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41.
An attempt is made to synthesize Nd2Co14C compound by mechanical alloying Nd16Co76B8−xCx (0x8) alloys and subsequent annealing. Phase formation and magnetic properties of Nd2Fe14B-type Nd16Co76B8−xCx alloys and their hydrides are investigated. The Nd2Co14(B,C) phase with Nd2Fe14B-type structure is formed for Nd16Co76B8−xCx (0x7) alloys, while NdCo7Cδ phase with TbCu7-type structure is observed in Nd16Co76C8 alloy. The lattice parameter c of the Nd2Co14(B,C) phase decreases with increasing the carbon content. A limit volume of the unit cell to form the Nd2Fe14B-type structure is estimated to be 0.870 nm3. The spin-reorientation temperature TSR increases with increasing the carbon content, due to an enhancement of magnetocrystalline anisotropy caused by carbon substitution for boron. After hydrogenation, the lattice expansion is observed for Nd16Co76B8−xCx (0x7) alloys. The spin-reorientation temperature of Nd16Co76B8−xCxHy (0x7) is much lower than that of the host alloys. Some structural and magnetic properties of hypothetic Nd2Co14C and Nd2Co14CHy compounds are estimated by extrapolation. 相似文献
42.
Izabela Bobowska Aleksandra Wypych-Puszkarz Agnieszka Opasinska Waldemar Maniukiewicz Piotr Wojciechowski 《Phase Transitions》2017,90(1):44-53
ABSTRACTEffects of the elevated temperature on the structure evolution of the ZnO nanorod array (ZNA) and their hybrid nanocomposite with layered (tetramethyl)ammonium titanate (LTMAT) prepared by the liquid phase deposition were investigated. The vertically oriented ZnO nanorods were deposited on a quartz plate by a chemical bath deposition method and then they were penetrated by the LTMAT using the dip-coating method from the water solution. As a result of such an experimental procedure, an assembly composed of the ZNA with LTMAT was obtained and called hybrid nanocomposite. Since the LTMAT converts to TiO2 upon subsequent sintering at 350 °C, it can be regarded as TiO2 precursor for the thermal treatment experiments. The experiments with ZNA and their hybrid nanocomposite at the elevated temperature revealed coalescence of the deposited ZnO nanorods and crystallization of zinc titanate with Zn2TiO4 stoichiometry. 相似文献
43.
The structure, growth and stoichiometry of heteroepitaxial Pr2O3 films on Si(1 1 1) were characterized by a combined RHEED, XRD, XPS and UPS study in view of future applications as a surface science model catalyst system. RHEED and XRD confirm the growth of a (0 0 0 1) oriented hexagonal Pr2O3 phase on Si(1 1 1), matching the surface symmetry by aligning the oxide in-plane direction along the Si azimuth. After an initial nucleation stage RHEED growth oscillation studies point to a Frank-van der Merwe growth mode up to a thickness of approximately 12 nm. XPS and UPS prove that the initial growth of the Pr2O3 layer on Si up to ∼1 nm thickness is characterized by an interface reaction with Si. Nevertheless stoichiometric Pr2O3 films of high crystalline quality form on top of these Pr-silicate containing interlayers. 相似文献
44.
We present further analysis of the structure functions at low-x using the approximate solutions of Altarelli-Parisi equations recently reported by us. We also compare our results with non-perturbative
and non-linear evolutions. 相似文献
45.
L. Szybisz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):733-746
Density functionals proposed in the literature for describing the behaviour of liquid helium at T
=0 K are examined. In so doing, several properties of the ground states of free films of superfluid
4
He are calculated by using zero- and finite-range density functional theories and these results are compared to that computed
with Monte Carlo simulations. We mainly focus the attention on the energy per particle of the slabs, the surface tension and
the width of the liquid-vacuum interfaces, all as a function of the inverse of coverage. The largest differences are found
in the case of the surface widths.
Received 26 July 1999 相似文献
46.
为了获得分束角对称的偏光分束棱镜,在双Wollaston棱镜结构的基础上,通过合理设计棱镜左右两端晶体光轴的取向,使棱镜整体呈中心切面对称;在保证对正向入射的光对称分束的同时,对反向入射光同样可以对称分束,达到了双向对称分束的目的;在此基础上给出了晶体光轴的旋转角δ与棱镜结构角S以及与波长的关系;并分析了对633 nm设计的棱镜用于其他波长时分束角的对称性.结果表明:在±300 nm的光谱范围内,分束角的不对称度均小于0.24°. 相似文献
47.
