全文获取类型
收费全文 | 1235篇 |
免费 | 58篇 |
国内免费 | 1篇 |
专业分类
1294篇 |
出版年
2023年 | 8篇 |
2022年 | 19篇 |
2021年 | 45篇 |
2020年 | 21篇 |
2019年 | 23篇 |
2018年 | 26篇 |
2017年 | 23篇 |
2016年 | 36篇 |
2015年 | 75篇 |
2014年 | 81篇 |
2013年 | 90篇 |
2012年 | 97篇 |
2011年 | 132篇 |
2010年 | 78篇 |
2009年 | 59篇 |
2008年 | 89篇 |
2007年 | 90篇 |
2006年 | 65篇 |
2005年 | 48篇 |
2004年 | 47篇 |
2003年 | 50篇 |
2002年 | 27篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有1294条查询结果,搜索用时 0 毫秒
51.
The technique of differential pulse polarography is shown here to be applicable to the monitoring directly the biosorption
of metal ions from solution by live bacteria from mixed metal solutions. Biosorption of Cd(II), Zn(II) and Ni(II) by P. cepacia was followed using data obtained at the potential which is characteristic of the metal ion in the absence and presence of
cells. Hepes buffer (pH 7.4, 50 mM) was used as a supporting electrolyte in the polarographic chamber and metal ion peaks
in the presence of cells of lower amplitude were obtained due to metal-binding by the cells. Well defined polarographic peaks
were obtained in experiments involving mixtures of metal ions of Cd(II)-Zn(II), Cu(II)-Zn(II), Cu(II)-Cd(II) and Cd(II)-Ni(II).
Biosorption of Cd(II), Zn(II) increased with solution pH. The method was also tested as a rapid technique for assessing removal
of metal ions by live bacteria and the ability of the polarographic technique in measuring biosorption of metal ions from
mixed metal solutions is demonstrated. Cu(II) was preferentially bound and removal of metals was in the order Cu(II) > Ni(II)
> Zn(II), Cd(II) by intact cells of P. cepacia.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
52.
Detecting and quantifying colocalization of cell surface molecules by single particle fluorescence imaging 下载免费PDF全文
Single particle fluorescence imaging (SPFI) uses the high sensitivity of fluorescence to visualize individual molecules that have been selectively labeled with small fluorescent particles. The positions of particles are determined by fitting the intensity profile of their images to a 2-D Gaussian function. We have exploited the positional information obtained from SPFI to develop a method for detecting colocalization of cell surface molecules. This involves labeling two different molecules with different colored fluorophores and determining their positions separately by dual wavelength imaging. The images are analyzed to quantify the overlap of the particle images and hence determine the extent of colocalization of the labeled molecules. Simulated images and experiments with a model system are used to investigate the extent to which colocalization occurs from chance proximity of randomly distributed molecules. A method of correcting for positional shifts that result from chromatic aberration is presented. The technique provides quantification of the extent of colocalization and can detect whether colocalized molecules occur singly or in clusters. We have obtained preliminary data for colocalization of molecules on intact cells. Cells often exhibit particulate autofluorescence that can interfere with the measurements; a method for overcoming this problem by triple wavelength imaging is described. 相似文献
53.
