全文获取类型
收费全文 | 16386篇 |
免费 | 3357篇 |
国内免费 | 924篇 |
专业分类
林业 | 456篇 |
农学 | 1072篇 |
基础科学 | 151篇 |
4443篇 | |
综合类 | 4197篇 |
农作物 | 650篇 |
水产渔业 | 2843篇 |
畜牧兽医 | 4448篇 |
园艺 | 131篇 |
植物保护 | 2276篇 |
出版年
2024年 | 101篇 |
2023年 | 275篇 |
2022年 | 432篇 |
2021年 | 559篇 |
2020年 | 907篇 |
2019年 | 1409篇 |
2018年 | 1176篇 |
2017年 | 1377篇 |
2016年 | 1225篇 |
2015年 | 1088篇 |
2014年 | 1082篇 |
2013年 | 1576篇 |
2012年 | 1920篇 |
2011年 | 1274篇 |
2010年 | 1077篇 |
2009年 | 790篇 |
2008年 | 705篇 |
2007年 | 640篇 |
2006年 | 505篇 |
2005年 | 490篇 |
2004年 | 331篇 |
2003年 | 287篇 |
2002年 | 272篇 |
2001年 | 228篇 |
2000年 | 218篇 |
1999年 | 125篇 |
1998年 | 84篇 |
1997年 | 94篇 |
1996年 | 63篇 |
1995年 | 50篇 |
1994年 | 46篇 |
1993年 | 42篇 |
1992年 | 41篇 |
1991年 | 35篇 |
1990年 | 29篇 |
1989年 | 35篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1962年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
猪肠道细菌培养组学研究进展 总被引:2,自引:0,他引:2
猪肠道菌群是由所有定殖在猪肠道里的大量细菌、病毒、真菌和古菌等构成的集合.已有研究表明,很多疾病以及猪重要经济性状都与肠道菌群有关.目前,肠道菌群研究使用较多的技术是16S rRNA基因测序和宏基因组测序,但这些技术并不能了解具体菌株的实际功能和生理特性.肠道细菌的分离培养具有特殊重要的意义.近几年来,肠道细菌的培养取... 相似文献
62.
63.
64.
65.
乳牛口服过量维生素A对维生素D3及钙磷代谢的影响 总被引:9,自引:0,他引:9
从北京郊区某农场选取10头健康成年黑白花乳牛,随机分为试验(5头,每周每头口服维生素A100万单位)和对照(5头,不作任何处理)两组。8周以后检测发现,试验组血清钙和无机磷水平呈下降趋势;尾椎骨皮质变薄,密度下降,呈现骨质吸收现象;血清碱性磷酸酶显著下降(P<0.05);其活性代谢产物25-羟维生素D3(25-OH-D3)极显著下降(P<0.01);1,25-二羟维生素D3[1,25-(OH)2- 相似文献
66.
Effects of dissolved carbon dioxide on the integrity of the rumen epithelium: An agent in the development of ruminal acidosis 下载免费PDF全文
The carbon dioxide released and dissolved in rumen fluid may easily permeate across the epithelial cell membrane. Thus, we hypothesized that CO2 may act as proton carrier and induce epithelial damage under acidotic conditions. Ovine ruminal epithelia were mounted in Ussing chambers under short‐circuit conditions. The serosal buffer solution had a constant pH of 7.4 and was gassed either with 100% oxygen or with carbogen (95% O2/5% CO2). The mucosal solution was gassed with either 100% oxygen or 100% carbon dioxide. The mucosal pH was lowered stepwise from 6.6 to 5.0 in the presence or absence of short‐chain fatty acids (SCFA). The transepithelial conductance (Gt) as an indicator of epithelial integrity and the short‐circuit current (Isc) as an indicator of active electrogenic ion transfer were continuously monitored. At an initial mucosal pH of 6.6, there was no significant difference in Gt between the treatment groups. In the absence of both SCFA and CO2, Gt remained constant when the mucosal solution was acidified to pH 5.0. In the presence of SCFA, mucosal acidification induced a significant rise in Gt when the solutions were gassed with oxygen. A small increase in Gt was observed in the mucosal presence of CO2. However, no difference in final Gt was observed between SCFA‐containing and SCFA‐free conditions under carbon dioxide gassing during stepwise mucosal acidification. The SCFA+proton‐induced increase in Gt could also be minimized by serosal gassing with carbogen. Because of the SCFA+proton‐induced changes in Gt and their attenuation by CO2, a protective role for mucosally available carbon dioxide may be assumed. We suggest that this effect may be due to the intraepithelial conversion of carbon dioxide to bicarbonate. However, the serosal presence of CO2 at a physiological concentration may be sufficient to protect the epithelia from SCFA+proton‐induced damage for a certain period of time. 相似文献
67.
