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   1243篇
  免费   58篇
  国内免费   6篇
林业   56篇
农学   62篇
基础科学   2篇
  163篇
综合类   62篇
农作物   36篇
水产渔业   88篇
畜牧兽医   746篇
园艺   11篇
植物保护   81篇
  2021年   21篇
  2020年   19篇
  2019年   21篇
  2018年   23篇
  2017年   35篇
  2016年   34篇
  2015年   34篇
  2014年   39篇
  2013年   87篇
  2012年   74篇
  2011年   76篇
  2010年   28篇
  2009年   39篇
  2008年   54篇
  2007年   60篇
  2006年   75篇
  2005年   77篇
  2004年   61篇
  2003年   58篇
  2002年   34篇
  2001年   42篇
  2000年   49篇
  1999年   41篇
  1998年   5篇
  1997年   9篇
  1996年   7篇
  1995年   4篇
  1994年   4篇
  1992年   14篇
  1991年   15篇
  1990年   16篇
  1989年   15篇
  1988年   16篇
  1987年   18篇
  1986年   9篇
  1985年   7篇
  1984年   5篇
  1983年   8篇
  1982年   4篇
  1981年   4篇
  1979年   9篇
  1977年   7篇
  1974年   5篇
  1973年   3篇
  1972年   7篇
  1970年   3篇
  1968年   3篇
  1967年   3篇
  1966年   3篇
  1965年   3篇
排序方式: 共有1307条查询结果,搜索用时 78 毫秒
991.
The effect of wood kraft pulp (KP) feed on dietary digestibility, ruminal fluid pH, rumen fermentation characteristics, and milk production performance in lactating dairy cows was examined. Four lactating dairy cows were used for the feeding experiment by the cross‐over design. The control group and KP group were set up as treatments. The control group was fed total mixed ration (TMR) (40% roughage and 60% concentrate) and the KP group was fed TMR containing 12% KP that replaced half of the rolled corn in the control diet. The dry matter intake, digestibility of the feed components, and milk yield were not significantly different between control group and KP group. The number of times that the ruminal fluid pH was below 6.1 tended to decrease in the KP group compared to the control group (< 0.10). The acetic acid ratio in the ruminal fluid of the KP group increased compared to the control group (< 0.05) and the propionic acid ratio in the ruminal fluid of the KP group decreased compared to the control group (< 0.05). The acetate:propionate acid ratio was increased in the KP group compared with the control group (< 0.05). Lipopolysaccharide levels in the ruminal fluid of the KP group tended to decrease compared to the control group (< 0.10). Based on these results, it was indicated that the use of KP feed for lactating dairy cows induced the same rumen fermentation characteristics as those in cows given a large amount of roughage without depressing milk productivity. Therefore, KP could be a valuable feed resource substitute for grains, which would also reduce the risk for subacute rumen acidosis.  相似文献   
992.
Death‐associated protein kinase (DAPK) is a serine/threonine kinase and a tumour suppressor gene. Diffuse large B‐cell lymphomas with inactivated DAPK through hypermethylation of a CpG island is known to result in a biologically aggressive phenotype in humans. This retrospective study was carried out to analyse the prognostic significance of DAPK CpG island hypermethylation in canine lymphoma. We hypothesized that DAPK CpG island hypermethylation can be a negative prognostic indicator in dogs with nodal high‐grade B‐cell lymphoma. Forty‐seven dogs with high‐grade B‐cell lymphoma, according to the updated Kiel classification, were evaluated after being treated with a CHOP (vincristine, cyclophosphamide, doxorubicin and prednisolone)‐based chemotherapy protocol. The methylation status of the DAPK CpG island was examined by methylation‐specific PCR. Progression‐free survival (PFS) and overall survival (OS) were compared using the Kaplan‐Meier analysis and log‐rank test. The cox proportional hazard regression model was used to evaluate the effect of multiple variables. Hypermethylation of the DAPK CpG island was detected in 21 of the 47 dogs. The PFS and OS in dogs with the hypermethylation (median: 220 and 266 days, respectively) were significantly shorter than those of dogs without hypermethylation (median: 301 and 412 days, respectively) (PFS, P = .036; OS, P = .007). In the multivariate analysis, hypermethylation of the DAPK CpG island remained an independent prognostic factor in predicting shortened PFS (P = .047) and OS (P = .021) as well as clinical substage b. Overall, hypermethylation of the DAPK CpG island was a negative prognostic factor in canine high‐grade B‐cell lymphoma.  相似文献   
993.
994.
995.
