全文获取类型
收费全文 | 1340篇 |
免费 | 68篇 |
国内免费 | 139篇 |
专业分类
林业 | 51篇 |
农学 | 368篇 |
基础科学 | 2篇 |
55篇 | |
综合类 | 593篇 |
农作物 | 100篇 |
水产渔业 | 109篇 |
畜牧兽医 | 193篇 |
园艺 | 56篇 |
植物保护 | 20篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 15篇 |
2021年 | 18篇 |
2020年 | 28篇 |
2019年 | 37篇 |
2018年 | 28篇 |
2017年 | 31篇 |
2016年 | 48篇 |
2015年 | 48篇 |
2014年 | 49篇 |
2013年 | 54篇 |
2012年 | 82篇 |
2011年 | 83篇 |
2010年 | 56篇 |
2009年 | 84篇 |
2008年 | 92篇 |
2007年 | 61篇 |
2006年 | 85篇 |
2005年 | 52篇 |
2004年 | 48篇 |
2003年 | 38篇 |
2002年 | 38篇 |
2001年 | 36篇 |
2000年 | 30篇 |
1999年 | 24篇 |
1998年 | 34篇 |
1997年 | 26篇 |
1996年 | 29篇 |
1995年 | 25篇 |
1994年 | 36篇 |
1993年 | 28篇 |
1992年 | 26篇 |
1991年 | 34篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1962年 | 1篇 |
排序方式: 共有1547条查询结果,搜索用时 0 毫秒
31.
为了创造小麦-长穗偃麦草染色体易位系,本研究将“中国春”-长穗偃麦草3E二体附加系与“中国春”-柱穗山羊草2C二体附加系进行了正反交、F1代自交和回交,利用细胞遗传学等方法对杂种后代进行了鉴定。以“中国春”-长穗偃麦草3E二体附加系为母本的杂交组合,其杂交当代结实率平均为37.3%,而以“中国春”-杀配子染色体2C二体附加系为母本的杂交组合,其平均结实率为28.19%,二者差异显著(P<0.05)。杂种F1代自交结实率平均为31.45%,用“中国春”-长穗偃麦草3E二体附加系为父本的F1代回交结实率为38.82%,二者差异显著(P<0.05)。在杂交后代有丝分裂和减数分裂中观察到了染色体畸变现象,说明杀配子染色体2C在配子的形成过程中起作用。这些研究结果为进一步创制小麦-长穗偃麦草3E染色体易位系奠定了基础。 相似文献
32.
不同预处理方法对柠檬桉染色体制片技术的影响 总被引:1,自引:0,他引:1
以柠檬桉种子的根尖为研究材料,通过比较了3种浓度的秋水仙素、2 mmol·L-1的8-羟基喹啉、冰水混合物及以不同比例冰水混合物和0.1%的秋水仙素的混合液等预处理,在多个时间梯度对柠檬桉根尖染色体制片的影响进行了研究,结果发现:3种浓度秋水仙素预处理中,0.1%秋水仙素预处理1.5 h的染色体浓缩适中,分散性好,有较多的分裂相;2 mmol·L-1的8-羟基喹啉预处理的染色体均分散性较差,且分裂相较少;冰水混合物预处理12 h 的染色体浓缩适中且分裂相较多,分散程度较好。其余处理时间的染色体浓缩程度不理想,不易进行染色体分析;混合液中2:3比例下的染色体分散性较好,且浓缩程度适中,有较多的分裂相,综合比较结果由优到劣的处理方法为:0.1%秋水仙素预处理1.5 h>2:3混合液>冰水混合物处理12 h>2 mmol·L-1的8-羟基喹啉,其中在上午11:30—12:30取材,0.1%的秋水仙素处理根尖1.5 h,效果最佳。 相似文献
33.
Shimelis?HusseinEmail author Johan?J.?Spies Zakkie?A.?Pretorius Maryke?T.?Labuschagne 《Euphytica》2005,141(3):209-216
Langdon durum D-genome disomic substitution lines were used to study the chromosome locations of adult-plant leaf rust resistance genes identified from tetraploid wheat accessions. The accessions are 104 (Triticum turgidum subsp. dicoccum var. arras) and 127 (T. turgidum subsp. durum var. aestivum). The complete sets of the substitution lines were crossed as female parents with the accessions and F1 double monosomic individuals selected at metaphase I. Segregating F2 individuals were inoculated during the flag leaf stage with pathotype UVPrt2 of Puccinia triticina. The substitution analysis involving accession 104 showed that the gene for leaf rust resistance is located on chromosome 6B. The analysis with accession 127 indicated that chromosome 4A carries a gene for leaf rust resistance. The two novel genes are temporarily designated as Lrac104 and Lrac127, respectively from accessions 104 and 127. 相似文献
34.
通过分子标记辅助选择将耐储藏主效QTL qSS-9~(Kas)转入宁粳4号提高其种子贮藏能力 总被引:1,自引:0,他引:1
利用置换系SL36作为qSS-9位点上Kasalath等位基因的供体亲本,各方面农艺性状较好的宁粳4号作为轮回亲本,通过回交和自交,并使用4个与qSS-9紧密连锁的分子标记Y-10、Y-11、Y-14、Y-13进行基因型的检测筛选,对宁粳4号进行耐贮性的遗传改良,获得了既耐贮藏、大多农艺性状又接近于宁粳4号的较为稳定的优良新品系,克服了宁粳4号耐贮藏性差的弱点。获得的新品系种子在人工老化和自然老化条件下均表现出发芽率明显提高、丙二醛含量显著降低、TTC染色效果更明显,表明转入耐储藏主效QTL Qss-9~(Kas)的宁粳4号新品系耐贮性显著提高。 相似文献
35.
