全文获取类型
收费全文 | 3771篇 |
免费 | 291篇 |
国内免费 | 240篇 |
专业分类
林业 | 216篇 |
农学 | 173篇 |
基础科学 | 153篇 |
412篇 | |
综合类 | 1336篇 |
农作物 | 258篇 |
水产渔业 | 229篇 |
畜牧兽医 | 1161篇 |
园艺 | 209篇 |
植物保护 | 155篇 |
出版年
2024年 | 15篇 |
2023年 | 59篇 |
2022年 | 130篇 |
2021年 | 139篇 |
2020年 | 125篇 |
2019年 | 123篇 |
2018年 | 91篇 |
2017年 | 166篇 |
2016年 | 117篇 |
2015年 | 132篇 |
2014年 | 189篇 |
2013年 | 218篇 |
2012年 | 252篇 |
2011年 | 295篇 |
2010年 | 278篇 |
2009年 | 225篇 |
2008年 | 259篇 |
2007年 | 221篇 |
2006年 | 182篇 |
2005年 | 164篇 |
2004年 | 121篇 |
2003年 | 108篇 |
2002年 | 100篇 |
2001年 | 98篇 |
2000年 | 80篇 |
1999年 | 43篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1995年 | 8篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1986年 | 15篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1981年 | 10篇 |
1979年 | 15篇 |
1977年 | 7篇 |
1975年 | 11篇 |
1974年 | 17篇 |
1973年 | 12篇 |
1972年 | 10篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 8篇 |
1967年 | 7篇 |
1966年 | 10篇 |
排序方式: 共有4302条查询结果,搜索用时 15 毫秒
1.
2.
3.
Epidemiological studies of piglet diarrhoea in intensively managed Danish sow herds. II. Post-weaning diarrhoea 总被引:1,自引:0,他引:1
This study comprised 48,931 litters in 89 sow herds. During the study (1976-82) weaning age decreased from approx. 42 days to approx. 30 days. The mean incidence of post-weaning diarrhoea was 6.0% of litters weaned, with little variation by year but with considerable variation among herds. Within the individual herd increased incidence occurred over limited periods, probably associated with specific infections. Litters with diarrhoea during the suckling period had increased risk of post-weaning diarrhoea. The incidence of post-weaning diarrhoea increased with litter size at weaning. Thus, a litter of 11-12 piglets at weaning had 1.2 times higher risk than litters with 8-10 piglets. In contrast to pre-weaning diarrhoea, there was no association between parity of the sow and diarrhoea in the litter after weaning. Litters weaned below 2 weeks of age had a 2-fold risk of developing diarrhoea after weaning and a 2.4-fold higher mortality rate than did litters weaned at 6-7 weeks. Similarly, litters weaned at an individual piglet weight below 3 kg bodyweight had a 3-fold higher risk of developing diarrhoea after weaning and a 5-fold higher mortality rate than did pigs from litters weaned at a bodyweight of 7-8 kg. The incidence of post-weaning diarrhoea decreased with increasing herd size. Piglets from litters with post-weaning diarrhoea had reduced weight gains after weaning and were 2.3 days older at 25 kg bodyweight than piglets from non-diarrhoeic litters. Likewise, diarrhoea after weaning was associated with an increased incidence of diseases of the skin and respiratory tract. Thus the risk of contracting respiratory disease was 4 times greater in diarrhoeic litters. 相似文献
4.
S Rosendal P L Frandsen J P Nielsen R Gallily 《Canadian journal of veterinary research》1995,59(2):154-156
Pasteurella multocida toxin (PMT) is the major virulence factor in Progressive Atrophic Rhinitis of swine. Other workers' previous findings that PMT was mitogenic for 3T3 fibroblasts, were confirmed in the present study. In addition, PMT stimulated 3T3 cells to release IL-6, but IL-1 alpha or TNF alpha were not detected in fibroblast supernatants sampled 24, 48, or 72 h after stimulation. In view of the role of IL-6 in osteoclastic bone resorption, these findings provide a new working hypothesis for investigations into the molecular pathogenesis of this important disease. 相似文献
5.
A haematological disorder in a dog characterised by a massive leucocytosis, mainly composed of eosinophils and their precursors is reported here. The normal composition of cells in the bone marrow was displaced in favour of the eosinophils and their precursors. No apparent cause for the pronounced eosinophilia could be determined by clinical, haematological, clinical-chemical, radiological or pathological examinations. A diagnosis of eosinophilic leukaemoid reaction was suggested as the criteria for the diagnosis of eosinophilic leukaemia in the dog but this was not firmly established. 相似文献
6.
参考 Genbank收录的 TGEV- Miller株的基因序列 ,自行设计合成 1对引物 (TGEVP5 /P6 ) ,对不同代次的 TGEV疫苗弱毒 STC3及种毒 、种毒 进行了 RT- PCR扩增 ,产物经琼脂糖凝胶电泳分析 ,均出现 1条大约 12 6 2 bp的目的条带 ,经 Eco R 酶切 ,都产生了 871bp和391bp左右的两个片段 ,与预期大小相符。将种毒 RT- PCR扩增目的条带回收纯化后克隆入PMD18- T载体中 ,转化宿主菌 DH5 α,挑选阳性克隆 (命名为 PTs) ,提取重组质粒 ,用 Hpa 、Eco R 对重组质粒进行酶切鉴定以及 PCR扩增 ,然后进行序列测定 ,并进行了序列分析 ,证实与国外标准毒株 Miller、Fs772 / 70、Purdue、TO14等有较高的同源性 相似文献
7.
抗霉菌素“120”是一种新的农用抗菌素,防治农作物上多种病害都有效。实验室试验证明;本剂与杀灭菌酯混用,对防治病害和虫害的效果没有不良影响,因此可以减少打药次数,有一定经济意义。 相似文献
8.
9.
10.
AIM: To investigate the effect of cGMP on voltage-gated potassium channel in pulmonary artery smooth muscle cells (PASMCs) from rats exposed to chronic hypoxia. METHODS: (1) Wistar rats were randomly divided into control group (group A) and chronic hypoxia group (group B). Then group B received hypoxia 8 hours per day for 4 consecutive weeks. (2) Single PASMC was obtained via acute enzyme separation method. (3) Conventional whole-cell patch clamp technique was used to record resting membrane potential (Em) and ion currents of voltage-gated potassium channel. The changes of ion currents of voltage-gated potassium channel before and after applying cGMP (1 mmol/L), an agonist of protein kinase G (PKG), and cGMP plus H-8 (1 mmol/L), an inhibitor of PKG were compared between two groups. RESULTS: The Em of group B were significantly lower than that of group A. The ion currents of voltage-gated potassium channel in group A and group B were all significantly inhibited by cGMP [control group: from (118.0±5.0) pA/pF to (89.9±16.5) pA/pF, n=6, P<0.05;chronic hypoxia group: from (81.0±5.0) pA/pF to (56.8±9.1) pA/pF, n=6, P<0.05]and these effects were reversed by H-8 [control group: from (119.2±10.3) pA/pF to (117.8±9.1) pA/pF, n=6, P>0.05;chronic hypoxia group: from (96.8±6.2) pA/pF to (98.0±2.2) pA/pF, n=6, P>0.05]. CONCLUSIONS: The currents of voltage-gated potassium channel was inhibited by chronic hypoxic. The inhibitory effect of cGMP on currents of voltage-gated potassium channel in PASMCs from both normal and chronic hypoxic rats may be probably through the phosphorylation of voltage-gated potassium channel. 相似文献