全文获取类型
收费全文 | 195篇 |
免费 | 12篇 |
专业分类
林业 | 33篇 |
农学 | 3篇 |
基础科学 | 1篇 |
35篇 | |
综合类 | 12篇 |
农作物 | 5篇 |
水产渔业 | 6篇 |
畜牧兽医 | 75篇 |
园艺 | 2篇 |
植物保护 | 35篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 10篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 10篇 |
2012年 | 19篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 14篇 |
2007年 | 14篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 13篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有207条查询结果,搜索用时 281 毫秒
1.
Stable isotopes and gut contents indicate differential resource use by coexisting asp (Leuciscus aspius) and pikeperch (Sander lucioperca) 下载免费PDF全文
Mojmír Vašek Antti P. Eloranta Ivana Vejříková Petr Blabolil Milan Říha Tomáš Jůza Marek Šmejkal Josef Matěna Jan Kubečka Jiří Peterka 《Ecology of Freshwater Fish》2018,27(4):1054-1065
Differential use of habitat and prey resources is an important mechanism that may allow coexistence of sympatric species. Unlike interactions between smaller cyprinid and percid fishes, the resource use by coexisting predatory asp (Leuciscus aspius) and pikeperch (Sander lucioperca) is relatively unknown. Here, gut content and stable isotope analyses were used to study ontogenetic dietary shifts and interspecific trophic niche overlap between asp and pikeperch coexisting in two reservoirs. The hypothesis that both species show an ontogenetic dietary shift from small invertebrates to large fish prey, but at the same time use different prey resources to reduce potential competitive interactions, was validated. The isotopic niches of the two predators showed no, or only a moderate, degree of overlap (0%–65%). The ontogenetic changes in the degree of interspecific isotopic niche overlap were different in the two reservoirs, suggesting that trophic segregation can be dynamic and variable among systems. Gut contents revealed that small (<100 mm standard length) asp consumed mostly terrestrial invertebrates and emerged aquatic insects, whereas small pikeperch foraged on zooplankton, larval and pupal stages of aquatic insects and fish. Larger individuals (>100 mm) of both species were predominantly piscivorous, with asp consuming more cyprinid prey and pikeperch more percid prey. Coexisting asp and pikeperch populations are able to utilise different prey resources, thereby reducing potential negative competitive interactions. 相似文献
2.
Marek Šmejkal Marie Prchalová Martin Čech Mojmír Vašek Milan Říha Tomáš Jůza Petr Blabolil Jan Kubečka 《Ecology of Freshwater Fish》2014,23(3):405-413
Fish associations with different types of littoral habitats were studied in four canyon‐shaped reservoirs in the Czech Republic in years 2010 and 2011 by gillnets. Two to three habitats per reservoir–beaches (former meadows), stump fields (former forest) and rubble slopes–were defined and sampled along the longitudinal axis of reservoirs. Effects of reservoir, habitat and locality (position along longitudinal axis) on fish biomass, abundance and species structure were tested for juvenile and adult fish separately. Hierarchical analysis of variance revealed that habitats differed significantly in fish biomass and abundance. Redundancy analysis showed that analysed environmental variables had significant influence on fish community structure. Most variability in community structure was explained by reservoir and then by combination of habitat and slope steepness. Locality position had the smallest influence on community structure. For both adult and juvenile fish total abundance and biomass, the most inhabited habitat was beaches; rubble slopes were the least inhabited. Habitat associations differed among species. Among adults, bream Abramis brama, white bream Blicca bjoerkna and roach Rutilus rutilus were associated with beaches and stump fields, whereas perch Perca fluviatilis, ruffe Gymnocephalus cernuus, asp Aspius aspius and pike Esox lucius were associated with rubble slopes. Bream, white bream, bleak Alburnus alburnus, roach, ruffe and pikeperch Sander lucioperca were associated with beaches among juveniles, whereas the only juvenile associated with rubble slopes was perch. We showed that most common species are associated with distinct habitats and also that utilisation of various littoral habitats differs in general. 相似文献
3.
