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   64篇
  免费   6篇
林业   14篇
农学   3篇
  19篇
综合类   1篇
农作物   2篇
水产渔业   14篇
畜牧兽医   8篇
植物保护   9篇
  2023年   1篇
  2022年   2篇
  2021年   2篇
  2020年   2篇
  2019年   4篇
  2018年   5篇
  2017年   5篇
  2016年   3篇
  2015年   3篇
  2014年   9篇
  2013年   4篇
  2012年   4篇
  2011年   8篇
  2010年   2篇
  2008年   1篇
  2007年   2篇
  2006年   1篇
  2005年   5篇
  2004年   3篇
  2003年   2篇
  1990年   1篇
  1984年   1篇
排序方式: 共有70条查询结果,搜索用时 171 毫秒
21.
In order to respond to global competition challenges, the wood-processing industry in Finland and elsewhere is outsourcing roundwood harvesting to harvesting contractors. The industry also seeks to negotiate with fewer, larger and more diverse contractor enterprises. The weak profitability, liquidity and solvency of harvesting contractors and the consequent difficulty in hiring qualified machine operators make networking and enterprise growth a complicated process. Financial data of 1,060 Finnish wood harvesting contractors from the period 2001 to 2007 were studied using the ‘closing of the accounts’ data. The material represents most of the full-time contractors. For 2007 net profit was about 6%, credit share of turnover over 50% and median financial reserve €18,000. High machine depreciation and interest expenses together with low solidity make it difficult for small enterprises to absorb seasonal variations and to cope with recessions. Profitability varies considerably amongst smallest enterprises, which most often are sole-operator enterprises. Moreover, even the median profit of the smallest enterprises tends to be negative, which means that enterprise capital will be consumed and many enterprises are at risk of failure. Larger enterprises are more likely to be limited liability companies. Their median profit is clearly positive and the profit varies relative little between enterprises.  相似文献   
22.
Polyphenols extracted from evening primrose seeds (industrial waste product) were studied as apoptosis inducers in human colorectal adenocarcinoma Caco-2 and HT-29 cell lines and in rat normal intestinal IEC-6 cells. The extract dose-dependently inhibited the growth of Caco-2, HT-29, and IEC-6 cells. However, nuclear DNA fragmentation characteristic of apoptosis was observed only in Caco-2. After 72 h of incubation with the extract at 150 μM gallic acid equivalents (44.1 μg extract/mL), Caco-2 cell numbers decreased to 19% of control and 48.8% of the cells were identified by flow cytometry as apoptotic. Under the same conditions only 8% of HT-29 cells and 12.6% of IEC-6 cells exhibited hypodiploid DNA content. The effects of the extract and its fractions on phosphatidylserine exposure and cell membrane integrity were assessed by high content screening image cytometry. The fractions strongly and dose-dependently reduced Caco-2 cell numbers, whereas HT-29 and IEC-6 cells were affected to lesser extents.  相似文献   
23.
European Journal of Forest Research - Increasing areas of gradation, making it difficult or impossible to perform restorations and forestations, and as causing tree crown damage, result in the need...  相似文献   
24.
25.

The influence of dietary protein content and composition on growing-furring blue fox ( Alopex lagopus ) was studied with three protein levels [15%, 22.5% and 30% of metabolizable energy (ME) from protein]. The two lowest diets were fed as such, or as supplemented with L-methionine or lysine. Growth, from the start of the experiment in July to mid-September, improved with increasing protein level ( P < 0.01). Lysine supplementation, unlike methionine, decreased early growth ( P <0.05). During the last months of the experimental period, differences in weight gain between the groups evened out. Skin length and quality declined with decreasing protein level ( P <0.05). Methionine and lysine had opposite effects on skin length ( P <0.10). For normal body growth and skin length, a level of 0.40 g of digestible L-methionine MJ -1 ME, and 25-32% protein in feed dry matter, was required. When feed ingredients are deficient in methionine, a supplementation is recommended. Methionine is the first limiting amino acid of the two amino acids studied here.  相似文献   
26.
27.
