全文获取类型
收费全文 | 1682篇 |
免费 | 108篇 |
国内免费 | 38篇 |
专业分类
1828篇 |
出版年
2023年 | 16篇 |
2022年 | 37篇 |
2021年 | 41篇 |
2020年 | 28篇 |
2019年 | 43篇 |
2018年 | 35篇 |
2017年 | 26篇 |
2016年 | 57篇 |
2015年 | 82篇 |
2014年 | 111篇 |
2013年 | 127篇 |
2012年 | 140篇 |
2011年 | 134篇 |
2010年 | 88篇 |
2009年 | 54篇 |
2008年 | 88篇 |
2007年 | 68篇 |
2006年 | 67篇 |
2005年 | 56篇 |
2004年 | 52篇 |
2003年 | 54篇 |
2002年 | 47篇 |
2001年 | 48篇 |
2000年 | 35篇 |
1999年 | 27篇 |
1998年 | 6篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 22篇 |
1991年 | 15篇 |
1990年 | 21篇 |
1989年 | 13篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1981年 | 7篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有1828条查询结果,搜索用时 9 毫秒
151.
Chieh-Sen Chuang Hong-Lin Su Fu-Chou Cheng Shan-hui Hsu Chi-Fen Chuang Chin-San Liu 《Journal of biomedical science》2010,17(1):9
Although gait change is considered a useful indicator of severity in animal models of Parkinson's disease, systematic and
extensive gait analysis in animal models of neurological deficits is not well established. The CatWalk-assisted automated
gait analysis system provides a comprehensive way to assess a number of dynamic and static gait parameters simultaneously.
In this study, we used the Catwalk system to investigate changes in gait parameters in adult rats with unilateral 6-OHDA-induced
lesions and the rescue effect of dopaminergic neuron transplantation on gait function. Four weeks after 6-OHDA injection,
the intensity and maximal area of contact were significantly decreased in the affected paws and the swing speed significantly
decreased in all four paws. The relative distance between the hind paws also increased, suggesting that animals with unilateral
6-OHDA-induced lesions required all four paws to compensate for loss of balance function. At 8 weeks post-transplantation,
engrafted dopaminergic neurons expressed tyrosine hydroxylase. In addition, the intensity, contact area, and swing speed of
the four limbs increased and the distance between the hind paws decreased. Partial recovery of methamphetamine-induced rotational
response was also noted. 相似文献
152.
Yi-Hsun Chang Chau-Zen Wang Chien-Chih Chiu Lea-Yea Chuang Chi-Ching Hwang 《Biochimica et Biophysica Acta - Proteins and Proteomics》2010,1804(1):235-241
3α-Hydroxysteroid dehydrogenase/carbonyl reductase reversely catalyzes the oxidation of androsterone with NAD+ to form androstanedione and NADH. In this study, we investigated the function of active site residues N86, Y155, and K159 in NADH binding and catalysis in the reduction of androstanedione, using site-directed mutagenesis, steady-state kinetics, fluorescence quenching, and anisotropy measurements. The N86A, Y155F, and K159A mutant enzymes decreased the catalytic constant by 37- to 220-fold and increased the dissociation constant by 3- to 75-fold, respectively. Binding of NADH with wild-type and mutant enzymes caused different levels of fluorescence resonance energy transfer, implying a different orientation of nicotinamide ring versus W173. In addition, the enzyme-bound NADH decreased the fluorescence anisotropy value in the order WT > N86A > Y155F > K159A, indicating an increase in the mobility of the bound NADH for the mutants. Data suggest that hydrogen bonding with the hydroxyl group of nicotinamide ribose by K159 and Y155 is important to maintain the orientation of NADH and contributes greatly to the transition-state binding energy to facilitate the catalysis. N86 is important for stabilizing the position of K159. Substitution of alanine for N86 has a minor effect on NADH binding through K159, resulting in a slight increase in the mobility of the bound NADH and decreases in affinity and catalytic constant. 相似文献
153.
