全文获取类型
收费全文 | 18515篇 |
免费 | 3344篇 |
国内免费 | 2894篇 |
专业分类
化学 | 14564篇 |
晶体学 | 234篇 |
力学 | 1044篇 |
综合类 | 198篇 |
数学 | 2211篇 |
物理学 | 6502篇 |
出版年
2024年 | 24篇 |
2023年 | 315篇 |
2022年 | 515篇 |
2021年 | 572篇 |
2020年 | 792篇 |
2019年 | 759篇 |
2018年 | 650篇 |
2017年 | 543篇 |
2016年 | 925篇 |
2015年 | 924篇 |
2014年 | 1150篇 |
2013年 | 1392篇 |
2012年 | 1597篇 |
2011年 | 1758篇 |
2010年 | 1283篇 |
2009年 | 1244篇 |
2008年 | 1373篇 |
2007年 | 1199篇 |
2006年 | 1139篇 |
2005年 | 911篇 |
2004年 | 779篇 |
2003年 | 636篇 |
2002年 | 834篇 |
2001年 | 600篇 |
2000年 | 532篇 |
1999年 | 397篇 |
1998年 | 279篇 |
1997年 | 234篇 |
1996年 | 257篇 |
1995年 | 199篇 |
1994年 | 180篇 |
1993年 | 148篇 |
1992年 | 113篇 |
1991年 | 102篇 |
1990年 | 72篇 |
1989年 | 64篇 |
1988年 | 60篇 |
1987年 | 36篇 |
1986年 | 38篇 |
1985年 | 35篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 4篇 |
1981年 | 14篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1974年 | 3篇 |
1957年 | 3篇 |
1930年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
11.
Dr. Feifan Wang Jie Tian Dr. Mengzhu Li Dr. Weizhen Li Dr. Lifang Chen Xiaozhi Liu Dr. Jian Li Aidaer Muhetaer Prof. Dr. Qi Li Prof. Dr. Yuan Wang Prof. Dr. Lin Gu Prof. Dr. Ding Ma Prof. Dr. Dongsheng Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8280-8286
Fully utilizing solar energy for catalysis requires the integration of conversion mechanisms and therefore delicate design of catalyst structures and active species. Herein, a MOF crystal engineering method was developed to controllably synthesize a copper–ceria catalyst with well-dispersed photoactive Cu-[O]-Ce species. Using the preferential oxidation of CO as a model reaction, the catalyst showed remarkably efficient and stable photoactivated catalysis, which found practical application in feed gas treatment for fuel cell gas supply. The coexistence of photochemistry and thermochemistry effects contributes to the high efficiency. Our results demonstrate a catalyst design approach with atomic or molecular precision and a combinatorial photoactivation strategy for solar energy conversion. 相似文献
12.
Understanding defect production in an hcp Zr crystal upon irradiation:An energy landscape perspective
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Primary radiation damage in hcp Zr,including both defect production in a single collision cascade and damage buildup through cascade overlap,is investigated using molecular dynamics(MD)simulations from a potential energy landscape(PEL)perspective.It is found that the material’s response to an energetic particle can be understood as a trajectory in the PEL comprising a fast uphill journey and a slow downhill one.High-temperature-induced damage reduction and the difference in the radiation tolerance between metals and semiconductors can be both qualitatively explained by the dynamics of the trajectory associated with the topographic features of the system’s PEL.Additionally,by comparing irradiation and heating under a nearly identical condition,we find that large atomic displacements stemming from the extreme locality of the energy deposition in irradiation events are the key factor leading to radiation damage in a solid.Finally,we discuss the advantages of the PEL perspective and suggest that a combination of the PEL and the traditional crystallographic methods may provide more insights in future work. 相似文献
13.
Here, we report a new strategy for rapid synthesis of branched peptide by side-chain hydrazide ligation at Asn. The hydrazide was converted to thioester at Asn side chain by NaNO2 and thiol reagent, and sequential ligation with an N-terminus Cys-peptide efficiently afforded the branched peptide. A branched cyclic peptide was successfully synthesized by side-chain ligation with a two-Cys-peptide and formation of a disulfide bond. This approach provides a new way for expeditious synthesis of branched peptides and facilitates the design of neopeptides as functional bio-mimics. 相似文献
14.
15.
采用顶部籽晶提拉法(TSSG)生长出Yb:KY(WO4)2(Yb:KYW)激光晶体.对预烧后的原料及晶体进行了XRD分析,结果表明,分别在920℃和600℃预烧8h后的熔质和助熔剂基本上形成一相,抑止了实验中的挥发问题;所生长的晶体为β-Yb:KYW,计算其晶格常数为a=1.063nm,b=1.034nm,c=0.755nm,β=130.75°.测得不同厚度样品的吸收光谱,结果表明样品在933nm和981nm有较强的吸收峰,计算出主峰981nm的吸收截面σ关键词:
Yb:KYW
TSSG法
晶体结构
光谱参数 相似文献
16.
瞄准线高精度稳定是机载光电稳瞄系统的主要指标和关键技术。根据四框架稳瞄系统的工作原理,以手动跟踪模式为主要研究对象,建立了稳瞄伺服控制系统模型。考虑到直升机扰动特点,对线扰动、角速率扰动、摩擦力矩、弹性力矩等各种扰动因素也建立相应的数学模型,同时在各种扰动因素作用下利用Matlab对机载高精度稳瞄系统的手动跟踪控制模式进行了仿真设计分析和理论研究,设计出适合的控制器。此模型在实际系统中获得验证,对稳瞄伺服控制系统的设计具有参考意义。 相似文献
17.
L. Tong Y. Tian Q. Y. Wang Y. S. Ling 《International Journal of Infrared and Millimeter Waves》2006,27(9):1307-1314
The paper introduces a special system calibration technology in s-parameters measurement of microwave and millimeter wave
devices. The 8-term errors module is built by analyzing the signals flowing in the measurement system. Then the calibration
technology using non-standard kits is designed on the base. Finally, the experiment using the calibration technology is introduced. 相似文献
18.
19.
20.
Proton conductivity of phosphoric acid derivative of fullerene 总被引:1,自引:0,他引:1
The proton conductive property of methano [60] fullerene diphosphoric acid has been investigated under various humidity conditions at the temperature range between 15 and 45 °C. It shows proton conductivity as high as 10−2 S cm−1 at 25 °C under relative humidity of 95%. Thermal analyses including TG–DTA and thermal desorption mass spectroscopy (TDS) confirm that the compound is thermally stable up to 200 °C. Proton conduction of the compound depends very much on humidity or water content. The logarithmic conductivity at 25 °C is increased linearly with increasing relative humidity. The activation energy (Ea) estimated from the slope of log(σT) vs. 1/T is decreased from 1.08 to 0.52 eV, as the relative humidity is increased from 40% to 75%. The humidity dependence of conductivity is discussed in the light of the observed hydration isotherm. 相似文献