全文获取类型
收费全文 | 69379篇 |
免费 | 2569篇 |
国内免费 | 5447篇 |
专业分类
林业 | 8876篇 |
农学 | 7572篇 |
基础科学 | 4365篇 |
10101篇 | |
综合类 | 20387篇 |
农作物 | 5207篇 |
水产渔业 | 4117篇 |
畜牧兽医 | 8444篇 |
园艺 | 3459篇 |
植物保护 | 4867篇 |
出版年
2024年 | 269篇 |
2023年 | 750篇 |
2022年 | 1820篇 |
2021年 | 2246篇 |
2020年 | 2079篇 |
2019年 | 2067篇 |
2018年 | 4052篇 |
2017年 | 4936篇 |
2016年 | 2958篇 |
2015年 | 2657篇 |
2014年 | 2705篇 |
2013年 | 3084篇 |
2012年 | 4852篇 |
2011年 | 6395篇 |
2010年 | 6082篇 |
2009年 | 4713篇 |
2008年 | 4719篇 |
2007年 | 4769篇 |
2006年 | 2777篇 |
2005年 | 2254篇 |
2004年 | 1298篇 |
2003年 | 1142篇 |
2002年 | 1062篇 |
2001年 | 963篇 |
2000年 | 977篇 |
1999年 | 884篇 |
1998年 | 735篇 |
1997年 | 570篇 |
1996年 | 511篇 |
1995年 | 486篇 |
1994年 | 389篇 |
1993年 | 387篇 |
1992年 | 309篇 |
1991年 | 252篇 |
1990年 | 248篇 |
1989年 | 248篇 |
1988年 | 184篇 |
1987年 | 101篇 |
1986年 | 90篇 |
1985年 | 89篇 |
1984年 | 63篇 |
1983年 | 59篇 |
1982年 | 46篇 |
1981年 | 42篇 |
1980年 | 23篇 |
1979年 | 7篇 |
1977年 | 6篇 |
1963年 | 5篇 |
1962年 | 5篇 |
1956年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
93.
牛副结核检疫中的非特异性干扰 总被引:2,自引:0,他引:2
给犊牛接种各种分枝杆菌,然后以副结核PPD进行变态反应试验,观察各分枝杆菌感染对副结核变态反应的干扰;从各种分枝杆菌感染牛群采取血清进行副结核ELISA检测,以观察各分枝杆菌血清对牛副结核ELISA的干扰。结果:多种分枝杆菌,特别是鸟胞内分枝杆菌、瘰疬分枝杆菌的感染可干扰副结核变态反应;部分结核牛血清干扰副结核ELISA的检测 相似文献
94.
LFA—3和IL—2对机体免疫增强作用 总被引:1,自引:0,他引:1
以绵羊红细胞膜提取的LFA-3和猪外周血单个核细胞所产生的IL-2,同时或分别与新城疫Ⅳ系疫苗胸肌注射22日龄雏鸡,测定鸡体HI抗体效阶及Etg花环形成率的变化,结果表明,LFA-3组抗体效价与对照组差异极显著,IL-2也可显著提高IV系苗免疫后HI抗体效价,且两者的作用具有剂量依赖性。 相似文献
95.
以市场上流行的6种搅拌型酸奶为研究对象,对其流变学特性及质构特性进行了初步的研究.结果表明:6种酸乳的剪切应力值在升速和降速过程中都能形成触变环,表观粘度在升速过程中随剪切应力的增大而逐渐降低,降速过程中随着剪切速率的降低而升高;酸奶在16 r/min的剪切速率下,转速和相应的表观粘度符合幂率定律,进一步发现搅拌型酸奶具有时间触变性,是一种正触变性流体.由触变环的面积可知,6种搅拌型酸奶的触变性大小:S5>S4>S2>S1>S3>S6,触变性的大小对样品的口感有非常重要的影响.此外,酸奶的流变学分析得出口感较好的酸奶粘度值应在540.56~674.25 mpa·s范围内;酸奶质构分析发现口感较好的酸奶硬度在33.9~39.9 g范围内. 相似文献
96.
97.
Silvia Pietschmann Katrin Hoffmann Michael Voget Ulrich Pison 《Veterinary research communications》2009,33(6):489-505
The therapeutic value of antibiotics depends on the susceptibility of the infecting microorganism and the pharmacological
profile of the drugs. To assess the value of an antibiotic combination of polymyxin B and miconazole this study examined the
in vitro synergistic potential of the two drugs on Gram-negative and Gram-positive bacteria and yeast. Antifungal and antibacterial
activity was tested by minimum inhibitory concentration (MIC) of broth macrodilution and urea broth microdilution, by fluorescence
microscopy and flow cytometry. Synergism was calculated using the fractional inhibitory concentration index (FICi). With Staphylococcus intermedius as target we found up to an eightfold reduction of the individual MICs when both drugs were combined. However, the FICi was
0.63 suggesting no real interaction between the two drugs. With Escherichia coli, Pseudomonas aeruginosa, and Malassezia pachydermatis as targets the antimicrobial drug combination reduced the MICs of polymyxin B and miconazole from fourfold to hundredfold
resulting in FICi between 0.06 and 0.5 which defines a synergistic action. Thus, if polymyxin B and miconazole are combined
their effect is greater than the sum of the effects observed with polymyxin B and miconazole independently, revealing bactericidal
and fungicidal synergism. Our results indicate a strong therapeutic value for the combination of these antimicrobial agents
against Gram-negative bacteria and yeast and a weaker value against Gram positive bacteria for clinical situations where these
pathogens are involved. 相似文献
98.
99.
Denis M Lacy-Hulbert SJ Buddle BM Williamson JH Wedlock DN 《Veterinary research communications》2011,35(3):145-156
The presence, phenotype and function of Streptococcus uberis-specific T cells in the mammary gland secretion (MGS) and blood of cows exposed to S. uberis were assessed. MGS T cells in the udder were purified and incubated with autologous blood monocytes as antigen-presenting
cells (APC). Most cows, irrespective of prior S. uberis infection status and lactation status, were shown to have S. uberis-specific T cells both in MGS and in the blood. When cells from a subgroup of cows were studied, it was found that the S. uberis-specific T cells produced high levels of interferon-gamma (IFN-γ), but low levels of interleukin-10 (IL-10). A high percentage
of responding T cells were of the CD8
+
memory (CD45RO) subset. T cells from the MGS specific for S. uberis were propagated from animals during the drying off period and expanded in vitro using interleukin-2 (IL-2) and S. uberis antigens. This led to the accumulation of T cells of the CD8
+
subset bearing memory cell markers (CD45A
−
, CD45RO
+
), which released high levels of IFN-γ. Four of the five T cell lines derived from the MGS of three animals had substantial
direct killing activity towards S. uberis in vitro. It is concluded that there is an emergence of S. uberis-specific bactericidal T cells in the MGS of cows after infection or environmental exposure to S. uberis. Vaccines aimed at activating and expanding this T cell population in the mammary glands of cattle may offer an avenue for
the prevention of mastitis caused by S. uberis. 相似文献
100.