全文获取类型
收费全文 | 700454篇 |
免费 | 7920篇 |
国内免费 | 2105篇 |
专业分类
化学 | 371849篇 |
晶体学 | 10344篇 |
力学 | 32446篇 |
综合类 | 28篇 |
数学 | 87004篇 |
物理学 | 208808篇 |
出版年
2021年 | 5927篇 |
2020年 | 6489篇 |
2019年 | 7311篇 |
2018年 | 9664篇 |
2017年 | 9510篇 |
2016年 | 13962篇 |
2015年 | 8486篇 |
2014年 | 13401篇 |
2013年 | 31603篇 |
2012年 | 24065篇 |
2011年 | 29233篇 |
2010年 | 21248篇 |
2009年 | 21041篇 |
2008年 | 27331篇 |
2007年 | 27172篇 |
2006年 | 25050篇 |
2005年 | 22530篇 |
2004年 | 20712篇 |
2003年 | 18469篇 |
2002年 | 18367篇 |
2001年 | 19940篇 |
2000年 | 15423篇 |
1999年 | 12037篇 |
1998年 | 10054篇 |
1997年 | 9960篇 |
1996年 | 9556篇 |
1995年 | 8437篇 |
1994年 | 8480篇 |
1993年 | 8332篇 |
1992年 | 9182篇 |
1991年 | 9340篇 |
1990年 | 8876篇 |
1989年 | 8739篇 |
1988年 | 8714篇 |
1987年 | 8550篇 |
1986年 | 8100篇 |
1985年 | 10591篇 |
1984年 | 10906篇 |
1983年 | 8774篇 |
1982年 | 9077篇 |
1981年 | 8925篇 |
1980年 | 8318篇 |
1979年 | 9055篇 |
1978年 | 9343篇 |
1977年 | 9289篇 |
1976年 | 9290篇 |
1975年 | 8601篇 |
1974年 | 8532篇 |
1973年 | 8749篇 |
1972年 | 6219篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
911.
Applied Magnetic Resonance - We examined by electron spin resonance (ESR) spectroscopy the thermal decay of radicals as induced by γ-irradiation on pepper. Upon irradiation, the satellite... 相似文献
912.
A nonlinear (in the cubic approximation) relaxation equation of state is derived for a rod containing cracks partially filled with an incompressible viscous liquid. The nonlinear effects of the self-action and interaction of low-and high-frequency longitudinal elastic waves propagating in such a rod are studied for the cases of identical and size-varied cracks. Linear and nonlinear acoustic parameters characterizing the self-action and interaction of elastic waves in a cracked rod are determined. 相似文献
913.
H. G. Bohlen W. von Oertzen R. Kalpakchieva B. Gebauer S. M. Grimes A. Lenz T. N. Massey M. Milin Ch. Schulz Tz. Kokalova S. Torilov S. Thummerer 《Physics of Atomic Nuclei》2003,66(8):1494-1500
The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion-induced transfer reactions. In neutron transfer reactions, the population of final states shows a strong sensitivity to the chosen core nucleus, i.e., the target nuclei 9Be or 10Be, respectively. Molecular rotational bands up to high excitation energies are observed with 9Be as the core due to its pronounced 2α-cluster structure, whereas only a few states at low excitation energies are populated with 10Be as the core. For 11Be, a detailed investigation has been performed for the three states at 3.41, 3.89, and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2+, 5/2?, and 3/2?, respectively. Furthermore, we have studied particle-hole states of 16C using the 13C(12C, 9C)16C reaction and found 14 previously unknown states. Using the 12C(12C, 9C)15C reaction, five new states were observed for 15C. 相似文献
914.
S. Szegedi P. Raics M. Fayez-Hassan 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):429-433
Considering the importance of the X-ray production cross sections for the determination of the element concentrations in a
given material, we have measured them experimentally for Al Si, Sc, Ti, V, Fe, Co, Ni and Cu bombarded by protons with energies
ranging from 40 to 180 keV.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
915.
