全文获取类型
收费全文 | 498篇 |
免费 | 34篇 |
专业分类
林业 | 68篇 |
农学 | 15篇 |
101篇 | |
综合类 | 21篇 |
农作物 | 39篇 |
水产渔业 | 28篇 |
畜牧兽医 | 185篇 |
园艺 | 21篇 |
植物保护 | 54篇 |
出版年
2023年 | 3篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 38篇 |
2017年 | 22篇 |
2016年 | 33篇 |
2015年 | 15篇 |
2014年 | 26篇 |
2013年 | 24篇 |
2012年 | 35篇 |
2011年 | 50篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 26篇 |
2007年 | 28篇 |
2006年 | 27篇 |
2005年 | 26篇 |
2004年 | 14篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1990年 | 2篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1963年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1932年 | 1篇 |
1926年 | 2篇 |
1918年 | 2篇 |
排序方式: 共有532条查询结果,搜索用时 31 毫秒
491.
Karl H. Mellert Jonathan Lenoir Susanne Winter Christian Kölling Andraž Čarni Isabel Dorado-Liñán Jean-Claude Gégout Axel Göttlein Daniel Hornstein Matthias Jantsch Nina Juvan Eckart Kolb Eduardo López-Senespleda Annette Menzel Dejan Stojanović Steffen Täger Ioannis Tsiripidis Thomas Wohlgemuth Joerg Ewald 《European Journal of Forest Research》2018,137(1):79-92
Based on macroecological data, we test the hypothesis whether European tree species of temperate and boreal distribution maintain their water and nutrient supply in the more arid southern margin of their distribution range by shifting to more fertile soils with higher water storage than in their humid core distribution range (cf. soil compensatory effects). To answer this question, we gathered a large dataset with more than 200,000 plots that we related to summer aridity (SA), derived from WorldClim data, as well as soil available water capacity (AWC) and soil nutrient status, derived from the European soil database. The soil compensatory effects on tree species distribution were tested through generalized additive models. The hypothesis of soil compensatory effects on tree species distribution under limiting aridity was supported in terms of statistical significance and plausibility. Compared to a bioclimatic baseline model, inclusion of soil variables systematically improved the models’ goodness of fit. However, the relevance measured as the gain in predictive performance was small, with largest improvements for P. sylvestris, Q. petraea and A. alba. All studied species, except P. sylvestris, preferred high AWC under high SA. For F. sylvatica, P. abies and Q. petraea, the compensatory effect of soil AWC under high SA was even more pronounced on acidic soils. Soil compensatory effects might have decisive implications for tree species redistribution and forest management strategies under anthropogenic climate change. Therefore, soil compensatory effects deserve more intensive investigation, ideally, in studies combining different spatial scales to reduce the uncertainty associated with the precision of soil information. 相似文献
492.
Rafał Strachel Jadwiga Wyszkowska Małgorzata Baćmaga 《Water, air, and soil pollution》2018,229(7):235
Zinc exerts negative effects on soil and contributing to the degradation of soil ecosystems. New solutions for restoring healthy soil activity are therefore needed. The aim of this study was to evaluate the effectiveness of sorbents in the biological remediation of soil contaminated with zinc. A pot experiment was conducted on loamy sand. The tested plant was maize (Zea mays). Soil was contaminated with zinc chloride doses of 0, 100, 300, and 900 mg Zn2+ kg?1 DM soil (dry matter of soil). Alginate, biochar, sepiolite, calcined halloysite, and a molecular sieve were added to soil in amounts corresponding to 2.5% of soil weight to minimize zinc’s potentially toxic effects on the biological properties of soil. The application of zinc stimulated the proliferation of all analyzed microbial groups. Zinc exerted negative effects on the ecophysiological diversity (EP) of fungi and the activity of dehydrogenases, catalase, and acid phosphatase. The applied sorbents modified the microbiological and biochemical properties of soil. In zinc-contaminated soil, alginate, biochar, and molecular sieve increased the counts of organotrophic, oligotrophic, and actinobacteria. Sorbents were not highly effective in promoting fungal growth and exerted varied effects on the activity of soil enzymes. The molecular sieve stimulated the activity of all soil enzymes, excluding β-glucosidase. Alginate minimized the negative influence of zinc on dehydrogenases and acid phosphatase, and biochar—on catalase, sepiolite, and calcined halloysite —on acid phosphatase. By modifying the biological properties of soil, the tested sorbents contributed to an increase in maize yields and a decrease in zinc uptake by maize plants. 相似文献
493.
