全文获取类型
收费全文 | 8171篇 |
免费 | 769篇 |
国内免费 | 9篇 |
专业分类
8949篇 |
出版年
2022年 | 53篇 |
2021年 | 121篇 |
2020年 | 71篇 |
2019年 | 118篇 |
2018年 | 110篇 |
2017年 | 89篇 |
2016年 | 165篇 |
2015年 | 251篇 |
2014年 | 279篇 |
2013年 | 358篇 |
2012年 | 431篇 |
2011年 | 413篇 |
2010年 | 239篇 |
2009年 | 227篇 |
2008年 | 349篇 |
2007年 | 334篇 |
2006年 | 332篇 |
2005年 | 321篇 |
2004年 | 310篇 |
2003年 | 299篇 |
2002年 | 291篇 |
2001年 | 107篇 |
2000年 | 91篇 |
1999年 | 111篇 |
1998年 | 103篇 |
1997年 | 69篇 |
1996年 | 78篇 |
1995年 | 67篇 |
1994年 | 77篇 |
1993年 | 65篇 |
1992年 | 91篇 |
1991年 | 103篇 |
1990年 | 91篇 |
1989年 | 75篇 |
1988年 | 64篇 |
1987年 | 83篇 |
1986年 | 68篇 |
1985年 | 62篇 |
1984年 | 98篇 |
1983年 | 76篇 |
1982年 | 89篇 |
1981年 | 75篇 |
1980年 | 103篇 |
1979年 | 69篇 |
1978年 | 84篇 |
1977年 | 80篇 |
1976年 | 69篇 |
1975年 | 64篇 |
1974年 | 68篇 |
1973年 | 82篇 |
排序方式: 共有8949条查询结果,搜索用时 15 毫秒
1.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
2.
Inhibitory pathways are an essential component in the function of the neocortical microcircuitry. Despite the relatively small fraction of inhibitory neurons in the neocortex, these neurons are strongly activated due to their high connectivity rate and the intricate manner in which they interconnect with pyramidal cells (PCs). One prominent pathway is the frequency-dependent disynaptic inhibition (FDDI) formed between layer 5 PCs and mediated by Martinotti cells (MCs). Here, we show that simultaneous short bursts in four PCs are sufficient to exert FDDI in all neighboring PCs within the dimensions of a cortical column. This powerful inhibition is mediated by few interneurons, leading to strongly correlated membrane fluctuations and synchronous spiking between PCs simultaneously receiving FDDI. Somatic integration of such inhibition is independent and electrically isolated from monosynaptic excitation formed between the same PCs. FDDI is strongly shaped by I(h) in PC dendrites, which determines the effective integration time window for inhibitory and excitatory inputs. We propose a key disynaptic mechanism by which brief bursts generated by a few PCs can synchronize the activity in the pyramidal network. 相似文献
3.
4.
During an ultrastructural study of small-intestinal mucosa from a patient suffering from alpha-chain disease organisms were identified within the epithelial cytoplasm which showed the fine structural features of the coccidian group. Though coccidiosis is well recognized as causing a diarrhoeal and often lethal illness in animals it has been neglected as a cause of disease in man. Thus this finding may be significant and warrants further investigation into its possible role in the pathogenesis of alpha-chain disease. 相似文献
5.
6.
7.
8.
Steven S. Witkin Henry M. Schumaker 《Biochemical and biophysical research communications》1977,75(3):568-575
A particulate fraction of adult rat brain (sucrose buoyant density 1.24 gm/ml) catalyzed the incorporation of [3H]dTTP into an acid-insoluble product in an endogenously templated reaction sensitive to ribonuclease pretreatment. Upon fractionation, this activity was identified in the cerebellum, pons, frontal lobes and base. The DNA polymerase present in these brain fractions exhibited a strong preference for the synthetic template dT12–18·poly rA rather than dT12–18·poly dA; dT10 was completely inactive. Purification and equilibrium Cs2SO4 gradient centrifugation of the [3H]DNA product-endogenous template complex suggested that RNA was serving as primer for endogenous DNA synthesis. 相似文献
9.
10.
T Henry A Ferguson 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,85(2):491-496
Informative crosses have verified the genetic basis of a polymorphism at the Ldh-1 locus in brown trout and enzyme activity measurements indicate that the previously described polymorphism at this locus is best explained by a null allele. The LDH-1, LDH-2, LDH-3 and LDH-4 homotetrameric isozymes were purified and subjected to enzyme kinetic analysis. While LDH-1 and LDH-2 displayed catalytic equivalence, important kinetic differences were found between the LDH-3 and LDH-4 isozymes. 相似文献