全文获取类型
收费全文 | 22946篇 |
免费 | 4147篇 |
国内免费 | 2853篇 |
专业分类
化学 | 16700篇 |
晶体学 | 281篇 |
力学 | 1377篇 |
综合类 | 146篇 |
数学 | 2486篇 |
物理学 | 8956篇 |
出版年
2024年 | 58篇 |
2023年 | 525篇 |
2022年 | 575篇 |
2021年 | 851篇 |
2020年 | 1046篇 |
2019年 | 999篇 |
2018年 | 883篇 |
2017年 | 835篇 |
2016年 | 1183篇 |
2015年 | 1178篇 |
2014年 | 1322篇 |
2013年 | 1730篇 |
2012年 | 2110篇 |
2011年 | 2044篇 |
2010年 | 1439篇 |
2009年 | 1347篇 |
2008年 | 1465篇 |
2007年 | 1329篇 |
2006年 | 1239篇 |
2005年 | 1103篇 |
2004年 | 816篇 |
2003年 | 662篇 |
2002年 | 663篇 |
2001年 | 506篇 |
2000年 | 460篇 |
1999年 | 518篇 |
1998年 | 382篇 |
1997年 | 380篇 |
1996年 | 357篇 |
1995年 | 309篇 |
1994年 | 237篇 |
1993年 | 227篇 |
1992年 | 179篇 |
1991年 | 151篇 |
1990年 | 166篇 |
1989年 | 121篇 |
1988年 | 94篇 |
1987年 | 57篇 |
1986年 | 73篇 |
1985年 | 75篇 |
1984年 | 40篇 |
1983年 | 36篇 |
1982年 | 43篇 |
1981年 | 24篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Acta Mathematicae Applicatae Sinica, English Series - In this paper, we investigate standing waves in discrete nonlinear Schrödinger equations with nonperiodic bounded potentials. By using the... 相似文献
992.
A variety of heterobiaryl compounds have been synthesized by the Suzuki‐Miyaura coupling reactions of heteroaryl halides with potassium aryltrifluoroborates. Pd (OAc)2 was found to be highly efficient for the Suzuki‐Miyaura coupling reactions of various heteroaryl halides with potassium aryltrifluoroborates in aqueous systems, delivering the corresponding heterobiaryl compounds in good to excellent yields. 相似文献
993.
Li Song Jiaxiang Lin Yang He Jingqing Li Jing Sheng Shichun Jiang Dinghai Huang 《Journal of Polymer Science.Polymer Physics》2019,57(3):142-151
Time‐dependent demixing enthalpy recovery behavior of aqueous poly(vinyl methyl ether) (PVME) solutions exhibits distinct recovery characteristics in three concentration regions. The absence of recovery behavior below a water concentration of 38.3 wt % indicates that the PVME coil is in a globular state. The typically sigmoidal recovery behavior of demixing enthalpy above 38.3 wt % is ascribed to the reswelling of the collapsed polymer coils induced by the entropic effect. The increase in difference between the upper and lower limits indicates the continued swelling of the PVME coils. Above 65 wt %, a dominant diluting effect can be observed, and a much longer phase separation time is needed to reach the expected lower limit. In contrast, the recovery of demixing enthalpy in a wide range of water concentration (from 38.3 to 90 wt %) exhibits the same feature. The infrared spectroscopy results are in agreement with the above macroscopic differential scanning calorimetry results. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 142–151 相似文献
994.
Wen‐ming He 《Numerical Methods for Partial Differential Equations》2019,35(6):2044-2055
In this article, we will discuss the local ultraconvergence of high‐degree finite element method based on a rectangular partition for the second‐degree elliptic problem with constant coefficients in Ω ? ?2 , u( y ) = 0 on ?Ω . Based on suitable regularity, ultraconvergence of the displacement of the extrapolated kth (k ≥ 3) degree finite element solution has been obtained by an extrapolation technique. Finally, numerical experiments are applied to demonstrate our theoretical findings. 相似文献
995.
Yongshuai Zhang Xiangxing Tao Tengteng Yao Jingsong He 《Studies in Applied Mathematics》2020,145(4):812-827
Based on the inverse scattering method, the formulae of one higher-order pole solitons and multiple higher-order poles solitons of the nonlinear Schrödinger equation (NLS) equation are obtained. Their denominators are expressed as , where is a matrix frequently constructed for solving the Riemann-Hilbert problem, and the asterisk denotes complex conjugate. We take two methods for proving is invertible. The first one shows matrix is equivalent to a self-adjoint Hankel matrix , proving . The second one considers the block-matrix form of , proving . In addition, we prove that the dimension of is equivalent to the sum of the orders of pole points of the transmission coefficient and its diagonal entries compose a set of basis. 相似文献
996.
Dr. Saud Asif Ahmed Qiao-Bo Liao Qi Shen Dr. Mirza Muhammad Faran Ashraf Baig Juan Zhou Cai-Feng Shi Dr. Pir Muhammad Dr. Sumaira Hanif Prof. Kai Xi Prof. Xing-Hua Xia Prof. Kang Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(57):12996-13001
Layered/two-dimensional covalent organic frameworks (2D COF) are crystalline porous materials composed of light elements linked by strong covalent bonds. Interlayer force is one of the main factors directing the formation of a stacked layer structure, which plays a vital role in the stability, crystallinity, and porosity of layered COFs. The as-developed new way to modulate the interlayer force of imine-linked 2D TAPB-PDA-COF (TAPB = 1,3,5-tris(4-aminophenyl)benzene, PDA = terephthaldehyde) by only adjusting the pH of the solution. At alkaline and neutral pH, the pore size of the COF decreases from 34 Å due to the turbostratic effect. Under highly acidic conditions (pH 1), TAPB-PDA-COF shows a faster and stronger turbostratic effect, thus causing the 2D structure to exfoliate. This yields bulk quantities of an exfoliated few/single-layer 2D COF, which was well dispersed and displayed a clear Tyndall effect (TE). Furthermore, nanopipette-based electrochemical testing also confirms the slipping of layers with increase towards acidic pH. A model of pH-dependent layer slipping of TAPB-PDA-COF was proposed. This controllable pH-dependent change in the layer structure may open a new door for potential applications in controlled gas adsorption/desorption and drug loading/releasing. 相似文献
997.
998.
Zhu Kai Li Cui Wu Kingsley Y. Mohr Christopher Li Xun Lanman Brian 《Journal of computer-aided molecular design》2022,36(8):591-604
Journal of Computer-Aided Molecular Design - KRAS has long been referred to as an ‘undruggable’ target due to its high affinity for its cognate ligands (GDP and GTP) and its lack of... 相似文献
999.
Generation of Oxazolidine‐2,4‐diones Bearing Sulfur‐Substituted Quaternary Carbon Atoms by Oxothiolation/Cyclization of Ynamides 下载免费PDF全文
Hai Huang Junzhen Fan Dr. Guangke He Zhimin Yang Xiaodong Jin Qi Liu Prof. Dr. Hongjun Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2532-2538
A novel method for metal‐free oxothiolation of ynamides to construct oxazolidine‐2,4‐diones bearing sulfur‐substituted quaternary carbon atoms has been developed. It represents a rare C?O bond cleavage of ynamides, as well as a facile and tandem approach for the formation of C?O, C?S, and C?Cl bonds. This redox‐neutral protocol can be applied to the synthesis of multisubstituted oxazolidine‐2,4‐diones with good chemoselectivity and good yields of isolated products under mild conditions. 相似文献
1000.