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991.
Ramiro Pino Olivier Bokanowski Eduardo V. Ludeña Roberto López Boada 《Theoretical chemistry accounts》2007,118(3):557-561
Bearing in mind the insight into the Hohenberg–Kohn theorem for Coulomb systems provided recently by Kryachko (Int J Quantum
Chem 103:818, 2005), we present a re-statement of this theorem through an elaboration on Lieb’s proof as well as an extension
of this theorem to finite subspaces.
Contribution to the Serafin Fraga Memorial Issue. 相似文献
992.
稀土电解槽的研究现状及发展趋势 总被引:1,自引:0,他引:1
综述了国内外稀土电解槽的类型和特点,国内在稀土电解槽的电场、磁场、流场、熔盐性质、工艺条件、电阻常数以及电解槽的热平衡和电极材料等方面的研究现状。提出了槽电压与结构参数之间的关系以及结构参数的优化设计方法,根据槽容量进行优化设计可显著降低槽电压,达到节能降耗的目的。 相似文献
993.
Carolina A. Pinto P. M. Büchler J. Dweck 《Journal of Thermal Analysis and Calorimetry》2007,87(3):715-720
The catalyst
used in fluidized catalytic cracking (FCC) units of refineries after several
recovery cycles in regeneration units, reduces its activity and it is partially
substituted by new catalyst in the process. As it has a high silicon and aluminum
oxides content, the pozzolanic properties of a Brazilian FCC spent residual
catalyst, used in different substitution degrees to cement, were evaluated
by three thermal analysis techniques during the early stages of hydration
of a type II Portland cement. NCDTA curves show in real time that the residual
catalyst, accelerates the stages of cement hydration. TG and DSC curves of
respective pastes after 24 h of hydration evidence the pozzolanic activity
of the waste, respectively, by the lower water mass loss during the dehydroxylation
of the residual calcium hydroxide and by the lower dehydroxylation endothermal
effect. Within the analyzed period, the higher is the cement substitution
degree, the higher is the pozzolanic activity of the residual catalyst. 相似文献
994.
Changlun Chen Di Xu Xiaoli Tan Xiangke Wang 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(1):227-233
The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions.
The extent of sorption of divalent metal cations is controlled by a number of factors including cosorbing or complexing. In
this work, the effects of pH, humic acid HA/Co(II) addition orders, ionic strength, concentration of HA, and foreign cations
on the Co(II) sorption on γ-Al2O3 in the presence of HA were investigated. The sorption isotherms of Co(II) on γ-Al2O3 in the absence and presence HA were also studied and described by using S-type sorption model. The experimental results showed
that the Co(II) sorption is strongly dependent on the pH values, concentration of HA, but independent of HA/Co(II) addition
orders, ionic strength, and foreign cations in the presence of HA under our experimental conditions. The results also indicated
that HA enhanced the Co(II) sorption at low pH, but reduced the Co(II) sorption at high pH. It was hypothesized that the significantly
positive influence of HA at low pH on the Co(II) sorption on γ-Al2O3 was attributed to strong surface binding of HA on γ-Al2O3 and subsequently the formation of ternary surface complexes such as ≡S-OOC-R-(COO−)
x
Co2−x
. Chemi-complexation may be the main mechanism of the Co(II) sorption on γ-Al2O3 in the presence of HA. 相似文献
995.
一类新的毛细管气相色谱固定液—侧链液晶冠醚聚硅氧烷的研究 总被引:7,自引:0,他引:7
合成了一种新的毛细管气相色谱用固定液——侧链含冠醚液晶的聚硅氧烷,这种固定液易于涂渍在弹性石英毛细管柱上,柱效高,热稳定性好,极性中等,它具有高分子液晶和高分子冠醚固定液的双重保留性能,适于分离多种异构体。 相似文献
996.
997.
