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211.
Jan Blomberg Peter J. Schoenmakers Jan Beens Robert Tijssen 《Journal of separation science》1997,20(10):539-544
In general, petrochemical products contain only a limited number of chemical classes of compounds (sample dimensionality). The enormous number of individual components within these classes, however, soon puts limitations upon a single chromatographic technique when it comes to adequate characterization of these products. Comprehensive two-dimensional gas chromatography (GC×GC) clearly opens the possibility of estimating the composition of hydrocarbon mixtures in a far more detailed fashion than hitherto possible. Although the emphasis of papers of GCxGC thus far almost exclusively applies to the unsurpassed peak-capacity, in the oil industry there is a need for characterization, rather than for analyzing all the individual compounds. In principle a GCxGC system can provide an almost perfect match between its intrinsic properties and the dimensionality of oil samples. To establish the applicability of GCxGC towards petrochemical analytical challenges, a commercially aavailable prototype instrument was subjected to an exhaustive characterization of a typical hydrocarbon precess stream and a fast characterization of a light gas oil. Although there are no fundamental limitations towards the quantitative aspects of a GCxGC system, this paper confines itself to qualitative results only. Quantitative aspects of GCxGC will be published in a forthcoming paper. 相似文献
212.
Capillary gc is now rapidly expanding. Naturally, initiation is most often attempted on the basis of the experience acquired with packed columns. However, such an extrapolation is successful only if a number of essential peculiarities of capillary gc are considered. Based on practical examples this paper discusses six essential details: 1) design and maintenance of the gas flow paths, 2) the greatly increased importance of sampling technique, which should not be confined just to stream splitting, 3) the problems in quantitative analysis arising from small sample size, 4) specific sources of trouble related to small amounts of liquid phase, 5) specific arguments for the choice of the carrier gas, clearly pointing to hydrogen as the ideal carrier and, 6) the different way to approach column production. Figures for all selected examples are given. 相似文献
213.
214.
The gas-chromatographic method is used to study the interaction of water and methanol molecules with active hydrophilic centres
existing at the surface of thermally exfoliated graphite and graphitized thermal carbon black. The concentration of carboxyl
and phenol hydroxyl groups at the surface of these sorbents is determined, and heats of adsorption of the studied molecules
are shown to be
and 28−25 kJ/mol, respectively. It is also shown that adsorption of water at the hydrophilic centres at lowest relative pressure
values takes place with formation of clusters consisting of n = 2 water molecules. 相似文献
215.
A technique has been developed for performing headspace GC-MS analysis of volatile components of food, in which the carrier gas flow is reversed during sampling in order to overcome problems caused by the diffusion of substances not retained by the cold trap. Chromatographic profiles of volatile compounds from cheeses, obtained at room temperature, provide confirmation of the validity of the reversed flow technique, and the versatility of the system is evidenced by its successful application to both solid and liquid matrixes: the absence of any discrimination against the various components reveals its efficacy for compounds with a wide range of volatility. Addition of internal standards to the sample enables the use of the technique for quantitative analysis. 相似文献
216.
Edoardo Apr Emily A. Carter Alessandro Fortunelli 《International journal of quantum chemistry》2005,101(2):230-230
Density Functional Theory (DFT) and direct ab initio molecular dynamics (MD) calculations were applied to the hydrogen molecule trapped in a water cluster composed of 12 water molecules (H2O)12. The static DFT calculation showed that the H2 molecule is trapped in the center of mass of (H2O)12. The vibrational frequency of the H–H stretching mode of the H2 molecule trapped in the water cluster was blueshifted from that in vacuo. On the other hand, the vibrational frequency of H2 in water‐hydrogen 1:1 complex (H2O–H2) was redshifted. A direct ab initio MD calculation of H2(H2O)12 at 50 K indicated that the H2 molecule is rotated freely around the center of mass of the water cluster. The origin of the spectral shift of H2 in water ice is discussed on the basis of the theoretical results. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
217.
吹扫-捕集气相色谱法测定水中挥发性卤代烃 总被引:5,自引:0,他引:5
研究建立了吹扫 捕集法富集样品 ,利用HP 1大口径厚液膜通用型熔融石英毛细管柱 (30m× 0 .5 3mm×2 .6 5 μm) ,ECD检测器 ,测定水中 10种挥发性卤代烃的方法 ,确定了最佳吹扫 捕集条件 .结果表明 :水样体积为 5mL时 ,标准偏差在 0 .0 2~ 0 .0 7μg L之间 ,变异系数在 1.0 9%~ 3.2 8%之间 ,加标回收率为 94.0 %~ 10 7%之间 ,10种物质的检出限在 0 .0 7~ 0 .19μg L之间 相似文献
218.
219.
220.
利用色谱-质谱联机技术,在红收获蚁P.barbatus和P.maricopa的毒腺体样品中检测到召引信息素甲基吡嗪(MP)、2,5-二吡嗪(DMP)、3-乙基-2,5-二甲基吡嗪(EDMP)、和三甲基吡嗪(TMP)。利用特征离子色谱技术,在P.barbatus样品中还检测到了含6个碳原子侧链烃基的吡嗪X。根据吡嗪X的质谱图推测其结构为3-仲丁基-2,5-二甲基吡嗪(BDMP)。P.barbatus中DMP,TMP和EDMP的平均相对百分比分别为60.71、26.49、12.80;标准偏差分别为6.91、4.92、5.11;P.maricopa中平均相对百分比和标准偏差分别为47.48、20.35、32.17和15.05、4.05、15.44。 相似文献