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991.
Munirathina Padmanaban Masa-Aki Kakimoto Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1990,28(6):1569-1578
1,2-Bis(p-aminophenyl)tetramethyldisilane was synthesized from 1,2-dichlorotetramethyldisilane and 4-[N,N-bis(trimethylsilyl)amino]phenyllithium. The diamine was reacted with various aromatic diacid chlorides giving disilane-containing aromatic polyamides (aramids), whose inherent viscosities were between 0.27 and 0.70 dL/g, depending on the diacid chlorides used. The aramids had glass transition temperatures between 194 and 255°C. No weight loss was observed below 350°C. Some of the polymers were found to be semicrystalline based on their x-ray diffractograms. The aramid films showed a strong ultraviolet (UV) absorption at 287 nm, which decreased during irradiation with UV light, suggesting that cleavage of the silicon-silicon bond in the aramid backbone occurs. A decrease in the inherent viscosity and molecular weight of the soluble aramid derived from phenylindanedicarbonyl chloride was also observed by irradiation with UV light. 相似文献
992.
We consider one-phase Stefan problems for the equation
u
i
=u
xx
+u
1+a
(>0)in one-dimensional space, which have blow-up solutions for a larger initial data. In this paper, the global existence result for our problem is proved by using energy inequalities. More precisely, if >1 an initial function is sufficiently small, then the free boundary is bounded and
decay in exponential order. 相似文献
993.
994.
995.
In a two-component columnar host system composed of racemic (rac)-1,2-diphenylethylenediamine and rac-1,1'-binaphthyl-2,2'-dicarboxylic acid, a cavity tuning mechanism resulted from changes in the structure of the columns using a specific combination of the following four molecules: (1R,2R)-1, (1S,2S)-1, (R)-2, and (S)-2. 相似文献
996.
Christian A. Sandoval Prof. Dr. Yuehui Li Kuiling Ding Prof. Dr. Ryoji Noyori Prof. Dr. 《化学:亚洲杂志》2008,3(10):1801-1810
Chiral binap/pica‐RuII complexes (binap=(S)‐ or (R)‐2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl; pica=α‐picolylamine) catalyze both asymmetric hydrogenation (AH) of ketones using H2 and asymmetric transfer hydrogenation (ATH) using non‐tertiary alcohols under basic conditions. The AH and ATH catalytic cycles are linked by the metal–ligand bifunctional mechanism. Asymmetric reduction of pinacolone is best achieved in ethanol containing the Ru catalyst and base under an H2 atmosphere at ambient temperature, giving the chiral alcohol in 97–98 % ee. The reaction utilizes only H2 as a hydride source with alcohol acting as a proton source. On the other hand, asymmetric reduction of acetophenone is attained with both H2 (ambient temperature) and 2‐propanol (>60 °C) with relatively low enantioselectivity. The degree of contribution of the AH and ATH cycles is highly dependent on the ketone substrates, solvent, and reaction parameters (H2 pressure, temperature, basicity, substrate concentration, H/D difference, etc.). 相似文献
997.
Perovskite-type lithium ionic conductors were explored in the (LixLa1−x/3)ScO3 system following their syntheses via a high-pressure solid-state reaction. Phase identification indicated that a solid solution with a perovskite-type structure was formed in the range 0 ≤ x < 0.6. When x = 0.45, (Li0.45La0.85)ScO3 exhibited the highest ionic conductivity and a low activation energy. Increasing the loading of lithium as an ionic diffusion carrier expanded the unit cell volume and contributed to the higher ionic conductivity and lower activation energy. Cations with higher oxidation numbers were introduced into the A/B sites to improve the ionic conductivity. Ce4+ and Zr4+ or Nb5+ dopants partially substituted the A-site (La/Li) and B-site Sc, respectively. Although B-site doping produced a lower ionic conductivity, A-site Ce4+ doping improved the conductive properties. A perovskite-type single phase was obtained for (Li0.45La0.78Ce0.05)ScO3 upon Ce4+ doping, providing a higher ionic conductivity than (Li0.45La0.85)ScO3. Compositional analysis and crystal-structure refinement of (Li0.45La0.85)ScO3 and (Li0.45La0.78Ce0.05)ScO3 revealed increased lithium contents and expansion of the unit cell upon Ce4+ co-doping. The highest ionic conductivity of 1.1 × 10−3 S cm−1 at 623 K was confirmed for (Li0.4Ce0.15La0.67)ScO3, which is more than one order of magnitude higher than that of the (LixLa1−x/3)ScO3 system. 相似文献
998.
