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   792篇
  免费   56篇
  国内免费   3篇
林业   60篇
农学   71篇
基础科学   4篇
  114篇
综合类   80篇
农作物   89篇
水产渔业   101篇
畜牧兽医   273篇
园艺   17篇
植物保护   42篇
  2024年   1篇
  2023年   2篇
  2022年   25篇
  2021年   31篇
  2020年   25篇
  2019年   24篇
  2018年   25篇
  2017年   20篇
  2016年   22篇
  2015年   31篇
  2014年   25篇
  2013年   41篇
  2012年   52篇
  2011年   62篇
  2010年   37篇
  2009年   56篇
  2008年   61篇
  2007年   36篇
  2006年   47篇
  2005年   33篇
  2004年   48篇
  2003年   29篇
  2002年   19篇
  2001年   13篇
  2000年   13篇
  1999年   5篇
  1998年   9篇
  1997年   10篇
  1996年   4篇
  1995年   3篇
  1993年   8篇
  1992年   5篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1979年   5篇
  1978年   1篇
  1976年   2篇
  1970年   2篇
  1965年   1篇
  1964年   4篇
  1963年   3篇
排序方式: 共有851条查询结果,搜索用时 15 毫秒
131.
We evaluated the proximate composition, free sugar content, fatty acid composition, carotenoid content, total phenol content, and radical scavenging activity of the grain from various Korean maize hybrid cultivars grown in two different cropping seasons. The moisture, crude ash, crude fat, crude protein, total starch, and amylose contents were significantly higher in most of the maize hybrid cultivars when grown in the early-season than when grown in the late-season. The free sugar content, fatty acid composition, carotenoid content, and total phenol content differed significantly between cultivars and cropping seasons. The highest unsaturated fatty acid compositions of maize hybrids of early-season and late-season were 86.05 and 86.29%, respectively, in the Daanok cultivar. The carotenoid contents were significantly higher in maize hybrids of late-season compared to those of early-season. The highest total phenol content was 108.09 mg/100 g in Singwangok of the late-season. The radical scavenging activity of maize hybrids differed significantly between cultivars and cropping seasons.  相似文献   
132.
This research was conducted to investigate the effects of different medium compositions on physicochemical properties and the growth of two tomato varieties. Five treatments were applied, combining medium composition with rice husk ash (RHS) and coconut fiber (CF) with the following proportions: 1/3 Peat moss + 1/3 rice husk ash + 1/3 coconut fiber (T1); 1/3 Vermicompost + 1/3 rice husk ash + 1/3 coconut fiber (T2); 1/3 Cattle manure compost + 1/3 rice husk ash + 1/3 coconut fiber (T3); 1/3 Chicken manure compost + 1/3 rice husk ash + 1/3 coconut fiber (T4); 1/3 Hog manure compost + 1/3 rice husk ash + 1/3 coconut fiber (T5). The results demonstrated that between pH, electrical conductivity (EC) value, and nutrient content in the media, there was a significant difference that led to different concentrations of total macro- and micronutrients in the shoots of both varieties. In addition, the root weight, shoot weight, and root volume were affected by medium composition for two varieties in seedling stage. A mixture of cattle manures composted with RHS and CF under the rate (1:1:1 by volume), respectively, gave the highest value of germination rate, plant height, leaf number, and plant biomass. Medium composition significantly influenced the germination rate and elongation of seedlings, specifically for each tomato variety. Therefore, cattle manure compost as a medium supplement improves seedling quality and growth of the two tomato varieties.  相似文献   
133.
1. The objective of this study was to compare the effects of pre- and post-pellet whole grain wheat additions to diets on growth performance, gizzard and pancreas development, nutrient utilisation and starch and protein (N) digestibility coefficients in broiler chickens via an equilateral triangle response surface design.

2. The three apical treatments of the equilateral triangle comprised (1A) a standard diet containing 600 g/kg ground wheat, (2B) the same diet containing 600 g/kg pre-pellet whole wheat and (3C) the same diet containing 300 g/kg ground wheat and 300 g/kg post-pellet whole wheat. Seven blends of the three apical diets were located within the triangle to complete the design and a total of 360 male Ross 308 chicks were offered the ten experimental diets from 7 to 28 d post-hatch. Model prediction and response surface plots were generated with R 3.0.3 software.

3. The most efficient FCR of 1.466 was observed in birds offered an almost equal mixture of the pre- and post-pellet whole grain apical dietary treatments, which corresponded to 172 g/kg ground grain, 256 g/kg pre-pellet whole grain, 172 g/kg post-pellet whole grain in a diet containing 600 g/kg wheat.

4. The most efficient energy utilisation (ME:GE ratio of 0.766) was observed in birds offered a blend of the ground grain and pre-pellet whole grain apical dietary treatments which corresponded to a mixture of 384 g/kg pre-pellet whole grain and 216 g/kg ground grain.

