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91.
Quality assurance and process understanding are assuming increasing importance in the production of Active Pharmaceutical Ingredients (APIs). NMR has the potential to report on physical processes, quantities, structures, and speciation as chemical reactions progress. Following the progression of chemical reactions by placing the sample in an NMR tube, one can perform a large number of useful studies that provide chemical and mechanistic insight. But this simple approach can have limitations, and we have therefore constructed an apparatus comprising a laboratory reactor coupled with an NMR flow cell. The reactor duplicates the exact reaction conditions that will apply with large-scale production. This reaction mixture is sampled and pumped to a high-resolution NMR flow cell where the spectrum is recorded through the course of the reaction. We demonstrate the utility of reaction monitoring using NMR both for simple cases where tubes can be used, and describe the design of the on-flow apparatus and highlight its utility with an example. 相似文献
92.
Mauriz E Calle A Manclús JJ Montoya A Lechuga LM 《Analytical and bioanalytical chemistry》2007,387(4):1449-1458
Multi-analyte detection of environmentally relevant pesticides is performed by using a two-channelled surface plasmon resonance
(SPR) biosensor. The special design of the SPR instrument allows the determination of several analytes (DDT, chlorpyrifos
and carbaryl) via different immobilization formats. First, simultaneous pesticide monitoring is possible by flowing chlorpyrifos,
carbaryl or DDT samples separately over each channel of the SPR system, wherein their corresponding recognition element was
previously immobilized. The second approach is based on the multiple and combined immobilization of several analyte recognition
elements on the sensing surface of one individual flow cell. In this format, the analysis time for all three pesticides varied
from 40 to 60 min depending on the number of regeneration cycles. In most cases, similar detection limits were attained for
the target analyte irrespective of the assay format, with sensitivity values at the nanogram per litre level (18–50 ng L−1). The assay reproducibility was proved through the repeated use of the same sensor surface for over more than 200 assay cycles,
whereas the absence of biosensor response to non-related analytes showed the specificity and reliability of the analysis.
The SPR instrument, including optics, electronics and microfluidics, is already commercialised by the company SENSIA, SL. 相似文献
93.
利用商品化ITO玻璃导电层的温阻效应, 无需任何微加工手段, 实现了自加热和传感的芯片温度自动程序控制, 最大程度地减小了传感滞后对温度控制稳定性的影响, 温度控制的稳定性达到了0.2 ℃, 升温速度最快可达20 ℃/s以上, 在冷却风扇辅助下降温速度最快达到了8 ℃/s. 芯片温控单元的引线从传统的两对(一对用于传感, 一对用于加热)减少为一对. 通过在该芯片上直接构建多个开放微池反应器的方法成功地实现了λDNA 157 bp片段的并行扩增. 将该芯片置于倒置荧光显微镜样品台上, 以蓝色(575 nm)发光二极管为光源, 以光电倍增管为检测手段检测了dsDNA和SYBR Green Ⅰ嵌合物的荧光强度随温度的实时变化曲线. 相似文献
94.
95.
Metabolism of <Superscript>14</Superscript>C-labelled and non-labelled sulfadiazine after administration to pigs 总被引:1,自引:0,他引:1
Lamshöft M Sukul P Zühlke S Spiteller M 《Analytical and bioanalytical chemistry》2007,388(8):1733-1745
The behaviour of sulfadiazine (SDZ) and its metabolites was investigated by administering the 14C-labelled veterinary drug to fattening pigs. The excretion kinetics were determined after daily collection of manure. Two
known metabolites, N-acetylsulfadiazine and 4-hydroxysulfadiazine, and two hitherto unidentified minor metabolites were recovered. Various mass
spectrometric techniques such as parent, product ion scans and accurate mass measurement were used. The new compounds were
identified as N-formylsulfadiazine (For-SDZ) and N-acetyl-4-hydroxysulfadiazine (Ac-4-OH-SDZ). The identification of SDZ, Ac-SDZ and For-SDZ was confirmed by comparison of
the spectroscopic and chromatographic data of the synthesized authentic references. The identification of the hydroxylated
compounds 4-OH-SDZ and Ac-4-OH-SDZ was performed by MSn, and accurate mass measurements. Only 4% of the administered radioactivity remained in the pig after ten days and SDZ accounted
for 44% of the 96% radioactivity excreted. More than 93% of the labelled compounds were detected and identified in the manure.
