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141.
Chemisorption of 1,1-dichloroethene (Cl2CCH2) to a Si(1 1 1)-7 × 7 surface was studied by means of X-ray photoelectron spectroscopy using synchrotron radiation, recording chlorine 2p and carbon 1s spectra. For carbon 1s, spectral assignment of the chemisorbed species is based on quantum chemical calculations of chemical shifts in model compounds.The results confirm the identity of covalently bonded 1-chlorovinyl (-CClCH2) and vinylidene (CCH2) adspecies. Upon chemisorption at room temperature it was found that about one-third of the molecules break one C-Cl bond while about two-thirds of the adsorbates break two C-Cl bonds. We do not, however, find evidence for isomerization of CCH2 to di-bonded vinylene (-CHCH-). 相似文献
142.
The CO2-broadened water coefficients (half-widths, line shifts, and temperature dependence of the widths) are predicted using a fully complex Robert-Bonamy formulation for the 937 allowed and forbidden perpendicular type transitions of (000)-(000) between 200 and 900 cm−1 in order to facilitate atmospheric remote sensing of Mars and Venus. In addition, empirical Lorentz line widths and pressure-induced frequency-shifts of CO2-broadened H216O are obtained at room temperature for 257 perpendicular transitions of the (010)-(000) fundamental. For this, calibrated spectra recorded at 0.0054 cm−1 resolution are measured assuming Voigt line shapes. For transitions between 1287 and 1988 cm−1 with rotational quanta up to J = 13 and Ka = 6, the widths vary from 0.045 to 0.212 cm−1 atm−1 at 300 K; the pressure-shifts are quite large and range from −0.0386 to +0.0436 cm−1 atm−1. For the (010)-(000) band, the RMS and mean observed and calculated differences for CO2-broadened H2O half-widths are 12% and −1.9%, respectively, while the RMS and mean ratios of the observed and calculated pressure-induced shift coefficients are 1.6 and 0.79, respectively. For pairs of transitions involving Ka = 0 and 1, such as 20 2 ← 31 3 and 31 3 ← 20 2, both the calculated and observed pressure induced shifts in positions are opposite in sign and often similar in magnitude. The data are too limited to characterize vibrational dependencies of the widths, however. 相似文献
143.
Piotr Matczak 《Molecular physics》2017,115(3):364-378
In this work, extensive quantum-chemical calculations have been carried out to identify and elucidate trends in the hydrogen-bonding (HB) interaction involving halogen acceptors covalently bonded to a group 14 atom. A series of 25 heterodimers composed of MH3X (where M = C?Pb and X = F?At) and HNC molecules have been selected as model complexes stabilised by the HB interaction occurring between the X atom of MH3X and the H atom of HNC. The interaction energy (Eint) between MH3X and HNC in the MH3X···HNC complexes falls in the range from ?2.7 to ?10.8 kcal/mol, indicating weak or medium strength of HB in these complexes. The strength of HB in the complexes remains consistent with the well-known HB weakening as X gets heavier. Regarding the effect of M on Eint, the gradual strengthening of HB is observed while descending group 14, but only from M = Si to M = Pb. The trends in Eint are compared with various HB-related parameters obtained from vibrational analysis, the natural bond orbital (NBO) method, the symmetry-adapted perturbation theory (SAPT) and the quantum theory of atoms in molecules (QTAIM). The parameters that present clear (possibly linear) relationships with Eint have been selected to characterise the effect of M and X on the HB interaction. 相似文献
144.
145.
Infrared reflection absorption spectroscopy that used buried metal layer substrates (BML-IRRAS) and density functional cluster calculations were employed to investigate the water related oxidation reactions of 2H + H2O/Si(1 0 0)-(2 × 1), 2D + H2O/Si(1 0 0)-(2 × 1), and H2O + H/Si(1 0 0)-(2 × 1). In addition to the oxygen inserted coupled monohydrides, which were previously reported in the former reaction system, we report several other oxidized Si hydride species in our BML-IRRAS experiments. Three new pairs of vibrational bands are identified between 900 and 1000 cm−1. These vibrational frequencies were calculated using Si9 and Si10 cluster models that included all possible structures from zero to five oxygen insertions into the top layer silicon atoms using a B3LYP gradient corrected density functional method with a polarized 6-31G** basis set for all atoms. The three pairs of vibrational modes are assigned to the scissoring modes of adjacent and isolated SiH2 with zero, one, and two oxygen atoms inserted into the Si back bonds. All the other newly observed vibrational peaks related to Si oxidation are also assigned in this study. The Si-O stretching bands observed in the reaction 2D + H2O/Si(1 0 0)-(2 × 1) show an isotope effect, which suggests that in the system 2H + H2O/Si(1 0 0)-(2 × 1) also, hydrogen atom tunneling plays an important role for the insertion of oxygen atoms into Si back bonds that form oxidized adjacent dihydrides. 相似文献
146.
