全文获取类型
收费全文 | 5997篇 |
免费 | 348篇 |
国内免费 | 733篇 |
专业分类
林业 | 673篇 |
农学 | 922篇 |
基础科学 | 480篇 |
1107篇 | |
综合类 | 1835篇 |
农作物 | 389篇 |
水产渔业 | 304篇 |
畜牧兽医 | 725篇 |
园艺 | 263篇 |
植物保护 | 380篇 |
出版年
2024年 | 24篇 |
2023年 | 72篇 |
2022年 | 189篇 |
2021年 | 243篇 |
2020年 | 234篇 |
2019年 | 249篇 |
2018年 | 183篇 |
2017年 | 244篇 |
2016年 | 187篇 |
2015年 | 307篇 |
2014年 | 234篇 |
2013年 | 293篇 |
2012年 | 355篇 |
2011年 | 416篇 |
2010年 | 377篇 |
2009年 | 326篇 |
2008年 | 290篇 |
2007年 | 341篇 |
2006年 | 305篇 |
2005年 | 295篇 |
2004年 | 145篇 |
2003年 | 125篇 |
2002年 | 87篇 |
2001年 | 111篇 |
2000年 | 132篇 |
1999年 | 165篇 |
1998年 | 169篇 |
1997年 | 140篇 |
1996年 | 104篇 |
1995年 | 125篇 |
1994年 | 112篇 |
1993年 | 107篇 |
1992年 | 84篇 |
1991年 | 63篇 |
1990年 | 51篇 |
1989年 | 52篇 |
1988年 | 42篇 |
1987年 | 27篇 |
1986年 | 15篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1964年 | 5篇 |
排序方式: 共有7078条查询结果,搜索用时 31 毫秒
951.
Shuilin Cai Nan Pan Min Xu Yongchang Su Kun Qiao Bei Chen Bingde Zheng Meitian Xiao Zhiyu Liu 《Marine drugs》2021,19(12)
Angiotensin-I-converting enzyme (ACE) is a crucial enzyme or receptor that catalyzes the generation of potent vasopressor angiotensin II (Ang II). ACE inhibitory peptides from fish showed effective ACE inhibitory activity. In this study, we reported an ACE inhibitory peptide from Takifugu bimaculatus (T. bimaculatus), which was obtained by molecular docking with acid-soluble collagen (ASC) hydrolysate of T. bimaculatus. The antihypertensive effects and potential mechanism were conducted using Ang-II-induced human umbilical vein endothelial cells (HUVECs) as a model. The results showed that FNLRMQ alleviated the viability and facilitated apoptosis of Ang-II-induced HUVECs. Further research suggested that FNLRMQ may protect Ang-II-induced endothelial injury by regulating Nrf2/HO-1 and PI3K/Akt/eNOS signaling pathways. This study, herein, reveals that collagen peptide FNLRMQ could be used as a potential candidate compound for antihypertensive treatment, and could provide scientific evidence for the high-value utilization of marine resources including T. bimaculatus. 相似文献
952.
953.
Tailiang Liu Hua Wen Ming Jiang Danning Yuan Pan Gao Yujiang Zhao Fan Wu Wei Liu 《Fish physiology and biochemistry》2010,36(3):565-572
An experiment was conducted to investigate the effect of dietary chromium picolinate supplement on growth and haematology
parameters of grass carp, Ctenopharyngodon idellus. Six diets with increasing dietary chromium picolinate levels 0, 0.2, 0.4, 0.8, 1.6 and 3.2 mg kg−1 were fed to triplicate groups of 20 fish (initial weight of 12.78 ± 1.16 g, mean ± SD) in a flow water system for 10 weeks.
Fish fed the diet supplemented with 0.8 mg Cr kg−1 had significantly improved weight gain (WG), feed efficiency ratio (FER), protein efficiency ratio (PER) and protein retention
(PR). Fish fed high-chromium diets exhibited lower whole-body crude lipid contents than fish fed low-chromium diets. Liver
glycogen concentrations for fish fed the diet with 0.2 mg Cr kg−1 was the highest (77.67 mg g−1). Fish fed the diet supplemented with 1.6 and 3.2 mg Cr kg−1 had significantly lower liver glycogen concentrations than other groups (P < 0.05). The highest serum insulin concentrations were observed in fish fed the diet supplemented with 0.8 mg Cr kg−1, but serum insulin concentrations decreased (P < 0.05) when dietary supplementation of chromium was higher than 0.8 mg Cr kg−1. Cholesterol concentrations decreased in direct proportion to dietary chromium level and achieved the lowest level when the
fish were fed the 0.8 mg Cr kg−1 diet, but increased when the fish were fed the diet with more than 0.8 mg Cr kg−1 (P < 0.05). Fish fed the diet supplemented with 0.8 mg Cr kg−1 had higher triglyceride and high-density lipoprotein cholesterol (HDL-C) concentrations compared to other treatments. The
results of the present study suggested that chromium picolinate could modify serum carbohydrate and lipid metabolism profile,
and that the optimal dietary chromium level was 0.8 mg kg−1 for grass carp according to growth. 相似文献
954.
