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51.
Anjorin Godwin Ajiboye Adeleke Joseph Ogunwale 《Archives of Agronomy and Soil Science》2013,59(2):247-258
The potassium status of soils developed over talc overburden in a southern Guinea savanna of Nigeria was evaluated using exchangeable, acid extractable, total and residual potassium values in particle-size fractions. Soil samples collected from genetic horizons of six profile pits at Kampe Forest Reserve were separated into sand, silt and clay fractions. Exchangeable K, acid-extractable K, total K and residual K were determined in these fractions. Reserved K values were similar to those of mobile K, but lower than total and residual K, whereas exchangeable K showed the lowest values. Total K was >25 cmol kg?1 in all the profiles; reserved K ranged from 9.26 to 24.45 cmol kg?1 and mobile K ranged from 5.12 to 29.57 cmol kg?1. Exchangeable K accounted for <1% of total K and ranged from 0.20 to 0.50 cmol kg?1. In most cases, the clay fraction of the soils had the highest values for all potassium forms, followed by the silt fraction, while the sand fraction had the lowest values for these forms of potassium. 相似文献
52.
53.
The analysis of saltwater intrusion through Komesu underground dam and water quality management for salinity 总被引:2,自引:1,他引:1
The Komesu underground dam is the first full-scale underground dam constructed to prevent saltwater intrusion in Japan. Although
the cutoff wall of the dam effectively reduces the movement of saltwater into the reservoir area, saltwater masses remained
behind the dam at the time of its completion, and saltwater can intrude beneath and diffuse through the wall, particularly
when the reservoir level is below the sea level because of high pumping levels during the drought years. Therefore, it is
necessary to estimate in advance whether the saltwater concentration in the pumped water is likely to exceed or not the permissible
salinity level because of an increase in the residual saltwater mass as a result of saltwater intrusion and to take necessary
measures to suitably manage the saltwater level behind the dam. To analyze saltwater intrusion, we first selected the optimal
program suitable for the analysis of saltwater intrusion. Second, we examined the longitudinal dispersivity and the effect
of the cone of depression around the pumping wells. Then we analyzed saltwater intrusion into the reservoir area in detail
by using a two-dimensional convective–dispersive analysis. The results of the analysis make it possible to improve management
of saltwater in the reservoir area behind the underground dam. 相似文献
54.
Validating a segment on the short arm of chromosome 6 responsible for genetic variation in the hull silicon content and yield traits of rice 总被引:2,自引:0,他引:2
Wei-Min Dai Ke-Qin Zhang Ji-Rong Wu Lei Wang Bin-Wu Duan Kang-Le Zheng Run Cai Jie-Yun Zhuang 《Euphytica》2008,160(3):317-324
Rice is a typical silicon-accumulating plant and the beneficial effect of silicon on rice has long been recognized. In a previous
study using 244 recombinant inbred lines (RILs) of an indica rice cross, Zhenshan 97B/Milyang 46 grown in 2003, four QTLs
were detected for hull silicon content. QTL qHUS-6 had the largest effect among these, and the same interval also had significant effects on yield traits in the same population.
The primary objective of this study was to validate the QTL effect in this region on HUS and yield traits. The same RIL population
and another RIL population of lower heterogeneity were grown in 2004. QTL qHUS-6 was found to have significant additive effects on hull silicon content with a consistent direction in the two populations.
From a residual heterozygous line selected from RILs of the same cross, 15 F2:3 lines that differed only in a 2.15-Mb segment extending from RM587 to RM6119 on the short arm of chromosome 6 were derived.
In these lines, qHUS-6 displayed a major effect, so did QTLs for yield traits previously detected in the same region. Two more QTLs for HUS detected
in 2003, qHUS-1-1 and qHUS-1-2, also had consistent effects in the Zhenshan 97B/Milyang 46 RIL population in 2004. Thus this study verified three candidate
regions for fine mapping HUS QTLs and determining the genetic relationship between silicon content and yield traits in rice. 相似文献
55.
