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1.IntroductionA fundamental problem in computer graphics is the drawing of a smooth curve through aset of data points(xi,fi) (i=0 ,1 ,… ,n) .In many applications,particularly in scientificvisualisation,the y- values are depenenton the x- values and it is… 相似文献
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Some of the most significant discoveries and achievements concerning the mass spectra and gas phase ion chemistry of carbon clusters are reviewed. These include (1) nanosecond and femtosecond laser ionizations; (2) ion structures through ion/molecule reactions, ion chromatography, and computational methods; (3) carbon cluster cooling through radiative decay, dissociative decay, and thermionic emission; (4) mechanisms and energetics of fragmentation reactions; (5) endohedral fullerenes including recent data on ion beam implantation, and (6) ion chemistry as a function of the fullerene charge state. 相似文献
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三次均匀B样条在服装CAD中的应用 总被引:2,自引:0,他引:2
张志强 《数学的实践与认识》2001,31(2):166-170
服装设计中三维向二维的转换是服装 CAD当今研究的重要课题之一 .依据投影原理寻找到三维衣片的边界点在平面上的对应位置 ,并利用三次均匀 B样条拟合二维边界点以实现三维衣片向二维衣片的转换 .经上机调试、运行、得到比较满意的结果 ,为今后深入研究奠定了基础 相似文献
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We adapted and optimized a method to quantify the cellulose, hemicellulose, xylan, arabinan, mannan, galactan contents in lignocellulosic biomass. This method is based on a neutral detergent extraction (NDE) of the interfering biomass components, followed by a sulfuric acid hydrolysis (SAH) of the structural polysaccharides, and a liquid chromatography with charged aerosol detection (LC-CAD) to analyze the released monosaccharides. The first step of this NDE-SAH-LC-CAD method aims at removing all compounds that interfere with the subsequent sulphuric acid hydrolysis or with the subsequent chromatographic quantification of the cellulosic and hemicellulosic monosaccharides. This step includes starch hydrolysis with an analytical thermostable α-amylase followed by an extraction of soluble compounds by a Van Soest neutral detergent solution (NDE). The aim of this paper was to assess the precision of this method when choosing fiber sorghum (Sorghum bicolor (L.) Moench), tall fescue (Festuca arundinacea Schreb.) and fiber hemp (Cannabis sativa L.) as representative lignocellulosic biomass. The cellulose content of fiber sorghum, tall fescue and fiber hemp determined by the NDE-SAH-LC-CAD method were 28.7 ± 1.0, 29.7 ± 1.0 and 43.6 ± 1.2 g/100 g dry matter, respectively, and their hemicellulose content were 18.6 ± 0.5, 16.5 ± 0.5 and 14.5 ± 0.2 g/100 g dry matter, respectively. Cellulose, mannan and galactan contents were higher in fiber hemp (dicotyledon) as compared to tall fescue and fiber sorghum (monocotyledons). The xylan, arabinan and total hemicellulose contents were higher in tall fescue and fiber sorghum as compared to fiber hemp. The precision of the NDE-SAH-LC-CAD method was better for polysaccharide concentration levels above 1 g/100 g dry matter. Galactan analysis offered a lower precision, due to a lower CAD response intensity to galactose as compared to the other monosaccharides. The dispersions of the results (expanded uncertainty) of the NDE-SAH-LC-CAD method were smaller as compared to the Van Soest (VS) method. In addition, the NDE-SAH-LC-CAD method was able to provide additional information on the composition of the hemicellulose (xylan, arabinan, mannan and galactan content) that is not provided by the Van Soest method. The NDE-SAH-LC-CAD method offers also the advantage of a better specificity for hemicellulose and cellulose, as compared to the NREL and Uppsala methods. 相似文献
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The particularity of metalloid clusters as a special kind of metal atom cluster is described. For the first time such metalloid clusters are investigated in the gas phase by means of FT/ICR–mass spectrometry, the results of which show that metalloid clusters represent a bridge between the bulk metal and metal compounds that can be found in solution after oxidation of the bulk metal. The metalloid clusters presented herein are [Ga19R6]– (R=C(SiMe3)3), and SiAl14Cp*6 and the precursor Al4Cp*4 (Cp*=
5-C5Me5). 相似文献
129.
Huy Truong Nguyen Kim Long Vu-Huynh Hien Minh Nguyen Huong Thuy Le Thi Hong Van Le Jeong Hill Park Minh Duc Nguyen 《Molecules (Basel, Switzerland)》2021,26(17)
Panax vietnamensis, or Vietnamese ginseng (VG), an endemic Panax species in Vietnam, possesses a unique saponin profile and interesting biological activities. This plant is presently in danger of extinction due to over-exploitation, resulting in many preservation efforts towards the geographical acclimatization of VG. Yet, no information on the saponin content of the acclimatized VG, an important quality indicator, is available. Here, we analyzed the saponin content in the underground parts of two- to five-year-old VG plants acclimatized to Lam Dong province. Nine characteristic saponins, including notoginsenoside-R1, ginsenoside-Rg1, -Rb1, -Rd, majonoside-R1, -R2 vina-ginsenoside-R2, -R11, and pseudoginsenoside-RT4, were simultaneously determined by HPLC coupled with UV and with a charged aerosol detector (CAD). Analyzing the results illustrated that the detection of characteristic ocotillol-type saponins in VG by CAD presented a superior capacity compared with that of UV, thus implying a preferential choice of CAD for the analysis of VG. The quantitative results indicating the saponin content in the underground parts of VG showed an increasing tendency from two to five years old, with the root and the rhizome exhibiting different saponin accumulation patterns. This is the first study that reveals the preliminary success of VG acclimatization and thereby encourages the continuing efforts to develop this valuable saponin-rich plant. 相似文献