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991.
本文提供了自增强厚壁圆筒疲劳裂纹扩展寿命的可靠性分析的方法和公式,自增强残余应力用符合厚壁筒用钢具有强化和包辛格效应实际性能推得的公式进行计算,残余应力对应的应力强度因子的计算采用了有限元法,得到了工作内压与自增强残余应力共同作用下的厚壁筒应力强度因子公式,通过实验测定了厚壁筒用钢的断裂韧度和疲劳裂纹扩展速率等性能。 相似文献
992.
依据学习目标、教学活动、评价任务、成绩评定一体化设计的要求,研制中学化学实验试题,通过试题的测评结果开展教学反思,分析实验教学中存在的问题,改进实验教学模式,激活学生从化学实验中认识物质及其变化的好奇心和求知欲,诊断并发展学生的核心素养水平。 相似文献
993.
994.
Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of
materials, loading, and environmental conditions. A probabilistic approach for predicting the pitting corrosion fatigue life
has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages
of the corrosion fatigue process (i.e. the pit nucleation and growth, pit-crack transition, short- and long-crack propagation).
The probabilistic model investigated considers the uncertainties in the initial pit size, corrosion pitting current, and material
properties due to the scatter found in the experimental data. Monte Carlo simulations were performed to define the failure
probability distribution. Predicted cumulative distribution functions of fatigue life agreed reasonably well with the existing
experimental data.
The project supported by SRF for ROCS, State Education Ministry of China, and the Society for the Promotion of Science (JSPS)
of Japan (JSPS-P02042) 相似文献
995.
996.
该文采用约束背景双线性分解算法(CBBL)对以高效液相色谱(HPLC)方法分离分析的灰色分析体系进行了多元校正研究。针对采用包括CBBL在内的矩阵校正方法处理HPLC灰色分析体系的固有缺陷,即在相关组分的色谱保留时间重现性较低的情形下多元校正的结果不理想,对CBBL方法进行了改进,即将待测组分的浓度与组分的色谱保留时间同时作为优化的参量引入CBBL,并采用遗传算法(GA)优化CBBL,对于模拟的组分保留时间飘移严重的HPLC灰色分析体系及保留时间重现性不佳的多种酚类化合物组成的实际HPLC灰色分析体系进行了多元校正分析,成功克服了经典CBBL的固有缺陷,取得了较理想的多元校正结果。另外,该研究所建议的方法的校正结果也显著优于传统的残差双线性分解法(RBL)以及秩消失因子分析法(RAFA)。 相似文献
997.
Molecular Chirality in Meteorites and Interstellar Ices,and the Chirality Experiment on Board the ESA Cometary Rosetta Mission
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Iuliia Myrgorodska Dr. Cornelia Meinert Dr. Zita Martins Dr. Louis Le Sergeant d'Hendecourt Prof. Dr. Uwe J. Meierhenrich 《Angewandte Chemie (International ed. in English)》2015,54(5):1402-1412
Life, as it is known to us, uses exclusively L ‐amino acid and D ‐sugar enantiomers for the molecular architecture of proteins and nucleic acids. This Minireview explores current models of the original symmetry‐breaking influence that led to the exogenic delivery to Earth of prebiotic molecules with a slight enantiomeric excess. We provide a short overview of enantiomeric enhancements detected in bodies of extraterrestrial origin, such as meteorites, and interstellar ices simulated in the laboratory. Data are interpreted from different points of view, namely, photochirogenesis, parity violation in the weak nuclear interaction, and enantioenrichment through phase transitions. Photochemically induced enantiomeric imbalances are discussed more specifically in the topical context of the “chirality module” on board the cometary Rosetta spacecraft of the ESA. This device will perform the first enantioselective in situ analyses of samples taken from a cometary nucleus. 相似文献
998.
Dr. Neha P. Kamat Dr. Sylvia Tobé Ian T. Hill Prof. Jack W. Szostak 《Angewandte Chemie (International ed. in English)》2015,54(40):11735-11739
Cooperative interactions between RNA and vesicle membranes on the prebiotic earth may have led to the emergence of primitive cells. The membrane surface offers a potential platform for the catalysis of reactions involving RNA, but this scenario relies upon the existence of a simple mechanism by which RNA could become associated with protocell membranes. Here, we show that electrostatic interactions provided by short, basic, amphipathic peptides can be harnessed to drive RNA binding to both zwitterionic phospholipid and anionic fatty acid membranes. We show that the association of cationic molecules with phospholipid vesicles can enhance the local positive charge on a membrane and attract RNA polynucleotides. This phenomenon can be reproduced with amphipathic peptides as short as three amino acids. Finally, we show that peptides can cross bilayer membranes to localize encapsulated RNA. This mechanism of polynucleotide confinement could have been important for primitive cellular evolution. 相似文献
999.
光电信息工程实验教学的思考与改革 总被引:3,自引:2,他引:1
面对急剧变化的世界,工程知识本身的有效期变得越来越短,社会对学生各种素质的要求越来越高。如何定位大学工程教育本身的角色?如何在光电工程实验教学中培养社会对学生所提出的各种要求?结合对这些问题的思考,讨论了光电信息工程专业实验教学所面临的挑战,以及为应对这些挑战所进行的教学改革实践。 相似文献
1000.
Water-spray-cooled quasi-isothermal compressed air energy storage aims to avoid heat energy losses from advanced adiabatic compressed-air energy storage (AA-CAES). The compression efficiency increases with injection water spray. However, the energy-generated water spray cannot be ignored. As the air pressure increases, the work done by the piston and the work converted into heat rise gradually in the compression process. Accordingly, the flow rate of the water needed for heat transfer is not a constant with respect to time. To match the rising compression heat, a time sequence of water-spray flow rate is constructed, and the algorithm is designed. Real-time water-spray flow rate is calculated according to the difference between the compression power and heat-transfer power. Compared with the uniform flow rate of water spray, energy consumption from the improved flow rate is reduced. 相似文献