全文获取类型
收费全文 | 1194篇 |
免费 | 59篇 |
国内免费 | 2篇 |
专业分类
林业 | 135篇 |
农学 | 88篇 |
基础科学 | 15篇 |
294篇 | |
综合类 | 85篇 |
农作物 | 105篇 |
水产渔业 | 91篇 |
畜牧兽医 | 308篇 |
园艺 | 18篇 |
植物保护 | 116篇 |
出版年
2023年 | 8篇 |
2022年 | 32篇 |
2021年 | 34篇 |
2020年 | 36篇 |
2019年 | 34篇 |
2018年 | 46篇 |
2017年 | 53篇 |
2016年 | 42篇 |
2015年 | 29篇 |
2014年 | 47篇 |
2013年 | 113篇 |
2012年 | 69篇 |
2011年 | 77篇 |
2010年 | 62篇 |
2009年 | 52篇 |
2008年 | 56篇 |
2007年 | 24篇 |
2006年 | 40篇 |
2005年 | 24篇 |
2004年 | 24篇 |
2003年 | 33篇 |
2002年 | 32篇 |
2001年 | 35篇 |
2000年 | 23篇 |
1999年 | 21篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 4篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1973年 | 9篇 |
1972年 | 4篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 7篇 |
排序方式: 共有1255条查询结果,搜索用时 0 毫秒
91.
92.
Summary Two pairs of genes indicated by H
P
1 and H
A
2 appear to play a part in the genetic control of pubescence of leaves in the crosses of Pak51 x Empire Red leaf, L11 x Empire Red leaf, AC134 x Empire Red leaf, AC134 x Acala 1517D and L11 x Acala 1517 D. H
P
1 seems to induce hair of sufficient length and density and is completely dominant to h
p
1.H
A
2 allele, seems to induce hairiness but to a smaller degree. It acts additivily to H
P
1 giving profusely hairy plants.
H
P
1 gene is present in the local varieties Pak51, L11 and AC134 producing hair of such length and density as to confer jassid resistance in them. Compared with these, the exotic types viz., Empire Red leaf and Acala 1517D possess H
A
2 giving sparsely hairy plants.The exotic variety Deltapine Smooth leaf possesses another gene, E
A, which displays an epistatic effect on H
A
2 gene. The gene E
A has only a minor effect on the H
P
1.Apart from this, the presence of certain intensifying or modifying genes seem to affect the density and length of hair resulting in deviations even in individual groups.M. Sc. Student, Professor and Head, and Reader, respectively of the Dept. of Plant Breeding and Genetics. 相似文献
93.
Theoretical fundamentals and experimental methods to study the strength of water-stable bonds in soil aggregates are discussed. The strength of water-stable aggregates characterized by cohesion is proved to be one of the important structural and mechanical properties of soil. The regular variation of this parameter inthe soils under study is related to the content of humus and physical clay. 相似文献
94.
Fluconazole resistance is becoming an important clinical concern. We studied the in vitro effects of cinnamaldehyde against 18 fluconazole-resistant Candida isolates. MIC90 of cinnamaldehyde against different Candida isolates ranged 100–500 μg/ml. Growth and sensitivity of the organisms were significantly affected by cinnamaldehyde at different concentrations. The rapid irreversible action of this compound on fungal cells suggested membrane-located targets for its action. Insight studies to mechanism suggested that cinnamaldehyde exerts its antifungal activity by targeting sterol biosynthesis and plasma membrane ATPase activity. Inhibition of H+-ATPase leads to intracellular acidification and cell death. Toxicity against H9c2 rat cardiac myoblasts was studied to exclude the possibility of further associated cytotoxicity. The observed selectively fungicidal characteristics against fluconazole-resistant Candida isolates signify a promising candidature of this essential oil as an antifungal agent in treatments for candidosis. 相似文献
95.