本研究采用A ndersen-6级空气微生物样品收集器,选用血-葡萄糖-琼脂培养基为采样介质,对两个不同种兔舍环境空气中需氧菌总数和葡萄球菌总数进行了检测,并对葡萄球菌的菌群组成进行了分析。结果表明,两个兔舍内需氧菌含量分别为1.73~85.8×103CFU/m3、2.71~9.66×103CFU/m3空气,葡萄球菌含量分别为0.94~7.84×103CFU/m3、1.02~6.54×103CFU/m3空气。兔舍空气中葡萄球菌主要包括金黄色葡萄球菌、腐生葡萄球菌、表皮葡萄球菌、科氏葡萄球菌、头状葡萄球菌和马胃葡萄球菌,其中金黄色葡萄球菌的含量占葡萄球菌总数的26.3%~29.6%,其次是腐生葡萄球菌和表皮葡萄球菌。另外,还对需氧菌和金黄色葡萄球菌在A ndersen-6级收集器不同层级上的分布情况进行了统计分析,结果表明,约有56.4%的需氧菌和49%金黄色葡萄球菌分布在3~6层上,空气动力学直径(A erody-nam ic d iam eter,D ae)在6~0.2μm,它们能进入人、畜的气管、支气管,甚至细支气管,对饲养员和动物的呼吸道构成严重危害。 相似文献
68.
本研究无菌采集唐山市某奶牛场临床型乳房炎病牛的奶样30份,对奶样进行了病原菌的分离培养、生化鉴定及药敏试验。从30份奶样中共分离到8种156株细菌,其中金黄色葡萄球菌58株(37.2%)、大肠杆菌17株(10.9%)、表皮葡萄球菌10株(6.4%)、无乳链球菌38株(24.4%)、乳房链球菌15株(9.6%)、停乳链球菌16株(10.3%)、克雷伯氏菌1株(0.6%)、变形杆菌1株(0.6%)。结果表明,葡萄球菌、链球菌为主要病原菌,其次是大肠杆菌,占总菌数的98.7%(154/156);药敏试验结果表明,主要致病菌对中药组方1(M、G)(蒲公英、连翘、瓜蒌、通草、川芎、土贝母、芙蓉叶、金银花、王不留行、当归)、中药组方2(G)(黄芪、党参、当归、通草、川芎、白术、木通、甘草、王不留行、路路通)、中药复方黄连乳腺炎注射液(M)、新霉素呈高度敏感。 相似文献
69.
70.
Objective To develop a lameness model to assess the efficacy of analgesics for alleviating pain, swelling and systemic signs of inflammation in sheep. Procedures The response to subcutaneous injection of 0.1 or 0.2 mL turpentine in a forelimb pastern (n = 4 ewes per dose) was examined at 0, 3, 6, 24, 48 and 72 h. In a second experiment, responses were measured at 0, 2, 4, 6, 8, 10, 12 and 24 h in ewes receiving 0.1 mL turpentine ± meloxicam 1 mg/kg IV at 0 h (n = 6 per group). Responses measured included forceplate pressure, skin temperature, limb circumference, nociception, leucocyte count, neutrophil : lymphocyte ratio, haptoglobin and daily feed intake. Results Turpentine injection caused a decrease in weight borne on the treated limb, increased skin temperature, increased sensitivity at the injection site and leucocytosis by 2 h and increased limb circumference by 4 h. Weight borne and sensitivity of the injected limb returned to control levels after around 24 h, whereas tissue swelling, elevated skin temperature and elevated haptoglobin levels persisted for at least 72 h. Treatment with meloxicam improved weight borne by and tolerance to pressure exerted on the turpentine‐injected limb. Conclusions The local and systemic signs of inflammation and pain, temporary reduction in function of the affected limb and partial amelioration of some of these changes by the dose of meloxicam used here suggest that injection of turpentine in the lower forelimb provides a suitable model for examining the efficacy of analgesics for alleviation of pain and inflammation in sheep. 相似文献