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排序方式: 共有266条查询结果,搜索用时 15 毫秒
151.
P. J. Huck G. Pritchard 《Journal of polymer science. Part A, Polymer chemistry》1973,11(12):3293-3298
Reaction between stilbene and a difunctional ether, in presence of Lewis acid catalyst, produces low molecular weight condensation polymers containing substantial olefinic unsaturation. These resins have been studied by various analytical techniques. Some evidence is presented concerning structure. The condensation polymers are soluble in organic solvents and may be cross linked by free-radical methods to form thermosetting networks. 相似文献
152.
In this review, an overview of CEC and EKC methods with their developments are summarized for different natural compounds. It is divided into three main parts. The first part elaborates the separation of lipophilic compounds without any charged groups. The second part constitutes CEC and EKC of lipophilic compounds containing ionizable functional groups whereas the third part contains hydrophilic compounds. Packed, monolithic, coated, or raw fused-silica (FS) capillaries are among the choice for stationary phases. Applications of these phases on the above-mentioned three classes of compounds, coupled with different detection methods, e.g. MS or LIF, are explored and their advantages and disadvantages are discussed. 相似文献
153.
Moya SE Azzaroni O Kelby T Donath E Huck WT 《The journal of physical chemistry. B》2007,111(25):7034-7040
The conformational behavior of poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes with different chain density in the presence of large benzyltributylammonium chloride (BTBAC) ions has been studied by a Quartz Crystal Microbalance with Dissipation (QCM-D) and Scanning Force Microscopy. Dense brushes do not collapse in the presence of BTBAC solutions of increasing ionic strength, contrary to what is observed in the presence of NaCl. Brush collapse can be observed for low-ionic-strength solutions of BTBAC when the brush density has been reduced. These phenomena can be explained by considering the Hofmeister series as well as ion size and free space in the brush. 相似文献
154.
Hahn H Huck CW Rainer M Najam-ul-Haq M Bakry R Abberger T Jennings P Pfaller W Bonn GK 《Analytical and bioanalytical chemistry》2007,388(8):1763-1769
A simple and highly effective reversed-phase (RP) high-performance liquid chromatography (HPLC) method is described for analysing
glutathione (GSH) and glutathione disulfide (GSSG) in out-flowing supernatants and lysates of perfusion cell cultures of human
kidney cells (HK-2 cells) continuously exposed to cadmium chloride (CdCl2), which is a well-known nephrotoxin. The developed linear liquid chromatographic gradient employs monolithic poly(styrene-co-divinylbenzene) (PS/DVB) as a stationary phase and is adaptable for coupling to mass spectrometry via an electrospray ionisation
interface (LC-ESI/MS), which is carried out in case of co-eluting peaks. This study presents a quantitative assay of glutathione
over the time of experiment and cell lysates at the end of the experiment. The assay of out-flowing supernatants has the potential
to be applied as an online assay in high time resolution. Glutathione (reduced and oxidised, GSH and GSSG) is chosen as an
indicator for toxic effects in the cultured cells. In principle it is possible to show the concentration of glutathione as
a function of time in an investigation of exposure of the HK-2 cell line to CdCl2. In addition to glutathione analysis, well-established assays of cell death such as enzyme release and cell viability are
performed to obtain information about the number of living cells. Toxicity of 5 μM CdCl2 is manifested in all of the assays applied. Fast (<7 min) and highly reproducible (max. aberration 4.7%) determination of
glutathione could be achieved. 相似文献
155.
A CE method employing capacitively coupled contactless conductivity (C(4)D) compared to indirect UV-detection was developed for the analysis of phytochemically relevant flavonoids, such as 6-hydroxyflavone, biochanin A, hesperetin and naringenin. To ensure fast separation at highest selectivity, sensitivity and peak symmetry, the pH value and the concentration of the running BGE had to be optimized regarding both co- and counter-EOF mode. Optimum conditions were found to be 1.0 and 5.0 mM chromate BGE (pH 9.50) in the counter- and co-EOF mode, respectively. Validation of the established CE-C(4)D method pointed out to be approximately seven times more sensitive compared to indirect UV-detection applying the same conditions. The lower LOD defined at an S/N of 3:1 was found between 0.12 and 0.21 microg/mL for the analytes of interest using C(4)D and between 0.77 and 1.20 microg/mL using indirect UV-detection. Compared to an earlier published CE method employing direct UV-detection, C(4)D was found to be approximately two times more sensitive. Due to the lower baseline noise, C(4)D showed an excellent regression coefficient >0.99 compared to 0.93 when using indirect UV detection calibrating within a concentration range between 1 and 10 microg/mL. The influence of the sugar moiety on the conductivity of a flavonoid was studied upon the analysis of the aglycon hesperetin and the rutinosid hesperidin. The sugar moiety in hesperedin shows a higher conductivity compared to hesperetin. Finally, the optimized established CE-C(4)D method was applied to the determination and quantification of naringenin in Sinupret. 相似文献
156.
R. S. Brusa A. Somoza H. Huck N. Tiengo G. P. Karwasz A. Zecca M. Reinoso E. B. Halac 《Applied Surface Science》1999,150(1-4):202-210
Hard amorphous carbon films produced using high-energy (ca. 30 keV) ion beam deposition of CH3+ and CH4+ on silicon wafers, have been investigated by Positron Annihilation Spectroscopy (PAS), the results are correlated with Raman Spectroscopy and Electrical Resistivity measurements. The microstructural modifications of the films as a function of the annealing temperature in the 300–600°C range have been studied. The evolution of the fractions of sp2 and sp3 bonds is described and related to the changes of the open volume defect distribution and the graphitization process. 相似文献
157.
158.
159.
Bart-Hendrik Huisman Holger Schnherr Wilhelm T. S. Huck Arianna Friggeri Henk-Jan van Manen Edoardo Menozzi G. Julius Vancso Frank C. J. M. van Veggel David N. Reinhoudt 《Angewandte Chemie (International ed. in English)》1999,38(15):2248-2251
The incorporation of dialkyl sulfide side chains in metallodendrimers is a simple method for their insertion into a monolayer of decanethiol formed by self-assembly on a gold surface. The dendrimer binds through the sulfide group to a defect in the monolayer on the gold surface (see picture). The surface concentration of the isolated dendrimer adsorbate can be regulated by the adsorption time (for example, 55 adsorbates on a surface of 200×200 nm2 after 20 h). 相似文献
160.
Frank C. J. M. van Veggel Wilhelm T. S. Huck David N. Reinhoudt 《Macromolecular Symposia》1998,131(1):165-173
Building blocks have been designed for the non-covalent formation of nanosize assemblies. As non-covalent interactions coordination chemistry and hydrogen bonding have been used. The self-assembly process leads to spherical assemblies with diameters in the range of 100 to 400 nm, with standard deviations in the order of 10–15%. The controlled assembly approach allows a precise controll of size and assemblies with molecular weights up to 10,000 Dalton have been realized. Finally, we have developed a strategy in which hydrogen bonding and coordination chemistry can be applied “orthogonally” 相似文献