H. Vinsova R. Konirova M. Koudelkova V. Jedinakova-Krizova 《Journal of Radioanalytical and Nuclear Chemistry》2004,261(2):407-413
The uptake of technetium on bentonite materials has been studied from the point of view of the characterization of long-term radioactive elements behavior in nuclear waste repository. It is generally known that bentonite materials show an excellent cation-exchange capacity and on the other hand a poor uptake of anions. The aim of our research has been to find out the conditions suitable for technetium sorption on selected bentonite under oxidizing conditions. The influence of the addition of different materials (e.g., activated carbon, graphite, Fe2+, Fe) with bentonite, the effect of solid:aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K
d values were tested.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
916.
Lipschitz regularity for solutions to nonsmooth problems in the calculus of variations is considered, where we allow for extended-real-valued Lagrangians. Conditions for regularity are given in terms of subdifferentiability properties of the value function. In particular, it is shown that there exists a Lipschitz minimizer as long as the limiting subgradient of the value function is nonempty at the point in question. The results improve upon previous results in the literature, even in the case of finite Lagrangians. 相似文献
917.
We study nonlinear dynamics of optical pulse propagation in the spectral region inside the polariton gap. It is shown that the Kerr nonlinearity can lead to formation of solitary waves in this region of frequencies. 相似文献
918.
I.A. Khotina L.S. Lepnev N.S. Burenkova P.M. Valetsky A.G. Vitukhnovsky 《Journal of luminescence》2004,110(4):232-238
New materials based on low-generation polyphenylene dendrimers with the light emission in the blue spectrum range were synthesized and examined for an efficient organic light emitting diodes (OLED) application. It has been shown that the ratio of p-phenylene groups with high fluorescence parameters to 1,3,5-triphenylbenzene groups with low fluorescent parameters may be the possible reason for the experimental variations of relative quantum yield of photoluminescence in the compounds explored. The quantum yield value is increased with a number of dendrimer generations up to 50–70%. The role of bromine atoms as the luminescence quenchers have been demonstrated, which is important for synthesis route choice. 相似文献
919.
V. A. Nadtochenko A. S. Lobach F. E. Gostev O. M. Sarkisov D. O. Shcherbinin E. D. Obraztsova 《JETP Letters》2004,80(3):176-180
The dynamics of the photoinduced differential absorption and excited-state bleaching spectra of single-walled carbon nanotubes suspended in a micellar solution were studied in the spectral range from 40 to 1000 nm within a time interval from 70 fs to 150 ps under excitation by 50-fs pulses with photon energies 2 and 4 eV. The bleaching and absorption bands were observed in the spectra; the positions of the bleaching peaks were independent of the photon energy of the exciting femtosecond pulse in the range 2–4 eV. It was established that, for delay times shorter than 1 ps, the shape of the differential spectrum of excited nanotubes coincided with the shape of the second derivative of the absorption spectrum of unexcited nanotubes in the frequency range of exciting pulse above 18000 cm?1 (the range of absorption bands of metallic nanotubes). In the frequency range below 16000 cm?1 (the range of absorption peaks of semiconducting nanotubes), the bleaching peaks in the differential spectrum of excited nanotubes undergo a high-frequency shift of 200–300 cm?1 with respect to the second-derivative spectrum of unexcited nanotubes. The excited-state relaxation rate constants were measured. They are well approximated by the exponential dependences and depend on the probe-pulse wavelength. An assumption was made about the nature of the observed spectra of excited nanotubes and about the excitation relaxation. 相似文献
920.
N. A. Lockerbie 《General Relativity and Gravitation》2004,36(3):593-600
By using a novel free-flying, rotating, optical bench aboard the International Space Station (ISS) as the basis for a measurement of differential acceleration between two gravitating bodies, in principle the Newtonian inverse-square law and the constant of gravitation, G, can be determined at the parts in 106 level. 相似文献