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921.
为了对柴油车运行过程中发生的燃油稀释润滑油的程度作出及时定量评价,建立了差示红外光谱定量测定润滑油被燃油稀释程度的方法,并根据朗伯-比耳定律建立了吸光度与柴油浓度的校准曲线.结果表明,该分析方法对柴油车使用过程中燃油稀释润滑油的程度能快速准确定量,并且具有重复性好,可信度高的特点.柴油稀释润滑油的程度在0-5.0wt%内呈良好线性关系,线性回归方程为y=0.0085x+0.0048(R2=0.9933).本方法对于发生燃油稀释润滑油的故障能快速诊断,可用于对大批量的行车试验样品进行快速量评估.相对于美国材料与试验协会标准方法ASTM3524中采用气相色谱法来定量分析润滑油中燃油含量,本方法更加快速,使用成本更低廉. 相似文献
922.
采用有限元微磁学模拟方法研究了Co纳米线在不同外加恒磁场下磁矩的翻转过程.研究结果表明在直径为10 nm的Co纳米线内,经过一定的形核时间将在其一端形成一个反向磁畴.磁畴壁的类型为横向畴壁,该畴壁将在一外加恒定磁场的驱动下匀速地从一端运动到另一端.畴壁的运动速度与外加磁场大小呈线性关系.在H为1000 kA/m时,发现在纳米线的两端均会形成一个“头对头”的反向磁畴.计算结果表明,畴壁内磁矩的方向旋转一个周期所导致的畴壁运动的距离相同,与外加磁场强度无关.
关键词:
磁性纳米线
微磁学模拟
磁畴
横向畴壁 相似文献
923.
924.
Ningfang Song Dezhao Yang Zhili Lin Pan Ou Yudong Jia Mingjie Sun 《Optics & Laser Technology》2012,44(2):452-458
The performance of linear frequency-modulated continuous-wave (LFMCW) coherent Lidar system is inevitably influenced by the modulation characteristics of the transmitting light and some issues may arise when the system does not work under the ideally specified conditions. The relationship between the asymmetric and nonlinear modulation of transmitting light with the quality of the resulting beat frequency signal (BFS) for the non-zero velocity cases is mathematically modeled and the effective means for eliminating or alleviating these harmful influences are given. The results that are obtained from both numerical simulations and practical system experiments demonstrate that the errors of range and velocity measurement are proportional to the asymmetric coefficients and its square, respectively, and 30% relative error of range measurement occurs even through the values of normalized 2nd- and 3rd-order polynomial nonlinear-coefficients is as low as 0.1%. The rating of merit experiments of a Lidar system in range and velocity measurement is conducted, and the obtained results are in good agreement with their analytical and numerical simulation counterparts. 相似文献
925.
926.
927.
Preparation of polystyrene/silica nanocomposites by radical copolymerization of styrene with silica macromonomer 总被引:1,自引:0,他引:1
A two-stage process has been developed to generate the silica-based macromonomer through surface-modification of silica with polymerizable vinyl groups. The silica surfaces were treated with excess 2,4-toluene diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). Thus, polystyrene/silica nanocomposites were prepared by conventional radical copolymerization of styrene with silica macromonomer. The main effecting factors, such as ratios of styrene to the macromonomer, together with polymerization time on the copolymerization were studied in detail. FTIR, DSC and TGA were utilized to characterize the nanocomposites. Experimental results revealed that the silica nanoparticles act as cross-linking points in the polystytene/silica nanocomposites, and the glass transition temperatures of the nanocomposites are higher than that of the corresponding pure polystyrene. The glass transition temperatures of nanocomposites increased with the increasing of silica contents, which were further ascertained by DSC. 相似文献
928.
929.
Ou MH Chen YM Chang YH Lu WK Liu GC Wang YM 《Dalton transactions (Cambridge, England : 2003)》2007,(26):2749-2759
With the objective of tuning the lipophilicity of ligands and maintaining the neutrality and stability of Gd(III) chelate, we designed and synthesized two bis(amide) derivatives of TTDA, TTDA-BMA and TTDA-BBA, and a mono(amide) derivative, TTDA-N-MOBA. The ligand protonation constants and complex stability constants for various metal ions were determined in this study. The identification of the microscopic sites of protonation of the amide ligand by 1H NMR titrations show that the first protonation site occurs on the central nitrogen atom. The values of the stability constant of TTDA-mono and bis(amide) complex are significantly lower than those of TTDA and DTPA, but the selectivity constants of these ligands for Gd(III) over Zn(II) and Cu(II) are slightly higher than those of TTDA and DTPA. On the basis of the water-exchange rate values available for [Gd(TTDA-BMA)(H2O)], [Gd(TTDA-BBA)(H2O)] and [Gd(TTDA-N-MOBA)(H2O)]-, we can state that, in general, the replacement of one carboxylate group by an amide group decreases the water-exchange rate of the gadolinium(III) complexes by a factor of about three to five. The decrease in the exchange rate is explained in terms of a decreased steric crowding and charge effect around the metal ion when carboxylates are replaced by an amide group. In addition, to support the HSA protein binding studies of lipophilic [Gd(TTDA-N-MOBA)(H2O)]- and [Gd(TTDA-BBA)(H2O)] complexes, further protein-complex binding was studied by ultrafiltration and relaxivity studies. The binding constants (KA) of [Gd(TTDA-N-MOBA)(H2O)]- and [Gd(TTDA-BBA)(H2O)] are 8.6 x 10(2) and 1.0 x 10(4) dm3 mol(-1), respectively. The bound relaxivities (r1(b)) are 51.8 and 52 dm3 mmol(-1) s(-1), respectively. The KA value of [Gd(TTDA-BBA)(H2O)] is similar to that of MS-325 and indicates a stronger interaction of [Gd(TTDA-BBA)(H2O)] with HSA. 相似文献
930.
Sapphyrin-nanotube assemblies 总被引:1,自引:0,他引:1
Boul PJ Cho DG Rahman GM Marquez M Ou Z Kadish KM Guldi DM Sessler JL 《Journal of the American Chemical Society》2007,129(17):5683-5687