首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   71095篇
  免费   3209篇
  国内免费   8014篇
林业   9022篇
农学   11880篇
基础科学   6784篇
  12261篇
综合类   19974篇
农作物   3598篇
水产渔业   2568篇
畜牧兽医   9526篇
园艺   2160篇
植物保护   4545篇
  2024年   153篇
  2023年   681篇
  2022年   1795篇
  2021年   2664篇
  2020年   2500篇
  2019年   2432篇
  2018年   1668篇
  2017年   2357篇
  2016年   2411篇
  2015年   3118篇
  2014年   2944篇
  2013年   3689篇
  2012年   4280篇
  2011年   4775篇
  2010年   4520篇
  2009年   4285篇
  2008年   4162篇
  2007年   4181篇
  2006年   4048篇
  2005年   3578篇
  2004年   1726篇
  2003年   1535篇
  2002年   1155篇
  2001年   1324篇
  2000年   1573篇
  1999年   1869篇
  1998年   1891篇
  1997年   1579篇
  1996年   1431篇
  1995年   1356篇
  1994年   1181篇
  1993年   1126篇
  1992年   948篇
  1991年   792篇
  1990年   675篇
  1989年   581篇
  1988年   447篇
  1987年   267篇
  1986年   169篇
  1985年   82篇
  1984年   73篇
  1983年   65篇
  1982年   51篇
  1981年   39篇
  1980年   29篇
  1979年   20篇
  1978年   9篇
  1965年   12篇
  1964年   14篇
  1963年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
为了解湖南省娄底市活禽批发市场活禽来源与流通情况,对2020—2021年娄底市2个活禽批发市场活禽调入、调出情况进行了调查.结果显示:每年调入娄底市活禽批发市场的活禽超过3000批次,数量超过600万羽;调入活禽种类有鸡、鸭、鹅、鸽等品种,其中活鸡比例超过80%;活禽批发市场主要以省内调入为主,还涉及12个省(自治区)...  相似文献   
992.
2016年8月16日,新疆温泉县某乡镇报告发生羊不明原因死亡,疑似感染捻转血矛线虫.为确定病因,控制疫情,减少损失,防止类似事件再次发生,新疆维吾尔自治区动物疾病预防控制中心组织相关人员,采用现场访谈、实地调查、问卷调查、临床剖检等方式,开展了紧急流行病学调查.调查发现:温泉县牧区是捻转血矛线虫的老疫区,在数十年前曾暴...  相似文献   
993.
兽药残留检测是监督控制药物滥用的手段之一。免疫学技术基于抗原对抗体的特异性识别,具有灵敏度高、稳定性好、操作简单、快捷等优点被广泛应用于兽药残留检测。该方法的关键是要获得高质量的特异性抗体,因而单抗技术的应用与发展,对免疫分析方法的普及起了巨大推动作用。为此,本文针对单抗的制备以及基于单抗的免疫分析方法在兽药残留检测领域的应用进行简要综述。目前酶联免疫吸附法(ELISA)与胶体金免疫层析法(GICA)是应用最广泛的基于单抗的兽药残留检测方法,主要用于检测抗生素、化学合成抗菌药、激素类和β-受体激动剂类药物、镇静剂类药物,其操作简单,灵敏度高,但均需要对样品进行一定的前处理,实际操作中较易出现假阳性,反应时间长等问题。为提高检验的敏感度、稳定性、特异性、便捷性,正在研究新型的免疫分析技术,如结合采用表面增强拉曼光谱(SERS)技术和金标检测试纸(LFA)实现超灵敏检测,采用微流控免疫分析芯片技术联合ELISA实现高通量检测等。诸多研究将为基于单抗的免疫分析方法在兽药残留检测中的应用提供新思路。  相似文献   
994.
宫内发育迟缓(IUGR)降低仔猪存活率和生长性能,给养猪业带来严重经济损失.如何有效降低IUGR仔猪的出生,一直是行业关注的科学问题.胎盘是一个高度血管化的器官,其血管生成异常会阻碍氧气和营养物质的正常运输,导致胎盘无法正常向胎儿提供足够的营养物质,这可能是引起仔猪IUGR的重要因素.鉴于胎盘血管在胎猪生长过程中扮演的...  相似文献   
995.
