全文获取类型
收费全文 | 776篇 |
免费 | 18篇 |
国内免费 | 3篇 |
专业分类
林业 | 78篇 |
农学 | 35篇 |
基础科学 | 2篇 |
328篇 | |
综合类 | 88篇 |
农作物 | 14篇 |
水产渔业 | 11篇 |
畜牧兽医 | 194篇 |
园艺 | 9篇 |
植物保护 | 38篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 47篇 |
2012年 | 38篇 |
2011年 | 50篇 |
2010年 | 22篇 |
2009年 | 25篇 |
2008年 | 41篇 |
2007年 | 51篇 |
2006年 | 50篇 |
2005年 | 54篇 |
2004年 | 33篇 |
2003年 | 32篇 |
2002年 | 40篇 |
2001年 | 15篇 |
2000年 | 26篇 |
1999年 | 17篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 5篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1978年 | 2篇 |
1974年 | 3篇 |
1973年 | 6篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1966年 | 3篇 |
1958年 | 2篇 |
1955年 | 2篇 |
1863年 | 1篇 |
排序方式: 共有797条查询结果,搜索用时 15 毫秒
111.
The effects and residual effects of farmyard manure (FYM), straw fertilization and mineral N fertilization were investigated in Field F of the long‐term fertilization trial in Halle (Saale), Germany. With sufficient mineral N fertilization, FYM and straw did not directly affect yield. The application of FYM alone increased the yield of potato less than those of silage maize and sugar beet. With low mineral N fertilization, however, residual effects of FYM, applied to root crops, were observed in the following cereal crops. Application of more mineral N to root crops had the same residual effects. In case of omitted mineral N fertilization, the humus content of the soil decreased rapidly. This implies that almost no stable humic material had been accumulated by application of FYM and straw. The calculated N loss increased with enhanced organic fertilization. In case of mineral N fertilization the content of organic C (Corg) was slightly higher (1.4 to 1.5%) than without any N fertilization (1.3%). FYM and straw (with same amounts of dry matter) likewise enhanced the Corg‐content and, consequently, the content of decomposable C (Cdec). In general, organic fertilizers should not be applied in too large amounts to avoid N losses. 相似文献
112.
Lothar Schmidt Kristina Warnstorff Hannelore Drfel Peter Leinweber Henning Lange Wolfgang Merbach 《植物养料与土壤学杂志》2000,163(6):639-648
Six forms of fertilizers and three rotations have been examined for 120 years in the ”︁Eternal Rye trial” in Halle (central German arid region, Haplic Phaeozem on sandy loess). Rank analysis, trend analysis and a new component model have been found to be suitable statistical methods to evaluate long‐term results without true replications. In this trial it was shown that mineral fertilization maintains like farmyard manuring the yield potential although at lower content of soil organic matter (SOM). Without fertilization, yield decline was greater with potato and silage maize than winter rye (Secale cereale L.). Deficiencies in N fertilization lead immediately, and in PK supply after more than 20 years, to a significant yield decrease which could be quickly compensated by full fertilization. Rye and maize monocultures also resulted in yield decreases. The establishing of new steady states in the turnover of SOM took about 50 years after changes in fertilization. Contrary to rye monoculture, both silage maize monoculture and potato alternating with winter rye caused considerable decomposition of SOM. According to analytical pyrolysis (Py‐FIMS and Py‐GC/MS), fertilization affects the SOM composition more than rotation. Without fertilization, a higher percentage of thermically stable SOM remained in comparison to the FYM soils. The introduction of potato into the rotation enhanced the content of easily decomposable SOM. 相似文献
113.
Wolfgang Merbach Joachim Garz Wilfried Schliephake Hermann Stumpe Lothar Schmidt 《植物养料与土壤学杂志》2000,163(6):629-638
Six of originally eight long‐term trials in Halle (Saale), Germany, are still continuing. Five are situated at Julius‐Kühn‐Feld, an experimental station launched by Julius Kühn in Halle in 1866. Apart from the Eternal Rye trial established in 1878, those are phosphorus, potassium, lime, and organic fertilization long‐term trials, all being launched by Karl Schmalfuß in 1949. Other long‐term trials have been terminated, but data are available on the effects of nitrogen fertilization and the physiological reaction of fertilizers. Another long‐term trial in Halle (Adam‐Kuckhoff‐Straße 17b) investigates the influence of fertilization on soil formation from loess. Up to now, the major results are as follows: 1. Changes in soil‐ecological properties due to fertilization and rotation were only evident after 30 years, and new steady states sometimes took 70 years to occur. 2. In the long term, the C‐ and N‐contents of the soil largely depend on the amount of hardly decomposable organic matter applied with organic fertilization. High mineral‐N doses, with consequent high crop and root residues, increased the humus content of the soil. 3. Mineral fertilization can replace organic fertilization in terms of sustainable yield capacity provided equal nutrient amounts were applied. 4. The high P‐supply ability of the soil in Halle could not be explained by traditional soil analysis methods of calculating plant‐available P. With some restrictions, the same is valid for K. 5. At the experimental site, soluble salts (nitrate, sulphate) accumulated in the subsoil. 6. A regular lime demand of central German chernozems could be proved, especially in case of low soil organic matter (SOM) and physiologically acid fertilization. 相似文献
114.