Environmental variables can significantly influence the folding and stability of a protein molecule. In the present study,
the biophysical properties of a truncated Bacillus sp. TS-23 α-amylase (BACΔNC) were characterized in detail by glutaraldehyde cross-linking, analytical ultracentrifugation,
and various spectroscopic techniques. With cross-linking experiment and analytical ultracentrifuge, we demonstrated that the
oligomeric state of BACΔNC in solution is monomeric. Far-UV circular dichroism analysis revealed that the secondary structures
of BACΔNC were significantly altered in the presence of various metal ions and SDS, whereas acetone and ethanol had no detrimental
effect on folding of the enzyme. BACΔNC was inactive and unstable at extreme pH conditions. Thermal unfolding of the enzyme
was found to be highly irreversible. The native enzyme started to unfold beyond ~0.2 M guanidine hydrochloride (GdnHCl) and
reached an unfolded intermediate, [GdnHCl]0.5, N–U, at 1.14 M. BACΔNC was active at the concentrations of urea below 6 M, but it experienced an irreversible unfolding by >8 M
denaturant. Taken together, this work lays a foundation for the future structural studies with Bacillus sp. TS-23 α-amylase, a typical member of glycoside hydrolases family 13. 相似文献
154.
Although cockroaches are known to produce allergens that can cause IgE-mediated hypersensitivity reactions, including perennial rhinitis and asthma, the various cockroach allergens have not yet been fully studied. Many proteins from the German cockroach show high IgE reactivity, but have never been comprehensively characterized. To identify these potential allergens, proteins were separated by 2-DE and IgE-binding proteins were analyzed by nanoLC-MS/MS or N-terminal sequencing analysis. Using a combination of proteomic techniques and bioinformatic allergen database analysis, we identified a total of ten new B. germanica IgE-binding proteins. Of these, aldolase, arginine kinase, enolase, Hsp70, triosephosphate isomerase, and vitellogenin have been reported as allergens in species other than B. germanica. Analysis of the Food Allergy Research and Resource Program allergen database indicated that arginine kinase, enolase, and triosephosphate isomerase showed significant potential cross-reactivity with other related allergens. This study revealed that vitellogenin is an important novel B. germanica allergen. Personalized profiling and reactivity of IgE Abs against the panel of IgE-binding proteins varied between cockroach-allergic individuals. These findings make it possible to monitor the individual IgE reactivity profile of each patient and facilitate personalized immunotherapies for German cockroach allergy disorders. 相似文献
155.
Shae B. Padrick Jacinta L. Chuang David T. Chuang Michael V. Norgard Chad A. Brautigam 《Analytical biochemistry》2010,407(1):89-23488
Determination of the stoichiometry of macromolecular assemblies is fundamental to an understanding of how they function. Many different biophysical methodologies may be used to determine stoichiometry. In the past, both sedimentation equilibrium and sedimentation velocity analytical ultracentrifugation have been employed to determine component stoichiometries. Recently, a method of globally analyzing multisignal sedimentation velocity data was introduced by Schuck and coworkers. This global analysis removes some of the experimental inconveniences and inaccuracies that could occur in the previously used strategies. This method uses spectral differences between the macromolecular components to decompose the well-known c(s) distribution into component distributions ck(s); that is, each component k has its own ck(s) distribution. Integration of these distributions allows the calculation of the populations of each component in cosedimenting complexes, yielding their stoichiometry. In our laboratories, we have used this method extensively to determine the component stoichiometries of several protein-protein complexes involved in cytoskeletal remodeling, sugar metabolism, and host-pathogen interactions. The overall method is described in detail in this work, as are experimental examples and caveats. 相似文献
156.
Shih-Kuang Yang Yu-Chao Wang Chun-Cheih Chao Yung-Jen Chuang Chung-Yu Lan Bor-Sen Chen 《BMC medical genomics》2010,3(1):19
Background
Development in systems biology research has accelerated in recent years, and the reconstructions for molecular networks can provide a global view to enable in-depth investigation on numerous system properties in biology. However, we still lack a systematic approach to reconstruct the dynamic protein-protein association networks at different time stages from high-throughput data to further analyze the possible cross-talks among different signaling/regulatory pathways.Methods
In this study we integrated protein-protein interactions from different databases to construct the rough protein-protein association networks (PPANs) during TNFα-induced inflammation. Next, the gene expression profiles of TNFα-induced HUVEC and a stochastic dynamic model were used to rebuild the significant PPANs at different time stages, reflecting the development and progression of endothelium inflammatory responses. A new cross-talk ranking method was used to evaluate the potential core elements in the related signaling pathways of toll-like receptor 4 (TLR-4) as well as receptors for tumor necrosis factor (TNF-R) and interleukin-1 (IL-1R).Results
The highly ranked cross-talks which are functionally relevant to the TNFα pathway were identified. A bow-tie structure was extracted from these cross-talk pathways, suggesting the robustness of network structure, the coordination of signal transduction and feedback control for efficient inflammatory responses to different stimuli. Further, several characteristics of signal transduction and feedback control were analyzed.Conclusions
A systematic approach based on a stochastic dynamic model is proposed to generate insight into the underlying defense mechanisms of inflammation via the construction of corresponding signaling networks upon specific stimuli. In addition, this systematic approach can be applied to other signaling networks under different conditions in different species. The algorithm and method proposed in this study could expedite prospective systems biology research when better experimental techniques for protein expression detection and microarray data with multiple sampling points become available in the future.157.
