全文获取类型
收费全文 | 388篇 |
免费 | 4篇 |
专业分类
化学 | 318篇 |
晶体学 | 9篇 |
力学 | 7篇 |
数学 | 22篇 |
物理学 | 36篇 |
出版年
2023年 | 1篇 |
2022年 | 17篇 |
2021年 | 30篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 10篇 |
2013年 | 25篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 18篇 |
2009年 | 18篇 |
2008年 | 25篇 |
2007年 | 22篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 17篇 |
2001年 | 16篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有392条查询结果,搜索用时 593 毫秒
131.
Schlesinger PH Ferdani R Liu J Pajewska J Pajewski R Saito M Shabany H Gokel GW 《Journal of the American Chemical Society》2002,124(9):1848-1849
The design, synthesis, and characterization of a synthetic chloride membrane transporter, SCMTR (synthetic chloride membrane transporter, "scimitar"), are presented. The compound [CH3(CH2)17]2NCOCH2OCH2CO-GGGPGGG-OBzl inserts rapidly into liposomes and planar lipid bilayers. SCMTR has a 1.3 +/- 0.01 nS chloride diffusion pathway (>10:1 Cl/K selectivity). Evidence was also obtained for voltage gating behavior. 相似文献
132.
Mark J. Tobin Ljiljana Puskar Jafar Hasan Hayden K. Webb Carol J. Hirschmugl Michael J. Nasse Gediminas Gervinskas Saulius Juodkazis Gregory S. Watson Jolanta A. Watson Russell J. Crawford Elena P. Ivanova 《Journal of synchrotron radiation》2013,20(3):482-489
The wings of some insects, such as cicadae, have been reported to possess a number of interesting and unusual qualities such as superhydrophobicity, anisotropic wetting and antibacterial properties. Here, the chemical composition of the wings of the Clanger cicada (Psaltoda claripennis) were characterized using infrared (IR) microspectroscopy. In addition, the data generated from two separate synchrotron IR facilities, the Australian Synchrotron Infrared Microspectroscopy beamline (AS‐IRM) and the Synchrotron Radiation Center (SRC), University of Wisconsin‐Madison, IRENI beamline, were analysed and compared. Characteristic peaks in the IR spectra of the wings were assigned primarily to aliphatic hydrocarbon and amide functionalities, which were considered to be an indication of the presence of waxy and proteinaceous components, respectively, in good agreement with the literature. Chemical distribution maps showed that, while the protein component was homogeneously distributed, a significant degree of heterogeneity was observed in the distribution of the waxy component, which may contribute to the self‐cleaning and aerodynamic properties of the cicada wing. When comparing the data generated from the two beamlines, it was determined that the SRC IRENI beamline was capable of producing higher‐spatial‐resolution distribution images in a shorter time than was achievable at the AS‐IRM beamline, but that spectral noise levels per pixel were considerably lower on the AS‐IRM beamline, resulting in more favourable data where the detection of weak absorbances is required. The data generated by the two complementary synchrotron IR methods on the chemical composition of cicada wings will be immensely useful in understanding their unusual properties with a view to reproducing their characteristics in, for example, industry applications. 相似文献
133.
Magorzata Szczesio Andrzej Olczak Jolanta Goka Katarzyna Gobis Henryk Foks Marek L. Gwka 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(7):o235-o240
Methyl 2‐(pyrazin‐2‐ylcarbonyl)hydrazinecarbodithioate, C7H8N4OS2, (E1), N′‐[bis(methylsulfanyl)methylidene]pyrazine‐2‐carbohydrazide, C8H10N4OS2, (F1), N′‐[bis(methylsulfanyl)methylidene]‐6‐methoxypyrazine‐2‐carbohydrazide, C9H12N4O2S2, (F2), and methyl 1‐methyl‐2‐(pyrazin‐2‐ylcarbonyl)hydrazinecarbodithioate, C8H10N4OS2, (G1), can be considered as derivatives of classical (thio)amide‐type tuberculostatics, and all are moderately active against Mycobacterium tuberculosis. This study was undertaken in a search for relationships between activity and specific intramolecular interactions, especially conjugations and hydrogen‐bond contacts, and the molecular structures were compared with respective amine analogues, also active against the pathogen. Despite the differences between the amine and carbonyl groups with opposite functions in the hydrogen bond, the two types of structure show a surprisingly similar planar geometry, mostly due to the conjugations aided by the bifurcated intramolecular hydrogen‐bond contact between the N—H group of the central hydrazide group as donor and a pyrazine N atom and an S atom of the dithio function as acceptors. Planarity was suggested to be crucial for the tuberculostatic activity of these compounds. The N‐methylated derivative (G1) showed a significant twist at the N—N bond [torsion angle = −121.9 (3)°] due to the methyl substitution, which precludes an intramolecular N—H...S contact and the planarity of the whole molecule. Nonetheless, the compound shows moderate tuberculostatic activity. 相似文献
134.
Jolanta Kochana Katarzyna Hnida Grzegorz Sulka Paweł Knihnicki Joanna Kozak Agnieszka Gilowska 《Chemical Papers》2015,69(8):1130-1135
Polypyrrole nanowires (PPyNWs) were fabricated and examined as a structural component of amperometric biosensor matrix. An enzyme, tyrosinase (TYR), was immobilized onto PPyNWs using glutaraldehyde (GA). Matrix composite morphology was investigated using scanning electron microscopy. Electrochemical behavior of the prepared PPyNWs/GA/TYR biosensor towards catechol was studied and the assessment of its analytical characteristics was carried out taking into account linear range, sensitivity, repeatability, reproducibility and operational stability. 相似文献
135.
