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971.
Because of the difficulty of producing F1 hybrid seeds by hand emasculation and pollination, wide use of heterosis in cotton production has been limited in China. The objective of this study was to evaluate the potential of F2 hybrids for yield and fibre quality. A half diallel involving eight parents and their F1 and F2 hybrids was grown in replicated studies at Linqing and Nanjing in 1999 and Nanjing in 2000. Yield and fibre quality was determined for all 64 entries. Fibre quality was also determined for parents and F1s, but only for Zhongmiansuo 28 (ZMS28), Xiangzamian 2 (XZM2) and Wanmian 13 (WM13) F2s. These three F2 hybrids are extensively planted in China and provide experimental controls with which to compare the performance of new hybrids. Average yield heterosis for F1s and F2s was 15.9 and 9.2%, respectively. Inbreeding depression for yield varied but some F2s greatly out‐yielded the best variety. Average F1 heterosis was 6.7, 6.2 and 2.9%, respectively for number of bolls per unit area, boll weight, and lint percentage. The average F2 heterosis for the same traits was 4.4, 3.3 and 1.6%, respectively. F1 heterosis for fibre traits was low. In general, parental average was a good indicator of the yield and fibre quality of F1 hybrids. These encouraging results suggest there is sufficient heterosis for yield to use F2s in China. 相似文献
972.
Field trials in two cropping seasons and two locations in central China were conducted on 60 Chinese autumn‐sown wheat varieties to assess their partial resistance to powdery mildew. Mean levels of disease severity ranged from close to 0 to more than 90%. The method of inoculation and the location in which trials were conducted affected the relative performance of the varieties, but these effects were much smaller than the main effect of variety. The area under the disease progress curve was highly correlated with final disease severity, but both were poorly correlated with apparent infection rate. Disease severity was regressed against frequencies of virulence in the Blumeria graminis (syn. Erysiphe graminis) f sp. tritici populations in the trial plots. A vertical distance (D) from the mean mildew severity to the fitted line was calculated for each variety and was used to quantify partial resistance. Five of the 60 varieties, ‘Hx8541’, ‘E28547’, ‘Chuan1066’, ‘Zhe88pin6’ and ‘Lin5064’, consistently expressed relatively low levels of disease despite high frequencies of virulence in the pathogen and had consistently high D‐values. They may therefore have good levels of partial resistance. 相似文献
973.
QTL analysis of cooked rice grain elongation, volume expansion, and water absorption using a recombinant inbred population 总被引:7,自引:0,他引:7
The traits of elongation, volume expansion, and water absorption are very important in determining the quality of cooked rice grains. In this study, quantitative trait loci (QTL) analysis of these traits was performed using a recombinant inbred population derived from a cross between two indica cultivars, ‘Zhenshan 97’ and ‘Minghui 63 ,’ which are the parents of the most widely grown hybrid rice in China. Using a linkage map based on 221 molecular marker loci covering a total of 1796 cM, a total of 33 QTLs were identified for the nine traits tested. QTLs were detected on chromosomes 1– 3 , 5– 9 , and 11 , respectively. The QTLs identified included three for cooked rice grain length elongation (chromosomes 2 , 6 , and 11), six for width expansion (chromosomes 1‐ 3 , 6 , 9 , and 11) and two for water absorption (chromosomes 2 and 6). Interestingly, a single QTL located near the wx gene on chromosome 6 seemed to influence all the traits tested for the cooked rice quality. 相似文献
974.
Analysis of Unbalanced Data by Mixed Linear Models Using the mixed Procedure of the SAS System 总被引:2,自引:0,他引:2
Unbalanced data are a common problem in plant research based on designed experiments. Such data are often conveniently analysed using linear mixed models. Recent developments in mixed model theory have been implemented in major packages. This paper describes the use of the mixed procedure of the SAS System for the analysis of designed experiments. Special emphasis is given to the specification of options as depending on the assumed mixed model and on the unbalancedness in the data. In addition, we consider a compact representation of multiple comparisons for unbalanced data (letter display). Two small data sets are used to exemplify the methods. 相似文献
975.
