首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   159篇
  免费   9篇
林业   10篇
农学   9篇
  17篇
综合类   9篇
农作物   7篇
水产渔业   5篇
畜牧兽医   94篇
植物保护   17篇
  2023年   1篇
  2022年   4篇
  2021年   6篇
  2020年   4篇
  2019年   2篇
  2018年   1篇
  2017年   7篇
  2016年   12篇
  2015年   7篇
  2014年   9篇
  2013年   15篇
  2012年   7篇
  2011年   8篇
  2010年   6篇
  2009年   4篇
  2008年   14篇
  2007年   5篇
  2006年   9篇
  2005年   12篇
  2004年   7篇
  2003年   7篇
  2002年   4篇
  2001年   1篇
  2000年   4篇
  1999年   1篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1992年   1篇
  1991年   1篇
  1987年   2篇
  1982年   1篇
  1975年   1篇
排序方式: 共有168条查询结果,搜索用时 15 毫秒
31.
A subchronic feeding study of l-serine (l-Ser) was conducted with groups of 10 male and 10 female Fischer 344 rats fed a powder diet containing 0, 0.06, 0.5, 1.5 or 5.0% concentrations of l-Ser for 90 days. There were no toxicologically significant, treatment-related changes with regards to body weight, food intake, water intake or urinalysis data. In several of the hematology, serum biochemistry and organ weight parameters, significant changes were observed between some of the treated groups and the controls. All these changes, however, were subtle and lacked any corresponding pathological findings. In addition, the increased or decreased values remained within the range of the historical control values. In fact, histopathological assessment revealed only sporadic and/or spontaneous lesions. In conclusion, the no-observed-adverse-effect-level (NOAEL) for l-Ser was, therefore, determined to be at least a dietary dose of 5.0% (2765.0 mg/kg body weight/day for males and 2905.1 mg/kg body weight/day for females) under the present experimental conditions.  相似文献   
32.
The aim of the present study was to provide a method for evaluating bone toxicity induced by drugs in various bones in aged rats. Male Crl:CD (SD) rats at 46 weeks of age were administered 15 mg/m(2) body surface area of doxorubicin, which effects the growth plate in weanling rats, weekly for 9 weeks by intravenous injection, and the femur, sternum, humerus and tibia were examined histopathologically. In the doxorubicin-treated group, thinning of the growth plate was remarkably observed in the proximal tibia and humerus; however, these changes were not observed in other regions. In addition, the osteoclast number per bone perimeter in the proximal tibia was significantly higher than others in control aged rat. Thus, recognizing the various histological reactions related to the time of epiphyseal closure is important for evaluating bone toxicity in aged rats.  相似文献   
33.
Despite the immense socio-economic repercussions of African trypanosomosis (AT), there is currently no effective control measure against the disease. Characterization of mechanisms governing resistance and/or susceptibility to AT could suggest interventions that might lead to more effective disease control. The present study was designed in an attempt to address the possible role of CD4+CD25+ T cells during an acute lethal infection of mice with Trypanosoma congolense, the causative agent of AT in domestic animals, through selective depletion using anti-CD25 monoclonal antibody. Accordingly, CD4+CD25+ T-cell-depletion resulted in a significant reduction or delay in parasitemia, pathology, and mortality, as compared to controls. The apparent resistance in CD4+CD25+-T-cell-depleted mice correlated with a profound suppression of Th2 cytokines in vitro and in vivo, culminating in a net Th1 cytokine environment. Cumulatively, these findings suggest that CD4+CD25+ T-cell- depletion improves the trypanotolerance of highly susceptible BALB/c mice acutely infected with the lethal T. congolense.  相似文献   
34.
35.
We investigated the optimal timing of artificial insemination (AI) for achieving pregnancy according to the onset/end of estrus detected by an accelerometer system in Holstein cattle. The conception rates of conventional semen were used as a reference. The conception rate from AI of sex-sorted semen was higher at −4 to 4 h (57.1%) from the end of estrus than those at −12 to −4 h (37.7%) and 12–20 h (30.3%), whereas AI at 4–12 h showed an intermediate conception rate (47.4%). Conversely, conception rates were similar in AI performed between 0 and 32 h from the onset of estrus. Regarding conventional semen, the interval from the onset and end of estrus did not affect conception rates. The present results suggest that the time of the end of estrus is the better indicator of optimal AI timing for sex-sorted semen than the onset of estrus.  相似文献   
36.
The prevalence of Dirofilaria immitis in free-ranging raccoon dogs (Nyctereutes procyonoides viverrinus) was examined in the southeast region of Kanagawa Prefecture, Japan, using a rapid immunomigration (RIM) test kit. Between April 2007 and March 2010, we examined 108 raccoon dogs rescued and housed by the Kanazawa Zoological Garden. D. immitis infection was found in 8 (7.4%) raccoon dogs. This is the first report to reveal the prevalence of D. immitis infection in living raccoon dogs. The prevalence of the infection was lower than previously reported values obtained on postmortem examination. One reason might be that the present study included young raccoon dogs infected with immature worms. Significant high-risk areas of D. immitis infection in the raccoon dogs were not observed.  相似文献   
37.
