全文获取类型
收费全文 | 18087篇 |
免费 | 972篇 |
国内免费 | 1062篇 |
专业分类
林业 | 1649篇 |
农学 | 1390篇 |
基础科学 | 1447篇 |
1585篇 | |
综合类 | 6745篇 |
农作物 | 1922篇 |
水产渔业 | 783篇 |
畜牧兽医 | 2810篇 |
园艺 | 1264篇 |
植物保护 | 526篇 |
出版年
2024年 | 135篇 |
2023年 | 338篇 |
2022年 | 597篇 |
2021年 | 703篇 |
2020年 | 679篇 |
2019年 | 848篇 |
2018年 | 643篇 |
2017年 | 602篇 |
2016年 | 905篇 |
2015年 | 1173篇 |
2014年 | 1464篇 |
2013年 | 1394篇 |
2012年 | 1472篇 |
2011年 | 1272篇 |
2010年 | 919篇 |
2009年 | 841篇 |
2008年 | 790篇 |
2007年 | 1040篇 |
2006年 | 944篇 |
2005年 | 702篇 |
2004年 | 536篇 |
2003年 | 361篇 |
2002年 | 233篇 |
2001年 | 241篇 |
2000年 | 256篇 |
1999年 | 142篇 |
1998年 | 149篇 |
1997年 | 114篇 |
1996年 | 81篇 |
1995年 | 82篇 |
1994年 | 74篇 |
1993年 | 58篇 |
1992年 | 51篇 |
1991年 | 42篇 |
1990年 | 41篇 |
1989年 | 32篇 |
1988年 | 27篇 |
1987年 | 20篇 |
1986年 | 11篇 |
1985年 | 29篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 19篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
971.
Kyoko Takagi Akito Kaga Masao Ishimoto Makita Hajika Toshiro Matsunaga 《Breeding Science》2015,65(5):372-380
Radiocesium is an extremely harmful radionuclide because of its long half-life; it is important to reduce its transfer from contaminated soil into crops. Here we surveyed genetic variation for seed cesium (Cs) concentration in soybean mini-core collections representing large genetic diversity. The collections grown over 3 years in rotational paddy fields exhibited varying seed Cs concentrations with significant year-to-year correlations, although the phenotypic stability of Cs concentration was lower than that of the congeners potassium (K) and rubidium (Rb). Although Cs is supposedly accumulated in plants via the K transport system, there was no apparent relationship between Cs and K concentrations, whereas a clear positive correlation was observed between Cs and Rb concentrations. Cs and K concentrations in seed showed slightly positive and negative correlations, respectively, with days to flowering. We selected several high or low Cs accumulator candidates on the basis of the 3 years of seed concentration data. These two groups showed significantly different seed Cs concentrations in another field. The differences could not be explained by flowering time alone. These results suggest that genetic variation for seed Cs concentration is present in soybean germplasm and would be useful for breeding low Cs-accumulating varieties. 相似文献
972.
Genetically modified, herbicide-tolerant (GMHT) Brassica napus plants originating from seed spill have recently been found along roadsides leading from Japanese ports that unload oilseed rape. Such introductions have potential biodiversity effects (as defined by the Cartagena Protocol): these include replacement of native elements in the biota through competitive suppression or hybridization. We conducted surveys in the period 2006–2011 to assess such threats. We examined shifts in the population distribution and occurrence of GMHT plants in 1,029 volunteer introduced assemblages of B. napus, 1,169 of B. juncea, and 184 of B. rapa around 12 ports. GMHT B. napus was found around 10 of 12 ports, but its proportion in the populations varied greatly by year and location. Over the survey period, the distributions of a pure non-GMHT population around Tobata and a pure GMHT population around Hakata increased significantly. However, there was no common trend of population expansion or contraction around the 12 ports. Furthermore, we found no herbicide tolerant B. juncea and B. rapa plants derived from crosses with GMHT B. napus. Therefore, GMHT B. napus is not invading native vegetation surrounding its populations and not likely to cross with congeners in Japanese environment. 相似文献
973.
Makiko Chono Hitoshi Matsunaka Masako Seki Masaya Fujita Chikako Kiribuchi-Otobe Shunsuke Oda Hisayo Kojima Shingo Nakamura 《Breeding Science》2015,65(1):103-109
In the wheat (Triticum aestivum L.) cultivar ‘Zenkoujikomugi’, a single nucleotide polymorphism (SNP) in the promoter of MOTHER OF FT AND TFL1 on chromosome 3A (MFT-3A) causes an increase in the level of gene expression, resulting in strong grain dormancy. We used a DNA marker to detect the ‘Zenkoujikomugi’-type (Zen-type) SNP and examined the genotype of MFT-3A in Japanese wheat varieties, and we found that 169 of 324 varieties carry the Zen-type SNP. In Japanese commercial varieties, the frequency of the Zen-type SNP was remarkably high in the southern part of Japan, but low in the northern part. To examine the relationship between MFT-3A genotype and grain dormancy, we performed a germination assay in three wheat-growing seasons. On average, the varieties carrying the Zen-type SNP showed stronger grain dormancy than the varieties carrying the non-Zen-type SNP. Among commercial cultivars, ‘Iwainodaichi’ (Kyushu), ‘Junreikomugi’ (Kinki-Chugoku-Shikoku), ‘Kinuhime’ (Kanto-Tokai), ‘Nebarigoshi’ (Tohoku-Hokuriku), and ‘Kitamoe’ (Hokkaido) showed the strongest grain dormancy in each geographical group, and all these varieties, except for ‘Kitamoe’, were found to carry the Zen-type SNP. In recent years, the number of varieties carrying the Zen-type SNP has increased in the Tohoku-Hokuriku region, but not in the Hokkaido region. 相似文献
974.
