全文获取类型
收费全文 | 1686篇 |
免费 | 150篇 |
国内免费 | 28篇 |
出版年
2023年 | 21篇 |
2022年 | 18篇 |
2021年 | 72篇 |
2020年 | 44篇 |
2019年 | 52篇 |
2018年 | 63篇 |
2017年 | 54篇 |
2016年 | 65篇 |
2015年 | 77篇 |
2014年 | 99篇 |
2013年 | 114篇 |
2012年 | 151篇 |
2011年 | 153篇 |
2010年 | 77篇 |
2009年 | 61篇 |
2008年 | 104篇 |
2007年 | 80篇 |
2006年 | 67篇 |
2005年 | 68篇 |
2004年 | 41篇 |
2003年 | 45篇 |
2002年 | 38篇 |
2001年 | 24篇 |
2000年 | 25篇 |
1999年 | 27篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1969年 | 4篇 |
排序方式: 共有1864条查询结果,搜索用时 15 毫秒
1.
2.
3.
A reversed-phase high-performance liquid chromatographic method for characterization of biosynthetic human growth hormone 总被引:1,自引:0,他引:1
An isocratic reversed-phase high-performance liquid chromatographic method for the determination of human growth hormone (HGH) purity is described. This method offers superior resolution of HGH-related substances (e.g., sulfoxide and desamido derivatives) from unmodified HGH when compared to a number of alternative chromatographic and electrophoretic techniques. 相似文献
4.
异大茴香脑新资源——齿叶黄皮的研究 总被引:2,自引:0,他引:2
齿叶黄皮是生长于广东省北部石灰岩山地的一种芸香科常绿小乔木,其叶富含精油,枝叶经水蒸汽蒸馏出油率为0.7%。精油经毛细管气相色谱、气相色谱/质谱联用、红外吸收光谱、核磁共振波谱等方法分析,确证含异大茴香脑(isoanethole)93.10%。异大茴香脑对霉菌有较强抑菌活性,并可通过异构化一步转变为大茴香脑。 相似文献
5.
6.
7.
Forced expression of the myogenic regulatory gene MyoD in many types of cultured cells initiates their conversion into skeletal muscle. It is not known, however, if MyoD expression serves to activate all or part of the skeletal muscle program in vivo during animal development, nor is it known how limiting the influences of cellular environment may be on the regulatory effects of MyoD. To begin to address these issues, we have produced transgenic mice which express MyoD in developing heart, where neither MyoD nor its three close relatives--myogenin, Myf-5, and MRF4/herculin/Myf-6--are normally expressed. The resulting gross phenotype in offspring from multiple, independent transgenic founders includes abnormal heart morphology and ultimately leads to death. At the molecular level, affected hearts exhibit activation of skeletal muscle-specific regulatory as well as structural genes. We conclude that MyoD is able to initiate the program that leads to skeletal muscle differentiation during mouse development, even in the presence of the ongoing cardiac differentiation program. Thus, targeted misexpression of this tissue-specific regulator during mammalian embryogenesis can activate, either directly or indirectly, a diverse set of genes normally restricted to a different cell lineage and a different cellular environment. 相似文献
8.
9.
c-myc inhibition of MyoD and myogenin-initiated myogenic differentiation. 总被引:19,自引:8,他引:11 下载免费PDF全文
In vertebrate development, a prominent feature of several cell lineages is the coupling of cell cycle regulation with terminal differentiation. We have investigated the basis of this relationship in the skeletal muscle lineage by studying the effects of the proliferation-associated regulator, c-myc, on the differentiation of MyoD-initiated myoblasts. Transient cotransfection assays in NIH 3T3 cells using MyoD and c-myc expression vectors demonstrated c-myc suppression of MyoD-initiated differentiation. A stable cell system was also developed in which MyoD expression was constitutive, while myc levels could be elevated conditionally. Induction of this conditional c-myc suppressed myogenesis effectively, even in the presence of MyoD. c-myc suppression also prevented up-regulation of a relative of MyoD, myogenin, which is normally expressed at the onset of differentiation in all muscle cell lines examined and may be essential for differentiation. Additional experiments tested whether failure to differentiate in the presence of myc could be overcome by providing myogenin ectopically. Cotransfection of c-myc with myogenin, MyoD, or a mixture of myogenin and MyoD showed that neither myogenin alone nor myogenin plus MyoD together could bypass the c-myc block. The effects of c-myc were further dissected by showing that c-myc can inhibit differentiation independently of Id, a negative regulator of muscle differentiation. These results lead us to propose that c-myc and Id constitute independent negative regulators of muscle differentiation, while myogenin and any of the other three related myogenic factors (MyoD, Myf-5, and MRF4/herculin/Myf-6) act as positive regulators. 相似文献
10.
本文利用两株针对HAFP分子不同抗原决定簇的单克隆抗体,鉴定HAFP酶解片断的抗原抗体反应性质,并同完整HAFP分子进行比较。结果表明,酶解片断上失去了一株单克隆抗体所对应的分子部份,完整保留着另一株单克隆抗体所识别的抗原决定簇,从而证实HAFP分子某些抗原结构之间具有可分割性。 相似文献