全文获取类型
收费全文 | 741篇 |
免费 | 27篇 |
国内免费 | 3篇 |
专业分类
化学 | 372篇 |
晶体学 | 23篇 |
力学 | 25篇 |
数学 | 69篇 |
物理学 | 282篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 10篇 |
2016年 | 24篇 |
2015年 | 25篇 |
2014年 | 24篇 |
2013年 | 67篇 |
2012年 | 51篇 |
2011年 | 48篇 |
2010年 | 39篇 |
2009年 | 37篇 |
2008年 | 48篇 |
2007年 | 36篇 |
2006年 | 33篇 |
2005年 | 37篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1984年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1937年 | 2篇 |
1930年 | 10篇 |
1929年 | 4篇 |
1906年 | 2篇 |
排序方式: 共有771条查询结果,搜索用时 15 毫秒
731.
The sorption capacities of hydrous SiO2 and ZrO2 for the Zn(ammine) ion have been observed to increase on irradiation with γ-rays, by ca. 4.1 and 3.8%, respectively. The
rates of sorption increase differently in the irradiated exchangers, depending upon their characteristic natures; e. g. when
the external concentration of the Zn(ammine) solution is 0.2M, the increase in the F value due to irradiation is more striking
in the case of SiO2 than for ZrO2. On the other hand, at a lower external concentration of the Zn(ammine) solution (0.01M), the increase in the F value, particularly
during the first five minutes, is more significant for ZrO2. 相似文献
732.
J. M. Chatterjee Somapriya Basu R. K. Chattopadhyay K. Kar D. Banik R. P. Sharma S. K. Pardhasaradhi 《Zeitschrift für Physik A Hadrons and Nuclei》1992,344(2):149-154
An investigation of the high spin isomer in151Sm was performed via the150Nd(α, 3nγ) reaction at a projectile energy of 35 MeV. A newγ-transition, 693.6 keV was identified having an exponential delayed component. The transition feeds the 1912 keV state of the negative parity band built on theh 11/2 state. This transition was also observed in coincidence withγ-rays belonging to151Sm in theγ-γ coincidence experiment atE α =37 MeV. A new isomeric state having energyE x =2605.8 keV and half lifeT 1/2=23.1±3.5 ns is proposed. 相似文献
733.
The series of CH...O bonds formed between CF(n)H(4-n) (n = 0-3) and water are studied by quantum calculations under vacuum and in various solvents, including aqueous environment. The results are compared with the OH...O bond of the water dimer in the same solvents. Increasing polarity of the solvent leads in all cases to a lessening of the H-bond interaction energy, in a uniform fashion such that the CH...O bonds all remain weaker than OH...O in any solvent. These H-bond weakenings are coupled to a shortening of the inter-subunit separation. The contraction of the covalent CH bond to the bridging proton is reduced as the solvent becomes more polar, and the blue shift of its stretching vibration is likewise diminished. A process is considered that simulates protein folding by starting from a pair of noninteracting subunits in aqueous solvent and then goes to a H-bonded pair within the confines of a protein environment. This process is found to be energetically more favorable for some of the CH...O H-bonds than for the nominally stronger conventional OH...O H-bond. This finding suggests that CH...O bonds can make important energetic contributions to protein folding, on par with those made by traditional H-bonds. 相似文献
734.
Dislocation structure of coarse-plate perlite in carbon steel after cold and high-temperature strain
V. M. Schastlivtsev I. L. Yakovleva L. E. Kar’kina Yu. V. Khlebnikov T. I. Tabatchikova V. N. Urtsev 《Russian Physics Journal》2004,47(8):807-817
It is demonstrated that during cold plastic deformation of coarse-plate perlite in carbon steel, planar cementite defects play the key role in deformation transfer through interphase boundaries and promote dissolution of cementite plates. It is first established that the austenite substructure formed upon high-temperature deformation is inherited by cementite and ferrite components of perlite during the subsequent phase transformation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 18–27, August, 2004. 相似文献
735.
Conjugate reduction of alkynones by stoichiometric [(Ph(3)P)CuH](6) or catalytic [(Ph(3)P)CuH](6) and polymethyl-hydrosiloxane proceeds to cyclization by an aldol reaction with tethered ketones to generate [small beta]-hydroxyenones with good diastereoselectivity. 相似文献
736.
Coal is the most important nonrenewable energy source of fossil origin. It is also the most common fuel in thermal power plants.
However, during coal incineration in power plants, high sulfur content of coal poses serious environmental problems owing
to sulfur dioxide emission. We studied the application of microbial methods for removal of sulfur from three types of high
sulfur coals—two samples collected from Assam and Rajasthan in India and one from Libiaz, Poland. These coal samples were
desulfurized using indigenous Acidithiobacillus sp. After investigation of the effect of various parameters, the conditions optimized for the maximum removal of total sulfur
(91.87% for lignite, 63.13% for Polish coal, and only 9.44% for Assam coal) were as follows: initial pH of 1.5 (2.5 in the
case of Assam coal), particle size of 45 μ, pulp density of 2% (w/v), incubation period of 30 d at −35°C in presence of 44.2
g/L of ferrous sulfate in the media with shaking at 140 rpm. Poor removal of sulfur in the case of Assam coal was owing to
extensive precipitation of jarosites. In addition, the sulfur in Assam coal is mostly found in organic form, which is difficult
to remove with Acidithiobacillus sp. The removal of sulfur from the three coal samples was demonstrated with photomicrographic studies. 相似文献
737.
We grow single and twofold stacked island layers on patterned substrates and investigate the material distribution in and around the patterned area. For both layers a pronounced material depletion region occurs outside the pattern. The material gradients across the planar-patterned interface are symmetric in the first, but highly asymmetric in the second layer. We can describe these phenomena by simulations that take into account the surface curvature for the first and a strain-field modulated surface for the second layer. 相似文献
738.
Borghesi M Bulanov SV Esirkepov TZh Fritzler S Kar S Liseikina TV Malka V Pegoraro F Romagnani L Rousseau JP Schiavi A Willi O Zayats AV 《Physical review letters》2005,94(19):195003
Experimental investigations of the late-time ion structures formed in the wake of an ultrashort, intense laser pulse propagating in a tenuous plasma have been performed using the proton imaging technique. The pattern found in the wake of the laser pulse shows unexpectedly regular modulations inside a long, finite width channel. On the basis of extensive particle in cell simulations of the plasma evolution in the wake of the pulse, we interpret this pattern as due to ion modulations developed during a two-stream instability excited by the return electric current generated by the wakefield. 相似文献
739.
In this article we attempt to bring out some significant general aspects of what we call collapse-induced quantum nonlocal
effects resulting from the use of the hypothesis of wave function collapse. 相似文献
740.
Electron mobility in compensated semiconductors for ionised impurity scattering is calculated. A simple screened dipole potential is used. The calculations differ from those of Stratton due to the fact that in this paper the mobility is exactly calculated. 相似文献