全文获取类型
收费全文 | 802篇 |
免费 | 48篇 |
专业分类
林业 | 80篇 |
农学 | 37篇 |
基础科学 | 6篇 |
226篇 | |
综合类 | 43篇 |
农作物 | 50篇 |
水产渔业 | 79篇 |
畜牧兽医 | 199篇 |
园艺 | 20篇 |
植物保护 | 110篇 |
出版年
2023年 | 7篇 |
2022年 | 18篇 |
2021年 | 36篇 |
2020年 | 36篇 |
2019年 | 34篇 |
2018年 | 43篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 37篇 |
2014年 | 34篇 |
2013年 | 46篇 |
2012年 | 58篇 |
2011年 | 65篇 |
2010年 | 32篇 |
2009年 | 28篇 |
2008年 | 54篇 |
2007年 | 35篇 |
2006年 | 44篇 |
2005年 | 39篇 |
2004年 | 43篇 |
2003年 | 29篇 |
2002年 | 27篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有850条查询结果,搜索用时 15 毫秒
61.
A-horizons of 48 Haplic Phaeozems and Kastanozems in plain sites of the Semiarid Argentinian Pampas under three contrasting management systems (virgin bushland, permanent pasture and continuous agriculture) were studied. Morphological characteristics, organic carbon and total nitrogen levels and E4:E6 ratios were determined on the assumption that both quantity and quality of organic matter should be related to soil texture of parent materials in this region since other soil forming factors are uniform. The more intensive land use produced an averaged decrease of 7 cm in A-horizon thickness and degradation of soil structure, but little changes in color and properties of boundaries to AC horizons. In virgin soils organic carbon and nitrogen contents correlate with silt + clay fractions (r = 0,92 and 0,99, respectively), while E4:E6-ratios are related to clay contents (r = ?0.69*) confirming the strong influence of soil texture. Agricultural-management and pasture use of soils lead to dispersion of these correlations probably because of differential influence of varying intensities of land use within each management system. Soils under continuous agriculture show lower organic carbon contents than virgin soils only at clay + silt > 40%. Eragrostis curvula-pastures seems to be more effective in restoring organic matter and nitrogen levels in sandy but not in loamy soils with respect to virgin soils. This may be due to a better efficiency of E. curvula-roots in coarse than in fine textured soils to produce humificable residues than the autochthonous grass species. 相似文献
62.
Magni C Herndl A Sironi E Scarafoni A Ballabio C Restani P Bernardini R Novembre E Vierucci A Duranti M 《Journal of agricultural and food chemistry》2005,53(11):4567-4571
The prevalence of food allergies in the world population requires integrated approaches to identify new potential allergens, especially those of plant origin. The aim of this work was the allergen in vitro analysis of Lupinus albus seed proteome, a promising food protein source, and the assessment of IgE cross-reactivities with other more diffused legume species. A combination of one- and two-dimensional gel electrophoresis and immunoblotting analyses with specific IgGs for band identification and lupin-sensitized patients' circulating IgEs for allergenicity studies has been used. Two lupin proteins, namely, conglutin gamma and 11S globulin basic subunits, strongly reacted with all patients' sera. Also, cross-reactivities with the homologous polypeptides of other legume species were observed. Otherwise, no reaction at all was detected with a 2S-type lupin protein. This global electrophoretic approach has allowed the identification of a new potential lupin allergen and confirmed the cross-reactivity among the legume 11S globulin basic subunits. 相似文献
63.
Extending applicability of the oxygen radical absorbance capacity (ORAC-fluorescein) assay 总被引:12,自引:0,他引:12
The ORAC-fluorescein (ORAC-FL) method recently validated using automatic liquid handling systems has now been adapted to manual handling and using a conventional fluorescence microplate reader. As calculated for Trolox, the precision of the method was <3.0, expressed as percent coefficient of variation. The accuracy of the method was <2.3, expressed as percent variation of the mean. The detection and quantification limits were those corresponding to 0.5- and 1-microM Trolox standard solutions, respectively. The method has been applied to 10 pure compounds (benzoic and cinnamic acids and aldehydes, flavonoids, and butylated hydroxyanisole), to 30 white, rose, and bottled- and oak-aged red wines, and to 7 commercial dietary antioxidant supplements. All samples exhibited a good linear response with concentration. As seen by other methodologies, the chemical structure of a compound determines its antioxidant activity (ORAC-FL value). Of particular interest were the results with oak-aged red wines from different vintages (1989-2002) that confirm influence of vintage, but not origin of the oak, in the antioxidant activity of wines from the same variety. Dietary antioxidant supplements presented a great variability (170-fold difference) in their antioxidant potency. This work proves applicability of the ORAC-FL assay in evaluating the antioxidant activity of diverse food samples. 相似文献
64.
