全文获取类型
收费全文 | 5738篇 |
免费 | 206篇 |
国内免费 | 242篇 |
专业分类
林业 | 1116篇 |
农学 | 396篇 |
基础科学 | 78篇 |
518篇 | |
综合类 | 2676篇 |
农作物 | 266篇 |
水产渔业 | 47篇 |
畜牧兽医 | 284篇 |
园艺 | 503篇 |
植物保护 | 302篇 |
出版年
2024年 | 19篇 |
2023年 | 64篇 |
2022年 | 98篇 |
2021年 | 101篇 |
2020年 | 129篇 |
2019年 | 143篇 |
2018年 | 71篇 |
2017年 | 165篇 |
2016年 | 233篇 |
2015年 | 209篇 |
2014年 | 300篇 |
2013年 | 346篇 |
2012年 | 516篇 |
2011年 | 515篇 |
2010年 | 405篇 |
2009年 | 442篇 |
2008年 | 349篇 |
2007年 | 373篇 |
2006年 | 307篇 |
2005年 | 220篇 |
2004年 | 187篇 |
2003年 | 133篇 |
2002年 | 118篇 |
2001年 | 69篇 |
2000年 | 98篇 |
1999年 | 93篇 |
1998年 | 81篇 |
1997年 | 54篇 |
1996年 | 76篇 |
1995年 | 48篇 |
1994年 | 39篇 |
1993年 | 38篇 |
1992年 | 25篇 |
1991年 | 22篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1955年 | 5篇 |
排序方式: 共有6186条查询结果,搜索用时 0 毫秒
101.
论述了原住民利用饲用植物资源的传统知识和经验的民族植物学研究价值,提出了我国饲用植物资源的民族植物学研究的主要内容,并以内蒙古阿鲁科尔沁旗的研究结果作了案例进行了深入的探讨。 相似文献
102.
103.
通过多年对河南省木通属药用植物资源种类、生境、分布的调查,查明了河南木通属药用植物有2种1亚种,介绍了其生药性状的鉴定方法,探讨了木通属植物的药用特性和应用价值,并提出了开发利用的建议. 相似文献
104.
《Communications in Soil Science and Plant Analysis》2012,43(17-18):2673-2687
Mandated processing of waste by‐products in the United States has inspired national interest in addressing the effectiveness of using composted biosolids and yard trimmings to grow containerized plants. Diamond bay Chinese evergreen (Aglaonema ‘Diamond Bay’) was transplanted in containers filled with one of eight formulated media (components added by volume). Medium 1 was a standard mix commonly used in Aglaonema production (5:2:3 peat–vermiculite–perlite); medium 2 was formulated on site to contain peat–bark–stalite–rice hulls–coir (2:2:3:1:2); media 3 and 4 contained 40% biosolid–yard waste compost instead of peat and with or without 20% stalite, respectively; and media 5, 6, 7, and 8 were commercially formulated to contain peat–bark–perlite–rice hulls–coir (4:1.5:2.5:1:1, 4:1.5:2.5:1:1, 4:2:2:1:1, and 3.0:2.5:2:1:1.5, respectively). Physical and chemical properties of the eight media were in ranges 50–65% container water‐holding capacity, 2.9–7.8% air‐filled porosity, 55–80% moisture (w/w), 0.11–0.37 g·cm3 bulk density, 0.34–0.96 g·cm3 particle density, 4.2–7.2 pH, 0.12–4.4 dS·m?1 electrical conductivity (EC), 27.3–54.5 meg/100 g cation exchange capacity (CEC), 17.9–39.0% carbon (C), and 0.22–1.7% nitrogen (N). Medium 4 (40% compost) had 5.5 times more ammoniacal N (NH4‐N) and 1.7 times more nitrate N (NO3‐N) than that of the standard commercial mix. At week 8, plants grown in media 2 and 5 were 8.9% to 9.5% taller than plants grown in medium 1 (commercial standard). At week 16, there were no significant differences in plant heights or growth indices among media. At week 24, there were no significant differences in plant height, growth index, visual quality, shoot dry weight, and root dry weight among media. However, cumulative phosphorus (P) leaching from media 1, 4, and 5 was significantly more than leaching from media 2 and 8. This study suggests that compost may serve as a horticulturally suitable and cost‐effective alternative to peat‐based media for Aglaonema production. 相似文献
105.
