全文获取类型
收费全文 | 3956篇 |
免费 | 216篇 |
国内免费 | 21篇 |
专业分类
化学 | 3099篇 |
晶体学 | 42篇 |
力学 | 166篇 |
数学 | 297篇 |
物理学 | 589篇 |
出版年
2023年 | 19篇 |
2022年 | 39篇 |
2021年 | 68篇 |
2020年 | 73篇 |
2019年 | 64篇 |
2018年 | 45篇 |
2017年 | 49篇 |
2016年 | 134篇 |
2015年 | 109篇 |
2014年 | 167篇 |
2013年 | 244篇 |
2012年 | 344篇 |
2011年 | 324篇 |
2010年 | 236篇 |
2009年 | 191篇 |
2008年 | 292篇 |
2007年 | 249篇 |
2006年 | 229篇 |
2005年 | 213篇 |
2004年 | 183篇 |
2003年 | 141篇 |
2002年 | 156篇 |
2001年 | 101篇 |
2000年 | 78篇 |
1999年 | 62篇 |
1998年 | 34篇 |
1997年 | 34篇 |
1996年 | 52篇 |
1995年 | 25篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 7篇 |
排序方式: 共有4193条查询结果,搜索用时 22 毫秒
951.
952.
953.
954.
955.
Rigid polyurethane foams have been fabricated from polymeric MDI and polypropylene glycols (PPG) synthesized with two different initiator compositions using two different types of blowing agents, viz., the conventional HCFC 141b and environmently friendly HFC 365 mfc. It was found that the two blowing agents gave identically the same cream time, gel time, and tack‐free time. The HFC 365 mfc gave foams with smaller cell size, greater core density and compression strength, whereas HCFC 141b gave better dimensional stability and thermal insulation. For the same type of blowing agent, the initiator containing more toluene diamine gave greater core density, compression strength and thermal insulation 相似文献
956.
957.
Sung Ho Yang Woo‐Jae Chung Sean McFarland Seung‐Wuk Lee 《Chemical record (New York, N.Y.)》2013,13(1):43-59
For the last decade, the fabrication of ordered structures of phage has been of great interest as a means of utilizing the outstanding biochemical properties of phage in developing useful materials. Combined with other organic/inorganic substances, it has been demonstrated that phage is a superior building block for fabricating various functional devices, such as the electrode in lithium‐ion batteries, photovoltaic cells, sensors, and cell‐culture supports. Although previous research has expanded the utility of phage when combined with genetic engineering, most improvements in device functionality have relied upon increases in efficiency owing to the compact, more densely packable unit size of phage rather than on the unique properties of the ordered nanostructures themselves. Recently, self‐templating methods, which control both thermodynamic and kinetic factors during the deposition process, have opened up new routes to exploiting the ordered structural properties of hierarchically organized phage architectures. In addition, ordered phage films have exhibited unexpected functional properties, such as structural color and optical filtering. Structural colors or optical filtering from phage films can be used for optical phage‐based sensors, which combine the structural properties of phage with target‐specific binding motifs on the phage‐coat proteins. This self‐templating method may contribute not only to practical applications, but also provide insight into the fundamental study of biomacromolecule assembly in in vivo systems under complicated and dynamic conditions. 相似文献
958.
The operation of an ambipolar field‐effect transistor (FET) is described using a simple diagram depicting the gate voltage and channel potential profile relative to the injection threshold voltage of charge carriers. From this diagram, the transition between transistor‐operation regimes and the resulting current–voltage relations can be easily understood. Also, a practical guidance for the operation of an ambipolar FET is provided. In particular, conditions to achieve the true ambipolar regime, which is of particular interest for light‐emitting transistor operation, and a correct method to extract electron and hole mobilities from a given current–voltage curve are presented. 相似文献
959.
Synchronization of chaos presents many challenges for controller design. The novel notion of exerting concurrent control in the joint time-frequency domain is applied to formulate a chaos synchronization scheme that requires no linearization or heuristic trial-and-errors for nonlinear controller design. The concept is conceived through recognizing the basic attributes inherent of all chaotic systems, including the simultaneous deterioration of dynamics in both the time and frequency domains when bifurcates, nonstationarity, and sensitivity to initial conditions. Having its philosophical bases established in simultaneous time-frequency control, on-line system identification, and adaptive control, the chaos synchronization scheme incorporates multiresolution analysis, adaptive filters, and filtered-x Least Mean Square algorithm as its physical features. Without A priori knowledge of the driven system parameters, synchronization is invariably achieved regardless of the initial and forcing conditions the response system is subjected to. In addition, driving and driven trajectories are seen robustly synchronized with negligible errors in spite of the infliction of high frequency noise. 相似文献
960.
Sunmi Kim Do-Kun Yoon Han-Back Shin Moo-Sub Kim Tae Suk Suh 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(3):1059-1065
This study analyzed the effectiveness attained through generation of three alpha particles in proton-boron fusion therapy (PBFT) based on a Monte Carlo simulation. PBFT is based on a fusion reaction between protons and boron. Three alpha particles are emitted from this reaction. The three alpha particles cause greater damage to tumor cells than the single alpha particle produced in the boron neutron capture reaction or conventional therapy. In addition, the intrinsic proton dose pattern follows Bragg-peak curve. We confirmed an energy deposition by the alpha particle and verified the therapeutic effect of the PBFT. 相似文献