For the identification of herds with cattle persistently infected (PI) with bovine viral diarrhea virus, 1,272 animals from 20 herds were subjected to serum neutralizing (SN) test using the Nose strain and virus isolation. Eighteen PI cattle were detected from 5 herds. On the phylogenetic tree based on the nucleotide sequences of the 5' untranslated region, the isolates from the PI cattle were classified into genotypes-1a or -1b. Of 3 unvaccinated calves aged 6 to 12 months selected from each herd, the probabilities of obtaining 2 or more non-PI cattle with SN antibody titers of 64 or more (P(SN)), one or more PI cattle (P(VI)), and either of the conditions (P(Total)) were calculated using the hypergeometric probability model. P(Total) for the 5 herds with PI cattle was 1.000. P(SN) for 3 herds with many PI cattle within the selected age group was as low as 0.500 or less, and P(VI) was as high as 0.886 or more. P(SN) in the 2 other herds with few PI cattle was 1.000, and P(VI) was as low as 0.375 or less. P(Total) in 13 of 15 herds without PI cattle was 0.000, and was 0.714 or 0.774 for the 2 other herds. These results suggest that herds with PI cattle can be predicted with high accuracy when both SN test and virus isolation are performed on only 3 unvaccinated calves aged 6 to 12 months selected from a herd.  相似文献   
38.
To evaluate the phenolic extracts of Chinese quince, quince, and apple fruits, their phenolic profiles, antioxidant properties, and anti-influenza viral activities were investigated. Chinese quince had the largest amount of phenolics consisting mainly of high polymeric procyanidins. Quince had considerable amounts of hydroxycinnamic derivatives mainly composed of 3-caffeoylquinic acid and 5-caffeoylquinic acid and polymeric procyanidins. Apple (cv. Fuji) had the lowest amount of phenolics, mainly 5-caffeoylquinic acid and monomeric and oligomeric procyanidins. The antioxidant functions of Chinese quince and quince phenolic extracts were superior to that of chlorogenic acid standard or ascorbic acid evaluated in both the linoleic acid peroxidation system and the DPPH radical scavenging system. However, those extracts were less effective than apple phenolics or (-)-epicatechin in linoleic acid peroxidation system. On the other hand, Chinese quince phenolics showed the strongest anti-influenza viral activity on the hemagglutination inhibition test.  相似文献   
39.
Curcuminoids are substances of great interest because of their important pharmacological activities, particularly anti-inflammatory, anticarcinogenic, and anti-Alzheimer's activities. In this study, we report the first procedure and effect of processing for the high, efficient, and useful purification of curcumin, demethoxycurcumin, and bisdemethoxycurcumin from turmeric powder. Purification involves high-speed countercurrent chromatographic (HSCCC) separation of these curcuminoids using a simple two-phase solvent system composed of n-hexane/chloroform/methanol/water (5/10/7.5/2.5, v/v). The HSCCC-fractionated effluent peaks indicated that the peak resolutions were 1.7 between curcumin and demethoxycurcumin and 2.1 between demethoxycurcumin and bisdemethoxycurcumin for 25 mg of loaded turmeric powder. These purified substances were analyzed by liquid chromatography-tandem mass spectrometry with scan and daughter scan negative modes, and the wide absorbance from 200 to 500 nm was monitored by photodiode array detection. The separation yielded 1.1 mg of curcumin, 0.6 mg of demethoxycurcumin, and 0.9 mg of bisdemethoxycurcumin (>98% purity). Moreover, the antioxidant effect of curcuminoids was measured by a 1,1-diphenyl-2-picrylhydrazil assay. The order of antioxidant activity was purified curcumin > purified demethoxycurcumin > purified bisdemethoxycurcumin > turmeric powder. Curcumin, demethoxycurcumin, and bisdemethoxycurcumin can be used for various evaluations of their pharmacological activities.  相似文献   
40.
Abstract

The humus composition was analyzed and the humic acid characterized by UV and visible absorption spectroscopy in order to investigate the rotting and maturing process of city refuse compost according to the method of Kumada et al. During the composting process, the following findings were obtained: (1) the HT value was almost constant, but the HE/HT ratio varied somewhat, (2) HA increased with decrease in FA, and the PQ value so increased clearly, (3) the shoulder-like absorption at a wavelength near 270 nm weakened, and (4) the RF value of humic acid increased, whereas the Δ log K value seldom varied.

The IR spectrum of humic acid gradually changed as follows: (1) the absorption band in the 1700-1600 cm-1 region and in the 1550-1500 cm-1 region increased slightly, (2) the band in the 1100-1000 cm-1 region decreased, and (3) the bands at 835 and 710 cm-1 com pletely disappeared. On the whole, the shape of the IR spectrum of the city refuse compost became featureless. These changes were probably due to the oxidation which occurred in the composting process.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号