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   97篇
  免费   7篇
林业   10篇
农学   4篇
  34篇
综合类   3篇
农作物   6篇
水产渔业   15篇
畜牧兽医   22篇
园艺   3篇
植物保护   7篇
  2021年   5篇
  2020年   5篇
  2019年   4篇
  2018年   8篇
  2017年   9篇
  2016年   5篇
  2015年   1篇
  2014年   4篇
  2013年   6篇
  2012年   6篇
  2011年   6篇
  2010年   4篇
  2009年   1篇
  2008年   6篇
  2007年   9篇
  2006年   8篇
  2005年   7篇
  2004年   2篇
  2003年   2篇
  2002年   2篇
  2000年   1篇
  1997年   1篇
  1990年   1篇
  1989年   1篇
排序方式: 共有104条查询结果,搜索用时 0 毫秒
51.
52.
The species of Salix herbacea L. and Salix lapponum L. are the rare relicts within the genus of Salix. With respect to their phylogeography, they are classified into the taxa of the Arctic-Alpine distribution. They can be found in the Arctic zone (Greenland, Scandinavia, Spitsbergen) as well as in such geographically separated areas as the mountains of lower latitudes like the Alps, the Sudetes or the Carpathians. Another species of willow occurring in the mountains of Europe, and more specifically on montane positions of the Balkan-Carpathian distribution is S. silesiaca. The aim of the study was to determine the severity of the diseases of the willows growing in selected locations in the Karkonosze Mountains. The research was conducted in the years 2014 and 2015 in the Kocio? ?omniczki [the ?omniczka Cirque] and the Wielki and Ma?y ?nie?ny Kocio?, [the Great and Small Snowy Cirques] at intervals of 4 weeks, from April to October. Field observations included the species of the genera Salix: S. herbacea, S. silesiaca and S. lapponum. Disease symptoms were identified with the percentage of infected plants at selected locations, as well as the percentage of infected leaves, recorded. In the course of the research, symptoms of rust caused by Melampsora epitea and M. alpina (S. herbacea and S. silesiaca), black spot blight caused by Rhytisma salicinum (S. silesiaca) and leaf spot, probably caused by a complex of fungal taxa (S. herbacea), were detected on the leaves of Salix spp. growing in post glacial cirques. During the study period, there were no disease symptoms on S. lapponum. A total of 13 species of fungi were isolated from the infected leaves of S. herbacea. In the first year, the highest share in the fungal assembly was taken by Penicillium notatum, followed by Alternaria alternata and an unidentified species of the genus Ceuthospora. In the second year of the research, Ceuthospora spp. and A. alternata predominated in the species assembly of fungi in the infected leaves of the herb willow.  相似文献   
53.
Journal of Plant Diseases and Protection - The aim of this study was to determine thrips abundance, species composition and seasonal dynamics on two genetically modified types of linseed, i.e.,...  相似文献   
54.
Stimulation of macrophages by a variety fatty acids causes activation of MAP kinases (MAPKs). The consequences arising from down-regulation of MAPKs may be a limitation in the activity of PPARγ, which is modulated by a modification catalyzed by these kinases. Phosphorylation of MAP kinases-ERK1/2 and p38 as well as PPARγ was determined by real-time polymerase chain reaction and Western blotting in human macrophages cultured with conjugated linoleic acids (CLAs). We demonstrated that CLA isomers alter MAP kinase phosphorylation and PPARγ activation. Phosphorylation of ERK1/2 was diminished in cells cultivated with cis-9,trans-11 CLA, whereas phosphorylation of p38 was reduced by trans-10,cis-12 CLA. PPARγ was phosphorylated mainly by ERK1/2, and consequently, PPARγ phosphorylation was suppressed mainly by cis-9,trans-11 isomer. In human adipocytes, cis-9,trans-11 C 18:2 raised the activation of PPAR and several of its downstream target genes. We suggest that a similar process may also occur in human macrophages.  相似文献   
55.
Thearubigins are the quantitatively major phenolic compounds in black tea, accounting for some 60-70% of the solids in a typical black tea infusion. MALDI-TOF mass spectra for caffeine-precipitated SII thearubigins (SII CTRs) from 15 different commercial teas support previous conclusions that SII CTRs are polyhydroxylated oligomers (rather than polymers) of catechins and catechin gallates in redox equilibrium with their quinone counterparts. Some 4500 peaks were revealed in a mass range from m/z 500 to 2100. Polyphenols are redox-susceptible and readily generate artifacts during MALDI-TOF analysis when the matrix is also redox-susceptible. Of the nine matrices evaluated, 3',4',5'-trihydroxyacetophenone (F) provided the best compromise between signal intensity and redox artifact formation.  相似文献   
56.
