全文获取类型
收费全文 | 14866篇 |
免费 | 1047篇 |
国内免费 | 1062篇 |
专业分类
林业 | 859篇 |
农学 | 1171篇 |
基础科学 | 420篇 |
1487篇 | |
综合类 | 4934篇 |
农作物 | 1889篇 |
水产渔业 | 1086篇 |
畜牧兽医 | 3517篇 |
园艺 | 1213篇 |
植物保护 | 399篇 |
出版年
2024年 | 73篇 |
2023年 | 317篇 |
2022年 | 553篇 |
2021年 | 653篇 |
2020年 | 651篇 |
2019年 | 828篇 |
2018年 | 665篇 |
2017年 | 700篇 |
2016年 | 909篇 |
2015年 | 1118篇 |
2014年 | 1207篇 |
2013年 | 1199篇 |
2012年 | 1297篇 |
2011年 | 975篇 |
2010年 | 753篇 |
2009年 | 710篇 |
2008年 | 571篇 |
2007年 | 619篇 |
2006年 | 677篇 |
2005年 | 497篇 |
2004年 | 278篇 |
2003年 | 208篇 |
2002年 | 156篇 |
2001年 | 176篇 |
2000年 | 217篇 |
1999年 | 132篇 |
1998年 | 101篇 |
1997年 | 85篇 |
1996年 | 81篇 |
1995年 | 88篇 |
1994年 | 67篇 |
1993年 | 55篇 |
1992年 | 48篇 |
1991年 | 40篇 |
1990年 | 48篇 |
1989年 | 40篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 35篇 |
1984年 | 23篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
通过大田试验研究了400克/升氯氟醚菌唑悬浮剂防治香蕉叶斑病效果及其对香蕉产量的影响。研究结果表明,分别以20毫升、13.3毫升、10毫升400克/升氯氟醚菌唑悬浮剂兑水60公斤分3次喷雾施药,第二次施药后14d后对香蕉叶斑病防治效果在60.43-66.52%,第三次施药后14d后对香蕉叶斑病防治效果在75.72-80.72%,并对香蕉的单株产量有明显增产效果。其中尤以20毫升400克/升氯氟醚菌唑悬浮剂兑水60公斤剂量喷雾处理的效果最好。 相似文献
72.
Short-term climate reconstruction, i.e., the reproduction of short-term(several decades) historical climatic time series based on the relationship between observed data and available longer-term reference data in a certain area, can extend the length of climatic time series and offset the shortage of observations. This can be used to assess regional climate change over a much longer time scale. Based on monthly grid climate data from a Coupled Model Inter-comparison Project phase 5(CMIP5) dataset for the period of 1850–2000, the Climatic Research Unit(CRU) dataset for the period of 1901–2000 and the observed data from 53 meteorological stations located in the Tianshan Mountains region(TMR) of China during the period of 1961–2011, we calibrated and validated monthly average temperature(MAT) and monthly accumulated precipitation(MAP) in the TMR using the delta, physical scaling(SP) and artificial neural network(ANN) methods. Performance and uncertainty during the calibration(1971–1999) and verification(1961–1970) periods were assessed and compared using traditional performance indices and a revised set pair analysis(RSPA) method. The calibration and verification processes were subjected to various sources of uncertainty due to the influence of different reconstructed variables, different data sources, and/or different methods used. According to traditional performance indices, both the CRU and CMIP5 datasets resulted in satisfactory calibrated and verified MAT time series at 53 meteorological stations and MAP time series at 20 meteorological stations using the delta and SP methods for the period of 1961–1999. However, the results differed from those obtained by the RSPA method. This showed that the CRU dataset produced a low degree of uncertainty(positive connection degree) during the calibration and verification of MAT using the delta and SP methods compared to the CMIP5 dataset. Overall, the calibrated and verified MAP had a high degree of uncertainty(negative connection degree) regardless of the dataset or reconstruction method used. Therefore, the reconstructed time series of MAT for the period of 1850(or 1901)–1960 based on the CRU and CMIP5 datasets using the delta and SP methods could be used for further study. The results of this study will be useful for short-term(several decades) regional climate reconstruction and longer-term(100 a or more) assessments of regional climate change. 相似文献
73.
Dong Gyu Choi Ming He Hua Fang Xin Lan Wang Xiao Qin Li Xiang Jun Leng 《Aquaculture Nutrition》2020,26(1):37-46
The present study investigated the effect of fish meal (FM) replacement with fermented soybean meal (FSM) on growth and feed utilization of rainbow trout. Two FSM products, FSM1 (more fermentation with more small peptide and acid than FSM2) and FSM2 were used to replace 20%, 40% and 60% of FM in control diet (250 g/kg FM), respectively (FSM1‐20, FSM1‐40, FSM1‐60, FSM2‐20, FSM2‐40 and FSM2‐60). Then the seven diets were fed to rainbow trout (18.1 g) for 8 weeks. Weight gain (WG), feed conversion ratio (FCR) and digestibility of crude protein and dry matter showed no significant difference among the groups of FSM1‐20, FSM1‐40, FSM2‐20, FSM2‐40 and the control, but WG significantly decreased and FCR increased when 60% FM was replaced by both FSMs (p < .05). The replacement of 40%, 60% FM resulted in lower villus height than the control (p < .05), and intestinal protease activity was lower in FSM2‐40, FSM2‐60 and FSM1‐60 groups than the control group (p < .05). In addition, the activity of alkaline phosphatase and superoxide dismutase increased with increasing levels of FSM (p < .05). In conclusion, dietary fish meal could be replaced by 40% with both FSMs without adverse effects on growth and feed utilization of rainbow trout based on an eight weeks feeding trial. 相似文献
74.