Ślęzak Andrzej Ślęzak-Prochazka Izabella Grzegorczyn Sławomir Jasik-Ślęzak Jolanta 《Transport in Porous Media》2017,116(2):941-957
Transport in Porous Media - S-entropy source of membrane system was described based on linear non-equilibrium thermodynamics. The volume and diffusive fluxes of non-electrolyte solutions and... 相似文献
136.
The Ramanujan Journal - It is known that among Siegel modular forms of degree 2 and level 1 the only functions that violate the Ramanujan conjecture are Saito–Kurokawa lifts of modular forms... 相似文献
137.
In this paper, the derivation of macroscopic transport equations for this cases of simultaneous heat and water, chemical and water or electrical and water fluxes in porous media is presented. Based on themicro-macro passage using the method of homogenization of periodic structures, it is shown that the resulting macroscopic equations reveal zero-valued cross-coupling effects for the case of heat and water transport as well as chemical and water transport. In the case of electrical and water transport, a nonsymmetrical coupling was found.Notations
b
mobility
-
c
concentration of a chemical
-
D
rate of deformation tensor
-
D
molecular diffusion coefficient
-
D
ij
eff
macroscopic (or effective) diffusion tensor
-
electric field
-
E
0
initial electric field
-
k
ij
molecular tensor
-
j, j
*,
current densities
-
K
ij
macroscopic permeability tensor
-
l
characteristic length of the ERV or the periodic cell
-
L
characteristic macroscopic length
-
L
ijkl
coupled flows coefficients
-
n
i
unit outward vector normal to
-
p
pressure
-
q
t
,q
t
+
,
heat fluxes
-
q
c
,q
c
+
,
chemical fluxes
-
s
specific entropy or the entropy density
-
S
entropy per unit volume
-
t
time variable
-
t
ij
local tensor
-
T
absolute temperature
-
v
i
velocity
-
V
0
initial electric potential
-
V
electric potential
-
x
macroscopic (or slow) space variable
-
y
microscopic (or fast) space variable
-
i
local vectorial field
-
i
local vectorial field
-
electric charge density on the solid surface
-
,
bulk and shear viscosities of the fluid
-
ij
local tensor
-
ij
local tensor
-
i
local vector
-
ij
molecular conductivity tensor
-
ij
eff
effective conductivity tensor
-
homogenization parameter
-
fluid density
-
0
ion-conductivity of fluid
-
ij
dielectric tensor
-
i
1
,
i
2
,
i
3
local vectors
- 4
local scalar
-
S
solid volume in the periodic cell
-
L
volume of pores in the periodic cell
-
boundary between
S
and
L
-
s
rate of entropy production per unit volume
-
total volume of the periodic cell
-
l
volume of pores in the cell
On leave from the Politechnika Gdanska; ul. Majakowskiego 11/12, 80-952, Gdask, Poland. 相似文献
138.
The difference between natural and regenerated cellulose fibers caused by variations in the degree of polymerization and supramolecular structure, influences dyes adsorption properties. The aim of the study was to discriminate between cotton and viscose fibers, dyed with several dye classes, using Raman spectroscopy. 8 reactive and 6 direct dyes were used for colouring textiles under laboratory conditions. Spectra of fibers were obtained with the use of three excitation sources: 514, 633, and 785 nm. The obtained results allowed for the differentiation of studied types of cellulose fibers, dyed with the same dye, at the same or very similar concentrations. 相似文献
139.
Jolanta Cieśla Andrzej Bieganowski Jolanta Narkiewicz-Michałek Marta Szymula 《Journal of Dispersion Science and Technology》2013,34(4):566-574
The interpretation of micelle/aggregate size obtained by use of the DLS technique for SDS/water/pentanol systems was discussed by comparison of the results of measurement with theoretical data. For most of the studied systems, the apparent radii (R h,app ) did not satisfactorily characterize the size of the aggregates (R h,app < 1 nm). The use of a correction factor (f = 0.26) confirmed that the discrepancies were associated with the electrostatic intermicellar interactions. However, the fuzzy optical interface between dispersed and dispersing phases can also be the reason of such results. An increase of pentanol content caused a decrease of the droplet radius in w/o systems but in o/w systems the changes were negligible. 相似文献
140.
Jolanta Szczygelska-Tao Marina S. Fonari Jan F. Biernat 《Supramolecular chemistry》2013,25(7):651-658
Azocrown ethers with sulphur atoms and pyrrole or imidazole residue as a part of macrocycle have been synthesised. Their metal complexation abilities in acetonitrile were studied using UV–vis spectrophotometry. The largest spectral changes were observed for both pyrrole- and imidazole-azothiacrown ethers on complexation with Pb2 + , Cu2 + , Zn2 + , Ni2 + , Co2 + and Ag+ ions. In the case of alkali and alkaline earth metal ions no spectral changes were found. Preliminary studies of ion-selective membrane electrodes with synthesised ionophores are presented. In the measurement for transition/heavy metal cations, only copper and lead give high responses. X-ray structure of 18-membered pyrrole azothiacrown ether is described. 相似文献