全文获取类型
收费全文 | 2229篇 |
免费 | 112篇 |
国内免费 | 213篇 |
专业分类
林业 | 88篇 |
农学 | 172篇 |
基础科学 | 123篇 |
371篇 | |
综合类 | 706篇 |
农作物 | 110篇 |
水产渔业 | 98篇 |
畜牧兽医 | 485篇 |
园艺 | 57篇 |
植物保护 | 344篇 |
出版年
2024年 | 12篇 |
2023年 | 58篇 |
2022年 | 87篇 |
2021年 | 84篇 |
2020年 | 117篇 |
2019年 | 144篇 |
2018年 | 97篇 |
2017年 | 106篇 |
2016年 | 129篇 |
2015年 | 121篇 |
2014年 | 126篇 |
2013年 | 145篇 |
2012年 | 161篇 |
2011年 | 170篇 |
2010年 | 140篇 |
2009年 | 135篇 |
2008年 | 101篇 |
2007年 | 98篇 |
2006年 | 90篇 |
2005年 | 73篇 |
2004年 | 48篇 |
2003年 | 48篇 |
2002年 | 31篇 |
2001年 | 35篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 27篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1962年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有2554条查询结果,搜索用时 31 毫秒
991.
992.
Response of Mung Bean (Vigna radiata (L.) R. Wilczek) to an Increasing Natural Temperature Gradient under Different Crop Management Systems
下载免费PDF全文
![点击此处可从《Journal of Agronomy and Crop Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. A. P. W. K. Malaviarachchi W. A. J. M. De Costa J. B. D. A. P. Kumara L. D. B. Suriyagoda R. M. Fonseka 《Journal of Agronomy and Crop Science》2016,202(1):51-68
Increasing temperatures pose a significant threat to crop production in the tropics. A field experiment was conducted with mung bean at three locations in Sri Lanka representing an increasing temperature gradient (24.4–30.1 °C) during two consecutive seasons to (i) determine the response of mung bean to increasing temperature and (ii) test a selected set of crop management practices aimed at decreasing essential inputs such as water, synthetic pesticides and inorganic nitrogen fertilizer. The control treatment (T1) consisted of standard crop management including irrigation, chemical crop protection and inorganic fertilizer application. Adaptation system 1 (T2) included mulching with rice straw at 8 t ha?1 with 30 % less irrigation and crop protection and nutrient management as in T1. Adaptation system 2 (T3) included crop protection using a pretested integrated pest management package with water and nutrient management as in T2. In adaptation system 3 (T4), 25 % of the crop's nitrogen requirement was given as organic manure (compost) at 0.8 t ha?1 while 75 % was given as inorganic fertilizer with water management and crop protection as in T3. Durations of both pre‐ and post‐flowering phases were reduced with increasing temperature. In the warmer (25.4–30.1 °C) yala season, seed yield (Y) of T1 decreased with increasing temperature at 366 kg ha?1 °C?1. However, in maha season, Y did not show a significant relationship across the narrower temperature gradient from 24.4 to 25.8 °C. Pooling the data from both seasons showed a second‐order polynomial response with an optimum temperature of 26.5 °C. In addition to shortened durations, reduced crop growth rates and reduced pod numbers per plant were responsible for yield reductions at higher temperatures. In yala, yields of all adaptation systems at all locations were on par with yields of the respective controls. Furthermore, yala yields of T2 and T3 were less sensitive than T1 to increasing temperatures (265 and 288 kg ha?1 °C?1). In maha, T3 and T4 had greater yields than the control at the relatively cooler site while having lower yields than the control at the warmer site. Maha yields of T2 were on par with the control at both temperature regimes. While demonstrating the significant temperature sensitivity of mung bean yields, results of the present work showed that components of the tested adaptation systems could be promoted among smallholder farmers in Asia, especially in view of their long‐term environmental benefits and contributions to sustainable agriculture in a warmer and drier future climate. 相似文献
993.
以海南省屯昌县国土局、林业局、住建局等部门提供的空间数据为基础,选取6个指标因子构建评价指标体系。利用层次分析法确定各因子权重,结合GIS空间分析技术,分析屯昌县土地生态敏感性的空间分布情况。结果表明,屯昌县生态敏感性较高的地区所占比重大,且空间分布差异明显。研究结果可为屯昌县各部门用地规划协调提供一定的实证参考。 相似文献
994.
In order to determine the pathogen and its virulence characteristics of a suspected case of piglets streptococcosis in a pig farms in Jiangxi province during September to November of 2013,a strain was isolated from the joint fluid and cerebrospinal fluid of one diseased piglet.The isolated strain was identified by culture characteristics,biochemical test,16S rDNA sequence analysis,serotype PCR test and further studied the presence of the following virulence genes:Glutamate dehydrogenase (gdh),virulent-assocciated sequence (orf2),fibronectin-binding proteins (fbps),suilysin (sly),extracellular protein factor (epf),muramidase-released protein (mrp) and antibiotic sensitivity tests.The isolated strain was identified as Streptococcus suis serotype 2 by culture characteristics,biochemical test,16S rDNA sequence analysis and serotype PCR test,and it was named as JMS2. Detection results of virulence gene showed that the distribution of main virulence genes of JMS2 were gdh+/orf2+/fbps+/sly-/epf-/mrp-,suggesting that the strain maybe not likely to be high virulence.Drug sensitivity tests showed that the JMS2 was susceptibility to β-lactams such as penicillin,amoxicillin,but resistant to azithromycin,SMZ-TMP,and so on.The result was significant for the clinical prevention and treatment of swine streptococcosis. 相似文献
995.
