全文获取类型
收费全文 | 2293篇 |
免费 | 154篇 |
国内免费 | 177篇 |
专业分类
林业 | 104篇 |
农学 | 88篇 |
基础科学 | 80篇 |
187篇 | |
综合类 | 1187篇 |
农作物 | 178篇 |
水产渔业 | 90篇 |
畜牧兽医 | 426篇 |
园艺 | 175篇 |
植物保护 | 109篇 |
出版年
2024年 | 5篇 |
2023年 | 16篇 |
2022年 | 110篇 |
2021年 | 98篇 |
2020年 | 76篇 |
2019年 | 102篇 |
2018年 | 90篇 |
2017年 | 123篇 |
2016年 | 96篇 |
2015年 | 162篇 |
2014年 | 159篇 |
2013年 | 155篇 |
2012年 | 252篇 |
2011年 | 264篇 |
2010年 | 184篇 |
2009年 | 177篇 |
2008年 | 153篇 |
2007年 | 118篇 |
2006年 | 86篇 |
2005年 | 66篇 |
2004年 | 30篇 |
2003年 | 11篇 |
2002年 | 19篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 9篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1958年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有2624条查询结果,搜索用时 281 毫秒
91.
通过对伦敦奥运会男篮比赛分析发现,来源于欧美职业篮球联赛队员数量决定各队竞技实力,体现各国运动员国际流动与交融发展新趋势;欧、美球队呈现“高、快、灵、准、全、悍、变、星”的进攻特征及防守“以球权争夺为核心,球、人、区、时空兼顾”的先进理念;当前世界篮球区域发展不均衡,美洲占据竞技优势,欧洲整体水平高,亚、非洲实力弱,呈欧美全面抗衡格局;中国男篮竞技水平和成绩下滑明显,运动员身体机能指标和得分、失分、投篮次数、命中率、篮板球、助攻、失误、抢断指标与世界强队存在显著性差异(P﹤0.05),盖帽、犯规无显著性差异(P>0.05),表现出个人能力、技战术风格、整体攻防与世界强队全方位差距,并呈逐步拉大趋势。 相似文献
92.
以阜新地区为例,开展不同秸秆还田量对旱地土壤水肥和玉米生长与产量的影响研究。试验设计0 kg·hm-2,6 000 kg·hm-2,12 000 kg·hm-2,18 000 kg·hm-2、24 000 kg·hm-2共5个处理,3次重复,共15个小区,小区面积(4 m×15 m)为60 m2。研究结果表明,对照CK不施用秸秆处理,深耕加秸秆的方法,土壤含水量显著增加,除了对照之外,各个处理剂量之间的差异并不明显,且呈先上升而后下降趋势。说明秸秆在土壤中始终处于水分的非饱和状态,并不是秸秆剂量越大越好。各个层次土壤容重与对照相比变化较明显,其中10~20 cm深处土壤容重变化最大,各个处理土壤容重表现出随秸秆还田量增加土壤容重降低值减少的趋势,下降幅度为12 000 kg·hm-2>6 000 kg·hm-2>18 000 kg·hm-2。秸秆还田处理,提高了植物的叶绿素含量,促进了植物的光合效率,以12 000 kg·h
m-2处理较好。不同处理对玉米产量影响差异显著,达到了5%的显著水平,施入量在0~12 000 kg·hm-2之间,玉米产量呈上升趋势,超过18 000 kg·hm-2产量呈下降趋势,因此建议推广剂量为12 000 kg·hm-2。 相似文献
93.
[目的]研究氮磷钾配施对北苍术的产量、苍术素含量及乙酰辅酶A羧化酶(ACC)活性和基因表达量的影响,探讨氮磷钾配施对北苍术药材产量增加、质量形成的影响及其机制,对提高北苍术药材产量及质量有重要的现实意义.[方法]以一年生北苍术为试验材料,采用L9(34)?正交设计,设置10个不同氮、磷、钾用量处理的田间试验,在营养生长... 相似文献
94.
95.
通过研究分析表明:兰州市园林绿化用土紧缺,绿地土壤存在密实度高、有机质含量低、污染严重、土源短缺、养护管理缺乏科学性等问题,必须提高土壤改良的科学性和管理的有效性,确保兰州市园林绿化事业的可持续发展。 相似文献
96.
