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   417篇
  免费   18篇
林业   9篇
农学   33篇
  60篇
综合类   29篇
农作物   26篇
水产渔业   27篇
畜牧兽医   242篇
植物保护   9篇
  2023年   3篇
  2022年   3篇
  2021年   5篇
  2019年   4篇
  2018年   4篇
  2017年   10篇
  2016年   3篇
  2015年   10篇
  2014年   9篇
  2013年   18篇
  2012年   29篇
  2011年   22篇
  2010年   16篇
  2009年   19篇
  2008年   30篇
  2007年   21篇
  2006年   15篇
  2005年   17篇
  2004年   17篇
  2003年   14篇
  2002年   18篇
  2001年   14篇
  2000年   10篇
  1999年   13篇
  1998年   2篇
  1996年   2篇
  1994年   3篇
  1993年   7篇
  1992年   5篇
  1991年   8篇
  1990年   10篇
  1989年   6篇
  1988年   7篇
  1987年   5篇
  1986年   8篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1981年   3篇
  1979年   2篇
  1978年   4篇
  1975年   4篇
  1974年   2篇
  1973年   5篇
  1972年   4篇
  1968年   2篇
  1967年   2篇
  1966年   2篇
  1936年   2篇
  1925年   1篇
排序方式: 共有435条查询结果,搜索用时 247 毫秒
101.
HJ Lee  JY Cho  JH Moon 《Fitoterapia》2012,83(7):1196-1204
Salvianolic acid B (Sal B) is the most abundant phenolic compound in Salvia miltiorrhiza, which has been widely used for the treatment of cardiovascular diseases in Oriental medicine. To elucidate structure of the converted compounds of Sal B by decoction in aqueous solution, Sal B (200mg) was decocted in an aqueous solution (200mL) at pH 4.9 and the decocted solution was purified by Sephadex LH-20 column chromatography and preparative HPLC. The 13 converted compounds were isolated and the chemical structures were determined by NMR and MS. In addition to the 4 compounds previously reported as conversion products of Sal B by decoction, 9 compounds were first reported with the complete structure of compounds isolated from decocted Sal B solution and three of the compounds were determined to be novel compounds. In addition, a conversion mechanism of compounds converted by decoction was proposed on the basis of kinetics studies, which reasonably supported the conversion mechanism of Sal B. The 13 compounds seemed to be produced by the hydrolysis of an ester bond, decarboxylation, retro oxa-Michael reaction, hydration, and radical reaction during decoction in aqueous solution.  相似文献   
102.
Object recognition memory and contextual fear conditioning task performance in adult C57BL/6 mice exposed to cranial fast neutron irradiation (0.8 Gy) were examined to evaluate hippocampus-related behavioral dysfunction following acute exposure to relatively low doses of fast neutrons. In addition, hippocampal neurogenesis changes in adult murine brain after cranial irradiation were analyzed using the neurogenesis immunohistochemical markers Ki-67 and doublecortin (DCX). In the object recognition memory test and contextual fear conditioning, mice trained 1 and 7 days after irradiation displayed significant memory deficits compared to the sham-irradiated controls. The number of Ki-67- and DCX-positive cells decreased significantly 24 h post-irradiation. These results indicate that acute exposure of the adult mouse brain to a relatively low dose of fast neutrons interrupts hippocampal functions, including learning and memory, possibly by inhibiting neurogenesis.  相似文献   
103.
This study was conducted to investigate effects of fermented mushroom (Flammulina velutipes) by‐product diets on the growth performance and carcass traits in growing‐fattening Berkshire pigs. The fermented diets mainly contained 40.0% mushroom by‐product, 20.0% formula feed, 26.0% rice bran and supplemental 0.1% probiotics. The mixed ingredients were fermented for 5 days at room temperature. Berkshire pigs (n = 225) were divided into five groups and three replications. The basal diets (C) were substituted by 10% (T1), 30% (T2), 50% (T3) and 70% (T4) fermented mushroom by‐product diets. Crude protein concentration and total calorie in fermented diets were significantly increased (P < 0.05) at the end of fermentation days compared with initial fermentation day. Body weight gain, feed efficiency and carcass weight were significantly lower (P < 0.05) in the T2, T3 and T4 groups than in the control group. Carcass grade was significantly better (P < 0.05) in the pigs fed fermented diets than in the pigs fed control diet and the ratio of high grade (1 plus 2 grades) was higher in the fermented diet groups compared with the control group. Therefore, although a diet of fermented mushroom by‐product decreased growth performance and feed efficiency, it improved the carcass grade in Berkshire pigs.  相似文献   
104.