Cabizza M Angioni A Melis M Cabras M Tuberoso CV Cabras P 《Journal of agricultural and food chemistry》2004,52(2):288-293
Rotenone and rotenoids (deguelin, beta-rotenolone (12a beta-hydroxyrotenone), tephrosin (12a beta-hydroxydeguelin), 12a alpha-hydroxyrotenone, and dehydrorotenone) were determined in cubè resins and formulations. Cubè resins from Lonchocarpus contain large quantities of deguelin (ca. 21.2%) and smaller quantities of tephrosin (ca. 3.5%) and beta-rotenolone (ca. 3.0%). The composition of commercial formulations may present very different rotenoid contents depending on the extracts used to prepare them. Because these rotenoids also present insecticide activity, the efficacy of these formulations may be very different. The storage stability and photodegradation of some rotenone formulations were studied. Rotenone and rotenoids are very sensitive to solar radiation, which degrades them rapidly, with half-lives in the order of a few tens of minutes. Some formulations show greater disappearance rates than that of cubè resin, indicating that not much attention has been paid to protecting the active ingredients from photodegradation in the formulation. A study on the residues on olives was also carried out to assess not only the rotenone content, but also that of the main rotenoids. At harvest, the residues of deguelin, tephrosin, and beta-rotenolone were 0.10, 0.06, and 0.10 mg/kg, respectively, very similar to rotenone (0.08 mg/kg), and though a few data indicate similar acute toxicity values for deguelin, only rotenone is taken into consideration in the legal determination of the residue. 相似文献
65.
Arruda NJ Filho JL Montenegro MC Araújo AN Silva VL 《Journal of agricultural and food chemistry》2003,51(24):6945-6948
This work refers to a very easy to implementate flow injection system with potentiometric detection for l-glutamate determination in food samples. The proposed procedure is based on measurement of carbon dioxide produced by decarboxylation of l-glutamate catalyzed by l-glutamate decarboxylase (E.C. 4.1.1.1.5) from Cucurbita maxima (pumpkin). The FI potentiometric system includes an enzymatic reactor with a length of 8 cm and thickness of 5 mm packed with 200 mg of a C. maxima outer layer cut in to small pieces. The proposed procedure allowed l-glutamate determinations in the concentration interval of 10-100 mmol L(-1) for an injected sample volume of 50 microL. A phosphate buffer (0.1 mol L(-1), pH 5.5) solution flowing at 1.4 mL min(-1) was used as the carrier solution in the system. The results obtained in the analysis of food samples revealed a relative error lower than 5% when compared with those provided by the spectrophometric reference procedure. The immobilized reactor retained its initial activity for 21 days. It was possible to measure 40 samples/h with the flow system proposed. 相似文献
66.
Application of a Balanced Scorecard System for Supporting Decision-Making in Contaminated Sites Remediation 总被引:1,自引:0,他引:1
Alberto Bezama Nóra Szarka Jürgen Wolfbauer Karl E. Lorber 《Water, air, and soil pollution》2007,181(1-4):3-16
This work introduces the development and application of a multi-goal evaluation procedure for assessing sets of remedial options that have previously been found technically suitable for managing a certain contaminated site. The construction of this decision support tool, in the form of a balanced scorecard, has followed a multi-attribute conception of the contaminated sites problem, identifying the most critical aspects considered by all stakeholders involved in contaminated sites management decisions. The developed tool has been checked in its formulation and application against an export benchmark of an Austrian remediation project. The performed evaluation allowed to identify and suggest a remedial option that best fitted the expectations of all stakeholders involved in the project. Furthermore, through the accomplishment of a sensitivity analysis it has been demonstrated that the system is stable and robust in terms of the chosen elicitation schemes, and that the preferences of the different stakeholders are influencing factors on the final result. The results and conclusions of this work present the benefits of implementing the developed balanced scorecard as a tool for supporting decision making in contaminated sites remediation projects. 相似文献
67.
