全文获取类型
收费全文 | 734篇 |
免费 | 77篇 |
出版年
2022年 | 4篇 |
2021年 | 14篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 21篇 |
2015年 | 26篇 |
2014年 | 33篇 |
2013年 | 52篇 |
2012年 | 69篇 |
2011年 | 37篇 |
2010年 | 44篇 |
2009年 | 30篇 |
2008年 | 46篇 |
2007年 | 60篇 |
2006年 | 45篇 |
2005年 | 39篇 |
2004年 | 34篇 |
2003年 | 37篇 |
2002年 | 44篇 |
2001年 | 10篇 |
2000年 | 3篇 |
1999年 | 15篇 |
1998年 | 5篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1967年 | 1篇 |
排序方式: 共有811条查询结果,搜索用时 446 毫秒
181.
Herz C Aumailley M Schulte C Schlötzer-Schrehardt U Bruckner-Tuderman L Has C 《The Journal of biological chemistry》2006,281(47):36082-36090
A novel family of focal adhesion proteins, the kindlins, is involved in attachment of the actin cytoskeleton to the plasma membrane and in integrin-mediated cellular processes. Deficiency of kindlin-1, as a result of loss-of-function mutations in the KIND1 gene, causes Kindler syndrome, an autosomal recessive genodermatosis characterized by skin blistering, progressive skin atrophy, photosensitivity and, occasionally, carcinogenesis. Here we characterized authentic and recombinantly expressed kindlin-1 and show that it is localized in basal epidermal keratinocytes in a polar fashion, close to the cell surface facing the basement membrane, in the areas between the hemidesmosomes. We identified two forms of kindlin-1 in keratinocytes, with apparent molecular masses of 78 and 74 kDa, corresponding to phosphorylated and desphosphorylated forms of the protein. In kindlin-1-deficient skin, basal keratinocytes show multiple abnormalities: cell polarity is lost, proliferation is strongly reduced, and several cells undergo apoptosis. In vitro, deficiency of kindlin-1 in keratinocytes leads to strongly reduced cell proliferation, decreased adhesion, undirected motility, and intense protrusion activity of the plasma membrane. Taken together, these results show that kindlin-1 plays a role in keratinocyte adhesion, polarization, proliferation, and migration. It is involved in organization and anchorage of the actin cytoskeleton to integrin-associated signaling platforms. 相似文献
182.
Nayak T Szewczyk E Oakley CE Osmani A Ukil L Murray SL Hynes MJ Osmani SA Oakley BR 《Genetics》2006,172(3):1557-1566
Aspergillus nidulans is an important experimental organism, and it is a model organism for the genus Aspergillus that includes serious pathogens as well as commercially important organisms. Gene targeting by homologous recombination during transformation is possible in A. nidulans, but the frequency of correct gene targeting is variable and often low. We have identified the A. nidulans homolog (nkuA) of the human KU70 gene that is essential for nonhomologous end joining of DNA in double-strand break repair. Deletion of nkuA (nkuA delta) greatly reduces the frequency of nonhomologous integration of transforming DNA fragments, leading to dramatically improved gene targeting. We have also developed heterologous markers that are selectable in A. nidulans but do not direct integration at any site in the A. nidulans genome. In combination, nkuA delta and the heterologous selectable markers make up a very efficient gene-targeting system. In experiments involving scores of genes, 90% or more of the transformants carried a single insertion of the transforming DNA at the correct site. The system works with linear and circular transforming molecules and it works for tagging genes with fluorescent moieties, replacing genes, and replacing promoters. This system is efficient enough to make genomewide gene-targeting projects feasible. 相似文献
183.