Mycoplasma pneumonia of swine (MPS) is responsible for significant economic losses in the swine industry. We selected Landrace pigs for reduced MPS pulmonary lesions over five generations, and measured concentrations of the following cytokines: interleukin (IL)‐10, IL‐13, IL‐17, tumor necrosis factor (TNF)‐α and interferon (IFN)‐γ to estimate their correlation with MPS lesions. Sheep red blood cells (SRBC) were injected twice intramuscularly at 70 and 95 kg body weight. Blood serum samples were collected after 1 week of secondary SRBC inoculation and cytokine concentrations were analyzed by ELISA. Genetic parameters and breeding values were estimated. The heritability estimates of IL‐10, IL‐13, IL‐17, TNF‐α and IFN‐γ were 0.20 ± 0.06, 0.12 ± 0.06, 0.27 ± 0.07, 0.20 ± 0.10 and 0.05 ± 0.03, respectively. Genetic correlations of IL‐17 and TNF‐α with pulmonary MPS lesions were high (‐0.86 ± 0.13 and 0.69 ± 0.29, respectively) and those of IFN‐γ and IL‐13 with MPS lesions were moderately negative (‐0.45). Through selection, the breeding values of IL‐17 and IFN‐γ increased substantially and those of TNF‐α decreased. These results suggest that innate and cellular immunity are more important for the suppression of pulmonary lesions in MPS than humoral‐mediated immunity, such as antibody response.  相似文献   
996.
Increasing restrictions on the use of agrochemicals in agriculture is a major limiting factor for grapevine (Vitis vinifera L.) growers, especially with respect to the use of hydrogen cyanamide as a bud dormancy-releasing compound, which is usually necessary in sub-tropical regions. In this context, a trial of the cultivar ‘Carmem’ was carried out in a commercial vineyard located in Paraná State, Southern Brazil, with the aim of developing an environmentally friendly and economically viable bud-break treatment. The following treatments were applied over two consecutive years: (i) control (water); (ii) 2% (v/v) vegetable oil (VO); (iii) 2% (v/v) mineral oil (MO); (iv) 2% (v/v) VO + 2% (v/v) MO; or (v) 3% (v/v) hydrogen cyanamide (HC). In both years, treatments (iv) and (v) increased bud-break percentages by a similar extent, from 24–25.0% to 60–95%. Both treatments also increased the number of berry clusters and yield, from 0.9–1.3 kg to 3.3–4.6 kg per vine, and decreased catalase activity in buds until 24 h after treatment. It appears that treatment (iv) could provide a substitute for the use of 3% (v/v) hydrogen cyanamide in viticulture in the sub-tropics, and could be a sustainable alternative based on lower cost and environmental impact.  相似文献   
997.
998.
Molecular screening of GM1 gangliosidosis in Shiba dogs was carried out in northern Japan using blood smear specimens after prolonged storage. Of 125 specimens obtained from 3 veterinary teaching hospitals for this screening, 68 specimens (54%) were adequate for direct amplification in a polymerase chain reaction (PCR)-based DNA test, and the percentage of adequacy was different at each hospital (34%, 73%, and 100%), suggesting that the amount of blood on the smear and the storage condition of specimens may affect adequacy. Of the 68 dogs examined, 2 dogs (2.9%) were heterozygous carriers for this disease and the other dogs were all genotypically normal. The results suggest blood smear specimens can be useful for PCR testing after prolonged storage provided specimens contain a generous amount of blood and have been adequately stored. The study also suggests that GM1 gangliosidosis may be widely prevalent in the Shiba dog population in northern Japan.  相似文献   
999.
Murashige and Skoog medium (MS), woody plant medium (WPM), and a mixture of equal parts of MS and WPM (MW) were compared for in vitro shoot proliferation and rooting of four highbush blueberry (Vaccinium spp.) cultivars. During the multiplication stage, the shoots on WPM showed worse growth than the other shoots. The MW produced the best shoot growth. The shoots on MS grew well but tended toward hyperhydricity in the multiplication stage, especially in the case of ‘Bluecrop’ shoots. Rooting was worst in the shoots multiplied on WPM, while the best rooting percentage of ‘Bluecrop’ shoots was obtained on MS, and that of ‘O’Neal’ on MW. The rooted shoots developed a good root system and were easily acclimatized after potting.  相似文献   
1000.
Glycophorins are the major sialoglycoproteins in red blood cell membranes, possessing various physiological and pathological roles. We examined membrane glycoproteins in canine red cells and cloned cDNAs for two major glycophorins, glycophorins A (GPA) and C (GPC) from bone marrow cells. Periodic acid-Schiff staining and immunoblotting analyses showed that canine red cell membranes contained several glycoproteins immunoreactive to an anti-bovine GPC antibody, whereas the most abundant sialoglycoproteins, the candidates for GPA, did not react with an anti-human GPA antibody. The amino acid sequences of the extracellular domains of GPA and GPC had no significant homology to those from other mammalian species, including humans, and had O-linked and/or N-linked glycosylation sites. On the other hand, the C-terminal cytoplasmic domain and/or the transmembrane helices of GPA and GPC were conserved among species, indicating some functional significance of those regions in red cell membranes that include dimerization of GPA in the membrane-spanning region, and association of GPC with membrane skeletal proteins through binding with protein 4.1 and p55 in the cytoplasmic domain. These findings provide insights for clinical studies to evaluate the involvement of GPA and GPC in the pathogenesis of red cell diseases.  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