Rosalinda Mendoza-Villarreal Alberto Sandoval-Rangel Valentín Robledo-Torres Adalberto Benavides-Mendoza 《Journal of plant nutrition》2015,38(1):73-82
Nitrogen (N) by form of nutrition, ammonium (NH4+) or nitrate (NO3?), affects metabolic and physiological processes of plants. In general, a high proportion of N in NH4+ form results in poor growth. Nonetheless, a number of species exhibit optimum growth when high levels of NH4+ are provided. In the present study, lisianthus [Eustoma grandiflorum (Raf.) Shinn] was grown in rockwool cultures and irrigated with nutrient solutions containing 15 mM N with varying proportions of NH4+ and NO3?. The results showed that an increase in NH4+-N form increased plant height, number of flowers and leaves, leaf area, and shoot, stem, and leaf dry weight. The proportion of NH4+ also affected leaf concentration of phosphorus, potassium (K), calcium (Ca), and magnesium (Mg), although leaf N concentration was unaffected. Potassium leaf concentration was higher when a low proportion of NH4+ was supplemented in the nutrient solution; however, plants exhibited a decrease in leaf K concentration and a decrease in leaf Ca as the proportion of NH4+-N increased. Shoot dry weight was higher with low leaf K whereas high leaf Ca was associated with high shoot dry weight. Net photosynthesis rate was higher in plants irrigated with solutions containing 75% of total N in NH4+ form than in those irrigated with solutions of 0 or 25%. The results suggest that lisianthus can tolerate high levels of NH4+, probably associated with a higher assimilation of Ca. 相似文献
68.
We conducted a longitudinal study to obtain baseline information about the health and productivity of sows and boars raised by smallholder-pig raisers in the Philippines, and test constraints and opportunities to smallholder-sow production that had been identified previously in a cross-sectional study [More, S.J., Lee, J.-A.L.M., La?ada, E.B., Taveros, A.A., Cotiw-an, B.S., 1999. Weight-for-age of growing pigs raised by smallholder farmers in the Philippines. Prev. Vet. Med. 41, 151-169]. Over 12-18 months, we collected data during monthly on-farm visits about 213 sows raised in 119 herds at 2 sites and 32 boars in 31 herds at 1 site. Sow reproductive performance was low and boars were used only infrequently (an average of 0.9 services/month). Using repeated-measure analyses, we identified sow nutrition and piglet care (such as provision of creep feed and unrestricted access to the sow) as important husbandry issues associated with increased sow productivity. 相似文献
69.
More SJ Lee JA Lañada EB Taveros AA Cotiw-an BS 《Preventive veterinary medicine》2005,70(1-2):115-131
We conducted a longitudinal study to obtain detailed baseline information about the health and productivity of unweaned piglets raised by smallholder pig raisers in the Philippines, and to identify constraints and opportunities to smallholder-piglet production. At two sites in the Philippines, we collected data about 242 litters from 173 sows in 102 herds during on-farm visits over 12-18 months. Preweaning mortality at the northern and southern sites was 17 and 9%, respectively. Of the piglet deaths at the northern site, 49% occurred within 24h of birth. Pig raisers used few of the recognised interventions known to reduce neonatal piglet mortality, although >50% of litters were given iron injections at the northern site and kept in a farrowing pen with a barrier at the southern site. Creep feeding was more common at the northern site but the nutritive value of the feeds given to piglets was low. We used repeated-measures and time-to-event analyses. Our results suggest that targeted extension (addressing, in particular, management issues relating to neonatal piglets) can contribute to increased productivity of unweaned piglets. 相似文献
70.
Guillemette?Garry Alberto?Salas Gregory?A.?ForbesEmail author Wilmer?Perez Magnolia?Santa?Cruz Rebecca?J.?Nelson 《European journal of plant pathology / European Foundation for Plant Pathology》2005,113(1):71-81
To determine whether populations of Phytophthora infestans attacking wild and cultivated potatoes in the highlands of Peru are specialized on their hosts of origin, we characterized
isolates using several neutral markers, metalaxyl resistance and for aggressiveness in a detached leaf assay. One hundred
and fifty-three isolates were collected from the northern and central highlands of Peru from different potato cultivars (both
modern and native cultivars) and from different species of wild, tuber-bearing potatoes. All the isolates analyzed belonged
to one of four clonal lineages that had been described previously in Peru: EC-1, US-1, PE-3 and PE-7. The EC-1 lineage (n = 133) was dominant and present in similar frequencies on wild and cultivated potatoes. PE-3 (n = 14) was found primarily on cultivated potatoes, with only one isolate coming from a wild host. US-1 (n = 2) and PE-7 (n = 4) were rare; all but one (PE-7) occurred on wild potatoes. Isolates from the EC-1 lineage from modern cultivars were compared
in three separate detached leaf inoculation assays with EC-1 isolates from the wild potato species S. sogarandinum, S. bill-hookerii or S. huancabambense, respectively. No significant interactions between isolate type (from wild or cultivated potato) and host type (wild or cultivated)
were measured for any assay. It appears that the pathogen genotypes in the EC-1 lineage indiscriminately attack both wild
and cultivated tuber-bearing solanaceous hosts in Peru, and breeders should be able to select for resistance using the common
EC-1 lineage. 相似文献