Wolfgang Wilcke Kai Uwe Totsche Markus Krber Jozef Kobza Wolfgang Zech 《植物养料与土壤学杂志》2000,163(5):503-508
Depositions originating from a central Slovak Al smelter may increase metal solubility in adjacent soils because they contain F (mainly HF). The reason for fluoro‐mobilization of metals may be the formation of soluble fluoro‐metal complexes or the mobilization of organic matter and subsequent formation of organo‐metal complexes. The objectives of our work were (1) to assess the extent of metal mobilization by fluoride in a Slovak Lithic Eutrochrept affected by the emissions of an Al smelter and (2) to model the dissolved metal species with the help of a chemical equilibrium model (MINEQL+). The O (Moder), A, and B horizons were equilibrated with solutions at F concentrations of 0, 0.9, 2.7, and 9.0 mmol l—1. In the extracts, the concentrations of Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Zn, dissolved organic carbon (DOC), free and complexed F, and the pH and electrical conductivity (EC) were determined. The heavy metal concentrations in the O horizon (Cd: 0.99, Cr: 18.0, Cu: 44, Ni: 26, Pb: 110, and Zn: 84 mg kg—1) were 2.5 to 9 times larger than those in the A and B horizons. The concentrations of H2O‐soluble F decreased from the O (261 mg kg—1) to the A (103 mg kg—1) and B horizon (92 mg kg—1). In batch experiments increasing addition of F increased the equilibrium concentrations of Al, Cr, Cu, Fe, Ni, Pb, and DOC in all samples, of Cd in the A, and of K in the B horizon. At the same time the concentrations of complexed F and pH increased whereas EC decreased. Chemical equilibrium modelling indicated that the mobilizing effect of F resulted from the formation of fluoro‐Al complexes and organo‐complexes of all other metals. 相似文献
115.
A. Séraphin Zanklan Heiko C. Becker Marten Sørensen Elke Pawelzik Wolfgang J. Grüneberg 《Genetic Resources and Crop Evolution》2018,65(3):811-843
Yam bean [Pachyrhizus DC.] is a legume genus of the subtribe Glycininae with three root crop species [P. erosus (L.) Urban, P. tuberosus (Lam.) Spreng., and P. ahipa (Wedd.) Parodi]. Two of the four cultivar groups found in P. tuberosus were studied: the roots of ‘Ashipa’ cultivars with low root dry matter (DM) content similar to P. erosus and P. ahipa are traditionally consumed raw as fruits, whereas ‘Chuin’ cultivars with high root DM content are cooked and consumed like manioc roots. Interspecific hybrids between yam bean species are generally completely fertile. This study examines the genetic diversity of the three crop species, their potentials for breeding and the identification of useful traits to differentiate among yam bean genotypes and accessions. In total, 34 entries (genotypes and accessions) were grown during 2000?2001 at two locations in Benin, West Africa, and 75 morphological and agronomical traits, encompassing 50 quantitative and 25 qualitative characters were measured. Diversity between entries was analyzed using principal component analysis, cluster analysis, multivariate analysis of variance and discriminant function analysis. Furthermore, phenotypic variation within and among species was investigated. Intra- and interspecific phenotypic diversity was quantified using the Shannon–Weaver diversity index. A character discard was tested by variance component estimations and multiple regression analysis. Quantitative trait variation ranged from 0.81 (for total harvest index) to 49.35% (for no. of storage roots per plant). Interspecific phenotypic variation was higher than intraspecific for quantitative traits in contrast to qualitative characters. Phenotypic variation was higher in overall for quantitative than qualitative traits. In general, intraspecific phenotypic variation ranged from 0.00 to 82.61%, and from 0.00 to 80.03% for quantitative and qualitative traits, respectively. Interspecific phenotypic variation ranged from 0.00 to 95.02%, and 0.00?81.58% for the two trait types, respectively. The Shannon–Weaver diversity index (H′) was in general high and over 0.80 for most of the trait. Diversity within P. tuberosus was higher than within P. erosus and P. ahipa. Across the 50 quantitative and 25 qualitative traits, the Shannon–Weaver diversity index of intra- and interspecific variation was around 0.83 and 0.51, respectively and was lower for qualitative than for quantitative traits. Monomorphism was observed in eight qualitative traits and one quantitative character. The first, second and third principal components explained, respectively, 39.1, 21.3 and 8.3% of the total variation in all traits. Pachyrhizus erosus, P. ahipa, and P. tuberosus (‘Chuin’ and ‘Ashipa’) were clearly separated from each other by these analyses. Multivariate analysis of variance indicates significant differences between Pachyrhizus species for all individual or grouped traits. Discriminant function analysis revealed that the first two discriminant functions were almost significant. Biases due to unbalanced sample size used per species were small. Within each species a similar amount of diversity was observed and was determinable to 70% by only ten traits. We conclude that the cultivated yam bean species represent distinct genepools and each exhibits similarly large amounts of genetic diversity. 相似文献
116.
