全文获取类型
收费全文 | 24649篇 |
免费 | 4351篇 |
国内免费 | 4206篇 |
专业分类
化学 | 17487篇 |
晶体学 | 367篇 |
力学 | 1763篇 |
综合类 | 381篇 |
数学 | 3061篇 |
物理学 | 10147篇 |
出版年
2024年 | 54篇 |
2023年 | 429篇 |
2022年 | 618篇 |
2021年 | 830篇 |
2020年 | 968篇 |
2019年 | 926篇 |
2018年 | 796篇 |
2017年 | 774篇 |
2016年 | 1078篇 |
2015年 | 1159篇 |
2014年 | 1356篇 |
2013年 | 1818篇 |
2012年 | 2090篇 |
2011年 | 2356篇 |
2010年 | 1646篇 |
2009年 | 1607篇 |
2008年 | 1708篇 |
2007年 | 1594篇 |
2006年 | 1593篇 |
2005年 | 1326篇 |
2004年 | 1120篇 |
2003年 | 831篇 |
2002年 | 784篇 |
2001年 | 722篇 |
2000年 | 681篇 |
1999年 | 551篇 |
1998年 | 439篇 |
1997年 | 383篇 |
1996年 | 384篇 |
1995年 | 372篇 |
1994年 | 346篇 |
1993年 | 268篇 |
1992年 | 290篇 |
1991年 | 230篇 |
1990年 | 216篇 |
1989年 | 178篇 |
1988年 | 113篇 |
1987年 | 115篇 |
1986年 | 94篇 |
1985年 | 84篇 |
1984年 | 59篇 |
1983年 | 58篇 |
1982年 | 44篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1975年 | 6篇 |
1965年 | 5篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
61.
62.
袁文俊 《数学物理学报(A辑)》2003,23(2):224-230
该文考虑具有控制系数 A\-0 和系数仅有有限个极点的高阶线性齐次微分方程(1.1)。得到了一个复振荡结果,该结果是J. K. Langley[11]等作者在整系数下相应结果的推广。 相似文献
63.
64.
固态金属中声子热传递的分子动力学模拟研究 总被引:2,自引:0,他引:2
固态金属中的热传递是声子和自由电子共同作用的结果。自由电子引起的热导率可以通过电导率,利用Wiedemann-Franz定律得到,声子引起的热导率目前仍然不能进行实验测量,只能借助其他方法来研究。本文采用非平衡分子动力学(NEMD)方法,用镶嵌原子方法(EAM)势能模型,模拟计算了不同厚度(1.760-10.56nm)金属镍薄膜中由于声子-声子作用引起的热导率。然后根据纳米厚度金属薄膜的热导率借助关联式推到宏观尺度下由于声子-声子作用引起的热导率。结果表明,对于纳米厚度金属薄膜,由于声子-声子作用引起的热导率比块体金属镍的热导率小一个数量级;薄膜厚度越小,声子-声子作用引起的热导率越小;对于块体金属镍,由于声子-声子作用引起的热导率约占其总热导率的33.0%左右。 相似文献
65.
66.
We study the spectral characteristics theoretically and experimentally in the Fraunhofer diffraction pattern formed by the diffraction of a spatially coherent, polychromatic light through a slit. It is found that the spectrum in some diffraction directions close to the singular direction is redshifted, compared to the spectrum of the incident polychromatic light, and blueshifted in other directions, and splits into two lines at the singular direction. We show that the experimental results are consistent with the theoretical expectations. 相似文献
67.
Ping Li Fei Rong Yibing Xie Van Hu Chunwei Yuan 《Journal of Analytical Chemistry》2004,59(10):939-944
S-naproxen imprinted polymer was prepared with acrylamide as a functional monomer, 1,4-butanediyl diacrylate as a new kind of crossliner, and 2,4,6-trimethylbenzoylphenyl-phosphinic acid ethyl ester as photoinitiator. Their UV and IR spectra were applied to study the interactions between the template and the monomer. Binding experiments showed that the S-naproxen imprinted polymer had better recognition capability for the template than that of a blank polymer. The adsorption distribution coefficient KD of S-naproxen on molecularly-imprinted polymer was 153.2 g/mL, and the separation factor was 1.95 when the initial concentration of substrate was 2.0 mmol/L. Scatchard curves suggested that there were two classes of binding sites in the imprinted polymer and only one class in the blank polymer. Computer simulation using Hyperchem showed the existence of the interactions between the template and the functional monomer as well as the models of the complexes formed by the template and the monomer. 相似文献
68.
Efforts are made to explore the hysteresis characteristics of vortex shedding in a pipe flow, whose velocity varies periodically in time. Results obtained show that during acceleration of the flow, the vortex strength tends to be stronger, whereas during deceleration of the flow, the situation is reversed. As reconstructed from the velocity signals measured at a point in the flow field, the shed vortex arrays appear to possess uneven vortex strengths in response to periodically-varying incoming flows. Furthermore, in the hysteresis range, the streamwise spacings between the vortices appear to be unequal. 相似文献
69.
Kosuke Morita Kouji Morimoto Daiya Kaji Yu Liang Zhao Atsushi Yoshida Toshimi Suda Akira Yoneda Tetsuya Ohnishi Hiromitsu Haba Eiji Ideguchi Hu Shan Xu Tao Zheng Hisaaki Kudo Keisuke Sueki Kenji Katori Isao Tanihata 《Acta Physica Hungarica A》2004,19(1-2):53-60
A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element 271[110] have been performed using the 208Pb(64Ni,1n)271[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope 271[110] of element 110. 相似文献
70.
Yu‐Hsiang Hu Chuh‐Yung Chen Chen‐Chien Wang Yao‐Hui Huang Shao‐Ping Wang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(19):4976-4993
The bulk polymerization of styrene initiated by ?‐caprolactam (CL) and n‐dodecyl mercaptan (RSH) has been explored. This novel polymerization system shows living characteristics. For example, the molecular weight of the resulting polymers increases with conversion, and the system has the ability to form diblock copolymers and so forth. The polymer chain end contains thiol and lactam structures, which we have investigated with Fourier transform infrared, 1H NMR, and 13C NMR techniques. Electron spin resonance spectra and theoretical calculations by the Hartree–Fock methods have been used to examine the mechanism. The results reveal that the initial polymerization starts from thiol via a chain‐transfer reaction, and the propagation proceeds by the insertion of a monomer between the terminal group and the intermediate structure of lactam. Finally, the polymerization kinetics have been examined. The polymerization rate varies linearly with the concentration of CL and RSH, and this confirms the mechanism. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4976–4993, 2004 相似文献