全文获取类型
收费全文 | 335篇 |
免费 | 11篇 |
国内免费 | 12篇 |
专业分类
林业 | 17篇 |
农学 | 14篇 |
基础科学 | 9篇 |
12篇 | |
综合类 | 140篇 |
农作物 | 17篇 |
水产渔业 | 20篇 |
畜牧兽医 | 110篇 |
园艺 | 15篇 |
植物保护 | 4篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 1篇 |
2019年 | 7篇 |
2018年 | 2篇 |
2017年 | 8篇 |
2016年 | 14篇 |
2015年 | 8篇 |
2014年 | 17篇 |
2013年 | 16篇 |
2012年 | 29篇 |
2011年 | 32篇 |
2010年 | 17篇 |
2009年 | 32篇 |
2008年 | 15篇 |
2007年 | 25篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有358条查询结果,搜索用时 15 毫秒
321.
采用层次分析和加权评分相结合的评价系统,以木莲属植物的园林景观应用为目的,根据观赏价值、资源潜力、生物学特性三大类13个指标,对26种木莲属植物的园林观赏价值进行评价。筛选出适宜华南地区园林应用的种类,有亮叶木莲、马关木莲、木莲、大叶木莲、海南木莲、毛桃木莲、乳源木莲、大果木莲等,评价结果与实际情况较为一致。此评价可以为育种目标的确定和育种亲本的选配提供依据,还可以很好地了解木莲属各个种的优缺点,为建立木莲属园林植物核心种质资源库提供数据支持,也便于人们根据各自的目标进行选择。 相似文献
322.
Hem-fir plywood were exposed to two brown rot fungi, Gloeophyllum trabeum and Postia placenta, and one white rot fungus, Trametes versicolor, to investigate the effect of fungal decay on mechanical properties of plywood. Results showed that modulus of rupture (MOR) and modulus of elasticity (MOE) of hem-fir plywood declined significantly by inoculating fungi, and weight loss of sample had a modest decrease. The fungi also made a greater effect on MOR than on MOE. Of three fungi, Postia placenta caused a most significant weight loss, and Gloeophyllum trabeum resulted in a largest flexural properties loss. Substantial declines in MOR and MOE of hem-fir plywood were also observed when the plywood samples were stored under wet conditions over 15 weeks, even in the absence of fungal attack. 相似文献
323.
324.
《动物营养(英文)》2021,7(4):917-926
This experiment was conducted to investigate the effects of partial replacement of steam-flaked corn (SFC) with shredded sugar beet pulp (SBP) in the starter diet on selective intake (sorting), feeding and chewing behavior, blood biochemical parameters, and growth in newborn female Holstein dairy calves. A total of 48 calves (3 d old; 40.1 ± 0.84 kg body weight; mean ± SE) were randomly assigned to 1 of 2 feeding treatments containing 0 or 25% SBP (percentage of dry matter [DM]) in the starter diet. Calves were weaned on d 61 and remained in the study until d 81. Intake of starter feed and total intake of DM (milk DM + starter feed DM), crude protein, and neutral detergent fiber were increased (P < 0.05) by feeding SBP; however, intake of starch (P < 0.01) and total intake of ether extract (P = 0.03) were decreased with no apparent effect on total intake of ME. Average daily gain, feed efficiency, final weight, and skeletal growth also showed no significant changes. Circulating concentrations of glucose, total protein, and albumin were not affected by partial replacement of SBP with SFC; however, higher concentrations of blood urea-N (P = 0.01) and a lower albumin-to-globulin ratio (P = 0.03) were observed in SBP- vs. SFC-fed calves. Calves fed SBP sorted more for particles retained on the 4.75-mm sieve (P = 0.02) and against particles retained on the 0.6-mm sieve and bottom pan (P < 0.01). Intake of neutral detergent fibers and starch from particles retained on all sieve fractions was increased and decreased (P < 0.01), respectively, by replacing SFC with SBP. Replacement of SBP with SFC was associated with increased meal length and meal size and increased rumination frequency and length, but decreased intervals between rumination (P ≤ 0.01). Calves fed SBP spent more time eating, rumination, and standing and less time lying and non-nutritive oral behaviors (P < 0.01). In general, 25% replacement of SFC with SBP did not affect calf performance but increased time spent rumination and eating and decreased non-nutritive oral behaviors. 相似文献
325.
KN Haffer 《畜牧与生物技术杂志(英文版)》2012,3(1):21-7
The purpose of the study was to test the therapeutic effects of novel vaccines for reducing weight gain and increasing weight loss in diet induced obesity (DIO) model. Male C57BL/6 J mice, fed a 60% Kcal fat diet for 8 weeks prior to the start of the study, were vaccinated via the intraperitoneal route with two formulations (JH17 & JH18) of chimeric-somatostatin vaccines at 1 and 22 days of the study. Control mice were injected with PBS. All mice continued to be feed the 60% Kcal fat diet for the 6 week study. Body weights were measured two times a week and food intake was measured weekly. At week 6, mice were euthanized and a terminal bleed was made and antibody levels to somatostatin and levels of insulin-like growth factor 1 (IGF-1) were determined. Vaccination with both vaccine formulations induced a statistically significant body weight change over the study period, as compared with PBS controls. Percentage of baseline body weight was also significantly affected by vaccination during the study period. Vaccinates finished the study at 104% and 107% of baseline weight, JH17 & JH18 respectively, while untreated controls reached 115% of baseline weight. Food intake per mouse was similar in all mouse groups during the entire study. Control mice did not demonstrate any antibody titers to somatostatin, while all vaccinated mice had measurable antibody responses (> 1:500,000 titer). IGF-1 levels were not statistically significant among the groups, but were elevated in the JH18 vaccinates (mean 440.4 ng/mL) when compared with PBS controls (mean 365.6 ng/mL). Vaccination with either JH17 or JH18 chimeric –somatostatin vaccines produced a statistically significant weight loss as compared with PBS controls (P < 0.0001), even though the DIO mice with continually fed a 60% Kcal fat diet. The weight loss/lower weight gain observations were even more significant, as all mice consumed similar amounts of food for the entire study. The presence of high levels of anti-somatostatin antibodies at 6 weeks was correlative with the weight observations and confirmed the success of vaccination. 相似文献
326.
