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   259篇
  免费   14篇
林业   34篇
农学   19篇
基础科学   3篇
  34篇
综合类   15篇
农作物   18篇
水产渔业   33篇
畜牧兽医   92篇
园艺   2篇
植物保护   23篇
  2022年   13篇
  2021年   14篇
  2020年   11篇
  2019年   12篇
  2018年   10篇
  2017年   9篇
  2016年   8篇
  2015年   9篇
  2014年   9篇
  2013年   20篇
  2012年   22篇
  2011年   17篇
  2010年   4篇
  2009年   11篇
  2008年   16篇
  2007年   17篇
  2006年   12篇
  2005年   8篇
  2004年   7篇
  2003年   5篇
  2002年   3篇
  2001年   4篇
  2000年   2篇
  1999年   6篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1992年   1篇
  1989年   1篇
  1986年   1篇
  1982年   1篇
  1980年   2篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   3篇
  1973年   1篇
  1970年   1篇
  1969年   1篇
  1967年   1篇
  1947年   2篇
排序方式: 共有273条查询结果,搜索用时 169 毫秒
131.
Gesunde Pflanzen - The effect of weed control in chickpea crop was assessed during 2011–12 and 2012-–13 in two-year experimentation at Ahmad Wala Research Station district Karak,...  相似文献   
132.
133.
Brassica rapa (chinese cabbage) is one of the main vegetable crops grown in Asian countries. Pectobacterium carotovorum subsp. carotovorum causes severe economic loss in this crop as well as in other Brassica crops through soft rot disease. Cysteine proteases like bromelain, papain or ficin show toxic effects to herbivorous insects and pathogenic bacteria. They have been known to be critical factors in plant defence mechanisms. The current study investigated the effect of bromelain gene (BL1) of pineapple (Ananas comosus L. Merrill) on enhancing resistance to soft rot in transgenic Brassica rapa ‘Seoulbaechu’. Three homozygous T2 lines were inoculated with Pectobacterium carotovorum subsp. carotovorum and BL8-2 line showed the lowest rate of infected leaves (RIL) in both wound inoculation and non-wound inoculation, when the non-infected line showed 100 % RIL in both cases. The highest expression of BL1 gene was also observed in BL8-2 homozygous line. Thus, the over-expressed BL1 gene conferred enhanced resistance to soft rot in Brassica rapa.  相似文献   
134.
The aims of the present study were to clarify the effect of kisspeptin10 (Kp10) on the secretion of growth hormone (GH) from bovine anterior pituitary (AP) cells, and evaluate the ability of sex steroid hormones to enhance the sensitivity of somatotrophic cells to Kp10. AP cells prepared from 8–11‐month‐old castrated calves were incubated for 12 h with estradiol (E2, 10?8 mol/L),progesterone (P4, 10?8 mol/L), testosterone (T, 10?8 mol/L), or vehicle only (control), and then for 2 h with Kp10. The amount of GH released in the medium was measured by a time‐resolved fluoroimmunoassay. Kp10 (10?6 or 10?5 mol/L) significantly stimulated the secretion of GH from the AP cells regardless of steroid treatments (P < 0.05), and E2, P4, and T had no effect on this response. The GH‐releasing response to growth hormone‐releasing hormone (GHRH, 10?8 mol/L) was significantly greater than that to Kp10 (P < 0.05). The present results suggest that Kp10 directly stimulates the release of GH from somatotrophic cells and sex steroid hormones do not enhance the sensitivity of these cells to Kp10. Furthermore, they suggest that the GH‐releasing effect of Kp10 is less potent than that of GHRH.  相似文献   
135.
The ripening of Jonagored Jonagold apple fruit (Malus x domestica Borkh.) during development was manipulated with preharvest applications of ReTain or a combination of ReTain plus Ethrel. The fruits, harvested preclimacteric at approximately the same stages of maturity, were stored in refrigerated air (RA) for 45 days or in controlled atmosphere (CA) for 180 days at 0 degrees C. Volatile evolution, ethylene production, and respiration of stored fruit were studied during poststorage holding at 22 degrees C. ReTain reduced volatile production by 19%, but application of Ethrel to ReTain-treated fruit increased production to control levels. The inhibition of volatile production by ReTain appears to be independent of respiration but may be related to the ethylene-producing capacity of the fruit. Although ReTain reduced flavor-related volatile esters, it did not affect levels of the compound responsible for the typical spicy flavor in Jonagored Jonagold fruit, 4-methoxy-2-propenylbenzene. The CA-stored fruit had a much reduced production of volatile compounds compared to RA-stored fruit, with more discernible effects in ReTain-treated fruit. Ethrel application to ReTain-treated fruit improved the volatile production intermediate between the ReTain alone and control in CA-stored fruit. The data collectively suggest that ReTain may have some promise for better scheduling of harvest of apples with no appreciable loss in RA-stored fruit quality. Reduction in production of alpha-farnesene by ReTain may also reduce the potential for scald development in CA-stored fruit.  相似文献   
136.
