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591.
在中国原子能科学研究院重水堆水平孔道旁,建立了高效率的Be过滤探测器中子非弹性散射谱仪,首次研制了具有宽的接受角(~30°)和聚焦安排的新型Be过滤器,使探测效率提高3倍以上,同时也克服了一般Be过滤谱仪在低能段相干散射的影响.本谱仪还通过具有特殊取向的Ge单色器的不同晶面的自动转向,拓宽了测量的能量范围(10—400meV),并有较好的能量分辨率(4%—9%).在此谱仪上对ZrH1.6和PdH0.58的光学振动模以及高Tc超导材料YBa2 Cu3 O6+x的全频谱进行了测试,观察出奇异的结构峰、高频模和反常的散射强度,表明本谱仪不仅效率高而且还具有优良的物理性能,可以在中等通量水平的反应堆上开展广泛的热中子非弹性散射研究. 相似文献
592.
Huang HG Huang JY Zhang YP Ning YS Yong KS Xu GQ 《The journal of physical chemistry. B》2005,109(11):4999-5004
The cumulative double bond (C=C=C), an important intermediate in synthetic organic chemistry, was successfully prepared via the selective attachment of acetylethyne to Si(111)-7 x 7. The experimental observation of the characteristic vibrational modes and electronic structures of the C=C=C group in the surface species demonstrates the [4 + 2]-like cycloaddition occurring between the terminal O and C atoms of acetylethyne and the neighboring Si adatom-rest atom pair, consistent with the prediction of density functional theory calculations. Scanning tunneling microscopy images further reveal that the molecules selectively bind to the adjacent adatom-rest atom pairs on Si(111)-7 x 7. 相似文献
593.
Huang HG Zhang YP Cai YH Huang JY Yong KS Xu GQ 《The Journal of chemical physics》2005,123(10):104702
The interaction of benzaldehyde with the Si(100) surface has been investigated as a model system for understanding the interaction of conjugated pi-electron systems with semiconductor surfaces. Vibrational features of chemisorbed benzaldehyde unambiguously demonstrate that the carbonyl group directly interacts with the Si surface dangling bonds, evidenced in the disappearance of the C=O stretching mode around 1713 cm(-1) coupled with the retention of all vibrational signatures of its phenyl ring. X-ray photoemission spectroscopy shows that both C 1s and O 1s binding energies of the carbonyl group display large downshifts by 1.9 and 1.3 eV, respectively. Vibrational and electronic results show that the covalent attachment of benzaldehyde on Si(100) occurs in a highly selective manner through the direct interaction of both C and O atoms of the carbonyl group with a Si=Si dimer to form a four-membered Si-C-O-Si ring at the interface, leaving a nearly unperturbed phenyl ring protruding into vacuum. This conclusion is further confirmed by the observation of a predominant protrusion for benzaldehyde adsorbed on Si(100)-2 x 1 in scanning tunneling microscopy experiments, consistent with the predication of density-functional theory calculation. 相似文献
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597.
Huang JY Shao YX Huang HG Cai YH Ning YS Tang HH Liu QP Alshahateet SF Sun YM Xu GQ 《The journal of physical chemistry. B》2005,109(42):19831-19838
The interaction of methacrylic acid and methyl methacrylate with Si(111)-7 x 7 has been investigated using high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS). While methacrylic acid chemisorbs dissociatively through O-H bond cleavage, methyl methacrylate is covalently attached to the silicon surface via a [4+2] cycloaddition. The different reaction pathways of these two compounds on Si(111)-7 x 7 demonstrate that the substitution groups play an important role in determining the reaction channels for multifunctional molecules, leading to the desired flexibility in the organic modification of silicon surfaces. 相似文献
598.
Huang JY Huang HG Ning YS Liu QP Alshahateet SF Sun YM Xu GQ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(25):11722-11728
The attachment of methyl methacrylate (MMA) on Si(100)-2x1 was investigated using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) calculations. The HREELS spectra of chemisorbed MMA show the disappearance of characteristic vibrations of C=O (1725 cm(-1)) and C(sp(2))-H (3110, 1400, and 962 cm(-1)) coupled with the blue shift of the C=C stretching mode by 34 cm(-1) compared to those of physisorbed molecules. These results clearly demonstrate that both C=C and C=O in MMA directly participate in the interaction with the surface to form a SiCH(2)C(CH(3))=C(OCH(3))OSi species via a [4+2]-like cycloaddition. This binding configuration was further supported by XPS, UPS, and DFT studies. 相似文献
599.
Araki K Endo H Masuda G Ogawa T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(13):3331-3340
A novel complex containing a 3,8-bis[terthiophenyl-(1,10-phenanthroline)] ligand coordinated to [Ru(bpy)(2)] was synthesized and characterized by electrochemical and spectroscopic techniques. The complex was shown to be a suitable starting material for the electrodeposition of functionalized molecular wires between nanogap electrodes to generate stable molecular nanodevices. Temperature-dependent nonlinear I-V curves were obtained at 80-300 K. The material can also be deposited on indium tin oxide (ITO) to form compact electrochromic films at surface concentrations lower than approximately 1 x 10(-8) mol cm(2); however, a more loosely bond fibrous form is preferentially deposited at higher surface concentrations. 相似文献
600.
Huang HG Xiang CL Ning YS Huang JY Ang SG Xu GQ 《The journal of physical chemistry. B》2005,109(41):19296-19300
The interactions of cyanoacetylene and diacetylene with a Si(111)-7 x 7 surface have been studied as model systems to mechanistically understand the chemical binding of unsaturated organic molecules to diradical-like silicon dangling bonds. Vibrational studies show that cyanoacetylene mainly binds to the surface through a diradical reaction involving both cyano and C[triple bond]C groups with an adjacent adatom-rest atom pair at 110 K, resulting in an intermediate containing triple cumulative double bonds (C=C=C=N). On the other hand, diacetylene was shown to the covalently attached to Si(111)-7 x 7 only through one of its C[triple bond]C groups, forming an enynic-like structure with a C=C-C[triple bond]C skeleton. These chemisorbed species containing triple cumulative double bonds (C=C=C=N) and C=C-C[triple bond]C may be employed as precursors (or templates) for further construction of bilayer organic films on the semiconductor surfaces. 相似文献