全文获取类型
收费全文 | 9558篇 |
免费 | 1557篇 |
国内免费 | 947篇 |
专业分类
化学 | 6871篇 |
晶体学 | 103篇 |
力学 | 528篇 |
综合类 | 55篇 |
数学 | 1083篇 |
物理学 | 3422篇 |
出版年
2024年 | 31篇 |
2023年 | 169篇 |
2022年 | 323篇 |
2021年 | 323篇 |
2020年 | 367篇 |
2019年 | 348篇 |
2018年 | 314篇 |
2017年 | 285篇 |
2016年 | 428篇 |
2015年 | 452篇 |
2014年 | 528篇 |
2013年 | 720篇 |
2012年 | 860篇 |
2011年 | 847篇 |
2010年 | 588篇 |
2009年 | 553篇 |
2008年 | 623篇 |
2007年 | 518篇 |
2006年 | 525篇 |
2005年 | 424篇 |
2004年 | 392篇 |
2003年 | 286篇 |
2002年 | 282篇 |
2001年 | 210篇 |
2000年 | 151篇 |
1999年 | 166篇 |
1998年 | 153篇 |
1997年 | 163篇 |
1996年 | 157篇 |
1995年 | 122篇 |
1994年 | 116篇 |
1993年 | 93篇 |
1992年 | 60篇 |
1991年 | 52篇 |
1990年 | 61篇 |
1989年 | 42篇 |
1988年 | 28篇 |
1987年 | 23篇 |
1986年 | 35篇 |
1985年 | 28篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 22篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Frequency-hopping spread spectrum and direct-sequence spread spectrum are two main spread coding technologies in communication systems. Frequency-hopping sequences are needed in FH-CDMA systems. In this paper, a construction of optimal sets of frequency-hopping sequences using cyclotomy and the Chinese remainder theorem is introduced. It generalizes some earlier constructions, and produces new optimal sets of frequency-hopping sequences. 相似文献
992.
Robust adaptive synchronization of uncertain complex networks with multiple time‐varying coupled delays
下载免费PDF全文
![点击此处可从《Complexity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this article, the synchronization problem of uncertain complex networks with multiple coupled time‐varying delays is studied. The synchronization criterion is deduced for complex dynamical networks with multiple different time‐varying coupling delays and uncertainties, based on Lyapunov stability theory and robust adaptive principle. By designing suitable robust adaptive synchronization controllers that have strong robustness against the uncertainties in coupling matrices, the all nodes states of complex networks globally asymptotically synchronize to a desired synchronization state. The numerical simulations are given to show the feasibility and effectiveness of theoretical results. © 2014 Wiley Periodicals, Inc. Complexity 20: 62–73, 2015 相似文献
993.
Tian Tian Mengling Liu Yinhui Li Jian Han Liang Ren Heike Lorenz Qing Wu Jianxin Chen 《Particuology》2022,(3):88-97
Textile wastewater contains highly toxic,nondegradable,carcinogenic organic pollutants,causing severe damage to the ecological environment.In this work,β-cyclod... 相似文献
994.
Qinhua Wei Hongsheng Shi Xiaofeng Cheng Laishun Qin Guohao Ren Kangying Shu 《Journal of Crystal Growth》2010,312(11):1883-1885
The growth and scintillation properties of the Na2W2O7 crystal are reported. The solid reaction between Na2CO3 and WO3 is used to synthesise the Na2W2O7 material. The Na2W2O7 single crystal has been grown by the Bridgman method. And the Na2W2O7 single crystal with sizes 14×7×6 mm3 has been achieved. The transmission spectra, the Ultraviolet fluorescence spectra and the X-ray excited luminescence spectra of the Na2W2O7 crystal are measured. The measurement results show that the Na2W2O7 crystal is a promising intrinsic scintillator. 相似文献
995.
Dongmei Liu Yanqing SuXinzhong Li Liangshu LuoJingjie Guo Hengzhi Fu 《Journal of Crystal Growth》2010,312(24):3658-3664
Experiments on Al–25 at%Ni peritectic alloy consisting of melting followed by thermal stabilization ranging from 0 to 2 h were carried out in a Bridgman-type furnace. Temperature distribution, microstructure evolution and solute concentration in the mushy zone are characterized. An analytical model is proposed to evaluate the Ni concentration of the melt after thermal stabilization. Effect of temperature gradient and volume fraction of liquid phase in the mushy zone on the Ni concentration of the melt is discussed. The steady state Ni concentration of the melt is inappropriately below the initial Ni concentration of the sample. The deviation increases with decreasing temperature gradient. Finally, the influence of thermal stabilization on the solute concentration of the melt is discussed based on a comparison of Al–Ni peritectic alloys with Al–Ni hyper-eutectic alloys and Al–Cu hypo-eutectic alloys. 相似文献
996.
Pál Perjési Gábor Maász Renáta Reisch András Benkő 《Monatshefte für Chemie / Chemical Monthly》2012,143(8):1107-1114
997.
Sandra Cruz Sylvain Bernès Pankaj Sharma Rosa Vazquez Guadalupe Hernández Roberto Portillo René Gutiérrez 《应用有机金属化学》2010,24(1):8-11
Optically pure α‐diimines quantitatively obtained in solvent‐free conditions starting from 2,3‐butanedione and (S)‐(?)‐1‐phenylethylamine and (S)‐(?)‐1‐(4‐methylphenyl)ethylamine, respectively, yielded the new chiral mono‐Pd complexes 2a–b, which have been partly characterized by IR, 1H‐ and 13C‐NMR spectroscopies along with MS‐FAB+ spectrometry. The crystal and molecular structure for palladacycle 2a has been fully confirmed by single‐crystal X‐ray studies. Studies in vitro of 2a–b have displayed growth inhibition against different classes of cancer: leukemia (K‐562 CML), colon cancer (HCT‐15), breast cancer (MCF‐7), central nervous system (U‐251 Glio) and prostate cancer (PC‐3) cell lines. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
998.
GMM-based Wald tests tend to overreject when used for small samples, mainly due to inaccurate estimation of the weighting matrix. This article proposes applying the shrinkage method to address this problem. Using a possibly-misspecified factor model, the shrinkage method can provide a good estimator for the weighting matrix, and hence improve the finite-sample performance of the GMM-based Wald tests. 相似文献
999.
1000.