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   115篇
  免费   7篇
林业   14篇
农学   4篇
基础科学   4篇
  20篇
综合类   3篇
农作物   21篇
水产渔业   21篇
畜牧兽医   22篇
园艺   1篇
植物保护   12篇
  2022年   7篇
  2021年   7篇
  2020年   9篇
  2019年   6篇
  2018年   7篇
  2017年   10篇
  2016年   6篇
  2015年   9篇
  2014年   9篇
  2013年   7篇
  2012年   7篇
  2011年   7篇
  2010年   5篇
  2009年   2篇
  2008年   4篇
  2007年   1篇
  2006年   1篇
  2005年   4篇
  2004年   2篇
  2003年   3篇
  2002年   5篇
  2001年   1篇
  1995年   1篇
  1977年   1篇
  1973年   1篇
排序方式: 共有122条查询结果,搜索用时 15 毫秒
31.

The objective of this study was to evaluate the fertility of sexed semen compared with conventional semen with regard to the puberty and breeding ages of Holstein dairy heifers subjected to double Ovsynch protocol with fixed time of artificial insemination. A total of 468 Holstein heifers were divided into two groups. The first group was 122 dairy heifers inseminated via conventional semen, while the second group was 346 heifers inseminated with sexed semen. The puberty and breeding ages of heifers were determined from the farm records. Estrus was synchronized using the double Ovsynch protocol. Numbers were estimated for pregnancy at 40 and 60 days post insemination, embryonic loss, and abortion. The results revealed that the heifers inseminated with sexed semen had a significantly lower first-service pregnancy rate (51.45%) than those inseminated with conventional semen (61.47%). Heifers achieving puberty before 350 days old had a higher pregnancy rate. Embryonic losses and abortion rates did not differ between the two types of semen. Holstein heifers subjected to Ovsynch protocol with sexed semen had an acceptable first-insemination pregnancy rate. Even the applications of sexed semen reduce the reproductive fertility and pregnancy rate in Holstein heifers.

  相似文献   
32.
European Journal of Forest Research - Pterocarya fraxinifolia, native to the southern Caucasus and adjacent areas, has been widely introduced in Europe. In this study, we investigate the following:...  相似文献   
33.
ABSTRACT