Soil microorganisms contribute to the formation of non-living soil organic matter (SOM) by metabolic transformation of plant-derived material. After cell death, their biomass components with a specific molecular character become incorporated into SOM imprinting its chemical properties, although this process has not yet been quantified. In order to elucidate the contribution to SOM formation, we investigated the fate of gram-negative bacterial model biomass (Escherichia coli usually introduced into soil with manure or feces) during incubation of soil with isotopically (13C) and genetically (lux gene) labeled cells. The decline of living cells was monitored by the loss of bioluminescence. The carbon turnover and mineralization was balanced by bulk soil stable isotope analysis, and the persistence of nucleic acids was investigated by PCR amplification of the lux gene. During incubation, the number of viable E. coli cells decreased rapidly (99.9% within the first 42 d) serving as substrate for other microorganisms or for the formation of SOM, and bioluminescent cells could only be detected during the first 56 d. However, the lux gene was still detected after 224 d, which indicates stabilization of DNA in SOM. Although the survival of E. coli in soil is limited, only about 65% of the added labeled biomass carbon was mineralized to 13CO2 and 51% remained in soil after 224 d with an average 13C recovery of 117%. The amount of 13C found in the PLFA representative of living cells had decreased to 25% of the initial value, suggesting a proportional decrease of the 13C in the soil microbial biomass. The extent of this decrease is higher than the mineralization of the bulk E. coli C and thus the difference of around 25% has to be stabilized as metabolites, or in non-living SOM. The data provide evidence that the genetic information and a considerable part of the carbon from dying bacterial biomass were retained in both the soil microbial food web and in non-living SOM. 相似文献
56.
残膜对番茄苗期和开花坐果期生长的影响 总被引:4,自引:0,他引:4
残膜污染已成为危害农田生态系统的重要因子,不仅阻碍土壤水分和养分运移,而且影响作物生长。为探明残膜对不同生育期番茄生长的影响规律,采用小区试验方法,设置0 kg·hm-2、80 kg·hm-2、160 kg·hm-2、320 kg·hm-2、640 kg·hm-2和1 280 kg·hm-2共6种不同残膜量水平,研究残膜量对番茄苗期和开花坐果期的根系特征、地上部生长和干物质积累的影响,并采用Logistic生长模型定量分析残膜对番茄养分积累始盛期、高峰期和盛末期的影响。结果表明,残膜阻碍了番茄苗期和开花坐果期根系的生长,根体积、根长密度和根干质量密度均随残膜量增加而降低;随着残膜量增加,苗期和开花坐果期的株高和茎粗均呈减小趋势,且株高和茎粗的增长速率逐渐降低。番茄养分积累的始盛期和高峰期随残膜量增加而提前,番茄追肥的最佳时期也应提前。在番茄苗期和开花坐果期,根系、茎秆、花和幼果的干物质量均随残膜量增加而减少,而叶片的干物质量呈递增趋势。残膜对番茄苗期根系、地上部生长和干物质积累的阻碍作用高于开花坐果期。由此可见,残膜对番茄苗期的危害强于开花坐果期,且干物质积累的始盛期和高峰期均随残膜量增加而提前,加强番茄苗期水肥管理和提前水肥施加时间是减轻残膜危害的有利措施。 相似文献
57.
土壤中磺胺类抗生素的检测方法优化及残留、降解研究 总被引:3,自引:0,他引:3
优化了磺胺甲基嘧啶(SM1)、磺胺二甲嘧啶(SM2)、磺胺对甲氧嘧啶(SMT)、磺胺甲噁唑(SMZ)4种磺胺类抗生素的高效液相色谱(H PLC)检测方法,分析了广州市养殖场周边土壤中磺胺类抗生素的残留特征,并进行了2种磺胺类抗生素的土壤降解试验。结果表明,4种磺胺类抗生素分别在0.10~10μg ml-1范围内线性良好,相关系数R>0.99。确定了最佳提取液为甲醇:含EDTA的Mcllvain缓冲液=1∶1(V/V),4种磺胺类药物的检测限与回收率分别为2.9~4.7μg kg-1、83.6%~90.1%。广州市18个规模化养殖场周边土壤中磺胺类抗生素污染以SM2为主,含量为1.75μgkg-1,其它3种均未被检出。土壤中磺胺类抗生素的含量总体呈随培养时间而不断下降的趋势,SMZ的降解速率大于SM2。 相似文献
58.
59.
动物专用头孢喹诺的研究进展 总被引:2,自引:0,他引:2
头孢喹诺是动物专用的第4代头孢菌素类抗生素,具有广泛的抗菌和强大的杀菌作用。其抗菌活性极强,对临床分离的各种革兰氏阳性菌、革兰氏阴性菌的MIC50、MIC90值均较小;其药动学特点优良,吸收快,达峰时间短,生物利用度较高,药时曲线下面积较大,表现分布容积也很大;头孢喹诺毒性低,在动物的可食用组织中残留较少,安全性较高。国外已将该药应用于猪、牛的呼吸系统感染及牛乳房炎的治疗。为指导头孢喹诺在我国兽医临床上的合理应用,现对其抗菌活性、药动学、残留及毒性、临床应用等最新资料进行综述。 相似文献
60.