全文获取类型
收费全文 | 37935篇 |
免费 | 4547篇 |
国内免费 | 3007篇 |
专业分类
化学 | 14926篇 |
晶体学 | 534篇 |
力学 | 1742篇 |
综合类 | 253篇 |
数学 | 4035篇 |
物理学 | 11877篇 |
综合类 | 12122篇 |
出版年
2024年 | 78篇 |
2023年 | 277篇 |
2022年 | 628篇 |
2021年 | 660篇 |
2020年 | 880篇 |
2019年 | 918篇 |
2018年 | 897篇 |
2017年 | 1142篇 |
2016年 | 1376篇 |
2015年 | 1312篇 |
2014年 | 1734篇 |
2013年 | 3274篇 |
2012年 | 2155篇 |
2011年 | 2201篇 |
2010年 | 1814篇 |
2009年 | 1986篇 |
2008年 | 2047篇 |
2007年 | 2323篇 |
2006年 | 2103篇 |
2005年 | 1904篇 |
2004年 | 1820篇 |
2003年 | 1638篇 |
2002年 | 1666篇 |
2001年 | 1285篇 |
2000年 | 1284篇 |
1999年 | 1152篇 |
1998年 | 953篇 |
1997年 | 793篇 |
1996年 | 735篇 |
1995年 | 703篇 |
1994年 | 617篇 |
1993年 | 494篇 |
1992年 | 491篇 |
1991年 | 413篇 |
1990年 | 318篇 |
1989年 | 285篇 |
1988年 | 254篇 |
1987年 | 204篇 |
1986年 | 150篇 |
1985年 | 120篇 |
1984年 | 96篇 |
1983年 | 46篇 |
1982年 | 65篇 |
1981年 | 41篇 |
1980年 | 32篇 |
1979年 | 42篇 |
1978年 | 16篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Tomohiro Shirai 《Optical Review》2004,11(5):312-319
Spatial coherence of the field modified by low-order adaptive optics is analyzed to establish a theoretical basis for the recent idea of using adaptive optics as a spatial coherence modifier. In this context low-order adaptive optics has the ability to correct some of the low-order aberrations specified by Zernike polynomials. The initial field to be modified is assumed to be a spatially partially coherent one resulting from phase disturbance. It is demonstrated, as in the previous study, that low-order adaptive optics serves to enhance the spatial coherence of the resultant field and that the effect of the enhancement becomes stronger as the spatial coherence of the initially partially coherent field increases. Potential applications of low-order adaptive optics as a spatial coherence modifier are briefly discussed. 相似文献
162.
163.
164.
平面物体在曲面状态下扫描仪图像的校正理论 总被引:6,自引:5,他引:1
平面物体在曲面状态下经扫描仪扫描后,其图像将发生复杂的畸变。提出将其分类为灰度畸变、投影畸变和成像畸变。通过理论分析,提出了在二元曲面模型下对投影畸变和成像畸变进行数字校正的方法,给出了对灰度畸变进行数字校正的实用方法。 相似文献
165.
It is shown that the cascaded fifth-order nonlinear phase shifts will increase with energy loss in the cascaded processes. Essentially different from the multi-photon absorption accompanied with inherent material nonlinearities, the loss of fundamental wave in a cascaded process is controllable and suppressible. By introducing difference frequencies generated from the reaction between the fundamental and its second harmonic after the cascaded processes, the fundamental wave can be free of energy loss, while the large cascaded fifth-order nonlinear phase shift is maintained. 相似文献
166.
167.
In this article a new technique was developed to fabricate scaffolds with a unique microstructure by solid–liquid separation in combination with particulate-leaching. Firstly, the effects of polymer concentration, quenching temperature on the porous morphology and the mechanical property of obtained scaffolds during solid–liquid separation have been investigated. Then, salt granules as porogen were introduced into the solid–liquid phase separation to produce the unique pore structure of the scaffold. The pore diameter of the scaffold could be controlled with the particulate size and the wall of pores possessed special microstructure, which enhanced the pore interconnectivity. The cell culture results confirmed that a good interconnectivity of the scaffold prepared by the improved solid–liquid separation was useful for nutrition transportation and cell proliferation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
168.
An alternative discretization of pressure‐correction equations within pressure‐correction schemes for the solution of the incompressible Navier–Stokes equations is introduced, which improves the convergence and robustness properties of such schemes for non‐orthogonal grids. As against standard approaches, where the non‐orthogonal terms usually are just neglected, the approach allows for a simplification of the pressure‐correction equation to correspond to 5‐point or 7‐point computational molecules in two or three dimensions, respectively, but still incorporates the effects of non‐orthogonality. As a result a wide range (including rather high values) of underrelaxation factors can be used, resulting in an increased overall performance of the underlying pressure‐correction schemes. Within this context, a second issue of the paper is the investigation of the accuracy to which the pressure‐correction equation should be solved in each pressure‐correction iteration. The scheme is investigated for standard test cases and, in order to show its applicability to practical flow problems, for a more complex configuration of a micro heat exchanger. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
169.
170.
潜热型热功能流体强化换热分析 总被引:4,自引:0,他引:4
本文建立了分析带有相变微胶囊的潜热型热功能流体的流动和换热过程数理模型,应用有限差分法和移动热源法进行联合求解。计算结果表明,相变微胶囊的加入:较好地提高了流体的换热性能。获得了相变颗粒大小和体积分数对强化换热影响等结果。计算结果对该类流体的设计和应用提供了理论依据。 相似文献