Ryusei Hoshikawa Kosuke Yoshida Ryoji Mitsuhashi Masahiro Mikuriya Takashi Okuno Hiroshi Sakiyama 《Molecules (Basel, Switzerland)》2021,26(4)
Oxido bridges commonly form between iron(III) ions, but their bond angles and symmetry vary with the circumstances. A large number of oxido-bridged dinuclear iron(III) complexes have been structurally characterized. Some of them belong to the C2 point group, possessing bent Fe–O–Fe bonds, while some others belong to the Ci symmetry, possessing the linear Fe–O–Fe bonds. The question in this study is what determines the structures and symmetry of oxido-bridged dinuclear iron(III) complexes. In order to gain further insights, three oxido-bridged dinuclear iron(III) complexes were newly prepared with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) ligands: [Fe2OCl2(bpy)4][PF6]2 (1), [Fe2O(NO3)2(bpy)4][PF6]2·0.6MeCN·0.2(2-PrOH) (2), and [Fe2OCl2(phen)4][PF6]2·MeCN·0.5H2O (3). The crystal structures of 1, 2, and 3 were determined by the single-crystal X-ray diffraction method, and all of them were found to have the bent Fe–O–Fe bonds. Judging from the crystal structure, some intramolecular interligand hydrogen bonds were found to play an important role in fixing the structures. Additional density functional theory (DFT) calculations were conducted, also for a related oxido-bridged dinuclear iron(III) complex with a linear Fe–O–Fe bond. We conclude that the Fe–O–Fe bridge tends to bend like a water molecule, but is often stretched by interligand steric repulsion, and that the structures are mainly controlled by the intramolecular interligand interactions. 相似文献
999.
Y. Fukao M. Togawa A. Bazilevsky L.C. Bland A. Bogdanov G. Bunce A. Deshpande H. En'yo B.D. Fox Y. Goto J.S. Haggerty K. Imai W. Lenz D. von Lintig M.X. Liu Y.I. Makdisi R. Muto S.B. Nurushev E. Pascuzzi M.L. Purschke N. Saito F. Sakuma S.P. Stoll K. Tanida J. Tojo Y. Watanabe C.L. Woody 《Physics letters. [Part B]》2007,650(5-6):325-330
In the 2001–2002 running period of the Relativistic Heavy Ion Collider (RHIC), transversely polarized protons were accelerated to 100 GeV for the first time, with collisions at . We present results from this run for single transverse-spin asymmetries for inclusive production of neutral pions, photons and neutrons of the energy region 20–100 GeV for forward and backward production for angles between 0.3 mrad and 2.2 mrad with respect to the polarized proton direction. An asymmetry of was observed for forward neutron production, where the errors are statistical and systematic, and the scale error is from the beam polarization uncertainty. The forward photon and π0, and backward neutron, photon, and π0 asymmetries were consistent with zero. The large neutron asymmetry indicates a strong interference between a spin–flip amplitude, such as one pion exchange which dominates lower energy neutron production, and remaining spin–non-flip amplitudes such as reggeon exchange. 相似文献
1000.
Imai Y Kido S Kamon K Kinuta T Sato T Tajima N Kuroda R Matsubara Y 《Organic letters》2007,9(24):5047-5050
A charge-transfer (CT) complex, composed of 10,10'-dihydroxy-9,9'-biphenanthryl as the electron donor and 1,1'-dimethyl-4,4'-bipyridinium dichloride as the electron acceptor, is formed only by the inclusion of guest molecules. The color of this inclusion CT complex is sensitive to the component guest molecules. 相似文献