为探讨麦麸酯酶在农残快速检测中应用的可行性,通过比色法研究了酶抑制法检测农残时表面活性剂对固蓝B盐显色体系的增敏作用及麦麸酯酶对乐果、敌敌畏、叶蝉联、西维因、丁硫克百威和甲基对硫磷等6种农药的灵敏度和最低检测限。结果表明,阴离子表面活性剂SDS在麦麸酯酶活性测定中具有增敏作用,当浓度为4.0%时可使显色体系相对吸光度值增加152.76%;叶蝉散对麦麸酯酶的最佳抑制时间为40min,其余5种农药均为30min。麦麸酯酶对6种农药的灵敏度大小顺序为:敌敌畏叶蝉散西维因甲基对硫磷丁硫克百威乐果,IC_(50)分别为0.136、0.375、0.641、1.366、2.361、2.651mg·L~(-1)。经溴水氧化的甲基对硫磷对麦麸酯酶的敏感性显著提高,其IC_(50)值达0.089mg·L~(-1)。综上所述,麦麸酯酶在快速检测有机磷及氨基甲酸酯类农药方面具有较高的灵敏度,且来源广泛,可满足酶抑制法用酶需要。本研究丰富了麦麸酯酶在农药残留快速检测中的应用。 相似文献
996.
以FeSo4.7H2O为材料,采用共沉淀法制备氧化铁,所得主体相是γ-Fe2O3和α-Fe2O3x的混合物。材料经800-850℃热处理后,全部转变为α-Fe2O3相。以α-Fe2O3为主体材料制成的酒敏元件,掺入SnO2-ZnO二元导电陶瓷粉等材料后,可使元件的灵敏度提高20%左右,在高浓度气体下,元件对乙醇和汽油的分离效果良好,是一种抗高浓度气体冲击能力强的不掺贵金属的酒敏元件。 相似文献
997.
采用直接微分法得到了一种弹性连杆机构稳态动力响应灵敏度的计算方法,该方法克服了用差分法计算灵敏度存在的截断误差和舍入误差较大、计算精度低的缺点,是一种精确有效的弹性连杆机构稳态动力响应灵敏度计算方法。文中给出了一平面四杆机构的灵敏度分析实例来说明方法的有效性。 相似文献
998.
在表现胶冻样或水样腹泻的病死兔中分离出大肠杆菌。经生化检验、兔肠管结扎试验、小白鼠感染试验鉴定为致病性大肠杆菌,其鞭毛抗原形为K99。药敏试验结果对庆大霉素、卡那霉素、新霉素高度敏感。 相似文献
999.
Summary The utility of the modal grade as an alternative to the mean grade in the pre-selection test for screening seedlings of Coffea arabica L. for resistance to coffee berry disease (CBD) caused by Colletotrichum coffeanum NOACK sensu HINDORF was examined. Three criteria were used to compare the sensitivity of the modal grade with that of the mean grade when partitioning 6 weeks old seedlings into different resistance classes. The criteria were: the sensitivity of the two statistics as estimators of central tendency, the sensitivity of the modal grade and the mean grade as selection criteria and the correlation between the two statistics.The modal grade was neither more sensitive in detecting genotypes that fell in diffent resistance classes nor more severe than the mean grade in screening for genotypes susceptible to CBD. In the cases studied, the modal grad was highly correlated with the mean grade (rs ranged from 0.55**–0.82**). Hence, it is concluded that there are practically no gains in adopting the modal grade as a pre-selection criterion in preference to the mean grade. 相似文献
1000.
Endotoxin was detected by the LAL test in the plasma of swine and cattle following in vivo injection of endotoxin in order to evaluate the applicability of the test in veterinary medicine for detection of endotoxemia.Clinical symptoms of endotoxemia occurred after the injection into 3 swine of 0.10–0.25 mg endotoxin/100 kg bwt and after the infusion during 1–1½ h of 2.0–2.2 mg endotoxin/100 kg bwt into 3 calves. The concentration of endotoxin detected by the LAL test in the experimental animals ranged from 0.15 ng to 6.0 ng endotoxin per ml crude plasma. As positive LAL reactions were obtained only in close connection to the administration of endotoxin, clearance of endotoxin to levels below the sensitivity of the test was fast. In spite of the fast clearance, light symptoms of endotoxemia could be seen as long as 24 h after the last sample showing a positive test result. The applied technique for LAL analysis on blood, therefore, was not adequate for detection of endotoxin at sufficiently low concentrations and some possibilities of improving the technique are discussed.Though leukocytosis were found not to influence the outcome of the LAL test on blood, leukocytic mediators released by endotoxin or endotoxin-derived injuries may still have caused the persistence of the symptoms of endotoxemia, and this question is disputed in relation to the benefit of improving the technique.Especielly in the veterinary clinic, great precautions are necessary to obviate false positive test samples resulting from, e.g., external contamination or transient stress caused by excitement, and it is concluded that the possible application of the LAL test for detection of endotoxemia in veterinary medicine is restricted to surveillance of hospitalized animals and to research purposes. 相似文献