全文获取类型
收费全文 | 623篇 |
免费 | 37篇 |
国内免费 | 47篇 |
专业分类
林业 | 75篇 |
农学 | 102篇 |
基础科学 | 31篇 |
75篇 | |
综合类 | 204篇 |
农作物 | 45篇 |
水产渔业 | 28篇 |
畜牧兽医 | 101篇 |
园艺 | 17篇 |
植物保护 | 29篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 20篇 |
2020年 | 22篇 |
2019年 | 26篇 |
2018年 | 16篇 |
2017年 | 17篇 |
2016年 | 16篇 |
2015年 | 16篇 |
2014年 | 24篇 |
2013年 | 33篇 |
2012年 | 32篇 |
2011年 | 41篇 |
2010年 | 49篇 |
2009年 | 49篇 |
2008年 | 54篇 |
2007年 | 29篇 |
2006年 | 34篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 5篇 |
2001年 | 14篇 |
2000年 | 4篇 |
1999年 | 17篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有707条查询结果,搜索用时 531 毫秒
631.
632.
信息社会呼唤信息公平 总被引:3,自引:1,他引:2
栾荣 《农业图书情报学刊》2008,20(12)
分析了平等与信息公平之间的关系,并且论述了当今社会中信息不公平的各种现象,以及为实现信息公平,提出了几点具体的策略. 相似文献
633.
Wenbo Long Li Luan Xing Wang Yuhua Liu Shengbin Tu Fanlun Kong Tao He 《Frontiers of Agriculture in China》2008,2(1):16-22
Cytogenetical comparison was made between high seed setting restorers TP-4 and Dminghui63 with eminent maintainer line D46B
of autotetraploid rice. The meiosis observation demonstrated that the genomes of our autotetraploid materials were all 2n = 48, which was the same as those in mitosis observation. Low percentages of univalent and trivalent in diakinesis-metaphase
I (MI) of restorers TP-4 and Dminghui63 as well as maintainer line D46B of autotetraploid rice were observed. And the percentages
of chromosome pairing were all over 99%, showing eminent cytological character. The frequency of TP-4 and Dminghui63 in diakinesis-metaphase
I was 2.00/PMC (pollen mother cell) and 2.26/PMC, respectively. However, the frequency of D46B was 6.00/PMC, significantly
higher than those of TP-4 and Dminghui63. It indicated that the maintainer D46B had better chromosome pairing capability in
diakinesis-metaphase. While, the frequency of lagging chromosomes of the maintainer D46B in anaphase I (AI) was 10.62%, significantly
lower than that of TP-4 (19.44%) or Dminghui63 (23.14%), and close to the level of diploid control (7.30%). In telophase I
(TI), maintainer D46B exhibited lower frequency of microkernel, and in telophase II (TII) the frequency of normal quartered
microspore of maintainer D46B was not only higher than that of TP-4 or Dminghui63 but also than that of diploid control. The
percentage of the cell observed chromosome lagging in AI and the percentage of abnormal cell in TI showed a greatly significant
positive correlation. That may demonstrate that chromosome separation in AI and microkernel formation in TI are controlled
by the same dominant single gene or the major gene of a QTL.
__________
Translated from Hereditas, 2007, 29(4): 462–470 [译自: 遗传] 相似文献
634.
635.
Minh Luan Nguyen Stijn Spaepen Patrick du Jardin 《Archives of Agronomy and Soil Science》2019,65(1):58-73
The capacity of plant growth-promoting rhizobacteria (PGPR) – Bacillus amyloliquefaciens GB03 (BamGB03), B. megaterium SNji (BmeSNji), and Azospirillum brasilense 65B (Abr65B) – to enhance growth and nutrient uptake in wheat was evaluated under different mineral N fertilizer rates, in sterile and non-sterile soils, and at different developmental stages. In gnotobiotic conditions, the three strains significantly increased plant biomass irrespective of the N rates. Under greenhouse conditions using non-sterile soil, growth promotion was generally highest at a moderate N rate, followed by a full N dose, while no significant effect was observed for the inoculants in the absence of N fertilizer. At 50N, plant biomass was most significantly increased in roots (up to +45% with Abr65B) at stem-elongation stage and in the ears (+19–23% according to the strains) at flowering stages. For some nutrients (N, P, Mn, and Cu), the biomass increases in roots and ears were paralleled with reduced nutrient concentrations in the same organs. Nevertheless, growth stimulation resulted in a higher total nutrient uptake and higher nutrient uptake efficiency. Furthermore, Abr65B and BmeSNji counteracted the reduction of root development caused by a high N supply. Therefore, combining PGPR with a proper cultivated system, N rate, and plant stage could enhance their biostimulant effects. 相似文献
636.
