全文获取类型
收费全文 | 17262篇 |
免费 | 5440篇 |
国内免费 | 1211篇 |
专业分类
化学 | 2675篇 |
晶体学 | 287篇 |
力学 | 1528篇 |
综合类 | 99篇 |
数学 | 436篇 |
物理学 | 18888篇 |
出版年
2024年 | 33篇 |
2023年 | 104篇 |
2022年 | 274篇 |
2021年 | 321篇 |
2020年 | 370篇 |
2019年 | 281篇 |
2018年 | 361篇 |
2017年 | 520篇 |
2016年 | 618篇 |
2015年 | 619篇 |
2014年 | 1140篇 |
2013年 | 1163篇 |
2012年 | 1099篇 |
2011年 | 1560篇 |
2010年 | 1106篇 |
2009年 | 1217篇 |
2008年 | 1331篇 |
2007年 | 1444篇 |
2006年 | 1296篇 |
2005年 | 1070篇 |
2004年 | 1043篇 |
2003年 | 860篇 |
2002年 | 855篇 |
2001年 | 730篇 |
2000年 | 743篇 |
1999年 | 629篇 |
1998年 | 532篇 |
1997年 | 463篇 |
1996年 | 402篇 |
1995年 | 318篇 |
1994年 | 256篇 |
1993年 | 222篇 |
1992年 | 209篇 |
1991年 | 158篇 |
1990年 | 133篇 |
1989年 | 101篇 |
1988年 | 69篇 |
1987年 | 73篇 |
1986年 | 38篇 |
1985年 | 28篇 |
1984年 | 30篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
V. S. Gorelik P. P. Sverbil' A. B. Fadyushin V. V. Vasil'ev 《Journal of Russian Laser Research》2004,25(1):54-63
A possibility of application of semiconductor lasers of the visible range as exciting sources for Raman spectroscopy is studied. An experimental set-up for measuring Raman spectra of polycrystalline dielectrics and broad-gap semiconductors excited by a semiconductor laser with a wavelength of 640 nm was created. The conditions under which the spectral width of the lasing line of a semiconductor laser was within 10-3 cm-1 in the continuous mode with a power of 10 mW are realized. The characteristics of various types of exciting sources used in Raman spectroscopy are compared. The results of studies of the characteristic Raman spectra excited with a semiconductor laser in polycrystalline sulfur are presented. 相似文献
23.
A. N. Logunov 《Journal of Russian Laser Research》2004,25(4):331-348
A physical multidimensional local model of the propagation process of a laser pulse in air having no analogy to famous models in laser physics is constructed. It is based on the representations of classical wave mechanics characteristic of the theory of scalar wave fields. 相似文献
24.
K. Sakurai Y. Kondo K. Miyazaki T. Okamoto S. Irie T. Sasaki 《Journal of Polymer Science.Polymer Physics》2004,42(13):2595-2603
Aiming to develop a high‐performance fiber‐reinforced rubber from styrene–butadiene rubber (SBR), we applied a special technique using electron‐beam (EB)‐irradiation‐induced graft polymerization to ultrahigh‐molecular‐weight‐polyethylene (UHMWPE) fibers. The molecular interaction between the grafted UHMWPE fibers and an SBR matrix was studied through the evaluation of the adhesive behavior of the fibers in the SBR matrix. Although UHMWPE was chemically inert, two monomers, styrene and N‐vinyl formamide (NVF), were examined for graft polymerization onto the UHMWPE fiber surface. Styrene was not effective, but NVF was graft‐polymerized onto the UHMWPE fibers with this special method. A methanol/water mixture and dioxane were used as solvents for NVF, and the effects of the solvents on the grafting percentage of NVF were also examined. The methanol/water mixture was more effective. A grafting percentage of 16.4% was the highest obtained. This improved the adhesive force threefold with respect to that of untreated UHMWPE fibers. These results demonstrated that EB irradiation enabled graft polymerization to occur even on the inert surface of UHMWPE fibers. However, the mechanical properties of the fibers could be compromised according to the dose of EB irradiation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2595–2603, 2004 相似文献
25.
26.
从激光推进的要求出发,阐述了用于激光推进的高功率激光器的选择原则,即激光器必须满足:(1)高的平均功率和峰值功率;(2)高的单脉冲能量;(3)高的重复频率;(4)优良的大气传输特性。主要分析了目前YAG固体激光器、自由电子激光器和TEA脉冲CO2激光器的特点,通过上述4个方面性能的比较,认为在目前水平下,TEA脉冲CO2激光器是进行激光推进的首选强激光源,其优点表现在:功率可达10kW量级,单脉冲能量可达0.5~1kJ,重复频率为20~40Hz;激光波长处于大气传输窗口,对大气变化不敏感;工作物质快速流动,不存在热透镜效应和破坏阈值;相关光学元件易于制造;光束质量较好;运行成本低。 相似文献
27.
Mari Grobbelaar‐Van Dalsen 《Mathematical Methods in the Applied Sciences》2004,27(11):1301-1315
This paper is concerned with well‐posedness results for a mathematical model for the transversal vibrations of a two‐dimensional hybrid elastic structure consisting of a rectangular Reissner–Mindlin plate with a Timoshenko beam attached to its free edge. The model incorporates linear dynamic feedback controls along the interface between the plate and the beam. Classical semigroup methods are employed to show the unique solvability of the coupled initial‐boundary‐value problem. We also show that the energy associated with the system exhibits the property of strong stability. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
28.
Until recently, simple and reliable high repetition-rate laser sources with nanosecond pulses much shorter than from conventional A-O Q-switch lasers were not available. However over the past 2 years we have developed such lasers based on proprietary fast E-O switching technology, which allows designs delivering 1 ns pulses and subnanosecond jitter for good synchronisation. The technology provides pulses with multi-kW peak power and repetition-rates to >100 kHz.Most recently, the performance of these short pulse lasers has been developed further by implementing oscillator/amplifier (master oscillator and power amplifier, MOPA) technology which increases the output to >1 W average power. Here we report on a simple model that has been used to predict the performance of the CW pumped Nd:YVO4 amplifier used in the MOPA laser. The model is based on the well-known expressions for the saturated gain applying to laser pulses, but more usually applied to pulse-excited amplifiers. The model is shown to allow a good interpretation of the amplifier behaviour for kHz pulses and to be a useful tool for predicting the performance of the MOPA laser. 相似文献
29.
I. Peshko G. Galich M. Lopiychuk A. Khizhnyak V. Nakvasuk 《Optics & Laser Technology》1997,29(4):211-215
A laser system containing four CW Nd:YAG double-rod lasers, transforming optics and a fibre with input-output optics has been designed and investigated. It is shown that reduction of the beam parameter product of the non-Gaussian beams in the image space of the lens has made it possible to collect the emission of four lasers to the same fibre. Independent laser operation has provided the output power control in the range of 10–900 W with a stable light spot size on the input end of the fibre. 相似文献
30.