The objective of this study was to evaluate of the growth performance, serum biochemical indices, liver antioxidant parameters and ability of anti-infection with Aeromonas hydrophila by adding the fermented Chinese medicine by Bacillus Subtilis to the carp fish feed, and to find out the appropriate supplemental level of fermented Chinese medicine in diets. Carp fingerling with an initial body weight of (35±0.5) g were set up to 6 experimental diets supplemented with 0 (control group), 0.1‰, 0.5‰, 1‰, 2‰ and 3‰ fermented Chinese medicine for 56 days, respectively. Each group had 30 fish and set up 3 repetitions. After the feeding trail,the fish were challenged with Aeromonas hydrophila to calculate the relative percentage survival (RPS).The results showed as follows:Supplementing fermented traditional Chinese medicine by Bacillus subtilis, the weight gain rate (WGR), specific growth rate (SGR), condition factor (CF), the activities of lysozyme (LSZ), complement 3 (C3),total protein (TP),total anti-oxidation capacity (T-AOC),total superoxide dismutase (T-SOD) and catalase (CAT) in serum of common carp were enhanced at different degrees, while the feed coefficient (FCR)and malondialdehyde (MDA) in serum were declined at different degrees.When the fermented Chinese medicine supplemental levels were 2‰ and 3‰,the effects were significant (P<0.05)(except for C3, ALP and Cr).The experimental results of the virulence of common carp infected with pathogen Aeromonas hydrophila showed that,the fermented herbal could obviously improve the ability of anti-infection, the immune protective rate of the group with 2‰, 3‰ doses of the fermented Chinese medicine could reach 77.23% and 74.63%, respectively. From what had been discussed above, the group with 2‰ and 3‰ doses of the fermented Chinese medicine had significant effect on the growth performance, serum biochemical indices, liver antioxidant parameters and Aeromonas hydrophila anti-infection ability. Considering the cost of adding fermented Chinese medicine, the recommendations for the best additive quantity was 2‰. 相似文献
97.
98.
陈婷婷 《上海交通大学学报(农业科学版)》2013,(3):98-100
探讨较长时间的有氧健身操锻炼对普通女性大学生STI是否有良性的影响,30名普通女性大学生分成实验组(15人,3次/周, 90min/次)和对照组(15人,1次/周, 90min/次),共16周(一个学期)有氧健身操定量锻炼。分别在锻炼前、第8周末、16周结束时测量STI指标。结果表明,8周有氧健身操锻炼有一定的效果,但并不显著,直到16周结束STI相应指标才出现较明显的变化。提示:短期的有氧健身操锻炼对心脏的影响较小,要使心脏发生与运动相适应性的良性变化,锻炼的周期要长,且要保证每周锻炼的次数和时间。 相似文献
99.
AIM: To establish a method for determining the differential expression of proteins in human endometrium during the implantation window and to analyze the correlation between altered expression of the proteins and endometrial receptivity. METHODS: A comparative proteomic strategy in a combination of two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was adopted to search the proteomic alternations in the endometria of pre-receptive pre-receptive [day 2 after luteinizing hormone surge (LH+2 d)] state versus the endometria of receptive (LH+7 d) state. Validation of annexin IV was performed by Western blotting. RESULTS: Approximate 2 555±98 polypeptide spots were revealed by densitometry analysis of the 2D protein maps in LH+2 d and LH+7 d endometrial tissues resolved in the linear range of pH 3~10 on the 2D gel, in which 31 proteins were found to be significantly changed, including 17 proteins up-regulated and 14 proteins down-regulated in LH+7 d samples. These 31 identified proteins were classified into 6 functional categories of the correlation with implantation process: cell migration or assimilation, enzymic activity, signal transduction and gene regulation, immunoregulation, vascularization, and blood clotting or fibrinolysis system. The same expression trend of annexin IV was confirmed by Western blotting. CONCLUSION: Human endometrium has a differential proteomic repertoire during the window of implantation. The 6 functional categories of differentially expressed proteins in the receptive endometrium indicate that they play an important role in transforming of the endometrium during the receptive state. 相似文献
100.
Juvenile tilapias (Oreochromis niloticus × O. aureus), with average body weights of groups I, II and III of 55.14, 122.82, and 225.68 g respectively were used to study changes in the activity of protease, amylase, and lipase in different organs and sections of the alimentary tract. Additionally, tract containing digesta, which is closer to physiological conditions, may help reveal the mechanisms of whole chemical digestion process. Another group of tilapias (mean body weight of 111.81 ± 0.14 g) was used to analyze changes in activity of protease, lipase, and amylase in response to varying pH and temperatures. The activity of enzymes in all digestive organs increased when body weight increased from 55 to 122 g, and the activity further increased when the weights increased from 122 to 225 g. The rates of increase in digestive enzyme activity were significantly greater than the rates of growth of the fish. When the activity was compared in different sections of the tract, a similar regularity was found for the three enzymes in all fish. The highest amounts of activity were seen in the foregut and the lowest in the rectum, with the middle amount of activity in the hindgut. The pH ranges for the maximum activity of tilapia protease in the stomach and intestine were 1.6–3.3 and 9.5–10.5 respectively and the optimal temperature in these organs was 55°C. The pH ranges for the maximum amylase activity in the intestine and hepatopancreas were 6–7 and 7.5 respectively, and high amylase activity in these organs was found at 25–35°C. The activity of lipase in the intestine remained unchanged at pH 6.0–9.0 and with temperatures between 25 and 35°C. These results suggest that the ability of tilapia to utilize feed varies at different growth stages and remains relatively stable with changes in environmental pH and temperature, which should be taken into account when designing feed formulas for tilapia. 相似文献