全文获取类型
收费全文 | 2547篇 |
免费 | 269篇 |
国内免费 | 5篇 |
出版年
2021年 | 35篇 |
2020年 | 22篇 |
2019年 | 28篇 |
2018年 | 48篇 |
2017年 | 39篇 |
2016年 | 54篇 |
2015年 | 107篇 |
2014年 | 111篇 |
2013年 | 150篇 |
2012年 | 159篇 |
2011年 | 167篇 |
2010年 | 119篇 |
2009年 | 105篇 |
2008年 | 150篇 |
2007年 | 116篇 |
2006年 | 117篇 |
2005年 | 123篇 |
2004年 | 116篇 |
2003年 | 113篇 |
2002年 | 106篇 |
2001年 | 47篇 |
2000年 | 28篇 |
1999年 | 36篇 |
1998年 | 33篇 |
1997年 | 19篇 |
1995年 | 19篇 |
1994年 | 23篇 |
1993年 | 19篇 |
1992年 | 27篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 22篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 24篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1973年 | 13篇 |
1971年 | 12篇 |
1968年 | 13篇 |
排序方式: 共有2821条查询结果,搜索用时 46 毫秒
1.
2.
3.
The 30-Base-Pair Deletion in Chinese Variants of the Epstein-Barr Virus LMP1 Gene Is Not the Major Effector of Functional Differences between Variant LMP1 Genes in Human Lymphocytes 总被引:7,自引:3,他引:4 下载免费PDF全文
Rowena J. Johnson Maria Stack Sheila A. Hazlewood Matthew Jones Colin G. Blackmore Li-Fu Hu Martin Rowe 《Journal of virology》1998,72(5):4038-4048
One group of sequence variants of Epstein-Barr virus is characterized by a 10-amino-acid deletion within the CTAR-2 functional domain of the latent membrane protein, LMP1. A role for this deletion in enhancing the tumorigenicity of the viral oncogene in rodent fibroblasts was recently demonstrated. We examined the effect of this deletion upon LMP1 function in four human lymphoid cell lines by using three natural variants of LMP1: the prototype B95.8 gene and the CAO and AG876 genes, both of which have codons 343 to 352 of the B95.8-LMP1 deleted. These experiments revealed that LMP1-mediated upregulation of CD40 and CD54 was markedly impaired (by 60 to 90%) with CAO-LMP1 compared with B95.8-LMP1. In contrast, the function of AG876-LMP1 was indistinguishable from that of B95.8-LMP1 in two lines and was only slightly impaired in the other two lines. Activation of NF-κB by CAO-LMP1 was not impaired in any of the lines; rather, activation of an NF-κB reporter by CAO-LMP1 was consistently about twofold greater than the activation with B95.8- or AG876-LMP1. Therefore, while the CAO-LMP1 is functionally distinct from the prototype B95.8-LMP1 in human lymphocytes, the 10-amino-acid deletion appears not to be directly responsible. This conclusion was confirmed by using a B95.8-LMP1 mutant with codons 343 to 352 deleted and chimerae of CAO- and B95.8-LMP1 in which the CTAR-2 domains of these genes were exchanged. Sequences outside the CTAR-2 domain were implicated in the distinct functional characteristics of CAO-LMP1 in human lymphoid cells. 相似文献
4.
Glycosaminoglycans (GAG) are known to participate in central nervous system
processes such as development, cell migration, and neurite outgrowth, but
little is known with respect to their regulation through soluble
neurotrophic factors. In the present study, we have addressed this issue
using cell culture models of three distinct cell populations derived from
young rat retinas, namely, purified M uller glia, pigmented epithelium, and
neurons respectively. Cultures were maintained in chemically defined media
in the presence or absence of either basic fibroblast or epidermal growth
factor. In control glial and epithelial cultures, hyaluronic acid dominated
the soluble GAG pool, with lesser contributions from dermatan sulfate,
chondroitin sulfate, and heparan sulfate (in decreasing order). Retinal
neuronal GAG were almost exclusively chondroitin sulfate (approximately
90%). Treatment of glial and epithelial cultures with either factor led to
dose-dependent increases in especially hyaluronic acid synthesis (a maximum
6-fold increase relative to control levels), with smaller but consistent
changes in chondroitin sulfate. Similar treatment of retinal neurons did
not lead to any changes in GAG synthesis. These data indicate that glia and
pigment epithelia are the principal sources of GAG components in retina at
least in vitro, and that endogenous neurotrophic growth factors can greatly
modify GAG synthesis in these two retinal cell populations. Such data
suggest that a delicate balance may exist between growth factor
availability and glycoconjugate metabolism in vivo, participating in normal
or pathological states of the retina.
相似文献
5.
6.
7.
Sheila M Bird 《BMJ (Clinical research ed.)》2004,329(7470):856-857
8.
9.
Properties of monoclonal antibodies specific for determinants of a protein antigen, myoglobin 总被引:8,自引:0,他引:8
J A Berzofsky G Hicks J Fedorko J Minna 《The Journal of biological chemistry》1980,255(23):11188-11191
Monoclonal hybridoma antibodies specific for the protein antigen sperm whale myoglobin were produced using hyperimmune spleen cells from mice with the genetic trait of high responsiveness to myoglobin. Antibodies from the several clones tested were found to produce linear Scatchard plots, as predicted for homogeneous antibodies, and to possess high affinities for the immunogen (KA congruent to 10(9) M-1). None of the monoclonal antibodies tested reacted with either fragment (1-55) or fragment (132-153) of sperm whale myoglobin. Competitive binding assays using human and horse myoglobins suggested that several of these monoclonal antibodies, which can readily distinguish these myoglobins, recognize different antigenic determinants on the myoglobin molecule. Studies using additional myoglobin sequence variants as competitors should be able to more closely define these antigenic determinants. 相似文献
10.