为研究不同地理种源猴樟的光合蒸腾生理特性,对6个猴樟种源1年生苗进行了主要光合参数、光合速率、蒸腾速率的对比研究,并对6个种源的光响应曲线进行拟合。结果表明:6个种源日平均净光合速率呈贵州开阳>贵州绥阳>贵州凯里>贵州花溪>云南腾冲>贵州兴仁;日平均光合速率为7.19~8.08μmol/(m2.s),变异系数为8.126%;平均蒸腾速率为2.65~3.63 mmol/(m2.s),变异系数为15.351%;光能利用率最高的是贵州绥阳种源,最低的是贵州兴仁;光补偿点呈贵州绥阳>贵州开阳>贵州凯里>云南腾冲>贵州兴仁>贵州花溪;光饱和点呈贵州凯里>贵州绥阳>云南腾冲>贵州兴仁>贵州开阳>贵州花溪;日平均蒸腾速率呈贵州凯里>云南腾冲>贵州绥阳>贵州开阳>贵州花溪>贵州兴仁;水分利用率最高的是花溪种源的猴樟,最低的是贵州兴仁;贵州花溪种源猴樟的光补偿点、光饱和点最小,其对弱光的适应性比较强,但光合作用容易受到强光的抑制,凯里种源猴樟的光补偿点低、光饱和点高,光能利用区间最大,对光的生态适应性最强。 相似文献
637.
<正>第七章克服关键组织障碍企业制定了蓝海战略后,关键是执行。由于蓝海战略的低成本差异化及独辟蹊径,就更加大了执行的难度。主要体现在以下4方面:一是认知的障碍,如何唤醒员工,让他们意识到战略变革的必要性。二是有限的资源,即如何协调战略执行与有限资源的矛盾。三是动力上的问题,如何鼓动关键 相似文献
638.
639.
Bacillus thuringiensis (Bt) transgenic cotton has been planting in large-scale for more than 10 years in China. It was observed that resistance to bollworm was reduced with the application of big-boll cultivars in China. The objective of the study was to investigate the effects of boll size on the contents of CryIA insecticidal protein in boll shell and cotton seed during the course of boll development. Two experiments were conducted at the Yangzhou University Farm, Yangzhou, China. In 2004, three cultivars including Sikang 1 (small-boll), Xiangza 3 (medium-boll) and Kemian 3 (big-boll) were compared for boll shell volume and 100-seed weight from 10 to 40 days after flowering (DAF), and insecticidal protein contents in boll shell and cotton seed from 10 to 50 DAF. As expected, the differences between cultivars were significant for all the four characteristics. Cultivars with bigger boll shell volume had higher 100-seed weight but lower insecticidal protein contents in both of the boll shell and cotton seed. The correlation between boll size and boll insecticidal protein content was negative (−0.653). The correlation between 100-seed weight and cotton seed insecticidal protein content was significantly negative (−0.645). In 2005, leaf cut (LC) and square removal (SR) treatments were applied to Sikang 1 and Sikang 3. The boll shell volume and 100-seed weight were decreased by LR, but increased by SR. LC significantly enhanced and SR significantly reduced the insecticidal protein contents of boll shell and cotton seed. The correlation between boll size and boll insecticidal protein content (−0.870) and the correlation between 100-seed weight and cotton seed insecticidal protein content were both highly significant and negative (−0.841). Therefore, the results of the study indicated that the boll insecticidal protein content was significantly affected by boll size. The implications of the observed results in breeding, cultural practices and pest management were discussed. 相似文献
640.
The purpose of this study was to investigate the morphology, transmission route of photosynthetic products in the seed stalk of Caragana arborescens Lam. at various stages after flowering and evaluate the role of the seed stalk in seed maturation using scanning electron microscopy. We found that the mature seed stalk mainly consisted of vessels,sclerenchymatous cells and parenchymatous cells. Elongated cells formed a ring at the junction between the seed stalk and seed, and a large hollow was produced by two layers of sclerenchymatous cells in the interior seed, which functions to sustain seed growth. The opening in the center of the ring was closed during an early stage of seed development, and the opening enlarged as the seed matured.There were two routes for material transport, which started from the seed stalk: one from the seed coat to the embryo,and another directly entering the embryo. Vessels, which are abundant in the seed stalk, are the pathway for absorption of nutrients by the seeds. The vessels were densely packed in the seed stalk, and secondary thickening of the cell wall of the vessels was characterized by net thread thickening, while the secondary thickening of the cell wall of the vessels within the seed was characterized by screw thread thickening. The morphological characteristics of the vessels were adaptive to its functions. 相似文献