全文获取类型
收费全文 | 1670篇 |
免费 | 39篇 |
国内免费 | 130篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 6篇 |
2017年 | 12篇 |
2016年 | 16篇 |
2015年 | 27篇 |
2014年 | 47篇 |
2013年 | 46篇 |
2012年 | 48篇 |
2011年 | 37篇 |
2010年 | 37篇 |
2009年 | 46篇 |
2008年 | 44篇 |
2007年 | 63篇 |
2006年 | 50篇 |
2005年 | 61篇 |
2004年 | 67篇 |
2003年 | 61篇 |
2002年 | 47篇 |
2001年 | 36篇 |
2000年 | 50篇 |
1999年 | 81篇 |
1998年 | 85篇 |
1997年 | 88篇 |
1996年 | 53篇 |
1995年 | 71篇 |
1994年 | 57篇 |
1993年 | 51篇 |
1992年 | 59篇 |
1991年 | 65篇 |
1990年 | 67篇 |
1989年 | 43篇 |
1988年 | 35篇 |
1987年 | 45篇 |
1986年 | 38篇 |
1985年 | 48篇 |
1984年 | 36篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有1839条查询结果,搜索用时 265 毫秒
51.
培养的人胃腺癌MGc 80-3细胞经过正丁酸钠处理7天后,生长抑制率达50.7%,约有90%的细胞形态发生分化,其超微结构亦有显著改变。而且,在染色体数目上,超二倍体细胞由对照组的78%增加到实验组的96%,超三倍体和超四倍体细胞则分别从6%和14%下降至2%。同时应用~3H-TdR放射自显影和福尔根细胞光度法测定未标记细胞(G_1期)DNA含量,结果显示实验组比对照组降低了。而且在实验组的同一制片中,未分化细胞DNA含量平均为超六倍体值(DI=3.67和3.56),其中90%的细胞超过6C;分化细胞DNA含量则平均为近四倍体值(DI=2.03和1.99),其中近60%的细胞少于4C。两者差异统计显著,表明形态分化的人胃腺癌细胞的遗传物质含量明显减少,但这些细胞并非就是正常二倍体细胞。 相似文献
52.
玉米花粉单倍体植株染色体上异染色质的变异 总被引:4,自引:1,他引:3
我们用Giemsa BSG C-带技术检查了玉米花药培养获得的花粉单倍体植株根尖细胞染色体上异染色质的变异,观察结果表明,有的植株所显示的C-带数目是与供体植株的相一致,有的植株所显示的C-带数目则发生了显著变化,其中有的增加,有的减少。并讨论了异染色质发生变异的可能原因。还相应地观察到间期核中染色中心的变化是与中期染色体上C-带数目的变化相一致。 相似文献
53.
中国家猪高分辨G—带及模式图 总被引:9,自引:0,他引:9
采用氨甲喋呤或胸苷阻断法使细胞分裂同步化,并结合胰酶G-带技术,对中国7个家猪品种高分辨G-带进行了研究,发现家猪品种间带型基本一致,从而参照人类细胞遗传学命名法的国际体制,提出了中国家猪高分辨G-带标准化核型及模式图,对显带核型界标进行了少许修改,对每对染色体进行了区带划分和描述。单倍染色体组所显示的G-带数目,包括X和Y染色体,巳达444条,近于中期染色体带纹数目的两倍。 相似文献
54.
55.
56.
P. Fredman J. Dumanski P. Davidsson L. Svennerholm V. P. Collins 《Journal of neurochemistry》1990,55(6):1838-1840
The ganglioside composition of 59 meningiomas has been compared with a molecular genetic analysis of chromosome 22 in the same specimens. Major gangliosides were GM3 (II3NeuAc-LacCer) and/or GD3 [II3(NeuAc)2-LacCer]. In specimens with no or partial deletions of chromosome 22, the GM3 ganglioside predominated, and the mean value for GM3, 61% of total sialic acid, was around four times higher than that for GD3. A loss of chromosome 22, found in 56% of the specimens, was shown to be associated with an increase in the proportion of ganglioside GD3, with the ratio between mean values of GM3 and GD3 being approximately 1:1. Logistic regression revealed that the probability of predicting monosomy of chromosome 22 by the GD3 proportion was 66%. 相似文献
57.
Chromosome numbers for 26 different species of the generaPiper, Peperomia andPothomorphe (Piperaceae) are reported. The basic chromosome numbers are 2n = 26, x = 13 (Piper, Pothomorphe) and 2n = 22, x = 11 (Peperomia), polyploid series are characteristic forPiper andPeperomia. Piper has the smallest chromosomes and prochromosomal interphase nuclei,Peperomia the largest ones and mostly reticulate to euchromatic nuclei.Pothomorphe is intermediate in both characters. The karyomorphological differences betweenPothomorphe andPiper underline their generic separation. Interspecific size variation of chromosomes occurs inPiper andPeperomia. Infraspecific polyploidy was observed inPiper betle. C-banding reveals different patterns of heterochromatin (hc) distribution between the genera investigated. The genome evolution is discussed. 相似文献
58.
Marcelo dos Santos Guerra 《Plant Systematics and Evolution》1989,168(1-2):83-86
Azima tetracantha has an asymmetrical karyotype with large chromosomes and a large amount of heterochromatin. The haploid number (n = 11) may represent the base number of the family. However, a possible secondary origin of this base number is also considered. 相似文献
59.
Identification of Brassica oleracea monosomic alien chromosome addition lines with molecular markers reveals extensive gene duplication 总被引:2,自引:0,他引:2
J. Mitchell McGrath Carlos F. Quiros John J. Harada Benoit S. Landry 《Molecular & general genetics : MGG》1990,223(2):198-204
Summary Chromosomes of Brassica oleracea (2n=18) were dissected from the resynthesized amphidiploid B. napus Hakuran by repeated backcrosses to B. campestris (2n=20), creating a series of monosomic alien chromosome addition line plants (2n=21). Using morphological, isozyme and restriction fragment length polymorphism markers (RFLPs), 81 putative loci were identified. Of nine possible synteny groups, seven were represented in the 25 monosomic addition plants tested. Sequences homologous to 26% of the 61 DNA clones utilized (80% were cDNA clones) were found on more than one synteny group, indicating a high level of gene duplication. Anomalous synteny associations were detected in four 2n=21 plants. One of these plants showed two markers from one B. oleracea chromosome associated with a second complete B. oleracea synteny group, suggesting translocation or recombination between non-homologous chromosomes in Hakuran or the backcross derivatives. The other three 2n=21 plants each contained two or more B. oleracea synteny groups, suggesting chromosome substitution. 相似文献
60.
E. B. Peffley P. D. Mangum 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,79(1):113-118
Summary A diploid Allium cepa plant was recovered from the backcross of an interspecific triploid (2 x A. cepa + 1 x A. fistulosum) to an A. cepa diploid which exhibited both A. cepa and A. fistulosum Adh-1 alleles. Cytogenetic analyses revealed a recombinant sub-telocentric chromosome. The ADH-1 locus is believed to be on the long arm of the sub-telocentric A. fistulosum chromosome 5. Meiosis of the triploid progenitor gives strong evidence that recombination occurred. A. fistulosum chromosome 8 has been substituted for A. cepa chromosome 1.Contribution of the College of Agricultural Sciences, Texas Tech University, Journal No. T-4-275 相似文献