全文获取类型
收费全文 | 16667篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
林业 | 3633篇 |
农学 | 1301篇 |
基础科学 | 138篇 |
2796篇 | |
综合类 | 730篇 |
农作物 | 2136篇 |
水产渔业 | 1819篇 |
畜牧兽医 | 1112篇 |
园艺 | 1117篇 |
植物保护 | 1906篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 2761篇 |
2017年 | 2726篇 |
2016年 | 1188篇 |
2015年 | 72篇 |
2014年 | 30篇 |
2013年 | 42篇 |
2012年 | 805篇 |
2011年 | 2141篇 |
2010年 | 2113篇 |
2009年 | 1263篇 |
2008年 | 1323篇 |
2007年 | 1581篇 |
2006年 | 32篇 |
2005年 | 102篇 |
2004年 | 105篇 |
2003年 | 153篇 |
2002年 | 63篇 |
2001年 | 9篇 |
2000年 | 44篇 |
1999年 | 7篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1990年 | 1篇 |
1989年 | 7篇 |
1988年 | 17篇 |
1987年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1979年 | 1篇 |
1977年 | 4篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Symbiotic gene mutated in the pea (Pisum sativum L.) line RisfixC is a determinant of the number of symbiotic root nodules. In parallel to a sharp increase in nodule number, its mutational inactivation brings about the insensitivity of nodulation to the ambient nitrate level (Nts trait). Using the established localization to the SYM2-NOD3 region of the pea linkage group I, functional PCR markers were developed for the orthologous region on the chromosome 5 of the model species Medicago truncatula. Owing to the conservation of the binding regions of the designed primers, pea orthologues were successfully amplified with 60% of the primer pairs tested. When applied to a mapping pea population from the cross of the line RisfixC x Afghanistan L1268 (sym2), the new markers allowed to localize the supernodulation mutation within 2.5 cM confidence interval in the pea genome. The placement of the functional markers on the M. truncatula chromosome 5 confined the orthologous gene location to eight overlapping BACs spanning approximately 710 kbp (positions 37,755,678–38,467,472). The narrowed list of the annotated Medicago genes in combination with the published data on their symbiotic and nitrate regulation can be used for the candidate gene identification, together with the requirements imposed by the known function in nodule number initiation and nitrate sensing. In addition, the new markers are applicable for tracking the RisfixC allele in breeding programmes aimed at the improvement of symbiotic performance. 相似文献
992.
Zhi-Wei Wang Lei Gao Hai Zhou Liu Shi Yong Mei Yuan Zhou Chang Ping Xiang Ting Wang 《Euphytica》2012,186(2):313-320
A male sterile plant appeared in the radish breeding program at the Hubei Academy of Agricultural Sciences, Hubei, China.
In its progeny, a two-type (half of plants male sterile, the other half male fertile) line 01GAB was established. An F2 population of 260 plants from a cross of male-sterile 01GAB and a male fertile line 9802H segregated for male fertility in
a 3:1 ratio indicating that fertility was restored by a single dominant gene, here designated RsMs. A PCR-based DNA marker specific to the male fertility Rfob gene in 9802H was absent in 01GAB. Linkage analysis placed the RsMs locus 10.7 cM away from the Rfo locus. In an F2 population of hybrids between 01GAB and male fertile 9802B, a co-dominant DNA marker for the RSultr3.2A (a radish sulfate transporter gene) locus was linked to the RsMs locus at 1.5 cM suggesting that fertility restoration in 01GAB was located in the region with known male sterility restorers
in radish. However, no maintainer for the 01GAB source of male sterility has been identified so far. Cytological observations
have shown that the abnormalities in male sterile anthers first appeared in tapetum at the tetrad stage, followed by a hypertrophy
of the tapetal cells at the vacuolate microspore period. These results suggest that male sterility in 01GAB is likely to be
genetic in nature, or it may represent a new type of the cytoplasmic male sterility. 相似文献
993.