The spatial distribution of chewing lice (Bovicola ovis) on their hosts was examined in Polypay and Columbia ewes initially artificially infested on the midside or the neck. Densities of lice were determined at 69 body sites in eight body regions at approximately monthly intervals for 2 years. In the second year, half of the ewes were mated and lice were counted at 26 body sites on the resulting lambs. Polypay ewes had higher densities of lice than Columbias at most inspections but there was little effect of infestation point or mating on either numbers or the distribution of lice. During periods of high louse numbers densities were generally greatest on the sides or the back. Densities on the head were also high at times and peaked later than overall louse densities. Shearing markedly reduced density but increased the proportion of lice found on the neck, belly and lowleg sites. The distribution of lice on the lambs was similar to that on the ewes except that fewer lice were found on the head. Comparisons of lice per part with the numbers of lice extracted from clipped patches indicated that a sheep with wool bearing area of 1 m2 and a mean count of one louse per 10 cm fleece parting carried approximately 2000 lice. At most times of the year inspections for sheep lice should be concentrated on the sides and back, but in recently shorn sheep greater attention should be paid to the lower neck and ventral regions. Implications of the observed distributions of lice for the efficacy of chemical treatments are discussed.  相似文献   
105.
OBJECTIVE: To evaluate the outcome of urinary bladder marsupialization in male goats. STUDY DESIGN: Prospective, experimental study. ANIMALS: Six healthy mixed-breed male goats. METHODS: After experimentally induced urethral obstruction, 6 male goats had urinary bladder marsupialization. Renal ultrasonography, complete blood count, and serum biochemical analysis were evaluated preoperatively (day 0), at 7 postoperative days, and then at 30-day intervals until 180 days. Stomal diameter was recorded immediately postoperatively and at each postoperative interval. Necropsy examination was performed on day 180 or when stomal stricture or death occurred. RESULTS: Stomal stricture occurred in 1 goat at 120 days. Another goat was found dead at 150 days; severe, suppurative cystitis was identified on necropsy. All goats had mild urine scald dermatitis. Serum biochemical values remained within normal limits, but significant decreases in white blood cell count, serum creatinine concentration, and stomal diameter occurred. At necropsy, all bladders were tubular in shape. Histological evidence of chronic suppurative cystitis and chronic, mild lymphoplasmacytic pyelitis occurred in all goats. Bacterial culture of renal tissue yielded growth in 3 goats, and bladder mucosal swabs yielded bacterial growth in all goats. CONCLUSIONS: Although clinical signs of ascending urinary tract infection were not observed in goats with patent stomata, urinary bladder marsupialization may result in ascending urinary tract inflammation or infection. CLINICAL RELEVANCE: Based on our results, urinary bladder marsupialization should be recommended with caution as the primary method for management of urinary tract obstruction in clinical cases.  相似文献   
106.