Meier JJ Kayed R Lin CY Gurlo T Haataja L Jayasinghe S Langen R Glabe CG Butler PC 《American journal of physiology. Endocrinology and metabolism》2006,291(6):E1317-E1324
Type 2 diabetes mellitus (T2DM) is characterized by an approximately 60% deficit in beta-cell mass, increased beta-cell apoptosis, and islet amyloid derived from islet amyloid polypeptide (IAPP). Human IAPP (hIAPP) forms oligomers, leading to either amyloid fibrils or toxic oligomers in an aqueous solution in vitro. Either application of hIAPP on or overexpression of hIAPP in cells induces apoptosis. It remains controversial whether the fibrils or smaller toxic oligomers induce beta-cell apoptosis. Rifampicin prevents hIAPP amyloid fibril formation and has been proposed as a potential target for prevention of T2DM. We examined the actions of rifampicin on hIAPP amyloid fibril and toxic oligomer formation as well as its ability to protect beta-cells from either application of hIAPP or endogenous overexpression of hIAPP (transgenic rats and adenovirus-transduced beta-cells). We report that rifampicin (Acocella G. Clin Pharmacokinet 3: 108-127, 1978) prevents hIAPP fibril formation, but not formation of toxic hIAPP oligomers (Bates G. Lancet 361: 1642-1644, 2003), and does not protect beta-cells from apoptosis induced by either overexpression or application of hIAPP. These data emphasize that toxic hIAPP oligomers, rather than hIAPP fibrils, initiate beta-cell apoptosis and that screening tools to identify inhibitors of amyloid fibril formation are likely to be less useful than those that identify inhibitors of toxic oligomer formation. Finally, rifampicin and related molecules do not appear to be useful as candidates for prevention of T2DM. 相似文献
184.
Jarho EM Venäläinen JI Juntunen J Yli-Kokko AL Vepsäläinen J Christiaans JA Forsberg MM Järvinen T Männistö PT Wallén EA 《Bioorganic & medicinal chemistry letters》2006,16(21):5590-5593
A series of ionizable prolyl oligopeptidase inhibitors were developed through the introduction of a pyridyl group to the P3 position of the prolyl oligopeptidase inhibitor structure. The study was performed on previously developed prolyl oligopeptidase inhibitors with proline mimetics at the P2 position. The 3-pyridyl group resulted in equipotent compounds as compared to the parent compounds. It was shown that the pyridyl group improves water solubility and, in combination with a 5(R)-tert-butyl-l-prolyl group at the P2 position, good lipophilicity can be achieved. 相似文献
185.
Satu Estlander Leena Nurminen Mikko Olin Mika Vinni Jukka Horppila 《Hydrobiologia》2009,620(1):109-120
The dynamics of crustacean zooplankton in the littoral and pelagic zones of four forest lakes having variable water qualities
(colour range 130–340 mg Pt l−1, Secchi depth 70–160 cm) were studied. The biomass of zooplankton was higher in the littoral zone than in the pelagic zone
only in the lake having the highest transparency. In the three other lakes, biomass was significantly higher in the pelagic
zone than in the littoral zone. In the two lakes with highest transparency, the littoral biomass of cladocerans significantly
followed the development of macrophyte vegetation, and cladoceran biomass reached the maximum value at the time of highest
macrophyte coverage. In lakes with lowest transparency, littoral zooplankton biomass developed independently of macrophyte
density and decreased when macrophyte beds were densest. The seasonal development of the littoral copepod biomass did not
follow the development of macrophytes in any of the lakes. The mean size of cladocerans in the pelagic zone decreased with
increasing Secchi depth of the lake, whereas in the littoral zone no such phenomenon was detected. Seasonally, when water
transparency increased temporarily in two of the lakes, the mean size of cladocerans in the pelagic zone decreased steeply.
For copepods, no relationship between water transparency and body size was observed. The results suggested that in humic lakes
the importance of the littoral zone as a refuge decreases with decreasing transparency of the water and that low water transparency
protects cladocerans from fish predation. All the observed between-lake differences could not be explained by fish predation,
but were probably attributed to the presence of chaoborid larvae with variable densities. Feeding efficiency of chaoborids
is not affected by visibility and thus they can obscure the relationship between water quality, fish density, and the structure
of crustacean zooplankton assemblages.
Handling editor: S. I. Dodson 相似文献
186.
