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991.
Balss KM Ross D Begley HC Olsen KG Tarlov MJ 《Journal of the American Chemical Society》2004,126(41):13474-13479
Two types of DNA hybridization assays are demonstrated with temperature gradient focusing (TGF) and peptide nucleic acids (PNAs). In TGF, the application of a controlled temperature gradient along the length of a microchannel filled with an appropriate temperature-dependent buffer results in the formation of a gradient in both the electric field and electrophoretic velocity. Ionic species move in this gradient and concentrate at a unique point where the total velocity sums to zero. The first assay is a mixing assay in which PNA is allowed to flow through spatially focused DNA targets within a capillary. The second assay detects single base pair mutations (SBPM) by monitoring the fluorescence intensity of PNA/DNA duplexes as a function of temperature within the capillary. The SBPM analysis can be performed in less than 5 min with 100-fold more dilute analyte compared to conventional UV melting measurements. 相似文献
992.
Kimura H Tanigawa T Morisaka H Ikegami T Hosoya K Ishizuka N Minakuchi H Nakanishi K Ueda M Cabrera K Tanaka N 《Journal of separation science》2004,27(10-11):897-904
Separation of peptides by fast and simple two-dimensional (2D)-HPLC was studied using a monolithic silica column as a second-dimension (2nd-D) column. Every fraction from the first column, 5 cm long (2.1 mm ID) packed with polymer-based cation exchange beads, was subjected to separation in the 2nd-D using an octadecylsilylated (C18) monolithic sillica column (4.6 mm ID, 2.5 cm). A capillary-type monolithic silica C18column (0.1 mm ID, 10 cm) was also employed as a 2nd-D column with split flow/injection. Effluentof the first dimension (1st-D) was directly loaded into an injector loop of 2nd-D HPLC. UV and MS detection were successfully carried out at high linear velocity of mobile phase at 2nd-D using flow splitting for the 4.6 mm ID 2nd-D column, or with directconnection of the capillary column to the MS interface. Two-minute fractionation inthe 1st-D, 118-second loading, and 2-second injection by the 2nd-D injector, allowed one minute for gradient separation in the 2nd-D, resulting in a maximum peak capacity of about 700 within 40 min. The use of a capillary column in solvent consumption and better MS detectability compared to a larger-sized column. This kind of fast and simple 2D-HPLC utilizing monolithic silica columns will be useful for the separation of complex mixtures in a short time. 相似文献
993.
In order to make analytical measurement results traceable to the SI units in the field of clinical chemistry, an ion chromatographic (IC) measurement procedure has been developed which allows the amount of substance of the four so-called electrolytes Na, K, Mg and Ca as well as that of Li to be determined efficiently in human serum and with high accuracy. The IC measurement procedure was validated using primary measurement procedures confirmed by international comparison measurements and is proposed for use as a transfer standard when comparing measurements with clinical reference laboratories. The solutions used for calibration were gravimetrically prepared from pure substances (salts). Their chemical compositions had been iteratively fitted to those of the samples. The serum samples were mineralized by microwave-assisted digestion. The following relative expanded uncertainties for the average elemental contents were obtained: Li 0.4%, Na 0.14%, K 0.6%, Mg 0.8% and Ca 0.4%. 相似文献
994.
Karin Popa Alexandru Cecal Doina Humelnicu Ioan Caraus Camelia L. Draghici 《Central European Journal of Chemistry》2004,2(3):434-445
This study concerns the removal of the 137Cs+ and 60Co2+ β+γ-radioactive ions in Azolla caroliniana Willd. water fern. The living fern and two different types of biosorbent prepared from Azolla caroliniana were tested to remove the above-mentioned radioactive ions from dilute solutions, in the absence and in the presence of the
ionic competition. Effective 137Cs+ and 60Co2+ ions removal from low radioactive wastewaters was demonstrated. The time dependent K
d
(t) values were calculated from the absorption data. These results indicate that removal process achieved equilibrium in about
120 min and that it involves two steps: rapid and slow absorption; the active process (metabolic bioaccumulation on the living
fern) was responsible for above one half of the total removal process. A thin layer radiochromatography study leads to the
conclusion that the biochemical components in which 137Cs+ and 60Co2+ place themselves are of a polysaccharide and lipoid fractions. 相似文献
995.
Karin Czech Norbert Haider Gottfried Heinisch 《Monatshefte für Chemie / Chemical Monthly》1991,122(5):413-418
Summary Starting from 3-chloro-4-pyridazinecarbonitrile (1), the thienopyridazine derivatives2 and3 were prepared. Condensation of3 with triethyl orthoformate afforded the novel tricyclic system4. Reaction of1 with 2-aminothiophenol, followed by treatment with NaH/DMSO was found to give the diaza-phenothiazine6 instead of the expected condensed thiazepine.Dedicated with best wishes to Prof. Dr. G. Zigeuner on the occasion of his 70th anniversary 相似文献
996.