We herein report a denitrogenative palladium-catalyzed cascade for the modular and regioselective synthesis of polysubstituted fluorenes. Hydrazone facilitates the Pd(ii) to Pd(iv) oxidative addition in a Catellani pathway and is also the methylene synthon in the proposed reaction. Aryl iodides and 2-bromoarylaldehyde hydrazones undergo a norbornene-controlled tandem reaction sequence to give a broad scope of fluorenes in the presence of a palladium catalyst. The method described is scalable and adaptable to a three-component reaction with in situ generation of the hydrazone group. Preliminary mechanistic investigations have been conducted.Hydrazone assists Pd(ii)/(iv) oxidative addition and is the methylene synthon in a palladium-catalyzed, norbornene-mediated regioselective synthesis of fluorenes. 相似文献
998.
Zhen-Qiang Yu Xiaodong Li Wei Wan Xin-Shun Li Kuo Fu Yue Wu Alexander D. Q. Li 《Chemical science》2021,12(9):3146
Balancing the rigidity of a π-conjugated structure for strong emission and the flexibility of liquid crystals for self-assembly is the key to realizing highly emissive liquid crystals (HELCs). Here we show that (1) integrating organization-induced emission into dual molecular cooperatively-assembled liquid crystals, (2) amplifying mesogens, and (3) elongating the spacer linking the emitter and the mesogen create advanced materials with desired thermal–optical properties. Impressively, assembling the fluorescent acceptor Nile red into its host donor designed according to the aforementioned strategies results in a temperature-controlled Förster resonance energy transfer (FRET) system. Indeed, FRET exhibits strong S-curve dependence as temperature sweeps through the liquid crystal phase transformation. Such thermochromic materials, suitable for dynamic thermo-optical sensing and modulation, are anticipated to unlock new and smart approaches for controlling and directing light in stimuli-responsive devices.A temperature-sensitive Förster resonance energy transfer system was constructed using a highly emissive liquid crystal co-assembled with Nile red, enabling thermo-optical modulation for controlling and directing light in stimuli-responsive devices. 相似文献
999.
In this study, a syringe was filled with silica gel loaded with 3-aminopropyltriethoxysilane, for the separation and preconcentration of copper, cadmium and chromium prior to their determination by graphite furnace atomic absorption spectrometry (GFAAS) in seawater. For this purpose, a syringe was filled with 0.5 g of modified silica gel and the sample solution was drawn into the syringe and ejected back again. The analyte elements were quantitatively retained at pH 5. Then, the elements sorbed by the silica gel were eluted with 2.0 M of HCl and determined by GFAAS. At optimum conditions, the recovery of Cu, Cd and Cr were 96-98%. Detection limits (3delta) were 6.6, 7.5 and 6.0 micro g L(-1) for Cu, Cd and Cr, respectively. The elements could be concentrated by drawing and discharging several portions of sample successively but eluting only once. Cu, Cd and Cr added to a seawater sample were quantitatively recovered (>95%) in the range of the 95% confidence level. The method proposed in this paper was compared with a column technique. Optimum experimental conditions, reproducibility, precision and recoveries of both techniques are the same, but the syringe technique is much faster, easier and more practical than the column technique. It is a portable system and allows one to make the sorption process in the source of sample. In addition, the risk of contamination is less than in the column technique. 相似文献
1000.
The adsorption/desorption process of borate was studied at Pt(111) in acidic solution by cyclic voltammetry. A so-called butterfly
wave in the cyclic voltammogram of Pt(111) in HClO4 shifted to negative direction upon the addition of boric acid with the disappearance of its sharp spikes. The shift in potential
was found to be −57 mV with a tenfold increase of boric acid concentration. This illustrates that this anomalous wave is due
to borate adsorption/desorption by a one-electron transfer process. The borate adsorption/desorption wave was observed to
shift by −63 mV/pH. At pH>3, the anomalous wave splits forming two separate waves, depending on the pH and the scan rate.
The appearance of two waves is assigned to the change in the adsorption mode of borate or the participation of OH in the adsorption
process. 相似文献