Hailin LiuZhihong Lu ling YueJing Liu Zhanghua GanChang Shu Ting ZhangJing Shi Rui Xiong 《Applied Surface Science》2011,257(22):9355-9361
A series of Ti1−xMoxO2−yNy samples were prepared by using sol-gel method and characterized by X-ray diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. All Ti1−xMoxO2−yNy samples are anatase phase. It is found that Mo, N mono-doping can increase visible light absorption, while (Mo + N) co-doping can greatly enhance absorption in whole visible region. Results of our first-principles band structure calculations reveal that (Mo + N)-doping, especially passivated co-doping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO2, which leads to a greatly increase of its visible-light absorption without a decrease of its redox potential. It reveals that (Mo + N) co-doped TiO2 is promising for a photocatalyst with high photocalystic activity under visible light. 相似文献
147.
The possibilities of magnetism induced by intrinsic defects and nitrogen substitution in (5,5) single-wall SnO2 nanotube are investigated by ab initio calculations. The calculated results indicate that a stoichiometric SnO2 nanotube is nonmagnetic. The tin (Sn) vacancy can induce the magnetic moments rather than oxygen vacancy, which is originated from the polarization of O 2p electrons. A couple of tin vacancies can lead to the ferromagnetic coupling. A nitrogen substitution for oxygen also produces magnetic moments. When substituting two nitrogen atoms, the characteristics of exchange coupling depend upon the distance of two nitrogen atoms. The longer distance of two nitrogen atoms prefers the ferromagnetic coupling, whereas the short distance leads to the antiferromagnetic coupling. 相似文献
148.
采用第一性原理计算方法,通过在单层GeSe上施加双轴向应变、外加电场、掺Ag等途径来探索提高单层GeSe对H2O分子传感性能的有效方法,并从微观角度阐明内在机理.计算结果表明,-1.0 V/?的外加电场能有效降低H2O分子在单层GeSe的吸附能并使二者之间的电荷转移量增加11倍,显著提高了单层GeSe对H2O分子的响应速度和敏感性.研究结果为进一步设计并制成二维GeSe基湿度传感器提供了理论依据. 相似文献
149.
M. Koll R. Ricken D. Merten B.C. Metsch H.R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):73-94
We present new results of a relativistic quark model based on the Bethe-Salpeter equation in its instantaneous approximation.
Assuming a linearly rising confinement potential with an appropriate spinorial structure in Dirac space and adopting a residual
interaction based on instanton effects, we can compute masses of the light mesons up to highest observed angular momenta with
a natural solution of the U
A(1) problem. The calculated ground states masses and the radial excitations describe the experimental results well. In this
paper, we will also discuss our results concerning numerous meson decay properties. For processes like π+/K
+↦e
+υeγ and 0-↦γγ at various photon virtualities, we find a good agreement with experimental data. We will also comment on the form factors
of the K
?3 decay and on the decay constants of the π, K and η mesons. For the sake of completeness, we will furthermore present the electromagnetic form factors of the charged π
and K mesons as well as a comparison of the radiative meson decay widths with the most recent experimental data.
Received: 28 August 2000 / Accepted: 12 September 2000 相似文献
150.
Andréi Zaitsevskii Elena Rykova Nikolai S. Mosyagin Anatoly V. Titov 《Central European Journal of Physics》2006,4(4):448-460
The relativistic effective core potential (RECP) approach combined with the spin-orbit DFT electron correlation treatment
was applied to the study of the bonding of eka-mercury (E112) and mercury with hydrogen and gold atoms. Highly accurate small-core
shape-consistent RECPs derived from Hartree-Fock-Dirac-Breit atomic calculations with Fermi nuclear model were employed. The
accuracy of the DFT correlation treatment was checked by comparing the results in the scalar-relativistic (spin-orbit-free)
limit with those of high level scalar-relativistic correlation calculations within the same RECP model. E112H was predicted
to be slightly more stable than its lighter homologue (HgH). The E112-Au bond energy is expected to be ca. 25–30 % weaker
than that of Hg-Au. The role of correlations and magnetic (spin-dependent) interactions in E112-X and Hg-X (X=H, Au) bonding
is discussed. The present computational procedure can be readily applied to much larger systems and seems to be a promising
tool for simulating E112 adsorption on metal surfaces. 相似文献