Aleš Doliška Simona Strnad Volker Ribitsch Karin Stana Kleinschek Stefan Willför Bodo Saake 《Cellulose (London, England)》2009,16(6):1089-1097
The aim of this study was to setup a method for detection and quantification of monosaccharide components in technical galactoglucomannas
(T-GGM) from spruce wood using capillary zone electrophoresis (CZE). CZE technique was optimised regarding borate buffer concentrations,
EOF modifier application, and system pH. Aqueous solution of T-GGM was chemically hydrolysed by sulphuric acid, in an autoclave.
In this way obtained monosaccharides were derivatized with 4-amino benzoic acid ethyl ester via reductive amination using
sodium cyanoborohydride. The results of the optimisation procedure showed that the borate buffers at lowest concentrations
(100 and 200 mM) with acetonitrile addition as EOF modifier gave the optimal measurement results, as it showed sufficient
separation at relatively short migration times. The amounts of single monosaccharide components in the T-GGM samples obtained
by the optimised CZE procedure were practically the same in comparison to the results of the well established HPLC-anion exchange
chromatography. On the basis of this research, it was concluded that the capillary zone electrophoresis is an efficient analytical
procedure for the characterisation of galactoglucomannans derived from softwoods. 相似文献
997.
998.
999.
Andreas Richter Wolfgang Wanek Roland A. Werner Jaleh Ghashghaie Maya Jäggi Arthur Gessler Enrico Brugnoli Elena Hettmann Sabine G. Göttlicher Yann Salmon Camille Bathellier Naomi Kodama Salvador Nogués Astrid Søe Fillip Volders Karin Sörgel Andreas Blöchl Rolf T. W. Siegwolf Nina Buchmann Gerd Gleixner 《Rapid communications in mass spectrometry : RCM》2009,23(16):2476-2488
Starch and soluble sugars are the major photosynthetic products, and their carbon isotope signatures reflect external versus internal limitations of CO2 fixation. There has been recent renewed interest in the isotope composition of carbohydrates, mainly for use in CO2 flux partitioning studies at the ecosystem level. The major obstacle to the use of carbohydrates in such studies has been the lack of an acknowledged method to isolate starch and soluble sugars for isotopic measurements. We here report on the comparison and evaluation of existing methods (acid and enzymatic hydrolysis for starch; ion‐exchange purification and compound‐specific analysis for sugars). The selectivity and reproducibility of the methods were tested using three approaches: (i) an artificial leaf composed of a mixture of isotopically defined compounds, (ii) a C4 leaf spiked with C3 starch, and (iii) two natural plant samples (root, leaf). Starch preparation methods based on enzymatic or acid hydrolysis did not yield similar results and exhibited contaminations by non‐starch compounds. The specificity of the acidic hydrolysis method was especially low, and we therefore suggest terming these preparations as HCl‐hydrolysable carbon, rather than starch. Despite being more specific, enzyme‐based methods to isolate starch also need to be further optimized to increase specificity. The analysis of sugars by ion‐exchange methods (bulk preparations) was fast but produced more variable isotope compositions than compound‐specific methods. Compound‐specific approaches did not in all cases correctly reproduce the target values, mainly due to unsatisfactory separation of sugars and background contamination. Our study demonstrates that, despite their wide application, methods for the preparation of starch and soluble sugars for the analysis of carbon isotope composition are not (yet) reliable enough to be routinely applied and further research is urgently needed to resolve the identified problems. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
1000.
Anette Funfak Jialan Cao Otto S. Wolfbeis Karin Martin J. Michael Köhler 《Mikrochimica acta》2009,164(3-4):279-286
Polymer microparticles containing an immobilized pH-sensitive dye are used for determination of pH inside microfluidic segments. The particles possess a hydrophilic surface in order to get a homogenous distribution inside the aqueous phase of microfluidic segments. The dye is coupled to the polymer matrix by a covalent bond. The pH can be determined by the read-out of fluorescence intensity. In contrast to dissolved indicator dyes, the chemical interference of the sensor particles with the surrounding solution is negligible. So, the particle-based sensing can easily be applied to the determination of pH changes during the cultivation of cells inside the microfluidic segments. The typical change of pH during cell cultivation can be used for monitoring the kinetic of cell cultivation inside single volumes in the nanoliter range, so that information about the metabolic activity of the organism can be obtained. An LED-based miniaturized flow-through fluorometer was developed to determine the fluorescence directly inside microtubes of an inner diameter of 0.5 mm. It allows measurement frequencies up to 60 Hz and is suited for characterization of fast moving large sequences of microfluidic segments. 相似文献