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71.
A multiresidue method analyzing 209 pesticides in 24 agricultural commodities has been developed and validated using the original Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure and high performance liquid chromatography-positive electrospray ionization-tandem mass spectrometry (LC-MS/MS) analysis. Using solvent-only calibration standards (SOCSs) and matrix-matched calibration standards (MMCSs), it was demonstrated that a minimal concentration of 5-10 μg/kg (part per billion, ppb) of analytes in matrix is required for the consistent identification of targeted pesticides with two MRM transitions. Method performance was validated by the precision and accuracy results obtained from fortification studies at 10, 25, 100, and 500 ppb and MMCSs. The method was demonstrated to achieve an average recovery of 100 ± 20% (n = 4) for >75% of evaluated pesticides at the low fortification level (10 ppb) and improved to >84% at the higher fortification concentrations in all 24 matrices. Matrix effects in LC-MS/MS analysis were studied by evaluating the slope ratios of calibration curves (1.0-100 ng/mL) obtained from the SOCSs and MMCSs. Principal component analysis (PCA) of LC-MS/MS and method validation data confirmed that each matrix exerts its specific effect during the sample preparation and LC-MS/MS analysis. The matrix effect is primarily dependent on the matrix type, pesticide type and concentration. Some caution is warranted when using matrix matched calibration curves for the quantitation of pesticides to alleviate concerns on matrix effects. The QuEChERS method with LC-MS/MS was used to identify and quantitate pesticides residues, with concentrations ranging from 2.5 to >1000 ppb in a variety of agricultural samples, demonstrating fitness for screening and surveillance applications.  相似文献   
72.
The dissipation behavior and degradation kinetics of azoxystrobin, carbendazim, and difenoconazole in pomegranate are reported. Twenty fruits/hectare (5 kg) were collected at random, ensuring sample-to-sample relative standard deviation (RSD) within 20-25%. Each fruit was cut into eight equal portions, and two diagonal pieces per fruit were drawn and combined to constitute the laboratory sample, resulting in RSDs <6% (n = 6). Crushed sample (15 g) was extracted with 10 mL of ethyl acetate (+ 10 g Na(2)SO(4)), cleaned by dispersive solid phase extraction on primary secondary amine (25 mg) and C(18) (25 mg), and measured by liquid chromatography tandem mass spectrometry. The limit of quantification was ≤0.0025 μg g(-1) for all the three fungicides, with calibration linearity in the concentration range of 0.001-0.025 μg mL(-1) (r(2) ≥ 0.999). The recoveries of each chemical were 75-110% at 0.0025, 0.005, and 0.010 μg g(-1) with intralaboratory Horwitz ratio <0.32 at 0.0025 μg g(-1). Variable matrix effects were recorded in different fruit parts viz rind, albedo, membrane, and arils, which could be correlated to their biochemical constituents as evidenced from accurate mass measurements on a Q-ToF LC-MS. The residues of carbendazim and difenoconazole were confined within the outer rind of pomegranate; however, azoxystrobin penetrated into the inner fruit parts. The dissipation of azoxystrobin, carbendazim, and difenoconazole followed first + first order kinetics at both standard and double doses, with preharvest intervals being 9, 60, and 26 days at standard dose. At double dose, the preharvest intervals extended to 20.5, 100, and 60 days, respectively.  相似文献   
73.
本文评估了沙棘叶水提物在大白鼠体内的适应原活性和毒性.提取物的剂量依赖性适应原活性的研究采取将小鼠置于低温(5℃),低压(428mmHg),抑制(C-H-R)的环境下的30min前口服不同剂量的沙棘叶水提物.在亚急性毒性中,连续14d每天口服10倍和20倍最大有效剂量(每天口服1g/kg体重和2g/kg体重)和连续30...  相似文献   
74.
A microbiological and fluorometric test for the determination of minute amounts of alloxan has been described. The test involves the conversion of the alloxan to riboflavin which is measured by microbiological or fluorometric techniques.  相似文献   
75.
