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991.
试验选用体长(8.16±0.14)cm,体重(7.91±0.12)g的岩原鲤(Procypris rabaudi),经76 d的养殖试验,研究添加Fe、Zn、Cu不同组合水平的7组实用日粮对岩原鲤生长、体营养组成和血清生化指标的影响。试验鱼种630尾,随机分成7个组,每组3个重复,每个重复30尾。结果显示:饲料中添加Fe、Zn、Cu能够提高岩原鲤的生长性能和抗氧化能能力。当Fe、Zn、Cu的添加量分别为140、50、5 mg/kg时,增重率、特定生长率、饲料蛋白质效率、超氧化物歧化酶(SOD)活性和总抗氧化能力(T-AOC)最高,饲料系数最低。适量添加Fe、Zn、Cu能够显著提高岩原鲤的免疫能力。当Fe、Zn、Cu的添加量分别为200、90、4 mg/kg时岩原鲤血清溶菌酶活力最高。结果表明,岩原鲤饲料中Fe、Zn、Cu的最适添加量分别为140、50、5 mg/kg。 相似文献
992.
We examined 5-year basal area growth of nearly 2600 trees in stem-mapped plots at five locations differing in site characteristics, species composition, and management history on the Olympic Peninsula in Western Washington, USA. Our objectives were to determine if internal edges, the boundaries within the stand between components of the variable-density thinning, influenced individual tree growth, and whether incorporation of individual tree local competition indices in growth prediction models could account for treatment and edge effects. Treatment significantly affected tree growth at all sites, with trees in the thinned matrix displaying on average over 25% greater basal area growth than trees in unthinned patches. Proximity to canopy gaps created as part of the variable-density thinning increased basal area growth of trees in the thinned matrix by nearly 11%. In addition, growth of trees close to skid trails was 11% greater than trees located away from the trails. Past thinning history, and its effect on initial stocking rate, appeared to affect the magnitude of the edge effects. Blocks that had received earlier commercial thinnings, and thus had lower stocking at the onset of the study, displayed lower growth responses than previously unthinned blocks. Including local competition indices in the models generally reduced growth prediction error; however, the indices examined did not fully account for treatment or edge effects. Our results suggest that not accounting for internal edges in spatially complex stands could result in errors in projected growth of trees, although these edge effects are highly variable. Failure to account for the effects of internal edges could affect not just estimates of future stand yield, but also projections of future stand structure. 相似文献
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995.
由于卧龙山庄原规划已时过境迁,已经不能满足需要,因而急需进行重新规划和对规划后的方案进行系统评价。该文通过实地调查、GPS定位相结合的方法查清了现有旅游资源并在此基础上进行了规划,然后运用景观生态学方法对规划后的方案进行了评价。该文规划种植了酸枣、冬枣、梨枣、月光枣、野菜、柿子、欧李,改变了蔬菜园的种植种类;增加了杜梨、栾树和红叶臭椿的种植面积;规划了生态集雨工程示范点、火箭消雷展览室、卧龙禅寺、金鱼池、观鱼长廊、商店、观景亭、道路、停车场和厕所等。用斑块水平和景观水平上的景观指数作为规划方案评价的数量指标,对规划后的效果进行评定,认为规划后虽然景观破碎化指数提高了,但景观类型集中度加强;景观多样性指数、优势度指数、丰富度均提高了,美学质量得到改善,旅游设施更为完善,游览期更长;同时认为这种评价方法在规划方案筛选中具有一定的可行性和参考性。 相似文献
996.
