全文获取类型
收费全文 | 4782篇 |
免费 | 353篇 |
国内免费 | 382篇 |
专业分类
化学 | 1728篇 |
晶体学 | 16篇 |
力学 | 337篇 |
综合类 | 21篇 |
数学 | 104篇 |
物理学 | 1581篇 |
综合类 | 1730篇 |
出版年
2024年 | 10篇 |
2023年 | 47篇 |
2022年 | 88篇 |
2021年 | 85篇 |
2020年 | 85篇 |
2019年 | 98篇 |
2018年 | 105篇 |
2017年 | 145篇 |
2016年 | 153篇 |
2015年 | 150篇 |
2014年 | 219篇 |
2013年 | 349篇 |
2012年 | 210篇 |
2011年 | 289篇 |
2010年 | 206篇 |
2009年 | 269篇 |
2008年 | 252篇 |
2007年 | 283篇 |
2006年 | 259篇 |
2005年 | 284篇 |
2004年 | 193篇 |
2003年 | 217篇 |
2002年 | 176篇 |
2001年 | 173篇 |
2000年 | 142篇 |
1999年 | 172篇 |
1998年 | 104篇 |
1997年 | 161篇 |
1996年 | 94篇 |
1995年 | 107篇 |
1994年 | 78篇 |
1993年 | 53篇 |
1992年 | 40篇 |
1991年 | 43篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有5517条查询结果,搜索用时 0 毫秒
31.
Tracks made in minerals by the electronic stopping of uranium fission fragments provide a modern geological dating tool, and are believed also to yield specific information on the low-temperature thermal history of rocks. Experimental work showing that the damaged crystal lattice along a fission track recovers primarily as a function of temperature ignored the fact that the basic theory of atomic diffusion requires an exponential decrease in the intrinsic diffusion coefficient with increasing pressure. Here, fission track recovery was experimentally investigated in basic apatite under the simultaneous influences of temperature, pressure and stress. We show that track fading is a complex recovery mechanism responding to several environmental physical parameters simultaneously. In particular a strong decrease in the track recovery rate was observed as a function of increasing pressure. And a nearly temperature-independent recovery was observed in samples under stress. 相似文献
32.
Al. Ivanov 《International Journal of Theoretical Physics》2004,43(1):77-87
The notion of Fock theory is introduced in the framework of quantum logics, which are here orthomodular atomic lattices satisfying the covering property. It is shown that there are some fundamental facts concerning particles, which may be successfully discussed in this general context. One of these facts is to establish the theoretical conditions for considering particles as sharply defined entities. The other refers to the theoretical circumstances, which almost impose to consider that some particles have a structure, meaning they are composed from other particles. This last problem is strongly related with the conservative time evolutions. 相似文献
33.
对体育教育专业如何与“素质教育”良性接轨进行了探索与研究,旨在能够为全面推进体育教育专业素质教育改革起到抛砖引玉的作用.研究结果表明:设计的教学模式有助于实现从应试教育向素质教育的良性转化;还有助于在普通高校体育教育专业田径专修跨栏教学中增强学生的自信心,提高教与学的效率. 相似文献
34.
35.
本文从簇射粒子分布的 KNO 标度无关性出发,导出了高能重离子碰撞中α粒子分布的 KNO 标度无关性公式.由公式计算的α粒子分布与实验结果相一致. 相似文献
36.
When comparing an urban system to an elasto-plastic lattice, an analogy to the solid state of matter can be exploited using the concepts of the band theory similarly. Thereafter, the population dynamics – in a region of certain stability in the state space and within appropriate energy bands – can be described in terms of Cellular Automata, with two mobile agents or pseudo particles: the inhabitant (representative of an average individual) and the recurson (representative of its multidimensional resources). As in the solid state, transition rules take the form of two coupled transport equations, comprising the terms equivalent to the generation-recombination and circulation processes. The first process can be compared to a predator–prey growth model, typical of Ecology; whereas the circulation process – composed of a drift component and a diffusion component – should be compared to the concentration-sprawl demographic balance seen in urban occupation and dynamics. Thus, it needs to be defined and determined an urban potential function, an equivalent population charge, mobility and diffusion parameters, as well as net growth factors. This analogy, discussed within the context of a case study for Great Mendoza, plausibly explains the varied growth rates of the political departments, as well as the principal urban trends for spatial occupation. 相似文献
37.
Summary The relative X-ray fluorescence (XRF) intensities for annular source and various annular specimen are measured with a Ge-Li
detection system and calculated by the Monte Carlo numerical techniques (MCNT).Kα X-ray intensities of annular specimens with different radii prepared from a pure-molybdenum foil are measured and it is
seen that the measured values are in good agreement with the values calculated by MCNT. The variation of the fluorescence
intensity due to the collimator radius is also studied. The differences between the MCNT and experimental results are discussed
in terms of the possible sources of errors. 相似文献
38.
研究了在美国BNL/AGS上能量10.7AGeV的197Au离子诱发核作用,报告了EMU–01国际合作实验关于射弹核碎裂和产生粒子密度等最新实验结果. 相似文献
39.
S. Banerjee 《Pramana》1998,51(1-2):77-86
We summarize here the recent results from the four experiments at the large electron positron collider (LEP). These experiments
provide precise measurements of theW and Z boson properties and their couplings to leptons and quarks. These measurements, together with measurements of the top
quark andW boson masses in the Tevatron collider provide a stringent test of the standard electroweak theory. Searches for Higgs boson
and supersymmetric particles have yielded null results so far giving rise to lower bounds in the parameter space. 相似文献
40.
Jos Vargas Carlos Ramos Roberto D. Zysler Hctor Romero 《Physica B: Condensed Matter》2002,320(1-4):178-180
Chemically prepared (CoxNi1−x)1−yBy (x=0.5, 0.75, 1; y≈0.4) amorphous fine particles were characterized by X-ray diffraction, DTA and TGA, and in situ magnetic measurement as a function of annealing temperature in an inert atmosphere. Magnetic measurement performed in as-prepared and 150°C annealed samples shows an increase of the saturation magnetization and magnetic moment after thermal treatment. Room temperature magnetization increases by factors of 3.5, 1.8, and 1.5, for x=0.5, 0.75, and 1, respectively. These measurements may indicate a local re-ordering of the amorphous phase at temperatures much lower than the full crystallization temperature. 相似文献