全文获取类型
收费全文 | 5212篇 |
免费 | 344篇 |
国内免费 | 3篇 |
专业分类
林业 | 338篇 |
农学 | 131篇 |
基础科学 | 39篇 |
903篇 | |
综合类 | 980篇 |
农作物 | 296篇 |
水产渔业 | 309篇 |
畜牧兽医 | 2070篇 |
园艺 | 122篇 |
植物保护 | 371篇 |
出版年
2023年 | 37篇 |
2022年 | 38篇 |
2021年 | 75篇 |
2020年 | 90篇 |
2019年 | 99篇 |
2018年 | 109篇 |
2017年 | 106篇 |
2016年 | 120篇 |
2015年 | 89篇 |
2014年 | 130篇 |
2013年 | 227篇 |
2012年 | 262篇 |
2011年 | 328篇 |
2010年 | 204篇 |
2009年 | 169篇 |
2008年 | 294篇 |
2007年 | 274篇 |
2006年 | 295篇 |
2005年 | 276篇 |
2004年 | 216篇 |
2003年 | 253篇 |
2002年 | 206篇 |
2001年 | 79篇 |
2000年 | 93篇 |
1999年 | 86篇 |
1998年 | 47篇 |
1997年 | 42篇 |
1996年 | 40篇 |
1995年 | 41篇 |
1994年 | 29篇 |
1993年 | 35篇 |
1992年 | 43篇 |
1991年 | 57篇 |
1990年 | 55篇 |
1989年 | 57篇 |
1988年 | 39篇 |
1987年 | 68篇 |
1986年 | 41篇 |
1985年 | 63篇 |
1984年 | 44篇 |
1983年 | 51篇 |
1982年 | 29篇 |
1980年 | 27篇 |
1979年 | 38篇 |
1978年 | 29篇 |
1976年 | 28篇 |
1973年 | 28篇 |
1970年 | 26篇 |
1969年 | 32篇 |
1924年 | 35篇 |
排序方式: 共有5559条查询结果,搜索用时 15 毫秒
31.
Leonard Omadang Martin Chamai Emmanuel Othieno Andrew Okwi Francis Olaki Inangolet Francis Ejobi Peter Oba Michael Ocaido 《Tropical animal health and production》2018,50(1):11-17
A cross-sectional study was done from March 2013 to May 2014 to assess knowledge, attitudes, and practices towards cystic echinococcosis (CE) or hydatidosis among selected pastoral and agro-pastoral communities in Uganda. A structured questionnaire was administered to 381 respondents. Multivariate logistic regression analysis was done to find the relationship between knowledge about CE and factors such as age, sex, and level of education across all regions. The odds ratio and confidence interval were used to determine the difference in responses across regions. It was shown that age above 36 years was significantly (p < 0.001) associated with awareness about CE in livestock. Likewise, uneducated (p < 0.0001) and agro-pastoralists (p = 0.01) were significantly less knowledgeable than the educated and pastoralists across all regions. The overall knowledge towards CE in livestock was low 17.8% (95% CI = 14.0–21.6). Dog ownership was high and they never dewormed their freely roaming dogs. Dogs shared water with livestock. In conclusion, knowledge about CE in livestock was low across all regions. Therefore, public health education and formulation of policies towards its control by the relevant stakeholders should be done. Also, the true prevalence of CE in livestock needs to be done so that the magnitude and its public health significance are elucidated. 相似文献
32.
D W Fink R P Martin J V Pivnichny J S Shim 《Journal of the Association of Official Analytical Chemists》1978,61(5):1078-1082
An analytical method has been developed for the determination of arprinocid (9-(2-chloro-6-fluorophenylmethyl)-9H-purin-6-amine) in feed, based upon measurement of the absorbance of the diazo chromophore formed from a product of zinc reduction of the drug in acidic solution. The analyte is extracted from the feed into chloroform in the presence of a pH 7 phosphate buffer and isolated by adsorption chromatography on alumina, followed by partitioning between hexane and 0.15M HCl. The reduction product in the aqueous phase is then treated for colorimetric measurement. This procedure has been applied to determining 0.0010--0.0080% arprinocid in feed with a precision of less than 5% relative standard deviation near the middle of this concentration range. Of 32 feed additives examined, only zoalene and sulfamethazine were serious interferences. A study and discussion of several factors, e.g., reaction time, pH, and amount of zinc metal, that affect the analytical reactions are also included. 相似文献
33.
