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   124篇
  免费   6篇
林业   5篇
农学   3篇
基础科学   6篇
  36篇
综合类   14篇
农作物   3篇
水产渔业   4篇
畜牧兽医   46篇
园艺   2篇
植物保护   11篇
  2023年   2篇
  2022年   1篇
  2021年   2篇
  2020年   5篇
  2019年   2篇
  2018年   5篇
  2017年   6篇
  2016年   8篇
  2015年   2篇
  2014年   11篇
  2013年   11篇
  2012年   5篇
  2011年   2篇
  2010年   4篇
  2009年   8篇
  2008年   5篇
  2007年   4篇
  2006年   2篇
  2004年   2篇
  2003年   2篇
  2002年   2篇
  2001年   3篇
  2000年   3篇
  1999年   4篇
  1998年   4篇
  1997年   2篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1985年   2篇
  1982年   2篇
  1973年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有130条查询结果,搜索用时 31 毫秒
41.
Investigations have been carried out to determine the influence of chlorocholine chloride on induction of the resistance mechanisms of Stevia rebaudiana against leaf spot disease, caused by Alternaria alternata. The paper also focuses an impact of chlorocholine chloride induced resistance on reduction of leaf spot disease. Chlorocholine chloride is attributed to its significant role in defence responses through augmentation of phenol and salicylic acid content as well as stimulation of phenylalanine ammonia lyase and peroxidase activity in S. rebaudiana following inoculation with A. alternata. Histochemical studies revealed that fungal invasion as well as infection process was appreciably reduced in chlorocholine chloride treated plants through peroxidase-H2O2 mediated strengthening of cell wall. The overall study highlights the significant role of chlorocholine chloride in induction of resistance in S. rebaudiana against A. alternata.  相似文献   
42.
Soft rot of Chinese cabbage is a disease of great economic importance to the State of Pernambuco, Brazil. The present study aimed to evaluate the effect of two calcium sources in different concentrations (calcium nitrate [Ca(NO3)2] at 0, 0.15 and 0.3 g l?1 and calcium chloride (CaCl2) at 0, 1 and 5 g l?1) that were applied through two methods (leaf spraying and soil drenching) on the control of soft rot. Further, it aimed to analyze calcium absorption by the plant and to determine calcium’s role in leaf and cell structure using microscopy. Ca(NO3)2 applied by both methods was effective in controlling soft rot caused by Pectobacterium carotovorum subsp. carotovorum, as it reduced the disease by up to 48.5 % when sprayed onto the leaves (0.15 g l?1). A significant increase in the leaf calcium content was observed only in the plants that were sprayed with higher doses of Ca(NO3)2 and CaCl2. In all of the calcium treatments, light microscopy analyses revealed an increased number of chloroplasts and improved structuring of the palisade parenchyma, while transmission electron microscopy analyses revealed an increased cell wall thickness that was especially evident for the 0.15 g l?1 Ca(NO3)2 treatment applied by leaf spraying and soil drenching.  相似文献   
43.
Long-term experimental sites are expected to provide important information regarding soil properties as affected by management practices. This study was designed to examine the effects of continuous fertilization, and manuring on the activities of enzymes involved in mineralization of C, N, and P on a long term (33 years) field trial under sub-temperate conditions in India. Treatments at the site included application of recommended doses of nitrogen and phosphorus (NP), nitrogen and potassium (NK), nitrogen, phosphorus and potassium (NPK), farmyard manure (FYM) with N (N + FYM), FYM with NPK (NPK + FYM) and un-amended control (C). The study was done under rainfed soybean–wheat rotation. Manure application increased soil carbohydrate, dehydrogenase, acid and alkaline phosphatases, cellulase, and protease activity significantly. Urease activity was not influenced by the manure treatment and the activity was highest in controls. Both acid and alkaline phosphatase activities were negatively influenced by chemical fertilizer treatment. Almost all the enzymes studied were significantly correlated with soil C content. The results suggest that application of FYM directly or indirectly influences the enzyme activity and it in turn regulates nutrient transformation.  相似文献   
44.
45.
Summary The anaesthetic effects of intravenous tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg (TK) and tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg-xylazine 0.11 mg/kg (TKX) were evaluated in six wethers. Heart rate, respiration rate, arterial blood pressure, and the electrocardiogram were monitored during anaesthesia. Analgesia was tested by electrical stimulation in the left flank. Atropine (0.03 mg/kg) was given intramuscularly before induction, but after recording of baseline heart rate and respiratory rate. The duration of analgesia was 28.7 ± 6.9 min with TK and 82.8 ± 26.6 min with TKX. Heart rate increased significantly within 5 min after TK or TKX administration. Respiratory rate remained unchanged after TK administration, but increased significantly from 5 to 45 min after TKX administration. Arterial blood pressure decreased significantly at 15 min with TK and 30 min with TKX. Sheep remained recumbent for 201 min with TK and 166 min with TKX. All recovered uneventfully. We conclude that either TK or TKX may be used for anaesthetising sheep.  相似文献   
46.
