全文获取类型
收费全文 | 7390篇 |
免费 | 1130篇 |
国内免费 | 1380篇 |
专业分类
化学 | 5331篇 |
晶体学 | 85篇 |
力学 | 477篇 |
综合类 | 224篇 |
数学 | 871篇 |
物理学 | 2912篇 |
出版年
2024年 | 83篇 |
2023年 | 232篇 |
2022年 | 360篇 |
2021年 | 257篇 |
2020年 | 133篇 |
2019年 | 187篇 |
2018年 | 220篇 |
2017年 | 164篇 |
2016年 | 157篇 |
2015年 | 171篇 |
2014年 | 305篇 |
2013年 | 224篇 |
2012年 | 505篇 |
2011年 | 640篇 |
2010年 | 342篇 |
2009年 | 287篇 |
2008年 | 499篇 |
2007年 | 498篇 |
2006年 | 549篇 |
2005年 | 449篇 |
2004年 | 371篇 |
2003年 | 290篇 |
2002年 | 272篇 |
2001年 | 259篇 |
2000年 | 262篇 |
1999年 | 240篇 |
1998年 | 189篇 |
1997年 | 170篇 |
1996年 | 144篇 |
1995年 | 162篇 |
1994年 | 169篇 |
1993年 | 120篇 |
1992年 | 132篇 |
1991年 | 101篇 |
1990年 | 116篇 |
1989年 | 110篇 |
1988年 | 63篇 |
1987年 | 67篇 |
1986年 | 47篇 |
1985年 | 56篇 |
1984年 | 38篇 |
1983年 | 47篇 |
1982年 | 50篇 |
1981年 | 33篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1959年 | 7篇 |
1958年 | 14篇 |
1957年 | 11篇 |
1955年 | 8篇 |
排序方式: 共有9900条查询结果,搜索用时 31 毫秒
1.
Difeng Yin Yucen Li Lingling Xia Wenbo Li Wei Chu Jianping Yu Miao Wu Ya Cheng Ming Hu 《中国化学快报》2022,(2):1077-1080
Despite the continuously increased requirement on automated synthesis of medicines for distributed manufacturing and personal care, it remains a challenge to realize automated synthesis which requires solid-liquid phase reactions. In this work, we demonstrated an automated solid-liquid synthesis for gadopentetate dimeglumine, the most widely used magnetic resonance imaging(MRI) contrast agent. The high-efficiency reaction was performed in a 3 D microfluidic chip which was fabricated by femtoseco... 相似文献
2.
3.
In the present research, hierarchical structure observation and mechanical property characterization for a type of biomaterial are carried out. The investigated biomaterial is Hyriopsis cumingii, a typical limnetic shell, which consists of two different structural layers, a prismatic "pillar"structure and a nacreous "brick and mortar" structure. The prismatic layer looks like a "pillar forest" with variationsection pillars sized on the order of several tens of microns.The nacreous material looks like a "brick wall" with bricks sized on the order of several microns. Both pillars and bricks are composed of nanoparticles. The mechanical properties of the hierarchical biomaterial are measured by using the nanoindentation test. Hardness and modulus are measured for both the nacre layer and the prismatic layer, respectively.The nanoindentation size effects for the hierarchical structural materials are investigated experimentally. The results show that the prismatic nanostructured material has a higher stiffness and hardness than the nacre nanostructured material.In addition, the nanoindentation size effects for the hierarchical structural materials are described theoretically, by using the trans-scale mechanics theory considering both strain gradient effect and the surface/interface effect. The modeling results are consistent with experimental ones. 相似文献
4.
The magnetic skyrmion transport driven by pure voltage-induced strain gradient is proposed and studied via micromagnetic simulation. Through combining the skyrmion with multiferroic heterojunction, a voltage-induced uniaxial strain gradient is adjusted to move skyrmions. In the system, a pair of short-circuited trapezoidal top electrodes can generate the symmetric strain. Due to the symmetry of strain, the magnetic skyrmion can be driven with a linear motion in the middle of the nanostrip without deviation. We calculate the strain distribution generated by the trapezoidal top electrodes pair, and further investigate the influence of the strain intensity as well as the strain gradient on the skyrmion velocity. Our findings provide a stable and low-energy regulation method for skyrmion transport. 相似文献
5.
The Hunga-Tonga-Hunga-Ha’apai volcano in Tonga erupted violently on January 15, 2022. After 8 hours and 39 minutes, an infrasound array in Kunming at a distance of 10151 km away from the volcano recorded a sequence of strong infrasonic waves. The average period of the first four infrasonic waves is 443 s with propagation speed of 321 m/s. The azimuth angle of this event has been estimated by applying the progressive multi-channel correlation(PMCC) method to process the received signals. During c... 相似文献
6.
<正>我们脚下的岩石中可能含有过去暗物质相互作用的残留物,这些残留物以纳米粗的径迹的形式存在着。以前对这些所谓的暗物质化石的寻找没有任何结果。但是瑞典和波兰的研究团队认为,最近在材料分析技术方面的进展,会促进新一 相似文献
7.
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
8.
《电磁学发展史》评介@曾清平¥空军雷达学院@王勇¥华中理工大学电子信息工程系《电磁学发展史》评介曾清平(空军雷达学院,武汉430010)王勇(华中理工大学电子信息工程系,武汉430074)《电磁学发展史》(修定版)是由宋德生先生和李国栋先生合编的,并于19... 相似文献
9.
10.
Wei Gengping~ Shen Jianhua~ 《高校应用数学学报(英文版)》2006,21(3):320-326
This paper studies the nonautonomous nonlinear system of difference equationsΔx(n)=A(n)x(n)+f(n,x(n)),n∈Z,(*) where x(n)∈R~N,A(n)=(a_(ij)(n))N×N is an N×N matrix,with a-(ij)∈C(R,R) for i,j= 1,2,3,...,N,and f=(f_1,f_2,...,f_N)~T∈C(R×R~N,R~N),satisfying A(t+ω)=A(t),f(t+ω,z)=f(t,z) for any t∈R,(t,z)∈R×R~N andωis a positive integer.Sufficient conditions for the existence ofω-periodic solutions to equations (*) are obtained. 相似文献