全文获取类型
收费全文 | 540篇 |
免费 | 21篇 |
国内免费 | 63篇 |
专业分类
林业 | 8篇 |
农学 | 229篇 |
14篇 | |
综合类 | 240篇 |
农作物 | 73篇 |
水产渔业 | 2篇 |
畜牧兽医 | 19篇 |
园艺 | 33篇 |
植物保护 | 6篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 15篇 |
2018年 | 12篇 |
2017年 | 19篇 |
2016年 | 22篇 |
2015年 | 6篇 |
2014年 | 19篇 |
2013年 | 19篇 |
2012年 | 25篇 |
2011年 | 28篇 |
2010年 | 36篇 |
2009年 | 28篇 |
2008年 | 25篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 22篇 |
2004年 | 23篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 18篇 |
1994年 | 11篇 |
1993年 | 20篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 3篇 |
排序方式: 共有624条查询结果,搜索用时 125 毫秒
591.
Molecular analysis of the fourth progeny of plants derived from a cytoplasmic male sterile chicory cybrid 总被引:1,自引:0,他引:1
Cytoplasmic male sterile (CMS) chicory cybrids have previously been obtained by fusion between chicory and CMS sunflower protoplasts. Preliminary restriction fragment length polymorphism analysis has shown mitochondrial recombination events in CMS plants and their progeny. The aim of this study was to investigate the fate of the mitochondrial genome of the fourth progeny derived from one CMS cybrid. Southern hybridization using several specific mitochondrial sequences as probes have revealed polymorphic patterns between the plants analysed and, consequently, the genetic instability of this genome. Presence of the sequence responsible for cytoplasmic male sterility in sunflower (orf522) was detected by polymerase chain reaction and confirmed by molecular hybridization in the CMS chicory plants; however, its part in CMS expression in chicory did not appear obvious. Moreover, different flowering phenotypes, including completely fertile plants occurred and no correlation could be established between the different mitochondrial profiles and the flowering types. These results suggested some hypotheses and questions about the molecular determinant of CMS in chicory, its regulation and expression and questions about the mitochondrial-nuclear interactions. 相似文献
592.
593.
Summary Cabbage hybrid seeds are commercially produced by means of self-incompatibility. This system may show some instability mainly under tropical conditions, where cytoplasmic male sterility can be an alternative approach for hybrid seeds production. However, cabbage hybrids holding Ogura male-sterile cytoplasm show some irregularities during development. By assessing some characteristics during the growing cycle of male-sterile cabbage hybrids and comparing them to genomic similar male-fertile ones and to the most common cabbage hybrid cultivated in Brazil, it was observed that the male-sterile hybrids had the same vigour, uniformity, number of leaves, resistance to Xanthomonas campestris pv. campestris, and earliness as their male-fertile counterparts and performed better than the commercial check hybrid for some of these characteristics. Although male-sterile hybrids showed yellowing of leaves, some parental combinations succeeded in overcoming or strongly reducing this cytoplasmic effect.Abbreviations dat
days after transplanting
- CMS
Cytoplasmic Male Sterility
- CNPH
National Centre for Vegetable Crops Research 相似文献
594.
Lucimara Chiari Lucas Koshy Naoe Newton Deniz Piovesan Inês Chamel José Cosme Damião Cruz Maurilio Alves Moreira Everaldo Gonçalves de Barros 《Euphytica》2006,150(1-2):141-147
Summary We studied the genetic basis of isoflavone content inheritance in soybean seeds. The progenitors BARC-8 (low isoflavone content), IAC-100 (high isoflavone content), the F1 and F2 populations derived from reciprocal crosses, and backcross populations were analyzed for isoflavone content and composition. Six isoflavones were detected: daidzin (DZ), genistin (GT), glycitin (GC), malonyldaidzin (MDZ), malonylgenistin (MGT) and malonylglycitin (MGC). DZ, GT, MDZ and MGT contents were influenced by the cytoplasm and the nuclear genes of the maternal parent. For this reason, a genetic model was considered that included the cytoplasmic effect and epistasis between nuclear and cytoplasmic genes. Except for GT, the additive effect was the most important one. For GT content the cytoplasmic effect was the most important. Except for MDZ, the epistatic effects were significant for all the isoflavone forms. Our data indicate that genetic improvement for these traits should explore the additive genetic variances in superior lines or the cytoplasmic effect and the epistatic interactions between cytoplasmic and nuclear genes to obtain the largest selection gains. 相似文献
595.
596.