Minas Papadopoulos Berthold Nock Theodosia Maina Ioannis Pirmettis Catherine Raptopoulou Anastasios Tasiopoulos Anastasios Troganis Themistoklis Kabanos Aris Terzis Efstratios Chiotellis 《Journal of biological inorganic chemistry》2001,6(2):159-165
Novel oxorhenium and oxotechnetium complexes based on the tetradentate 1-(2-hydroxybenzamido)-2-(pyridinecarboxamido)benzene, H3L, ligand have been synthesized and characterized herein. Thus, by reacting equimolar quantities of the triply deprotonated ligand L3- with the suitable MO3+ precursor, the following neutral MOL complexes could be easily produced following similar synthetic routes: M = Re (1), M = 99gTc (2), and M = 99mTc (3). Complexes 1 and 2, prepared in macroscopic amounts, were chemically characterized and their structure determined by single-crystal X-ray analysis. They are isostructural metal chelates, adopting a distorted square pyramidal geometry around the metal. The N3O donor atom set of the tetradentate ligand defines the basal plane and the oxygen atom of the M = O core occupies the apex of the pyramid. Complex 3 forms quantitatively at tracer level by mixing the H3L ligand with Na99mTcO4 generator eluate in aqueous alkaline media and using tin chloride as reductant in the presence of citrate. Its structure was established by chromatographic comparison with prototypic complexes 1 and 2 using high-performance liquid chromatographic techniques. When challenged with excess glutathione in vitro, complex 3 is rapidly converted to hydrophilic unidentified metal species. Tissue distribution data after administration of complex 3 in vivo revealed a significant uptake and retention of this compound in brain tissue. 相似文献
54.
55.
Bacterial synergism or antagonism in a gel cassette system 总被引:1,自引:0,他引:1
The growth and the metabolic activity of Shewanella putrfaciens, Brochothrix thermosphacta, and Pseudomonas sp., when cultured individually or in all possible combinations in gel cassettes system supplemented with 0.1% glucose at 5 degrees C, were investigated. The overall outcome was that the coexistence of the above-mentioned microorganisms affected not only each growth rate but also their type of metabolic end products compared to the control cultures. These effects were varied and depended on the selection of the combination of the tested bacteria. For example, the growth of Pseudomonas sp. strains cocultured with either B. thermosphacta or S. putrefaciens strains resulted in different effects: a promoting one for the first and an inhibitory one for the second. Moreover, the production of formic acid and two unidentified organic acids (peaks a and b) was characteristic in all cases in which S. putrefaciens was cultured. 相似文献
56.
The application of Fourier Transform near infrared spectroscopy (FT-NIRS) to near real-time monitoring of polysaccharide and biomass concentration was investigated using a gellan-producing strain of Sphingomonas paucimobilis grown in a stirred tank reactor. Successful models for both biomass and gellan were constructed despite the physichochemical complexity of the viscous process fluid. Modelling of biomass proved more challenging than for gellan, partly because of the low range of biomass concentration but a model with a good correlation coefficient (0.94) was formulated based on second derivative spectra. The gellan model was highly satisfactory, with an excellent correlation coefficient (0.98), again based on second derivative spectra. No sample pre-treatment was required and all spectral scanning was carried out on whole broth. Additionally, both models should be robust in practice since both were formulated using low numbers of factors. Thus, the near real time simultaneous monitoring of gellan and biomass in this highly complex matrix using FT-NIRS potentially opens the way to greatly improved process control strategies. 相似文献
57.
Iliopoulos I Enright AJ Poullet P Ouzounis CA 《Comparative and Functional Genomics》2003,4(3):337-341
We have previously shown that the detection of gene fusion events can contribute towards the elucidation of functional associations of proteins within entire genomes. Here we have analysed the entire genome of Drosophila melanogaster using fusion analysis and two additional constraints that improve the reliability of the predictions, viz. low sequence similarity and low degree of paralogy of the component proteins involved in a fusion event. Imposing these constraints, the total number of unique component pairs is reduced from 18 654 to a mere 220 cases, which are expected to represent some of the most reliably detected functionally associated proteins. Using additional information from sequence databases, we have been able to detect pairs of functionally associated proteins with important functions in cellular and developmental pathways, such as spermatogenesis and programmed cell death. 相似文献
58.
