全文获取类型
收费全文 | 550篇 |
免费 | 46篇 |
专业分类
林业 | 18篇 |
农学 | 43篇 |
基础科学 | 1篇 |
82篇 | |
综合类 | 23篇 |
农作物 | 106篇 |
水产渔业 | 50篇 |
畜牧兽医 | 243篇 |
园艺 | 5篇 |
植物保护 | 25篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 21篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 25篇 |
2017年 | 23篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 30篇 |
2013年 | 41篇 |
2012年 | 48篇 |
2011年 | 48篇 |
2010年 | 29篇 |
2009年 | 31篇 |
2008年 | 36篇 |
2007年 | 40篇 |
2006年 | 36篇 |
2005年 | 25篇 |
2004年 | 21篇 |
2003年 | 23篇 |
2002年 | 12篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1997年 | 1篇 |
排序方式: 共有596条查询结果,搜索用时 265 毫秒
31.
Loss of pendimethalin in runoff and leaching from turfgrass land under simulated rainfall 总被引:2,自引:0,他引:2
A field study was undertaken to investigate runoff and leaching loss of the herbicide pendimethalin in turfgrass land of loamy sand soil. A series of plots constructed in a golf course fairway were surface-applied with pendimethalin SC formulation at the rate of 2. 25 or 4.50 kg a.i./ha and subjected to simulated rainfall at 2.0 cm/day for 10 consecutive days. Runoff losses of pendimethalin were the highest at the first rainfall and then gradually decreased with time. The first runoff event contained pendimethalin in its highest concentration, and in subsequent runoff samples the concentration decreased exponentially. The ranges of pendimethalin concentration were 80.9-18.2 and 177.4-48.6 microgram/L in the standard and double doses, respectively. Total losses by 20 cm of rainfall for 10 days reached 0.81 and 1.22% of the initial deposits at 2.25 and 4.50 kg a. i./ha, respectively. Pendimethalin concentration in the leachate collected at 30-cm soil depth was quite lower than that in the runoff, and the concentration rapidly decreased from 4.3-4.7 to 0. 2-0.4 microgram/L during the 10 days of rainfall treatment. Soil residue analysis at 45 and 90 days after pendimethalin treatment showed that more than 90% of the residue remained at the top 10 cm of soil depth. Low runoff and leaching confirmed that lateral and downward movement of the herbicide should be limited in turf soil. The half-life of pendimethalin under field conditions was 23-30 days and was not affected by application dose and rainfall treatment, but longer persistence was observed under laboratory conditions. Considering low runoff and leaching, as well as relatively short persistence in soil, it is concluded that little environmental carryover of pendimethalin would be expected in turfgrass land. 相似文献
32.
Methylation methods for the quantitative analysis of conjugated linoleic acid (CLA) isomers in various lipid samples 总被引:8,自引:0,他引:8
Park SJ Park CW Kim SJ Kim JK Kim YR Park KA Kim JO Ha YL 《Journal of agricultural and food chemistry》2002,50(5):989-996
Precise methylation methods for various chemical forms of conjugated linoleic acid (CLA), which minimize the formation of t,t isomers and allylmethoxy derivatives (AMD) with the completion of methylation, were developed using a 50 mg lipid sample, 3 mL of 1.0 N H(2)SO(4)/methanol, and/or 3 mL of 20% tetramethylguanidine (TMG)/methanol solution(s). Free CLA (FCLA) was methylated with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). CLA esterified in safflower oil (CLA-SO) was methylated with 20% TMG/methanol (100 degrees C, 5 min), whereas CLA esterified in phospholipid (CLA-PL) was methylated with 20% TMG/methanol (100 degrees C, 10 min), followed by an additional reaction with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). Similarly, CLA esterified in egg yolk lipid (CLA-EYL) was methylated by base hydrolysis, followed by reaction with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). These results suggest that for the quantitative analysis of CLA in lipid samples by GC, proper methylation methods should be chosen on the basis of the chemical forms of CLA in samples. 相似文献
33.
