotype canicola antibodies because of false positive reactions. An indirect immunofluorescence test and the microscopic agglutination test provided comparable results and they effectively detected serotype pomona antibodies in bovine sera.  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