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991.
C. Sekar S. PaulrajG. Krabbes M. KanagarajS. Arumugam Ravhi S. Kumar 《Journal of magnetism and magnetic materials》2011,323(23):3033-3037
MCu2O3 (M=Ca and Co) system has two-leg spin ladder structure similar to that of the prototype SrCu2O3 system except that the rungs are buckled with an angle of 123° and 105° for CaCu2O3 and CoCu2O3 compounds, respectively. We have synthesized powder samples of (Ca1−xCox)Cu2O3 (x=0.00-1.00) by the solid state reaction method and their structural and magnetic properties have been investigated. All the synthesized compounds crystallize in orthorhombic structure with space group Pmmn. Lattice parameters of (Ca1−xCox)Cu2O3 decrease with the increase in Co content. DC magnetic susceptibility χ(T) results of the end products CaCu2O3 and CoCu2O3 show antiferromagnetic transition (TN) at 27 and 215 K, respectively. Co doping into (Ca1−xCox)Cu2O3 enhances its TN systematically with increasing Co concentration. The χ(T) of CoCu2O3 shows a broad transition with the peak temperature around 215 K and it was found to be field independent up to 90 kOe. The ambiguity concerning the transition was ruled out by recording the temperature dependent X-ray diffraction pattern on CoCu2O3 system, which indicated that there is no structural transition in the investigated temperature range of 115-300 K. Further, specific heat measurement on CoCu2O3 confirms the magnetic phase transition by the appearance of a sharp peak at 215 K. 相似文献
992.
利用基尔霍夫衍射公式通过数值计算绘制出理想狭缝在不同区域的衍射光强分布,并与菲涅耳衍射公式及夫朗禾费衍射公式的计算的结果比较,对基尔霍夫衍射公式、菲涅尔衍射公式和夫朗禾费衍射公式的适用范围做了详细的讨论. 相似文献
993.
C. Mauder B. Reuters L. Rahimzadeh Khoshroo M.V. Rzheutskii E.V. Lutsenko G.P. Yablonskii J.F. Woitok M. Heuken H. Kalisch R.H. Jansen 《Journal of Crystal Growth》2010,312(11):1823-1827
The anisotropic film properties of m-plane GaN deposited by metal organic vapour phase epitaxy (MOVPE) on LiAlO2 substrates are investigated. To study the development of layer properties during epitaxy, the total film thickness is varied between 0.2 and 1.7 μm. A surface roughening is observed caused by the increased size of hillock-like features. Additionally, small steps which are perfectly aligned in (1 1 −2 0) planes appear for samples with a thickness of ∼0.5 μm and above. Simultaneously, the X-ray rocking curve (XRC) full width at half maximum (FWHM) values become strongly dependent on incident X-ray beam direction beyond this critical thickness. Anisotropic in-plane compressive strain is initially present and gradually relaxes mainly in the [1 1 −2 0] direction when growing thicker films. Low-temperature photoluminescence (PL) spectra are dominated by the GaN near-band-edge peak and show only weak signal related to basal plane stacking faults (BSF). The measured background electron concentration is reduced from ∼1020 to ∼1019 cm−3 for film thicknesses of 0.2 μm and ∼1 μm while the electron mobilities rise from ∼20 to ∼130 cm2/V s. The mobilities are significantly higher in [0 0 0 1] direction which we explain by the presence of extended planar defects in the prismatic plane. Such defects are assumed to be also the cause for the observed surface steps and anisotropic XRC broadening. 相似文献
994.
A new organic compound of bis-glycine maleate was synthesized in the alkaline medium of 10% ammonium hydroxide solution. The bulk single crystals of Bis-Glycine Maleate (BGM) have been grown by slow cooling method. The grown crystals were characterized by employing single crystal and powder X-ray diffraction, Fourier transform infrared, optical absorption spectral studies and thermo gravimetric analysis. The microhardness studies confirmed that the BGM has a fairly high Vicker’s hardness number value (41 kg mm−2) in comparison to other organic NLO crystals. Second harmonic generation efficiency of the crystal measured by Kurtz–Perry powder method using Nd:YAG laser is found to be comparable to that of potassium dihydrogen phosphate (KDP). Frequency dependent dielectric studies were carried out along the major growth axis. 相似文献
995.
