全文获取类型
收费全文 | 5323篇 |
免费 | 126篇 |
国内免费 | 24篇 |
专业分类
化学 | 3851篇 |
晶体学 | 28篇 |
力学 | 112篇 |
数学 | 539篇 |
物理学 | 943篇 |
出版年
2022年 | 45篇 |
2021年 | 50篇 |
2020年 | 65篇 |
2019年 | 62篇 |
2018年 | 49篇 |
2017年 | 45篇 |
2016年 | 94篇 |
2015年 | 76篇 |
2014年 | 88篇 |
2013年 | 217篇 |
2012年 | 280篇 |
2011年 | 332篇 |
2010年 | 187篇 |
2009年 | 147篇 |
2008年 | 304篇 |
2007年 | 295篇 |
2006年 | 287篇 |
2005年 | 296篇 |
2004年 | 282篇 |
2003年 | 207篇 |
2002年 | 236篇 |
2001年 | 102篇 |
2000年 | 109篇 |
1999年 | 66篇 |
1998年 | 72篇 |
1997年 | 50篇 |
1996年 | 94篇 |
1995年 | 51篇 |
1994年 | 69篇 |
1993年 | 90篇 |
1992年 | 74篇 |
1991年 | 50篇 |
1990年 | 46篇 |
1989年 | 53篇 |
1988年 | 37篇 |
1987年 | 43篇 |
1986年 | 36篇 |
1985年 | 60篇 |
1984年 | 42篇 |
1983年 | 32篇 |
1982年 | 66篇 |
1981年 | 39篇 |
1980年 | 56篇 |
1979年 | 39篇 |
1978年 | 52篇 |
1977年 | 46篇 |
1976年 | 43篇 |
1975年 | 53篇 |
1974年 | 33篇 |
1973年 | 41篇 |
排序方式: 共有5473条查询结果,搜索用时 15 毫秒
881.
D. S. Pratt Ch. R. Sanger E. R. Riege A. Stoc E. Schwinge P. Rassfeld E. Havas G. K. Burgess H. Siedentopf W. Biltz J. Shukow W. Kurbatow Holborn Wien R. Loebe W. Dickmann R. Wegscheider Tammann W. Plato Ruffs W. P. White R. Nacken Ernst Jänecke John Johnston L. H. Adams 《Analytical and bioanalytical chemistry》1918,57(3):138-144
882.
H. v. Wartenberg B. Lerner-Steinberg J. Geidel W. Rehwinkel T. Gaydo A. Perrier P. E. Verkade J. Coops Jr. E. Cohen S. Miyake J. A. van der Hoeve C. Moureu W. P. White F. Karas A. Mennucci W. Sturm E. Berner J. Peters J. W. Davis E. L. Wallace W. Kohen S. H. Regester G. B. Watkins J. V. Hunn C. A. Myers Jr. W. Groose W. Dinkler A. Herberholz J. S. G. Thomas M. Barash H. Löffler 《Analytical and bioanalytical chemistry》1930,82(11-12):455-456
883.
Synthesis of an advanced intermediate for (+)-pillaromycinone. Staunton-Weinreb annulation revisited
Condensation of an orsellinate anion with a 2-cyclohexenone (Staunton-Weinreb annulation) afforded a linear tetracycle which was converted to a protected derivative of 12a-epipillaromycinone. Methodology for introducing a 12a-hydroxyl substituent into the tetracycle with correct (R) configuration is described. 相似文献
884.
Graham Smith Urs D. Wermuth Jonathan M. White 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(9):o532-o536
The crystal structures of the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with the three isomeric monoaminobenzoic acids, namely the hydrate 2‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate dihydrate, C7H8NO2+·C8H3Cl2O4−·2H2O, (I), and the anhydrous salts 3‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate, C7H8NO2+·C8H3Cl2O4−, (II), and 4‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate, C7H8NO2+·C8H3Cl2O4−, (III), have been determined at 130 K. Compound (I) has a two‐dimensional hydrogen‐bonded sheet structure, while (II) and (III) are three‐dimensional. All three compounds feature sheet substructures formed through anilinium N+—H...Ocarboxyl and anion carboxylic acid O—H...Ocarboxyl interactions and, in the case of (I), additionally linked through the donor and acceptor associations of the solvent water molecules. However, (II) and (III) have additional lateral extensions of these substructures though cyclic R22(8) associations involving the carboxylic acid groups of the cations. Also, (II) and (III) have cation–anion π–π aromatic ring interactions. This work provides further examples illustrating the regular formation of network substructures in the 1:1 proton‐transfer salts of 4,5‐dichlorophthalic acid with the bifunctional aromatic amines. 相似文献
885.
Sather-Wagstaff Sean; Sharif Tirdad; White Diana 《Journal London Mathematical Society》2008,77(2):481-502
We show that an iteration of the procedure used to define theGorenstein projective modules over a commutative ring R yieldsexactly the Gorenstein projective modules. Specifically, givenan exact sequence of Gorenstein projective R-modules
such that the complexes HomR(G, H) and HomR(H,G) are exact for each Gorenstein projective R-module H, themodule Coker() is Gorensteinprojective. The proof of this result hinges upon our analysisof Gorenstein subcategories of abelian categories. 相似文献
886.
E. Rodney Canfield Catherine Greenhill Brendan D. McKay 《Journal of Combinatorial Theory, Series A》2008,115(1):32-66
Let s=(s1,s2,…,sm) and t=(t1,t2,…,tn) be vectors of non-negative integers with . Let B(s,t) be the number of m×n matrices over {0,1} with jth row sum equal to sj for 1?j?m and kth column sum equal to tk for 1?k?n. Equivalently, B(s,t) is the number of bipartite graphs with m vertices in one part with degrees given by s, and n vertices in the other part with degrees given by t. Most research on the asymptotics of B(s,t) has focused on the sparse case, where the best result is that of Greenhill, McKay and Wang (2006). In the case of dense matrices, the only precise result is for the case of equal row sums and equal column sums (Canfield and McKay, 2005). This paper extends the analytic methods used by the latter paper to the case where the row and column sums can vary within certain limits. Interestingly, the result can be expressed by the same formula which holds in the sparse case. 相似文献
887.
Rio-Echevarria IM White FJ Brechin EK Tasker PA Harris SG 《Chemical communications (Cambridge, England)》2008,(38):4570-4572
Benzohydroxamic acid is shown to be an unexpectedly good ligand for iron(iii) oxides, favouring surface attachment to the formation of trisbenzohydroxamato complexes, which are known to have very high thermodynamic stability in solution. 相似文献
888.
889.
890.