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121.
陈文华 《数学的实践与认识》2009,39(7)
求元素为1或-1的n阶行列式的最大值问题至今还没有得到解决,试图解决这个问题.首先把该问题转化为求元素为0或1的n-1阶行列式的最大值问题,接着给出了用取值较大的k-1阶行列式构造取值较大的k阶行列式的一种方法,并利用这种方法分别求出了元素为1或-1的3阶至8阶行列式的最大值. 相似文献
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An approach of realizing high performance HTS coil comprised of ferromagnetic material-coated BSCCO tape is proposed. The concept of influencing critical current and ac loss is based on the magnetic shielding effect resulting in redirection of self-field flux-lines. In the previous article, ac performance of Ni-coated tape was demonstrated where the Ni-coating was introduced at the edge-regime of the finished tape in order to redirect the perpendicular component of self-field lines. In order to investigate the shielding effect on ac performance in HTS coil, a two-turn pancake coil comprised of Ni-coated Bi-2223/Ag tape is demonstrated in the present article. About 6.4% of critical current was enhanced and 30% of transport current ac loss was reduced by means of 40 μm thick and 0.3 mm long (from the edge toward center of the tape) Ni-coating. This result suggests that additional ferromagnetic loss could be compensated well by the shielding effect of the partial Ni-coating. The degree of enhancement in critical current as well as ferromagnetic impact on ac losses depend on the volume and geometry of ferromagnetic coating introduced. Therefore, it is very important to control the parameter of ferromagnetic coating of the tape in order to balance the critical current and ac loss for optimum coil performance. 相似文献
125.
Ag是目前唯一不需要隔离层的高温超导基带材料,而且研究表明,在YBCO中掺入适量的Ag,将有利于超导性能的改善和表面电阻的降低.本研究采用准分子激光法(PLD),在经不同表面处理的{110}〈110〉取向的双轴织构银基带上直接沉积了YBCO薄膜,得到了强双轴织构的超导膜,系统地研究了银基带中的孪晶、晶界等缺陷对YBCO超导微观组织的影响. 相似文献
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Duyen Minh Pham Yasushi Miyata Takanori Awata Masashi Nakatake Chung Fang Zhang Keiji Kanda Satoshi Ogawa Shozo Ohta Shinya Yagi Arata Katayama 《Surface and interface analysis : SIA》2019,51(2):226-233
Carbon-binding state of humin (HM, a non-conductive insoluble organo-mineral humic substance) was successfully characterized for the first time by synchrotron-radiation–based X-ray photoelectron spectroscopy (XPS). Four sample preparation techniques—HM on double-sided carbon tape, indium sheet, copper mesh, and in pellet formed from the mixture of HM and copper powder (Cu) at different mixing ratios (1:1, 1:2, and 1:6 v/v)—were compared. The results show that HM samples prepared using the first three methods had significant charge buildup, which made the interpretation of the XPS spectra impossible because of the shifts in the binding energy of C 1s XPS spectra. Pellets of HM:Cu mixture enhanced the electrical conductivity and reduced charge buildup on the sample surface. Pellets prepared with HM:Cu ratio of 1:1 (v/v) provided the minimum charge buildup and high sensitivity with difference in C 1s spectra regardless of the observing position. The C 1s spectra, estimated by the subtraction of the carbon contamination in Cu, showed the resolution of CC (284.0 eV), C C/C H (285.1 eV), C O (286.3 eV), CO (287.3 eV), and OC O (288.3 eV) and three additional peaks of CF (289.3 eV), CF2 (290.2 eV), and CF3 (291.4 eV). Soft X-ray absorption spectroscopic (XAS) analysis further proved the existence of fluoride (F 1s) in HM structure. The detection of fluorinated carbon in HM showed a great advancement of XPS compared with other conventional analyses. X-ray with the incident angle of 0° provided the smallest (nearly negligible) energy shift in the C 1s spectra of HM and did not damage the surface of the sample. 相似文献
128.
A. Şakar-Deliormanı E. Çelik M. Polat 《Journal of Thermal Analysis and Calorimetry》2008,94(3):663-667
In this study, aqueous lead magnesium niobate (PMN) slurry formulations were developed for tape casting using a poly(acrylic
acid) - poly(ethylene) oxide comb polymer as the dispersant, nonionic acrylic latex as the binder phase and hydroxypropyl
methylcellulose as the wetting agent. Concentrated suspensions were cast onto a silicone-coated mylar film, and the effect
of acrylic latex on deposition was investigated.
Thermal analyses were performed to investigate the mass loss of the green tapes as a function of calcination temperature.
Differential scanning calorimetric analyses were made under air and nitrogen atmospheres to investigate the binder distribution
through the green tapes. Results showed that it is possible to prepare flexible, crack free PMN thick films using a proper
slurry composition in the presence of acrylic latex binder, without using any plasticizer. Additionally, decomposing mechanisms
of the acrylic based binder were essentially different in the two atmospheres. 相似文献
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At present longitudinal magnetic recording systems are the basis of all low cost high-density information storage systems. During the recent past the data density stored on rigid disk media which is the higher density format have increased at the rate of 60% per annum compound. However, very recently due to the introduction of new advanced GMR spin-valve heads this rate of advance has increased to 100% per annum in laboratory demonstrations. Hence, it is pertinent at this time to enquire as to where the fundamental physical limitations of longitudinal magnetic recording may lie. In this context there are two principle areas of interest: the first of these is limitations to data rate. These are concerned with the fundamental physics of the maximum rate at which a magnetic moment may reverse from one direction to the other. The theoretical calculation of these limits is complex and not well understood but the limits of our understanding will be reviewed in this paper. Secondly, and of principle concern is the limit to the density at which information can be stored in a magnetic thin film. This latter limitation is based around the signal to noise ratio and also the question of the stability of increasingly small written bits. Signal to noise considerations are extremely complex and derive from factors such as the shape of bits and cross-talk between neighbouring bits or even neighbouring tracks. In this article the fundamental origins of noise will be reviewed in terms of the basic physics that gives rise to variation in transition shapes. Cross-talk and cross-track interference will not be discussed as these are generally addressed through issues associated with the resolution of the servo-mechanism that positions the head above a track and is not associated with the fundamental physics of the medium itself. Thermal stability of a bit of information is of critical importance particularly as media is made ever thinner and will form a major aspect of the discussion in this work. Finally, possible material physics solutions to some of these limitations will be presented in terms of measurable parameters which to some limited degree may be controlled by process conditions. 相似文献