Dirk Hoffmeister Guido Waldhoff Wolfgang Korres Constanze Curdt Georg Bareth 《Precision Agriculture》2016,17(3):296-312
Information on crop height, crop growth and biomass distribution is important for crop management and environmental modelling. For the determination of these parameters, terrestrial laser scanning in combination with real-time kinematic GPS (RTK–GPS) measurements was conducted in a multi-temporal approach in two consecutive years within a single field. Therefore, a time-of-flight laser scanner was mounted on a tripod. For georeferencing of the point clouds, all eight to nine positions of the laser scanner and several reflective targets were measured by RTK–GPS. The surveys were carried out three to four times during the growing periods of 2008 (sugar-beet) and 2009 (mainly winter barley). Crop surface models were established for every survey date with a horizontal resolution of 1 m, which can be used to derive maps of plant height and plant growth. The detected crop heights were consistent with observations from panoramic images and manual measurements (R2 = 0.53, RMSE = 0.1 m). Topographic and soil parameters were used for statistical analysis of the detected variability of crop height and significant correlations were found. Regression analysis (R2 < 0.31) emphasized the uncertainty of basic relations between the selected parameters and crop height variability within one field. Likewise, these patterns compared with the normalized difference vegetation index (NDVI) derived from satellite imagery show only minor significant correlations (r < 0.44). 相似文献
117.
118.
Binding of imidacloprid,thiamethoxam and N‐desmethylthiamethoxam to nicotinic receptors of Myzus persicae: pharmacological profiling using neonicotinoids,natural agonists and antagonists
下载免费PDF全文
![点击此处可从《Pest management science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
119.
Journal of Plant Diseases and Protection - Roots, collars and rhizosphere soils from diseased boxwood saplings (Buxus sempervirens) from German and Romanian nurseries were shown to be colonized by... 相似文献
120.
Weber K Germann PG Iwata H Hardisty J Kaufmann W Rosenbruch M 《Journal of toxicologic pathology》2009,22(4):229-246
Specific regions in the rat larynx exhibit cellular changes in response to inhaled xenobiotics. These regions include the base of the epiglottis, ventral pouch, and medial surfaces of the vocal processes of the arytenoid cartilages. 1 , 2 In order to collect information on the usefulness of trimming techniques, the influence of different vehicles, the impact of different application routes in toxicity studies, and differences between induced vs. spontaneous lesions, the data obtained from a large number of inhalation and non-inhalation studies performed in Wistar RCCHan(TM): Wist rats at Harlan Laboratories Ltd Switzerland, all evaluated or reviewed by the same pathologist, were compiled for a detailed review. The value of different trimming techniques was deemed to be greatest for transverse and sagittolongitudinal section techniques, as compared to horizontolongitudinally section techniques. The comparison of lesions encountered in control rats of inhalation studies treated with different vehicles did not reveal differences in the type, distribution pattern, incidence and/or severity of spontaneous lesions. The types of lesions were also independent of different application routes in non-inhalation studies compared to inhalation studies. The pattern of spontaneous lesions in the rodent larynx was determined by degenerative and inflammatory lesions starting most often in the submucosal glands by desiccated secretion followed by mineralization and local inflammation or were induced by impacted foreign bodies. Squamous metaplasia was recorded in the respiratory epithelium overlaying the ventral gland as a spontaneous lesion in male Wistar rats from inhalation studies with a maxim of 20.0% in an inhalation oncogenicity study. Induced metaplastic changes recorded in the larynx were reversible. Other induced lesions in inhalation studies consisted of submucosal edema, necrosis, inflammation and/or granuloma. Induced lesions in non-inhalation studies were found to be exclusively related to reflux laryngitis or food impaction. It is concluded, that in rodents induced lesions of the larynx differ in type, distribution pattern, severity and incidence from spontaneous lesions. 相似文献