Pyramiding of Xa7 and Xa21 for the improvement of disease resistance to bacterial blight in hybrid rice 总被引:3,自引:0,他引:3
‘Minghui 63’ is a restorer line widely used in hybrid rice production in China for the last two decades. This line and its derived hybrids, including ‘Shanyou 63’, are susceptible to bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo). To improve the bacterial blight resistance of hybrid rice, two resistance genes Xa21 and Xa7, have been introgressed into ‘Minghui 63’ by marker‐assisted selection and conventional backcrossing, respectively. The single resistance gene‐introgressed lines, Minghui 63 (Xa21) and Minghui 63 (Xa7) had higher levels of resistance to bacterial blight than their derived hybrids, Shanyou 63 (Xa21) or Shanyou 63 (Xa7). Both Xa21 and Xa7 showed incomplete dominance in the heterozygous background of rice hybrids by infection with GX325 and KS‐1‐21. The improved restorer lines, with the homozygous genotypes, Xa21Xa21 or Xa7Xa7, were more resistant than their hybrids with the heterozygous genotypes Xa21xa21 or Xa7xa7. To further enhance the bacterial blight resistance of ‘Minghui 63’ and its hybrids, Xa21 and Xa7 were pyramided into the same background using molecular marker‐aided selection. The restorer lines developed with the resistance genes Xa21 and Xa7, and their derived hybrids were evaluated for resistance after inoculation with 10 isolates of pathogens from China, Japan and the Philippines, and showed a higher level of resistance to BB than the restorer lines and derived hybrids having only one of the resistance genes. The pyramided double resistance lines and their derived hybrids have the same high level of resistance to BB. These results clearly indicate that pyramiding of dominant genes is a useful approach for improving BB resistance in hybrid rice. 相似文献
976.
Elongated glumes are present in thetetraploid wheat species T.polonicum, T. turanicum, T.durum convar. falcatum and in thehexaploid species T. petropavlovskyi.Inheritance of glume length was studiedwith the aim to map the respective lociusing wheat microsatellite markers. In T. polonicum and T. petropavlovskyiloci conferring long glume were mapped nearthe centromere on chromosome 7A. These twoloci are designated P-A
pol
1 andP-A
pet
1, respectively. It isshown that both are probably homoeoallelicto each other and to the P gene ofT. ispahanicum on chromosome 7B. The loci determining elongated glumes in T. turanicum and T. durum conv. falcatum are not homoeologous to the P loci in the centromeric region of thegroup 7 chromosomes. 相似文献
977.
RAPD and SCAR markers linked to the sex expression locus M in asparagus 总被引:13,自引:0,他引:13
Bulk segregant analysis (BSA), random amplified polymorphic DNA (RAPD) and sequence characterized amplified region (SCAR)
methods were used to map molecular markers to the sex locus M of asparagus. Two parents, A19 (male, Mm) and MW25 (female,
mm), and 63 progeny were used for the study. Two DNA bulks, one male and one female, were made by pooling equal amounts of
DNA from 10 randomly selected progeny of each sex type. A total of 760 arbitrary decamer oligonucleotide primers were used
for RAPD analysis. Primer OPC15 produced two RAPD markers, OPC15-98 and OPC15-30, both of which were linked to the M locus
at a distance of 1.6 cM. Subsequently, amplified RAPD fragment OPC15-98 was cloned and sequenced. The sequence was then used
to design flanking 24-mer oligonucleotide SCAR primers SCC15-1 and SCC15-2. Both of these SCAR primers amplified a single
980 bp fragment; the same size as the cloned RAPD fragment. However, the SCAR marker was dominant as was the original OPC15-98
band from which it was derived. These RAPD and SCAR markers could be used for scoring male and female progeny in the mapping
population, but were not found to be applicable to other asparagus germplasm studied.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
978.
979.
980.
中国低酚棉品种资源群体特点及特异种质筛选 总被引:1,自引:0,他引:1
对145个国内外不同来源的低酚棉品种(系)的研究表明,中国低酚棉品种资源群体的基本特点是,皮棉产量的变异潜力较大;铃重、衣分、子指、衣指变异度较小,纤维品质性状的变异率表现相似。多数品种(系)的衣分偏低,子指较大,纤维强度低,细度中等,但纤维较长且整齐度好。在产量或品质性状方面,该资源群体含有一些特异种质;国内育成品种(系)在衣分、细度上可更好地提供优异的基因资源,而国外品种(系)在铃重,衣指,纤 相似文献