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1.
In late November 1991, 1883 clinics in Canada were sent a questionnaire to assess the status of Dirofilaria immitis in dogs in 1991 and there was a 60.0% response. There were 344,031 dogs tested for heart-worm (HW), 627 were found infected and the prevalence of HW infection was 0.18%. There were 417 dogs with HW in Ontario, 116 in Manitoba, 38 in Quebec, 53 in British Columbia, three in Alberta, and one in Nova Scotia. In British Columbia, all of the infected dogs but one were from the Okanagan valley which, as from 1991, is a new focus of infection in Canada. Most dogs with HW had not been on preventive medication in 1990, and the prevalence among dogs tested and unprotected was 0.59%. That prevalence was considerably higher in endemic areas. Companion dogs, over three years of age and maintained primarily outdoors in rural areas, were most frequently infected. One cat was diagnosed with D. immitis and 33 dogs had Dipetalonema reconditium.  相似文献   
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Trace minerals feeding had significant effects on sperm production and fertility with better absorption and proper utilization within the body for optimum reproductive function. Several studies have shown that more influenced trace elements in the diets of animals are copper (Cu) and zinc (Zn). Bucks showing deficiency of this mineral might affect the quality of semen production which in turn would affect the fertility. This experiment was thus designed to test the effects of organic Cu and Zn supplementation on antioxidants enzyme activities and sperm functional attributes in fresh semen of bucks. Forty bucks (n = 40, Aged 5 months) were assigned to ten groups of four animals in each group, supplemented (for a period of 8 months) with different levels of organic Zn: 20 mg (T2), 40 mg (T3) and 60 mg (T4), organic Cu: 12.5 mg (T5), 25 mg (T6), 37.5 mg (T7) and combined organic Zn and Cu: 20 + 12.5 mg (T8), 40 + 25 mg (T9), 60 + 37.5 mg (T10), respectively, per kg dry matter and no additional mineral diet (control; T1). One hundred and sixty semen samples were collected through electro‐ejaculator and analysed for sperm quantity, quality, acrosome intactness and plasma membrane integrity and correlated with the catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase enzyme activities in seminal plasma. The results indicated organic Cu and zinc supplemented bucks produced more sperm cells, had higher sperm concentrations, maintained higher (< .01) sperm livability, plasma membrane and acrosome integrities, more motility and velocity. The increased antioxidant enzyme activities, reduced oxidative stress and lowered lipid peroxidation were positively correlated (< .05) with the sperm functional attributes. In conclusion, organic Cu and Zn supplement to male goats showed protective roles against oxidative damage and maintained better fresh semen characteristics.  相似文献   
3.
Two different deworming strategies based on the use of moxidectin, a broad spectrum endectocide with persistency against Ostertagia ostertagi, were evaluated in grazing dairy heifers. Eighty-four heifers unexposed to parasitic infection were randomly allocated to 3 different groups: untreated (Group 1), treated at 3 and 10 weeks after turnout with 0.5 mg/kg/body weight (BW) of topical moxidectin (Group 2), or treated at turnout and 10 weeks later with 0.5 mg/kg/BW of topical moxidectin (Group 3). The heifers were turned out on June 6 (Day 0) to a naturally contaminated pasture divided into 3 sections by an electrical fence. Each group of heifers was put on a different section of pasture. The trial ended when they were housed on October 29 (Day 143). The results of this experiment confirmed the beneficial effect of 2 strategic treatments with moxidectin pour-on under field conditions in Quebec. The parasitological parameters showed a statistical difference in terms of mean fecal egg counts between treated and control groups (ANOVA, P < or = 0.006). After turnout, pasture larval counts were consistently higher for Group 1 compared with counts for Group 2 or 3. All heifer groups gained weight during the trial period, but the weight gain profile of both treated groups was significantly higher than that of the untreated controls (ANOVA, P < 0.03). During the trial period, Group 2 and Group 3 gained 77.7 kg BW and 73.2 kg BW, respectively, while Group 1 gained only 57.9 kg BW, despite the fact that heifers of Group 1 received a greater quantity of supplementary feed while on pasture.  相似文献   
4.
Neospora caninum is a protozoan that causes abortion in cattle. The dog has recently been identified as a definitive host for N. caninum. To verify if bovine fetuses can infect dogs, nine 2-4-month-old dogs were fed bovine fetuses naturally infected by N. caninum. None of the dogs excreted oocysts, seroconverted, had clinical signs or lesions compatible with N. caninum infection. Additional studies will be necessary to determine the natural mode of infection of dogs by N. caninum.  相似文献   
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Monensin, a polyether ionophore antibiotic, is potentially an important agent for bloat relief in dairy cows grazing temperate legume-based pasture. A series of studies was undertaken to determine the effect of monensin, when delivered continuously in the rumen of lactating dairy cows by means of controlled-release capsules (monensin CRC). Such devices release approximately 300 mg/head/day for 100 d. A short-term pilot study made at Ruakura, New Zealand, tested monensin CRC in cows selected for high susceptibility to bloat and grazing lucerne (Medicago sativa) or red clover (Trifolium pratense). Treatment significantly reduced the incidence of bloat, while milk yield and protein yield were increased. There was no effect on fat yield. Following the pilot study, 6 large-scale field experiments involving a total of 368 lactating dairy cows, were made in Australia and New Zealand to confirm the effectiveness of monensin CRC for bloat control and to measure the effect of such treatment on milk production and composition. A severe bloat problem occurred in 2 experiments, mild bloat occurred in 2 others, while no visual signs of bloat were observed in the remaining 2 experiments. Bloat was significantly (P less than 0.05) reduced by monensin CRC treatment when data was pooled over the 4 experiments in which bloat occurred. Daily milk yield was increased in all experiments from a mean of 17.7 in untreated groups to 18.8 kg/head/day (P less than 0.05) in monensin CRC-treated cows. Protein percentage was not affected by treatment, while there was a decrease from 4.29 to 4.10% fat, although total fat yield was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
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Most organisms rely on interhomolog crossovers (COs) to ensure proper meiotic chromosome segregation but make few COs per chromosome pair. By monitoring repair events at a defined double-strand break (DSB) site during Caenorhabditis elegans meiosis, we reveal mechanisms that ensure formation of the obligate CO while limiting CO number. We find that CO is the preferred DSB repair outcome in the absence of inhibitory effects of other (nascent) recombination events. Thus, a single DSB per chromosome pair is largely sufficient to ensure CO formation. Further, we show that access to the homolog as a repair template is regulated, shutting down simultaneously for both CO and noncrossover (NCO) pathways. We propose that regulation of interhomolog access limits CO number and contributes to CO interference.  相似文献   
10.
Conical intersections play a crucial role in the chemistry of most polyatomic molecules, ranging from the simplest bimolecular reactions to the photostability of DNA. The real-time study of the associated electronic dynamics poses a major challenge to the latest techniques of ultrafast measurement. We show that high-harmonic spectroscopy reveals oscillations in the electronic character that occur in nitrogen dioxide when a photoexcited wave packet crosses a conical intersection. At longer delays, we observe the onset of statistical dissociation dynamics. The present results demonstrate that high-harmonic spectroscopy could become a powerful tool to highlight electronic dynamics occurring along nonadiabatic chemical reaction pathways.  相似文献   
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