全文获取类型
收费全文 | 89475篇 |
免费 | 11521篇 |
国内免费 | 4126篇 |
专业分类
化学 | 72464篇 |
晶体学 | 1109篇 |
力学 | 1947篇 |
综合类 | 115篇 |
数学 | 20390篇 |
物理学 | 9097篇 |
出版年
2024年 | 53篇 |
2023年 | 468篇 |
2022年 | 445篇 |
2021年 | 625篇 |
2020年 | 1274篇 |
2019年 | 3141篇 |
2018年 | 3008篇 |
2017年 | 3200篇 |
2016年 | 3730篇 |
2015年 | 5901篇 |
2014年 | 6023篇 |
2013年 | 8682篇 |
2012年 | 6588篇 |
2011年 | 7065篇 |
2010年 | 5788篇 |
2009年 | 5961篇 |
2008年 | 6450篇 |
2007年 | 5582篇 |
2006年 | 4911篇 |
2005年 | 4358篇 |
2004年 | 3690篇 |
2003年 | 3331篇 |
2002年 | 3932篇 |
2001年 | 2158篇 |
2000年 | 1972篇 |
1999年 | 1284篇 |
1998年 | 607篇 |
1997年 | 459篇 |
1996年 | 526篇 |
1995年 | 538篇 |
1994年 | 466篇 |
1993年 | 354篇 |
1992年 | 332篇 |
1991年 | 236篇 |
1990年 | 205篇 |
1989年 | 209篇 |
1988年 | 160篇 |
1987年 | 141篇 |
1986年 | 126篇 |
1985年 | 180篇 |
1984年 | 145篇 |
1983年 | 75篇 |
1982年 | 143篇 |
1981年 | 128篇 |
1980年 | 79篇 |
1979年 | 72篇 |
1978年 | 61篇 |
1977年 | 62篇 |
1976年 | 60篇 |
1974年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Ching Sum Hui Lillian Sze Man Lam Chun Yin Wai Kin Chan Aleksandra B. Djurii 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1708-1715
Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003 相似文献
72.
In mononuclear HgI2[(C5H4N)3N], mercury is tetrahedrally coordinated by two nitrogen atoms of a tris(2‐pyridyl)amine ligand and two iodides. The coordination moieties are connected by weak intermolecular Hg(II)···I interactions to give a one‐dimensional structure. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
73.
Peter Clifford 《Annals of Combinatorics》2005,9(3):281-291
Motivated by recent results of Stanley, we generalize the rank of a partition λ to the rank of a shifted partition S(λ). We show that the number of bars required in a minimal bar tableau of S(λ) is max(o, e + (ℓ(λ) mod 2)), where o and e are the number of odd and even rows of λ. As a consequence we show that the irreducible projective characters of Sn vanish on certain conjugacy classes. Another corollary is a lower bound on the degree of the terms in the expansion of Schur’s
Qλ symmetric functions in terms of the power sum symmetric functions.
Received November 20, 2003 相似文献
74.
《Magnetic resonance in chemistry : MRC》2003,41(1):37-41
The oxidation of symmetrical disulfides [D ,L ‐cystine ( 1 ) and 3,3′‐dithiobis(propionic acid) ( 2 )] with hydrogen peroxide in D2O–NaOH solution (pH 10–11) was studied by NMR spectroscopy. Assignments of the proton and carbon NMR signals of starting materials ( 1 and 2 ) and products of oxidation are based on conventional 1D NMR methods (DEPT, selective spin decoupling). Formation of C—S bond cleavage products or, in case of 2 , partially oxidized intermediates was not detected. The accelerating effect of Cu2+ cations, but not Fe3+ cations, on the oxidation rate of 1 in basic medium was demonstrated. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
75.
Extending to r > 1 a formula of the authors, we compute the expected reflection distance of a product of t random reflections in the complex reflection group G(r, 1, n). The result relies on an explicit decomposition of the reflection distance function into irreducible G(r, 1, n)-characters and on the eigenvalues of certain adjacency matrices.Received December 8, 2003 相似文献
76.
A method for fabricating well-dispersed nanowire suspension has been demonstrated in the paper. Thin gold nanowires were prepared by template synthesis, and then functionalized with sulphonate group-terminated thiols before suspended in different solvents. The degree of aggregation of the obtained suspension was evaluated with transmission electron microscopy (TEM) and UV-vis spectroscopy. It was found that the degree of aggregation was predominated by the solvents, and the best degree of dispersion was obtained when isopropyl alcohol (IPA) was used as the solvent. The gold nanowires from the suspension can be selectively assembled onto chemically patterned substrates. This well-dispersed nanowire suspension is potentially useful for fabricating novel nanodevices. 相似文献
77.
78.
B. Saha S. Bhattacharyya T. K. Mukherjee P. K. Mukherjee 《International journal of quantum chemistry》2003,92(5):413-418
In the framework of nonrelativistic variational formalism a new type of basis set is proposed, to estimate separately the effect of radial and angular correlations on the ground‐state energy for helium isoelectronic sequence H? to Ar16+. Effect of radial correlation is incorporated by using multiexponential functions arising from product basis sets suitably formed out of Slater‐type one‐particle orbitals. The angular correlation can be switched on by incorporating an expansion in terms of basis involving interparticle coordinates. With a set of six‐term Slater‐type one‐particle basis and five‐term interparticle expansion, the ground‐state energy of helium is estimated as ?2.9037236 (a.u.) compared with the multiterm variational estimates ?2.9037244 (a.u.) due to Pekeris and Thakkar and Smith and Drake. Matrix elements of different operators in the ground state have been calculated and found to be in good agreement with available accurate results. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献
79.
80.
B.V. Raghavaiah 《Journal of Physics and Chemistry of Solids》2004,65(6):1153-1164
PbO-Sb2O3 glasses added with different concentrations of As2O3 (10-55 mol%) were prepared to understand their IR spectra, elastic properties (Young's modulus E, Shear modulus G, microhardness H), optical absorption and dielectric properties (constant ε, loss tan δ, ac conductivity σac over a moderately wide range of frequency and temperature and breakdown strength in air medium at room temperature). Results have indicated that the structure of the PbO-Sb2O3-As2O3 glass is more rigid when the concentration of As2O3 is around 40 mol%. 相似文献