The key analytical problem, namely a high concentration of matrix in sample extracts, was overcome by advanced measurement
techniques and with the use of a suitable internal standard. The mean recoveries for all compounds were ≥96%. Linearity was
established over a concentration range of 0.5 to 10,000 μg kg−1 manure with a correlation coefficient ≥0.99. The same experiment was carried out simultaneously with non-labelled SDZ to
obtain manure for outdoor soil experiments. 相似文献
96.
Jocelyn Jalbert Roland Gilbert Pierre Tétreault Brigitte Morin Denise Lessard-Déziel 《Cellulose (London, England)》2007,14(4):295-309
In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by
the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative
conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture
of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the
number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded
(TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper
constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the
system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial
moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular
chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing
transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of
equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and
TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential
over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with
2-furfuraldehyde, which is the current reference in the domain. 相似文献
97.
Photoionization Detector for Portable Rapid GC 总被引:1,自引:0,他引:1
With the development of portable rapid gas chromatography (GC) for environmental monitoring the photoionization detector (PID)
has potential application. The frequent calibration required and the relatively large dead volume have limited the use of
the PID, however. An improved PID which resolves these problems is proposed in this paper. Compared with a commercial instrument,
signal generation, the main aspect of the improved PID, has also been optimized. In the improved PID the sample is directed
to flow across the lamp window, rather than toward the lamp, and a new, simple automatic self-cleaning technique, which effectively
eliminates contaminants and substantially reduces drift, has also been adopted. Use of new electrodes has effectively reduced
the background noise and dead volume of the PID. As a result of this new design the PID should be more compatible with rapid
portable GC in environmental monitoring, because of elimination of most of the tedious cleaning and calibration previously
necessary. 相似文献
98.
根据《环境监测质量管理规定》、《江苏省环境监测质量管理实施细则》及环境监测技术规范的要求,探讨了降水监测采样、样品保存技术、实验室分析的质量控制方法。采用不同采样方法、不同采样器同时采集15场降水,其降雨量、电导率、pH值的比对监测结果合格率均大于90%。经试验,降水各组分有效保存时间不同,其中NO_3~-,NH_4~+为3 d;F~-,Cl~-,SO_4~(2-)为14d;K~+,Na~+,Ca~(2+),Mg~(2+)为30 d。选择2家实验室对降水样品、空白样品、标准样品同时测试,结果显示,空白测定结果均低于方法检出限,标准曲线相关性系数r≥0.999 0,测定结果的相对标准偏差为1.4%~5.9%(n=6),加标回收率为89.8%~106%,标准样品的分析结果均合格。该方法能保证降水监测结果准确、可靠,满足HJ/T 165-2004《酸沉降监测技术规范》的要求。 相似文献
99.
The in-situ and high-throughput evaluation of enzymes and real-time monitoring of enzyme catalyzed reactions in liquid phase is quite significant in the catalysis industry. In-situ nanoelectrospray, the direct sampling and ionization method for mass spectrometry, has been applied for high-throughput evaluation of enzymes, as well as the on-line monitoring of reactions. Simply inserting a capillary into a liquid system with high-voltage applied, analytes in liquid reaction system can be directly ionized at the capillary tip with small volume consumption. With no sample pre-treatment or injection procedure, different analytes such as saccharides, amino acids, alkaloids, peptides and proteins can be rapidly and directly extracted from liquid phase and ionized at the capillary tip. Taking irreversible transesterification reaction of vinyl acetate and ethanol as an example, this technique has been used for the high-throughput evaluation of enzymes, fast optimizations, as well as real-time monitoring of reaction catalyzed by different enzymes. In addition, it is even softer than traditional electrospray ionization. The present method can also be used for the monitoring of other homogenous and heterogeneous reactions in liquid phases, which will show potentials in the catalysis industry. 相似文献
100.