全文获取类型
收费全文 | 2475篇 |
免费 | 296篇 |
国内免费 | 195篇 |
专业分类
化学 | 1841篇 |
晶体学 | 29篇 |
力学 | 134篇 |
综合类 | 15篇 |
数学 | 225篇 |
物理学 | 722篇 |
出版年
2024年 | 6篇 |
2023年 | 52篇 |
2022年 | 60篇 |
2021年 | 73篇 |
2020年 | 121篇 |
2019年 | 95篇 |
2018年 | 71篇 |
2017年 | 70篇 |
2016年 | 129篇 |
2015年 | 97篇 |
2014年 | 121篇 |
2013年 | 182篇 |
2012年 | 187篇 |
2011年 | 227篇 |
2010年 | 120篇 |
2009年 | 111篇 |
2008年 | 147篇 |
2007年 | 141篇 |
2006年 | 99篇 |
2005年 | 97篇 |
2004年 | 81篇 |
2003年 | 75篇 |
2002年 | 82篇 |
2001年 | 76篇 |
2000年 | 57篇 |
1999年 | 58篇 |
1998年 | 30篇 |
1997年 | 28篇 |
1996年 | 21篇 |
1995年 | 16篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 20篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有2966条查询结果,搜索用时 15 毫秒
1.
2.
Monomeric sarcosine oxidase (mSOx) fusion with the silaffin peptide, R5, designed previously for easy protein production in low resource areas, was used in a biosilification process to form an enzyme layer electrode biosensor. mSOx is a low activity enzyme (10–20 U/mg) requiring high amounts of enzyme to obtain an amperometric biosensor signal, in the clinically useful range <1 mM sarcosine, especially since the Km is >10 mM. An amperometric biosensor model was fitted to experimental data to investigate dynamic range. mSOx constructs were designed with 6H (6×histidine) and R5 (silaffin) peptide tags and compared with native mSOx. Glutaraldehyde (GA) cross‐linked proteins retained ~5 % activity for mSOx and mSOx‐6H and only 0.5 % for mSOx‐R5. In contrast R5 catalysed biosilification on (3‐mercaptopropyl) trimethoxysilane (MPTMS) and tetramethyl orthosilicate (TMOS) particles created a ‘self‐immobilisation’ matrix retaining 40 % and 76 % activity respectively. The TMOS matrix produced a thick layer (>500 μm) on a glassy carbon electrode with a mediated current due to sarcosine in the clinical range for sarcosinemia (0–1 mM). The mSOx‐R5 fusion protein was also used to catalyse biosilification in the presence of creatinase and creatininase, entrapping all three enzymes. A mediated GC enzyme linked current was obtained with dynamic range available for creatinine determination of 0.1–2 mM for an enzyme layer ~800 nm. 相似文献
3.
Yasuhiro Ikezoe Sadahiro Ishizaki Hiroharu Yui Masanori Fujinami Tsuguo Sawada 《Analytical sciences》2004,20(3):435-440
The oscillation of the interfacial tension and electrical potential at a water/nitrobenzene interface was observed with homologous anionic surfactant molecules, sodium-alkyl-sulfates. Concerning small molecules with a short hydrophobic carbon chain, the oscillation period and amplitude decreased with a decrease of the length of the alkyl chain. On the other hand, when surfactant molecules with a long hydrophobic carbon chain were used, no remarkable periodic oscillation occurred after the first oscillation. In all systems, an interfacial flow by Marangoni convection was observed when the oscillation took place. By monitoring the movement of carbon powder scattered on the liquid/liquid interface with a CCD camera, we could observe that the liquid/liquid interface expanded outward from the area on which the surfactant molecules adsorbed when the oscillation occurred. When the small molecule was used, the speed of expansion of the interface (flow speed) was small and shrinkage followed by expansion of the interface repeatedly occurred. However, when the large molecule was used, the flow speed was large and expansion occurred only one time. These results show that hydrodynamic factors and surface activities are important in chemical oscillation systems. 相似文献
4.
Molecules in inhomogeneous liquid environments, such as air/liquid, liquid/liquid, solid/liquid interfaces interact with each other specifically, and sometimes form characteristic structures and emerge unique properties. Here, we introduce two newly developed spectroscopic techniques, the total-internal-reflection ultrafast transient lens method (TIR-UTL) and second harmonic generation-coherent vibrational spectroscopy (SHG-CVS), to investigate the characteristic behaviors of molecules in such inhomogeneous environments. TIR-UTL probes the refractive-index change with sub-picosecond resolution and provides information on ultrafast changes in the population, density, and thermal properties, such as temperature increase and energy transfer from the solute molecules to the surrounding solvent molecules. On the other hand, SHG-CVS probes nonlinear susceptibility changes at the interfacial areas, and is expected to provide spectroscopic information on the low-frequency vibrational modes that reflect the corrective motion of the molecules in such an inhomogeneous environment. These new approaches are based on pump-probe techniques utilizing (ultra) short laser pulses. They are expected to provide further information on inhomogeneous environments from the viewpoints of solute-solvent interactions, changes in the molecular orientation, and the corrective motion of molecules at liquid interfaces. 相似文献
5.
6.
7.
8.
Zhengqian Luo Guoyong Sun Zhiping Cai Miaoling Si Qibo Li 《Optics Communications》2007,277(1):118-124
In this paper, continuous wave Yb3+-doped double-clad fiber lasers (DCFLs) with linear-cavity are investigated theoretically and numerically using the rate equations. Under the steady state conditions, the simplified analytic solutions of Yb3+-doped DCFLs under considering the scattering loss are deduced in the strongly pump condition. Compared with the known analytic solutions in published literatures, our analytic solutions are more accurate, especially, at higher reflectivity of output mirror. In addition, a fast and stable algorithm based on the Newton-Raphson method is proposed to simulate numerically Yb3+-doped DCFLs. The results by simplified analytic solutions are in good agreement with those by the numerical simulation. Moreover, we have performed the optimization of an Yb3+-doped DCFL using the simplified analytic solutions and the numerical simulations, respectively. 相似文献
9.
10.
低温太阳热能与化学链燃烧相结合控制CO2分离动力系统 总被引:3,自引:1,他引:2
本文探索并提出控制CO2分离的低温太阳热能与清洁合成燃料甲醇-三氧化二铁化学链燃烧相结合的新颖能源动力系统。基于图象(?)分析方法,明确地指出甲醇化学链燃烧能量释放过程燃烧堋损失减小和低温太阳热能品位提升的机理。从能源有效利用和环境相容出发,研究和揭示化学链燃烧与太阳能有机整合共同减小CO2分离能耗的特性规律。相比不分离常规联合循环,新系统(?)效率提高约6.2个百分点;与分离CO2的联合循环相比,新系统媚效率提高约14.2个百分点。同时,低温太阳热能热转功效率可达到22.5%。 相似文献