Kim JH Lee JS Song KS Kwon CS Kim YK Kim JS 《Journal of agricultural and food chemistry》2004,52(3):451-455
Induction of cellular phase 2 detoxifying enzymes is associated with cancer preventive potential. Quinone reductase (QR) has been used as a prototype for anticarcinogenic phase 2 enzymes because of its widespread distribution in mammalian systems, large amplitude of inducer response, and ease of measurement in murine hepatoma cells. Methanol extract of Polyozellus multiplex, which shows a strong QR induction potential, was subjected to bioassay-guided fractionation, and polyozellin (PM1) appeared to be a major active component. In in vitro cultured cells (hepa1c1c7 and BPRc1 cells), polyozellin enhanced QR, glutathione S-transferase (GST) activities, and glutathione (GSH) content in a dose-dependent manner. The compound also significantly promoted differentiation of HL-60 human promyelocytic emia cells. In conclusion, polyozellin deserves further in vivo study to evaluate its potential as a cancer preventive agent. 相似文献
34.
35.
Choi US Jeong SM Kang MS Jung IS Kim DY Lee CW 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2004,33(1):47-49
Abstract: An 18-month-old male Doberman Pinscher was referred to the Veterinary Medical Teaching Hospital of the College of Veterinary Medicine for an erythemic nodular mass on the right forelimb. The mass was diagnosed as cutaneous lymphoma, based on cytologic examination of a mass aspirate and histopathology. Using immunohistochemistry the neoplastic cells were positive for CD3 but negative for CD79a, E-cadherin, and pancytokeratin, confirming their origin as T lymphocytes. No tumor recurrence was noted 18 months after surgery. To our knowledge, this is the first report of a solitary nodular form of cutaneous lymphoma in a young dog. 相似文献
36.
Isolation and characterization of a new compound from Prunus mume fruit that inhibits cancer cells 总被引:1,自引:0,他引:1
An active compound that inhibits cancer cells was isolated from the fruit of Prunus mume, and its structure and in vitro activities were characterized. The n-hexane fraction obtained from methanol extracts exhibited the strongest inhibitory effect on the growth of cancer cells. From the n-hexane fraction, a new compound named B-1 was purified through preparative thin-layer chromatography, ODS column chromatography, and reverse phase high-performance liquid chromatography and its structure was analyzed by fast atom bombardment mass spectrometry and 1H and 13C NMR. The molecular formula of B-1 was C19H22O6 {2-hydroxy-1-[(7-hydroxy-2-oxo-2H-chromen-6-yl)methyl]-2-methylpropyl-(2Z)-3-methyl-but-e-enoate:prunate}, and the IC50 value was in the range of 39-58 microg/mL in descending order of the cancer cell lines Hep-2, SW-156, HEC-1-B, and SK-OV-3. B-1 exhibited 81-96% inhibition at a concentration level of 100 microg/mL against all cells, based on an 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. However, B-1 showed little effect against normal cells with only 23% or less growth inhibition at 100 microg/mL. Thus, B-1 has a highly specific inhibitory effect against cancer cells but little effect against normal cells. When the cancer cell lines Hep-2 and SK-OV-3 were incubated with B-1 for 72 h, most of the tested cells suffered strong growth inhibition. The compound has the potential to be developed as a nutraceutical. 相似文献
37.
