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   436篇
  免费   29篇
林业   58篇
农学   7篇
基础科学   5篇
  87篇
综合类   4篇
农作物   31篇
水产渔业   49篇
畜牧兽医   147篇
园艺   33篇
植物保护   44篇
  2024年   1篇
  2023年   6篇
  2022年   10篇
  2021年   12篇
  2020年   10篇
  2019年   11篇
  2018年   34篇
  2017年   27篇
  2016年   25篇
  2015年   14篇
  2014年   17篇
  2013年   37篇
  2012年   17篇
  2011年   32篇
  2010年   16篇
  2009年   20篇
  2008年   27篇
  2007年   21篇
  2006年   14篇
  2005年   32篇
  2004年   17篇
  2003年   26篇
  2002年   18篇
  2001年   7篇
  2000年   4篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1995年   1篇
  1991年   1篇
  1986年   2篇
  1979年   1篇
  1978年   1篇
  1962年   1篇
排序方式: 共有465条查询结果,搜索用时 93 毫秒
431.
In this study, fractional excretions (Fe) of sodium (Na), potassium (K), chloride (Cl), calcium (Ca), magnesium (Mg) and phosphorus (PO4) were examined with the aim to demonstrate interactions between fractional excretions of these electrolytes within each period and relate them to electrolyte metabolism in clinically normal cows at different stages of lactation and dry period. The material of this study consisted of 20 clinically healthy Holstein-Friesian cows of the same age and milk yield. Blood and urine samples were collected on 190-200th, 240-250th and 270-280th days of pregnancy and on days 1-7th, 35-45th and 75-85th after calving, altogether 6 times. An increase was observed in FeCa and FeMg during the transition from the lactation to the dry period (p < 0.05), and a decrease in FeCa (p < 0.05), FeMg (p < 0.01) in the 2nd month of the dry period. FePO4 and FeMg, respectively, increased on levels of p < 0.01 and p < 0.05, while FeCa decreased on a level of p < 0.05 after gestation compared to the level before gestation. FeNa and FeK showed a decrease of p < 0.001 and p < 0.01, respectively, between the 1st and 2nd months of the dry period, while after gestation this value showed an increase in FeNa (p < 0.05) and FeK (p < 0.01). FeCl increased significantly (p < 0.05) only from postpartum to the 1st month of lactation. There was a strong positive correlation between FeNa and FeCl in all of the periods. It was concluded that there were significant changes in the Fe of Na, K, Cl, Ca, PO4 and Mg before parturition and during lactation; these changes could have an important role in assessing renal function and electrolyte balance.  相似文献   
432.
In this study, the effects of tilmicosin on some haematological and biochemical variables were investigated. Ten male New Zealand rabbits were used as material. The tilmicosin was injected (25 mg/kg body weight, subcutaneously as a single injection), and the rabbits were monitored for 4 days. No negative effects of tilmicosin on haematological and biochemical variables were observed, but it did cause a temporary decrease in red and white blood cell counts.  相似文献   
433.
In the present study, effects of enrofloxacin on biochemical, haematological and blood gas parameters were investigated. Changes in laboratory parameters were monitored during the treatment period. Enrofloxacin was administered (5 mg/kg intramuscularly, once daily) to 10 healthy dogs for 14 days. Acidosis and temporary increases in aspartate aminotransferase, indirect bilirubin, sodium, partial pressure of CO2 and mean corpuscular volume levels as well as decreased levels of inorganic phosphorus, ionized calcium, potassium, partial pressure of O2 and standard bicarbonate were observed. The results of this study suggest that these observed effects of enrofloxacin on blood gas parameters should be taken into consideration in long-term use of the drug.  相似文献   
434.