Glycomics of bone marrow-derived mesenchymal stem cells can be used to evaluate their cellular differentiation stage 总被引:1,自引:0,他引:1
Annamari Heiskanen Tia Hirvonen Hanna Salo Ulla Impola Anne Olonen Anita Laitinen Sari Tiitinen Suvi Natunen Olli Aitio Halina Miller-Podraza Manfred Wuhrer André M. Deelder Jari Natunen Jarmo Laine Petri Lehenkari Juhani Saarinen Tero Satomaa Leena Valmu 《Glycoconjugate journal》2009,26(3):367-384
Human mesenchymal stem cells (MSCs) are adult multipotent progenitor cells. They hold an enormous therapeutic potential, but
at the moment there is little information on the properties of MSCs, including their surface structures. In the present study,
we analyzed the mesenchymal stem cell glycome by using mass spectrometric profiling as well as a panel of glycan binding proteins.
Structural verifications were obtained by nuclear magnetic resonance spectroscopy, mass spectrometric fragmentation, and glycosidase
digestions. The MSC glycome was compared to the glycome of corresponding osteogenically differentiated cells. More than one
hundred glycan signals were detected in mesenchymal stem cells and osteoblasts differentiated from them. The glycan profiles
of MSCs and osteoblasts were consistently different in biological replicates, indicating that stem cells and osteoblasts have
characteristic glycosylation features. Glycosylation features associated with MSCs rather than differentiated cells included
high-mannose type N-glycans, linear poly-N-acetyllactosamine chains and α2-3-sialylation. Mesenchymal stem cells expressed SSEA-4 and sialyl Lewis x epitopes. Characteristic
glycosylation features that appeared in differentiated osteoblasts included abundant sulfate ester modifications. The results
show that glycosylation analysis can be used to evaluate MSC differentiation state. 相似文献
187.
Ahonen LJ Kukkonen AM Pouwels J Bolton MA Jingle CD Stukenberg PT Kallio MJ 《Chromosoma》2009,118(1):71-84
Incenp is an essential mitotic protein that, together with Aurora B, Survivin, and Borealin, forms the core of the chromosomal
passenger protein complex (CPC). The CPC regulates various mitotic processes and functions to maintain genomic stability.
The proper subcellular localization of the CPC and its full catalytic activity require the presence of each core subunit in
the complex. We have investigated the mitotic tasks of the CPC using a function blocking antibody against Incenp microinjected
into cells at different mitotic phases. This method allowed temporal analysis of CPC functions without perturbation of complex
assembly or activity prior to injection. We have also studied the dynamic properties of Incenp and Aurora B using fusion protein
photobleaching. We found that in early mitotic cells, Incenp and Aurora B exhibit dynamic turnover at centromeres, which is
prevented by the anti-Incenp antibody. In these cells, the loss of centromeric CPC turnover is accompanied by forced mitotic
exit without the execution of cytokinesis. Introduction of anti-Incenp antibody into early anaphase cells causes abnormalities
in sister chromatid separation through defects in anaphase spindle functions. In summary, our data uncovers new mitotic roles
for the CPC in anaphase and proposes that CPC turnover at centromeres modulates spindle assembly checkpoint signaling.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
188.
