全文获取类型
收费全文 | 2521篇 |
免费 | 53篇 |
国内免费 | 10篇 |
专业分类
化学 | 1350篇 |
晶体学 | 47篇 |
力学 | 53篇 |
数学 | 328篇 |
物理学 | 806篇 |
出版年
2022年 | 37篇 |
2021年 | 36篇 |
2020年 | 38篇 |
2019年 | 48篇 |
2018年 | 55篇 |
2017年 | 55篇 |
2016年 | 70篇 |
2015年 | 47篇 |
2014年 | 92篇 |
2013年 | 186篇 |
2012年 | 121篇 |
2011年 | 137篇 |
2010年 | 97篇 |
2009年 | 88篇 |
2008年 | 111篇 |
2007年 | 89篇 |
2006年 | 68篇 |
2005年 | 71篇 |
2004年 | 61篇 |
2003年 | 49篇 |
2002年 | 44篇 |
2001年 | 23篇 |
2000年 | 29篇 |
1999年 | 21篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 22篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 34篇 |
1992年 | 31篇 |
1990年 | 19篇 |
1989年 | 28篇 |
1988年 | 30篇 |
1987年 | 25篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 29篇 |
1983年 | 26篇 |
1982年 | 28篇 |
1981年 | 42篇 |
1980年 | 43篇 |
1979年 | 32篇 |
1978年 | 41篇 |
1977年 | 43篇 |
1976年 | 27篇 |
1975年 | 26篇 |
1974年 | 26篇 |
1973年 | 38篇 |
1972年 | 24篇 |
排序方式: 共有2584条查询结果,搜索用时 15 毫秒
71.
72.
We have theoretically investigated the effect of pressure on the structural stability of GaP?:?InP mixed system. The three-body-potential (TBP) model has been used. The TBP model consists of long-range as well as short-range interactions; the long-range part includes the modified Coulomb force as well as a three-body term; the short-range part in TBP defines the van der Waals and overlap repulsive interactions. We observe a pressure-induced structural phase transformation from ZnS (B3) to NaCl (B1) type phase in Ga 1?x In x P. Our calculated transition pressures for the initial GaP and final InP compound semiconductors are in good agreement with other reported data. 相似文献
73.
74.
Induced twisted-grain-boundary phases in the binary mixtures of a cholesteric and a nematic compound
Thermodynamical, optical-texture and dielectric studies have been performed to study the phase diagram of the binary system of 5-cholesten-3β-ol-octanoate and 4-n-nonyloxybenzoic acid. It is observed that low concentrations of 5-cholesten-3β-ol-octanoate (2–30?mol?%) in 4-n-nonyloxybenzoic acid induce a mean-field phase diagram derived by Renn within the framework of the chiral Chen–Lubenski model. Various optical textures of the twisted-grain-boundary (TGB) phases under different conditions of molecular anchoring have been observed. Weak transitions related to the TGB phases have been detected by temperature dependent dielectric spectroscopy. 相似文献
75.
Malik Abdul Waseem ShireenAnjali Srivastava Arjita SrivastavaRahila I.R. Siddiqui 《Tetrahedron letters》2014
Reusable [bmIm]OH was found to be a highly efficient renewable homogenous catalyst for the rapid and convenient synthesis of benzoxazine-4-one derivatives from o-iodobenzoic-acid and benzonitrile at 75 °C in moderate to good yields. This methodology provides a facile and straightforward path to construct other related heterocycles in an eco-compatible fashion. 相似文献
76.
Xiao-Jun Yang H.M. Srivastava Ji-Huan He Dumitru Baleanu 《Physics letters. A》2013,377(28-30):1696-1700
In this Letter, we propose to use the Cantor-type cylindrical-coordinate method in order to investigate a family of local fractional differential operators on Cantor sets. Some testing examples are given to illustrate the capability of the proposed method for the heat-conduction equation on a Cantor set and the damped wave equation in fractal strings. It is seen to be a powerful tool to convert differential equations on Cantor sets from Cantorian-coordinate systems to Cantor-type cylindrical-coordinate systems. 相似文献
77.
H. M. Srivastava Shy-Der Lin Shuoh-Jung Liu Han-Chun Lu 《Russian Journal of Mathematical Physics》2012,19(1):121-130
Motivated essentially by their potential for applications in the mathematical, physical, and statistical sciences, the object
of this paper is to investigate several general families of hypergeometric polynomials and their associated multiple integral
representations. By suitably specializing the main results presented here, the corresponding integral representations are
derived for familiar simpler classes of hypergeometric polynomials such as (for example) the Lagrange polynomials, Shively’s
pseudo-Laguerre polynomials, and generalized Bessel polynomials. Each of the integral representations derived in this paper
may be also viewed as a linearization relationship for the product of two different members of the associated family of hypergeometric
polynomials. 相似文献
78.
Hiroya Takada Yoshiaki Nishibayashi Sanjay Kumar Srivastava Kouichi Ohe Sakae Uemura 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):629-632
Asymmetric intramolecular selenocyclisation of alkenoic acids, alkenols and alkenyl urethanes using chiral ferrocenylselenenyl cations proceeds smoothly to give the corresponding lactones, cyclic ethers and N-heterocyclic compounds, respectively, in moderate yields with very high diastereoselectivities. 相似文献
79.
R. K. Gupta A. K. Sinha B. N. Raja Sekhar A. K. Srivastava G. Singh S. K. Deb 《Applied Physics A: Materials Science & Processing》2011,103(1):13-19
Controllable and uniform doping of nanowires (NWs) is the ultimate challenge prior to their effective application. Si NWs
amorphize and bend toward the impinging ions under ion irradiation as a result of viscous flow. We demonstrate that thermal
annealing induces a full recovery of the crystalline phase corresponding to the unbending of the NWs. The competition between
Solid Phase Epitaxy and Random Nucleation and Growth at the nanoscale is the key parameter controlling the recovery. 相似文献
80.
S. K. Srivastava Shailja Tomar Rupali Rastogi Richa Saxena 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):634-640
Six new substituted diphenyltin(IV) O,O′-alkylene dithiophosphates, (C6H5)2Sn(X)S(S) POGO [G = —CH2C(CH3)2CH2—, X = Cl (1), SCN (3), ClO4 (5); G = —CH2C (C4H9)(C2H5)CH2—, X = Cl (2), SCN (4), ClO4 (6)], were synthesized by the reaction of the corresponding ammonium salts of the O,O’-alkylene dithiophosphates with an appropriate organotin(IV) chloride. The compounds were characterized on the basis of elemental and spectral analyses (ESI mass spectrometry, IR, 1H, 13C, 31P, and 119Sn NMR). The presence of a four-coordinated Sn atom and monodentate O,O’-alkylene dithiophosphate moiety in compounds 1–4 as well as bidentate O,O’-alkylene dithiophosphate unit in compounds 5,6 is established. 相似文献