Neda Tešan Tomić Slavko Smiljanić M. Jović M. Gligorić D. Povrenović A. Došić 《Water, air, and soil pollution》2018,229(9):303
As a result of the destruction of ammunition, mines, and explosive devices by the method of open detonation, the increased concentration of heavy metals is often recorded in the soil of military polygons, which is a serious ecological problem. However, in order to determine the potential risk of such locations to the environment, it is necessary to determine, in addition to the total content, the forms in which the metals are present. In this paper, a sequential extraction method was used to analyze the six fractions of five heavy metals (cadmium, lead, nickel, copper, and zinc) in the soil of the polygon for destruction of ammunition, mines, and explosive devices. Samples were collected from the place of direct detonation (so-called pits) and from the edge of the pit. The aim of this research is determination of metal speciation in order to obtain a better insight in their mobility and risk arising from this. The results showed that heavy metals are predominantly present in the residual, oxide, and organic fractions. Cd and Cu were also significantly present in the mobile fractions due to conducted activities on the polygon. To assess the potential environmental risk of soil, the risk assessment code (RAC) and individual (ICF) and global (GCF) contamination factors were used. According to the RAC, the mobility and bioavailability of the analyzed heavy metals decreases in the following order: Cd?>?Cu?>?Zn?>?Pb?>?Ni. ICF results show low to moderate risk, while GCF results show low risk in terms of heavy metal contamination in the examined area. 相似文献
494.
Mato Drenjančević Vladimir Jukić Krunoslav Zmaić Toni Kujundžić 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2017,67(8):705-711
The aim of this study was to determine the impact of two different treatments of early defoliation performed before blooming on: grape yield, chemical parameters, polyphenols content, and antioxidant activity of grape and red wine cv. Cabernet Sauvignon from the vineyard located in Ilok, the eastern continental region of Croatia. Two different treatments of leaf removal (LR) were performed: removal of 3 leafs (T1) and 6 leafs (T2) before blooming, together with control (no leaf removal) (T3) during two years (2013 and 2014). Crop yield and average cluster weights per vine were determined. Density, pH and titratable acidity were measured in must, while the total phenols, total anthocyanins and antioxidant activity were measured in the extract of grape skin and produced wine. The analysis of individual anthocyanins in wine was performed by HPLC method. T2 treatment significantly lowered the crop yield and the average cluster weights, and increased total phenols, total anthocyanins, antioxidant activity and most abundant individual anthocyanins in wine. Defoliation did not affect the other chemical parameters in must, grape skin extract and wine. Vintage year is statistically the most significant source of variability for density of must, antioxidant activity in grape skin extract, as well as pH and titratable acidity in wine. This study has showed that the early leaf removal treatment in eastern continental part of Croatia could be used for the production of smaller quantity of high quality Cabernet Sauvignon red wine abundant with anthocyanins. 相似文献
495.
Svetlana Milijašević-Marčić Miloš Stepanović Biljana Todorović Bojan Duduk Jelena Stepanović Emil Rekanović Ivana Potočnik 《European journal of plant pathology / European Foundation for Plant Pathology》2017,148(3):509-519
Fifty bacterial isolates obtained from compost were tested in vitro against the causal agents of green mould in Agaricus bisporus. Isolate B-38 which induced 48.08% in vitro growth inhibition of T. harzianum T54 and 52.25% of T. aggressivum f. europaeum T77 was identified as Bacillus subtilis, based on 16S rDNA sequence and used in mushroom growing room experiments. B. subtilis B-38 did not decrease mycelial growth rate of Agaricus bisporus A15 in mushroom compost in glass tubes. After applying prochloraz-manganese, B. subtilis B-38 and B. subtilis QST 713, no significant differences in BE values among treatments were found concerning both total yield and the weight of healthy mushrooms. Statistical analyses showed that only inoculation significantly influenced the healthy mushroom yield. In plots inoculated with T. harzianum T54 disease incidence was significantly lower after treatments with prochloraz-manganese (11.81%), B. subtilis QST 713 (12.26%) and B. subtilis B-38 (14.19%) compared to the control (28.16%), as well as in plots inoculated with T. aggressivum f. europaeum T77 11.88%, 12.2% and 15.03%, respectively, in comparison with the control (23.47%). Statistically significant differences were not found among the efficacy values of tested bio-fungicides based on B. subtilis and the commercial fungicide prochloraz-manganese suggesting the use of B. subtilis B-38 and B. subtilis QST 713 as good alternatives to chemical fungicides. 相似文献
496.
Michael Heym Ricardo Ruíz-Peinado Miren Del Río Kamil Bielak David I. Forrester Gerald Dirnberger Ignacio Barbeito Gediminas Brazaitis Indrė Ruškytkė Lluís Coll Marek Fabrika Lars Drössler Magnus Löf Hubert Sterba Václav Hurt Viktor Kurylyak Fabio Lombardi Dejan Stojanović Jan Den Ouden Renzo Motta Maciej Pach Jerzy Skrzyszewski Quentin Ponette Géraud De Streel Vit Sramek Tomáš Čihák Tzvetan M. Zlatanov Admir Avdagic Christian Ammer Kris Verheyen Buraczyk Włodzimierz Andrés Bravo-Oviedo Hans Pretzsch 《Annals of Forest Science》2017,74(3):63
Key message
This data set provides unique empirical data from triplets of Scots pine ( Pinus sylvestris L.) and European beech ( Fagus sylvatica L.) across Europe. Dendrometric variables are provided for 32 triplets, 96 plots, 7555 trees and 4695 core samples. These data contribute to our understanding of mixed stand dynamics. Dataset access at http://dx.doi.org/10.5061/dryad.8v04m . Associated metadata available at https://metadata-afs.nancy.inra.fr/geonetwork/apps/georchestra/?uuid=b3e098ca-e681-4910-9099-0e25d3b4cd52&hl=eng .497.
