全文获取类型
收费全文 | 21529篇 |
免费 | 3377篇 |
国内免费 | 3528篇 |
专业分类
化学 | 16323篇 |
晶体学 | 449篇 |
力学 | 1251篇 |
综合类 | 356篇 |
数学 | 2453篇 |
物理学 | 7602篇 |
出版年
2024年 | 38篇 |
2023年 | 299篇 |
2022年 | 570篇 |
2021年 | 637篇 |
2020年 | 770篇 |
2019年 | 763篇 |
2018年 | 598篇 |
2017年 | 668篇 |
2016年 | 921篇 |
2015年 | 935篇 |
2014年 | 1171篇 |
2013年 | 1569篇 |
2012年 | 1824篇 |
2011年 | 1935篇 |
2010年 | 1511篇 |
2009年 | 1336篇 |
2008年 | 1539篇 |
2007年 | 1384篇 |
2006年 | 1433篇 |
2005年 | 1209篇 |
2004年 | 977篇 |
2003年 | 791篇 |
2002年 | 913篇 |
2001年 | 669篇 |
2000年 | 624篇 |
1999年 | 500篇 |
1998年 | 343篇 |
1997年 | 313篇 |
1996年 | 297篇 |
1995年 | 285篇 |
1994年 | 237篇 |
1993年 | 205篇 |
1992年 | 201篇 |
1991年 | 159篇 |
1990年 | 149篇 |
1989年 | 119篇 |
1988年 | 106篇 |
1987年 | 74篇 |
1986年 | 78篇 |
1985年 | 70篇 |
1984年 | 42篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1976年 | 5篇 |
1974年 | 4篇 |
1964年 | 4篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
81.
ZHOU Ming-Xiua② YANG Chuna DENG Xiao-Yana YU Wei-Feib LI Jin-Shanb a 《结构化学》2006,25(6):647-652
1 INTRODUCTION Silicon and its alloy have been widely applied in such fields as electronic industry, high-temperature structural ceramics, etc. In addition, the researches on silicon and its relevant materials greatly promote the rapid development of modern optics and infor- mation technology. Therefore, more and more at- tention is focused on the structure of silicon, oxide of silicon and the interfaces between silicon and metal or nonmetal. As an ideal passive film on the Si surface, S… 相似文献
82.
Yong‐Jin Kim Jin‐Woong Kim Jung‐Eun Lee Jee‐Hyun Ryu Junoh Kim Ih‐Seop Chang Kyung‐Do Suh 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5627-5635
Mesoporous polymer microspheres with gold (Au) nanoparticles inside their pores were prepared considering their surface functionality and porosity. The Au/polymer composite microspheres prepared were characterized by transmission electron microscope (TEM), X‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) techniques. The results showed that the adsorption of Au nanoparticles could be increased by imparting the pore structure and surface‐functional groups into the supporting polymer microspheres (in this study, poly (ethylene glycol dimethacrylate‐co‐acrylonitrile) and poly (EGDMA‐co‐AN) system). Above all, from this study, it was established that the porosity of the polymer microspheres is the most important factor that determines the distribution and adsorption amount of face‐centered cubic (fcc) Au nanoparticles in the final products. Our study showed that the continuous adsorption of Au nanoparticles with the aid of the large surface area and surface interaction sites formed more favorably the Au/polymer composite microspheres. The BET measurements of Au/poly(EGDMA‐co‐AN) composite microspheres reveals that the adsorption of Au nanoparticles into the pores kept the pore structure intact and made it more porous. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5627–5635, 2004 相似文献
83.
高阶线性微分方程的解及其解的导数的不动点 总被引:2,自引:0,他引:2
研究了复域齐次和非齐次线性微分方程的解及其解的导数的不动点与超级问题,得到了整函数系数的齐次和非齐次线性微分方程的解及其解的导数的不动点的两个结果,所得结果推广了一些相关结果. 相似文献
84.
Zhen‐Feng Chen Hong‐Li Zhou Hong Liang Yan Li Ren‐Gen Xiong Xiao‐Zeng You 《应用有机金属化学》2003,17(11):883-884
The centrosymmetric binuclear structure of [Pb2(H‐Norf)2(ONO2)4]shows the geometry around each lead(II) atom to be distorted trigonal bipyramidal with Pb–O distances ranging from 2.357(3) to 2.769(4) Å. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
85.
Hilbert空间上线性算子的Drazin可逆性 总被引:1,自引:0,他引:1
主要研究了Hilbert空间上两个Drazin可逆算子和的Drazin可逆性.同时,对上三角算子矩阵的Drazin可逆性也给出了详细的讨论. 相似文献
86.
87.
Hua Jin Zhuangqi Hu Qingmin Liu Yunlong Ge Changxu Shi 《Applied Physics A: Materials Science & Processing》1992,54(5):399-403
A crystallization study has been carried out for rapidly solidified Bi2Pb0.5Sr2Ca4Cu5Ox glass. Glass transition temperature T
g, crystallized superconducting phases and microstructural changes were measured and analysed by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The crystallization mechanism of the three superconducting phases — (2201) 20 K phase, (2212) 80 K phase, and (2223) 110 K phase — has been discussed, and a time-temperature-transformation diagram for the glass has been constructed. 相似文献
88.
89.
在电流及温度分布满足“不变性”原理的基础上,本文分析了等离子体中心热区的能量平衡,求出了电子热传导系数,根据实验数据拟合出HL-1装置电子热传导系数的定标关系为X_e=6.8(n_(eq1))~(-1.2)。此关系与其他托卡马克装置的结果类似。 相似文献
90.
Traveling wave Ti:LiNbO3 Mach-Zehnder optical modulators with buried electrodes and etched grooves in the SiO2 buffer layer are analyzed by the finite element method. The tradeoff between the bandwidth BW and the half-wave voltage Vπ is discussed. The value of BW/Vπ is used to weight the total performance of the modulator. Taking a thick buffer layer and etching deep grooves in the buffer layer are demonstrated as two effective methods to improve the performance of the modulator. A 3-dB optical bandwidth of 18 GHz with half-wave voltage 5V at a wavelength of 1.55 pm could be obtained even though the electrode is not very thick. When the requirement of half-wave voltage is not very critical, a bandwidth of more than 100 GHz can be obtained. 相似文献