Plants belonging to the family Annonaceae have been commonly described in traditional medicine as remedies against head lice, and for their insecticidal properties. Characteristic constituents from a few genera of these plants are the annonaceous acetogenins. Fourteen annonaceous acetogenins have been isolated from our Argentine collection of the seeds of A. cherimolia. We report herein the antifeedant and insecticidal effects of nine of those acetogenins on Spodoptera frugiperda (J. E. Smith). The acetogenin squamocin, one of the major constituents of the extract, displayed toxic effects on early larval instars when incorporated to the larval diet at a dose of 50 μg per g of diet. The remaining annonaceous acetogenins tested, itrabin, asimicin, neoanonin, cherimolin-1, cherimolin-2, almuñequin, motrilin, and tucumanin produced pupal mortality and adult malformations leading to death, when incorporated to the larval diet at the same dose. The evaluation of indices of food consumption, growth, and food utilization indicated that squamocin was the only tested acetogenin to produce significant decrease in the growth rate and to reduce the efficiency with which larvae converted ingested food into biomass. All the acetogenins produced more than 80% pupal mortality with no dependence on the position of the THF rings or the number and location of the OH groups. 相似文献
997.
Adaptation of soil quality indices and application to three tillage systems in southern Illinois 总被引:2,自引:0,他引:2
Sustainability of agricultural management systems has become an issue of wide public concern and international debate. One result is that soil quality assessment has been suggested as a tool for evaluating sustainability of soil and crop management practices. Our objective was to adapt a soil quality index to assess the effects of three long-term tillage systems on sloping Grantsburg silt loam soil. Soil quality was evaluated using a framework that included three soil functions: (1) resist erosion (water relations), (2) provide plant nutrients (nutrient relations), and (3) provide a favorable root environment (rooting relations). A score for each of these functions was computed using measurements (indicators) that were normalized with one of the three (more is better, optimum, or worse) scoring functions. Six different indices were developed from a basic framework. Modifications included changing the weighting factors, threshold limits, or type of scoring function applied to indicators, and the addition of air-filled and water storage porosity to the nutrient and rooting relations functions. Changing threshold limits and the type of scoring function used for surface residue improved the correlation between water relations and soil loss. The addition of porosity indicators increased the sensitivity of nutrient and rooting relations functions to yield and cone index, respectively, and resulted in a better correlation between porosity indicators and plant population. Computing soil quality indices helped to combine different soil properties and processes into a simple tool that explained changes in complex soil properties in response to different tillage practices. This supports previous studies suggesting that computing soil quality indices and functions could be useful for selecting management practices to maintain or improve soil quality. Our results demonstrated that adjusting threshold limits for local conditions can make the function ratings more or less sensitive to the management practices being evaluated. 相似文献
998.
[目的]研究代乳料对羔羊生产性能及血液生化指标的影响,探讨羔羊早期断奶的可行性。[方法]将37只10~15日龄的白头萨福克(♂)×小尾寒羊(♀)F1羔羊随机分为A、B、C、D 4个组进行试验。其中,A、B、C 3组羔羊分别饲喂3种不同的代乳料;D组羔羊为对照组,不断奶,随母羊哺乳。分别测定各组的生产性能指标及血液生化指标。[结果]生产性能指标:10~15日龄时,B、C组日增重显著低于D组(P<0.05),而A组与D组间差异不显著;16~25、26~35日龄各组羔羊日增重均无显著差异;46~55日龄时,试验组羔羊日增重显著高于对照组(P<0.05)。血液生化指标:B组和C组的血浆尿素氮(PUN)显著高于A组(P<0.05),B组和C组间差异不显著;各组中血浆白蛋白(ALB)含量比较接近,无显著差异;B组总蛋白(TP)含量有高于A组和C组的趋势,但差异不显著;A、B、C 3组间总氨基酸浓度差异不显著。[结论]用代乳料饲喂羔羊并实现羔羊的早期断奶是可行的。 相似文献
999.
1000.
[目的]通过研究水分对大芒幼苗生长性状和几个生理指标的影响,评价大芒的抗旱性。[方法]采用盆栽方法,设置4个土壤水分梯度(对照、轻度水分胁迫、中度水分胁迫和重度水分胁迫)。[结果]水分胁迫对大芒的生长性状和生理特性影响显著。随着水分胁迫程度的加重和时间的延长,大芒的株高在整个胁迫期间持续上升,净光合速率均呈下降趋势,蒸腾速率日变化均为先升后降的趋势,相对含水量和根系活力均呈下降趋势,但都维持在较高水平。[结论]大芒具有一定的抗旱能力。 相似文献