全文获取类型
收费全文 | 3800篇 |
免费 | 292篇 |
专业分类
4092篇 |
出版年
2022年 | 19篇 |
2021年 | 58篇 |
2020年 | 28篇 |
2019年 | 41篇 |
2018年 | 49篇 |
2017年 | 55篇 |
2016年 | 91篇 |
2015年 | 114篇 |
2014年 | 128篇 |
2013年 | 214篇 |
2012年 | 218篇 |
2011年 | 220篇 |
2010年 | 115篇 |
2009年 | 102篇 |
2008年 | 170篇 |
2007年 | 196篇 |
2006年 | 183篇 |
2005年 | 158篇 |
2004年 | 140篇 |
2003年 | 150篇 |
2002年 | 136篇 |
2001年 | 118篇 |
2000年 | 128篇 |
1999年 | 96篇 |
1998年 | 52篇 |
1997年 | 49篇 |
1996年 | 43篇 |
1995年 | 39篇 |
1994年 | 35篇 |
1993年 | 33篇 |
1992年 | 87篇 |
1991年 | 70篇 |
1990年 | 67篇 |
1989年 | 61篇 |
1988年 | 45篇 |
1987年 | 50篇 |
1986年 | 45篇 |
1985年 | 40篇 |
1984年 | 43篇 |
1983年 | 47篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1979年 | 33篇 |
1978年 | 18篇 |
1975年 | 25篇 |
1974年 | 20篇 |
1973年 | 19篇 |
1971年 | 17篇 |
1970年 | 21篇 |
1967年 | 20篇 |
排序方式: 共有4092条查询结果,搜索用时 15 毫秒
31.
32.
33.
This paper reports the properties of human hemoglobin covalently bound to Sepharose 4B both in 'high-affinity' and 'low-affinity' conformations. The results suggest that the coupling reaction is strongly affected by the conformational changes linked to oxygenation of the protein. The rate and the extent of the reaction are different for the oxy and deoxyderivatives, probably due to the change in reactivity of the amino groups in the liganded and unliganded tetramer. The data on the equilibrium which is established between matrix-bound and soluble subunits, measured by the 'subunit-exchange chromatography', indicate that the system displays a minimal heterogeneity when hemoglobin is coupled to the gel in the deoxy state at intermediate protein concentration and pH 8. Maxtrix-bound hemoglobin is characterized by a higher oxygen affinity and by decreased homotropic and heterotropic interactions with respect to hemoglobin in solution, but the changes depend strongly on the conditions used in the coupling procedure. 相似文献
34.
The isolated rabbit heart was perfused with tritium-labelled adenosine or uridine at constant concentration (respectively 10 and 2 micrometer) and specific activity. The transfer rates of the precursors into free nucleotides were obtained by calculating the uptake of isotope into the products. The rates of phosphorylation of the nucleotides were estimated by following the incorporation of 32PO4 3- into the alpha phosphate groups. The results obtained with the two isotopes show that the rate of labelling of the alpha phosphate groups is a good estimate of the turnover of nucleotides when the mechanism of synthesis involves phosphorylation of a riboside. 相似文献
35.
36.
37.
Ribonucleoside diphosphate reductase activity is determined in centrifuged homogenates by following the conversion of cytosine ribonucleotide to cytosine deoxyribonucleotide. The enzymatic reaction is measured by monitoring the radioactivity of the reaction products separated by thin layer chromatography on PEI-cellulose plates. The method is rapid and permits the simultaneous processing of multiple samples. 相似文献
38.
Elke EM Brouwers Alwin DR Huitema Jos H Beijnen Jan HM Schellens 《BMC clinical pharmacology》2008,8(1):7
Background
The aim of this study was to evaluate long-term platinum retention in patients treated with cisplatin and oxaliplatin. 相似文献39.
G Berton L Zeni M A Cassatella F Rossi 《Biochemical and biophysical research communications》1986,138(3):1276-1282
The oxidative metabolism of human neutrophils has been studied after incubation of the cells with recombinant interferon-y. Neutrophils incubated for 2-4 hours with 2-50 U/ml recombinant interferon-y undergo a higher respiratory burst measured both as Oz consumption and Oz- production when stimulated with formyl-methionyl-leucyl-phenylalanine, Concanavalin A or phorbol myristate acetate. The potentiating effect of interferon-y requires more than one hour of incubation, is optimal at 20-50 U/ml and depends on the presence of serum in the incubation medium. The interferon effect depends on new protein synthesis. Cycloheximide at doses which do not alter the respiratory response of normal cells completely prevents the potentiating effect of interferon. 相似文献
40.
Synaptic destabilization by neuronal Nogo-A 总被引:1,自引:0,他引:1
Aloy EM Weinmann O Pot C Kasper H Dodd DA Rülicke T Rossi F Schwab ME 《Brain Cell Biology》2006,35(2-3):137-157
Formation and maintenance of a neuronal network is based on a balance between plasticity and stability of synaptic connections.
Several molecules have been found to regulate the maintenance of excitatory synapses but nothing is known about the molecular
mechanisms involved in synaptic stabilization versus disassembly at inhibitory synapses. Here, we demonstrate that Nogo-A,
which is well known to be present in myelin and inhibit growth in the adult CNS, is present in inhibitory presynaptic terminals
in cerebellar Purkinje cells at the time of Purkinje cell-Deep Cerebellar Nuclei (DCN) inhibitory synapse formation and is
then downregulated during synapse maturation. We addressed the role of neuronal Nogo-A in synapse maturation by generating
several mouse lines overexpressing Nogo-A, starting at postnatal ages and throughout adult life, specifically in cerebellar
Purkinje cells and their terminals. The overexpression of Nogo-A induced a progressive disassembly, retraction and loss of
the inhibitory Purkinje cell terminals. This led to deficits in motor learning and coordination in the transgenic mice. Prior
to synapse disassembly, the overexpression of neuronal Nogo-A led to the downregulation of the synaptic scaffold proteins
spectrin, spectrin-E and β-catenin in the postsynaptic neurons. Our data suggest that neuronal Nogo-A might play a role in
the maintenance of inhibitory synapses by modulating the expression of synaptic anchoring molecules.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献