全文获取类型
收费全文 | 81706篇 |
免费 | 4750篇 |
国内免费 | 35篇 |
专业分类
林业 | 4382篇 |
农学 | 2966篇 |
基础科学 | 541篇 |
11316篇 | |
综合类 | 11993篇 |
农作物 | 3031篇 |
水产渔业 | 4542篇 |
畜牧兽医 | 40715篇 |
园艺 | 1216篇 |
植物保护 | 5789篇 |
出版年
2020年 | 682篇 |
2019年 | 794篇 |
2018年 | 1594篇 |
2017年 | 1637篇 |
2016年 | 1510篇 |
2015年 | 1250篇 |
2014年 | 1546篇 |
2013年 | 3270篇 |
2012年 | 2923篇 |
2011年 | 3257篇 |
2010年 | 2148篇 |
2009年 | 2152篇 |
2008年 | 3263篇 |
2007年 | 3003篇 |
2006年 | 2821篇 |
2005年 | 2652篇 |
2004年 | 2696篇 |
2003年 | 2611篇 |
2002年 | 2403篇 |
2001年 | 2581篇 |
2000年 | 2562篇 |
1999年 | 2103篇 |
1998年 | 966篇 |
1997年 | 874篇 |
1996年 | 824篇 |
1995年 | 925篇 |
1994年 | 873篇 |
1993年 | 785篇 |
1992年 | 1586篇 |
1991年 | 1602篇 |
1990年 | 1713篇 |
1989年 | 1558篇 |
1988年 | 1489篇 |
1987年 | 1387篇 |
1986年 | 1427篇 |
1985年 | 1376篇 |
1984年 | 1157篇 |
1983年 | 1062篇 |
1979年 | 1037篇 |
1978年 | 817篇 |
1977年 | 736篇 |
1976年 | 695篇 |
1975年 | 730篇 |
1974年 | 791篇 |
1973年 | 850篇 |
1972年 | 824篇 |
1971年 | 772篇 |
1970年 | 752篇 |
1969年 | 769篇 |
1967年 | 679篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Belobrov V. P. Yudin S. S. Yaroslavtseva N. V. Yudina A. V. Dridiger V. K. Stukalov R. S. Kluev N. N. Zamotaev I. V. Ermolaev N. R. Ivanov A. L. Kholodov V. A. 《Eurasian Soil Science》2020,53(7):968-977
Eurasian Soil Science - This article presents the results of research on the impact of no-till technology on the natural bulk density and macro- and microaggregate composition of the topsoil... 相似文献
992.
ABSTRACT1. The objective of this study was to investigate the effect of supplementing broiler diets with xylanase or xylo- oligosaccharide (XOS) on growth performance, the concentration of non-starch polysaccharide (NSP) hydrolysis products in the ileum and concentration of short chain fatty acids (SCFA) in the caeca of broiler chickens.2. In total, 500 male Ross 308 broilers were used in this 29-day (d) study. The treatments were organised into a 2 × 2 plus 1 factorial arrangement consisting of two additives (xylanase or XOS) at two levels (low or high) plus a control treatment with no additives. This gave five treatments with 100 birds in each treatment group. The diets were slightly deficient in protein by 20 g/kg and energy by 1 MJ/kg.3. On d 14 and 28, two birds per pen were euthanised, the caeca content collected and analysed for short chain fatty acid (SCFA) concentration. On d 29, six birds per pen were euthanised and ileal digesta were collected and analysed for the concentration of NSP fractions.4. On d 14, caecal acetic acid, iso-butyric acid, iso-valeric acid, n-valeric acid and total SCFA concentrations were significantly greater (P ≤ 0.05) when diets were supplemented with XOS compared with xylanase.5. Ileal concentration of arabinose, galactose and glucuronic acid (GlucA2) were significantly greater (P ≤ 0.05) in the insoluble NSP fraction when diets were supplemented with a high level of xylanase, compared with the control treatment. Ileal concentration of fructose was significantly greater (P ≤ 0.05) in the water soluble NSP when a high level of xylanase or low level of XOS were included in the diet compared with the control.6. It was concluded that xylanase and XOS had similar effects on NSP concentration and SCFA in the caeca, although there was little effect on performance. This observation demonstrated further benefits of xylanase supplementation in wheat-based broiler diets beyond digesta viscosity reduction and the release of extra nutrients. 相似文献
993.
Champa P. Wijekoon Binod B. Pageni Melanie L. Kalischuk Newton Z. Lupwayi Lawrence M. Kawchuk 《American Journal of Potato Research》2017,94(3):251-257
Late blight, caused by the oomycete Phytophthora infestans (Mont.) de Bary, is a devastating disease in potato and tomato and causes yield and quality losses worldwide. The disease first emerged in central America and has since spread in North America including the United States and Canada. Several new genotypes of P. infestans have recently emerged, including US-22, US-23 and US-24. Due to significant economic and environmental impacts, there has been an increasing interest in the rapid identification of P. infestans genotypes. In addition to providing details regarding the various phenotypic characteristics such as fungicide resistance, host preference, and pathogenicity associated with various P. infestans genotypes, information related to pathogen movement and potential recombination may also be determined from the genetic analyses. Restriction fragment length polymorphism (RFLP) analysis with the RG57 loci is one of the most reliable procedures used to genotype P. infestans. However, the RFLP procedure requires propagation and isolation of the pathogen and relatively large amounts of DNA. Isolation of the late blight pathogen is sometimes impossible due to the poor condition of the infected tissues or the presence of fungicide residues. In this study, we describe a procedure to identify P. infestans at the molecular level in planta using terminal restriction fragment length polymorphism (T-RFLP) of the RG57 loci. This T-RFLP assay is sufficiently sensitive to detect and differentiate P. infestans genotypes directly in planta without propagation and isolation of the pathogen, to facilitate the timely implementation of best management practices. 相似文献
994.
A salinity‐tolerant japonica cultivar has Na+ exclusion mechanism at leaf sheaths through the function of a Na+ transporter OsHKT1;4 under salinity stress 下载免费PDF全文
995.
Faridy Juárez-Chairez Milagros Stephanie Cid-Gallegos María Gabriela Meza-Márquez Ofelia Cristian Jiménez-Martínez 《Plant foods for human nutrition (Dordrecht, Netherlands)》2020,75(2):142-153
Plant Foods for Human Nutrition - Chickpea is one of the most consumed legumes worldwide. Among their benefits are the high protein concentration that reflects not only at the nutritional level but... 相似文献
996.
Moharana P. C. Jena R. K. Pradhan U. K. Nogiya M. Tailor B. L. Singh R. S. Singh S. K. 《Precision Agriculture》2020,21(2):426-448
Precision Agriculture - Delineation of management zones (MZs) are needed to manage fields in order to maximize economic return, minimize environmental impact, and improve soil and crop management.... 相似文献
997.
Precision Agriculture - An accurate and robust strawberry flower representation and detection scheme is a key step to enable the reliable forecasting of fruit yield for use in precision... 相似文献
998.
Barrera-Reyes Paloma K de Lara Josué Cortés-Fernández González-Soto Melissa Tejero M Elizabeth 《Plant foods for human nutrition (Dordrecht, Netherlands)》2020,75(1):1-11
Plant Foods for Human Nutrition - The effects of cocoa-derived polyphenols on cognitive functions have been analyzed through numerous studies using different interventions (doses, vehicles, time... 相似文献
999.
1000.
New Forests - The coppice is a very flexible cultural system producing several calibers adapting to the demands of the market. Small-caliber roundwood from sweet chestnut (Castanea sativa Mill.)... 相似文献