全文获取类型
收费全文 | 10092篇 |
免费 | 1694篇 |
国内免费 | 1300篇 |
专业分类
化学 | 6427篇 |
晶体学 | 225篇 |
力学 | 527篇 |
综合类 | 83篇 |
数学 | 506篇 |
物理学 | 5318篇 |
出版年
2024年 | 27篇 |
2023年 | 87篇 |
2022年 | 208篇 |
2021年 | 252篇 |
2020年 | 319篇 |
2019年 | 314篇 |
2018年 | 311篇 |
2017年 | 316篇 |
2016年 | 423篇 |
2015年 | 374篇 |
2014年 | 415篇 |
2013年 | 1236篇 |
2012年 | 571篇 |
2011年 | 651篇 |
2010年 | 507篇 |
2009年 | 642篇 |
2008年 | 615篇 |
2007年 | 573篇 |
2006年 | 593篇 |
2005年 | 544篇 |
2004年 | 491篇 |
2003年 | 480篇 |
2002年 | 407篇 |
2001年 | 295篇 |
2000年 | 365篇 |
1999年 | 283篇 |
1998年 | 209篇 |
1997年 | 198篇 |
1996年 | 203篇 |
1995年 | 140篇 |
1994年 | 165篇 |
1993年 | 131篇 |
1992年 | 115篇 |
1991年 | 100篇 |
1990年 | 74篇 |
1989年 | 67篇 |
1988年 | 54篇 |
1987年 | 36篇 |
1986年 | 48篇 |
1985年 | 43篇 |
1984年 | 47篇 |
1983年 | 10篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
V. E. Diyuk V. G. Gerasyova T. N. Bezuglaya V. K. Yatsimirskii 《Theoretical and Experimental Chemistry》2008,44(4):252-259
A study was carried out on the effect of electrolytes KCl, CaCl2, MnCl2, ZnCl2, CuCl2, KNO3, Ca(NO3)2, Mn(NO3)2, Zn(NO3)2, and Cu(NO3)2 on the kinetics of the decomposition of H2O2 catalyzed by [Cu(L1/L2)][MCl4] complexes (M = Zn, Mn; L1 is 4,6,6-trimethyl-1,9-diamino-3,7-diaza-3-nonene, L2 is 1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetraaza-6-pentadecene). The chloride ions were found to reversibly inhibit the
catalyst. The major kinetic characteristics of this reaction were obtained using a mathematical model taking account of the
reversible and irreversible inhibition of the catalyst.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 4, pp. 240–247, July–August, 2008. 相似文献
992.
J. Betzabe Gonzlez‐campos Evgen Prokhorov Gabriel Luna‐Brcenas A. Mendoza Galvn Isaac C. Sanchez Sergio M. Nuo Donlucas B. Garcia‐Gaitan Yuriy Kovalenko 《Journal of Polymer Science.Polymer Physics》2009,47(9):932-943
Relaxations in chitin have been investigated in the temperature range 298–523 K using impedance spectroscopy in the frequency range 10−1–108 Hz. The objective was to detect a glass‐transition temperature for this naturally occurring, semicrystalline polysaccharide. The impedance study was complemented with X‐ray diffraction, thermogravimetric, and differential scanning calorimetry measurements. Preliminary impedance data treatment includes the subtraction of the dc conductivity contribution, the exclusion of contact and interfacial polarization effects, and obtaining a condition of minimum moisture content for further analysis. When all these aspects are taken into account, two relaxations are clearly revealed in the impedance data. For the first time, evidence is presented for a relaxation process, which exhibits a non‐Arrhenius temperature dependence, in dry α‐chitin (∼0.1% moisture content), and likely represents the primary α‐relaxation. This evidence suggests a glass transition temperature for chitin of 335 ± 10 K estimated on the basis of the temperature dependence of the conductivity and of the relaxation time. A second relaxation in dry α‐chitin, not previously reported in the literature, is observed from 353 K to the onset of thermal degradation (∼483 K) and is identified as the σ‐relaxation often associated with proton mobility. It exhibits a normal Arrhenius‐type temperature dependence with activation energy of 113 ± 3 kJ/mol. The latter has not been previously reported in the literature. A high frequency secondary β‐relaxation is also observed with Arrhenius activation energy of 45 ± 1 kJ/mol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 932–943, 2009 相似文献
993.
W. Stadje 《Queueing Systems》1989,4(1):85-92
For a M/M/1 queueing system with group arrivals of random size the transition probabilities of the queue size process and the distribution of the maximal queue size during a time interval [0,t) are calculated. Simple formulae for the corresponding Laplace transforms are given. 相似文献
994.
995.