Use of cross incompatibility in corn (Zea mays L.) by the Ga1-s allele may reduce cross-fertilization in specialty and conventional organic corn with pollen from genetically-modified (GM)
corn. For effective use, information about environment, and genotype × environment effects on cross-fertilization by ga1 as well as heritability of cross incompatibility in maize is necessary. Our objective was to obtain this information. Four
population pairs differing in their genotype at ga1 were evaluated for cross incompatibility with ga1 pollen in different environments. Populations were derived by crossing the recurrent parents B116, PHG35, ARZM16035:S19,
and (CHZM05015:Mo17)Mo17 to Ga1-s donor parent Mo508W/Mo506W. Two replicates of each treatment were grown in the center of 952 m2 fields planted with purple corn as an adventitious source of ga1/ga1 pollen. Open pollination was allowed and the amount of cross-fertilization estimated by averaging the percentage of purple
seeds. Environment and genotype × environment effects were not significant. Contrasts to evaluate differences in cross-fertilization
between Ga1-s and ga1 populations revealed that mean percentages of cross-fertilization in Ga1-s populations of B116, ARZM16035:S19, and (CHZM05015:Mo17)Mo17 were significantly lower than in ga1 populations. The estimated broad-sense heritability on an entry-mean basis for cross incompatibility was 0.81. Results suggest
differences in genotype at ga1 played a major role in cross-fertilization of populations differing in their genotype at the ga1 locus. Incompatibility may be selected effectively over different environments and the Ga1-s system may be of value to reduce cross-fertilization with GM corn pollen. 相似文献
994.
The selection of cross-compatible cultivars is essential to ensure fruit set in self-incompatible species like Japanese plum and thus the S-genotype must be determined in order to establish incompatibility groups. In this study an improved Japanese plum S-genotyping method, based in polymerase chain reaction and capillary electrophoresis detection of intron polymorphisms of S-locus genes, S-RNase and SFB, has been assayed and validated in a wide sample of cultivars. This method allows a more precise determination of amplified fragment sizes and therefore a better differentiation of self-incompatibility alleles. The assayed methodology was proven effective in the detection of 13 different S-alleles of S-RNases and SFBs and was used to S-genotype 105 Japanese plum cultivars, 32 of which are described by first time in this work. Analysed cultivars were assigned into 11 incompatibility groups and two new incompatibility groups (XX and XXI) were identified, increasing to 21 the number of incompatibility groups described in this crop. 相似文献
995.
Solidity of microsatellite markers is a key issue for varietal identification, especially when they are used for legal purposes, what includes their probable future use in the distinctness, uniformity and stability testing of new varieties needed for the granting of Plant Breeders’ Rights. Nine grapevine microsatellites (VVS2, VVMD5, VVMD27, VVMD28, ssrVrZAG29, ssrVrZAG62, ssrVrZAG67, ssrVrZAG83 and ssrVrZAG112), which had previously demonstrated its capacity to discriminate any grapevine variety, have been assessed to evaluate its uniformity and stability. 19 varieties were selected, representative of a high diversity for morphological, agronomical, cultural and historical aspects, as well as for microsatellite allele variability. Then, for each variety, uniformity and stability were evaluated through the analysis of 50 plants from each of three different plots, and five plants from each of seven additional plots. Material from 4,137 plants of 229 plots of the 19 varieties was sampled in seven countries. Of 3,654 plants analyzed with the set of nine microsatellites, 3,299 were of the right variety and used for the survey. An average of 172 individual values was studied for each allele of each microsatellite of each variety, and none differences were detected that could not be explained as technical variations, with the exception of several putative chimeras in two varieties. Of the total of 171 variety x microsatellite combinations, only in one combination (‘Merlot’ x VVMD27) the number of off-types exceeded the threshold allowed. The remaining 170 combinations have been found uniform and stable according to internationally accepted rules. 相似文献
996.
Shahid Hussain Muhammad Aamer Maqsood Zed Rengel Muhammad Khawar Khan 《Euphytica》2012,186(1):153-163
Estimating variation in grain mineral concentration and bioavailability in relation to grain yield and the year of cultivar
release is important for breeding wheat with increased content of bioavailable minerals. The grain yield and yield components,
grain phytate concentration, and concentration and bioavailability of minerals (zinc Zn, iron Fe and calcium Ca) in wheat
grains were estimated in 40 wheat cultivars released in Punjab (Pakistan) during the last five decades. Mean grain Zn and
Ca concentrations in current-cultivars were significantly lower (≥14%) than in obsolete cultivars released during the Green
Revolution (1965–1976). Much of this variation was related to increased grain weight in current-cultivars. There was a positive
correlation among minerals (r = 0.39 or higher, n = 40) and minerals with phytate in wheat grains (r = 0.38 or higher, n = 40). The tested cultivars varied widely in grain yield and grain phytate-to-mineral molar ratios (phytate:mineral). Compared
to obsolete cultivars, the current-cultivars had a higher phytate:mineral ratio in grains, indicating poor bioavailability
of minerals to humans. The study revealed a non-significant relationship between grain yield and phytate:mineral ratios in
grains. Therefore, breeding for lower phytate:mineral ratios in wheat grains can ensure increased mineral bioavailability
without significant reduction in the yield potential. Future breeding should be focused on developing new genotypes suitable
for mineral biofortification and with increased mineral bioavailability in grains. 相似文献
997.