Periphyton grown on substrates is known to improve water quality in aquaculture ponds. Five different substrates, (i) bamboo pipe (ii) plastic sheet (iii) polyvinylchloride (PVC) pipe (iv) fibrous scrubber, and, (v) ceramic tile were evaluated for the formation of biofilm in this experiment. The substrates were suspended 25 cm below the water surface. Each type of substrate was collected fortnightly to analyze the abundance and biomass of different periphytic algae and of the biofouling organism. The study was terminated after 60 days due to severe fouling by polychaete. Results showed that pond water nutrients were high on day 60 with mean total ammonia-N, nitrite-N and soluble reactive phosphorus concentrations of 309.6 ± 8.6 μg L− 1, 26.0 ± 2.7 μg L− 1 and 87.2 ± 7.1 μg L− 1 respectively. During the first two weeks the substrates were colonized by 19 periphytic algae. The most abundant family was Bacillariophyta (8 genera) followed by Chlorophyta (7 genera) and Cyanophyta (4 genera). Periphyton colonization on bamboo pipe showed the highest (p < 0.05) biomass in terms of chlorophyll a amongst all the substrates used. The biomass varied from 179 to 1137 μg m− 2 with mean values of 1137.2 ± 0.6, 929.6 ± 0.6, 684.2 ± 1.2, 179.1 ± 0.6 and 657.0 ± 0.6 μg m− 2 on bamboo pipe, PVC pipe, plastic sheet, fibrous scrubber and ceramic tile respectively for the first 15 days. From 3rd week, polychaetes began to form tubes on the substrate. By day 60, the whole surface of all substrates was covered with tightly packed polychaete tubes with mean densities of 168.0 ± 15.4, 121.0 ± 13.5, 72.8 ± 9.8, 72.4 ± 7.4 and 56.0 ± 6.8 polychaete tubes cm− 2 for bamboo, PVC, plastic, fibrous scrubber and ceramic tile respectively. This study illustrated the invasive nature of attached polychaete thus hampering the formation of periphyton biofilm on substrates which could have been used for improving water quality in enriched brackishwater shrimp ponds.  相似文献   
76.
This work aims to manufacture cotton yarns with requisite quality by choice of suitable raw materials for a given spinning system. To fulfill this aim, a hybrid model based on Artificial Neural Network (ANN) and Genetic Algorithm (GA) has been developed which captures both the high prediction power of ANN and global solution searching ability of GA. In an attempt to achieve a yarn having predefined tenacity and evenness, a constrained optimization problem is formulated with the ANN input-output relation between fibre and yarn properties. GA has been used to solve the optimization problem by searching the best combination of fibre properties that can translate into reality a yarn with the desired quality. The model is capable in identifying the set of fibre properties that gives requisite yarn quality with reasonable degree of accuracy.  相似文献   
77.
Journal of Crop Science and Biotechnology - Genomic selection (GS) is a popular breeding method that uses genome-wide markers to predict plant phenotypes. Empirical studies and simulations have...  相似文献   
78.
Field experiments were conducted with mustard (Brassica campestris cv. B9) consecutively for three years (2005, 2006 and 2007) in the Crop Research and Seed Multiplication Farm of Burdwan University, Burdwan, West Bengal, India. In the first year, varietal screening of mustard under recommended dose of chemical fertilizer (100:50:50) were performed with seven mustard varieties during November 2005 to February 2006. In the second year, two experiments were conducted to study the effects of six different combined doses of chemical fertilizer and biofertilizer and six different levels of growth retardant cycocel. In the third year, six different levels of compost along with the best screened dose of growth retardant (CCC-300 ppm) and the best combined dose of biofertilizer and chemical fertilizer (3/4thchemical fertilizer:1/4th biofertilizer) from the previous year were applied to study the effects on agronomic traits and growth attributes of mustard, and the field data were analyzed statistically. The variety B9 recorded a significant higher seed yield along with other yield contributing factors, which was found to be superior to other varieties under old alluvial soil of Burdwan, West Bengal, India, in 2005. In 2006 and 2007, seed yield was found to be the best for CCC-300 ppm treatment and the best combined dose of biofertilizer and chemical fertilizer was found to be 3/4th chemical fertilizer:1/4th biofertilizer. In 2007, the best yield was given by the treatment of 7.5 t·hm?2 compost along with the best dose of growth retardant cycocel and the best combined dose of biofertilizer and chemical fertilizer.  相似文献   
79.
The bioassay guided fractionation of the n-hexane extract of the seeds of Murraya koenigii Spreng (Rutaceae) resulted in the isolation of three bioactive carbazole alkaloids, kurryam (I), koenimbine (II) and koenine (III). The structures of the compounds were confirmed from their 1H-, 13C-, and 2D-NMR spectral data. Of the three compounds (I) and (II) exhibited significant inhibitory activity against castor oil-induced diarrhoea and PGE2-induced enteropooling in rats. The compounds also produced a significant reduction in gastrointestinal motility in the charcoal meal test in Wister rats.  相似文献   
80.
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