The effectiveness of applying Ovaprim [(D-Arg6, Pro9NEt)-sGnRH + domperidone] and Ovopel [(D-Ala6, Pro9NEt)-mGnRH + metoclopramide] to male barbel Barbus barbus (L.) 6, 12 and 24 h after hormonal stimulation was analyzed. The control group (Control) during each time interval was stimulated with 0.9 % NaCl. Milt was collected from seven fish only once (n = 7) for Ovopel, Ovaprim and Control group in order to determine total volume of milt, volume of milt per kg of body weight, sperm concentration, total sperm production, seminal plasma osmotic pressure, pH of milt and pH of seminal plasma. Woynarovich’s solution (68 mM NaCl + 50 mM urea) with the addition of 0.5 % BSA (pH 7.7; 181 mOsm kg?1) was used as the activating liquid. Selected parameters of sperm motility (MOT %) and progressively motile sperm (%), curvilinear velocity (VCL, μm s?1), straight-line velocity (μm s?1), movement linearity (%), wobbling index (%), amplitude of lateral head displacement (μm) and beat cross frequency (Hz) were determined using the Computer-assisted sperm analysis system. A time of 6 h proved to be too short to obtain milt from barbel following hormonal stimulation with Ovaprim and Ovopel. Extending the time to 12 h, however, resulted in 100 % spermiation in males, regardless of hormonal preparation used for stimulation. The stimulation of spermiation in barbel is best performed using Ovopel 12 h upon application. Extending the latency period to 24 h following the application of this preparation results in a significant decrease in the volume of milt obtained, sperm count and motility parameters, including MOT and VCL, which may influence sperm fertilization ability.  相似文献   
28.
Journal of Plant Diseases and Protection - The assessment of the effectiveness of resistance sources to fungal diseases is a very important issue allowing to determine the possibilities of...  相似文献   
29.
The study investigated effect of dietary supplementation with malic acid, Bacillus subtilis and a mixture of the two (3 × 2 factorial trial) on Nile tilapia (Oreochromis niloticus) health. Treatment groups (T1–T6) were fed diets containing three levels of malic acid (0.0, 5.0 and 10.0 g/kg), each of which was supplemented with 0 and 1.1 × 105 cfu/g B. subtilis, respectively. Each treatment group was assigned randomly to triplicate groups of 35 fish (5.26 ± 0.06 g) in 18 tanks for 84 days. The results indicated that survival was higher in all dietary treatments as compared to the control fed fish. The highest values of FBW, WG and SGR (%), PER, PPV and ER were recorded in groups T4 and T6, which were fed diets supplemented with 5 g malic acid/kg and 1.1 × 105 cfu/g B. subtilis and 10 g malic acid/kg and 1.1 × 10cfu/g B. subtilis, respectively. The best value of FCR was obtained in groups T4 and T6. The lowest total bacterial count in the gut and faeces was detected in fish from group T6. The values of haematocrit, haemoglobin, red blood cells, white blood cells, total protein, albumin and globulin were significantly higher (p < .05) in fish from groups T4 and T6 (diets supplemented with malic acid and Bsubtilis). As compared to the control fed fish, te mixture of these substances are promising as immune enhancher in aquacultured fish.  相似文献   
30.
Effect of the lectin PHA on the feeding behavior of the grain aphid   总被引:1,自引:0,他引:1  
The electrical penetration graph (EPG) method was used to quantify the effect of the lectin PHA (phytohemagglutinin) on the feeding behavior of the grain aphid Sitobion avenae F (Hemiptera: Aphididae). Addition of PHA to an artificial diet affected aphid probing behavior. In general, increasing concentrations of PHA in sucrose-agarose gels significantly reduced the number of aphid probes and extended their duration. Aphids feeding on the gels with lectin (without concentration 50 μg · cm−3) had a prolonged activity (EPG pattern C) that was corresponded to prolonged penetration of the epidermis and mesophyll for aphids feeding on plants. Such insects also showed a significant reduction in salivation and passive ingestion from gels and a reduction in the total number of gel penetrations. At concentrations ≤250 μg · cm−3, PHA reduced feeding behavior on gels, and the EPG data were interpreted to correspond with reduced salivation into phloem sieve elements (EPG pattern E1) and reduced ingestion of phloem sap (EPG pattern E2). PHA also delayed the onset of the first E1 and E2 patterns. At higher concentrations (≥500 μg · cm−3), PHA completely stopped salivation and passive ingestion from gels. Similarly, higher concentration of PHA strongly reduced activity on gels that corresponded to activity in xylem (EPG pattern G); high PHA delayed the onset of the first G pattern and reduced total time of pattern G activity.  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