全文获取类型
收费全文 | 11076篇 |
免费 | 3070篇 |
国内免费 | 342篇 |
专业分类
林业 | 592篇 |
农学 | 859篇 |
基础科学 | 59篇 |
2692篇 | |
综合类 | 1879篇 |
农作物 | 379篇 |
水产渔业 | 2223篇 |
畜牧兽医 | 3509篇 |
园艺 | 176篇 |
植物保护 | 2120篇 |
出版年
2024年 | 17篇 |
2023年 | 57篇 |
2022年 | 93篇 |
2021年 | 234篇 |
2020年 | 596篇 |
2019年 | 1045篇 |
2018年 | 918篇 |
2017年 | 1019篇 |
2016年 | 862篇 |
2015年 | 818篇 |
2014年 | 774篇 |
2013年 | 1168篇 |
2012年 | 1379篇 |
2011年 | 907篇 |
2010年 | 761篇 |
2009年 | 495篇 |
2008年 | 503篇 |
2007年 | 409篇 |
2006年 | 316篇 |
2005年 | 344篇 |
2004年 | 307篇 |
2003年 | 228篇 |
2002年 | 196篇 |
2001年 | 176篇 |
2000年 | 190篇 |
1999年 | 96篇 |
1998年 | 88篇 |
1997年 | 67篇 |
1996年 | 70篇 |
1995年 | 75篇 |
1994年 | 51篇 |
1993年 | 35篇 |
1992年 | 47篇 |
1991年 | 30篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
《Communications in Soil Science and Plant Analysis》2012,43(8):839-852
Abstract The performance of the vanodomolybdate and molybdenum blue methods for the routine determination of phosphate in plant sap were compared in order to assess their suitability for the detection of P deficiency at an early stage of plant growth. The molybdenum blue method was ca 10 times more sensitive than the vanadomolybdate one and required less sap to give a successful test. Recoveries of phosphate added to both sap and solution samples were close to 100% with both methods. The methods were in good agreement over a wide range of phosphate concentrations using sap samples from all leaves during the early stages of P deficiency, but increases in sap background colour caused the vanadomolybdate method to overestimate phosphate concentrations as the deficiency became more acute. Measurements on solutions of similar absorbance showed that the vanadomolybdate method was not significantly more variable than the molybdenum blue method but tended to overestimate phosphate concentration when very small volumes of sap were available. It was concluded that the molybdenum blue method was the most reliable for routine measurements of phosphate in plant sap. 相似文献
112.
《Communications in Soil Science and Plant Analysis》2012,43(6):415-420
Abstract The usefulness of the nitrate‐specific ion electrode (NE) for the determination of nitrate nitrogen (NO3‐N) in surface and ground water was determined. The NE method had several advantages that made it superior to the phenoldisulfonic acid (PDS) method in our environmental quality studies. Samples could be analyzed quickly and with a minimum of sample preparation. Sample coloration and soluble salts did not interfere with the performance of the electrode. Range of detection without dilution was much wider than by the PDS method. Also, the values obtained by the NE method, although slightly greater than those obtained by the PDS method, were satisfactory. 相似文献
113.
Combined effects of temperature and light quality on plants have received little attention. We investigated the single and interactive effects of temperature and light quality on growth and physiological characteristics of four canola (Brassica napus) cultivars – Clearfield 46A76 (cv1), Clearfield 45H72 (cv2), Roundup Ready 45H24 (cv3) and Roundup Ready 45H21 (cv4). Plants were grown under lower (24°/20 °C) and higher (30°/26 °C) temperature regimes at low red/far‐red (R/FR), normal R/FR and high R/FR light ratios in environment‐controlled growth chambers (16 h light/8 h dark). Higher temperature reduced stem height and diameter; leaf number and area; dry matter of all plant parts; and specific leaf weight, but increased leaf area ratio; and chlorophyll (Chl) fluorescence (Y). Low R/FR increased stem height; Y; and ethylene, but decreased stem diameter; Fv/Fm; Chl a; Chl b; and carotenoids. Among cultivars, plants from cv4 were tallest with thickest stems and greatest dry matter. None of the main factors affected gas exchange. Higher temperature at high R/FR caused cv3 to be shortest, whereas lower temperature at low R/FR caused cv4 to be tallest. We conclude that heat and other stress factors will adversely affect sensitive crops, but tolerant genotypes should perform well under future climate. 相似文献
114.
《Journal of plant nutrition》2013,36(10-11):2009-2021
Abstract A collaborative assay among three laboratories was made in order to compare both the ion (CEN. EN 13368‐2:2001 E. Determination of chelating agents in fertilizers by ion chromatography. Part 2: EDDHA and EDDHMA, 2001a) and the ion‐pair (Lucena, J.J.; Barak, P.; Hernandez‐Apaolaza, L. Isocratic ion‐pair high‐performance liquid chromatographic method for the determination of various iron(III) chelates. J. Chromatogr. A 1996, 727, 253–264) high performance liquid chromatography (HPLC) methods as well as the soluble and complexed Fe (CEN. EN 13366:2001 E. Treatment with a cation exchange resin for the determination of the chelated micronutrient content and of the chelated fraction of micronutrients, 2001b) methods. Fifteen and ten samples of commercial fertilizers of Fe‐EDDHA, Fe‐EDDHMA, respectively were analysed by three laboratories using these methods. No significant differences were observed between the results obtained for the Fe‐EDDHA content using the Lucena et al. or CEN method. The first method makes it possible to distinguish between the meso and DL‐racemic diasteroisomers of Fe‐o, o‐EDDHA. For the Fe‐EDDHMA formulations, the CEN method gives higher values than the ion‐pair method, since in the first one Fe‐EDDH4,6MA coelutes with FeEDDHMA. Also the CEN method does not makes it possible to distinguish between Fe‐EDDHMA and Fe‐EDDH5MA products. The variability among laboratories was larger for the CEN method than for the Lucena et al. method. 相似文献
115.
