全文获取类型
收费全文 | 409172篇 |
免费 | 3365篇 |
国内免费 | 1385篇 |
专业分类
化学 | 214601篇 |
晶体学 | 6545篇 |
力学 | 17885篇 |
综合类 | 7篇 |
数学 | 46774篇 |
物理学 | 128110篇 |
出版年
2020年 | 3418篇 |
2019年 | 3912篇 |
2018年 | 5282篇 |
2017年 | 5146篇 |
2016年 | 7342篇 |
2015年 | 4382篇 |
2014年 | 7122篇 |
2013年 | 17817篇 |
2012年 | 13163篇 |
2011年 | 16222篇 |
2010年 | 11574篇 |
2009年 | 11461篇 |
2008年 | 15247篇 |
2007年 | 15337篇 |
2006年 | 14393篇 |
2005年 | 13046篇 |
2004年 | 11849篇 |
2003年 | 10638篇 |
2002年 | 10539篇 |
2001年 | 11646篇 |
2000年 | 9063篇 |
1999年 | 6982篇 |
1998年 | 5982篇 |
1997年 | 5938篇 |
1996年 | 5598篇 |
1995年 | 4877篇 |
1994年 | 4932篇 |
1993年 | 4977篇 |
1992年 | 5268篇 |
1991年 | 5465篇 |
1990年 | 5156篇 |
1989年 | 5134篇 |
1988年 | 5081篇 |
1987年 | 4949篇 |
1986年 | 4691篇 |
1985年 | 6327篇 |
1984年 | 6615篇 |
1983年 | 5331篇 |
1982年 | 5757篇 |
1981年 | 5590篇 |
1980年 | 5295篇 |
1979年 | 5575篇 |
1978年 | 5762篇 |
1977年 | 5724篇 |
1976年 | 5780篇 |
1975年 | 5331篇 |
1974年 | 5382篇 |
1973年 | 5485篇 |
1972年 | 3819篇 |
1971年 | 3276篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
V. P. Ershov D. A. Kas’yanov V. I. Rodchenkov D. A. Sergeev 《Crystallography Reports》2008,53(2):339-343
The growth of the isolated (100) face of a KDP crystal at exposure of the phase boundary to the initial ultrasound field and a standing acoustic wave has been investigated. A significant growth response of this face, exposed to sound normally along the acoustic axis in the near zone of a piston-like half-wave vibrator with f = 20 kHz and tangentially in the pulsed two-frequency (f = 600 and 900 kHz) standing-wave mode, has been revealed. It is shown that the mechanisms of mass exchange enhancement in these acoustic modes are different. The results obtained show a fundamental possibility of controlling crystal growth and dissolution by varying the parameters of inhomogeneous acoustic field. 相似文献
43.
A. P. Voronov G. N. Babenko V. M. Puzikov A. D. Roshal’ V. I. Salo 《Crystallography Reports》2008,53(4):708-712
The features of doping of KDP crystals with cerium ions and organocerium complexes with alizarin complexon and arsenazo III have been investigated. It is established that “direct” doping by introducing cerium salts into the initial solution cannot be implemented. The effect of organometallic complexes of cerium on the crystal growth has been studied. Organocerium complexes predominantly enter the prismatic or pyramidal growth sectors. It is shown that the complex arsenazo III + Ce blocks the growth of the prismatic sector. Cerium-doped KDP crystals exhibit a photoluminescence band peaking at the wavelength λmax= 350 nm. 相似文献
44.
K. Morigaki K. Takeda H. Hikita C. Ogihara P. Roca i Cabarrocas 《Journal of Non》2008,354(19-25):2131-2134
Our model for light-induced defect creation in hydrogenated amorphous silicon is applied to its kinetics, i.e., the growing curve of light-induced dangling bond density as a function of illumination time, which is fitted to a stretched exponential function. Two parameters β and τ involved in the function are estimated as functions of saturated dangling bond density in terms of our model. These are compared with two experimental results, i.e., our results obtained from ESR measurements and Shimakawa et al.’s results obtained from photoconductivity measurements. The saturated dangling bond density is also measured as a function of the generation rate of free carriers. The experimental results are compared with calculated results and discussed. 相似文献
45.
A. V. Ivanov M. Yu. Tsentalovich E. G. Kogan L. G. Tomilova N. S. Zefirov 《Russian Chemical Bulletin》2008,57(8):1676-1679
The chlorination of benzene, toluene, and o-xylene with molecular chlorine in the presence of the phthalocyanine complexes of different structures was studied. The transformations
of the catalysts during the reaction were investigated.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1644–1647, August, 2008. 相似文献
46.
The kinetics of unhindered sedimentation of a titanium dioxide suspension (as model dispersed system) was studied, and the effect of the concentration and mode of addition of various formulations based on anionic and cationic acrylamide copolymers on their flocculation properties in aqueous salt (NaCl) solutions was evaluated. 相似文献
47.
48.
S. A. Bulgakova A. I. Mashin I. A. Kazantseva D. E. Kashtanov M. M. Jones G. S. Tsepkov A. V. Korobkov A. V. Nezhdanov 《Russian Journal of Applied Chemistry》2008,81(8):1446-1451
Polymer films with a dispersed liquid crystal were prepared by photopolymerization of (meth)acrylic monomers. The electrooptical properties of these films were studied. The influence exerted by the composition of the monomer mixture, cross-linking agents, and chain-transfer agent on the liquid crystal drop size and on the transmission of the polymer-liquid crystal films was examined. 相似文献
49.
The dynamic structure factors (DSFs) of several strong glasses (SF6, SF10, BK7, SUPRASIL) measured by Brillouin light scattering spectroscopy are reported. Spectra have been collected, at and above room temperature, at two scattering angles, θ=90° and θ=180° corresponding to exchanged wavevector q values ranging from 0.0256 to 0.0448 nm−1. In particular we find that the isotropic spectral lineshapes are in all cases well described by the simple hydrodynamic theory of an amorphous solid. The width of the Brillouin peaks are found to be consistent with the predicted q2 dependence at both investigated temperatures. This damping is however found to account only partially for the strong asymmetry of the Brillouin line clearly visible on a logarithmic intensity scale. As a matter of fact there is an excess intensity in the very low frequency plateau underlying the central component. The height of this plateau and hence the entire lineshape is well reproduced if a relaxation process is taken into account in the hydrodynamic equations. Owing to the intense elastic scattering we are able to determine unambiguously only the ratio between amplitude and characteristic time of this process which quantifies the sound dispersion to be of the order of a few percent in all samples. The temperature dependence of the parameters indicates that this relaxation cannot be attributed to thermally activated relaxation phenomena. These general findings favorably compare with molecular dynamics simulation results on similar systems. 相似文献
50.
Electrohydrodynamic instability in homeotropically oriented nematic samples of 4'-n-octyl-4-cyano-biphenyl and 4'n-alkyloxy-4-cyanobiphenyl, (n = 8.9) have been studied in an a.c. electric field. The domain patterns during the instability in these compounds in a very low frequency a.c. field are very similar to those in a d.c. field. The domain patterns observed at higher frequencies have been identified as 'maltese crosses' or 'crossed isogyres'. The electro-convective 'isotropic' flows near the electrode play an important role in the observed instability. 相似文献