全文获取类型
收费全文 | 892篇 |
免费 | 91篇 |
专业分类
林业 | 116篇 |
农学 | 34篇 |
267篇 | |
综合类 | 5篇 |
农作物 | 57篇 |
水产渔业 | 80篇 |
畜牧兽医 | 333篇 |
园艺 | 20篇 |
植物保护 | 71篇 |
出版年
2023年 | 10篇 |
2022年 | 8篇 |
2021年 | 30篇 |
2020年 | 32篇 |
2019年 | 22篇 |
2018年 | 79篇 |
2017年 | 69篇 |
2016年 | 77篇 |
2015年 | 48篇 |
2014年 | 52篇 |
2013年 | 66篇 |
2012年 | 64篇 |
2011年 | 86篇 |
2010年 | 40篇 |
2009年 | 17篇 |
2008年 | 31篇 |
2007年 | 34篇 |
2006年 | 23篇 |
2005年 | 35篇 |
2004年 | 28篇 |
2003年 | 27篇 |
2002年 | 25篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有983条查询结果,搜索用时 109 毫秒
981.
Gołkowski F Buziak-Bereza M Trofimiuk M Bałdys-Waligórska A Szybiński Z Huszno B 《Public health nutrition》2007,10(8):799-802
OBJECTIVE: To assess the prevalence of hyperthyroidism just after implementation of iodine prophylaxis among adults from an area with iodine deficiency. STUDY DESIGN AND SUBJECTS: A total of 1648 adults (age 16 years and older) were sampled from an area of southern Poland during two nationwide epidemiological surveys. Of these, 1424 adults with negative medical history for thyroid disorders qualified for final analysis. The authors compared thyroid dysfunction in participants prior to (1989-1990) and after implementation of iodine prophylaxis (1997-1999). SETTING: The southern part of Poland. RESULTS: We found an increase in the serum concentration of anti-thyroid microsomal antibodies from 4.9% in the years 1989-1990 to 12.1% after introduction of iodised household salt (P < 0.0001). The prevalence of hyperthyroidism (defined as thyroid-stimulating hormone < 0.4 microU ml- 1) significantly increased in the equivalent period from 4.8 to 6.5% (P = 0.009). CONCLUSIONS: We concluded that a sudden rise in iodine intake after implementation of iodine prophylaxis among adults from the area with iodine deficiency may lead to an increase in thyroid autoimmunity and prevalence of hyperthyroidism. Those possible early side-effects appear to be only temporary and are acceptable when compared with the evident benefits of adequate iodine intake. 相似文献
982.
Karol Trejchel Daniel Żarski Katarzyna Palińska-Żarska Sławomir Krejszeff Bartłomiej Dryl Krzysztof Dakowski Dariusz Kucharczyk 《Aquaculture International》2014,22(1):195-203
The aim of the study was to optimize burbot juveniles rearing in recirculating aquaculture system. In experiment 1 (17 °C, photoperiod 24L:0D), the fish (initial: body weight [W] = 15.36 ± 3.72 g, standard length [SL] = 12.48 ± 1.09 cm) were divided into four groups (I, II, III and IV). Different feeding levels were applied: 1, 2, 3 and 4 % of biomass daily (counted based on dry feed weight). The feed conversion ratio (FCR) and specific growth rate (SGR) were recorded. In experiment 2 (17 °C, feeding level of 2 % of biomass day?1), fish (W = 5.24 ± 2.43 g and SL = 8.54 ± 1.24 cm) were divided into two groups where different light conditions were applied (I: 24 h light [1,800 lx] and II: 24 h darkness [4 lx]). In experiment 1, the highest SGR was recorded in group II (1.93 % day?1), whereas the lowest SGR (1.27 % day?1) and final W (P < 0.05) was in I group. The lowest (P < 0.05) FCR (0.63) was in group II. In the remaining groups, FCR was similar (0.68–0.70, P > 0.05). The feed consumption in group I reached 100 %, in group II, it was 71.3 % (P < 0.05) and it was the lowest in groups III (39.26 %) and IV (36.93 %). In experiment 2 no differences in the growth and survival rate were recorded (final SL between 14.16 and 14.19 cm, P > 0.05; W between 23.33–23.35 g; P > 0.05). The results from experiment 1 indicate that the feeding 2 % of biomass day?1 was the most efficient. Also, it was proven, for the first time, that there was no effect of using different constant light conditions. 相似文献
983.
Effect of soil drought on growth and yield of maize (Zea mays L.) hybrids grown under compacted soil
Maciej T. Grzesiak Tomasz Hura Anna Maksymowicz Kinga Dziurka Grzegorz Rut Andrzej Rzepka Stanisław Grzesiak 《Journal of Agronomy and Crop Science》2023,209(2):300-315
In this study, we examined responses of maize hybrids differing in susceptibility to soil compaction and drought in the case of their separate or combined action. We ran field and greenhouse experiments and determined effects on grain yield, biomass, weight of 1000 grains, shoot and roots dry matter (DM), shoot-to-roots ratio, harvest index, plant height, emergence index, leaf area and greening and root number and length. Individual and combined effects of both stresses were observed in the field and greenhouse. Compared with plants growing in loose soil and optimal irrigation (LI), the resistant hybrids in treatments HI, LD and HD showed a smaller reduction in GY, BY, S, R, RN and RL than the sensitive. In both groups, stress influence on HA, W-1000, LA and SPAD was smaller and the differences were insignificant. Compared with LI treatment, the roots of LD, HI and HD increased their DM, number and length in the upper level of the soil profile and the number of roots developed at 0–30° and 30–60° in relation to the root main axis. Analysis of those traits in the hybrids resistant and sensitive to both stress factors enabled to explain a defence response. Our study demonstrated that soil compaction and soil drought, which usually occurs simultaneously, caused significant changes in components of plant yield and showed plant plasticity in response to environmental factors under natural conditions. 相似文献