In vivo, resumption of oocyte meiosis occurs in large ovarian follicles after the
preovulatory surge of luteinizing hormone (LH). The LH surge leads to the activation of a broad signaling
network in mural granulosa cells equipped with LH receptors. The signals generated in the mural granulosa
cells are further augmented by locally produced peptides or steroids and transferred to the cumulus cell
compartment and the oocyte itself. Over the last decade, essential progress has been made in the
identification of molecular events associated with the final maturation and ovulation of mammalian oocytes.
All new evidence argues for a multiple roles of mitogen-activated protein kinase 3/1 (MAPK3/1) in the
gonadotropin-induced ovulation processes. However, the knowledge of gonadotropin-induced signaling pathways
leading to MAPK3/1 activation in follicular cells seems limited. To date, only the LH-induced transactivation
of the epidermal growth factor receptor/MAPK3/1 pathway has been described in granulosa/cumulus cells even
though other mechanisms of MAPK3/1 activation have been detected in other types of cells. In this review, we
aimed to summarize recent advances in the elucidation of gonadotropin-induced mechanisms leading to the
activation of MAPK3/1 in preovulatory follicles and cultured cumulus-oocyte complexes and to point out a
specific role of this kinase in the processes accompanying final maturation of the mammalian oocyte. 相似文献
4.
Studies on the predatory insects of the Sycamore lace bug (Corythuca ciliata (Say))
In our previous work (Maceljski, andBalarin, 1974) we presented some results of our first investigations of the new insect introduced in Europe from North America, the Sycamore lace bug (Corythuca ciliata [SAY]). There we concluded that it is necessary to bring this insect under control especially by biological means.In our recent work we established that some most usual predatory bugs in Yugoslavia, i. e.Nabis pseudoferus Rm.,Rhinocoris iracundus iracundus (Pd.) andHimacerus mirmicoides (O. C.) are in the laboratory very effective sucking on the Sycamore lace bugs. Therefore it is possible that these predators will have a negative influence on the population-dynamic of this new nuisible insects in Europe. The investigation added to the knowledge of the possible preys of these bugs too.
Die Untersuchungen wurden von der Stadt Zagreb unterstutzt. 相似文献
Die Untersuchungen wurden von der Stadt Zagreb unterstutzt. 相似文献
5.
• Background
In the development of pure beech and pure spruce pristine forests, we assume there should be a continuous transition from full stocking to successive disintegration and, finally, total replacement of the first generational wave at the end of its lifetime, dependent on mortality due to overcrowding as well as ageing, leading newly recruited cohorts to grow up from below. 相似文献6.
Dragan Nonic John C. Bliss Vojislav Milijic Nenad Petrovic Mersudin Avdibegovic Milan Mataruga 《Small-Scale Forestry》2011,10(4):435-455
Small-scale forestry in Serbia is characterized by high fragmentation of properties, a large number of parcels and forest
owners. Numerous activities for private forest owners in Serbia supported by the State, FAO and CEPF have resulted in an increased
interest of owners in forming private forest owners’ associations (PFOA). The goal of this paper is to explore preconditions
that are necessary for organizing private forest owners in Serbia into effective associations. In order to reach this goal,
results of PRIFORT project were used. The over-arching research questions of this paper are: “What is the level of interest
among forest owners in forming owners’ associations?”; “Why has forest owner interest in organizing developed so slowly?”
and “What are the necessary preconditions for the development of private forest owners’ organizations in the country?” In
order to answer these questions, quantitative survey with 42 close, open and Likert scale questions was conducted. Sample
size was determined following Malhotra’s proportion method and, in total, 350 private forest owners, from nine municipalities
were interviewed. Results of this paper show that majority of respondents are very little or not at all aware of existing
legislation. Almost half of respondents consider that their interests are not represented well. Although about 50% of interviewed
forest owners miss interest organization, only 0,3% are members of PFOA. More than 70% are ready to join association, if it
would provide some economic advantages. 相似文献
7.