毛白杨根系分布的研究 总被引:13,自引:1,他引:13
对沙地上不同年龄毛白杨人工林的根系,从形态、数量和分布密度3个方面进行了调查研究。结果表明,其根系为水平斜生复合根型,14a生林木根系的分布深度可达4.5m,水平根幅达8m左右。以重量划分7,9,14a生林分的根系,分别集中在0 ̄60cm、0 ̄100cm和0 ̄100cm土层内,占根系总重的86%以上,树木周围2.0m范围内根系的重量占总根量的80%以上。以根系长度衡量,整个林地内根系分布较均匀,0 相似文献
327.
[目的]建立基于属性差异度的多属性决策方法并说明其在水稻优选中的应用。[方法]提出属性间贴近度的概念,在此基础上对属性间的差异度进行研究,并对基于属性差异度的权重确定方法进行分析。[结果]得到了1种基于属性差异度的多属性决策方法,并针对水稻优选问题说明了该方法具有应用及可行性。[结论]丰富了多属性决策中属性权重确定的问题,并为科学合理地选择水稻品种问题提供了必要的理论支撑。 相似文献
328.
C. J. Ng’ang’a N. Maingi P. W. N. Kanyari W. K. Munyua 《Tropical animal health and production》2009,41(6):921-926
The effects of anthelmintics treatments in controlling gastrointestinal nematodes in breeding ewes in a semi-arid area of
Kenya were determined. The study carried out during two breeding seasons, between June 2000 and December 2001 where albendazole
was administered to groups of ewes, 2 weeks before mating, 3 weeks to lambing and mid lactation indicated significantly lower
nematode egg counts in treated than untreated groups of ewes. In the first breeding season, reduced rainfall resulted in pasture
scarcity and weight loss in both groups of ewes through out the gestation period, but losses were higher for the untreated
group. In the second season, both groups of ewes showed a steady increase in weight gain during the gestation period and post-partum,
but weight gains were higher in the treated group. In lambs, weight gains at 6 weeks were higher for treated ewes than control
groups, in both breeding seasons. The results of this trial indicate that anthelmintic treatments in breeding ewes in the
study area are beneficial in reducing gastrointestinal nematode infections and improving performance of the ewes and their
lambs. In addition to the treatments, breeding ewes should be given feed supplementation particularly during periods of pasture
scarcity. 相似文献
329.
Optimum manufacturing conditions of activated carbon fiber absorbents. II. Effect of carbonization and activation conditions 总被引:1,自引:0,他引:1
In this paper, viscose rayon-based knitted fabrics were utilized as the precursor to produce activated carbon fiber absorbents
(ACFA). The effects of carbonization and activation conditions on characteristics (ACFA) were examined. Experimental results
revealed that increasing the flow rate of environmental gas N2 and steam activator used in conjunction and decreasing the production rate of ACFA can obtain better pore properties. However,
higher flow rate of steam activator and lower production rate of ACFA reduced the weight yield. According to our findings,
to maintain good absorption property of ACFA, the optimum manufacturing conditions are flow rate of gas N2 at 80 cc/min, flow rate of steam activator at 60 ml/min, and production rate of ACFA at 30 cm/min, with flame retardant reagent
concentration maintained at 30%. Under these conditions, the weight yield can be up to 40.85% and the BET surface area can
exceed 1500 g/m2. 相似文献
330.
In recent years the freshwater fish market has required more processed goods, as young consumers purchase ready-to-cook food
products. In Middle European aquaculture systems carp are the main species. The appearance of new species (African catfish,
trout, salmon), as well as the improved import possibilities of value-added fish products have introduced new challenges for
fish farmers. In order to maintain the share of carps in fish sales, it is indispensable to develop up-to-date products that
meet the needs of present generations. It is necessary to find processing methods that remove the fish bone and the off flavours
occurring in Cyprinids. Smoking of carp has a strong tradition in the region, thus there are advantages to the development
of smoked carp products, mainly in the form of boned fillets. The present study investigates two smoking methods aimed at
ensuring basic information for product innovation. Analyses of the variation of weight, dry matter and lipid content during
hot and cold smoking are presented for the case of three species: the common, silver, and grass carp. To determine the most
acceptable products, the paper details the results of organoleptic tests, in which five characteristics (appearance, consistence,
flavour, smell, and succulence) were investigated. Evaluation results indicate that the hot-smoked carp products are more
acceptable, therefore it is hoped that these products, packed in a modified atmosphere, will achieve a strong market share
in the near future. 相似文献