全文获取类型
收费全文 | 1107篇 |
免费 | 141篇 |
国内免费 | 693篇 |
出版年
2024年 | 15篇 |
2023年 | 40篇 |
2022年 | 54篇 |
2021年 | 75篇 |
2020年 | 57篇 |
2019年 | 62篇 |
2018年 | 45篇 |
2017年 | 53篇 |
2016年 | 40篇 |
2015年 | 60篇 |
2014年 | 91篇 |
2013年 | 92篇 |
2012年 | 119篇 |
2011年 | 112篇 |
2010年 | 104篇 |
2009年 | 98篇 |
2008年 | 122篇 |
2007年 | 148篇 |
2006年 | 108篇 |
2005年 | 93篇 |
2004年 | 69篇 |
2003年 | 53篇 |
2002年 | 36篇 |
2001年 | 57篇 |
2000年 | 38篇 |
1999年 | 30篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1956年 | 2篇 |
1954年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有1941条查询结果,搜索用时 15 毫秒
981.
三倍体换锦花在安徽发现 总被引:5,自引:0,他引:5
本文对分布于安徽江南和江淮两个地区野生居群的换锦花Lycoris sprengeri进行了细胞学研究,
发现换锦花为一复合体,包括两个不同类型:(1)三倍体类型,分布于安徽马鞍山市采石的野生居群,其
染色体数目和核型为2n=33=9st+21t+3T,属4A核型,极其稳定,该种的三倍体类型为首次发现;(2)
二倍体类型,分布于滁州市琅琊山的野生居群,发现有2个核型,核型I,2n=22=8st+14t,属4A核型,
约占观察细胞的80%;核型Ⅱ,2n=22=1m+1sm+14st+6t,属3B核型,约占观察细胞的20%,该染色
体核型为首次报道。换锦花三倍体居群和二倍体居群的植物外部形态特征基本相同。本文还指出罗伯逊变化在石蒜属核型演化中起了关键作用。 相似文献
982.
拟南芥LFYcDNA的克隆及转化菊花的研究 总被引:22,自引:0,他引:22
以野生型拟南芥(Arabidopsisthaliana(L.)Heynh.)为材料,克隆并测序了Leafy(LFY)基因的全长cDNA;同时构建了LFYcDNA以CaMV35S为启动子的植物表达载体,并转化菊花(Chrysanthemummorifolium(Ramat.)Tzvel.)。该cDNA全长1263bp,共编码420个氨基酸残基,Southern杂交结果表明,LFYcDNA整合到菊花染色体组中。跟正常植株相比,转基因植株中有3株分别提早65、67、70d开花,2株分别推迟78、90d开花。 相似文献
983.
984.
985.
986.
QIN Jing-Dong SHAO Ning SHI Ding-Ji XU Xu-Dong ZHANG Jin-Dong GUO Ping-Zhong WANG Wen-Qing TANG Pei-Song 《植物学报(英文版)》1999,41(1)
A recombinate plasmid pDC-ATGS was constructed, which contained the antisense fragment of glnA gene from Anabaena sp. PCC 7120 and transformed the unicellular cyanobactefium Synechococcus sp. PCC 7942. The foreign DNA was inserted into the site of glnA locus of the chromosome through the homologous recombination. By using neomyisin, a highly efficient ammonia secretion mutant was selected. After immobilized, the cells of the mutant within polyurethane (PU) foams, glutamine synthetase (GS) and NIt4+ secretory activity of GS, and its growth and photosynthesis were measured. It was shown that NH4+ secretion of the immobilized mutant was enhanced 156 folds which was much higher than that of free-living cells of the wild type. The activity of GS was decreased by 73.6%. Growth of the mutant was the same as that of the wild type. The activity of photosystem Ⅱ in the immobilized mutant cells increased by 44% with 77 K fluorescence spectrum measurement. 相似文献
987.
l103s was a rice ( Oryza sativa L. ) mutant whose leaves would mm into chimerical chlorophylldeficient when treated with varied temperature (high - low - high). The alteration of whole leaf protein was studied with two-dimensional electrophoresis during the bleaching process. No changes of large subunit and small subunit of Rubisco had been detected in the bleached tissues of 1103s, but a 51 kD (PI =-4.5) special polypeptide-P1 disappeared in the white area during the bleaching process. P1 polypeptide was also detected in those tissues which remained green on the chlorophyll deficient leaves, although its amount apparenfiy decreased. In the tissue of low-temperature treated 1103s and l103s × 8902s, the normal expression of P1 polypeptide had been detected. The data suggest that P1 is an important chlorophyll-synthesis related down stream functional protein. In 1103s, it is regulated by some yet-tmknown temperature-sensitive mechanisms. 相似文献
988.
The green-yellow bands interrupted discolorated transverse bands on the leaves of the thermo-sensitive rice line l103s (Oryza sativa ssp. indica ) was induced by cold shock and the change of leaf color coincided with the change of chlorophyll contents. Uhrastmctural observation revealed that the chloroplast slructure in the yellow part degenerated, i.e., the number of stocks in granum abnormally decreased, thylakoid system was disintegrated and replaced by few single thylakoid, and then the whole structure of some chloroplast became vesicle-hke structure with high electronic density. Nonetheless, in the green zone of the green-yellow banded leaf, there were slight decrease in the number granum thylakoids, disordered grana arrangement in the chloroplast, and aggregation of osmiophile globule. However, it was found that these structural alternations were reversable in the process of recovery of the yellow part of the leaves into green, and the chloroplast structure renewed normally. It might be concluded that the character of green-yellow bands induced by cold shock was consequent upon a reverse process of degeneration and regeneration. 相似文献
989.
新种祁门过路黄的核型证据 总被引:2,自引:0,他引:2
对新种祁门过路黄及其近缘种巴东过路黄和光叶巴东过路黄的核型在居群水平上进行了比较研究。结果表明这两种植物的核型特征在种内是稳定的,同一物种的不同居群间核型无明显差异。祁门过路黄的核型为2n=2x=24=6m+6sm+6st+6t;巴东过路黄和光叶巴东过路黄的核型均为2n=2x=24=6m+4sm+6st+8t;两物种间核型差异显著,核型特征支持将祁门过路黄作为新种处理。 相似文献
990.