全文获取类型
收费全文 | 188篇 |
免费 | 32篇 |
专业分类
林业 | 29篇 |
农学 | 11篇 |
基础科学 | 6篇 |
67篇 | |
综合类 | 3篇 |
农作物 | 12篇 |
水产渔业 | 24篇 |
畜牧兽医 | 41篇 |
园艺 | 3篇 |
植物保护 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 28篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 32篇 |
2012年 | 12篇 |
2011年 | 5篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1983年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1970年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有220条查询结果,搜索用时 31 毫秒
61.
Petr Baldrian Věra Merhautová Tomáš Cajthaml Mirka Petránková Jaroslav Šnajdr 《Biology and Fertility of Soils》2010,46(7):717-726
The small-scale distribution of activities of extracellular laccase, Mn-peroxidase, endoglucanase, cellobiohydrolase, β-glucosidase,
endoxylanase, β-xylosidase, chitinase, and acid phosphatase were studied in the litter (L) and organic (H) horizons of Quercus petraea forest soil and related to the distribution of microbial biomass. Geostatistical analysis showed that the spatial autocorrelation
of the enzyme activities and soil microbial biomass measured as phospholipid fatty acids (PLFA) and ergosterol content occurred
at similar scales, typically in the range of tens of centimeters. The size of the spatial structures differed between the
L and H horizons; for most of the studied enzymatic processes, litter exhibited a higher spatial variability (smaller autocorrelation
distances). The distribution of several enzymes, including laccase, Mn-peroxidase, and some hydrolases, reflected the distribution
of fungal biomass. Polysaccharide hydrolases exhibited similar spatial distribution patterns in the L horizon, and their activity coincided with a high fungal/bacterial biomass ratio. 相似文献
62.
D. Vašková J. Špak M.M. Klerks C.D. Schoen J.R. Thompson W. Jelkmann 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(2):213-221
An assay for the detection of Strawberry vein banding virus (SVBV) in Fragaria spp. based on nucleic acid sequence based amplification (NASBA) and real-time detection using molecular beacons (real-time NASBA) is described. This assay was compared both with biological indexing, the current method for certification of SVBV, and a newly optimised PCR-based detection method. Performance of the assay was tested on three SVBV isolates in Fragaria indicator plants and 317 field strawberries from five European countries. The assay was shown to be SVBV-specific, testing negative for other common aphid-borne strawberry viruses. The virus was detected in purified total RNA preparations diluted a millionfold, which is an amount equivalent to 1ng of fresh material. The real-time NASBA method developed here offers the potential of a fast, sensitive and reliable approach for the routine diagnosis of strawberry stock material. 相似文献
63.
Miroslav Glasa Véronique Marie-Jeanne Gérard Labonne Zdeno Šubr Otakar Kúdela Jean-Bernard Quiot 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(9):843-853
The isolate BOR-3, collected in Slovakia in 1996, was recently identified as a natural recombinant between an M and D type of Plum pox virus (PPV). Biological assays demonstrated its capacity to be aphid- and graft-transmitted to various Prunus spp. hosts. A study was carried out to determine the further presence of PPV recombinants in two epidemiologically distinct areas – Slovakia and France. Tools based on PPV-M and D subgroup typing, targeting P3–6K1, CI and CP regions of the PPV genome were used for recombinant identification. Closely related recombinant variants were detected in different Prunus spp. during a survey conducted in Slovakia in 2001, but not within a set of selected PPV isolates from France collected between 1985 and 2001. Sequence analysis of the (Cter)NIb–(Nter)CP region of 10 recombinant isolates from Slovakia showed their high homology, reaching more than 98%. All the recombinant isolates shared the same recombination breakpoint situated in the C terminus of the NIb gene. Our study demonstrates that the PPV recombinants are viable and competitive with conventional PPV-M and D isolates. The present work indicates that the occurrence of recombinants within PPV isolates might be more common than previously assumed. 相似文献
64.
It has become accepted that the horse cannot see directly in front when the nose is lowered and must therefore rely on the rider. We tested the hypothesis that this conclusion would be correct only if the horse did not adjust the eyeball horizontal axis to changes of the head position. The results of the present study suggest that it is unlikely that horses have limited vision in relation to their head position when driven by the rider, and that the horse maintains the optimal horizontal eyeball position regardless of head position relative to the ground. 相似文献
65.
66.
Effect of soil CO2 concentration on microbial biomass 总被引:1,自引:0,他引:1
The effect of increasing soil CO2 concentration was studied in six different soils. The soils were incubated in ambient air (0.05 vol.% CO2) or in air enriched with CO2 (up to 5.0 vol.% CO2). Carbon dioxide evolution, microbial biomass, growth or death rate quotients and glucose decay rate were measured at 6,
12 and 24 h of CO2 exposure. The decrease in soil respiration ranged from 7% to 78% and was followed by a decrease in microbial biomass by 10–60%
in most cases. High CO2 treatments did not affect glucose decay rate but the portion of Cgluc mineralized to CO2 was lowered and a larger portion of Cgluc remained in soils. This carbon was not utilized by soil microorganisms.
