全文获取类型
收费全文 | 2522篇 |
免费 | 141篇 |
国内免费 | 189篇 |
专业分类
2852篇 |
出版年
2024年 | 3篇 |
2023年 | 30篇 |
2022年 | 53篇 |
2021年 | 64篇 |
2020年 | 42篇 |
2019年 | 55篇 |
2018年 | 69篇 |
2017年 | 52篇 |
2016年 | 56篇 |
2015年 | 61篇 |
2014年 | 66篇 |
2013年 | 146篇 |
2012年 | 64篇 |
2011年 | 77篇 |
2010年 | 63篇 |
2009年 | 94篇 |
2008年 | 98篇 |
2007年 | 131篇 |
2006年 | 151篇 |
2005年 | 120篇 |
2004年 | 110篇 |
2003年 | 111篇 |
2002年 | 105篇 |
2001年 | 85篇 |
2000年 | 97篇 |
1999年 | 93篇 |
1998年 | 71篇 |
1997年 | 61篇 |
1996年 | 87篇 |
1995年 | 57篇 |
1994年 | 52篇 |
1993年 | 67篇 |
1992年 | 46篇 |
1991年 | 40篇 |
1990年 | 33篇 |
1989年 | 37篇 |
1988年 | 42篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 29篇 |
1984年 | 13篇 |
1983年 | 19篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有2852条查询结果,搜索用时 10 毫秒
211.
212.
目前,有关不定芽发生的研究主要集中在单基因的调控方面,缺乏转录组方面的系统研究.利用RNA-seq高通量测序技术在全基因组范围内检测了不定芽发生早期的基因表达谱,共检测到2457个差异表达基因.这些基因参与了激素代谢和信号转导、愈伤组织和侧根的形成、茎顶端分生组织的发育和光合作用等过程.进一步的途径富集分析表明,不定芽发生早期苯丙氨酸代谢和苯丙胺素合成等途径相关的基因显著富集.并且苯丙氨酸可以显著抑制不定芽的发生,暗示了苯丙氨酸代谢和苯丙胺素的合成可能在不定芽发生过程起着重要的作用. 相似文献
213.
Y. Kaneda Y. Tabei S. Nishimura K. Harada T. Akihama K. Kitamura 《Plant cell reports》1997,17(1):8-12
A successful, efficient system for multiple soybean shoot induction of soybean [Glycine max (L.) Merr.] is reported. Multiple shoots were induced from cotyledonary nodes and hypocotyl segments cultured on media supplemented
with 2 mg/l thidiazuron (TDZ) or 1.15 mg/l benzyladenine (BA). It was found that TDZ induced adventitious shoots more efficiently
than BA and that hypocotyl segments promoted more adventitious shoots than cotyledonary nodes. The optimal TDZ concentrations
for shoot organogenesis from hypocotyl segments were between 1 and 2 mg/l. Basal media also influenced the efficiency of shoot
organogenesis. The frequency of adventitious shoot formation tended to increase when the salt concentration in the basal media
supplemented with 2 mg/l TDZ was reduced. Two media (1/2B5 and 1/2L2) stimulated shoot organogenesis efficiently from hypocotyl
segments. This method can thus be advantageously applied in the production of transgenic soybean plants.
Received: 3 July 1996 / Accepted: 9 May 1997 相似文献
214.
为建立龙珠果(Passiflora foetida)的快繁再生体系,以实生苗茎段为外植体,研究了植物生长调节剂对丛生芽诱导、壮苗生根的影响,同时对组培苗的耐盐性进行研究.结果表明,MS+6-BA 0.5 mg/L+NAA 0.05 mg/L培养基有利于诱导丛生芽并促进芽的生长;MS+6-BA 3.0 mg/L+NAA ... 相似文献
215.
