全文获取类型
收费全文 | 356篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
化学 | 239篇 |
晶体学 | 3篇 |
力学 | 6篇 |
数学 | 68篇 |
物理学 | 55篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 9篇 |
2013年 | 20篇 |
2012年 | 25篇 |
2011年 | 26篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 23篇 |
2007年 | 20篇 |
2006年 | 11篇 |
2005年 | 15篇 |
2004年 | 20篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1964年 | 1篇 |
1941年 | 2篇 |
1933年 | 1篇 |
1932年 | 3篇 |
1931年 | 2篇 |
1926年 | 1篇 |
1918年 | 1篇 |
1917年 | 1篇 |
1912年 | 2篇 |
1911年 | 2篇 |
1901年 | 3篇 |
1900年 | 3篇 |
1898年 | 2篇 |
1897年 | 1篇 |
1884年 | 1篇 |
排序方式: 共有371条查询结果,搜索用时 31 毫秒
51.
52.
V. Henriques L. de Jager S. P. L. Sörensen H. Jessen-Hansen H. Malfatti O. v. Spindler H. Björn-Andersen Marius Laritzen T. Yoshida W. Frey und A. Gigon 《Fresenius' Journal of Analytical Chemistry》1911,50(8):528-534
Ohne ZusammenfassungVergl. auch diese Zeitschrift47, 547;49, 66. 相似文献
53.
Variability of UV irradiance in Europe 总被引:1,自引:1,他引:0
Seckmeyer G Pissulla D Glandorf M Henriques D Johnsen B Webb A Siani AM Bais A Kjeldstad B Brogniez C Lenoble J Gardiner B Kirsch P Koskela T Kaurola J Uhlmann B Slaper H den Outer P Janouch M Werle P Gröbner J Mayer B de la Casiniere A Simic S Carvalho F 《Photochemistry and photobiology》2008,84(1):172-179
54.
Martins MA Santos C Almeida MM Costa ME 《Journal of colloid and interface science》2008,318(2):210-216
Hydroxyapatite (HAP) particles with different morphologies were precipitated from homogeneous calcium/citrate/phosphate solutions at physiological temperature. Small variations of the starting solution pH in the range 7.4相似文献
55.
Pissarra LS Farinha CM Xu Z Schmidt A Thibodeau PH Cai Z Thomas PJ Sheppard DN Amaral MD 《Chemistry & biology》2008,15(1):62-69
Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) Cl(-) channel. F508del, the most frequent CF-causing mutation, disrupts both the processing and function of CFTR. Recently, the crystal structure of the first nucleotide-binding domain of CFTR bearing F508del (F508del-NBD1) was elucidated. Although F508del-NBD1 shows only minor conformational changes relative to that of wild-type NBD1, additional mutations (F494N/Q637R or F429S/F494N/Q637R) were required for domain solubility and crystallization. Here we show that these solubilizing mutations in cis with F508del partially rescue the trafficking defect of full-length F508del-CFTR and attenuate its gating defect. We interpret these data to suggest that the solubilizing mutations utilized to facilitate F508del-NBD1 production also assist folding of full-length F508del-CFTR protein. Thus, the available crystal structure of F508del-NBD1 might correspond to a partially corrected conformation of this domain. 相似文献
56.
Carabineiro SA Bellabarba RM Gomes PT Pascu SI Veiros LF Freire C Pereira LC Henriques RT Oliveira MC Warren JE 《Inorganic chemistry》2008,47(19):8896-8911
The new bis-iminopyrrolyl five-coordinate Co(II) complexes [Co(kappa (2) N, N'-NC 4H 3C(R)N-2,6- (i)Pr 2C 6H 3) 2(PMe 3)] (R = H 3a; Me 3b) were synthesized in high yields (ca. 80-90%), using THF and diethyl ether as solvents, respectively, by (a) treatment of CoCl 2(PMe 3) 2 with the corresponding iminopyrrolyl Na salts ( Ie or If) or (b) reaction of anhydrous CoCl 2 and PMe 3 with Ie or If. A third route was tested, involving the addition of excesses of PMe 3 to the complexes [Co(kappa (2) N, N'-NC 4H 3C(R)N-2,6- (i)Pr 2C 6H 3) 2] (R = H 1e; Me 1f), which was only successful for the synthesis of 3a, in lower yields (ca. 30%). The synthesis of 3b in THF was unfruitful because of the kinetic competition of the solvent, giving rise to mixtures of 1f and its coordinated THF adduct 4b. The synthesis of the new bis-iminopyrrolyl five-coordinate Co(II) complexes [Co(kappa (2) N, N'-NC 4H 3C(R)N-2,6- (i)Pr 2C 6H 3) 2(THF)] (R = H 4a; Me 4b) were carried out in high yields (ca. 80-90%) by the reaction of CoCl 2(THF) 1.5 with the corresponding iminopyrrolyl Na salt. All the compounds have been characterized by X-ray diffraction, with 3a and 3b showing axially compressed trigonal bipyramidal geometry (with the PMe 3 ligand lying on the equatorial plane), whereas complexes 4a and 4b exhibit distorted square pyramidal geometries with the THF molecule occupying the axial position. Complex 4a shows clearly a compressed geometry, but for complex 4b, two polymorphs were characterized, exhibiting molecules with different Co-O (THF) bond lengths, one of them being compatible with an elongated form. Magnetic measurements either in the solid or in the liquid phases indicate that complexes 3a and 3b have low-spin ground states ( S = 1/2). In toluene solution, the geometry is fully confirmed by EPR data, which further indicates a d x (2) - y (2) /d xy ground state. However, compounds 4a and 4b behave unusually because they show magnetic moments that are compatible with high-spin ground states ( S = 3/2) in the solid state, but conform to low-spin ground states ( S = 1/2) when both complexes are dissolved in toluene solutions. The low-spin ground states in toluene solution are confirmed by EPR spectroscopy, which further supports, for complexes 4a and 4b, an axially elongated square pyramidal geometry and a d z (2) ground state. Thus the change in the ground-state and, consequently, in the geometry of complexes 4a and 4b from solid state to toluene solution might be a consequence of the elongation of the Co-O(THF) bond length. DFT studies performed on complexes 3 and 4 corroborate their different structure and magnetic behaviors and verify, for the latter complexes, the structural differences observed in the solid state and in toluene solution. 相似文献
57.