为验证碾压消毒垫和驶过消毒池两种常见运输车辆消毒方式对非洲猪瘟病毒(ASFV)的杀灭效果,采用生物学特性和理化特性相近的猪伪狂犬病毒(PRV)疫苗稀释液喷洒运输车辆车轮,测试两种消毒方式的消毒效果。结果显示:车辆碾压消毒垫后0、1、2、3、4、5 min以及驶过消毒池后0、2、5、10 min,车轮可被检测的PRV与表面细菌含量均呈下降趋势,且杀灭效果随时间增加而增强。其中,碾压消毒垫后5 min无法有效杀灭所有PRV,细菌杀灭率为92.5%;驶过消毒池后10 min可有效杀灭所有PRV,细菌杀灭率为98.3%。本研究结果为提高非洲猪瘟疫情应急处置水平和日常防控消毒措施有效性提供了数据支撑。  相似文献   
996.
对临床接诊的1例犬体表肿物进行诊断,采用临床检查、血液常规检查、血液生化检查、组织细胞学检查、影像学检查等方法进行诊断,结果为犬肥大细胞瘤,术后患犬痊愈.该病例可为犬肥大细胞瘤的临床诊断和治疗提供参考.  相似文献   
997.
This experiment was conducted to study the effects of Bacillus amylolyticus on rumen dry matter digestibility, fermentation parameters and metabolites of dairy cows. Experiment 1: six dairy cows with permanent fistula and had the similar parity (2 to 3 fetuses), body weight [(662 ±57) kg], lactation days [(160 ± 22) d] and milk yield [(36.1 ±3.8) kg / d], were randomly divided into 3 groups with 2 cows per group. Using 3 ×3 Latin square design, each group was extra fed 0 (control group), 5 ×109 and 5 ×1010 CFU / d Bacillus amylolyticus, the trial period was 3 periods, 13 days for each period, including 10 days for the pre-trial period and 3 days for the trial period. At the beginning of the trial period, the rumen dry matter digestibility of cows was measured by nylon bag method. Experiment 2: thirty dairy cows with similar parity [(2.5 ±0.3) fetuses], initial body weight [(559.2 ± 7. 4) kg], milk yield [(35. 2 ± 1. 5) kg / d] and lactation days [(99 ± 22) d] were randomly divided into three groups with 10 cows in each group. Cows in the 3 groups were extra fed with 0 (control group), 5 ×109 and 5 ×1010 CFU / d Bacillus amylolyticus, respectively. The pre-trial period was 10 days and the trial period was 42 days. The rumen fluid was collected on the last day of the trial period, and the rumen fermentation parameters and metabolites were determined. The results showed as follows: compared with the control group, 1) supplementary feeding of 5 × 1010 CFU / d Bacillus amylolyticus could significantly improve the rumen dry matter digestibility of dairy cows at 12, 24, 36, 48 and 72 h (P <0.05), supplementary feeding of 5 ×109 CFU / d Bacillus amylolyticus could significantly improve the rumen dry matter digestibility of dairy cows at 36 and 48 h (P <0.05); 2) supplementary feeding of 5 ×109 CFU / d Bacillus amylolyticus could significantly increase the contents of isobutyric acid, butyric acid, isovaleric acid, valeric acid, total volatile fatty acid and microbial protein in the rumen of dairy cows (P < 0. 05), supplementary feeding of 5 × 1010 CFU / d Bacillus amylolyticus could significantly increase the contents of isobutyric acid and isovaleric acid in the rumen of dairy cows and significantly reduce the rumen acetic acid / propionic acid (P < 0. 05), supplementary feeding of 5 ×109 and 5 ×1010 Bacillus amylolyticus had no effects on rumen pH and ammonia nitrogen content (P >0.05); 3) eleven metabolic pathways related to differential metabolites were detected, and ascorbic acid and alginate metabolism were significantly enriched (P < 0. 05) . In conclusion, Bacillus amylolyticus can increase the rumen dry matter digestibility, and improve the rumen fermentation function of dairy cows by affecting the content of rumen metabolites. By comprehensive analysis, supplementary feeding of 5 × 109 CFU / d Bacillus amylolyticus can achieve better effect. © 2023 Authors. All rights reserved.  相似文献   
998.