Received: 30 August 1996 相似文献
67.
J. Šebesta 《Euphytica》1979,28(3):807-809
Summary In oat cv. Delphin (Bonda x Carstens Vii) two complementary genes were found conferring resistance to sixteen cultures of ten crown rust (Puccinia coronata
Cda. var. avenae
Fraser ET Led.) races. The complementary genes showed full dominance to eight races and incomplete dominance to two races. 相似文献
68.
Properties and bioavailability of particulate and mineral‐associated organic matter in Arctic permafrost soils,Lower Kolyma Region,Russia 下载免费PDF全文
N. Gentsch R. Mikutta O. Shibistova B. Wild J. Schnecker A. Richter T. Urich A. Gittel H. Šantrůčková J. Bárta N. Lashchinskiy C. W. Mueller R. Fuß G. Guggenberger 《European Journal of Soil Science》2015,66(4):722-734
Permafrost degradation may cause strong feedbacks of arctic ecosystems to global warming, but this will depend on if, and to what extent, organic matter (OM) is protected against biodegradation by mechanisms other than freezing and anoxia. Here, we report on the amount, chemical composition and bioavailability of particulate (POM) and mineral‐associated OM (MOM) in permafrost soils of the East Siberian Arctic. The average total organic carbon (OC) stock across all soils was 24.0 ± 6.7 kg m?2 within 100 cm soil depth. Density fractionation (density cut‐off 1.6 g cm?3) revealed that 54 ± 16% of the total soil OC and 64 ± 18% of OC in subsoil horizons was bound to minerals. As well as sorption of OM to clay‐sized minerals (R2 = 0.80; P < 0.01), co‐precipitation of OM with hydrolyzable metals may also transfer carbon into the mineral‐bound fraction. Carbon:nitrogen ratios, stable carbon and nitrogen isotopes, 13C‐NMR and X‐ray photoelectron spectroscopy showed that OM is transformed in permafrost soils, which is a prerequisite for the formation of mineral‐organic associations. Mineral‐associated OM in deeper soil was enriched in 13C and 15N, and had narrow C:N and large alkyl C:(O‐/N‐alkyl C) ratios, indicating an advanced stage of decomposition. Despite being up to several thousands of years old, when incubated under favourable conditions (60% water‐holding capacity, 15°C, adequate nutrients, 90 days), only 1.5–5% of the mineral‐associated OC was released as CO2. In the topsoils, POM had the largest mineralization but was even less bioavailable than the MOM in subsoil horizons. Our results suggest that the formation of mineral‐organic associations acts as an important additional factor in the stabilization of OM in permafrost soils. Although the majority of MOM was not prone to decomposition under favourable conditions, mineral‐organic associations host a readily accessible carbon fraction, which may actively participate in ecosystem carbon exchange. 相似文献
69.
The concentrations of selected metals—Cr, Ni, Cu, Zn, Cd, and Pb—were determined in the samples of Hypogymnia physodes lichen and Pleurozium schreberi moss collected in Polish and Czech Euroregions Praded and Glacensis. More specifically, the samples were collected in Bory Stobrawskie, Bory Niemodlińskie, and Kotlina K?odzka (Poland) and in Jeseniki (Czech Republic). The concentration of metals in the samples was measured using the atomic absorption spectrometry (flame AAS technique and electrothermal atomization AAS technique). The results were used to calculate the comparison factor (CF) that quantifies the difference in concentration of a given bioavailable analyte × accumulated in lichens and mosses: CF?=?2 (c x,lichen ? c x,moss) (c x,lichen + c x,moss)?1. The values of CF greater than 0.62 indicate the most probable location of heavy metals deposited in the considered area. In this work, the method was used to show a significant contribution of urban emissions to the deposition of heavy metals in the area of Bory Stobrawskie and in the vicinity of K?odzko City. 相似文献
70.
The effects of selenium (Se) (VI) soil fertilization with 2 μg Se L?1 or foliar spraying twice with 20 mg Se L?1 in the form of sodium (Na) selenate on the physiological and biochemical characteristics of cabbage plants were studied. The ability of the plants to take up Se and translocate it to different parts of the plants was also studied. Despite the high concentration of Se in the foliar solution, there was no effect on photosynthesis, transpiration rate, photochemical efficiency of PSII, or electron transport system activity. The amount of chlorophyll and anthocyanins were unchanged. At harvest, the concentration of Se in control plants was lower than 100 ng Se g?1 dry weight (DW), while plants treated with 20 mg Se L?1 contained 5500 ng Se g?1. Selenium enriched cabbage could be used in human nutrition. The tolerance of cabbage to Se could be explained by the formation of insoluble compounds that are not available for the plant. 相似文献