全文获取类型
收费全文 | 3106篇 |
免费 | 212篇 |
国内免费 | 388篇 |
专业分类
林业 | 391篇 |
农学 | 335篇 |
基础科学 | 136篇 |
356篇 | |
综合类 | 1376篇 |
农作物 | 203篇 |
水产渔业 | 223篇 |
畜牧兽医 | 246篇 |
园艺 | 256篇 |
植物保护 | 184篇 |
出版年
2024年 | 16篇 |
2023年 | 78篇 |
2022年 | 111篇 |
2021年 | 141篇 |
2020年 | 135篇 |
2019年 | 151篇 |
2018年 | 103篇 |
2017年 | 141篇 |
2016年 | 195篇 |
2015年 | 154篇 |
2014年 | 173篇 |
2013年 | 228篇 |
2012年 | 249篇 |
2011年 | 242篇 |
2010年 | 188篇 |
2009年 | 173篇 |
2008年 | 170篇 |
2007年 | 160篇 |
2006年 | 126篇 |
2005年 | 109篇 |
2004年 | 81篇 |
2003年 | 80篇 |
2002年 | 75篇 |
2001年 | 60篇 |
2000年 | 65篇 |
1999年 | 35篇 |
1998年 | 30篇 |
1997年 | 30篇 |
1996年 | 29篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有3706条查询结果,搜索用时 15 毫秒
61.
62.
A. K. Thakur S. Rath S. Roychowdhury N. Uphoff 《Journal of Agronomy and Crop Science》2010,196(2):146-159
The System of Rice Intensification (SRI) reportedly enhances the yields of rice (Oryza sativa L.) through synergy among several agronomic management practices. This study was conducted to investigate the effects on rice plant characteristics and yield by comparing the plants grown with different methods of cultivation – SRI vs. recommended management practices (RMP) focusing on the impact of different plant spacings. Performance of individual hills was significantly improved with wider spacing compared with closer‐spaced hills in terms of root growth and xylem exudation rates, leaf number and leaf sizes, canopy angle, tiller and panicle number, panicle length and grain number per panicle, grain filling and 1000‐grain weight and straw weight, irrespective of whether SRI or RMP was employed. Both sets of practices gave their highest grain yield with the spacing of 20 × 20 cm; however, SRI yielded 40 % more than the recommended practice. At this spacing, canopies also had the highest leaf area index (LAI) and light interception during flowering stage. The lowest yield was recorded at 30 × 30 cm spacing under both the practices, as a result of less plant population (11 m?2), despite improved hill performance. During the ripening stage, hills with wider spacing had larger root dry weight, produced greater xylem exudates, and transported these towards shoot at faster rates. These features contributed to the maintenance of higher chlorophyll levels, enhanced fluorescence and photosynthesis rates of leaves and supported more favourable yield attributes and grain yield in individual hills than in closely‐spaced plants. Moreover, these parameters further improved in SRI, apart from the enhanced percentage of effective tillers and showed substantial and positive impacts on grain yield (17 %) compared with recommended practice. In conclusion, wide spacing beyond optimum plant density, however, does not give higher grain yield on an area basis and for achieving this, a combination of improved hills with optimum plant population must be worked out for SRI. 相似文献
63.
64.
在简单介绍农作物光照特性的基础上,总结了我国近几十年来光技术在农业种植中的应用和发展情况,指出了目前存在的不足,并分析了未来的发展趋势。 相似文献
65.
本文主要对单体用钢量大、楼层高的多层写字楼的施工进行技术分析,为今后此类型工业建筑施工工艺水平的提高提供成功的经验。 相似文献
66.
芦笋茎枯病病原菌及其生物学研究 总被引:2,自引:1,他引:2
芦笋茎枯病是一种分布广、为害重的毁灭性病害。研究证实,临沂市芦笋茎枯病病原为Phoma asparagi Sacc.。该菌分生孢子发芽和菌丝生长适温为23—26℃,致死温度分别为50℃10分钟和60℃10分钟,发芽和生长最适pH为7。分生孢子生长在分生孢子器内,单个分生孢子常温下可活10天,菌块内可活25天,孢子器内则长达240天。分生孢子在蒸馏水中不发芽,加糖液发芽率略有提高,在文竹和芦笋茎煮液中发芽率最高;条件适宜时2小时产生芽突,5小时发芽率达98.21%。 相似文献
67.
Light, temperature and burial depth effects on Rumex obtusifolius seed germination and emergence 总被引:1,自引:0,他引:1
Trials were carried out to investigate the effects of light and temperature on germination of Rumex obtusifolius L. After several months of storage, seeds gradually lost dormancy and became photosensitive. Thermal optima for germination were between 20 °C and 25 °C in light or in darkness. At lower temperatures there was a greater demand for light, so that the greatest differences in germination percentage (between low and high temperatures) were found within the 10–15 °C temperature range. The calculated thermal minima ( x -intercept method) in light and darkness were 8.3 °C and 6.1 °C respectively. Daily temperature fluctuation increased germination even after seed irradiation with far-red light, suggesting a lower demand for the far-red-absorbing form of phytochrome. Seed burial inhibited germination in proportion to depth; however, germination inhibition was independent of seed phytochrome photo-equilibrium, which had been diversified by seed pretreatment with light. Seedlings did not emerge when seeds were buried >8 cm deep. Recovery of ungerminated seeds showed that excessive burial did not impede seedling emergence but rather prevented seed germination. However, this induction of dormancy was lost once germination processes were activated (24–48 h at 20 °C) that made germination irreversible. Temperature was also involved in inhibition, and low temperature (<15 °C) induced the least inhibition. This is discussed in terms of processes of respiration and fermentation in buried seeds. 相似文献
68.
M. Van Oijen 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(1):3-11
A field experiment with three potato cultivars, where plants were inoculated withPhytophthora infestans, was used to parameterize a model of potato growth and blight population dynamics. The model was validated by accurately simulating a field experiment conducted in another year. Sensitivity analysis with the model showed that late cultivars are longer able to maintain a green canopy in the presence of disease, but still suffer more yield loss than early cultivars. The level of partial resistance of a cultivar was more important than its level of tolerance, and other plant characteristics. The model calculations showed that only between 4 and 15% of the yield loss in the experiments was due to accelerated leaf senescence caused by the disease; the major part of the loss was caused by lesion coverage of leaves. 相似文献
69.
在玉米光热生产潜力的基础上,进一步讨论沈阳地区水分对玉米生产潜力发挥的限制作用,结果表明:水分的限制率为18.5%,使玉米经济产量降低395.01kg/mu。 相似文献
70.