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排序方式: 共有269条查询结果,搜索用时 171 毫秒
121.
Joél Smet Sara Seneca Boel De Paepe Ann Meulemans Helene Verhelst Jules Leroy Linda De Meirleir Willy Lissens Rudy Van Coster 《Electrophoresis》2009,30(20):3565-3572
Complex V, site of the final step in oxidative phosphorylation, uses the proton gradient across the inner mitochondrial membrane for the production of ATP. It is a multi‐subunit complex composed of a catalytic domain (F1) and a membrane domain (F0) linked by two stalks. Subcomplexes of complex V containing the F1 domain have previously been reported in small series of patients. We report the results in tissue samples and/or cultured skin fibroblasts studied by blue native PAGE followed by activity staining in the gel. Catalytically active subcomplexes of complex V were detected in 66 tissues originating from 53 patients. In 29 of the latter (55%), a mitochondrial DNA (mtDNA) defect was identified. Twelve patients had a pathogenic point mutation in a mitochondrial tRNA, one a large mtDNA deletion, 12 showed mtDNA depletion and four had a mutation in the MT‐ATP6 gene. We conclude that the presence of subcomplexes of complex V is a valuable indicator in the detection of mtDNA defects. 相似文献
122.
Marie-Hélène Dévier Pierre Labadie Anne Togola Hélène Budzinski 《Analytica chimica acta》2010,657(1):28-879
A simple analytical procedure for the simultaneous determination of eight endogenous steroids (testosterone, androstenedione, 17β-estradiol, estrone, pregnenolone, progesterone, dihydroandrostenedione, and dihydrotestosterone) in aquatic molluscs by solid-phase extraction (SPE) and gas chromatography/mass spectrometry (GC-MS) has been developed. After a microwave-assisted extraction, samples were further extracted and purified using two successive SPE (EnviChrom-P and NH2) cartridges. Steroids were derivatized with a mixture of N-methyl-N(trimethylsilyl)trifluoroacetamide (MSTFA)/mercaptoethanol/ammonium iodide (NH4I) and determined by GC-MS in selective ion monitoring mode. Recoveries were in the range 85-114%, although slightly lower for dihydrotestosterone, and the repeatability of the procedure, expressed as the coefficient of variation, was lower than 16%. The limits of detection determined in digestive glands of mussels were in the range 0.1-0.4 ng g−1 wet weight for all the steroids. The developed procedure was then applied to the monitoring of steroid profiles in the digestive glands of mussels from the Arcachon Bay (France) during two reproductive cycles. In parallel, two physiological parameters (lipid content and the condition index of mussels) were also monitored, as well as the seawater temperature and salinity. Only progesterone and pregnenolone were detected in the digestive glands of mussels, and the seasonal variations of progesterone levels seemed to be related to the spawning periods of Mytilus sp. in the Bay. The current challenge for the determination of natural steroids in aquatic invertebrates is also briefly discussed. 相似文献
123.
Podszun S Vulto P Heinz H Hakenberg S Hermann C Hankemeier T Urban GA 《Lab on a chip》2012,12(3):451-457
Macro- to micro-volume concentration of viable bacteria is performed in a microfluidic chip. The enrichment principle is based on free flow electrophoresis and is demonstrated for Gram positive bacteria. Bacteria from a suspension flow are trapped on a gel interface that separates the trapping location from integrated actuation electrodes in order to enable non-destructive trapping. The microfluidic chip contains integrated electrolytic gas expulsion structures and phaseguides for gel and liquid handling. Trapping efficiency is systematically optimized to reach 25 times the initial concentration from a theoretical maximum of 30. Finally, enrichment from analytically relevant concentrations down to 3 × 10(2) colony forming units per millilitre is demonstrated with a trapping efficiency of 80% which represents the most important parameter in enrichment. 相似文献
124.