AFLP-based STS markers closely linked to a fertility restoration locus (Rfm1) for cytoplasmic male sterility in barley 总被引:3,自引:0,他引:3
The Rfm1 gene restores the fertility of the msm1 and msm2 male‐sterile cytoplasms in barley. Rfm1 is located on the short arm of chromosome 6H. To develop molecular markers tightly linked to Rfm1 for use in sophisticated marker‐assisted selection and map‐based cloning, an amplified fragment‐length polymorphism (AFLP) marker system with isogenic lines and a segregating BC1F1 population was used. Nine hundred primer combinations were screened and a linkage map was constructed around the Rfm1 locus by using 25 recombinant plants selected from 214 BC1F1 plants. Three AFLP markers were identified, e34m2, e46m19 and e48m17, linked to the locus. The most closely linked markers were e34m2, at 1.0 cM distally and e46m19, at 1.1 cM proximally. The two AFLP markers were converted to dominant STS markers. These markers should accelerate programmes for breeding restorer lines and will be useful for map‐based cloning. 相似文献
597.
Summary The quinoa cultivar Apelawa carries both normal and male sterile cytoplasms. Plants with male sterile cytoplasm produce flowers characterized by the complete absence of anthers and prominent exsertion of stigmas. Intraspecific crosses between male sterile quinoa plants and normal male fertile pollen donors consistently produced male sterile offspring under greenhouse conditions. Interspecific hybridization between male sterile quinoa plants and the related weed species Chenopodium berlandieri resulted in offspring with partial restoration of male fertility. The male sterile cytoplasm found in Apelawa has potential for use in the production of quinoa hybrids, although a more complete restorer system than that identified in C. berlandieri would be desirable. 相似文献
598.
Wide crosses were made to identify new cytoplasmic male sterility (CMS) systems in faba beans, based on the interaction of cytoplasm with restorer and maintainer alleles. A total of 330 F1 hybrids were produced in both reciprocal forms. Male sterile segregates were observed in one reciprocal version in the F2 generation of six crosses. Two of these crosses with female parents originating from Afghanistan and Egypt expressed stable male sterility in subsequent backcross generations. Based on the female parents of the two crosses, these two CMS systems were designated CMS 199 and CMS 297. CMS 199 was more stable than CMS 297 during backcross generations and across different environments. Maintainer and restorer lines for both CMS systems were identified. Lower expression of male sterility occurred in CMS 297 in the greenhouse during the winter generations than in isolation cages during the summer generations, which may be utilized to maintain male sterile lines by selfing. Regarding practical applications, the CMS 199 shows great promise for hybrid breeding in faba beans. 相似文献
599.
S. Prakash I. Ahuja H. C. Upreti V. Dinesh Kumar S. R. Bhat P. B. Kirti V. L. Chopra 《Plant Breeding》2001,120(6):479-482
An alloplasmic mustard, Brassica juncea, has been synthesized by placing its nucleus into the cytoplasm of the related wild species Erucastrum canariense to express cytoplasmic male sterility. To achieve this, the sexual hybrid E. canariense (2n=18, EcEc) ×Brassica campestris (2n= 20, AA) was repeatedly backcrossed to B. juncea (2n= 36, AABB). Cytoplasmic male‐sterile (CMS) plants were recovered in the BC4 generation. These plants are a normal green and the flowers have slender, non‐dehiscing anthers that contain sterile pollen. Nectaries are well developed and female fertility is > 90%. The fertility restoration gene was introgressed to CMS B. juncea from the cytoplasmic donor E. canariense through pairing between chromosomes belonging to B. juncea with those of the E. canariense genome. The restorer plants have normal flowers, with well‐developed anthers containing fertile pollen. Meiosis proceeds normally. Pollen and seed fertility averaged 90% and 82%, respectively. F1 hybrids between CMS and the restorer are fully pollen fertile and show normal seed set. Preliminary results indicate that restoration is achieved by a single dominant gene. The constitution of the organelle genomes of the CMS, restorer and fertility restored plants is identical, as revealed by Southern analysis using mitochondrial and chloroplast probes atp A and psb D, respectively. 相似文献
600.
‘Yi 4060’ is an elite restorer line of a non‐photoperiod‐sensitive D2‐type cytoplasmic male‐sterile (CMS) line of wheat. Random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) markers were employed to map one major fertility‐restoring gene (D2Rf1) in ‘Yi 4060′. The sterile and fertile DNA pools were established from individuals in BC6, based on bulked segregant analysis. One RAPD marker E09, linked to D2Rf1, was converted to a SCAR marker and designated as E09‐SCAR865. The genetic distance between E09‐SCAR865 and D2Rf1 is 9.5 cM. Two SSR markers, Xgwm11 and Xgwm18, were also linked to a D2Rf1 and co‐segregated with E09‐SCAR865. The three molecular markers are useful in marker‐assisted breeding of the elite restorer lines for D2 ‐type CMS lines in wheat. 相似文献