In Hungary, maize is grown on 1 million ha and occupies more than 20% of the arable land. The rich assortment of maize cultivars of different vegetation periods and different responses to nutritional effects, water supply etc. gives the growers the possibility to choose the cultivars suiting best the site characteristics (Jolânkai et al. 1999). Among the cereals maize has the highest genetical potential. To utilize its yield and quality potential, soil types of high nutrient content and regular nutrient supply are required (Gyõrffy, 1979). Both over‐ and under‐fertilization have an unfavourable effect on the yield and quality of maize (Debreczeni, 1985). Crops can be supplied with the appropriate nutrient amounts only with the knowledge of soil characteristics in the different agro‐ecological regions (nutrient content, water supply, soil compactness, pH, nutrient supplying capacity etc.). In Hungary, a network of long‐term field fertilization trials with uniform fertilizer treatments has been maintained at nine experimental sites representing different agro‐ecological regions of the country. This experimental network gives a basis to test the nutrient responses of our main crops and calibrate their optimal nutrient supply (Kismányoky, 1991). 相似文献
116.
《Journal Of Aquatic Food Product Technology》2013,22(4):63-79
Abstract The shelf-life of Spanish mackerel caught by line fishing in Northern Australian waters was evaluated. Spiked fish were stored in ice either headed and gutted or left uncut and subjected to sensory, nucleotide, pH, histamine and microbial analysts and the rigor pattern recorded. There was little difference between the two product forms. Rigor in uncut fish lasted for 14 ± 9.8 hours and in headed and gutted fish for 19.6 ± 16.3 hours. Spanish mackerel retained good sensory quality for up to 14 days. The bacterial load reached 105 cfu/g by 18 days. K values were low for most of the storage time, < 40%. Histamine levels did not develop more than 10 mg/kg during storage. The pH of Spanish mackerel did not change much even though bacterial levels become high. 相似文献
117.
Nicols Javier Litterio Augusto Matías Lorenzutti María del Pilar Zarazaga Martín Alejandro Himelfarb Manuel Ignacio San Andrs‐Larrea Juan Manuel Serrano‐Rodríguez 《Journal of veterinary pharmacology and therapeutics》2021,44(1):68-78
Cefquinome is a fourth‐generation cephalosporin that is used empirically in goats. Different physiologic factors like pregnancy or lactation could determine the pharmacokinetic behavior of drugs in the organism. The objectives of this study are to (a) compare the pharmacokinetics of cefquinome after intravenous and intramuscular administration in adult nonpregnant (n = 6), pregnant (n = 6), and lactating goats (n = 6), at a dose of 2 mg/kg, with rich sampling by nonlinear mixed‐effects modeling, (b) conduct a pharmacokinetic/pharmacodynamic analysis to evaluate the efficacy of the recommended posology in goats with different physiological states, and (c) determine the optimal posology that achieve a PTA value ≥ 90%, taking into account a T > MIC ≥ 60% of a MIC value ≤ 0.25 µg/ml, in the different subpopulations of goats for both routes. Gestation significantly increased Ka and V1, while reduced F0, Cl, and Q. On the other hand, lactation significantly increased V1 and reduced Tk0. Cefquinome concentrations achieved in placental cotyledon, amniotic fluid, and fetal serum indicate a minimal penetration across the placental barrier. Moreover, milk penetration of cefquinome was minimal. The total body clearance of cefquinome for goats was 0.29 L kg?1 hr?1, that is apparently higher than the reported for cows (0.13 L kg?1 hr?1) and pigs (0.16 L kg?1 hr?1). So, the optimal dose regimen for cefquinome after intravenous and intramuscular administration required higher dose and frequency of administration compared with recommendations for cows or pigs. Therefore, 2 mg kg?1 8 hr?1 and 5 mg kg?1 12 hr?1 could be used for IV and IM routes, respectively, for the treatment of respiratory infections caused by P. multocida and M. haemolytica, but only 5 mg kg?1 12 hr?1 by both routes should be recommended for Escherichia coli infections. 相似文献
118.
Heather K. Knych Carrie J. Finno Russell Baden Rick M. Arthur Daniel S. McKemie 《Journal of veterinary pharmacology and therapeutics》2021,44(1):36-46
The in vivo metabolism and pharmacokinetics of flunixin meglumine and phenylbutazone have been extensively characterized; however, there are no published reports describing the in vitro metabolism, specifically the enzymes responsible for the biotransformation of these compounds in horses. Due to their widespread use and, therefore, increased potential for drug–drug interactions and widespread differences in drug disposition, this study aims to build on the limited current knowledge regarding P450‐mediated metabolism in horses. Drugs were incubated with equine liver microsomes and a panel of recombinant equine P450s. Incubation of phenylbutazone in microsomes generated oxyphenbutazone and gamma‐hydroxy phenylbutazone. Microsomal incubations with flunixin meglumine generated 5‐OH flunixin, with a kinetic profile suggestive of substrate inhibition. In recombinant P450 assays, equine CYP3A97 was the only enzyme capable of generating oxyphenbutazone while several members of the equine CYP3A family and CYP1A1 were capable of catalyzing the biotransformation of flunixin to 5‐OH flunixin. Flunixin meglumine metabolism by CYP1A1 and CYP3A93 showed a profile characteristic of biphasic kinetics, suggesting two substrate binding sites. The current study identifies specific enzymes responsible for the metabolism of two NSAIDs in horses and provides the basis for future study of drug–drug interactions and identification of reasons for varying pharmacokinetics between horses. 相似文献
119.