ISSR和SRAP标记技术在葫芦科植物种质资源研究中的应用 总被引:1,自引:0,他引:1
阐述了简单重复序列间扩增(ISSR)和相关序列扩增多态性(SRAP)分子标记技术的基本原理和特点,综述与探讨了分子标记技术在葫芦科植物种质资源的亲缘关系鉴定与遗传多样性分析、分子遗传图谱的构建与目的性状基因的标记定位、基因库的构建和基因克隆、辅助育种选择及品种纯度鉴定等研究领域的广泛利用与推广,以期更合理高效地保护和利用葫芦科植物种质资源。 相似文献
106.
M. Hühn 《Journal of Agronomy and Crop Science》1999,182(2):89-98
Based on several simplifying assumptions, a stochastic approach was developed which allows an estimation of the effects of nonregular spatial patterns of the distribution of individual plants on yield per area (F). In this approach, two random variables were attached to each plant: single plant yield (E) and individual space per plant (A). The latter was estimated by the area of Thiessen polygons. Yield per area was calculated theoretically by the expectation of the ratio E / A. Appropriate approximations of this expectation depend on the means (ē and ā), coefficients of variation (vE and vA) of E and A and their correlation (rEA). Yield per area can be decomposed into two additive terms: the first term gives the commonly used estimate ē/ā— or h(ā)/ā if a functional relationship between E and A is assumed: E = h(A). In this study, the two relationships E = k1 + k2 · ln A and E = A/(k3 + k4A) were used (with appropriately chosen constants k1, k2, k3, and k4). The second term in the decomposition of F can be interpreted as the effect of variable individual plant spaces on yield per area. In this paper, all theoretical concepts and results were applied to 17 experimental data sets of three cultivars of winter oilseed rape (Brassica napus L.). Single plant yields (E) and individual plant areas (A) were positively correlated with correlation coefficients from 0.64 up to 0.91. The ranges for both coefficients of variation were similar: 0.27 ≤ vE ≤ 0.65 and 0.28 ≤ vA ≤ 0.59. One obtains no significant differences in the goodness-of-fit for both tested relationships between E and A although the logarithmic relationship seems to be slightly superior. For only three data sets one obtains negative values for the percentage of the second term in the decomposition of F. This indicates an overestimation of yield per area by the commonly used estimates h(ā)/ā and ē/ā, respectively. These overestimations, however, are less than 5 %. In all other cases with positive values for the second term the yield per area is underestimated by the common estimates. For almost all data sets, however, the percentages of F which are explained by the common estimates are much larger than 90 %. 相似文献
107.
A. M. Abu-Awwad 《Journal of Agronomy and Crop Science》1999,183(1):1-7
Caused by the necessarily imperfect seed placement accuracy of sowing machines and, additionally, caused by many other biotic and abiotic factors, the resulting plant stands exhibit nonregular spatial distributions of its plants. Based on several simplifying assumptions, a stochastic approach is developed which allows an estimation of the effects of nonregular spatial patterns on yield per area. In this approach, two random variables are attached to each plant: single plant yield E and individual space A . The latter is estimated by the area of Thiessen polygons. Yield per area, calculated by the expectation of the ratio E/A , can be approximately expressed dependent on the means ( Ē and Ā ) and coefficients of variation ( v E and v A ) of E and A and their correlation ( r EA ). In relation to the commonly used estimate Ē/Ā for yield per area, one obtains yield decreases if v A / v E < r EA . This inequality, however, will be usually valid in the field of applications. The theoretical approaches and results were applied to three experimental data sets for drilled seeds of winter oilseed rape ( Brassica napus L.) (plant density: 60 plants m−2 , row distance: 10 cm). These data sets are characterized by different accuracies of longitudinal distributions within rows (58 %, 101 %, 150 %): yield depression increases with an increasing variability of plant distances within rows. 相似文献
108.
柚矮化病的品种感病性调查 总被引:2,自引:0,他引:2
以特征性症状春梢叶片扭曲畸形和枝条茎陷点为诊断依据,调查结果表明,55个柚类品种中有22个发病,占调查品种数的40%;28个沙田柚砧穗组合中有22个发病,占调查砧穗组合数的78.5%。以沙田柚实生苗和酸柚实生苗作指示植物,对温州蜜柑上的类似矮化病的叶片扭曲症状进行鉴定的结果,指示植物上表现出与接种沙田柚矮化病病原的指示植物相似的春梢叶片扭曲及茎陷点症状。 相似文献
109.
110.