全文获取类型
收费全文 | 2253篇 |
免费 | 434篇 |
国内免费 | 123篇 |
专业分类
化学 | 1105篇 |
晶体学 | 33篇 |
力学 | 116篇 |
综合类 | 18篇 |
数学 | 143篇 |
物理学 | 1395篇 |
出版年
2024年 | 6篇 |
2023年 | 17篇 |
2022年 | 43篇 |
2021年 | 89篇 |
2020年 | 94篇 |
2019年 | 74篇 |
2018年 | 75篇 |
2017年 | 91篇 |
2016年 | 128篇 |
2015年 | 102篇 |
2014年 | 143篇 |
2013年 | 169篇 |
2012年 | 163篇 |
2011年 | 163篇 |
2010年 | 129篇 |
2009年 | 151篇 |
2008年 | 166篇 |
2007年 | 152篇 |
2006年 | 129篇 |
2005年 | 131篇 |
2004年 | 89篇 |
2003年 | 92篇 |
2002年 | 66篇 |
2001年 | 44篇 |
2000年 | 60篇 |
1999年 | 38篇 |
1998年 | 30篇 |
1997年 | 20篇 |
1996年 | 30篇 |
1995年 | 23篇 |
1994年 | 27篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1966年 | 1篇 |
排序方式: 共有2810条查询结果,搜索用时 406 毫秒
11.
《Surface and interface analysis : SIA》2003,35(4):395-402
Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices—extruded and injection moulded—were studied in the non‐sterilized condition and after 25 and 50 kGy of beta irradiation. The polymer surfaces were analysed by scanning electron microscopy (SEM) equipped with an x‐ray energy‐dispersive spectroscopy (XEDS) and by atomic force microscopy (AFM). The inner surface of two parts of a venous line showed a different morphology according to their original formulation (for extrusion or injection moulding process) and reacted differently on sterilization with beta irradiation. Moulded parts were affected only slightly by the radiation step, whereas the variations were bigger for the extruded parts. In order to gain the best performances for the medical devices studied, the utmost care must be taken in the sterilization step, which should be optimized as well as the other steps of the manufacturing process. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
12.
We investigate a new parallel all-optical clock recovery scheme based on heterodyne beats of an optical sideband-filtered signal. The oscillating clock signal is recovered when the filtered sideband is combined with a stable local oscillator. The filtering is performed with an optical resonator, which by nature provides possibility for multiwavelength operation. The local oscillator could be realized by a multiwavelength laser, whose emission wavelengths are injection seeded with carrier wavelengths of the input data. The output signal of such a configuration benefits from a reduced bit-pattern effect and a stable offset level. The sideband filtering is demonstrated for 23 simultaneous channels at 100 GHz DWDM grid, each hosting a data stream of 10 Gbit/s. 相似文献
13.
Ch. Tsitouras 《Numerical Algorithms》2007,44(3):291-307
Runge–Kutta (RK) pairs furnish approximations of the solution of an initial value problem at discrete points in the interval
of integration. Many techniques for enriching these methods with continuous approximations have been proposed. Here we construct
C
1 continuous, eighth and ninth order interpolation methods for a recently appeared RK pair of orders 9(8). These interpolants
share a very small leading truncation error making them suitable for use at quadruple precision, i.e. 32–33 decimal digits
of accuracy. Extended numerical results justify our effort. 相似文献
15.
用于曲面精密检测的新型光纤三角传感器研究 总被引:1,自引:1,他引:0
基于光纤传感技术和三角测量方法,提出了一种用于曲面检测的新型光纤三角传感器。根据所设计的轮辐式接收光纤结构,可以在测量曲面与传感头间位移时,首先获取被测点处微面元的倾斜信息,以便对传感器测量值进行实时误差修正,从而解决了被测表面倾斜对坐标测量带来的影响。该传感器还能有效地消除环境光干扰、光源波动、表面反射率变化等对测量带来的影响。建立了传感器测量的数学模型。理论分析和初步的实验结果证明了系统的有效性和实用性。该传感器系统不稳定性好于0.3%,横向分辨率好于8μm,高度分辨率好于0.1μm。 相似文献
16.
A. I. Golovashkin G. N. Izmaïlov G. V. Kuleshova T. Q. Khánh A. M. Tskhovrebov L. N. Zherikhina 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):243-249
A scheme of magnetic calorimeter for registration of rare events
characterized by small energy release (cosmic rays, WIMPs, solitary X-ray
quanta) is proposed. The calorimeter is brought to operation by adiabatic
demagnetization, and its magnetic response is measured by a quantum
interferometer (SQUID, A. Barone and G. Paterno, Physics and applications of Josephson Effect). Special consideration is given to the specific
features of calorimeter operation in the ferromagnetic transition region.
The trigger registration of ultrasmall energy release by a ferromagnetic
system in the metastable state is described. 相似文献
17.
18.
19.
20.
M. Froese C. Champagne J. R. Crespo López-Urrutia S. Epp G. Gwinner A. Lapierre J. Pfister G. Sikler J. Ullrich J. Dilling 《Hyperfine Interactions》2006,173(1-3):85-92
The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and,
hence, can be increased by using highly charged ions (HCI). For this reason, charge breeding with an electron beam ion trap
(EBIT) is employed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding
the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased
inside the EBIT. To be compatible with the on-line requirements of short-lived isotopes, very high electron beam current densities
are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies
of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration
within tens of ms. Subsequently, the HCI are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and
injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN
EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear
Physics in Heidelberg, Germany. 相似文献