全文获取类型
收费全文 | 7516篇 |
免费 | 3397篇 |
国内免费 | 2篇 |
专业分类
林业 | 395篇 |
农学 | 461篇 |
基础科学 | 5篇 |
1615篇 | |
综合类 | 110篇 |
农作物 | 120篇 |
水产渔业 | 2549篇 |
畜牧兽医 | 4308篇 |
园艺 | 21篇 |
植物保护 | 1331篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 149篇 |
2020年 | 484篇 |
2019年 | 1038篇 |
2018年 | 914篇 |
2017年 | 954篇 |
2016年 | 948篇 |
2015年 | 832篇 |
2014年 | 820篇 |
2013年 | 1040篇 |
2012年 | 504篇 |
2011年 | 517篇 |
2010年 | 624篇 |
2009年 | 287篇 |
2008年 | 294篇 |
2007年 | 123篇 |
2006年 | 162篇 |
2005年 | 134篇 |
2004年 | 135篇 |
2003年 | 126篇 |
2002年 | 146篇 |
2001年 | 90篇 |
2000年 | 115篇 |
1999年 | 20篇 |
1998年 | 14篇 |
1997年 | 21篇 |
1996年 | 9篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 18篇 |
1992年 | 7篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1970年 | 13篇 |
1968年 | 9篇 |
1958年 | 6篇 |
1938年 | 10篇 |
1931年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Sheikh Muhammad Masum Mohammad Amzad Hossain Hikaru Akamine Jun‐Ichi Sakagami Takahiro Ishii Ichiro Nakamura Md. Asaduzzaman Prasanta Chitta Bhowmik 《Weed Biology and Management》2019,19(2):39-50
This study aimed to identify the potential allelopathic indigenous rice (Oryza sativa L. ssp. indica) varieties from Bangladesh using a performance study in a weed‐infested field and to assess the extent of allelopathic interference relative to resource competition in a glasshouse experiment. Six varieties – namely, “Boterswar,” “Goria,” “Biron” and “Kartiksail” as the most allelopathic, “Hashikolmi” as weakly allelopathic and “Holoi” as nonallelopathic – were raised following a nonweed control method. The infestation levels of weed species were calculated using Simpson's Diversity Index (SDI), which ranged from 0.2 to 0.56. However, a significant correlation coefficient (0.87, P < 0.001) was obtained from these field data compared with the root inhibition percentage from the laboratory bioassay, and the “Boterswar” variety was the most allelopathic. The interactions between the allelopathic variety “Boterswar,” weakly allelopathic variety “Hashikolmi” and Echinochloa oryzicola via a target (rice)‐adjacent (E. oryzicola) cogrowth culture were determined in a hydroponic arrangement. The relative competitive intensity (RCI) and the relative neighbor effect (RNE) values showed that the crop–weed interaction was facilitation for “Boterswar” and competition for “Hashikolmi” and E. oryzicola in rice/E. oryzicola cogrowth cultures. The allelopathic effects of “Boterswar” were much higher than the resource competition in rice/E. oryzicola cogrowth cultures. The converse was observed for “Hashikolmi.” Moreover, the mineral content of E. oryzicola was severely affected by “Boterswar”/E. oryzicola cogrowth cultures’ exudate solution. Therefore, the allelopathic potential of “Boterswar” variety might be useful for developing the weed‐suppressing capacity of rice, which will likely have a significant influence on paddy weed control. 相似文献
62.
63.
Hanxiang Wu Hanhong Xu Ccile Marivingt‐Mounir Jean‐Louis Bonnemain Jean‐Franois Chollet 《Pest management science》2019,75(6):1507-1516
Systemicity of agrochemicals is an advantageous property for controlling phloem sucking insects, as well as pathogens and pests not accessible to contact products. After the penetration of the cuticle, the plasma membrane constitutes the main barrier to the entry of an agrochemical into the sap flow. The current strategy for developing systemic agrochemicals is to optimize the physicochemical properties of the molecules so that they can cross the plasma membrane by simple diffusion or ion trapping mechanisms. The main problem with current systemic compounds is that they move everywhere within the plant, and this non‐controlled mobility results in the contamination of the plant parts consumed by vertebrates and pollinators. To achieve the site‐targeted distribution of agrochemicals, a carrier‐mediated propesticide strategy is proposed in this review. After conjugating a non‐systemic agrochemical with a nutrient (α‐amino acids or sugars), the resulting conjugate may be actively transported across the plasma membrane by nutrient‐specific carriers. By applying this strategy, non‐systemic active ingredients are expected to be delivered into the target organs of young plants, thus avoiding or minimizing subsequent undesirable redistribution. The development of this innovative strategy presents many challenges, but opens up a wide range of exciting possibilities. © 2018 Society of Chemical Industry 相似文献
64.
Women's Entrepreneurship in Global and Local Contexts. Edited by Cristina Díaz‐García,Candida G. Brush,Elizabeth J. Gatewood,and Friederike Welter,Northampton, MA: Edward Elgar. 2016. 293 pp. $135 (hardcover). ISBN 978‐1‐78471‐741‐4.
下载免费PDF全文
Maria Figueroa‐Armijos 《Growth and change》2017,48(3):487-489
65.
Each species is characterized by a specific set of chromosomes, which is described as the chromosome portrait or karyotype. In general, such a karyotype is the same for all individuals in the population. An exception to that rule has recently been found in the orchid Erycina pusilla, which has been reported to have two cytotypes with chromosome numbers of 2n = 10 and 2n = 12. Here, we examined the karyotypes of the two cytotypes and found differences in arm ratios and heterochromatin patterns as well as in the presence of satellite chromosomes and in the number and location of rDNA and telomeric repeat sites. These differences are extensive and would have required multiple chromosome rearrangements to generate the differences between the two karyotypes. We also found that F1 hybrids between the parents with the two different chromosome numbers resulted in sterile offspring, in accordance with our previous findings. The combination of hybrid sterility and extensively rearranged chromosomes supports the hypothesis that these two reported cytotypes are, in fact, two different species. 相似文献
66.
67.
68.
69.
70.
Autochthonous Chagas disease in the southern United States: A case report of suspected residential and military exposures 下载免费PDF全文
N. Harris L. Woc‐Colburn S. M. Gunter R. Gorchakov K. O. Murray S. Rossmann M. N. Garcia 《Zoonoses and public health》2017,64(6):491-493
Chagas disease is a parasitic infection that can result in a progressive dilated cardiomyopathy. Here, we present the epidemiologic details of a suspected locally acquired transmission case originating from the southern United States. This is the first published report of Chagas disease in a young, healthy United States veteran with repeat triatomine exposures in Arizona. Military personnel and Arizona residents should be aware of their Chagas disease transmission risks. 相似文献