Amrutha Gopan Narottam P. Sahu Tincy Varghese Parimal Sardar Manas K. Maiti 《Aquaculture Nutrition》2020,26(3):737-751
A protein isolate was prepared from karanj seed (KPI) with 921.2 g protein/kg seed, which contained a negligible amount of anti‐nutritional factors and a balanced amino acid composition, especially rich in methionine. For 60‐day feeding trial, five isonitrogenous (300 g/kg CP) and isocaloric (15 MJ DE/kg) diets were formulated by replacing soybean protein isolate (SPI) on protein equivalent basis, KPI‐0 (control, 0 g/kg KPI); KPI‐25 (replacing 250 g/kg SPI protein with KPI); KPI‐50 (replacing 500 g/kg SPI protein with KPI); KPI‐75 (replacing 750 g/kg SPI protein with KPI) and KPI‐100 (replacing 1,000 g/kg SPI protein with KPI) for the feeding of L. rohita. The weight gain percentage, specific growth rate, feed conversion ratio and protein efficiency ratio were not significantly (p > .05) varied among the KPI fed and control groups. A significantly higher hepatosomatic index was recorded in the control and KPI‐25 groups compared with other groups. The whole‐body compositions, except ether extract, did not differ significantly (p > .05) among the groups. Digestive (amylase, protease, lipase and alkaline phosphatase) and metabolic enzyme activities (hexokinase, transaminases and lactate dehydrogenase) and glycogen stores were not significantly affected, whereas intestinal alkaline phosphatase differed significantly (p < .05). The RNA–DNA ratio was significantly (p < .05) higher in the KPI‐75 group. Thus, the study revealed that KPI can completely replace SPI protein at 191 g/kg inclusion level in the diets of L. rohita fingerlings. 相似文献
75.
Ming He Xiaoqin Li Lumpan Poolsawat Zihao Guo Wenxiang Yao Chunyan Zhang Xiangjun Leng 《Aquaculture Nutrition》2020,26(4):1058-1071
This study was conducted to investigate the effects of replacing fish meal (FM) with fermented soybean meal (FSM) and soybean meal (SM) on growth performance, intestinal histology and microbiota of largemouth bass (Micropterus salmoides). The basal diet contained 350 g/kg FM (CON), and then, FM was replaced with SM and FSM at the ratios of 30% and 60% (SM‐30, SM‐60, FSM‐30 and FSM‐60), respectively. The largemouth bass (4.43 ± 0.13 g) were fed for 8 weeks. The results showed that weight gain of fish fed with FSM‐60 and SM‐60 diets was significantly lower, and feed conversion ratio of SM‐30, SM‐60 and FSM‐60 groups was significantly higher than the CON group (p < .05). The intestinal villus height of SM‐60 group and the villus width of SM‐60 and FSM‐60 group were significantly lower than the CON group (p < .05). The 30% FM replacement by SM and FSM significantly increased the abundance of Cetobacterium and Mycoplasma, respectively (p < .05). In conclusion, FSM could replace 30% FM in diet without negative impacts on the growth performance of largemouth bass, while the SM should be controlled below 30%. 相似文献
76.
77.
西府海棠锈病是危害西府海棠的最重要病害,造成叶片枯黄、早落,影响次年的开花与结果。本研究,分析了近年来病害严重发生的环境影响因素,并提出防治技术方案。 相似文献
78.
79.
80.
我国鱼粉产品质量参差不齐,由于原料问题组胺含量普遍高于国际先进水平,过高的鱼粉含量易造成食品安全问题。为了降低过高的组胺含量对鱼粉品质的影响,本实验通过使用微生物参与降解鱼粉产品中的组胺。实验将降解时间与微生物添加比例作为变量,测试出较为适宜微生物降级组胺的条件,以及该条件下的实际效果。实验结果表明在设置的6个时间中(以6小时为时间梯),24h为较适宜的降解时间;在较适宜的降解时间中(24h)较适宜的微生物添加比例为10:1。此时鱼粉组胺含量为1622mg/kg,相较未加入微生物处理的鱼粉组胺含量(5298 mg/kg)降低69%。实验结果证明了微生物处理鱼粉中组胺具有显著的效果,为鱼粉生产、储存技术的改良提供了参考依据。 相似文献