Genetic heterogeneity of Turkish ruminant pestiviruses was investigated by phylogenetic analysis of complete N(pro) encoding nucleotide sequences. A total of 30 virus isolates obtained from 15 provinces around the country between 1997 and 2005 were included in the phylogenetic analysis. Virus isolates mostly originated from cattle with one isolate from sheep. The bovine isolates all belonged to BVDV-1, the sheep isolate to BVDV-2. Fifteen isolates formed a new subgroup within BVDV-1, tentatively named BVDV-1l. The remaining bovine isolates were typed as BVDV-1a (n=4), BVDV-1b (n=4), BVDV-1d (n=3), BVDV-1f (n=2) and BVDV-1h (n=1). The isolates allocated to BVDV-1l originated from various geographical regions in different years. There was no correlation between genetic grouping and locations where isolates were obtained. Viruses originating from one farm in most cases belonged to the same subgroup (n=5). This study indicates that the newly detected subgroup BVDV-1l is predominant and widespread in Turkey. Moreover, an ovine virus isolate was identified as the first member of BVDV-2 reported in Turkey. A serological survey using samples from western Turkey indicated that BVDV-2 is also present in cattle.  相似文献   
435.
The pineal gland is a neuroendocrine organ associated with photoperiodic regulation in mammals. The aim of this study was to evaluate the pineal gland at the pre‐pubertal, pubertal and post‐pubertal periods by means of morphology and stereology. The study examined at total of 24 ovine pineal glands collected from healthy female Akkaraman breed. Thick sections (40 μm) were cut and treated with synaptophysin. Following each thick section, six consecutive sections at a thickness of 5 μm were cut. Each thin section was stained with one of the following dyes: Crossman’s modified triple dye, glial fibrillary acidic protein (GFAP), melatonin marker, periodic acid–Schiff, Von Kossa and AgNOR. The pineal gland volume was measured using Cavalieri’s method. The optical fractionator was used to estimate the total number of pinealocytes. The percentage of parenchyma and connective tissue and degree of vascularization were estimated by the area fraction fractionator method. The pineal gland volumes in the pre‐pubertal, pubertal and post‐pubertal groups were 7.53 ± 1.715 mm3, 11.20 ± 1.336 mm3 and 17.75 ± 1.188 mm3, respectively (p < .5). The number of pinealocytes in the pre‐pubertal, pubertal and post‐pubertal groups was 3,244,000 ± 228,076, 4,438,000 ± 243,610, 7,381,766 ± 406,223, respectively (p < .05). The glands of the post‐pubertal group contained the highest amount of connective tissue (11.49 ± 2.103%; p < .5) and the largest GFAP staining area (p < .05). The melatonin staining density was the highest in the pubertal group. The density of lipofuscin staining was higher in the pubertal and post‐pubertal groups.  相似文献   
436.
We determined the effect of different storage systems and packaging on the quality of ‘Sultana Seedless’ raisins. The fruit were packed in plastic boxes and kept under controlled atmosphere (1% O2 and 3% CO2) at 0°C and 75–85% RH for 12 months (CA), packed in vacuum bags and kept under normal atmosphere (21% O2–0.03% CO2) (NA) and packed in thin plastic bags + carton boxes and kept under ambient condition (semi-refrigeration), at 0°C and 90% ± 5 RH for 12 months (AC). Fruit kept under CA or NA had acceptable fruit quality in terms of general appearance and taste for 10 months, whereas fruit quality was unacceptable at that time under AC. Fruit under NA had less weight loss than fruit under the other conditions. Differences in skin colour were relatively small, apart from the h° values. Concentrations of ochratoxin A were generally higher with AC. External appearance and taste were better with CA and NA. As a result, raisins can be stored for 10 months with good quality in vacuum package in NA (0°C and 90% ± 5 RH) and CA (1% O2–3% CO2) at 0°C and 75–85% RH.  相似文献   
437.