利用量子化学密度泛函理论B3LYP方法及 6 31G(d ,p)、6 311G(d ,p)、6 31+G(d ,p)和 6 311+G(d ,p)基组对五氟代吡啶、2 ,6 二氟代吡啶和 2 氟代吡啶分子的阳离子进行了计算研究 .B3LYP构型优化和频率分析计算结果表明这三种氟代吡啶阳离子的结构分别具有C2v、C2v和Cs 对称性 ,电子基态分别为2 A2 、2 A2 和2 A″ .对离子和分子的计算构型做了比较 .利用B3LYP方法和不同的基组对这三种阳离子及其分子进行了自然布居分析计算 .用B3LYP方法对这三种阳离子 (自由基 )中的超精细结构进行了计算 ,对五氟代吡啶、2 ,6 二氟代吡啶和2 氟代吡啶分子的垂直电离势和绝热电离势进行了计算 ,与实验值符合得很好 相似文献
48.
The present paper concentrates on structure and micro-mechanical properties of the helium-implanted layer on titanium treated by plasma-based ion implantation with a pulsed voltage of −30 kV and doses of 3, 6, 9 and 12 × 1017 ions/cm2, respectively. X-ray photoelectron spectroscopy and transmission electron microscopy are employed to characterize the structure of the implanted layer. The hardnesses at different depths of the layer were measured by nano-indentation. We found that helium ion implantation into titanium leads to the formation of bubbles with a diameter from a few to more than 10 nm and the bubble size increases with the increase of dose. The primary existing form of Ti is amorphous in the implanted layer. Helium implantation also enhances the ingress of O, C and N and stimulates the formations of TiO2, Ti2O3, TiO, TiC and TiN in the near surface layer. And the amount of the ingressed oxygen is obviously higher than those of nitrogen and carbon due to its higher activity. At the near surface layer, the hardnesses of all implanted samples increases remarkably comparing with untreated one and the maximum hardness has an increase by a factor of up to 3.7. For the samples implanted with higher doses of 6, 9 and 12 × 1017 He/cm2, the local displacement bursts are clearly found in the load-displacement curves. For the samples implanted with a lower dose of 3 × 1017 He/cm2, there is no obvious displacement burst found. Furthermore, the burst width increases with the increase of the dose. 相似文献
49.
Omp33-36 in A. baumannii, a bacterium causing serious nosocomial infections, is a virulence factor associated with the pathogen metabolic fitness as well as its adherence and invasion to human epithelial cells. This protein is also involved in interaction of the bacteria with host cells by binding to fibronectin. Moreover, Omp33-36 renders cytotoxicity to A. baumannii in addition to inducing apoptosis and modulation of autophagy. In the present study, an integrated strategy is launched to pierce into the 3D structure of Omp33-36 protein. The signal peptide within the sequence was determined, then, topology as well as secondary and tertiary structures of the protein were predicted. The mature protein assigned as a 14-stranded barrel in which residues 1–19 is removed as signal peptide. The obtained 3D models were evaluated in terms of quality; and then, served as queries to find similar protein structures. The hits were analyzed regarding topology among which 14-stranded were considered. The most qualified model was refined and then its sequence aligned to its counterpart similar structure protein (CymA from Klebsiella oxytoca). The determined structure of Omp33-36 could justify its porin function and carbapenem-resistance associated with the loss of this protein. 相似文献
50.
Etienne V. Brouillet Alan R. Kennedy Tobias Krämer Robert E. Mulvey Stuart D. Robertson Alexander Stewart Stephen Towie 《无机化学与普通化学杂志》2020,646(13):726-733
Previous studies of different solvates of 2-methylpyridyllithium (2-picolyllithium) have uncovered electronic structures corresponding to aza-allyl and enamido resonance forms of the metallated pyridine-based compounds. Here, we report the synthesis and characterization of [2-CH2Li(THF)2C5H4N], a new THF solvate. X-ray crystallographic studies reveal a dimeric arrangement featuring a non-planar eight-membered [NCCLi]2 ring, in which the primary cation-anion interaction is between the central Li atom and the C atom of the deprotonated methyl group [length, 2.285(2) Å], suggesting a new carbanionic resonance structure for this 2-picolyllithium series. The significant carbanionic character of [2-CH2Li(THF)2C5H4N] was confirmed by gas-phase DFT calculations [B3LYP/6-311+G(d)] with the calculated electron density interrogated by means of quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. For comparison these computational analyses were also performed on the literature structures of [2-CH2Li(2-Picoline)C5H4N] and [2-CH2Li(PMDETA)C5H4N]. In a reactivity study, [2-CH2Li(THF)2C5H4N] was found to undergo nucleophilic addition to pyridine to generate dipyridylmethane in a good yield. 相似文献