QIU Long-guang 《保鲜与加工》2006,(1):154-158
This article summarizes the theory achievements,arguments,the investment and ownership concentration model which studied in investment-cash flow and the stockholder's rights structure questions.The financing restraint is explained.The special social stratum shareholder is elaborated which influences relation between investment and internal cash flow by the financing restraint existing in the enterprise,the management opportunism hypothesis and the information assymetrical theory separately.Finally the authors induce and study the real diagnosis model of the supposition(above).The model is important for the empirical study of ownership structure influencing to corporate investment. 相似文献
975.
976.
Chao Li Cheng Liu Xiaoying Ma Aidong Wang Ruijun Duan Christiane Nawrath Takao Komatsuda Guoxiong Chen 《Breeding Science》2015,65(4):327-332
The cuticle covers the aerial parts of land plants, where it serves many important functions, including water retention. Here, a recessive cuticle mutant, eceriferum-ym (cer-ym), of Hordeum vulgare L. (barley) showed abnormally glossy spikes, sheaths, and leaves. The cer-ym mutant plant detached from its root system was hypersensitive to desiccation treatment compared with wild type plants, and detached leaves of mutant lost 41.8% of their initial weight after 1 h of dehydration under laboratory conditions, while that of the wild type plants lost only 7.1%. Stomata function was not affected by the mutation, but the mutant leaves showed increased cuticular permeability to water, suggesting a defective leaf cuticle, which was confirmed by toluidine blue staining. The mutant leaves showed a substantial reduction in the amounts of the major cutin monomers and a slight increase in the main wax component, suggesting that the enhanced cuticle permeability was a consequence of cutin deficiency. cer-ym was mapped within a 0.8 cM interval between EST marker and AK370363, a pericentromeric region on chromosome 4H. The results indicate that the desiccation sensitivity of cer-ym is caused by a defect in leaf cutin, and that cer-ym is located in a chromosome 4H pericentromeric region. AK251484相似文献
977.
Summary The effect of genotype, growing conditions for donor plants and type and concentration of carbohydrate in the culture medium was investigated for anther culture of head cabbage (white cabbage, savoy cabbage, pointed-headed cabbage). Strong genotypic effects on embryo formation from the cultured anthers were shown as well as superior embryo formation from anthers of field grown donor plants compared to plants grown in the greenhouse. When comparing 7, 10 and 13% sucrose in the medium, embryo response increased with increasing sucrose concentration. With maltose, which was generally inferior to sucrose as carbohydrate source for anther culture, the embryo response did not increase with maltose concentration above 10 per cent. 相似文献
978.
Forty-seven genotypes of the cultivated peanut, Arachis hypogaea L., were screened for regenerative responses of immature leaflet cultures on two media varying in the auxin: cytokinin ratio. Statistical analysis revealed significant media and genotype differences for rhizogenesis plus media differences for callus proliferation but no differences for shoot formation. When genotypes were categorized according to botanical types, differences between subspecies were observed for rhizogenesis. Cultivars of the Virginia botanical type (subspecies hypogaea) were significantly different from either the Valencia or Spanish botanical types (both subspecies fastigiata). Overall, rhizogenesis varied from 0 to 70% among all genotypes. Shoot production was low (30%) while callus proliferation was extremely high (70%). 相似文献
979.
Summary Soybean DNA fingerprints were analyzed by digoxigenin-labeled oligonucleotide probes complementary to simple repetitive sequences. The clearest and most polymorphic patterns were obtained with (AAT)6 as a probe, with which all 47 soybean cultivars tested could be distinguished. However, DNA fingerprints of individuals within cultivars showed the same pattern. Using (CT)8, (GAA)5 or (AAGG)4 as probes, clear polymorphic patterns among cultivars and accessions in the subgenus Soja (Glycine max and Glycine soja) were not observed, while quite different patterns were found in accessions in the subgenus Glycine. The results suggest that G. max and G. soja are closer in their genome structure. DNA fingerprints of reciprocal crosses between cultivars and accessions in the subgenus Soja were similar, and contained bands of both parents. In an F2 population from these crosses, such bands segregated in a Mendelian fashion. 相似文献
980.
Summary The inheritance of flowering time (FT) in a cross between early-flowering (P1) and late-flowering (P2) Matthiola incana genotypes, was investigated. The distribution of FT in F1, F2 and BC1 generations indicated an additive genetic control with partial dominance of earlines alleles, particularly with regard to double-flowered plants. Single-flowered plants flowered earlier than double-flowered plants, averaged within both parental lines; however, the mean difference between singles and doubles was 16 days for P1 as compared with 6 days for P2. This flower-doubleness related delay in FT was found to be heritable, by analysis of F3 family means. The implications of these results on the breeding of stock cultivars is discussed.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1138-E, 1993 series. 相似文献