Leontowicz M Gorinstein S Leontowicz H Krzeminski R Lojek A Katrich E Cíz M Martin-Belloso O Soliva-Fortuny R Haruenkit R Trakhtenberg S 《Journal of agricultural and food chemistry》2003,51(19):5780-5785
The aim of this study was to assess the bioactive compounds of apple and pear peel and pulp in vitro and their influence on plasma lipids and antioxidant potentials in vivo. The antioxidant potentials measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH), beta-carotene bleaching (beta-carotene), and nitric oxide inhibition radical scavenging (NO) tests in apple peel and pulp were significantly higher than in pear peel and pulp, respectively. The ethanol extract of apple peels showed the strongest inhibition of lipid peroxidation as a function of its concentration and was comparable to the antioxidant activity of butylated hydroxyanisole. The pear pulp extract had the weakest antioxidant ability, whereas other extracts such as apple pulp and pear peel were nearly equal. The antioxidant activities comprised contributions from polyphenols, phenolic acids, and flavonoids and correlated well with polyphenols and flavonoids. The correlation coefficients between polyphenols and antioxidant activities by DPPH, beta-carotene, and NO were as follows: 0.9207, 0.9350, and 0.9453. Contrarily, the correlation coefficient between the content of dietary fiber and the antioxidant activities test was low. The content of all studied indices in apple and pear peel was significantly higher than in peeled fruits (p < 0.05). Diets supplemented with fruit peels exercised a significantly higher positive influence on plasma lipid levels and on plasma antioxidant capacity of rats than diets with fruit pulps. 相似文献
8.
Novák J Tykva R Wimmer Z Pavlík M Prouza M Hlavsová K Zarevúcka M 《Journal of agricultural and food chemistry》2008,56(15):6604-6608
Two bacteria were isolated from sand RQ30, characterized as Bacillus simplex and Bacillus sp. strain 05 (GenBank EU399813 ), and were used as biocatalysts for a hydrolytic assay of stability of the cis or trans isomers of ethyl N-{2-{4-{[2-(butanoyl)oxycyclohexyl]methyl}phenoxy}ethyl}carbamate, which are among insect hormonogen substances (juvenogens). The stability tests were performed using simple modeling under laboratory conditions. The structures of the products were assigned as ethyl (1 R,2 R)- N-{2-{4-[(2-hydroxycyclohexyl)methyl]phenoxy}ethyl}carbamate and ethyl (1 S,2 R)- N-{2-{4-[(2-hydroxycyclohexyl)methyl]phenoxy}ethyl}carbamate on the basis of (1)H and (13)C NMR, IR, and FAB-MS analyses. 相似文献
9.
J. Ren H. Tang X. Yan X. Huang B. Zhang H. Ji B. Yang D. Milan & L. Huang 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2009,126(1):30-36
The enterotoxigenic Escherichia coli (ETEC) F4ac is a major cause of diarrhoea in newborn and young pigs. The locus for the intestinal ETEC F4ac receptor (F4acR) has been mapped to pig chromosome (SSC) 13q41 with known homology to human chromosome (HSA) 3q21 and q29. However, the causative gene and mutation(s) remain unknown. The aim of this study was to characterize gene-derived markers on SSC13q41 for fine mapping of the F4acR locus, and construct a high-resolution pig–human comparative map to select positional candidate genes for F4acR. Pig-specific sequence-tagged site markers were developed for 20 genes that are located in a 6.8-Mb region on HSA3q21 and q29, and a total of 34 single-nucleotide polymorphisms (SNPs) were identified in 14 of 20 markers developed. Eighteen markers were mapped to SSC13q41, while the other two markers ( PLXNA1 and KLF15 ) were assigned to SSC13q32 and SSC7q13, respectively, by radiation hybrid mapping. This result showed that there was a small conserved segment on SSC7 corresponding to HSA3q21. A framework map comprising 18 markers on SSC13q41 was established, refining the synteny breakpoint on SSC13q41 to a region of 12.3 centiRay. The comparative radiation hybrid (RH) map revealed three interesting candidate genes for F4acR from the human genome, viz. MUC4 , MUC13 and MUC20 . Linkage analysis with six marker polymorphisms revealed that MUC4 had the most significant linkage with the F4acR locus. 相似文献
10.
Jelena Petrović Snežana Dragović Ranko Dragović Milan Đorđević Mrđan Đokić Mirjana Ćujić 《Journal of Soils and Sediments》2016,16(4):1168-1175