Pantos C Malliopoulou V Paizis I Moraitis P Mourouzis I Tzeis S Karamanoli E Cokkinos DD Carageorgiou H Varonos D Cokkinos DV 《Molecular and cellular biochemistry》2003,242(1-2):173-180
It has been recently shown that long-term thyroxine administration increases the tolerance of the heart to ischaemia. The present study investigated whether thyroxine induced cardioprotection involves alterations in the pattern of p38 mitogen activated protein kinase (p38MAPK) and c-Jun NH2-terminal kinases (JNKs) activation during ischaemia-reperfusion. L-thyroxine (T4) was administered in Wistar rats (25 g/100 g/day, subcutaneously) for 2 weeks (THYR), while normal animals served as controls (NORM). NORM and THYR isolated rat hearts were perfused in Langendorff mode and subjected to 10 or 20 min of zero-flow global ischaemia only and also to 20 min of ischaemia followed by 10, 20 or 45 min of reperfusion. Postischaemic recovery of left ventricular developed pressure at 45 min of reperfusion was expressed as % of the initial value. Activation of p38 MAPK and JNKs was assessed at the different times of the experimental setting by standard Western blotting techniques using a dual phospho p38MAPK and phospho JNKs (p46/p54) antibodies. Activation of p38 MAPK was significantly attenuated during ischaemia and reperfusion in thyroxine treated hearts compared to normal hearts. JNKs were found to be activated only during the reperfusion period. The levels of phospho JNKs were found to be lower in thyroxine treated hearts as compared to untreated hearts, though not at a statistically significant level. Postischaemic functional recovery was higher in THYR as compared to NORM, p < 0.05. In summary, in hearts pretreated with thyroxine, p38 MAPK was attenuated during ischaemia and at reperfusion and this was associated with improved postischaemic recovery of function. 相似文献
59.
Michel C Battaglia-Brunet F Minh CT Bruschi M Ignatiadis I 《Biosensors & bioelectronics》2003,19(4):345-352
The chromate reductase activity of cytochrome c(3) (Cyt c(3), M(r) 13000), isolated from the sulfate-reducing bacterium Desulfomicrobium norvegicum, was used to develop an amperometric biosensor to measure chromate (CrO(4)(2-)) bioavailability. The performance of various biosensor configurations for qualitative and quantitative determination of Cr(VI) was studied. Biosensor properties depend on the technique used to immobilize the enzyme on the electrode (glassy carbon electrode). Immobilization of Cyt c(3) by entrapment in poly 3,4-ethylenedioxythiophene films denatured the enzyme, while application of an adsorption technique did not affect enzyme activity but the detection range was limited. The best results were obtained with dialysis membranes, which allowed the determination of Cr(VI) from 0.20 to 6.84 mg l(-1) (3.85-132 microM) with a sensitivity of 35 nA mg(-1) l (1.82 nA microM(-1)). No interference was observed with As(V), As(III) and Fe(III). Only a small amount of Cyt c(3) (372 ng of protein) was needed for this biosensor. 相似文献
60.
Dermitzaki E Tsatsanis C Charalampopoulos I Androulidaki A Alexaki VI Castanas E Gravanis A Margioris AN 《Biochemical and biophysical research communications》2005,327(3):828-836
Protein kinase C (PKC) has recently emerged as mediator of corticotropin-releasing hormone (CRH) effects. Aim of the present study was to study the effects of CRH on each PKC isoenzyme. As a model we have used the PC12 rat pheochromocytoma cell line, expressing the CRH type 1 receptor (CRHR1). Our data were as follows: (a) CRH-induced rapid phosphorylation of conventional PKCalpha and PKCbeta, accompanied by parallel increase of their concentration within nucleus. (b) CRH suppressed the phosphorylation of novel PKCdelta and PKCtheta;, which remained in the cytosol. (c) CRH-induced transient phosphorylation of atypical PKClambda and had no effect on PKCmu. (d) The effect of CRH on each PKC isoenzyme was blocked by a CRHR1 antagonist. (e) Blockade of conventional PKC phosphorylation inhibited CRH-induced calcium ion mobilization from intracellular stores as well as the CRH-induced apoptosis and Fas ligand production. In conclusion, our findings suggest that CRH via its CRHR1 receptor differentially regulates PKC-isoenzyme phosphorylation, an apparently physiologically relevant effect since blockade of conventional PKC phosphorylation abolished the biological effect of CRH. 相似文献