Hopfer H Haar N Stockreiter W Sauer C Leitner E 《Analytical and bioanalytical chemistry》2012,402(2):903-919
In a previous study, we identified carbonyls as highly odor-active compounds in both unprocessed and processed polypropylene
(PP) with higher intensities after processing, indicating a temperature-driven forming mechanism. In the presented work, we
studied whether (a) these carbonyls are the major odor drivers to the overall odor of polyolefins, (b) their formation is
taking place already at moderate temperatures well below the typical processing temperatures, (c) conventional antioxidants
in polyolefins can prevent or reduce their formation, and (d) whether reducing the amount of oxygen present can decrease the
overall odor. One polyethylene (PE) and one PP were selected, and both stabilized and unstabilized polymer powder samples
were exposed to conditions differing in oxygen concentration and aging time. The changes in the volatile fraction as well
as the formation of odor-active compounds were monitored using a multidisciplinary approach by combining analytical methods
based on gas chromatography (GC), multivariate data analysis, and sensory methods (GC–olfactometry and a sensory panel). Both
investigated materials (PE and PP) showed similar degradation products (aldehydes, ketones, carboxylic acids, alcohols, and
lactones) which increased dramatically with increasing aging time and the lack of stabilization. Oxidation products, mainly
carbonyl compounds, were responsible for the odor of the investigated materials. The main odor drivers were unsaturated ketones
and aldehydes with a chain length between six and nine C-atoms. Interestingly, similar odor patterns were found for both stabilized
and unstabilized samples, indicating that similar formation processes take place independent of the stabilization. 相似文献
125.
Faber H Melles D Brauckmann C Wehe CA Wentker K Karst U 《Analytical and bioanalytical chemistry》2012,403(2):345-354
Diclofenac is a frequently prescribed drug for rheumatic diseases and muscle pain. In rare cases, it may be associated with
a severe hepatotoxicity. In literature, it is discussed whether this toxicity is related to the oxidative phase I metabolism,
resulting in electrophilic quinone imines, which can subsequently react with nucleophiles present in the liver in form of
glutathione or proteins. In this work, electrochemistry coupled to mass spectrometry is used as a tool for the simulation
of the oxidative pathway of diclofenac. Using this purely instrumental approach, diclofenac was oxidized in a thin layer cell
equipped with a boron doped diamond working electrode. Sum formulae of generated oxidation products were calculated based
on accurate mass measurements with deviations below 2 ppm. Quinone imines from diclofenac were detected using this approach.
It could be shown for the first time that these quinone imines do not react with glutathione exclusively but also with larger
molecules such as the model protein β-lactoglobulin A. A tryptic digest of the generated drug–protein adduct confirms that
the protein is modified at the only free thiol-containing peptide. This simple and purely instrumental set-up offers the possibility
of generating reactive metabolites of diclofenac and to assess their reactivity rapidly and easily. 相似文献
126.
A number of porous salts based on the pamoate anion in combination with lutidinium or picolinium cations have been characterised. One salt undergoes single-crystal to single-crystal solvent exchange, while another isostructural series of salts contain channels that can be partly evacuated without collapse of the framework. 相似文献
127.
128.
We discuss thermoforming of thermoplastic polymers for the hot-embossing lithographic (HEL) fabrication of microfluidic chips near equilibrium conditions that minimize elastic recoil for optimal motif replication. While HEL is often simplistically described as the transfer of micro- and nano-motifs into heat-softened thermoplastic materials, we describe our rational approach to selecting appropriate processing parameters. 相似文献
129.
Ohne Zusammenfassung 相似文献
130.
The combination of electrochemistry (EC) and mass spectrometry (MS) has become a more and more frequently used approach in metabolism studies in the last decade. This review provides insight into the importance of metabolism studies during the drug development process and gives a short overview about the conventionally used methods since electrochemistry is often intended to substitute or minimize animal-based studies. The optimization of the electrochemical conditions is of great importance for a successful comparison with in vitro approaches. The type of metabolism reactions, which can be simulated by EC, has been extended with new cell types and working electrodes. Although the mechanism differs from the enzyme-catalyzed turnover, electrochemistry can be used to simulate a significant number of the respective reactions. 相似文献