Md. Habibur Rahman Md. Abu Sayed Arfin Khan Bishwajit Roy Most. Jannatul Fardusi 《林业研究》2011,22(4):551-559
A study was conducted at two-biodiversity conservation areas of Northeastern Bangladesh (a part of Sylhet Forest Division)
to assess the species composition, diversity and density of natural regeneration of tree species both indigenous and exotic
species. Data were collected by stratified random quadrate method during January 2010 to July 2010. Totally 200 circular plots
of 2 m×2 m in size had 5 different habitat types of plants namely; forest, roadside, homestead (surrounding forest dwellers
house), fallow land and others (canals, streams and tea gardens side), which included a total of 55 regenerating species belonging
to 28 families. Meliaceae is the dominant family and shows the highest family importance value (26.3), having six species,
followed by Moraceae (24.24). Among the five habitat types, forest (43 species) possess the highest number of species, followed
by roadside (23 species). Total 15 exotic species among 9 families and 40 indigenous species with 24 families were recorded.
For exotic species, Tectona grandis possess the highest relative density (11.7%) and relative frequency (10.5%); Senna siamea had highest relative abundance (7.83%). In case of indigenous species, Chickrassia tabularis possess the highest relative density (4.23%) and relative frequency (4%); Dipterocarpus turbinatus had the highest relative abundance (3.92%). Tectona grandis (29.66) and Chickrassia tabularis (10.8) had the highest IVI for exotic and indigenous species respectively. Different diversity indices such as Shanon-Winner
diversity index, species diversity index, species richness index, species evenness index, Simpson index and species dominance
index, etc. were applied to quantify definite diversity. The regeneration of species associated with low levels of disturbance
was in the exotic species. Study suggests that proper protection from human disturbances and scientific management of natural
regeneration of two-study forests may lead a rich biodiversity site in the country. 相似文献
96.
M. Shahadat Hossain Khan Tadao Wagatsuma Afrin Akhter Idupulapati M. Rao 《Journal of plant nutrition》2015,38(13):1973-1983
Nutrient deficiencies are often an additional growth-limiting factor in tropical acid soils. Considering the potential interactions between Al stress and low-nutrient stress, differences among rice cultivars for Al tolerance, low-nutrient tolerance, and combined stress tolerance were investigated. The main objective of this study was to identify the predominant growth-limiting factor in tropical acid soils. Tolerance to low nutrient stress and combined stress did not show any relationship with aluminum (Al) tolerance indicating that these stress factors act independently. Al-tolerant cv. Rikuu-132 was tolerant to combined stress. Conversely, highly Al-sensitive cv. BR34 was most tolerant to combined and low nutrient stress. Combined stress tolerance of shoot was positively correlated with calcium (Ca) content of shoot. The results indicate that Al tolerance alone is not adequate for superior performance on most acid soils. Tolerance to combined stress factors would be needed to improve productivity of rice on low fertility acid soils. 相似文献
97.
98.
99.
Cytokinins: permissive role in seed germination 总被引:14,自引:0,他引:14
A A Khan 《Science (New York, N.Y.)》1971,171(974):853-859
100.
Antiarthritic gold compounds effectively quench electronically excited singlet oxygen 总被引:5,自引:0,他引:5
Although certain gold [Au(I)] compounds have been used effectively in the treatment of rheumatoid arthritis for some years, the molecular basis for such therapeutic action has been unclear. One possible mechanism of the action of Au(I) compounds is that they protect unsaturated membrane lipids and proteins against oxidative degradation caused by activated phagocytes that are not properly regulated. In this study it has been shown that superoxide ion (O-2.), a product of activated phagocytes, can be oxidized to electronically excited singlet oxygen (O1(2)delta g), an agent that is capable of peroxidation of unsaturated fatty acid derivatives. It has also been shown that antiarthritic Au(I) compounds are effective deactivators of O1(2)delta g with quenching constants on the order of 10(7) M-1 sec-1. 相似文献