This study was conducted to evaluate the utilisation of the residual feed intake (RFI ) as a feed efficiency selection tool and its relationship with methane emissions. Eighteen Murrah buffalo (Bubalus bubalis ) heifers were fed ad libitum with total mixed ration (TMR ) for 120 days. Based on linear regression models involving dry matter intake (DMI ), average daily gain (ADG ) and mid‐test metabolic body size (MBW 0.75), heifers were assigned into low and high RFI groups. The RFI varied from ?0.09 to +0.12 kg DM /day with average RFI of ?0.05 and 0.05 kg DM /day in low and high RFI heifers respectively. Low RFI heifers ate 11.6% less DM each day, yet average daily gain (ADG ) and feed utilisation were comparable among low and high RFI groups. Low RFI heifers required significantly (< .05) less metabolizable energy for maintenance (ME m) compared to high RFI heifers. Apparent nutrient digestibility showed non‐significant difference (p >  .05) among low and high RFI groups. Although the nitrogen balance was similar among heifers of low and high RFI groups, nitrogen metabolism was significantly higher (> .05) in high RFI heifers. Comparison of data from heifers exhibiting the low (n  = 9) and high (n  = 9) RFI showed that the low RFI heifers have lower enteric methane production and methane losses than high RFI heifers. In conclusion, results of this study revealed that selection of more efficient buffalo heifers has multiple benefits, such as decreased feed intake and less emission of methane.  相似文献   
47.
48.
The current study investigated the possibility of using the AMH concentration as a predictor of the ability of Korean Hanwoo cows to produce cumulus‐oocyte complexes, embryos that survive after transfer as well as the pregnancy outcome of surrogates. Eight sessions of ovum pick‐up (OPU) were performed with 19 donor cows at an interval of 3–4 days. Antral follicle count (AFC), oocyte quality and in vitro embryo development were recorded for each cow. Embryos produced from cows with different AMH profiles were transferred into recipients (n = 96). Cows in the high (≥0.25 ng/ml) and intermediate (0.1≥ to <0.25 ng/ml) AMH groups had a significantly higher AFC per OPU session (20.40 ± 1.36 and 16.91 ± 1.52, respectively; mean ± standard deviation) than cows in the low AMH group (<0.1 ng/ml; 12.19 ± 2.14). In addition, more cumulus‐oocyte complexes per donor were recovered in the high (11.46 ± 1.22) and intermediate (7.38 ± 0.83) AMH groups than in the low AMH group (4.77 ± 0.44). The percentage of oocytes reached blastocyst stage was significantly higher in the intermediate (47.0%) and high (38.5%) AMH groups than in the low AMH group (32.3%). The number of embryos produced per cow was higher in the high (3.9 ± 0.2) and intermediate (6.9 ± 0.6) AMH groups than in the low AMH group (2.2 ± 0.3). The percentage of embryos that gave birth to viable calves when transferred into recipients was higher for those derived from cows in the intermediate AMH group (50.7%) than for those derived from cows in the low (35.7%) and high (36.4%) AMH groups. In conclusion, a single measurement of AMH concentration predicted the in vitro embryo production potential of donor Korean native cows before OPU and is linked with embryo viability after transfer into recipients.  相似文献   
49.
The hypothesis was tested, whether soil wetness and phosphorus status could regulate the evapotranspiration rate (ETR), which is of special interest in the lower Gangetic Plain. Rajmash was grown during November-February of 2003-2004 and 2004-2005 on a sandy loam soil, and was irrigated when cumulative pan evaporation (CPE) attained the value of 33 mm (CPE33); 44 mm (CPE44) and 66 mm (CPE66). Four levels of phosphate application were 0 kg P2O5 ha−1 (P0); 30 kg P2O5 ha−1 (P30); 60 kg P2O5 ha−1 (P60) and 90 kg P2O5 ha−1 (P90). Seed yield under CPE33 was 1.37 Mg ha−1 and reduced by 18% and 35%, respectively under CPE44 and CPE66. Continuous increasing trend in yield was recorded with an increase in phosphate level (PL). Irrespective of growth stages, similar trends were recorded for leaf area index (LAI). Maximum variation in LAI among the treatments was recorded at 60 days after sowing. On average, actual ETR was 1.37 mm day−1 under CPE33 and declined by 13% and 16% under CPE44 and CPE66, respectively. Variation in ETR under different PL was highest under CPE33 and lowest under CPE44. Except P90, irrespective of PL, highest value of water use efficiency (WUE) was obtained under CPE44. However, magnitude of net evapotranspiration efficiency (WUEET) and irrigation efficiency (WUEI) attained the highest level under CPE33 regime. All water use indices showed an increasing trend with the increase in phosphate level from 0 to 90 kg ha−1. Impact of phosphorus on various parameters was pronounced under CPE33.  相似文献   
50.
A protocol of multiplex RT-PCR in a one-tube system for the detection of the most common stone fruit trees viruses [e.g., plum pox virus (PPV), prune dwarf virus (PDV), and Prunus necrotic ringspot virus (PNRSV)], including the internal control of NADH dehydrogenase subunit 5 (nad5) gene are described here. The method specificity was tested on more than 80 different samples with various isolates and strains of the viruses. It showed that the targeted viruses produced the expected amplicons, whereas all other related viruses produced only the nad5 internal control amplicon. The method sensitivity was evaluated by comparing it with Simplex RT-PCR with the same primers; no significant differences in detection limits were recorded. Furthermore, the competitiveness of the primers in the assay was tested by serial RNA dilutions of samples with mixed and single infections. The least competitive was the internal control nad5 gene primer pair; therefore, there is a reduced risk of false negatives as all the other primers tend to be more efficient in the given primer cocktail than in the primers for internal control.  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