Background: Traditional field-based methods of measurement of biomass and carbon storage face difficulty in collecting time-consuming and expensive, suggests the use of remote sensing-based techniques. It estimates the economic value of the aboveground biomass (AGB) using satellite remote sensing across the Hyrcanian forests of Iran. Methods: The Landsat-8 OLI sensor data were combined with field-based allometric information of 186 circular sample plots. The AGB was calculated at the plot level using the collected data and specific volumetric mass for species in the studied area. It was followed by calculating the carbon storage using a 50% carbon coefficient and the photosynthesis equation at the forest parcel level. Model results using the random forest and support vector machines. The carbon sequestration value was calculated with USD 25.3 as a shadow value of carbon in 2014 and using the replacement cost approach. Results: The highest performances achieved by RF for biomass, carbon storage and the carbon storage value (Iranian Rials of 0.67% and 16%, respectively). The value was derived once at the plot level of 12.22 million IRR (370.43 USD) per ha. In addition, at the parcel level, which resulted in an estimated value of 12.87 million IRR (390.24 USD) per ha.  相似文献   
34.
Paddy and Water Environment - One of the common irrigation systems in the paddy fields is field-to-field irrigation. The management of these irrigation systems is difficult and essential because of...  相似文献   
35.
This study was conducted to evaluate the protein quality of four types ofedible mushrooms common in Jordan in terms of protein digestibility –corrected amino acid score (PDCAAS), which is a combination of thechemical score of the limiting amino acid multiplied by true digestibility ofthe protein. True protein digestibility values were low (61.4, 73.4, 52.6and 80.5 for Terfezia claveryi, Pleurotus ostreatus, Tricholoma terrum and Agaricus macrosporus, respectively). Based onthe essential amino acids pattern requirements for children, the limitingamino acids in P. ostreatus and A. macrosporus protein weresulphur-containing amino acids with chemical scores of 0.61 and 0.50,respectively. However, lysine was the limiting amino acid in the protein ofT. claveryi and T. terreum with chemical scores of 0.71 and 0.67,respectively, and the PDCAAS was 0.43, 0.45, 0.35 and 0.40 for themushrooms types, respectively. Considering the pattern of essential amino acid requirements of laboratory rats, thesulphur containing amino acids were the limiting amino acids in the proteinof T. claveryi, P. ostreatus, T. terreum and A.macrosporus with chemical scores of 0.56, 0.30, 0.34 and 0.25,respectively. The PDCAAS were 0.34, 0.22, 0.17 and 0.20,respectively. It is concluded that the four mushroom types studied are of lowprotein quality.  相似文献   
36.
Journal of Plant Diseases and Protection - Methylated soy and chickpea proteins (MSP and MCP, respectively), and 11S globulin (a soy protein fraction), are characterized by net positive charges and...  相似文献   
37.
Stewing of rice grains by steam after boiling in excess water can be used for cooking rice perfectly. The effects of this procedure in cooking of three varieties of Iranian rice (Sang Tarom, Domsiyah and Fajr) on textural and morphological properties of cooked rice grains were investigated. The results showed that this step in rice cooking reduced the hardness and increased the adhesiveness of rice grains significantly. By the use of the scanning electron microscopy, it was shown that the outer surface of cooked rice stewed by steam had less porosity and closer pores due to the modification during cooking, and better gelatinization and more expansion of starch granules compared to non-stewed samples. The use of this procedure in rice cooking to provide a fully cooked and gelatinized, softer and stickier final product is recommended.  相似文献   
38.
39.
Interaction between soil pedogenesis, subsurface water dynamics, climate, vegetation and human ingenuity in a desert environment has been found to result in a unique ecohydrological system with an essentially three dimensional sedimentation structure in the bed of a recharge dam in Oman. A 3-D array of silt blocks sandwiched by dry sand-filled horizontal and vertical fractures was studied in pot experiments as a model of a natural prototype. Pots are filled with a homogenous sand-silt mixture(control) or artificially structured(smart design, SD) soil substrates. Rhodes grass and ivy(Ipomea, Convolvulaceae) were grown in the pots during the hottest season in Oman. Soil moisture content(SMC) was measured at different depths over a period of 20 days without irrigation. SD preserved the SMC of the root zone for both ivy and grass(SMC of around 25%–30% compared to 10% for control, 3 days after the last irrigation). Even after 20 days, SMC was around 18% in the SD and 7% in the control. This, similar to the case of a natural prototype, is attributed to the higher upward capillary movement of water in control pots and intensive evaporation. The capillary barrier of sand sheaths causes discontinuity in moisture migration from the micro-pores in the silt blocks to sand pores. The blocks serve as capillarity-locked water buffers, which are depleted at a slow rate by transpiration rather than evaporation from the soil surface. This creates a unique ecosystem with a dramatic difference in vegetation between SD-pots and control pots. Consequently, the Noy-Meir edaphic factor, conceptualizing the ecological impact of 1-D vertical heterogeneity of desert soils, should be generalized to incorporate 3-D soil heterogeneity patterns. This agro-engineering control of the soil substrate and soil moisture distribution and dynamics(SMDaD) can be widely used by desert farmers as a cheap technique, with significant savings of irrigation water.  相似文献   
40.
Channel catfish were fed practical corn‐soybean meal diets for 10 weeks that contained various weighed amounts of ground, dried field corn contaminated with 20 mg deoxynivalenol (DON) kg−1. Weighed amounts of DON corn were blended with weighed amounts of ground, clean corn that contained no DON (0 mg kg−1) to yield five diets that had 0, 2.5, 5.0, 7.5 and 10.0 mg DON kg−1 of diet. Results show that catfish fed diets that contained DON for 7 weeks did not experience lower weight gains or poorer feed conversion ratios that were significantly (P > 0.05) different from control‐fed fish. Mortality of catfish during the 21‐day post‐challenge period indicate that catfish fed diets containing DON‐contaminated corn that provided at least 5.0 mg DON kg−1 of diet had significantly (P < 0.05) lower mortality than catfish fed the control diet or the diet that provided 2.5 mg DON kg−1 of diet. The presence of DON‐contaminated corn in the experimental diets did not significantly (P > 0.05) alter fish body weight gains and appeared to provide a protective effect for channel catfish challenged with the pathogenic bacterium Edwardsiella ictaluri.  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