全文获取类型
收费全文 | 453652篇 |
免费 | 3058篇 |
国内免费 | 1399篇 |
专业分类
化学 | 223753篇 |
晶体学 | 6630篇 |
力学 | 24024篇 |
综合类 | 16篇 |
数学 | 74114篇 |
物理学 | 129572篇 |
出版年
2020年 | 3497篇 |
2019年 | 4179篇 |
2018年 | 15852篇 |
2017年 | 15647篇 |
2016年 | 13672篇 |
2015年 | 5017篇 |
2014年 | 7451篇 |
2013年 | 16483篇 |
2012年 | 15911篇 |
2011年 | 24751篇 |
2010年 | 16530篇 |
2009年 | 16961篇 |
2008年 | 20478篇 |
2007年 | 22383篇 |
2006年 | 13036篇 |
2005年 | 12784篇 |
2004年 | 12067篇 |
2003年 | 11588篇 |
2002年 | 10507篇 |
2001年 | 10619篇 |
2000年 | 8315篇 |
1999年 | 6196篇 |
1998年 | 5381篇 |
1997年 | 5457篇 |
1996年 | 5109篇 |
1995年 | 4315篇 |
1994年 | 4472篇 |
1993年 | 4435篇 |
1992年 | 4811篇 |
1991年 | 4950篇 |
1990年 | 4732篇 |
1989年 | 4794篇 |
1988年 | 4656篇 |
1987年 | 4627篇 |
1986年 | 4431篇 |
1985年 | 5689篇 |
1984年 | 5863篇 |
1983年 | 4797篇 |
1982年 | 5062篇 |
1981年 | 4916篇 |
1980年 | 4538篇 |
1979年 | 5081篇 |
1978年 | 5171篇 |
1977年 | 5310篇 |
1976年 | 5326篇 |
1975年 | 4984篇 |
1974年 | 4896篇 |
1973年 | 5133篇 |
1972年 | 3683篇 |
1971年 | 3348篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
N. A. Anurova V. A. Blatov G. D. Ilyushin O. A. Blatova A. K. Ivanov-Shitz L. N. Demyanets 《Crystallography Reports》2008,53(6):930-936
A new method was developed for studying voids and channels in crystal structures based on the Voronoi-Dirichlet partition
of crystal space, and 822 structurally characterized ternary compounds Li
p
X
q
O
r
were analyzed for the first time. For these compounds, the dimensionality was determined and the migration patterns of channel
systems capable of providing lithium-ion transport were constructed. The calculated coordinates of lithium atoms in the centers
of the voids are consistent (within 0.4 ?) with the known structural data. Among these compounds, 113 compounds have infinite
channel systems, 60 compounds (18 structural types, STs) have been described earlier in the literature as solid electrolytes,
and 53 compounds (23 STs) can be considered as potential one-, two-, or three-dimensional ionic conductors (13, 3, and 7 STs,
respectively).
Original Russian Text ? N.A. Anurova, V.A. Blatov, G.D. Ilyushin, O.A. Blatova, A.K. Ivanov-Shitz, L.N. Dem’yanets, 2008,
published in Kristallografiya, 2008, Vol. 53, No. 6, pp. 987–993. 相似文献
32.
M.N. Ichchou J. Berthaut M. Collet 《International Journal of Solids and Structures》2008,45(5):1179-1195
This paper addresses the issue of energy propagation features in ribbed panels over a wide frequency range. First, a tool for estimating the wave propagation characteristics of one- and two-dimensional structures by k-space analysis is presented. This tool uses a concept of Inhomogeneous Wave Correlation with sparse measured or extracted data, and leads to the estimation of θ-dependent wavenumbers. Here, the method is employed with the sparse simulated and measured normal velocities of a set of ribbed panels and new insights into their k-space behavior are highlighted. Behavior is essentially characterized at low frequencies by structural orthotropy. Comparisons with homogenized data show very good agreement. At higher frequencies, a new behavior pattern is observed and explained both numerically and experimentally. This is a multi-modal waveguide type of propagation in a direction parallel to the ribs. 相似文献
33.
Chengzhi Qi Mingyang Wang Qihu Qian Jianjie Chen 《Moscow University Mechanics Bulletin》2008,63(5):113-121
The formation mechanisms for the structural hierarchy in geological media are discussed. It is shown that the formation of such a hierarchy is caused by certain external and internal circumstances. The first ones consist in the fact that, because of external actions, the Earth’s poles continuously execute the translational and rotational motions responsible for a regular structure of rock fracture and for the appearance of the scale factor √2. The second ones consist in the fact that, under the action of many random factors and because of external actions, during the formation of geological media there appear dissipative structures and, hence, some self-similar fractal structures are formed. 相似文献
34.
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
35.
36.
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
37.
A. Ya. Samuilov L. A. Zenitova I. N. Bakirova Ya. D. Samuilov 《Russian Journal of Applied Chemistry》2008,81(8):1419-1422
Thermodynamic parameters of reactions of methyl and phenyl isocyanates with a series of compounds were determined by quantum-chemical calculations. The products of these reactions model for various functional groups present in commercial polyurethanes. The thermodynamic stability series for compounds formed from aliphatic and aromatic isocyanates were constructed. 相似文献
38.
K. S. Trofimova V. G. Dronov N. S. Shaglaeva R. G. Sultangareev 《Russian Journal of Applied Chemistry》2008,81(4):730-731
Possibilities of utilization of by-products formed in manufacture of epichlorohydrin are considered. A promising way to utilize wastes from production of epichlorohydrin by synthesis of 2,3-dichloropropene from 1,2,3-trichloropropane is suggested. 相似文献
39.
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
40.
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