本文详细报道了从秃杉(Taiwania flousiana Gaussen)离体胚诱导不定芽、不定根及从无菌苗茎端培养再生植株的过程。诱导不定芽要求较低的蔗糖浓度(以3%最好);同时BA是必须的,在附加0.1—3 mg/1 BA的White培养基上,从离体胚的子叶或胚轴上诱导了不定芽的发生(以1 mg/1最好);NAA与BA结合使用,对不定芽诱导无促进作用;适当提高光照有利于不定芽的诱导。在诱导不定芽的同时,在子叶表面还观察到有许多无结构的“不定突起”。不定芽起源于子叶表皮下1—2层细胞。IBA对诱导离体胚上产生不定根效果较好。在有或无生长素的培养基上,从生长1月龄的无菌苗茎端培养获得了不定根的产生,在加有细胞分裂索的培养基上,从无菌苗上产生了腋芽。 相似文献
216.
Phytoremediation is an alternative to other technologies for the clean up of petroleum contaminated soil. Ten vegetatively propagated cultivars of bermudagrass were examined for their potential to reduced oil sludge contaminated in soil and select the most efficient cultivar. Soil was mixed with different rates of oil sludge (0, 10, 20, 30, and 40% (w/w) to obtain 0, 2, 4, 6, and 8% total petroleum hydrocarbons (TPHs). Ten cultivars of bermudagrass were planted in pots filled with respected mixtures of soil and sludge. Shoot and root weights and percent reduction in the contamination level were measured after six months. Shoot weight reduced as contamination level increased. The root weight increased up to 6% TPHs level. As contamination level increased, the percent reduction in contamination increased. Reduction was 37.7, 41.0, 35.0, 34.0, 45.0, 41.3, 34.5, 41.3, 34.5, 41.3, 55.0, and 43.6% under Tifdwarf, Tifgreen, Tifway, ISF1, ISF2, JP1, JP2, and Midlawn, 3200W18-4 and 3200W19-9 at the highest contamination level 3200W18-4 was the most effective cultivar followed by ISF2, 3200W19-9, JPI, and Midlawn, respectively. The results suggested that bermudagrass is an efficient species for phytoremediation of petroleum contaminated soil and the selection for more tolerant and efficient cultivar is possible. 相似文献
217.
218.
219.
G. Müller-Starck M. Ziehe 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,69(2):173-177
Summary In order to quantify female and male fitness values of clones in a Pinus sylvestris L. seed orchard, multilocus-genotypes of parental clones were compared with those of open pollinated seeds in the bulked orchard crop. Female and male contributions to individual seeds were distinguished by observing enzyme gene loci active in both endosperm and embryo tissue. Seed probes from two successive flowering periods were surveyed. The female and male fitnesses of five parental clones measured relative to the population mean were derived. The contributions of four clones were found to be sexually asymmetric. One clone, for instance, made exclusively female contributions in one flowering period. Variations existed in fitness values between clones. Deviations in sex specificity occurred between flowering periods: one clone contributed asymmetrically in both periods, but in sexually reversed proportions. A method to comprehensively quantify and illustrate the observed phenomena is proposed. 相似文献
220.
Irrespective of their age, leaves of Ginkgo biloba metabolised applied 8 (14C) zeatin to compounds of similar chromatographic properties. Glucosylation is apparently not a normal feature of cytokinin metabolism in immature leaves. However, the application of zeatin to these leaves did result in the formation of metabolites which co-chromatographed with glucosylated cytokinins. As far as cytokinin metabolism is concerned therefore, this application of excess zeatin allowed immature leaves to behave as mature or senescing leaves. Overall metabolism was fastest in immature leaves. From the metabolites formed it would appear as if oxidation, which resulted in the formation of a metabolite which co-eluted with N-(purin-6-yl)glycine, was also important in immature leaves. In senescing leaves glucosylation was the major form of metabolism. Extraction and re-application of the polar metabolites (formed from zeatin) to mature leaves resulted in the formation of compounds which co-chromatographed with zeatin. This suggests that these compounds could serve as precursors for zeatin or could be hydrolysed to form zeatin.Very little of the applied radioactivity was exported from the leaves irrespective of their physiological age. When the metabolites, obtained after zeatin application to mature leaves, were extracted and reapplied to the leaves, export of radioactive material was much improved. The results suggest that should cytokinins such as zeatin be translocated to mature leaves of this deciduous gymnosperm their export from the leaves would be unlikely unless first metabolised. In all probability the metabolites concerned are cytokinin glucosides.The financial support of the C.S.I.R., Pretoria, is gratefully acknowledged. 相似文献