全文获取类型
收费全文 | 11407篇 |
免费 | 640篇 |
国内免费 | 969篇 |
专业分类
林业 | 764篇 |
农学 | 855篇 |
基础科学 | 331篇 |
1707篇 | |
综合类 | 3489篇 |
农作物 | 1715篇 |
水产渔业 | 288篇 |
畜牧兽医 | 2248篇 |
园艺 | 1123篇 |
植物保护 | 496篇 |
出版年
2024年 | 93篇 |
2023年 | 241篇 |
2022年 | 426篇 |
2021年 | 486篇 |
2020年 | 428篇 |
2019年 | 579篇 |
2018年 | 529篇 |
2017年 | 418篇 |
2016年 | 675篇 |
2015年 | 918篇 |
2014年 | 1016篇 |
2013年 | 1013篇 |
2012年 | 992篇 |
2011年 | 708篇 |
2010年 | 570篇 |
2009年 | 573篇 |
2008年 | 467篇 |
2007年 | 496篇 |
2006年 | 561篇 |
2005年 | 426篇 |
2004年 | 215篇 |
2003年 | 156篇 |
2002年 | 130篇 |
2001年 | 114篇 |
2000年 | 140篇 |
1999年 | 77篇 |
1998年 | 85篇 |
1997年 | 48篇 |
1996年 | 44篇 |
1995年 | 74篇 |
1994年 | 43篇 |
1993年 | 34篇 |
1992年 | 28篇 |
1991年 | 22篇 |
1990年 | 32篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 18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 27 毫秒
991.
992.
Akito Kaga Takehiko Shimizu Satoshi Watanabe Yasutaka Tsubokura Yuichi Katayose Kyuya Harada Duncan A. Vaughan Norihiko Tomooka 《Breeding Science》2012,61(5):566-592
Genetic variation and population structure among 1603 soybean accessions, consisted of 832 Japanese landraces, 109 old and 57 recent Japanese varieties, 341 landrace from 16 Asian countries and 264 wild soybean accessions, were characterized using 191 SNP markers. Although gene diversity of Japanese soybean germplasm was slight lower than that of exotic soybean germplasm, population differentiation and clustering analyses indicated clear genetic differentiation among Japanese cultivated soybeans, exotic cultivated soybeans and wild soybeans. Nine hundred ninety eight Japanese accessions were separated to a certain extent into groups corresponding to their agro-morphologic characteristics such as photosensitivity and seed characteristics rather than their geographical origin. Based on the assessment of the SNP markers and several agro-morphologic traits, accessions that retain gene diversity of the whole collection were selected to develop several soybean sets of different sizes using an heuristic approach; a minimum of 12 accessions can represent the observed gene diversity; a mini-core collection of 96 accession can represent a major proportion of both geographic origin and agro-morphologic trait variation. These selected sets of germplasm will provide an effective platform for enhancing soybean diversity studies and assist in finding novel traits for crop improvement. 相似文献
993.
Tetsuya Yamada Makita Hajika Naohiro Yamada Kaori Hirata Akinori Okabe Nobuhiko Oki Koji Takahashi Kousuke Seki Katsunori Okano Yoichi Fujita Akito Kaga Takehiko Shimizu Takashi Sayama Masao Ishimoto 《Breeding Science》2012,61(5):653-660
‘Enrei’ is the second leading variety of soybean (Glycine max (L.) Merr.) in Japan. Its cultivation area is mainly restricted to the Hokuriku region. In order to expand the adaptability of ‘Enrei’, we developed two near-isogenic lines (NILs) of ‘Enrei’ for the dominant alleles controlling late flowering at the maturity loci, E2 and E3, by backcrossing with marker-assisted selection. The resultant NILs and the original variety were evaluated for flowering, maturity, seed productivity and other agronomic traits in five different locations. Expectedly, NILs with E2 or E3 alleles flowered later than the original variety in most locations. These NILs produced comparatively larger plants in all locations. Seed yields were improved by E2 and E3 in the southern location or in late-sowing conditions, whereas the NIL for E2 exhibited almost the same or lower productivity in the northern locations due to higher degrees of lodging. Seed quality-related traits, such as 100-seed weight and protein content, were not significantly different between the original variety and its NILs. These results suggest that the modification of genotypes at maturity loci provides new varieties that are adaptive to environments of different latitudes while retaining almost the same seed quality as that of the original. 相似文献
994.
研究阳际峰自然保护区不同海拔梯度土壤剖面状况及其微生物学性状,探讨土壤微生物量C与N、酶活性、微生物商与呼吸速率的变化及其相互关系。结果发现,不同海拔梯度土壤在微生物学性状上均有较大差异。总的趋势是植被覆盖度高,地形平缓,土层厚,微生物活性强,且与海拔梯度呈显著正相关。在剖面分布上,也有明显的层次差异,即随土层的增加而减少。 相似文献
995.