5. Pre-pellet whole grain feeding generated the most pronounced responses in increased relative gizzard contents, reduced gizzard pH and increased relative pancreas weights. Consideration is given to the likely differences between pre- and post-pellet whole grain feeding.  相似文献   

134.
郭清保 《农业展望》2010,6(5):23-24,32
自2009年以来,中国云贵川遭受了较为严重的旱情,由于此3地均为中国菜籽的生产与消费区,引起了市场对新季菜籽产量的担忧。同时,根据国家政策规定,2010年5月21日全国夏油菜籽主产省将继续实施菜籽临储收购政策,收购价格为3.90元/kg。在减产与政策支撑下,2010年的中国菜籽市场走势也更加引人关注。  相似文献   
135.
Understanding the molecular details of CO(2)-sorbent interactions is critical for the design of better carbon-capture systems. Here we report crystallographic resolution of CO(2) molecules and their binding domains in a metal-organic framework functionalized with amine groups. Accompanying computational studies that modeled the gas sorption isotherms, high heat of adsorption, and CO(2) lattice positions showed high agreement on all three fronts. The modeling apportioned specific binding interactions for each CO(2) molecule, including substantial cooperative binding effects among the guest molecules. The validation of the capacity of such simulations to accurately model molecular-scale binding bodes well for the theory-aided development of amine-based CO(2) sorbents. The analysis shows that the combination of appropriate pore size, strongly interacting amine functional groups, and the cooperative binding of CO(2) guest molecules is responsible for the low-pressure binding and large uptake of CO(2) in this sorbent material.  相似文献   
136.
Micropigs are the most likely source animals for xenotransplantation. However, an appropriate method for evaluating the lung of micropigs had not been established. Therefore, this study was performed to evaluate the feasibility of 64-channel multi-detector row computed tomography (MDCT) to measure the diameter of the pulmonary arteries and the lung volume in micropigs. The mean diameters of the trachea, and left and right bronchi were 1.6 ± 0.17, 1.18 ± 0.14, and 1.1 ± 0.11 cm, respectively. The mean diameters of the main, right, and left pulmonary arteries were 1.38 ± 0.09, 1.07 ± 0.26, and 0.98 ± 0.13 cm and the diameters of right, left, and common inferior pulmonary veins were 0.97 ± 0.20, 0.76 ± 0.20, and 1.99 ± 0.26 cm, respectively. The mean lung volume was 820.3 ± 77.11 mL. The data presented in this study suggest that the MDCT may be a noninvasive, rapid, and accurate investigational method for pulmonary anatomy in living lung donors.  相似文献   
137.
Lignin and cellulose contents and wood basic density were related to diameter at breast height (DBH) in six fast-growing and five slow-growing families from a combined progeny test and seedling seed orchard of Eucalyptus urophylla grown for 10 years in northern Vietnam. The mean cellulose content of the fast-growing families was significantly higher than that of the slow growing-families (40.0 and 37.1%, respectively), and for individual trees cellulose content was significantly correlated phenotypically with DBH. Wood basic density was significantly lower in the fast-growing group than in the slow-growing group (0.506 and 0.535 g cm−3, respectively), and was significantly negatively correlated phenotypically with DBH. The lignin contents were not significantly different between groups. Cellulose content and wood basic density were not correlated. The main conclusion is that there is no obstacle to combining high growth rate with high cellulose content, for plantation of forests intended mainly for pulpwood.  相似文献   
138.
为揭示新疆家畜地理分布气候规律,利用畜牧业统计资料及其气候资料,应用相关分析方法研究了新疆各种草食家畜的地理分布与气候条件之间关系,并在此基础上采用回归方法建立了新疆家畜地理分布气候模式。结果表明:(1)牛、马要求温凉湿润的气候条件,驴、骡、骆驼、山羊和绵羊对炎热干燥的气候条件有很强的适应能力。骆驼、山羊和骡对强光照条件的适应能力强,而绵羊的适应能力较差。(2)草食家畜的地理分布与气候条件关系密切,气候模式能够反映气候条件对草食家畜地理分布的影响。  相似文献   
139.
140.
In this study fusaricidin, a cyclic depsipeptide isolated from Paenibacillus polymyxa E681 (E681), was demonstrated to control Phytophthora blight infection caused by Phytophthora capsici in red-pepper. The minimal inhibitory concentration (MIC) of fusaricidin was found to be 16 ppm against P. capsici. The disease severity of P. capsici was 40% at 0.1 ppm of fusaricidin when compared with water-treated control (81.7%) on post-treatment, whereas the disease severities on pre-treatment were 45% and 83.3% in fusaricidin (0.1 ppm) and water-treated control, respectively, in red-pepper plants. Significant (P?<?0.05) disease suppression was observed on treatment with fusaricidin (0.1 ppm) by foliar spray and soil drench. The disease severity was drastically reduced to 3.3% by soil drench of fusaricidin (1.0 ppm), whereas in water-treated control, the disease severity was 83.3% in the first experiment. Fusaricidin at 0.1 ppm reduced disease severity of P. capsici to 27.5% when compared with positive control (43.1%) and water-treated control (66.2%) in the second experiment. Soft rot disease in tobacco was suppressed upon treatment with fusaricidin at 1.0 ppm by leaf infiltration. RT-PCR analyses of Arabidopsis thaliana revealed that there was an up-regulation of pathogenesis-related (PR) gene expression in wild type A. thaliana (Col-0), while there was no accumulation of PR genes, which implies that the mechanism of protection might be based on a salicylic acid-dependent pathway. This is the first report that fusaricidin exhibits protection against plant pathogens in addition to activity as an antibiotic agent. Hence, E681 can play a role in plant protection by secretion of ISR elicitors including fusaricidin.  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