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   1060篇
  免费   73篇
  国内免费   2篇
林业   85篇
农学   30篇
  194篇
综合类   122篇
农作物   43篇
水产渔业   73篇
畜牧兽医   502篇
园艺   32篇
植物保护   54篇
  2024年   1篇
  2023年   11篇
  2022年   8篇
  2021年   22篇
  2020年   28篇
  2019年   35篇
  2018年   29篇
  2017年   36篇
  2016年   34篇
  2015年   31篇
  2014年   41篇
  2013年   63篇
  2012年   72篇
  2011年   99篇
  2010年   42篇
  2009年   40篇
  2008年   85篇
  2007年   76篇
  2006年   55篇
  2005年   53篇
  2004年   61篇
  2003年   50篇
  2002年   59篇
  2001年   4篇
  2000年   12篇
  1999年   6篇
  1998年   11篇
  1997年   5篇
  1996年   4篇
  1995年   5篇
  1994年   5篇
  1993年   4篇
  1992年   4篇
  1991年   7篇
  1990年   7篇
  1989年   3篇
  1988年   2篇
  1986年   1篇
  1985年   4篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1979年   3篇
  1978年   2篇
  1977年   3篇
  1975年   1篇
  1974年   1篇
  1973年   3篇
  1966年   1篇
排序方式: 共有1135条查询结果,搜索用时 46 毫秒
141.
Equine piroplasmosis (EP) has not been considered indigenous in The Netherlands. However, following the detection of an apparently indigenous subclinical Babesia caballi infection in a horse on Schouwen-Duiveland (an island in the Zeeland Province), a survey was undertaken between May and September 2010 to assess the prevalence of the causative agents of EP in the South-West of The Netherlands. Blood samples from 300 randomly selected horses were tested for specific antibodies against Theileria equi and B. caballi using an indirect fluorescence antibody test (IFAT), and for parasite DNA using a specific polymerase chain reaction combined with reverse line blotting (PCR-RLB). Twelve of the horses (4%) were seropositive for EP. Of these, nine (75%) were positive (titre?1:160) for B. caballi alone and three (25%) were also positive for T. equi. PCR-RLB detected T. equi DNA in five horses (1.6%), two of which were seronegative. Four (1.3%) of the positive horses (three positive for T. equi and one for both B. caballi and T. equi) were considered truly indigenous. During the study, two indigenous ponies from a farm situated outside the sampling area were diagnosed with acute clinical piroplasmosis characterized by severe anaemia and pyrexia. Blood smears showed T. equi - like inclusions in red blood cells, and T. equi infection was confirmed in both ponies by PCR-RLB. The initial subclinical B. caballi infection, the survey results and the two acute clinical EP cases confirmed the autochthonous transmission of B. caballi and T. equi infections in The Netherlands.  相似文献   
142.
Dung beetles are considered keystone species because of their role in decomposition, seed dispersal, and control of vertebrate parasites in grazed habitats. Despite the ecological importance of this group to pasture ecosystem functioning, still little is known about its relationship with grazing management activities. We evaluated the conservation value of protected areas for dung beetle diversity by comparing two different management conditions of Mediterranean savanna in central Spain. Four different sites with wild herbivory (red deer, roe deer) were sampled inside the Cabañeros National Park, and four sites with traditional agrosilvopastoral management were sampled in a sheep farm near the park. The dung beetle species richness was similar between savanna conditions, but the total dung beetle abundance and biomass were considerably greater in the park grasslands than in the grasslands of the sheep farm. Dung beetle species composition, species dominance, and abundance by functional groups from both park and farm sites were different, despite the high similarity among the sampled sites in both hydric content and dung availability. Onthophagus maki (Illiger 1803) and O. furcatus (Fabricius 1781) were the dominant species in the park, while O. furcatus, Aphodius foetidus (Herbst 1783), and Caccobius schreberi L. were the dominant species on the farm. Species richness and abundance of telecoprids were higher in the park than on the farm. Abundance of paracoprids was also higher in the park than on the farm, while no differences in species richness and abundance of endocoprids were observed between both conditions. These results suggest that management activities such as plowing and the use of veterinary substances affect soil structure and dung quality and could be important factors that alter dung beetle assemblages in terms of composition, abundance, and biomass on traditional farms.  相似文献   
143.
144.
Lamellar pathology in experimentally-induced equine laminitis associated with euglycaemic hyperinsulinaemia is substantial by the acute, clinical phase (~48 h post-induction). However, lamellar pathology of the developmental, pre-clinical phase requires evaluation. The aim of this study was to analyse lamellar lesions both qualitatively and quantitatively, 6, 12 and 24 h after the commencement of hyperinsulinaemia. Histological and histomorphometrical analyses of lamellar pathology at each time-point included assessment of lamellar length and width, epidermal cell proliferation and death, basement membrane (BM) pathology and leucocyte infiltration. Archived lamellar tissue from control horses and those with acute, insulin-induced laminitis (48 h) was also assessed for cellular proliferative activity by counting the number of cells showing positive nuclear immuno labelling for TPX2.Decreased secondary epidermal lamellar (SEL) width and increased histomorphological evidence of SEL epidermal basal (and supra-basal) cell death occurred early in disease progression (6 h). Increased cellular proliferation in SELs, infiltration of the dermis with small numbers of leucocytes and BM damage occurred later (24 and 48 h). Some lesions, such as narrowing of the SELs, were progressive over this time period (6–48 h). Cellular pathology preceded leucocyte infiltration and BM pathology, indicating that the latter changes may be secondary or downstream events in hyperinsulinaemic laminitis.  相似文献   
145.
