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961.
Extremely localized molecular orbitals are rigorously localized on only a preselected set of atoms and do not have any tails outside the localization region. The importance of these orbitals lies in their ability to be transferred from one molecule to another one. A new algorithm to determine extremely localized molecular orbitals in the framework of the density functional theory method is presented. This could also be a valuable tool in the quantum mechanics/molecular mechanics methodology where localized molecular orbitals are used to describe covalent bonds across the frontier region. The present approach is used to build up the electron density of thymopentin, a polypeptide constituted by five residues, starting from extremely localized molecular orbitals determined on a set of model molecules. The results obtained confirm good transferability properties for these orbitals.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail 相似文献
962.
EDTA—Cu配合物用于还原糖的测定 总被引:2,自引:0,他引:2
首次报道了应用EDTA(乙二胺四乙酸二钠盐)-铜配合物(EC)测定还原糖的分光光度法,结果表明,pH4~11时EC的最大吸收波长为732nm,在HCO-3CO2-3缓冲介质中,配合物EC的吸光度与还原糖在077~161mg(六碳糖)范围内有很好的线性关系,相关系数大于0998,样品测定回收率在95%~105%之间。该法试剂易得、性质稳定,操作方便,灵敏度较高,取样量少于5mL。 相似文献
963.
An additive procedure (SIBFA) is developed for the rapid computation of conformational energy variations in very large molecules. The macromolecule is built out of constitutive molecular fragments and the intramolecular energy is computed as a sum of interaction energies between the fragments. The electrostatic and the polarization components are calculated using multicenter multipole expansions of theab initio SCF electron density of the fragments. The repulsion component is obtained as a sum of bond and lone pair interactions.Tests of the procedure on a series of model compounds containing ether oxygens and pyridine-like nitrogens are reported and compared with the results of correspondingab initio SCF calculations. The resulting methodology is compatible with the simultaneous computation of intermolecular interactions. 相似文献
964.
叠加法是由内标法衍生而来的一种气相色谱定量方法。对于较复杂混合物的分析,当选择内标物困难时,用叠加法定量更为方便。本文在大量实验的基础上,提出了叠加法定量过程中应注意的一些问题。 相似文献
965.
The geometries of the most stable isomers of gold telluride systems AuTe, Au2Te, and AuTe2 are determined using the MP2 method. The aspect of gold—telluride interaction, the electron correlation, and relativistic
effects on geometry and stability are investigated at the MP2 and CCSD(T) theoretical levels. The results show that the electron
correlation and relativistic effects are responsible not only for gold—gold attraction but also for additional gold—telluride
interaction. The gold—telluride interaction is strong enough to modify the known pattern of bare gold clusters. Both effects
are essential for determining the geometry and relative stability of this type of systems. 相似文献
966.
967.
968.
The dependence of the frequency factor on the temperature (A=A
0
T
m) has been examined and the errors involved in the activation energy calculated from some integral methods without considering
such dependence have been estimated. Investigated integral methods are the Coats-Redfern method, the Gorbachev-Lee-Beck method,
the Wanjun-Yuwen method and the Junmeng-Fusheng method. The results have shown that the error in the determination of the
activation energy calculated ignoring the dependence of the frequency factor on the temperature can be rather large and it
is dependent on x=E/RT and the exponent m. 相似文献
969.
Zhengbin Zhang Liansheng Liu Hongbin Zhao Youjun Fu Fengyun Cheng Weihong Zhao 《中国科学B辑(英文版)》1997,40(4):353-364
A new method for the study of ternary surface complexes at liquid-solid interface, theE(%) -pH curve method, was proposed. Four types ofE(%)-pH curves, namely, phenomenon of left-right shifts of S-shaped curve, V-shaped curve, monodirection shift curve and X-shaped
curve, were discovered. Correspondingly, apart from type (I) ternary surface complex
and type (II) ternary surface complex
, a new type of ternary surface complex
was discovered.
Project supported by the National Natural Science Foundation of China and the Fund of Doctoral Degree’s Spot. 相似文献
970.
Akihiko Kanazawa Tomiki Ikeda Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):335-343
Various polymeric phosphonium salts and the corresponding low-molecular-weight model compounds were prepared and their antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell counting method in sterile distilled water. Antibacterial activity of the polymers was found to be higher than that of the corresponding model compounds, particularly against S. aureus. Furthermore, the polymeric phosphonium salt exhibited a higher activity by 2 orders of magnitude than the polymeric quaternary ammonium salt with the same structure except the cationic part. Compounds with the longest alkyl chain (octyl) studied were found to exhibit particularly high activity, and this finding may be ascribed to the contribution of the increased hydrophobicity of the compounds to the cidal activity. © 1993 John Wiley & Sons, Inc. 相似文献