To assess the effects of slaughter weight and sex on APGS (Animal Products Grading Service) quality and APGS yield grade of Korean Hanwoo (n = 20,881) cattle, data were collected from cow, bull, and steer carcasses during a 1-yr period. Factors used to determine quality grade (marbling, meat color, fat color, texture, and overall maturity score) and yield grade (cold carcass weight, adjusted fat thickness, and longissimus muscle area) by the Korean grading system were recorded. Both yield and quality grades were improved (P < 0.01) with heavier slaughter weight, but there was no difference in yield grade for Hanwoo cattle classes heavier than 551 kg (P > 0.01). Longissimus muscle area, adjusted fat thickness, and marbling score increased (P < 0.01) with carcass weight. Bull carcasses showed higher yield but lower quality than those of cows or steers (P < 0.01). The quality grade of steer carcasses was higher (P < 0.01) than that of cow carcasses due to higher marbling scores, lower maturity scores, and heavier carcass weights. Hanwoo carcasses with larger longissimus muscle areas in relation to their carcass weight had lower APGS quality grades. The APGS quality grades were different between yield grade A and B carcasses (P < 0.01), but quality grade was not improved by increased fat thickness beyond the point of yield grade B. Adjusted fat thickness and marbling score showed significant (P < 0.01) differences among all yield grade classes, and this resulted in increased quality grade as yield grade decreased. Adjusted fat thickness showed the strongest correlation (r = -0.63) with yield grade, whereas marbling score had the strongest correlation (r = 0.81) with quality grade. Results showed a negative effect of castration on yield but a positive effect on quality. Also, data showed that Hanwoo carcasses with heavier weights had higher quality grades than those of lighter weight.  相似文献   
107.
The localization and the specific activities of lysosomal enzymes in jejunal and ileal epithelium of suckling pigs were determined. Acid phosphatase was found in pinocytotic vesicles and vacoles at both intestinal sites in pigs examined during (less than or equal to 1 day old) or shortly after (2 days old) closure. These pinocytolically active vesicles and vacuoles were determined to be phagolysosomes. In the ileum, phagolysosomes persisted well after closure, at an age (10 days) when ileal epithelium retains the capacity for pinocytotic uptake of immunoglobulin, but does not transport it to blood. Neither jejunum nor ileum contained phagolysosomes at an age (30 days) when the intestine had lost both uptake and transport capacities. The specific activities of acid phosphatase and cathepsin B-1 in jejunum were similar for all age groups. However, the activities of these enzymes in ileum of 10-day-old pigs were three and five times greater than at any other age or site. The results are consistent with phagolysosomes in the ileum of 10-day-old pigs functioning as a "barrier" which prevents transport of the macromolecules which are taken up pinocytotically by this epithelium. The results do not permit conclusions whether (or not) the phagolysosomes which appear in jejunum and ileum of pigs less than or equal to 1 day old contribute to closure, because the transcellular route for immunoglobulin absorption in pigs has not been precisely defined.  相似文献   
108.
Patellar fixation is a common cause of lameness in horses and has been successfully treated by injection of the patellar ligaments with counterirritants. To investigate the effects of this treatment, the medial and middle patellar ligaments of 10 ponies were injected with an oil-based iodine counterirritant solution and then examined morphologically. Vacuoles of counterirritant were present in the paratenon and endotenon of the ligaments and caused severe necrosis and inflammation. At 1 day after injection, there was a marked neutrophilic infiltration which progressed to a lymphocytic infiltrate by 3 days. By 7 days, fibroplasia was present and became more organized with time. Disrupted collagen fibers and numerous, large, pale fibroblasts were present in the fasciculi, but neutrophilic infiltration was absent. The fibrous response in the fasciculi was similar to that present in the paratenon and endotenon. At 28 days, the drug was still present as lipid vacuoles in the paratenon and endotenon, and the damaged fasciculi had not regained their normal appearance. The clinical effect of this treatment was attributed to the change in size and shape of the patellar ligaments resulting from the inflammatory response.  相似文献   
109.
110.
A 13-year-old male lion (Panthera leo) from Dae Jeon Zoo, Republic of Korea, presented with clinical signs of lethargy and anorexia. Despite treatment with antibiotics and fluid therapy, the lion died 6 days after initial presentation. Postmortem examination revealed multiple masses measuring 5-10 cm in diameter and cysts throughout the liver. A diagnosis of spontaneous peribiliary cysts was made on the basis of microscopic lesions as well as special staining and immunohistochemical characteristics. Histologically, the neoplasm was surrounded and composed of compact collagenous tissue. The inner cystic single layer resembled biliary mucosa and was composed of cuboidal or flattened epithelial lining that was strongly immunopositive for cytokeratin AE1/AE3. This layer was surrounded by fibrous tissue that stained blue by Masson's trichrome staining. Given the presence of multiple organized cysts in the liver, the lesion was consistent with peribiliary cysts. To the authors' knowledge, this is the first report of peribiliary cysts in an animal.  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