全文获取类型
收费全文 | 28362篇 |
免费 | 4619篇 |
国内免费 | 2924篇 |
专业分类
化学 | 18727篇 |
晶体学 | 274篇 |
力学 | 1955篇 |
综合类 | 233篇 |
数学 | 3566篇 |
物理学 | 11150篇 |
出版年
2024年 | 108篇 |
2023年 | 597篇 |
2022年 | 1087篇 |
2021年 | 1096篇 |
2020年 | 1125篇 |
2019年 | 1054篇 |
2018年 | 982篇 |
2017年 | 940篇 |
2016年 | 1378篇 |
2015年 | 1322篇 |
2014年 | 1561篇 |
2013年 | 2097篇 |
2012年 | 2473篇 |
2011年 | 2509篇 |
2010年 | 1681篇 |
2009年 | 1638篇 |
2008年 | 1780篇 |
2007年 | 1544篇 |
2006年 | 1417篇 |
2005年 | 1189篇 |
2004年 | 884篇 |
2003年 | 706篇 |
2002年 | 629篇 |
2001年 | 520篇 |
2000年 | 522篇 |
1999年 | 640篇 |
1998年 | 541篇 |
1997年 | 530篇 |
1996年 | 498篇 |
1995年 | 472篇 |
1994年 | 395篇 |
1993年 | 348篇 |
1992年 | 290篇 |
1991年 | 254篇 |
1990年 | 238篇 |
1989年 | 188篇 |
1988年 | 145篇 |
1987年 | 124篇 |
1986年 | 95篇 |
1985年 | 94篇 |
1984年 | 63篇 |
1983年 | 51篇 |
1982年 | 52篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1957年 | 7篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
Casey Chun Zhou Eric J. Stoner Kent D. Stewart L. Steven Hollis Edmund D. Matayoshi Gregory M. Brill 《Tetrahedron》2004,60(47):10611-10618
Oritavancin is a semi-synthetic glycopeptide antibiotic which is structurally related to vancomycin. When oritavancin bisphosphate is dried in vacuo with heat, a new compound forms. This new compound is stable only in the solid state and reverts to oritavancin in solution. Highly enriched samples of this compound were obtained by preparative HPLC and the structure of this compound was elucidated by using one and two-dimensional (1H and 13C) NMR spectroscopy in conjunction with computer-assisted molecular modeling. It has been determined that oritavancin adopts a conformation similar to that of vancomycin in solution, while the new compound is the unnatural R-AB-biaryl atropisomer of oritavancin. This is the first observation and isolation of an AB-biaryl atropisomer in an intact member of the vancomycin family of glycopeptide antibiotics. 相似文献
83.
GFFs with less than 0.4 dB peak-to-peak error functions are routinely fabricated using commercially available coating machines by utilizing the natural error compensation mechanism of wavelength variable turning point optical monitoring method. 相似文献
84.
Yanqing Tian Xiaohe Xu Yingying Zhao Xinyi Tang Fengyu Su Xiaoguang Zhao Enle Zhou 《Liquid crystals》1995,19(3):295-300
The synthesis of three new series of chiral Schiff's bases containing benzilideneaniline and 2-hydroxybenzilideneaniline moieties as mesogenic cores is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements were used to study the phase transition temperatures and behaviour. The results reveal that most of these materials show chiral smectic mesomorphism. 相似文献
85.
X. S. Wu Xuehai Wu Yunping Li Zhangde Lu Liangen Gong Ping Zhou Qing Zhang 《Fiber and Integrated Optics》1993,12(1):97-103
Miniature, etching ridge InGaAsP/InP Phase Modulator with highly efficient phase shifting efficiency of 60°/V.mm and 43°/V.mm for TE and TM modes, respectively, and 3 dB bandwidth of 650 MHz at 1.52 μm are reported. It is well suited for integrated opto-electronics. Some functions depending on bandwidth of the devices are discussed. 相似文献
86.
对任一函数f∈Lp[0,1],n阶Bernstein—Durrnieyer算子为 相似文献
87.
The line search method incorporating the Wolfe conditions is modified to ensure that a descent algorithm terminates in a finite number of steps at an approximate stationary point where the second-order conditions of optimality are satisfied. A simple procedure based on conjugate directions is proposed to determine directions of negative curvature. 相似文献
88.
89.
This paper studies the pullback asymptotic behavior of solutions for a non-autonomous incompressible non-Newtonian fluid in two-dimensional (2D) bounded domains. We first prove the existence of pullback attractors AV in space V (has H2-regularity, see notation in Section 2) and AH in space H (has L2-regularity) for the cocycle corresponding to the solutions of the fluid. Then we verify the regularity of the pullback attractors by showing AV=AH, which implies the pullback asymptotic smoothing effect of the fluid in the sense that the solutions become eventually more regular than the initial data. 相似文献
90.
A molecular dynamics method has been used to simulate the argon ion-assisted deposition of Cu/Co/Cu multilayers and to explore ion beam assistance strategies that can be used during or after the growth of each layer to control interfacial structures. A low-argon ion energy of 5–10 eV was found to minimize a combination of interfacial roughness and interlayer mixing (alloying) during the ion-assisted deposition of multilayers. However, complete flattening with simultaneous ion assistance could not be achieved without some mixing between the layers when a constant ion energy approach was used. It was found that multilayers with lower interfacial roughness and intermixing could be grown either by modulating the ion energy during the growth of each metal layer or by utilizing ion assistance only after the completion of each layers deposition. In these latter approaches, relatively high-energy ions could be used since the interface is buried and less susceptible to intermixing. The interlayer mixing dependence upon the thickness of the over layer has been determined as a function of ion energy. 相似文献