José Gaspar Mihail Fontul Elsa Henriques António Ribeiro Arlindo Silva Nuno Valverde 《Applied Acoustics》2016
The car interior is becoming quieter and other sounds are now exposed to user perception, such as the sound produced by interface buttons when actuated. So, the functional role of the button sound on interface operation and its aesthetic and emotional role on the user experience are now more important than before. However, little research and design effort has been paid to understand how to design buttons that produce a pleasant sound. Moreover, the button’s sound requirements received by interface manufacturers are ill-defined, insufficient or even inexistent, and consequently their conversion into specifications for manufacturing is problematic and leads to long and costly development processes. The purpose of this paper is to contribute to identify relevant acoustic parameters that explain the users sound preferences. Data on preference subjective judgments were collected and buttons acoustic signals were measured allowing the development of preference models based on partial least squares regression and neural networks methods. The former was successful in selecting the relevant parameters to describe the preference ratings of the buttons sound. The later, dealing with the non-linear nature of acoustic perception, was able to predict preferences based on the relevant parameters. 相似文献
58.
Duarte Darío J. R. Miranda Margarida S. Esteves da Silva Joaquim C. G. Liebman Joel F. 《Structural chemistry》2016,27(2):663-670
Structural Chemistry - In this paper, we investigate the nature of the carbonyl and the intraring C–C, C–N, C–O, N–N, O–O and N–O bonds of cyclopropanone and the... 相似文献
59.
Nunes JP Figueira MJ Belo D Santos IC Ribeiro B Lopes EB Henriques RT Vidal-Gancedo J Veciana J Rovira C Almeida M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(35):9841-9849
The gold and nickel bisdithiolene complexes based on new highly extended ligands incorporating fused tetrathiafulvalene and thiophene moieties (alpha-tdt=thiophenetetrathiafulvalenedithiolate and dtdt=dihydro- thiophenetetrathiafulvalenedithiolate), were prepared and characterised by using cyclic voltammetry, single crystal X-ray diffraction, EPR, magnetic susceptibility and electrical transport measurements. These complexes, initially obtained under anaerobic conditions as diamagnetic gold monoanic [nBu(4)N][Au(alpha-tdt)(2)] (4), [nBu(4)N][Au(dtdt)(2)] (3) and nickel dianionic species [(nBu(4)N)(2)][Ni(alpha-tdt)(2)] (8), [(nBu(4)N)(2)][Ni(dtdt)(2)] (7), can be easily oxidised to the stable neutral state just by air or iodine exposure. The monoanionic complexes crystallise in at least two polymorphs, all of which have good cation and anion segregation in alternated layers, the anion layers making a dense 2D network of short SS contacts. All of the neutral complexes, obtained as microcrystalline or quasi amorphous fine powder, present relatively large magnetic susceptibilities that correspond to effective magnetic moments in the range 1-3 mu(B) indicative of high spin states and very high electrical conductivity that in case of the Ni compound can reach sigma(RT) approximately 250 S cm(-1) with a clear metallic behaviour. These compounds are new examples of the still rare single-component molecular metals. 相似文献
60.
Margarida Mendes Lopes Rita Pardini 《Proceedings of the American Mathematical Society》2007,135(5):1279-1282
In this note it is shown that, given a smooth minimal complex surface of general type with , , for which the bicanonical map is a morphism, the degree of is not 3. This completes our earlier results, showing that if is a minimal surface of general type with , such that is free, then the bicanonical map of can have degree 1, 2 or 4.