全文获取类型
收费全文 | 23975篇 |
免费 | 510篇 |
国内免费 | 480篇 |
专业分类
林业 | 4257篇 |
农学 | 1943篇 |
基础科学 | 405篇 |
4061篇 | |
综合类 | 2079篇 |
农作物 | 2517篇 |
水产渔业 | 2181篇 |
畜牧兽医 | 3774篇 |
园艺 | 1318篇 |
植物保护 | 2430篇 |
出版年
2023年 | 48篇 |
2022年 | 101篇 |
2021年 | 154篇 |
2020年 | 188篇 |
2019年 | 180篇 |
2018年 | 2874篇 |
2017年 | 2896篇 |
2016年 | 1357篇 |
2015年 | 251篇 |
2014年 | 219篇 |
2013年 | 373篇 |
2012年 | 1162篇 |
2011年 | 2555篇 |
2010年 | 2481篇 |
2009年 | 1594篇 |
2008年 | 1700篇 |
2007年 | 1908篇 |
2006年 | 358篇 |
2005年 | 414篇 |
2004年 | 372篇 |
2003年 | 425篇 |
2002年 | 402篇 |
2001年 | 317篇 |
2000年 | 300篇 |
1999年 | 203篇 |
1998年 | 120篇 |
1997年 | 94篇 |
1996年 | 98篇 |
1995年 | 91篇 |
1994年 | 79篇 |
1993年 | 115篇 |
1992年 | 128篇 |
1991年 | 100篇 |
1990年 | 98篇 |
1989年 | 93篇 |
1988年 | 75篇 |
1987年 | 69篇 |
1986年 | 49篇 |
1985年 | 57篇 |
1984年 | 63篇 |
1983年 | 55篇 |
1982年 | 53篇 |
1979年 | 39篇 |
1978年 | 45篇 |
1977年 | 48篇 |
1976年 | 43篇 |
1974年 | 41篇 |
1972年 | 35篇 |
1971年 | 34篇 |
1969年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
1. Differences were found among eight populations of White Plymouth Rock pullets in the frequency of broken eggs.
2. The shells of such eggs were thinner than those of intact eggs in seven of the populations.
3. The number of defective eggs, the specific gravity of the eggs, and the percentage hen‐day egg production of normal eggs were significantly correlated within populations with the incidence of broken eggs.
4. No significant correlations were found within populations between the incidence of egg breakage and either egg weight, body weight, or shank length. 相似文献
72.
73.
74.
A CELO-type adenovirus (AV) isolated from fowls with respiratory disease was inoculated experimentally into the tracheas of young birds. No symptoms referable to respiratory infection were evident. Post mortem examination between days 2 and 5 after inoculation revealed pneumonia involving up to 30 per cent of the surface of the lungs. Histologically, a focal to diffuse interstitial lymphocytic infiltration and bronchiolar degeneration were present. Concurrent infections with a mild strain of infectious laryngotracheitis virus (ILT) failed to enhance the pathogenicity of either the AV or ILT infections. 相似文献
75.
两种光周期下矮牵牛‘幻想粉红’生长发育特性的研究 总被引:3,自引:2,他引:3
将矮牵牛‘幻想粉红’分别培养在长日照和短日照条件下, 观测其始花期及株高、株幅、分枝数和开花数的变化; 将短日照下培养的‘幻想粉红’分别于2、4、6、8、10、12、14、16片真叶时移入长日照下进行培养, 观测从长日照处理至第1朵花开放的时间。结果分析表明: 长日照下, ‘幻想粉红’株型松散, 短日照下生长紧凑; ‘幻想粉红’为量性长日照植物, 短日照下要达到较大的营养生长量才能开花; ‘幻想粉红’的幼龄期约在8片真叶期结束。初步建议在8叶期之前采用短日照处理‘幻想粉红’,以得到紧凑的株型, 而在8叶期以后给予长日照, 以促进开花。 相似文献
76.
77.
Tsutomu MATSUMOTO Yuichiro NARA Hiromitsu FURUYA Harumi TAKAHASHI Kiichi TAIRAKO Hideki YAMAMOTO 《Journal of General Plant Pathology》2002,68(4):382-384
L11A-Fukushima (L11A-F) derived from attenuated isolate LuA of Tomato mosaic virus (ToMV) has the highest ability to cross protect against virulent ToMV among LuA and its derivatives and is stably inherited.
Growth, yield, fruit quality and symptom attenuation of inoculated tomato plants did not differ significantly between L11A-F and L11A. The infectivity of progeny viruses in tomato infected with LuA-F was less than 4% of that with virulent ToMV. From these
results, L11A-F appears to possess the properties necessary for practical use. To manage L11A-F strictly, a PCR-based assay to detect trace contamination of virulent ToMV in L11A-F preparations was established.
Received 10 June 2002/ Accepted in revised form 30 October 2002 相似文献
78.
Shohei MATSUURA Shigeru HOSHINO Hideaki HAYASHI Tetsuyuki KOHGUCHI Kyoji HAGIWARA Toshihiro OMURA 《Journal of General Plant Pathology》2002,68(1):99-102
DAS-ELISA proved to be reliable enough to detect a latent infection by Tomato spotted wilt virus (TSWV) in asymptomatic stock plants of chrysanthemum. A high density of Frankliniella occidentalis, the predominant vector, in the presence of latently infected stock plants resulted in a high incidence of disease in the chrysanthemum
production field. The incidence of disease was low when the vector thrips were not abundant in spite of the presence of latently
infected stock plants. These results suggest that an infestation of the vector thrips causes severe secondary spread of TSWV
originating from latently infected stock plants in chrysanthemum production fields.
Received 27 July 2001/ Accepted in revised form 27 November 2001 相似文献
79.
20%多效唑·甲哌Wong微乳剂防止小麦倒伏和增产机理研究 总被引:2,自引:0,他引:2
冬小麦二棱期喷施植物生长调节剂20%多效唑·甲哌鎓微乳剂375 mL/hm2,可以显著抑制茎秆基部节间伸长,增加各节间充实度,其中赤霉素(Gas)和生长素(IAA)降低,可显著增强小麦抗倒伏能力和降低田间倒伏率.处理还协调了穗数、穗粒数和粒重的关系,增产幅度6.2%~28.6%.增产原因可能在于促进籽粒灌浆强,增加籽粒中内源Gas、IAA、细胞分裂素(CTKs)的水平,增强了籽粒库活性,同时促进茎叶中干物质向籽粒运转. 相似文献
80.