Nakanishi S Vikstedt R Söderlund S Lee-Rueckert M Hiukka A Ehnholm C Muilu M Metso J Naukkarinen J Palotie L Kovanen PT Jauhiainen M Taskinen MR 《Journal of lipid research》2009,50(2):183-192
The main antiatherogenic function of HDL is to promote the efflux of cholesterol from peripheral cells and transport it to the liver for excretion in a process termed reverse cholesterol transport. The aim of this study was to evaluate the cholesterol efflux capacity in low- and high-HDL subjects by utilizing monocytes and serum from 18 low-HDL and 15 high-HDL subjects. Low and high HDL levels were defined, respectively, as HDL < or =10(th) and HDL > or =90(th) Finnish age/sex-specific percentile. Cholesterol efflux from [(3)H]cholesterol-oleate-acetyl-LDL-loaded monocyte-derived macrophages to standard apolipoprotein A-I (apoA-I), HDL(2), and serum was measured. In addition, cholesterol efflux from acetyl-LDL-loaded human THP-1 macrophages to individual sera (0.5%) derived from the study subjects was evaluated. Cholesterol efflux to apoA-I, HDL(2), and serum from macrophage foam cells derived from low- and high-HDL subjects was similar. The relative ABCA1 and ABCG1 mRNA expression levels in unloaded macrophages, as well as their protein levels in loaded macrophage foam cells, were similar in the two study groups. Cholesterol efflux from THP-1 foam cells to serum recovered from high-HDL subjects was slightly higher than that to serum from low-HDL subjects (P = 0.046). Cholesterol efflux from THP-1 macrophages to serum from study subjects correlated with serum apoB (P = 0.033), apoA-I (P = 0.004), apoA-II (P < 0.0001), and the percentage of apoA-I present in the form of prebeta-HDL (P = 0.0001). Our data reveal that macrophages isolated from either low- or high-HDL subjects display similar cholesterol efflux capacity to exogenous acceptors. However, sera from low-HDL subjects have poorer cholesterol acceptor ability as compared with sera from high-HDL subjects. 相似文献
189.
Tarmo Lipping Michael Rorarius Ville Jäntti Kari Annala Ari Mennander Rain Ferenets Tommi Toivonen Tim Toivo Alpo Värri Leena Korpinen 《Nonlinear biomedical physics》2009,3(1):5-10
Background
In this study, investigating the effects of mobile phone radiation on test animals, eleven pigs were anaesthetised to the level where burst-suppression pattern appears in the electroencephalogram (EEG). At this level of anaesthesia both human subjects and animals show high sensitivity to external stimuli which produce EEG bursts during suppression. The burst-suppression phenomenon represents a nonlinear control system, where low-amplitude EEG abruptly switches to very high amplitude bursts. This switching can be triggered by very minor stimuli and the phenomenon has been described as hypersensitivity. To test if also radio frequency (RF) stimulation can trigger this nonlinear control, the animals were exposed to pulse modulated signal of a GSM mobile phone at 890 MHz. In the first phase of the experiment electromagnetic field (EMF) stimulation was randomly switched on and off and the relation between EEG bursts and EMF stimulation onsets and endpoints were studied. In the second phase a continuous RF stimulation at 31 W/kg was applied for 10 minutes. The ECG, the EEG, and the subcutaneous temperature were recorded. 相似文献190.
Orathai Lim Worapot Suntornsuk Leena Suntornsuk 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2009,877(8-9):710-718
Enumeration of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus is a priority due to their importance in yogurt production. Capillary electrophoresis (CE) of both bacteria could be achieved in 7.2 min with a resolution of 3.2 in the background electrolyte (BGE) containing 4.5 mM Tris(hydroxymethyl) amminomethane (TRIS)–4.5 mM boric acid–0.1 mM ethylenediamine tetraacetate (EDTA) (TBE) buffer (pH 8.4) and 0.05% (v/v) polyethylene oxide (PEO), using a capillary of 47.5 cm (effective length) × 100 μm i.d., injection of 50 mbar × 3 s followed by ?5 kV × 120 s, a voltage and temperature of 20 kV and 25 °C, respectively. Appropriate amounts of PEO in the BGE, sample preparation (i.e. vortex) and introduction were key factors for their separation. A short hydrodynamic injection followed by applying reversed polarity voltage could compress the bacteria into narrow zones, which were detected as separated single peaks. Method linearity (r2 > 0.99), precision (%RSDs < 9.3%), recovery (%R = 91.7–106.7%) and limit of quantitation (1.0 × 106 colony forming unit per mL (CFU/mL)) were satisfactory. Results from the CE analysis of both bacteria in yogurt were not statistically different from those of the plate count method (P > 0.05). The CE method can be used as an alternative for quantitation of L. delbrueckii subsp. bulgaricus and S. thermophilus in yogurt since it was reliable, simple, cost and labor effective and rapid, allowing the analysis of 3 samples/h (comparing to 2d/sample by plate count method). 相似文献