全文获取类型
收费全文 | 24778篇 |
免费 | 1334篇 |
国内免费 | 1036篇 |
专业分类
化学 | 14240篇 |
晶体学 | 158篇 |
力学 | 1882篇 |
综合类 | 44篇 |
数学 | 3441篇 |
物理学 | 7383篇 |
出版年
2021年 | 345篇 |
2020年 | 473篇 |
2019年 | 543篇 |
2018年 | 548篇 |
2017年 | 539篇 |
2016年 | 754篇 |
2015年 | 533篇 |
2014年 | 706篇 |
2013年 | 936篇 |
2012年 | 1090篇 |
2011年 | 1169篇 |
2010年 | 972篇 |
2009年 | 882篇 |
2008年 | 981篇 |
2007年 | 957篇 |
2006年 | 813篇 |
2005年 | 723篇 |
2004年 | 666篇 |
2003年 | 621篇 |
2002年 | 625篇 |
2001年 | 584篇 |
2000年 | 428篇 |
1999年 | 389篇 |
1998年 | 326篇 |
1997年 | 339篇 |
1996年 | 327篇 |
1995年 | 322篇 |
1994年 | 269篇 |
1993年 | 298篇 |
1992年 | 294篇 |
1991年 | 307篇 |
1990年 | 328篇 |
1989年 | 310篇 |
1985年 | 295篇 |
1984年 | 292篇 |
1983年 | 264篇 |
1982年 | 284篇 |
1980年 | 257篇 |
1979年 | 300篇 |
1978年 | 329篇 |
1977年 | 320篇 |
1976年 | 405篇 |
1975年 | 357篇 |
1974年 | 389篇 |
1973年 | 395篇 |
1972年 | 368篇 |
1971年 | 331篇 |
1970年 | 314篇 |
1969年 | 298篇 |
1968年 | 253篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Physics of the Solid State - The phase transitions in the two-dimensional diluted Potts model with the number of spin states q = 3 are studied by computer simulation method. The systems... 相似文献
2.
Hu Duo-Duo Gao Qian Dai Jing-Cheng Cui Ru Li Yuan-Bo Li Yuan-Ming Zhou Xiao-Guo Bian Kang-Jie Wu Bing-Bing Zhang Kai-Fan Wang Xi-Sheng Li Yan 《中国科学:化学(英文版)》2022,65(4):753-761
Science China Chemistry - A light-induced, nickel-catalyzed three-component arylsulfonation of 1,3-enynes in the absence of photocatalyst is reported. This methodology exhibited mild conditions,... 相似文献
3.
Eliovich Ya. A. Blagov A. E. Kocharyan V. R. Gogolev A. S. Targonsky A. V. Movsisyan A. E. Korzhov V. A. Mkrtchyan A. R. Kovalchuk M. V. 《JETP Letters》2022,115(3):148-152
JETP Letters - Features of the simultaneous action of longitudinal and transverse ultrasonic vibrations in the quartz crystal on the parameters of reflected X-rays are studied. It is shown that... 相似文献
4.
Shklover V. Ya. Kazanskii P. R. Artemov N. A. Maryasev I. G. 《Crystallography Reports》2021,66(4):663-672
Crystallography Reports - The development of fundamental and applied geology requires an ever-increasing amount of data on the structures and properties of rocks at different scales. Of particular... 相似文献
5.
Journal of Experimental and Theoretical Physics - In this paper, we consider Hamiltonian structures of hydrodynamic type and some of their generalizations. In particular, we discuss the questions... 相似文献
6.
Volk T. R. Bodnarchuk Ya. V. Gainutdinov R. V. Kokhanchik L. S. Shandarov S. M. 《JETP Letters》2021,113(12):769-779
JETP Letters - Studies of ferroelectric nano- and microdomain structures formed in LiNbO3-based optical waveguides are reviewed. Nanodomain structures of a given configuration have been written in... 相似文献
7.
Nonlinear Dynamics - The hybrid neural model provides a computationally effective and biophysics-based neuron behavior model, which maintains its simplicity by incorporating the dynamics... 相似文献
8.