Esdras M. Carbajal M. Carolina Zuleta Luellen Swayzer Brian M. Schwartz Maria Carolina Chavarro A. Carolina Ballen‐Taborda Susana R. Milla‐Lewis 《Plant Breeding》2019,138(6):958-966
St. Augustinegrass is well suited for lawns and commercial landscapes. While many genotypes are cross‐fertile, all cultivars are propagated vegetatively in sod production. To ensure varietal purity, development of sterile triploid hybrids by crossing tetraploid and diploid genotypes has been successfully used in other warm‐season turfgrasses. Applying this model in St. Augustinegrass would be beneficial to sod producers and turf managers who require purity for certification and uniformity for performance, respectively. This study was conducted to develop colchicine‐induced tetraploid lines of St. Augustinegrass. Seeds of cultivar ‘Raleigh’ were treated with four colchicine concentrations at four exposure times. A non‐treated control was included among the treatments. Seedlings that germinated were screened for genome size changes using flow cytometry. Line DSA 13005 and two progeny lines derived through selfing, DSA 16001 and DSA 16016, were corroborated as tetraploids (2n = 4x = 36) through chromosome counts. These lines will be used in future breeding efforts to attempt development of sterile triploid cultivars of St. Augustinegrass. 相似文献
36.
平邑甜茶与扎矮山定子杂交后代的倍性鉴定及核型分析 总被引:2,自引:0,他引:2
为了确定平邑甜茶[Malus hupehensis(Pamp.)Rehd]与扎矮山定子[Malus Baccata(L.)Borkh]杂交后代的倍性特征和核型特点,以风油精为预处理液采用常规压片法对杂交后代进行染色体数目观察和核型分析,以亲本和普通山定子为对照。结果表明:供试材料中6株皱叶型株系均为四倍体,2n=4x=68。染色体均为小型,染色体长度比差异不大,核型组成由中部着丝点染色体(m)和亚中部着丝点染色体(sm)组成。株系10#、14#、15#、19#、28#、33#核型公式分别为,2n=4x=44m+24sm,2n=4x=60m+8sm,2n=4x=20m+48sm,2n=4x=52m+16sm,2n=4x=56m+12sm,2n=4x=48m+20sm,核型分别为1B、2B、2A、2B、1A和1B类型;1株光叶株系为非整倍体,2n=43,核型公式为2n=22m+18sm+3st,核型为2B类型。表现为株系之间的核型不完全相同。试验为丰富无融合生殖型砧木的育种理论,获得新的苹果无融合生殖型砧木提供有益的借鉴。 相似文献
37.
CS‐B14Sh and CS‐B22Sh are cotton interspecific chromosome substitution (CS)‐B lines, in which a pair of short arms of chromosome 14 and chromosome 22 were introgressed from Gossypium barbadense doubled‐haploid line 3‐79 with the background of Gossypium hirsutum line TM‐1, respectively. These two CS‐B lines were crossed with TM‐1, and segregating progenies (F2 and F2:3, respectively) were obtained. Phenotypic data of lint yield, yield‐related traits and fibre‐quality traits were collected from two trials. In the cross CS‐B14SH X TM‐1, QTL for boll weight (BW), lint percentage (LP), fibre upper half mean length (UHML), micronaire reading (MIC), and fibre breaking tensile strength (STR) were repeatedly detected. Alleles from 3‐79 decreased BW and MIC, but increased UHML and STR. In the cross CS‐B22Sh X TM‐1, QTL for BW, LP, UHML, MIC, STR, fibre elongation (EL),seed weight(SW), node of first fruiting branch (NFB) and fibre uniformity index (UI) were repeatedly detected, and alleles from 3‐79 decreased UHML, UI and STR, but increased NFB, SW, MIC and EL. QTL clusters were found in both populations. 相似文献
38.
甘蔗根尖染色体制片技术研究 总被引:3,自引:1,他引:3
甘蔗是异源多倍体植物,染色体数目多、体积小,染色体制片困难,导致细胞遗传学研究进展缓慢。以分裂旺盛的甘蔗根尖为材料,对不同采样时间、预处理方法、解离时间、染色方法等各技术环节进行实验研究。结果表明:在冬季气温较低的条件下,于15:00进行采样,饱和对二氯苯与0.002 mol/L 8-羟基喹啉等体积混合液室温预处理4~4.5 h,1 mol/L HCl与45%乙酸等体积混合液于60℃水浴锅解离8 min后,用改良苯酚卡宝品红进行涂片滴染,所获得的染色体制片效果最好。 相似文献
39.
Job shop scheduling is an important part of manufacturing process. Pre-mature, local optimal solution or low convergence rate of Genetic Algorithm may come across in solving scheduling problem in multi-Job shop. To avoid those unhealthy tendencies, this paper introduced the Dynamical Niche Sets-based Cooperative Evolutionary Algorithm model.In the Algorithm, Process-based chromosome encoding method was used; the crossover operator and mutation operator were designed to adjust operation sequences and choose process routes. The cooperative scheduling problem in multi-Job shop was solved using dynamical niche sets technology and multi-population cooperative evolution method. The Experiment result shows the proposed method has good advantages. 相似文献
40.