复合硝化菌制剂对水质改良的应用效果 总被引:8,自引:0,他引:8
室内静态水体中0.25mg/L复合硝化菌制剂使用后,7d内氨氮平均降解率为34.84%,亚硝酸盐氮的平均降解率为19.05%。0.5mg/L组氨氮平均降解率为45.05%,亚硝酸盐的平均降解率为41.79%。1.0mg/L组的氨氮平均降解率为55.26%,亚硝酸盐氮平均降解率为51.20%。氨氮和亚硝酸盐氮的最大的降解峰值出现6d之间。而养殖池塘中,0.5mg/L复合硝化菌制剂后,5d内氨氮的降解率为13.61%~28.03%,7d内亚硝酸盐氮的降解率为9.30%~25.58%。0.2mg/L复合硝化菌制剂使用后,6d内氨氮的降解为23.40%~34.75%,7d内亚硝酸盐氮的降解率为16.33%~36.13%。试验结果表明,复合硝化菌制剂在养殖池塘中使用后,有降解速度快、降解能力强、维持时间长等特点,适宜于作为净化和调控养殖水质的渔用微生物制剂使用。 相似文献
955.
956.
以浓硫酸为磺化剂,合成了磺酸基聚松香苯甲酯(SRBEP),测定了SRBEP中磺酸基(-SO3H)的含量,用红外光谱测定了合成树脂的结构,分别用静态吸附法和动态吸附法考察了SRBEP对金属离子Co2 、Cu2 、 Pb2 的吸附性能及其重复使用性.结果显示,在20 ℃时SRBEP的接枝率较高.该树脂能与Co2 、Cu2 、 Pb2 等金属离子络合,对Co2 、Pb2 的吸附比较明显,该树脂在重复使用6次后,相对保留率达80%以上,能用于金属离子的吸附分离. 相似文献
957.
Yang Mingxia Zhang Jun Liang Qiting Pan Guanxin Zhao Jiachang Cui Miao Zhao Xinqing Zhang Qizhong Xu Delin 《Fisheries Science》2019,85(3):533-543
Fisheries Science - Marine Streptomyces sp. isolate S073 was shown to have strong antagonistic activity towards the pathogenic Vibrio parahaemolyticus using the agar diffusion method. The... 相似文献
958.
959.
Mingchun Ren Juyun He Hualiang Liang Ke Ji Xianping Ge Ajun Sun Liangkun Pan Karthik Masagounder 《Aquaculture Nutrition》2019,25(3):567-576
A feeding trial was conducted to investigate the effects of essential amino acids (EAA) supplementation on the success of dietary protein reduction for Jian carp (Cyprinus carpio var. Jian). Five diets were formulated including a positive control (Diet 1, 378.4 g/kg protein), a negative control (Diet 5, 289.8 g/kg protein) and three test diets (Diet 2‐Diet 4, 340.4–299.0 g/kg protein supplemented with EAA). No significant decline of growth performance in fish fed decreased dietary protein with EAA supplementation, which were significantly higher than the negative control. The apparent digestibility coefficients (ADC) of protein and most EAAs were not significantly affected by the dietary treatments. Dietary treatments did not affect whole‐body composition, but influenced protein and EAAs retentions. Total ammonia nitrogen (TAN) excretion decreased with the decreasing dietary protein, and the highest plasma ammonia content was observed in fish fed Diet 5. Plasma glucose concentration increased with the decreasing dietary protein reduction, while other plasma parameters were not affected by dietary treatments. These results indicated that low‐protein diets (299.0 g/kg) supplemented with EAA can maintain protein, EAA digestibility and retention in Jian carp, and also has benefit in the reduction of TAN excretion. 相似文献
960.
Ahmed Mokrani Hualiang Liang Ke Ji Hopeson Chisomo Kasiya Qiang Yang Xianping Ge Mingchun Ren Xuezhi Zhu Liangkun Pan Ajun Sun 《Aquaculture Research》2019,50(2):557-565
Six diets were formulated to investigate the success of fish meal (FM) replacement by plant proteins; diet 1 reflected a commercial feed (8% FM), diet 3 contained 4% FM, and diet 5 was devoid of FM. Whereas, diet 2, diet 4, and diet 6 reflected diet 1, diet 3, diet 5, respectively, and supplemented with essential amino acid (EAA). At the end of 8‐week trial, there was no significant difference in survival rate. Significantly higher final weight, weight gain rate, and specific growth rate were recorded in the group fed diet 2 compared with the other treatments (except diet 4) (p < 0.05). Feed conversion ratio of fish fed diet 2 was significantly lower than those fed diets 1, 3, and 5 (p < 0.05). The lowest feed intake and highest protein efficiency rate were found in fish fed diet 2 (p < 0.05). There was no significant difference in whole body compositions between treatments. Plasma aspartate transaminases, alanine aminotransferase, and glucose were significantly affected by dietary treatments (p < 0.05), while plasma protein and albumin contents were not influenced by the treatments. The relative expression of target of rapamycin (TOR) and phosphatidylinositol 3‐kinase, regulatory subunit 1 (alpha) (PIK3R1) in fish fed diet 3 (4% FM) were significantly down‐regulated compared with those fed diet 6 for TOR and diets 4 and 6 for PIK3R1 (p < 0.05). Insulin receptor substrate 1 (IRS‐1) and janus kinase 3 (JAK3) expressions were fluctuated, with the higher levels in fish fed diets 4 and 6. In conclusion, the findings of this study indicate that plant protein mixture supplemented with EAA could be used to substitute FM in practical diet for Megalobrama amblycephala. 相似文献