The looming global energy crisis and ever-increasing energy demands have catalyzed the development of renewable energy storage systems. In this regard, supercapacitors (SCs) have attracted widespread attention because of their advantageous attributes such as high power density, excellent cycle stability, and environmental friendliness. However, SCs exhibit low energy density and it is important to optimize electrode materials to improve the overall performance of these devices. Among the various electrode materials available, spinel nickel cobaltate (NiCo2O4) is particularly interesting because of its excellent theoretical capacitance. Based on the understanding that the performances of the electrode materials strongly depend on their morphologies and structures, in this study, we successfully synthesized NiCo2O4 nanosheets on Ni foam via a simple hydrothermal route followed by calcination. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis, and the results showed that they were uniformly distributed on the Ni foam support. The surface chemical states of the elements in the samples were identified by X-ray photoelectron spectroscopy. The as-synthesized NiCo2O4 products were then tested as cathode materials for supercapacitors in a traditional three-electrode system. The electrochemical performances of the NiCo2O4 electrode materials were studied and the area capacitance was found to be 1.26 C·cm-2 at a current density of 1 mA·cm-2. Furthermore, outstanding cycling stability with 97.6% retention of the initial discharge capacitance after 10000 cycles and excellent rate performance (67.5% capacitance retention with the current density from 1 to 14 mA·cm-2) were achieved. It was found that the Ni foam supporting the NiCo2O4 nanosheets increased the conductivity of the electrode materials. However, it is worth noting that the contribution of nickel foam to the areal capacitance of the electrode materials was almost zero during the charge and discharge processes. To further investigate the practical application of the as-synthesized NiCo2O4 nanosheets-based electrode, a device was assembled with the as-prepared samples as the positive electrode and active carbon (AC) as the negative electrode. The assembled supercapacitor showed energy densities of 0.14 and 0.09 Wh·cm-3 at 1.56 and 4.5 W·cm-3, respectively. Furthermore, it was able to maintain 95% of its initial specific capacitance after 10000 cycles. The excellent electrochemical performance of the NiCo2O4 nanosheets could be ascribed to their unique spatial structure composed of interconnected ultrathin nanosheets, which facilitated electron transportation and ion penetration, suggesting their potential applications as electrode materials for high performance supercapacitors. The present synthetic route can be extended to other ternary transition metal oxides/sulfides for future energy storage devices and systems. 相似文献
9.
Yongtao Bai Lihua Song Yongheng Zhang Guoliang Dai Weidong Zhang Shanshan Song Hong Sun Wen Jing Meijuan Xu Wenzheng Ju 《Biomedical chromatography : BMC》2019,33(9)
A highly selective and efficient LC–MS/MS method was developed to determine the plasma concentration of magnolol, hesperidin, neohesperidin and geniposide following oral administration of Zhi‐Zi‐Hou‐Po decoction in normal and depressed rats. Plasma samples were pretreated by protein precipitation with methanol. Chromatographic separation was performed on an XTerra® MS C18 column using a gradient elution with a mobile phase composed of acetonitrile–0.1% aqueous formic acid. The proposed method was validated to be specific, accurate and precise for the analytes determination in plasma samples. The calibration curves displayed good linearity over definite concentration ranges for the analytes. The intra‐ and inter‐day precision of the proposed method at three different levels were all within <11.13% and the relative errors ranged from ?8.46 to 8.93%. The recovery of the four compounds ranged from 82.72 to 89.08% and no apparent matrix effect was observed during sample analysis. After full validation, the established method was successfully applied for comparing the pharmacokinetics of four components between normal and depressed rats. The results showed that the AUC and Cmax of four analytes in depressed rats were significantly different from those in normal rats and might provide helpful information to guide the clinical use of Zhi‐Zi‐Hou‐Po to treat depression. 相似文献
10.
International Applied Mechanics - The geometry and kinematics of a dynamic system with several degrees of freedom and controllable friction clutches are considered. The necessary kinematic... 相似文献