996.
Arzu Funda Bagcigil Suvi Taponen Joanna Koort Bj?rn Bengtsson Anna-Liisa Myllyniemi Satu Py?r?l? 《Acta veterinaria Scandinavica》2012,54(1):69
Background
The blaZ gene encoding penicillin resistance can be located either chromosomally or on plasmids. The aim of this study was to investigate the genetic relationships and to determine the location of the blaZ gene in S. aureus isolated in bovine mastitis in Finland and Sweden.Methods
Seventy-eight β-lactamase positive S. aureus isolates from bovine mastitis (34 from Finland and 44 from Sweden) were included in the study. The localization of blaZ gene was determined by Southern blotting. The blaZ genes of the isolates were sequenced and the sequences were translated to beta-lactamase proteins and further grouped as different protein signatures. The isolates and, as control, 33 Swedish and 36 Finnish beta-lactamase negative isolates were typed with pulsed-field gel electrophoresis (PFGE).Results
In 26 out of 34 Finnish isolates (76.5%) and in 25 out of 44 Swedish isolates (56.8%) the blaZ gene was localized on a plasmid. Six different protein signatures were found. One signature was found only in four Swedish isolates, but all other signatures were found both in Finnish and Swedish isolates. The PFGE results revealed a diversity of S. aureus clones. The protein signatures were not clearly associated with certain pulsotypes.Conclusions
The plasmid location of the blaZ gene was not statistically significantly more common in Finland than in Sweden, and hence does not explain the higher proportion of penicillin-resistant isolates of S. aureus causing bovine mastitis in Finland compared to Sweden. 相似文献997.
Alessandra MMG de Castro Taís F Cruz Vanessa R Salgado Tatiana M Kanashiro Karen L Ferrari Jo?o P Araujo Jr Paulo E Brand?o Leonardo J Richtzenhain 《Acta veterinaria Scandinavica》2012,54(1):29
Background
Porcine circovirus type 2 (PCV2) has been associated with several disease complexes, including reproductive failure. The aim of this study was to identify the subtypes of PCV2 that are associated with reproductive failure in pigs from the State of São Paulo, Brazil and to investigate co-infections with other infectious organisms.Findings
Samples of 168 aborted foetuses or mummified foetuses from five farrow-to-finish swine farms known to be infected with PCV2 and located in the State of São Paulo were tested for PCV2 by polymerase chain reaction (PCR). Positive samples were additionally tested for porcine parvovirus (PPV), Leptospira spp. and Brucella spp. by PCR. PCV2 was detected in 18 of the samples (10.7%). PPV, Brucella spp. and Leptospira spp were found in 2, 10 and 0 cases, respectively. Eleven PCV2 strains were sequenced and determined to be either genotype 2a (n = 1) or 2b (n = 10).Conclusions
The findings indicate that the frequency of PCV2 infections in aborted porcine foetuses from the State of São Paulo is rather low (10.7%) and that co-infection with other pathogens is common and may be involved in PCV2 associated reproductive failure. No repeatable, characteristic amino acid motifs for regions of the PCV2 capsid protein seemed to be associated with abortion in sows. 相似文献998.
999.
YU Hong SHI Ming-jun XIAO Ying LIU Rui-xia WANG Yuan-yuan GUO Bing ZHANG Guo-zhong 《园艺学报》2012,28(12):2222-2226
AIM: To examine the effects of high glucose (HG) on the expression of Snail1 and protein kinase B (Akt)/glycogen synthase kinase 3β (GSK-3β) in primary renal tubular epithelial cells (RTECs). METHODS: The primary RTECs were randomly treated with normal glucose, high glucose or D-mannitol for 30 min~72 h. RT-PCR and Western blotting were used to observe the expression of Snail1, Akt and GSK-3β at mRNA and protein levels in these cells. The primary cultured RTECs were pretreated with LY294002 (a PI3K inhibitor, 25 μmol/L) to observe the specific inhibitory effects of phosphatidylinositol 3-kinase (PI3K) on HG-induced expression of Snail1 protein. RESULTS: Treatment of RTECs with HG resulted in increased mRNA and protein levels of Snail1, Akt1, and phosphorylation of Akt and GSK-3β. LY294002 blocked the HG-induced up-regulation of p-Akt, p-GSK-3β and Snail1 expression at protein level, but no effect of LY294002 was seen on the total protein expression of Akt1 and GSK-3β. HG did not affect the expression of GSK-3β at mRNA and protein levels. CONCLUSION: HG-induced up-regulation of Snail1 may be regulated by Akt/GSK-3β pathway in RTECs. 相似文献
1000.