Hong YJ Tomas-Barberan FA Kader AA Mitchell AE 《Journal of agricultural and food chemistry》2006,54(6):2405-2411
The fruits of the date palm (Phoenix dactylifera) are consumed throughout the world and are an important part of the diet in the Middle East. Dates at the rutab and tamar maturity and ripening stages contain a wide array of phenolic antioxidants, but little is known about the composition of phenolic compounds in dates at the khalal stage of ripening. In the current study, the flavonoid glycoside and procyanidin compositions of dates of the cultivar Deglet Noor harvested at the khalal stage of maturity were characterized using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI/MS/MS). Procyanidin oligomers through decamers were identified in extracts of these dates. Higher molecular weight polymers, undecamers through heptadecamers, were also apparent from mass spectra. Thirteen flavonoid glycosides of luteolin, quercetin, and apigenin, 19 when considering isomeric forms, were also identified. Mass spectra indicate that both methylated and sulfated forms of luteolin and quercetin are present as mono-, di-, and triglycosylated conjugates whereas apigenin is present as only the diglycoside. LC-ESI/MS/MS spectra indicate that quercetin and luteolin formed primarily O-glycosidic linkages whereas apigenin is present as the C-glycoside. 相似文献
38.
Koyanagi Y Sawada K Sakata-Haga H Jeong YG Fukui Y 《Anatomia, histologia, embryologia》2006,35(6):387-392
Rolling Mouse Nagoya (RMN) carries a mutation in a gene encoding for alpha(1A) subunit of P/Q-type Ca(2+) channel (Ca(v)2.1). In addition to ataxia, this mutant mouse exhibits abnormal hindlimb extension, which is characterized by a sustained excessive tone of hindlimb extensor muscles. This study aimed to clarify whether serotonergic (5-HTergic) innervation of the spinal motoneurons was altered in RMN in relation to the abnormal hindlimb extension. The density of 5-HT immunoreactive fibres in the ventral horn of lumbar and sacral regions of spinal cord was significantly greater in RMN than in controls. Retrograde wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) labelling combined with 5-HT immunostaining revealed that the number of 5-HT immunoreactive terminals adjoining femoris quadriceps motoneurons was about 2.5-fold greater in RMN than in controls. Furthermore, 5-HT immunostaining in the lumbar cord ventral horn was examined in three other Ca(v)2.1 mutant mice (tottering, leaner and pogo) as to whether or not they showed the abnormal hindlimb extension. Among these mutants, the increased density of 5-HT immunoreactive fibres was observed in correlation with the presence of the abnormal hindlimb extension. The results suggest an increased 5-HTergic innervation of the lumbosacral motoneurons in correlation with the abnormal hindlimb extension in RMN and other Ca(v)2.1 mutant mice. As 5-HT is known to induce the sustained membrane depolarizations without continuous excitatory synaptic inputs (plateau potentials) in spinal motoneurons, the increased 5-HTergic innervation may cause the sustained excitation of hindlimb extensor motoneurons, resulting in the abnormal hindlimb extension. 相似文献
39.
Yi NY Park SA Jeong MB Kim MS Lim JH Nam TC Seo K 《Journal of the American Animal Hospital Association》2006,42(6):435-439
The medical records of 23 dogs that underwent medial canthoplasty for treatment of epiphora were reviewed. The most prevalent breed encountered was the shih tzu. Other affected breeds included the Pekingese, Maltese, toy poodle, and pug. All dogs had epiphora associated with medial canthal trichiasis and/or entropion. Other ocular abnormalities included conjunctivitis, keratitis, pigmentary keratitis, corneal ulceration, globe prolapse, and nasal fold trichiasis. After medial canthoplasty, the epiphora resolved in all dogs. 相似文献
40.
Jung DI Park C Kang BT Kim JW Kim HJ Lim CY Jeong SW Park HM 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2006,68(11):1235-1238
A 15-year-old female maltese was referred to us because of a 3-month history of ataxia, circling, and acute blindness. A mass was noted in the brainstem on brain magnetic resonance images. A cerebellar herniation was also detected on T1-weighted sagittal images. The lateral, third and fourth ventricles and central canal of the cervical spinal cord were enlarged. Based on diagnostic imaging findings, cervical syringomyelia secondary to a brainstem tumor was suspected. The clinical signs were controlled well by lomustine and the dog survived for 8 months after the initial diagnosis. The mass was diagnosed as a meningioma based on histopathological findings. This report describes the clinical findings and imaging characteristics of an acquired syringomyelia resulting from a brainstem meningioma. 相似文献