146.
Myristica dactyloides is characteristic of the mid- and high-elevation evergreen forests of the Western Ghats of India. Aril and seeds of the species are valuable nontimber forest products and are harvested extensively. We made visual estimates of fruit crop size in nine populations. We assessed disturbance using five variables: distance from road, method of harvesting fruits, nonforest matrix around the population, seedling regeneration, and protected area status. Unsustainable harvest and proximity to road impacted fruit crop, as did the nonforest matrix (F = 38.17 df = 5,102, p < .001). While high protection and measures against harvesting keep some populations safe, the harvest method plays a crucial role in determining total fruit production and seedling recruitment in the species.  相似文献   
147.
148.
Dicathais orbita is a large Australian marine gastropod known to produce bioactive compounds with anticancer properties. In this research, we used bioassay guided fractionation from the egg mass extract of D. orbita using flash column chromatography and identified fractions containing tyrindoleninone and 6-bromoisatin as the most active against colon cancer cells HT29 and Caco-2. Liquid chromatography coupled with mass spectrometry (LCMS) and 1H NMR were used to characterize the purity and chemical composition of the isolated compounds. An MTT assay was used to determine effects on cell viability. Necrosis and apoptosis induction using caspase/LDH assay and flow cytometry (PI/Annexin-V) and cell cycle analysis were also investigated. Our results show that semi-purified 6-bromoisatin had the highest anti-cancer activity by inhibiting cell viability (IC50 = ~100 µM) and increasing caspase 3/7 activity in both of the cell lines at low concentration. The fraction containing 6-bromoisatin induced 77.6% apoptosis and arrested 25.7% of the cells in G2/M phase of cell cycle in HT29 cells. Tyrindoleninone was less potent but significantly decreased the viability of HT29 cells at IC50 = 390 µM and induced apoptosis at 195 µM by increasing caspase 3/7 activity in these cells. This research will facilitate the development of these molluscan natural products as novel complementary medicines for colorectal cancer.  相似文献   
149.
The intestine and the gut-associated lymphoid tissue(GALT) are essential components of whole body immune defense,protecting the body from foreign antigens and pathogens,while allowing tolerance to commensal bacteria and dietary antigens.The requirement for protein to support the immune system is well established.Less is known regarding the immune modifying properties of individual amino acids,particularly on the GALT.Both oral and parenteral feeding studies have established convincing evidence that not only the total protein intake,but the availability of specific dietary amino acids(in particular glutamine,glutamate,and arginine,and perhaps methionine,cysteine and threonine) are essential to optimizing the immune functions of the intestine and the proximal resident immune cells.These amino acids each have unique properties that include,maintaining the integrity,growth and function of the intestine,as well as normalizing inflammatory cytokine secretion and improving T-lymphocyte numbers,specific T cell functions,and the secretion of IgA by lamina propria cells.Our understanding of this area has come from studies that have supplemented single amino acids to a mixed protein diet and measuring the effect on specific immune parameters.Future studies should be designed using amino acid mixtures that target a number of specific functions of GALT in order to optimize immune function in domestic animals and humans during critical periods of development and various disease states.  相似文献   
150.
Two carboxylic acid haptens of glycitein were synthesized, with a spacer arm at the C2 position. They differed in the length of the spacer arm, with the length of the spacer arms being three or four carbon atoms, and were named Delta3-glycitein and Delta4-glycitein haptens, respectively. The different haptens were coupled to bovine serum albumin (BSA), and the coupling efficiency was assessed by MALDI mass spectrometry. Polyclonal antibodies were generated against the BSA conjugates. An additional conjugate of Delta4-glycitein hapten was generated with swine thyroglobulin (Thyr). Enzyme-linked immunosorbent assays (ELISAs) based on the competition between free glycitein and Delta4-glycitein-Thyr conjugates for specific antibodies were developed. The IC50 of the standard curves was 15.6 ng mL(-1) with anti-Delta3-glycitein and 62.5 ng mL(-1) with anti-Delta4-glycitein, that is, 10.9 and 44 pmol/well, respectively. With the Delta3-glycitein antibody, interassay and intra-assay variations were 12.2 and 11.5%, respectively. Specificity tests did not show any significant cross-reaction with any other soy isoflavone. This specificity is not influenced by the length of the spacer arm. The assay was validated by measurements performed on plasma samples as well as on soy-based foodstuffs and on soy-based food supplements.  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