全文获取类型
收费全文 | 19085篇 |
免费 | 3431篇 |
国内免费 | 1693篇 |
专业分类
化学 | 13204篇 |
晶体学 | 179篇 |
力学 | 1088篇 |
综合类 | 67篇 |
数学 | 2042篇 |
物理学 | 7629篇 |
出版年
2024年 | 124篇 |
2023年 | 429篇 |
2022年 | 734篇 |
2021年 | 770篇 |
2020年 | 764篇 |
2019年 | 757篇 |
2018年 | 742篇 |
2017年 | 590篇 |
2016年 | 983篇 |
2015年 | 880篇 |
2014年 | 1095篇 |
2013年 | 1421篇 |
2012年 | 1732篇 |
2011年 | 1762篇 |
2010年 | 1159篇 |
2009年 | 1083篇 |
2008年 | 1197篇 |
2007年 | 1040篇 |
2006年 | 991篇 |
2005年 | 788篇 |
2004年 | 608篇 |
2003年 | 425篇 |
2002年 | 434篇 |
2001年 | 333篇 |
2000年 | 276篇 |
1999年 | 389篇 |
1998年 | 276篇 |
1997年 | 292篇 |
1996年 | 284篇 |
1995年 | 245篇 |
1994年 | 211篇 |
1993年 | 215篇 |
1992年 | 143篇 |
1991年 | 159篇 |
1990年 | 130篇 |
1989年 | 99篇 |
1988年 | 89篇 |
1987年 | 73篇 |
1986年 | 70篇 |
1985年 | 55篇 |
1984年 | 58篇 |
1983年 | 31篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1978年 | 13篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1973年 | 15篇 |
1968年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
Wen-Xiu Ma 《Physics letters. A》2011,375(45):3931-3935
By combining two pieces of bi-directional Wronskian solutions, molecule solutions in Wronskian form are presented for the finite, semi-infinite and infinite bilinear 2D Toda molecule equations. In the cases of finite and semi-infinite lattices, separated-variable boundary conditions are imposed. The Jacobi identities for determinants are the key tool employed in the solution formulations. 相似文献
222.
With the three-dimensional symmetry and wide potential application, spherical array signal processing has been a hot research area for years. This paper devotes to the direction-of-arrival (DOA) estimation of the spherical arrays. Based on the orthogonality of the sensors’ location, MUSIC algorithm in spherical space is proposed, named as SH-MUSIC. Similar to beamspace MUSIC, spherical harmonics transformation is operated before MUSIC algorithm and a better performance is gotten because SH-MUSIC utilizes the array configuration’s orthogonality. On account of the transformation matrix’s orthogonality, spherical harmonics transformation is suggested to be operated firstly in other improved MUSIC algorithms without rejection, and it is demonstrated in beamspace MUSIC. In addition, owing to the tiny error between the steering vectors and the spherical harmonics with high order, sphere array data models including open sphere and rigid sphere are constructed. Simulation proves SH-MUSIC to be effective. Moreover, experimental data from a rigid sphere microphone array is dealt with by SH-MUSIC and the DOAs are estimated accurately. 相似文献
223.
Herein, we report a facile approach for rapid and maskless production of subwavelength structured antireflective surfaces with high and broadband transmittance-direct laser interference ablation. The interfered laser beams were introduced into the surface of a bare optical substrate, where structured surfaces consisting of a micropillar array were produced by two-step laser irradiation in the time frame of seconds. A multiple exposure of the two-beam interference approach was proposed instead of multiple-beam interference to simply realize planar patterns of a high aspect ratio. Tall sinusoidal pillars were created and shaped by pulse shot number control. As an example of the application, zinc sulfide substrates were processed with the technology, from which high transmission at an infrared wavelength, over 92%, at normal incidence was experimentally achieved. 相似文献
224.
研究了痂囊腔菌素A(EA)与肌红蛋白(Mb)的相互作用.通过紫外-可见吸收光谱研究发现痂囊腔菌素A与肌红蛋白在避光与光照两种条件作用模式存在明显差异;痂囊腔菌素A对肌红蛋白的内源荧光有猝灭作用,形成了新的配合物,属于静态猝灭;热力学计算结果表明痂囊腔菌素A与肌红蛋白之间以疏水作用力结合.同步荧光光谱研究了痂囊腔菌素A对... 相似文献
225.
The t–J model is analysed in the limit of strong anisotropy, where the transverse components of electron spin are neglected. We propose a slave-particle-type approach that is valid, in contradiction to many of the standard approaches, in the low-doping regime and becomes exact for a half-filled system. We describe an effective method that allows to numerically study the system with the no-double-occupancy constraint rigorously taken into account at each lattice site. Then, we use this approach to demonstrate the destruction of the antiferromagnetic order by increasing the doping and formation of Nagaoka polarons in the strong interaction regime. 相似文献
226.
227.
1689-nm diode lasers used in medical apparatus have been fabricated and characterized. The lasers had pnpn InP current confinement structure, and the active region consisted of 5 pairs of InGaAs quantum wells and InGaAsP barriers. 相似文献
228.
新一代运载火箭时序仿真系统具有数字电路速度快、集成度高的特点,系统要求发出多路高精度时序、时串信号以满足新一代运载火箭地面测试设备的检查与校准需求,因此信号完整性问题在系统设计中不容忽视。针对仿真系统的典型模块(USB 3.0 Super-speed差分线、FPGA外设数据走线、时钟走线)进行建模分析仿真得出PCB硬件电路设计参数,给出时序仿真系统设计信号完整性问题的抑制和解决方法,优化了板级信号质量,改善系统可靠性、工作连续性和输出精度,可有效提高新一代运载火箭测试效率和测试可靠性。 相似文献
229.
由于大部分环境样品的浓度非常低,为了实现其直接检测,提出将一种集成化的微型富集器应用到色谱系统中。富集器可实现色谱系统的进样与样品富集,能将色谱仪的检测限提高1~2个数量级。设计的富集器采用了高容量4平行通道结构,沟道内填充了高吸附率的Tenax-TA吸附材料,来实现对环境样品中挥发性有机化合物组分的富集。此外,为了密闭热解吸过程中所释放的组分,在微型富集器后集成了微型阀。试验结果表明,研制的微型富集器取得了15倍以上的富集因子。而且,通过微阀的控制,色谱峰的拖尾和峰展宽得到了有效的控制。因此,该微型富集器可广泛应用到环境样品的快速检测中,提高各检测器对复杂环境的适应能力。 相似文献
230.