The phase state of dense matter in the intermediate density range (\begin{document}$\sim$\end{document} ![]()
![]()
1-10 times the nuclear saturation density) is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron stars. As matter density increases in compact stars, the sound velocity is expected to approach the conformal limit (\begin{document}$c_s/c=1/\sqrt{3}$\end{document} ![]()
![]()
) at high densities and should also fulfill the causality limit (\begin{document}$c_s/c<1$\end{document} ![]()
![]()
). However, its detailed behavior remains a prominent topic of debate. It was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition, where a particular shape might be expected for its density dependence. In this work, we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark stars. Various conditions are employed for the hadron-quark phase transition with varying interface tension. We find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase, in addition to a deconfinement phase transition. Moreover, it leads to a more compact star with a similar mass. We then propose a new class of quark star equation of states, which can be tested by future high-precision radius measurements of pulsar-like objects. 相似文献
996.
Modeling a causal association as arising from a communication process between cause and effect, simplifies the discovery of causal skeletons. The communication channels enabling these communication processes, are fully characterized by stochastic tensors, and therefore allow us to use linear algebra. This tensor-based approach reduces the dimensionality of the data needed to test for conditional independence, e.g., for systems comprising three variables, pair-wise determined tensors suffice to infer the causal skeleton. The only thing needed is a minor extension to information theory, namely the concept of path information. 相似文献
997.
《中国物理 B》2021,30(6):67402-067402
The geometrically frustrated iridate La_3Ir_3O_(11) with strong spin–orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematically investigate the evolution of structural and electronic properties of La_3Ir_3O_(11) under high pressure. Electrical transport measurements reveal an abnormal insulating behavior rather than metallization above a critical pressure P_c ~ 38.7 GPa. Synchrotron x-ray diffraction(XRD)experiments indicate the stability of the pristine cubic KSbO_3-type structure up to 73.1 GPa. Nevertheless, when the pressure gradually increases across P_c, the bulk modulus gets enhanced and the pressure dependence of bond length d_(Ir-Ir) undergoes a slope change. Consistent with the XRD data, detailed analyses of Raman spectra reveal an abnormal redshift of Raman mode and a change of Raman intensity around P_c. Our results demonstrate that the pressure-induced insulating behavior in La_3Ir_3O_(11) can be assigned to the structural modification, such as the distortion of IrO_6 octahedra. These findings will shed light on the emergent abnormal insulating behavior in other 5 d iridates reported recently. 相似文献
998.
Equilibrium folding and unfolding dynamics to reveal detailed free energy landscape of src SH3 protein by magnetic tweezers 下载免费PDF全文
《中国物理 B》2021,30(7):78201-078201
Src SH3 protein domain is a typical two-state protein which has been confirmed by research of denaturant-induced unfolding dynamics. Force spectroscopy experiments by optical tweezers and atomic force microscopy have measured the force-dependent unfolding rates with different kinds of pulling geometry. However, the equilibrium folding and unfolding dynamics at constant forces has not been reported. Here, using stable magnetic tweezers, we performed equilibrium folding and unfolding dynamic measurement and force-jump measurement of src SH3 domain with tethering points at its N-and C-termini. From the obtained force-dependent transition rates, a detailed two-state free energy landscape of src SH3 protein is constructed with quantitative information of folding free energy, transition state barrier height and position,which exemplifies the capability of magnetic tweezers to study protein folding and unfolding dynamics. 相似文献
999.
Fabrication and characterization of Al–Mn superconducting films for applications in TES bolometers 下载免费PDF全文
《中国物理 B》2021,30(7):77402-077402
Superconducting transition edge sensor(TES) bolometers require superconducting films to have controllable transition temperatures T_c in different practical applications.The value of T_c strongly affects thermal conductivity and thermal noise performance of TES detectors.Al films doped with Mn(Al-Mn) of different concentrations can accomplish tunable T_(c.)A magnetron sputtering machine is used to deposit the Al-Mn films in this study.Fabrication parameters including sputtering pressure and annealing process are studied and their influences on T_c and superconducting transition width ΔT_c are optimized.The Al-Mn films with ΔT_c below 1.0 mK for T_c in a range of 520 mK-580 mK are successfully fabricated. 相似文献
1000.
《中国物理 B》2021,30(6):66701-066701
Floquet theorem is widely used in the light-driven systems. But many 2 D-materials models under the radiation are investigated with the high-frequency approximation, which may not be suitable for the practical experiment. In this work,we employ the non-perturbative Floquet method to strictly investigate the photo-induced topological phase transitions and edge states properties of graphene nanoribbons under the light irradiation of different frequencies(including both low and high frequencies). By analyzing the Floquet energy bands of ribbon and bulk graphene, we find the cause of the phase transitions and its relation with edge states. Besides, we also find the size effect of the graphene nanoribbon on the band gap and edge states in the presence of the light. 相似文献