April L Ellis Wensheng Pan Guang Yang Kim Jones Christine Chuang John M Whitelock Arthur A DeCarlo 《BMC biotechnology》2010,10(1):66
Background
Heparan sulfate glycosaminoglycans are diverse components of certain proteoglycans and are known to interact with growth factors as a co-receptor necessary to induce signalling and growth factor activity. In this report we characterize heterogeneously glycosylated recombinant human perlecan domain 1 (HSPG2 abbreviated as rhPln.D1) synthesized in either HEK 293 cells or HUVECs by transient gene delivery using either adenoviral or expression plasmid technology. 相似文献159.
Phosphatidylinositol 3-kinase/Akt activation by integrin-tumor matrix interaction suppresses Fas-mediated apoptosis in T cells 总被引:1,自引:0,他引:1
Su CC Lin YP Cheng YJ Huang JY Chuang WJ Shan YS Yang BC 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(7):4589-4597
It has recently become apparent that the microenvironment made up of the extracellular matrix may affect cell signaling. In this study, we evaluated Fas-triggered apoptosis in T cells in contact with tumor cells, which resembles the cell-to-cell interactions found in tumor regions. Jurkat cells were less susceptible to the Fas-mediated apoptosis when cocultured with U118, HeLa, A549, and Huh-7 tumor cells. This was indicated by less plasma membrane alteration, an amelioration of the loss of mitochondria membrane potential, a decrease in caspase-8 and caspase-3 activation, a decrease in DNA fragmentation factor-45/35 cleavage, and a reduction in the breakage of DNA when compared with Jurkat cells cultured alone. In contrast, the tumor cell lines MCF-7 and HepG2 produced no such protective effect. This protective event was independent of the expression of Fas ligand on the tumor cells. Interrupting the beta integrins-matrix interaction diminished the coculture effect. In Jurkat cells, cell matrix contact reduced the assembly of the Fas death-inducing signaling complex and Bcl-x(L) cleavage, but enhanced the phosphorylation of ERK1/2, p38 MAPK, and Akt. Only PI3K inhibitor, but not kinase inhibitors for MEK, ERK1/2, p38 MAPK, JNK, protein kinase C, and protein kinase A, completely abolished this tumor cell contact-associated protection and in parallel restored Fas-induced Bcl-x(L) cleavage as well as decreasing the phosphorylation of Bad at serine 136. Together, our results indicate that stimulation of the beta integrin signal of T cells by contact with tumor cells may trigger a novel protective signaling through the PI3K/Akt pathway of T cells against Fas-mediated apoptosis. 相似文献
160.
The group I metabotropic glutamate receptor agonist (S)-3,5-dihydroxyphenylglycine (DHPG) elicited two phases of synchronized neuronal (epileptiform) discharges in hippocampal slices: an initial phase of short duration discharges followed by a phase of prolonged discharges. We assessed the involvement of transient receptor potential canonical (TRPC) channels in these responses. Pre-treatment of hippocampal slices with TRPC channel blockers, 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride (SKF96365) or 2-aminoethoxydiphenyl borate, did not affect the short epileptiform discharges but blocked the prolonged epileptiform discharges. SKF96365 suppressed ongoing DHPG-induced prolonged epileptiform discharges. Western blot analysis showed that the total TRPC4 or TRPC5 proteins in hippocampal slices were unchanged following DHPG. DHPG increased TRPC4 and TRPC5 in the cytoplasmic compartment and decreased these proteins in the plasma membrane. Translocation of TRPC4 and TRPC5 was suppressed when the epileptiform discharges were blocked by ionotropic glutamate receptor blockers. Translocation of TRPC4 and TRPC5 was also prevented in slices from phospholipase C (PLC) beta1 knockout mice, even when synchronized discharges were elicited by the convulsant 4-aminopyridine. The results suggest that TRPC channels are involved in generating DHPG-induced prolonged epileptiform discharges. This function of TRPC channels is associated with a neuronal activity- and PLCbeta1-dependent translocation of TRPC4 and TRPC5 proteins from the plasmalemma to the cytoplasmic compartment. 相似文献