The amounts of organic materials released into soil from roots during the first 4 weeks of growth were determined for 11 cultivars of wheat (Triticum aestivum L.). Carbon loss from roots was measured by supplying 14CO2 continuously to the shoots and measuring the 14C content of the roots, root-free soil, water-soluble material and CO2 flushed from the root chamber. Six cultivars were compared in each of two experiments, with the cultivar Condor common to both experiments. There were no significant differences between cultivars, relative to Condor, for 14C activity present in soil, roots, water-soluble material or rhizosphere CO2. There was a significant difference between cultivars in experiment 1, but not in experiment 2, for the variate log10 (14C lost from roots: 14C translocated to roots).There was evidence that a reduction in growth temperature, within the range 10–15°C, increased carbon loss from wheat roots into the rhizosphere. 相似文献
34.
Axenic cultures of Anacystis, Microcoleus, Plectonema and Synechococcus isolated from Greenfield sandy loam and of Anabaena flos-aquae, Nostoc muscorum and Chlorella pyrenoidosa from other sources were cultured under light and constant aeration and with [U-14C]-glucose in the nutrient medium. Whole cells, cell walls, cytoplasm and extracellular polysaccharides of selected species readily decomposed in the soil and after 22 weeks between 61 and 81% of the added C had evolved as CO2. Complexing of cell wall and cytoplasmic preparations from A. flos-aquae and N. muscorum with model humic acid-type phenolic polymers reduced decomposition of the cell walls by 40% and of the cytoplasm by 70%. Over 50% of the residual 14C activity in the soil amended with whole algal cells remained in the 0.5% NaOH-extracted soil. With exception of Microcoleus sp. more of the residual 14C from cell walls, cytoplasm and polysaccharide fractions was present in the humic acid or fulvic acid fractions. 相似文献
35.
In well-aerated culture solutions Ca-montmorillonite at 0.25% concentration markedly accelerated and increased growth, glucose consumption and CO2 evolution by various Streptomyces, Micromonospora and Nocardia species. The montmorillonite was a little more active than Ca-humate and was usually still but somewhat less effective when confined to dialysis tubing. Ca-exchange resin, Na2SiO3 and finely powdered CaCO3 exerted very little or no effect. In many cultures the relation of glucose consumption to biomass formation indicated a more efficient use of the glucose C for cell synthesis in the presence of clay. In other cultures the greater biomass formation was associated with a more rapid and complete utilization of the glucose present. 相似文献
36.
J.K. Martin 《Soil biology & biochemistry》1977,9(1):1-7
Wheat plants were grown in an atmosphere containing 14CO2 at temperatures of 10°C or 18°C for periods from 3–8 weeks. The plant roots were maintained under sterile or non-sterile conditions in soil contained in sealed pots which were flushed to displace respired 14CO2. The 14C content of the shoots, roots and soil was measured at harvest. The loss of 14C from the roots, expressed either in terms of total 14C recovered from the pots or 14C translocated to the roots, ranged from 14.3–22.6%, mean 17.3% or 29.2–44.4%, mean 39.2%, respectively. The presence of soil microorganisms significantly increased 14CO2 release from the rhizosphere but had no effect on the 14C content of the soil. Fractionation of 6 m HC1 hydrolysates from sterile and non-sterile soils showed the presence in all soils of material behaving as neutral sugars and amino acids, in quantities representing 5.9–9.2% and 13.4–17.2% of the soil 14C content for the sugar and amino acid fractions respectively. It is proposed that a major loss of root carbon resulted from autolysis of the root cortex. Root lysis was increased by soil microorganisms, apparently without penetration of the plant cell walls. 相似文献
37.
38.
Perennial ryegrass and meadow fescue were grown alone and in association in field plots, to gain an idea of the nature and importance of the competitive interactions between them, and their relative contributions to the yield of the newly-established sward.
Experiments over 10 weeks and 9 months both showed that the contribution by fescue to the overall dry-matter yield was severely restricted by perennial ryegrass. There were no deaths of fescue plants during the experimental period (which included an overwintered treatment). The depression in yield was rather a result of a marked decrease in size and weight of the individual plants, brought about by competition for light and nutrients from the faster-growing ryegrass. 相似文献
Experiments over 10 weeks and 9 months both showed that the contribution by fescue to the overall dry-matter yield was severely restricted by perennial ryegrass. There were no deaths of fescue plants during the experimental period (which included an overwintered treatment). The depression in yield was rather a result of a marked decrease in size and weight of the individual plants, brought about by competition for light and nutrients from the faster-growing ryegrass. 相似文献
39.
40.