Mathematical morphology encompasses methods for characterizing land-cover patterns in ecological research and biodiversity assessments. This paper reports a neutral model analysis of patterns in the absence of a structuring ecological process, to help set standards for comparing and interpreting patterns identified by mathematical morphology on real land-cover maps. We considered six structural classes (core, perforated, edge, connector, branch, and patch) on randomly generated binary (forest, non-forest) maps in which the percent occupancy (P) of forest varied from 1% to 99%. The maps were dominated by the patch class for low P, by the branch and connector classes for intermediate P, and by the edge, perforated, and core classes for high P. Two types of pattern phase changes were signaled by abrupt transitions among the six structural classes, at critical P thresholds that were indicated by increased variance among maps for the same P. A phase change from maps dominated by the patch class to maps dominated by the branch and connector classes was related to the existence of a percolating cluster of forest, and the P threshold varied depending on the co-existence of the core class. A second phase change from the edge class to the perforated class was related to the existence of a percolating cluster of non-core (including non-forest) and represents a change of context from exterior to interior. Our results appear to be the first demonstration of multiple phase changes controlling different aspects of landscape pattern on random neutral maps. Potential applications of the results are illustrated by an analysis of ten real forest maps. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.  相似文献   
57.
The aim of the study was to examine the utilization of mineral analyses of pre-bloom leaves and inflorescences to forecast the nutrition of blackcurrant (Ribes nigrum L.). The study was carried out in Poland in 2 consecutive years on 8 mature ‘Tisel’ blackcurrant plantations planted in coarse- and medium-textured soils that were poor in organic matter. Within each plantation, plants were supplied with nitrogen (N), phosphorus (P) and potassium (K) at low, moderate or high doses for each nutrient. Every year, from the same bushes, the pre-bloom leaves, the inflorescences and the mid-summer leaves (as a standard diagnostic tool) were collected 3–6 days before flowering, when ca. 50% of flowers were open, and at harvest, respectively. No relationships between calcium (Ca) and zinc (Zn) in the studied tissues were significant. The pre-bloom leaf concentrations of N, P, magnesium (Mg), boron (B,) iron (Fe), manganese (Mn) and copper (Cu) were correlated with those in the mid-summer leaves. The relationships between the inflorescence concentrations of P, K, Mg, B, and Mn and those in the mid-summer leaves were also significant. However, only linear correlations between B and Mn in the pre-bloom leaves and the mid-summer leaves were sufficiently strong because the determination coefficients for those relationships were 81% for B and 62% for Mn. The calculated optimal concentrations of B and Mn in the pre-bloom leaves varied from 23 to 37 mg/kg and from 46 to 93 mg/kg, respectively.  相似文献   
58.
This study was performed to evaluate the ability of N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride (HTCC), the cationically modified chitosan, to form biologically inactive complexes with unfractionated heparin and thereby blocking its anticoagulant activity. Experiments were carried out in rats in vivo and in vitro using the activated partial thromboplastin time (APTT) and prothrombin time (PT) tests for evaluation of heparin anticoagulant activity. For the first time we have found that HTCC effectively neutralizes anticoagulant action of heparin in rat blood in vitro as well as in rats in vivo. The effect of HTCC on suppression of heparin activity is dose-dependent and its efficacy can be comparable to that of protamine-the only agent used in clinic for heparin neutralization. HTCC administered i.v. alone had no direct effect on any of the coagulation tests used. The potential adverse effects of HTCC were further explored using rat experimental model of acute toxicity. When administered i.p. at high doses (250 and 500 mg/kg body weight), HTCC induced some significant dose-dependent structural abnormalities in the liver. However, when HTCC was administered at low doses, comparable to those used for neutralization of anticoagulant effect of heparin, no histopathological abnormalities in liver were observed.  相似文献   
59.
The aim of this study was to characterize whitefish and peled populations in Miedwie Lake by means of the genetic analysis of ND-1 (NADH dehydrogenase 1) gene and the ITS-1 (internal transcribed spacer 1) region in order to distinguish native forms from whitefish/peled hybrids. In the analysis, archival specimens of Coregonus lavaretus maraena from the Berlin Museum für Naturkunde were used. Genetic analysis performed with the aid of MEGA 4.0 software explicitly indicated that samples from Miedwie Lake belonged entirely to a native (rapidly growing) form of whitefish. Furthermore, the conducted research has also provided crucial information for a C. lavaretus management program for Miedwie Lake.  相似文献   
60.
The aim of the study was to evaluate the effect of short-term starvation on the morphology of the digestive system of juvenile tench Tinca tinca (L.). The morphological changes in digestive structures of juveniles, fed 70 days starter or Chironomidae larvae, were examined after 1, 12, 24 and 48 h of starvation at 28 °C. The morphological changes in the organisation of the digestive structures were as follows: (1) Intestine – proteolysis of the intestinal mucosa, especially of enterocytes in apical part of mucosal folds; (2) Liver – progressive reduction of lipid vacuoles and glycogen granules, and, in effect, volume reduction of hepatocytes cytoplasm; (3) Pancreas – progressive degeneration of exocrine pancreatic cells, parallel with decrease of zymogen activity. The fish fed natural food prior to starvation seem to be more resistant to starvation than those fed starter.  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