498.
Jasmina Nestorović Danijela Mišić Branislav Šiler Marina Soković Jasmina Glamočlija Ana Ćirić Vuk Maksimović Dragoljub Grubišić 《Fitoterapia》2010
Rapid micropropagation of Nepeta rtanjensis, N. sibirica and N. nervosa was performed. Qualitative and quantitative nepetalactone content in methanol extracts of in vitro grown plants was analysed by reverse-phase HPLC coupled with UV and MS detection. Only trans,cis-nepetalactone was detected in shoots of N. rtanjensis, while cis,trans-nepetalactone stereoisomer was present in N. sibirica. No nepetalactone was observed in shoots of N. nervosa. The antimicrobial activity of methanol extracts, against eight bacterial and eight fungal species, was evaluated. All the tested extracts showed significant antibacterial and strong antifungal activity. However, N. rtanjensis extract exhibited the best antimicrobial potential. 相似文献
499.
S. Kamiński M. Koćwin‐Podsiadła H. Sieczkowska H. Help A. Zybert E. Krzęcio K. Antosik P. Brym E. Wójcik G. Adamczyk 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2010,127(2):125-132
Low heritability of meat quality traits and the lack of their systematic registration in breeding programs have encouraged the search for single nucleotide polymorphisms (SNPs) located within genes coding the proteins involved in muscle and fat metabolism. In this report, a panel of 52 SNPs was used to find which alleles and genotypes are more/less frequent in groups of pigs differentiated by extreme value of glycolytic potential (GP) and drip loss (DL). The analysis was carried out in 52 fatteners (chosen from 246 pigs), of which 28 were Landrace and 27 Landrace × Yorkshire. Two designs were performed: I, fatteners were divided into two groups showing extreme value of GP (<125 versus >145), II, fatteners were divided into two groups showing extreme value of DL (<6.0 versus >6.0). Allele frequency differences between the phenotypic groups of extreme GL or DL were not influenced by the breed. The frequency of 52 SNPs alleles for each of group was calculated and a chi‐squared test was used to estimate the significance of differences in allele frequencies between alternative groups in each experimental design. Three SNPs (DECR1, PPARGC1, MC4R) and another two (CYP21, SFRS1) showed significant differences between groups of extreme GP and DL, respectively. To exemplify and validate potential associations of candidate SNPs for GP and DL, 293 fatteners representing three commercial breeds/crosses (95 Landrace, 66 Landrace × Yorkshire and 132 Landrace × Yorkshire × Duroc were genotyped for DECR1 and CYP21 by PCR‐RFLP assays. DECR1 showed significant associations with GP in Landrace and Landrace × Yorkshire × Duroc fatteners. CYP21 showed significant associations with DL in all breeds/crosses. Interestingly, the CYP21 polymorphism revealed adverse associations trend in Landrace × Yorkshire × Duroc pigs in comparison to Landrace and Landrace × Yorkshire fatteners. 相似文献
500.
Becskei Z Aleksić-Kovačević S Rusvai M Balka G Jakab C Petrović T Knežević M 《Acta veterinaria Hungarica》2010,58(4):483-498
The lymphatic organs of 50 pigs from a total of eight farms located at different sites in the epizootiological region of North Ba?ka County were studied to obtain data on the prevalence of circoviral infections in Serbia. All of the pigs examined had clinical signs suggestive of postweaning multisystemic wasting syndrome (PMWS). All pigs underwent necropsy and tissue samples were taken for histopathological, immunohistochemical (IHC) and PCR analysis. The presence of porcine circovirus 2 (PCV2) was established by PCR analysis in the organs of the pigs tested. The most frequent histopathological lesions of lymphoid tissue linked with the presence of positive immunostaining for PCV2 Cap antigen confirmed the existence of PMWS in all farms tested in North Ba?ka County. Using PCR, histopathological and IHC techniques, the presence of PMWS was proved in the Republic of Serbia. During necropsy, generalised enlargement of the lymph nodes was evident. The most common histopathological finding was lymphocyte depletion in the follicular and perifollicular areas of lymph nodes. Infiltration by macrophages was also recorded. By IHC analysis, the cytoplasm of macrophages was shown to contain a large amount of the ORF2-coded Cap antigen of PCV2. Lymphocyte depletion and large numbers of macrophages were recorded in the tonsils, spleen, intestinal lymphatic tissue, Peyer's patches and ileocaecal valve. The presence of typical granulomatous lesions with multinuclear giant cells (MGCs) was also recorded in the lymphatic tissue. Cap antigen was shown to be present in macrophages and less often in lymphocytes. 相似文献