An accurate timing of parturition is very useful for managing canine parturition. It is generally accepted that parturition in bitches occurs between 64 and 66 days after the luteinizing hormone peak. In this retrospective study, we determined pregnancy length in different breeds and its influencing factors dating it from the estimated day of ovulation (EDO), defined as the day when peripheral plasma level of progesterone (P4) reaches 6 ng/ml. From January 2001 to December 2006, 162 pregnancies in 151 bitches of 53 different breeds were followed. Different parameters concerning the bitch, the litter, the type of semen and the type of reproduction were studied. The mean estimated pregnancy length in the bitch from EDO to parturition was 63.1±2.1 days. The main influencing factors for the pregnancies studied were the breed, the size of the bitch and the number of puppies within the litter.  相似文献   
137.
Conservational tillage (CT) in combination with broad spectrum herbicide may be more efficient and economical in controlling weeds,reducing cost of cultivation,and enhancing wheat yield.Field experimen...  相似文献   
138.
The objective of the study was to evaluate a pinhole castration technique in male ponies. Adult ponies (n = 12) were randomly allotted to one of the two equal groups. Both of the groups were anaesthetised with xylazine–ketamine–diazepam and had single (SLS, SLC) ligation of the spermatic cord on one side and double (DLS, DLC) ligation on the other side using silk (Group T1) and catgut (Group T2). Single ligation whether using silk or catgut (SLS and SLC) was completed in 3.50 ± 0.34 min. DLS took 6.66 ± 0.49 min and DLC 7.16 ± 0.47 min. Scrotal oedema was noticed in all of the ponies from Day 1 to Day 15. The scrotal circumference and testicular volume in animals of both of the groups showed a significant (P<0.05) increase from Day 1 to Day 4. Orchiectomy to recover testicular remnants was performed in all of the animals on Day 41. Straw-coloured fluid accumulation was noticed in seven testicular remnants (4 T1 and 3 T2). One testicle from Group DLS showed suppuration. Multiple gross and histological abnormalities were detected in all double ligated testes. The changes were more severe in the DLS than the DLC group and their epididymis (n = 3) also showed necrosis, fibroplasia and an obstructed lumen. Severe adhesions had developed in three and one testicle only from the SLS and SLC groups respectively. The remaining testes and epididymis in both of these groups showed only mild-to-moderate adhesions. From this study, it was concluded that castration may not be achieved by percutaneous single ligation of the spermatic cord in ponies. Although double ligation induces marked gross and histopathological changes, assessments of the testosterone levels and sperm analysis are required before recommending this procedure. Use of silk for ligation of the spermatic cord is advantageous over catgut but maintenance of strict asepsis is mandatory.  相似文献   
139.
140.
At the seedling stage, a small amount of N is required to boost growth of leguminous plants. A pot experiment was conducted to observe the effect of N fertilizer on various growth parameters and nodulation behavior of Pongamia pinnata under nursery conditions. After the establishment of seedlings, four nitrogen treatments, 0, 40, 80 and 100 kg·ha?1 N were applied in two equal splits. Monthly observations were taken for the morphological parameters viz. plant height, collar diameter, leaf number, root length, root shoot ratio, nodule number and weight per plant. Maximum plant height was recorded after application of N at 40 kg·ha?1. Seasonally, the difference in collar diameter in rainy season was significantly higher than in winter or summer. However, more leaves were produced per plant at N-40 and N-100 treatments in winter and rainy seasons. Higher root length was recorded in rainy season than in winter or summer. Root biomass was higher than for stems or leaves. Seasonal effects of N-80 and N-40 treatments on leaf dry weight were significantly higher than for N-100 or N-0. Stem dry weight was higher at N-40 than at other treatments in winter and summer seasons. Root:shoot ratio was higher throughout winter to early summer. Nodule biomass was 2–3 times higher in rainy season compared to winter or summer. Maximum nodule number and biomass per plant were highest at N-40, followed by N-0, N-80 and N-100 treatments. New nodule formation started from June to the end of September. Maximum biomass per plant was recorded at N-40, followed by N-80, N-100 and N-0. Nitrogen treatment effect and seasonal behaviour interaction were not significant. Significantly higher numbers of nodules per plant were recorded in rainy season followed by summer and winter for all treatments. Higher nitrogen doses suppressed growth while lower doses promoted growth in Pongamia pinnata. Therefore, the lower nitrogen dose i.e., N-40 Kg·ha?1 applied in two equal splits was suitable at the initial nursery stage for the increase in nodulation and biomass 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