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991.
Takashi Iwatsubo Toshio Masuoka Kensaku Mizoguchi 《Journal of Polymer Science.Polymer Physics》1994,32(1):1-6
Pervaporation of a water/alcohol mixture through a membrane which has ion-exchange capacity has been investigated. Theoretical equations are introduced which relate the degree of ionic dissociation of the polymer to quantities of water and alcohol dissolved in the polymer. From these equations, an equation for selective dissolution R is derived which does not contain an explicit term for ionic dissociation. Dissociation affects selective dissolution only by changing the degree of swelling of the polymer. Reformulating R asymptotically obtains a reciprocal relationship between permselectivity and permeability for a water-selective membrane. Experiments to check the validity of the relationship have been carried out using chitosan membranes neutralized by several acids. The effect of degree of neutralization also has been investigated. Results can be well understood on the supposition that ionic dissociation depends upon the water/alcohol composition, the kind of acid, and the degree of neutralization. Experimental results indicate that the reciprocal relationship is maintained over an appropriate range of feed compositions which confirm the validity of the theoretical equations for the swelling equilibrium of an ionic membrane. © 1994 John Wiley & Sons, Inc. 相似文献
992.
信元在 ATM 网内传输时,由于网内缓存的存在,造成了信元延时变化。信元延时变化对基于锁相环(PLL)的恒定比特率业务时钟的恢复有很大影响,即时钟的抖动和漂移比较明显。从而使这种基于 PLL 的CBR 业务时钟恢复方案在某些场合不能应用。本文提出了一种基于 PLL 的时钟恢复新方案,该方案可以明显地降低由于信元延时变化而造成的 CBR 业务时钟的抖动和漂移,同时不增加缓存的容量。 相似文献
993.
本文探讨了修改排序网实现信元淘汰的方法(简称B网)。比较了B网和[1]中淘汰网(简称K网)的复杂性和时延。给出了集线比λ=L/N的临界值λ0(N),并证明当λ>λ0(N)时B网有较小复杂性和较小时延。 相似文献
994.
设计与制备了带Ti/Au膜参考电极的长臂式pH-ISFET集成传感器与微流通池。在静态和流动分析系统测量中表明:由蠕动泵驱动的待测液流动极畅,且试样量极少,响应速度快。 相似文献
995.
The selective detection of CO gas by stannic oxide incorporated with ThO2(l − 10 wt%), in the presence of H2 and petroleum
gases such as C3H8 and iso-C4H2 has been studied. Materials mixed with 5 wt% ThO2 showed high selectivity to CO gas at a sample temperature of 200−250‡C. The effects of hydrophobic or hydrophilic silica
present in the samples on the detection sensitivity to CO gas have been investigated. From the results it is apparent that
the removal of the hy-droxyl radical from the surface of SnO2 enhances the sensitivity to CO gas. 相似文献
996.
997.
It is proposed in this paper to use the generalized cell mapping to locate strange attractors of dynamical systems and to determine their statistical properties. The cell-to-cell mapping method is based upon the idea of replacing the state space continuum by a large collection of state space cells and of expressing the evolution of the dynamical system in terms of a cell-to-cell mapping. This leads to a Markov chain which in turn allows us to compute all the statistical properties as well as the invariant distribution. After a general discussion, the method is applied in this paper to strange attractors of a variety of systems governed either by point mappings or by differential equations. The results indicate that it is a viable, effective and attractive method. Some comments on this method in comparison with the method of direct iteration will also be made. 相似文献
998.
The G-protein-coupled receptor (GPCR) superfamily represents one of the largest classes of molecules involved in signal transduction
across the plasma membrane. Fluorescence-based approaches have provided valuable insights into GPCR functions such as receptor–receptor
and receptor–ligand interactions, real-time assessment of signal transduction, receptor dynamics on the plasma membrane, and
intracellular trafficking of receptors. This has largely been possible with the use of fluorescent probes such as the green
fluorescent protein (GFP) from the jellyfish Aequoria victoria and its variants. We discuss the potential of fluorescence-based approaches in providing novel information on the membrane
organization and dynamics of the G-protein-coupled serotonin1A receptor tagged to the enhanced yellow fluorescent protein (EYFP).
These authors contributed equally to the work. 相似文献
999.
Roehrl MH Heffron GJ Wagner G 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2005,174(2):325-330
Spin state selective experiments have become very useful tools in solution NMR spectroscopy, particularly in the context of TROSY line narrowing. However, the practical implementation of such pulse sequences is frequently complicated by unexpected instrument behavior. Furthermore, a literal theoretical analysis of sequences published with specific phase settings can fail to rationalize such experiments and can seemingly contradict experimental findings. In this communication, we develop a practical approach to this ostensible paradox. Spin-dynamic design, rationalization, and simulation of NMR pulse sequences, as well as their confident and reliable implementation across current spectrometer hardware platforms, require precise understanding of the underlying nutation axis conventions. While currently often approached empirically, we demonstrate with a simple but general pulse program how to uncover these correspondences a priori in the general case. From this, we deduce a correspondence table between the spin-dynamic phases used in NMR theory and simulation on the one hand and pulse program phases of current commercial spectrometers on the other. As a practical application of these results, we analyze implementations of the original (1)H-(15)N TROSY experiment and illustrate how steady-state magnetization can be predictably, rather than empirically, added to a desired component. We show why and under which circumstances a literal adoption of phases from published sequences can lead to incorrect results. We suggest that pulse sequences should be consistently given with spin-dynamically correct (physical) phases, rather than in spectrometer-specific (software) syntax. 相似文献
1000.