This experiment was conducted to study the effects of dietary lactic acid bacteria (LAB) and fructooligosaccharides (FOS) on growth performance, nutrient digestibility and serum biochemical indices of Arctic foxes (Alopex lagopus) during early growth period. Sixty male post-litter Arctic foxes with the average body weight of (1.16±0.15) kg and at the age of (45±3) days were randomly assigned to 4 groups with 3 replicates per group and 5 foxes per replicate. The foxes were fed the following diets, respectively: basal diet (control group), basal diet+3×109 CFU / kg LAB (LAB group), basal diet+5 g / kg FOS (FOS group) and basal diet+3×109 CFU / kg LAB+5 g / kg FOS (LAB+FOS group). The experiment lasted for 30 days. The results showed as follows: 1) on the days 1 to 15, the diarrhea rate of foxes in the LAB group and LAB+FOS group was significantly lower than that in the control group and FOS group (P<0.05). On the days 16 to 30, the average daily gain of foxes in the LAB+FOS group was significantly higher than that in the control group and FOS group (P<0.05), but had no significant difference with LAB group (P>0.05); the diarrhea rate of foxes in the LAB+FOS group was significantly lower than that in the control group and FOS group (P<0.05), but had no significant difference with LAB group (P>0.05); compared with the FOS group, the feed to gain ratio of foxes in the LAB+FOS group was significantly decreased (P<0.05). 2) The dry matter digestibility of foxes in the LAB + FOS group was significantly higher than that in the control group and FOS group (P < 0.05), but had no significant difference with LAB group (P>0.05). There were no significant differences in nitrogen intake, fecal nitrogen, urine nitrogen, nitrogen deposition, net protein utilization and protein biological value among all groups (P>0.05). 3) Serum total protein (TP) content of foxes in the LAB+FOS group was significantly higher than that in the FOS group (P<0.05), but had no significant difference with control group and LAB group (P>0.05). Serum albumin (ALB) content of foxes in the LAB group was significantly higher than that in the control group and FOS group (P<0.05), but had no significant difference with LAB+ FOS group (P>0.05). Serum urea nitrogen (UN) content of foxes in the LAB+FOS group was significantly decreased compared with the control group (P < 0. 05). In conclusion, the combined supplementation of 3 × 109 CFU / kg LAB and 5 g / kg FOS in the diet is beneficial to reduce diarrhea rate, improve dry matter digestibility, improve body immune level, and promote the growth of Arctic foxes during early growth period. © 2023 Chinese Journal of Urology. All rights reserved.  相似文献   
999.
畜产品中药物残留主要包括β-受体激动剂类、抗生素类、性激素类等药物。ELISA检测技术因其灵敏度高、特异性强、仪器设备简单、成本低、方法快速、简便等优点,成为畜产品中药物残留目前最理想的检测技术之一。为了考察试剂盒的各项指标与标示指标是否一致和能否正确使用试剂盒,本文就ELISA检测技术在畜产品中兽药残留检测试剂盒的选择原则和使用注意事项进行了归纳总结。  相似文献   
1000.
为了解决使用简易装置、依靠人工方法而导致冷冻细管精液精子复苏率低及冷冻数量少的问题,利用日本西川式简易急速冻结器和密集浸入式细管精液冷冻仪,采取竖向紧密摆放、垂直浸入冷冻精液细管的方法开展试验.结果表明:密集浸入式细管精液冷冻方法,可使解冻后精子复苏率达到57% ~ 61%,并可以增加每次冷冻细管精液数量,与国内人工冷冻方法比较差异显著(P<0.05),国外程控冷冻方法比较差异不显著(P>0.05);应用计算机程序控制细管精液冷冻的方法,能够精确控制精液的降温速率,精子复苏率和工作效率显著提高.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号