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851.
The electronic band structure and stability of extended nanocrystallites (NCs) of titanium monocarbide TiC were investigated by the electron density functional-tight binding (DFTB) technique. The stability of prismatic NCs increases with the number of atomic layers; the electronic spectrum of these compounds changes from semiconductor (for NC of minimal atomic size) to metallike type inherent in crystalline titanium carbide. 相似文献
852.
853.
The growth of ultrathin films of Si3N4 directly on Si surfaces is studied with valence band photoemission. The information from these studies about the growth mechanism and the changes of the electronic structure is enhanced by the use of various photon energies with synchrotron radiation. The silicon nitride films are grown isothermally on the Si(1 0 0) and Si(1 1 1) surfaces by reactions with atomic N. The atomic nitrogen is produced by using a remote, microwave excited nitrogen plasma. The growth under these conditions was earlier shown to be self limiting. The details in the valence band spectra are identified and resolved with numerical methods, and followed systematically during the growth. Thus the identification of Si surface states, Si-nitride interface states and bulk nitride states becomes possible. The previously obtained separation between amorphous and crystalline growth occurring around 500 °C is further supported in the present studies. 相似文献
854.
本文考虑非可微凸规划的一个对偶问题,它使用目标函数的扰动函数的次微分及外法向量锥,它不同于已知结果.我们给出相应的对偶性质. 相似文献
855.
Haijun Tao Jun Zhang Xiaolin Wang Jiali Gao 《Journal of Polymer Science.Polymer Physics》2007,45(2):153-161
The effects of the polymer concentration and quenching temperature on the phase separation, the membrane morphology and polymer crystallization behavior in a poly(4‐methyl‐1‐pentene) (TPX)‐dioctylsebacate (DOS)‐dimethylphthalate (DMP) system via thermally induced phase separation were studied with a pseudobinary phase diagram, with the weight ratio of DOS:DMP = 1:1. SEM was used to observe the membrane morphology and structure, whereas the TPX crystallization behavior was studied with DSC and WAXD. Liquid‐liquid phase separation occurred, although quenching under the crystallization temperature. As the quenching temperature decreased, the pore size decreased, with better connected pore structure formed. The membranes quenched at 333 and 363 K showed good cellular structures, with an average pore size of about 2.3μm, whereas the pores of the membranes quenched at 393 and 423 K were not well formed, with some lamellar crystals on the inner side. The diluent assisted the mobility of the polymer chain, which improved the polymer crystallization. Dual‐melting‐peak behavior occurred for all the samples studied here. As the quenching temperature increased, the first peak of the melting trace moved to a higher temperature, whereas the second one stayed almost the same. The flexibility of the TPX main chain was restricted by the side groups, which allowed liquid‐liquid phase separation to occur first when quenched below the equilibrium crystallization temperature. This allowed primary and secondary crystallization, which was responsible for the dual‐melting‐peak behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 153–161, 2007 相似文献
856.
857.
We have used IR spectroscopy to study the structure of tellurium germanate glasses synthesized in the system TeO2-GeO2-B2O3-PbO. The structure of the glasses consists of [BO3], [BO4], [GeO4], [GeO6], [TeO3], and [PbO6] groups. Changes in the coordination of boron and germanium ions occur when the PbO and GeO2 contents in the glasses increase. The glasses are attractive for designing optical and laser devices.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 78–81, January–February, 2007. 相似文献
858.
通过将箭图的每个顶点放置一个k-余代数,首先引进了广义路余代数的概念,其次给出了广义路余代数的一些基本性质,还讨论了同构问题.证明了两个正规广义路余代数是同构的当且仅当他们的箭图及对应顶点上的单余代数是同构的.对于满足Codim C_0■1余代数C,证明了对偶Wedderburn-Malcev定理成立.作为广义路余代数的一个应用,推广了点余代数的对偶Gabriel定理. 相似文献
859.
E. M. Woo Kai Cheng Yen Ming Chien Wu 《Journal of Polymer Science.Polymer Physics》2008,46(9):892-899
In‐depth interpretation of ring‐banded spherulitic morphology, crystals, polymorphism, and complex melting behavior in poly(1,4‐butylene adipate) (PBA) were analyzed via a procedure of designing composite core‐shell spherulites, in which two lamellar patterns (ring‐band vs. ringless) were packed by subjecting to crystallization at two‐step temperature schemes with specific temperatures and times. By heating to 52 °C and holding at that temperature for 30 min annealing, the core can be stripped off by melting, and analysis specifically on the ring‐shell portion (with the ringless core stripped by controlled melting) proves that the highest melting peak (P4 at 55–57 °C) is likely associated with melting of the ring‐band lamellae. Furthermore, the unusually complex multiple melting in PBA can be attributed to all three widely proposed mechanisms: (1) multiple types of lamellae preexisting in crystallized PBA, (2) scan/heating induced remelting/reorganization, and (3) polymorphism of dual crystal cells. In addition, this study evidently shows that the extinction rings within the ring‐banded shell, regardless of alternate edge‐on and flat‐on mechanism or alternative origins, can be of all singly α‐crystal form, either initially or upon postheating temperature‐induced transformation. Thus, the type of crystal forms (α or β) in polymorphic PBA is mainly associated with temperature of crystallization (Tc = 28 or 35 °C), and not likely with lamellar orientation (flat‐on or edge‐on). © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 892–899, 2008 相似文献
860.
Xiaohua Yang Jingwen Ben Ling Li Yangqin Chen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(3):468-475
Six hundred and sixty-one spectral lines of the (3, 1) band in the d3Δ-a3Π system of CO in the range of 13,410-13,920 cm−1 were observed employing optical heterodyne magnetic rotation enhanced concentration modulation spectroscopy. Improved molecular constants of the upper vibrational level involved were obtained by a non-linear least-squares weighted fitting procedure using effective Hamiltonians with those of the lower levels fixed at the values obtained in the sub-millimeter region, and the improvements are around one order of magnitude. 相似文献