全文获取类型
收费全文 | 1673篇 |
免费 | 89篇 |
国内免费 | 7篇 |
专业分类
化学 | 1043篇 |
晶体学 | 1篇 |
力学 | 51篇 |
数学 | 364篇 |
物理学 | 310篇 |
出版年
2023年 | 14篇 |
2022年 | 9篇 |
2021年 | 20篇 |
2020年 | 29篇 |
2019年 | 23篇 |
2018年 | 35篇 |
2017年 | 24篇 |
2016年 | 78篇 |
2015年 | 64篇 |
2014年 | 67篇 |
2013年 | 138篇 |
2012年 | 127篇 |
2011年 | 113篇 |
2010年 | 82篇 |
2009年 | 57篇 |
2008年 | 77篇 |
2007年 | 85篇 |
2006年 | 79篇 |
2005年 | 64篇 |
2004年 | 59篇 |
2003年 | 54篇 |
2002年 | 53篇 |
2001年 | 34篇 |
2000年 | 25篇 |
1999年 | 13篇 |
1998年 | 19篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1934年 | 11篇 |
1911年 | 5篇 |
排序方式: 共有1769条查询结果,搜索用时 15 毫秒
111.
C. Zúñiga M. S. Larrechi G. Lligadas J. C. Ronda M. Galià V. Cádiz 《Journal of polymer science. Part A, Polymer chemistry》2011,49(5):1219-1227
The novel benzoxazine monomers, DPA‐Bz and MDP‐Bz from renewable diphenolic acid (DPA), which mimics the structure of bisphenol A (BPA), were synthesized by traditional approaches. The structure and purity of the monomers was confirmed by FTIR, 1H NMR, and 13C NMR spectra. The thermally activated polymerization of the MDP‐Bz and DPA‐Bz afforded thermosetting polybenzoxazines with higher Tg's, 270 °C and 208 °C respectively, and higher crosslinking density compared to BPA‐Bz, due to the transesterification or esterification reactions occurred during curing process. These reactions are in accordance with the number of independent reactions determined analyzing by SVD the chemical rank of the IR spectra data matrices recorded along the homopolymerization reactions monitored at 200 °C. Spectral and concentration profiles of the active chemical species involved in these processes were obtained by MCR‐ALS. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
112.
A López-Macià J C Jiménez M Royo E Giralt F Albericio 《Journal of the American Chemical Society》2001,123(46):11398-11401
Kahalalide F, the only member of the family of peptides called kahalalides, isolated from the sacoglossan mollusc Elysia rufescens and the green alga Bryopsis sp., with important bioactivity, is in clinical trials for treatment of prostate cancer. An efficient solid-phase synthetic approach is reported. Kahalalide F presents several synthetic difficulties: (i) an ester bond between two beta-branched and sterically hindered amino acids; (ii) a didehydroamino acid; and (iii) a rather hydrophobic sequence with two fragments containing several beta-branched amino acids in a row, one of them terminated with a saturated aliphatic acid. The cornerstones of our strategy were (i) a quasiorthogonal protecting system with allyl, tert-butyl, fluorenyl, and trityl-based groups, (ii) azabenzotriazole coupling reagents, (iii) formation of the didehydroamino acid residue on the solid phase, and (iv) cyclization and final purification in solution. HPLC, high-field NMR, and biological activity studies showed that the correct stereochemistry of the natural product is that proposed by Rinehart et al. whereas the stereochemistry proposed by Scheuer et al. is that of a biologically less active diastereoisomer. 相似文献
113.
Arben Merkoçi Majlinda Vasjari Esteve Fàbregas Salvador Alegret 《Mikrochimica acta》2000,135(1-2):29-33
Two different approaches for the modification of glassy carbon electrodes using a mercury film and mercury-nafion are compared.
The mixture of mercury(II) chloride solution with a nafion solution diluted in ethanol is used to coat the polished glassy
carbon surface. The modified working electrodes are compared when measuring Pb and Cu in real seawater samples. An optimisation
of the parameters during the formation of the films was done to obtain well-defined stripping peaks. The type of inert supporting
electrolyte and the pH play an important role on the sensitivity of the measurement. Results for Pb and Cu determinations
show the advantages of Hg-nafion modification as an alternative method. These advantages include a shorter modification time,
the avoidance of Hg solutions during the formation of the Hg film and an improved sensitivity for Pb determination.
Received March 16, 1999. Revision April 24, 2000. 相似文献
114.
We characterize generators ? of norm continuous quantum Markov semigroups satisfying the quantum detailed balance condition with respect to an antiunitary time reversal in terms of the operators H and L k in the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) representation ?(x) = i[H, x] ? (1/2)gZ k (L* k L k x ? 2L* k x L k + x L* k L k ). 相似文献
115.
B. Juliá-Díaz 《Few-Body Systems》2008,43(1-4):103-108
Recent developments on a dynamical coupled-channels model of hadronic and electromagnetic production of nucleon resonances are summarized. 相似文献
116.
H. Kràl 《Analytical and bioanalytical chemistry》1893,32(1):206-206
117.
The main objective of this paper is to study and describe the hypercentre of a finite group associated with saturated formations, in terms of some subgroup embedding properties related to permutability. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
118.
Annali di Matematica Pura ed Applicata (1867-1897) - 相似文献
119.
N. Pappadà 《Colloid and polymer science》1910,6(2):83-86
Ohne Zusammenfassung(Aus dem chemischen Laboratorium des Technischen Instituts in Cremona.) 相似文献
120.
Ohne Zusammenfassung(Uebersetzt von J. Donau, Graz.)(Erste Mitteilung.) 相似文献