C. Martos B. Coto J.L. Peña R. Rodríguez D. Merino-Garcia G. Pastor 《Journal of Crystal Growth》2010,312(19):2756-2763
The deposition of inorganic salts (“scales”) such as calcium carbonate is an important flow assurance problem during crude oil production. The knowledge of the features of the precipitated solids, mainly the particle size and morphology, is crucial to understand the nature of the solids and to avoid or reduce the effect of their deposition. For instance, the use of additives is one of the most usual procedures to mitigate this problem. Additives interact with scale-forming substances either by increasing the induction time, or by inhibiting crystal growth, changing the morphology of solids. 相似文献
996.
Hooyoung Song Jooyoung Suh Eun Kyu Kim Kwang Hyeon Baik Sung-Min Hwang 《Journal of Crystal Growth》2010,312(21):3122-3126
Nonpolar (1 1–2 0) a-plane GaN films have been grown using the multi-buffer layer technique on (1–1 0 2) r-plane sapphire substrates. In order to obtain epitaxial a-plane GaN films, optimized growth condition of the multi-buffer layer was investigated using atomic force microscopy, high resolution X-ray diffraction, and transmission electron microscopy measurements. The experimental results showed that the growth conditions of nucleation layer and three-dimensional growth layer significantly affect the crystal quality of subsequently grown a-plane GaN films. At the optimized growth conditions, omega full-width at half maximum values of (11–20) X-ray rocking curve along c- and m-axes were 430 and 530 arcsec, respectively. From the results of transmission electron microscopy, it was suggested that the high crystal quality of the a-plane GaN film can be obtained from dislocation bending and annihilation by controlling of the island growth mode. 相似文献
997.
B. Díaz A. Malachias P.H.O. Rappl E. Abramof V.A. Chitta A.B. Henriques 《Journal of Crystal Growth》2010,312(19):2828-2833
Semiconductor magnetic quantum dots are very promising structures, with novel properties that find multiple applications in spintronic devices. EuTe is a wide gap semiconductor with NaCl structure, and strong magnetic moments S=7/2 at the half filled 4f7 electronic levels. On the other hand, SnTe is a narrow gap semiconductor with the same crystal structure and 4% lattice mismatch with EuTe. In this work, we investigate the molecular beam epitaxial growth of EuTe on SnTe after the critical thickness for island formation is surpassed, as a previous step to the growth of organized magnetic quantum dots. The topology and strain state of EuTe islands were studied as a function of growth temperature and EuTe nominal layer thickness. Reflection high energy electron diffraction (RHEED) was used in-situ to monitor surface morphology and strain state. RHEED results were complemented and enriched with atomic force microscopy and grazing incidence X-ray diffraction measurements made at the XRD2 beamline of the Brazilian Synchrotron. EuTe islands of increasing height and diameter are obtained when the EuTe nominal thickness increases, with higher aspect ratio for the islands grown at lower temperatures. As the islands grow, a relaxation toward the EuTe bulk lattice parameter was observed. The relaxation process was partially reverted by the growth of the SnTe cap layer, vital to protect the EuTe islands from oxidation. A simple model is outlined to describe the distortions caused by the EuTe islands on the SnTe buffer and cap layers. The SnTe cap layers formed interesting plateau structures with easily controlled wall height, that could find applications as a template for future nanostructures growth. 相似文献
998.
L.M. Chen W. Tao Z.Y. Zhao Q.J. Li W.P. Ke X.M. Wang X.G. Liu C. Fan X.F. Sun 《Journal of Crystal Growth》2010,312(21):3243-3246
The bulk single crystals of low-dimensional magnet (CH3)2NH2CuCl3 (DMACuCl3 or MCCL) are grown by a slow evaporation method with different kinds of solvents, different degrees of super-saturation of solution and different temperatures of solution, respectively. Among three kinds of solvent, methanol, alcohol and water, alcohol is found to be the best one for growing MCCL crystals because of its structural similarity to the raw materials and suitable evaporation rate. The best growth temperature is in the vicinity of 35 °C. The problem of the crystals deliquescing in air has been solved through recrystallization process. The crystals are characterized by means of X-ray diffraction, specific heat and magnetic susceptibility. 相似文献
999.
1000.
Vakhid A. Mamedov Dina F. Saifina Venera R. Ganieva Dimitry V. Rakov Oleg G. Sinyashin 《Tetrahedron letters》2010,51(50):6503-6506
A highly efficient, one-step, versatile method for the synthesis of 2-benzimidazol-2-ylquinolines has been developed on the basis of an acid-catalyzed rearrangement proceeding via a novel ring contraction of 3-(β-2-aminostyryl)quinoxalin-2(1H)ones. 相似文献