全文获取类型
收费全文 | 21550篇 |
免费 | 3547篇 |
国内免费 | 2576篇 |
专业分类
化学 | 15570篇 |
晶体学 | 238篇 |
力学 | 1417篇 |
综合类 | 140篇 |
数学 | 2549篇 |
物理学 | 7759篇 |
出版年
2024年 | 68篇 |
2023年 | 459篇 |
2022年 | 797篇 |
2021年 | 780篇 |
2020年 | 877篇 |
2019年 | 851篇 |
2018年 | 773篇 |
2017年 | 717篇 |
2016年 | 1122篇 |
2015年 | 1052篇 |
2014年 | 1299篇 |
2013年 | 1665篇 |
2012年 | 1977篇 |
2011年 | 1936篇 |
2010年 | 1362篇 |
2009年 | 1280篇 |
2008年 | 1490篇 |
2007年 | 1296篇 |
2006年 | 1169篇 |
2005年 | 983篇 |
2004年 | 707篇 |
2003年 | 551篇 |
2002年 | 552篇 |
2001年 | 425篇 |
2000年 | 376篇 |
1999年 | 390篇 |
1998年 | 315篇 |
1997年 | 283篇 |
1996年 | 306篇 |
1995年 | 282篇 |
1994年 | 215篇 |
1993年 | 172篇 |
1992年 | 166篇 |
1991年 | 158篇 |
1990年 | 141篇 |
1989年 | 117篇 |
1988年 | 104篇 |
1987年 | 80篇 |
1986年 | 58篇 |
1985年 | 58篇 |
1984年 | 44篇 |
1983年 | 37篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 25篇 |
1979年 | 10篇 |
1978年 | 20篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Deposition of Hydrogen-Free Silicon Nitride Thin Films by Microwave ECR plasma Enhanced Magnetron Sputtering at Room Temperature
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hydrogen-free silicon nitride (SiNx) films were deposited at room temperature by microwave electron cyclotron resonance (MW-ECR) plasma enhanced unbalance magnetron sputtering system. Both Fourier-transform infrared spectroscopy and x-ray photoelectron spectroscopy are used to study the bonding type and the change of bonding structures of the silicon nitride films. The results indicate that the chemical structure and composition of SiNx films deposited by this technique depend strongly on the N2 flow rates, the stoichiometric SiNx film, which has the highest hardness of 22.9 GPa, could be obtained at lower N2 flow rate of 4 sccm. 相似文献
42.
使用结构简单的单温炉设备,通过三步升温热解二茂铁、三聚氰氨混合物方法,在二氧化硅、多晶陶瓷基底上分别合成了碳纳米管阵列、碳纳米管捆束.使用扫描电子显微镜、透射电子显微镜、电子能量损失谱和x射线光电子能谱对合成样品进行了结构和成分分析.结果显示:两种基底上合成的纳米管均为多壁纯碳管;生长于光滑二氧化硅表面的碳纳米管具有高度取向性和一致的外径,长度为10—40μm.碳纳米管采取催化剂顶端生长模式并展示出类杯状形貌;生长于粗糙多晶陶瓷表面的碳纳米管捆束随机取向,碳纳米管直径为15—80nm,长度在几百微米,展示
关键词:
碳纳米管
热解法
三步升温工艺 相似文献
43.
A signed graph has a plus or minus sign on each edge. A simple cycle is positive or negative depending on whether it contains an even or odd number of negative edges, respectively. We consider embeddings of a signed graph in the projective plane for which a simple cycle is essential if and only if it is negative. We characterize those signed graphs that have such a projective-planar embedding. Our characterization is in terms of a related signed graph formed by considering the theta subgraphs in the given graph. 相似文献
44.
45.
46.
Qing An WU Zhen Yuan XU Mei ZHENG Dan Qian XU Jun XU Yin Chu SHENCollege of Chemical Engineering Materials Zhejiang University of Technology Hangzhou 《中国化学快报》2004,(7)
Six new 13-O-acylavermectin Bl aglycones(3-8) were synthesized from avermectin B1 aglycone and their bioactivities were evaluated against Spodoptera exigua, Spodoptera eridania, Tetranychus urticae and Aphis fabae. 相似文献
47.
Baker‘s yeast mediated reduction of optically active diketone is described. The two keto groups are efficiently differentiated and the ee value of the recovered material is considerably raised. It affords highly optically active key intermediates efficiently for the synthesis of natural polyhydroxylated agarofuran products. 相似文献
48.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
49.
In this paper we focus on the problem of identifying the index sets P(x):=i|xi>0, N(x):={i|Fi(x)>0 and C(x):=i|xi=Fi(x)=0} for a solution x of the monotone nonlinear complementarity problem NCP(F). The correct identification of these sets is important from both theoretical and practical points of view. Such an identification enables us to remove complementarity conditions from the NCP and locally reduce the NCP to a system which can be dealt with more easily. We present a new technique that utilizes a sequence generated by the proximal point algorithm (PPA). Using the superlinear convergence property of PPA, we show that the proposed technique can identify the correct index sets without assuming the nondegeneracy and the local uniqueness of the solution.This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan.Mathematics Subject Classification (2000): 90C33, 65K10 相似文献
50.
Continuous dependence on a modelling parameter is established for solutions of a problem for a complex Ginzburg–Landau equation. A homogenizing boundary condition is also used to discuss the continuous dependence results. We derive a priori estimates that indicate that solutions depend continuously on a parameter in the governing differential equation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献