Genetic expression of a trait is complicated and it is usually associated with many genes including their interactions (epistasis) and genotype-by-environment interactions. Genetic mapping currently focuses primarily on additive models or marginal genetic effects due to the complexity of epistatic effects. Thus, there exists a need to appropriately identify favorable epistatic effects for important biological traits. Several multifactor dimensionality reduction (MDR) based methods are important resources to identify high-order gene–gene interactions. These methods are mainly focused on human genetic studies. Many traits in plant systems are not only quantitatively inherited but also are often measured in repeated field plots under multiple environments. In this study, we proposed a mixed model based MDR approach, which is suitable for inclusion of various fixed and random effects. This approach was used to analyze a cotton data set that included eight agronomic and fiber traits and 20 DNA markers. The results revealed high order epistatic effects were detected for most of these traits using this modified MDR approach. 相似文献
998.
V. S. A. K. Sama K. Himabindu S. Bhaskar Naik R. M. Sundaram B. C. Viraktamath J. S. Bentur 《Euphytica》2012,187(3):393-400
Host plant resistance is the preferred management strategy for Asian rice gall midge (Orseolia oryzae), a serious pest in many rice-growing countries. Identification of simple sequence repeat (SSR) markers that are tightly linked to pest resistance genes can accelerate development of gene pyramids for durable/multiple resistance. Based on conventional and molecular allelism tests, we report herein that rice genotype Aganni possesses Gm8 gene, conferring hypersensitive independent (HR– type) resistance to gall midge biotypes GMB1, GMB2, GMB3, GMB4, and GMB4M. The gene Gm8 was mapped to chromosome 8 within a 400-kbp region, and the SSR markers RM22685 and RM22709 flank the gene closely. Using these closely linked flanking markers, nine other gall midge-resistant genotypes were identified as carrying the same gene Gm8. Through marker-assisted selection, Gm8 has been introgressed into an elite bacterial blight-resistant cultivar, Improved Samba-Mahsuri (IS). 相似文献
999.
Moytri RoyChowdhury Yulin Jia Aaron Jackson Melissa H. Jia Robert Fjellstrom Richard D. Cartwright 《Euphytica》2012,184(1):35-46
The Pi-z gene in rice confers resistance to a wide range of races of the rice blast fungus, Magnaporthe oryzae. The objective of this study was to characterize Pi-z in 111 rice germplasm accessions using DNA markers and pathogenicity assays. The existence of Pi-z in rice germplasm was detected by using four simple sequence repeat (SSR) markers (RM527, AP4791, AP5659-1, AP5659-5) closely
linked to Pi-z, and was verified using pathogenicity assays with an avirulent strain (IE1k) and two virulent races (IB33 and IB49). Among
111 germplasm accessions evaluated, 73 were found to contain the Pi-z gene using both SSR markers and pathogenicity assays. The remaining 38 germplasm accessions were found to be inconsistent
in their responses to the blast races IB33, IEIk and IB49 with expected SSR marker alleles, suggesting the presence of unexpected
SSR alleles and additional R gene(s). These characterized germplasm can be used for genetic studies and marker-assisted breeding for improving blast resistance
in rice. 相似文献
1000.
Mohammad Monirul Islam Eef Meerschman Timothy Saey Philippe De Smedt Ellen Van De Vijver Marc Van Meirvenne 《Precision Agriculture》2012,13(3):384-392
Every growing season, paddy fields are kept both flooded and drained for a significant period of time. As a consequence, these
soils develop distinct physico-chemical characteristics. For practical reasons, these soils are mostly sampled under dry conditions,
but the question arises how representative the results are for the wet growing conditions. Therefore, the apparent electrical
conductivity (ECa) of a 1.4 ha alluvial paddy field located in the Brahmaputra floodplain of Bangladesh was measured in both dry and wet conditions
by a sensing system using the electromagnetic induction sensor EM38, which does not require physical contact with the soil,
and compared both surveys. Due to the smooth water surface under wet conditions which ensured increased stability of the sensing
platform, the results of the survey showed considerably reduced micro-scale variability of ECa. Furthermore, the wet survey results more reliably furnished soil-related information mainly due to the absence of soil moisture
dynamics. The differences between ECa under wet and dry conditions were attributed to differences in soil texture, mainly the sand content variation having considerable
effect on soil moisture differences when flooded following drainage. Accordingly, the largest differences between ECa under wet and dry conditions were found in those parts of the field with a large sand content. Hence, the conclusion was
that an ECa survey on flooded fields has an added value to precision soil management. 相似文献