Reference genes are essential for the normalisation of the expression data of quantitative real-time PCR for the purposes of validation. Although several reference genes have been validated for the olive, comprehensive analyses including an excessive number of candidate reference genes still require study in various olive tissue samples. In this work, a total of 40 candidate reference genes were tested for their stability in 8 different olive tissues (root, apical bud, lateral bud, pedicel, young leaf, mature leaf, fruit mesocarp, and seed) with the utilisation of the most popular software programs including GeNorm, NormFinder, BestKeeper, and ΔCt. The analyses of expression stability of candidate reference genes using quantitative real-time PCR demonstrated ubiquitin-conjugating enzyme (UBC1) as the most stable reference gene for the studied tissues of the olive. The GeNorm software also calculated the optimum reference gene combinations as two which consist of UBC1 and the Clathrin adaptor complex medium subunit (CLATHRIN) genes. This study provides the most stable reference gene combination for normalisation of target genes for quantitative real-time PCR gene expression studies on the olive.  相似文献   
438.
The physiological responses of cherry rootstocks were evaluated under moderate salinity in short term. MaxMa 14, CAB-6P and Mazzard rootstocks were treated with 35?mM NaCl solution for 1 month to assess physiological responses. Under NaCl stress, rootstocks’ physiological parameters were compared with their own control, with the greatest alterations in SPAD value, leaf relative water content (LRWC), membrane permeability and stomatal conductivity. SPAD value was reduced by 9.5, 2.17 and 2.27% in saline-treated plants of MaxMa 14, CAB-6P and Mazzard, respectively. MaxMa 14 and CAB-6P exhibited a rapid decrease in stomatal conductivity by 39.90 and 47.60%, respectively compared with their control, while in Mazzard there was a reduction by 5.28% compared with its control. Moreover, LRWC of the plants decreased by 11.24 and 13.75% in salt-treated MaxMa 14 and CAB-6P, respectively. In comparison, a lower reduction of LRWC (6.11%) was observed in NACl-treated Mazzard. As seen in the result of experiment, the inhibitory effects of NaCl were less in Mazzard compared with MaxMa 14 and CAB-6P.  相似文献   
439.
Many seeds of woody plants require low temperature for germination and that’s called seed dormancy has been investigated for relations of proteins by several researchers. We determined polypeptide profiles of cold-stratified Mazzard seeds. Seeds were studied in five different periods: seeds in dormancy (none stratified), 30, 60, 90 and 120 days cold-stratified. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) of the soluble protein fractions from stratified and none stratified seeds was utilized for determination of changes in polypeptides. SDS-PAGE revealed a decrease in the concentrations of 14 polypeptides and appearance of four low-molecular weight (15.1, 16.3, 17.8 and 19.4?kDa) polypeptides were determined in 90 and 120 day stratified seeds. The study results exhibited the evidences of the involvement of protein changes in response of Mazzard seeds during cold stratification.  相似文献   
440.
Heterobasidion species are the most important pathogens causing root and stem rot on conifers in northern hemisphere forests. The host list of this complex is very wide and includes over 200 species of trees and shrubs. Among the members of this complex, Heterobasidion annosum s. s. has the largest host range. In this study, young plants of Pinus sylvestris, Picea orientalis, Abies nordmanniana, Cedrus libani and Pinus brutia (three different origins) were inoculated on the lower stem with known genets of Heterobasidion annosum s.s. collected from Pinus brutia stands in south-western Türkiye. Infection frequency, assessed as presence of the conidial stage in stem discs following incubation, in the inoculated seedlings was 100%. The Heterobasidion annosum s. s. isolates were re-isolated from all inoculated host species. Control seedlings showed no symptoms of disease. Mortality in inoculated plants was 11.5% of the 735 inoculated plants, which died over an 8-weeks incubation period. The isolates showed greater growth on Cedrus libani, Pinus sylvestris and Picea orientalis seedlings compared to other species tested. On the other hand, it was found that the least affected seedlings were Pinus brutia TB12 and Abies nordmanniana. This study proved that differences occur in aggressiveness of Heterobasidion annosum s. s. to host species. A striking point in the results is that, despite being the host species from which the isolates were obtained, Pinus brutia seedlings showed lower sensitivity to Heterobasidion annosum s. s. than the other conifer species tested. Inoculations of three different Pinus brutia provenances suggested there was no significant difference in mean lesion lengths and fungal growth values in Pinus brutia plants, except in Pinus brutia TB14, which was more susceptible to extension growth of the pathogen.  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