全文获取类型
收费全文 | 25254篇 |
免费 | 3746篇 |
国内免费 | 2406篇 |
专业分类
化学 | 17875篇 |
晶体学 | 268篇 |
力学 | 1653篇 |
综合类 | 196篇 |
数学 | 2547篇 |
物理学 | 8867篇 |
出版年
2024年 | 76篇 |
2023年 | 436篇 |
2022年 | 796篇 |
2021年 | 865篇 |
2020年 | 922篇 |
2019年 | 892篇 |
2018年 | 744篇 |
2017年 | 651篇 |
2016年 | 1117篇 |
2015年 | 1151篇 |
2014年 | 1326篇 |
2013年 | 1815篇 |
2012年 | 2133篇 |
2011年 | 2366篇 |
2010年 | 1504篇 |
2009年 | 1397篇 |
2008年 | 1550篇 |
2007年 | 1421篇 |
2006年 | 1377篇 |
2005年 | 1164篇 |
2004年 | 1031篇 |
2003年 | 764篇 |
2002年 | 722篇 |
2001年 | 596篇 |
2000年 | 532篇 |
1999年 | 494篇 |
1998年 | 412篇 |
1997年 | 348篇 |
1996年 | 379篇 |
1995年 | 354篇 |
1994年 | 332篇 |
1993年 | 264篇 |
1992年 | 271篇 |
1991年 | 220篇 |
1990年 | 199篇 |
1989年 | 162篇 |
1988年 | 101篇 |
1987年 | 95篇 |
1986年 | 86篇 |
1985年 | 83篇 |
1984年 | 46篇 |
1983年 | 46篇 |
1982年 | 43篇 |
1981年 | 26篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1974年 | 6篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Close‐Packed Two‐Dimensional Silver Nanoparticle Arrays: Quadrupolar and Dipolar Surface Plasmon Resonance Coupling 下载免费PDF全文
Sukang Yun Soonchang Hong Jesus A. I. Acapulco Jr. Ho Young Jang Songyi Ham Kyungeun Lee Prof. Seong Kyu Kim Prof. Sungho Park 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6165-6172
Silver nanoparticles (NPs) ranging in size from 40 to 100 nm were prepared in high yield by using an improved seed‐mediated method. The homogeneous Ag NPs were used as building blocks for 2D assembled Ag NP arrays by using an oil/water interface. A close‐packed 2D array of Ag NPs was fabricated by using packing molecules (3‐mercaptopropyltrimethoxysilane) to control the interparticle spacing. The homogeneous 2D Ag NP array exhibited a strong quadrupolar cooperative plasmon mode resonance and a dipolar red‐shift relative to individual Ag NPs suspended in solution. A well‐arranged 2D Ag NP array was embedded in polydimethylsiloxane film and, with biaxial stretching to control the interparticle distance, concomitant variations of the quadrupolar and dipolar couplings were observed. As the interparticle distance increased, the intensity of the quadrupolar cooperative plasmon mode resonance decreased and dipolar coupling completely disappeared. The local electric field of the 2D Ag NP array was calculated by using finite difference time domain simulation and qualitatively showed agreement with the experimental measurements. 相似文献
3.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes 下载免费PDF全文
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
4.
Star copolymers have attracted significant interest due to their different characteristics compared with diblock copolymers, including higher critical micelle concentration, lower viscosity, unique spatial shape, or morphologies. Development of synthetic skills such as anionic polymerization and controlled radical polymerization have made it possible to make diverse architectures of polymers. Depending on the molecular architecture of the copolymer, numerous morphologies are possible, for instance, Archimedean tiling patterns and cylindrical microdomains at symmetric volume fraction for miktoarm star copolymers as well as asymmetric lamellar microdomains for star‐shaped copolymers, which have not been reported for linear block copolymers. In this review, we focus on morphologies and microphase separations of miktoarm (AmBn and ABC miktoarm) star copolymers and star‐shaped [(A‐b‐B)n] copolymers with nonlinear architecture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1–21 相似文献
5.
S. Q. Hou W. Wang Z. Y. Wang Z. W. Hu K. Liu 《Journal of Applied Mechanics and Technical Physics》2018,59(1):153-162
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages. 相似文献
6.
7.
8.
9.
10.
We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160. 相似文献