全文获取类型
收费全文 | 4570篇 |
免费 | 145篇 |
国内免费 | 390篇 |
专业分类
5105篇 |
出版年
2024年 | 15篇 |
2023年 | 62篇 |
2022年 | 68篇 |
2021年 | 83篇 |
2020年 | 79篇 |
2019年 | 109篇 |
2018年 | 70篇 |
2017年 | 68篇 |
2016年 | 64篇 |
2015年 | 89篇 |
2014年 | 132篇 |
2013年 | 228篇 |
2012年 | 130篇 |
2011年 | 155篇 |
2010年 | 115篇 |
2009年 | 196篇 |
2008年 | 223篇 |
2007年 | 244篇 |
2006年 | 228篇 |
2005年 | 243篇 |
2004年 | 239篇 |
2003年 | 194篇 |
2002年 | 179篇 |
2001年 | 153篇 |
2000年 | 168篇 |
1999年 | 140篇 |
1998年 | 133篇 |
1997年 | 106篇 |
1996年 | 108篇 |
1995年 | 107篇 |
1994年 | 96篇 |
1993年 | 88篇 |
1992年 | 105篇 |
1991年 | 86篇 |
1990年 | 55篇 |
1989年 | 62篇 |
1988年 | 54篇 |
1987年 | 63篇 |
1986年 | 43篇 |
1985年 | 62篇 |
1984年 | 52篇 |
1983年 | 21篇 |
1982年 | 30篇 |
1981年 | 26篇 |
1980年 | 29篇 |
1979年 | 30篇 |
1978年 | 24篇 |
1977年 | 9篇 |
1976年 | 16篇 |
1973年 | 8篇 |
排序方式: 共有5105条查询结果,搜索用时 0 毫秒
161.
162.
Excessive activation of the hormone signaling pathways is implicated in several disorders of the target tissues, with cancer being one of the most serious fallouts. Steroid hormone receptors are key proteins through which steroid hormones convey their signals to the cells. Deregulated activity of the hormone receptors due to their altered activation; stability or sub-cellular localization is heavily implicated in the onset and progress of cancers. The role played by estrogen and its receptors in breast cancer remains the most thoroughly investigated steroid-dependent cancer system till date. Choosing it as an example, we have summarized the molecular mechanisms underlying the action of the estrogen receptors (ERs) in manifesting the effects of the estrogens in the cells. A special emphasis is placed on the molecular mechanism of their functionality, role of the coactivator proteins, and the reasons for the deregulated signaling. The therapeutic approaches resulting from the mechanistic study of the ER action and their efficacies are also discussed. 相似文献
163.
花生四烯酸作为一种重要的多价不饱和脂肪酸,因其具有多种生理功能而被认为是潜在的食品添加剂和药物。近年来,利用高山被孢霉合成花生四烯酸已成为研究热点。前期相关研究主要集中在菌种选育及发酵调控方面。随着研究的不断深入,关于高山被孢霉合成花生四烯酸的代谢途径的研究取得了较大进展。以下简要概述前期工作进展,着重论述花生四烯酸合成途径的关键酶及其高山被孢霉的遗传改造的研究情况,包括生物合成花生四烯酸代谢途径、关键酶及其应用、高山被孢霉的遗传操作系统的构建以及遗传改造的应用,并对其研究前景进行了展望。 相似文献
164.
165.
Krasnyanskaya V. Belova L. P. Velikanov G. A. Widholm J. Lozovaya V. V. 《Russian Journal of Plant Physiology》2002,49(6):804-809
Using Agrobacterium rhizogenes, Astragalus sinicus plants were transformed with the kidney bean pal5 gene coding for phenylalanine-ammonia lyase (PAL). The hairy root culture thus obtained manifested enhanced PAL activity and lignin content in the cell walls; in addition, the transformed cells differed from the wild-type ones in several electrophysiological indices. In particular, the diffusion component of the total membrane potential of plasmalemma increased in the pal-transformed roots. The authors presume that the volume density of the protein-related negative charge of the cytoplasm increases in the transformed root cells along with changes in the cytoplasmic pH and pCa2+, the extent of coupling of these two indices, and the hydraulic conductivity of plasmodesmata. 相似文献
166.
167.
Morphologically normal and fertile transgenic plants of mungbean with two transgenes, bar and α-amylase inhibitor, have been developed for the first time. Cotyledonary node explants were transformed by cocultivation
with Agrobacterium tumefaciens strain EHA105 harboring a binary vector pKSB that carried bialaphos resistance (bar) gene and Phaseolus vulgaris α-amylase inhibitor-1 (αAI-1) gene. Green transformed shoots were regenerated and rooted on medium containing phosphinothricin (PPT). Preculture and
wounding of the explants, presence of acetosyringone and PPT-based selection of transformants played significant role in enhancing
transformation frequency. Presence and expression of the bar gene in primary transformants was evidenced by PCR-Southern analysis and PPT leaf paint assay, respectively. Integration
of the Phaseolus vulgaris α-amylase inhibitor gene was confirmed by Southern blot analysis. PCR analysis revealed inheritance of both the transgenes
in most of the T1 lines. Tolerance to herbicide was evidenced from seed germination test and chlorophenol red assay in T1 plants. Transgenic plants could be recovered after 8–10 weeks of cocultivation with Agrobacterium. An overall transformation frequency of 1.51% was achieved. 相似文献
168.
Non-transformed and transformed embryogenic cultures of alfalfa (Medicago sativa L. cv. Zaječarska 83), long-term maintained on growth regulator-free medium, were histologically analyzed. In all examined
cultures, somatic embryos at various stages of development were observed and secondary embryos were formed in the cotyledonary,
hypocotylary and radicular region of the primary embryos. Detailed histological analysis of the torpedo shape somatic embryo
revealed that secondary somatic embryos arose directly from single epidermal cells of hypocotylary axis after an unequal periclinal
division. Bipolar proembryos were composed of one smaller cytoplasm rich cell and one larger more vacuolated cell. Further
cell division pattern was similar for both non-transformed and transformed embryos. However, multicellular origin of secondary
embryos in a direct process and even from callus can not be excluded. 相似文献
169.
Microprojectile bombardment is a powerful method for the transformation of various organisms and tissues. For plants, the
biolistic approach is primarily used for transformation of cereals and other monocotyledons, as well as for dicotyledonous
plants shown to be recalcitrant to Agrobacterium-based transformation of organellar genomes, and transformation of plant and algal chloroplasts has recently been reported.
In this protocol paper we provide methods for nuclear and plastomic transformation of plants using the biolistic technique. 相似文献
170.