全文获取类型
收费全文 | 4677篇 |
免费 | 164篇 |
国内免费 | 12篇 |
专业分类
化学 | 2803篇 |
晶体学 | 85篇 |
力学 | 151篇 |
数学 | 331篇 |
物理学 | 1483篇 |
出版年
2023年 | 42篇 |
2022年 | 54篇 |
2021年 | 82篇 |
2020年 | 101篇 |
2019年 | 93篇 |
2018年 | 115篇 |
2017年 | 85篇 |
2016年 | 133篇 |
2015年 | 110篇 |
2014年 | 163篇 |
2013年 | 268篇 |
2012年 | 352篇 |
2011年 | 346篇 |
2010年 | 196篇 |
2009年 | 175篇 |
2008年 | 206篇 |
2007年 | 202篇 |
2006年 | 204篇 |
2005年 | 156篇 |
2004年 | 125篇 |
2003年 | 119篇 |
2002年 | 89篇 |
2001年 | 76篇 |
2000年 | 62篇 |
1999年 | 54篇 |
1998年 | 33篇 |
1997年 | 54篇 |
1996年 | 58篇 |
1995年 | 44篇 |
1994年 | 76篇 |
1993年 | 84篇 |
1992年 | 79篇 |
1991年 | 51篇 |
1990年 | 50篇 |
1989年 | 54篇 |
1988年 | 35篇 |
1987年 | 39篇 |
1986年 | 37篇 |
1985年 | 35篇 |
1984年 | 35篇 |
1983年 | 41篇 |
1982年 | 40篇 |
1981年 | 49篇 |
1980年 | 40篇 |
1979年 | 31篇 |
1978年 | 26篇 |
1977年 | 34篇 |
1975年 | 24篇 |
1974年 | 27篇 |
1973年 | 33篇 |
排序方式: 共有4853条查询结果,搜索用时 859 毫秒
111.
The inner-shell structure of some heavy atoms is examined using a self-consistent relativistic local density method. Ar(K), Kr(K) and Xe (K,L
1,L
2 andL
3) binding energies and {ie863-1} (hyper-satellite) energies of Tl, Hg and Tm are calculated. The results are compared with
available experimental data.
A part of this work was presented byMPD at the Trieste International Symposium on “Core level excitations in atoms, molecules and solids,” 22–26 June 1981, Extended
Abstracts (ed.) E Tosatti, ICTP Report No. 89/81 p. 11. 相似文献
112.
Arylazoimidazoles (2) are N,N-chelating ligands. The polymerization trend of the azolate system is restricted via N(1)-benzylation. The parent molecules (2), N(1)-benzylated products (3) and palladium complexes (4) were made by standard methods. The ligands (3) and complexes (4) are new. They have been characterized by elemental analysis, i.r., u.v.-vis. and high resolution 1H-n.m.r. spectral data. Redox studies were carried out by cyclic voltammetry. On complexation, azo reduction is shifted anodically. 相似文献
113.
Das DD Mahapatra R Pradhan J Das SN Thakur RS 《Journal of colloid and interface science》2000,232(2):235-240
Removal of hexavalent chromium from aqueous medium by using activated cow dung carbon was studied. Cow dung was carbonized and activated by treating with concentrated H(2)SO(4) followed by heating for 24 h at 120 degrees C. The extent of adsorption was studied as a function of pH, contact time, amount of adsorbent, concentration of adsorbate, and temperature. At lower pH (<3.5), the prepared sorbent was capable of removing approximately 90% Cr(VI) at 5 ppm concentration from aqueous synthetic solution. The dynamics of migration of the sorbate ions from the bulk onto the sorbent surface was studied and the results obtained under various experimental conditions were found to follow standard adsorption isotherms. The reaction kinetics was found to be of first order. Copyright 2000 Academic Press. 相似文献
114.
B. J. T. Nieuwendijk J. R. W. Woittiez H. A. Das 《Journal of Radioanalytical and Nuclear Chemistry》1985,89(2):465-472
A correction procedure is presented for the residual bias due to dead time losses in thermal INAA based on short-lived radionuclides. It is based on a linear least-squares fitting, starting from three pre-chosen (average) half-lives. 相似文献
115.
The effect of calcination temperature on the physico-chemical characterization of manganese nodule leached residue (MNLR) and water-washed manganese nodule leached residue (WMNLR) has been investigated on the basis of chemical analysis, XRD, TG-DTA, FTIR, surface hydroxyl groups, surface oxygen, reducing and oxidizing sites, surface area. XRD and IR confirm the presence of amorphous iron oxyhydroxides, delta-MnO2, which are converted to alpha-Fe2O3 and gamma-Mn2O3 phases above 400 degrees C of calcination, respectively. A solid solution of Fe2O3 and Mn2O3 is formed above 700 degrees C. The surface area, surface hydroxyl group, surface oxygen, reducing and oxidizing sites increase with the increase in calcination temperature up to 400 degrees C and then decrease with further rise in calcination temperature up to 700 degrees C. The catalytic activity of the sample towards H2O2 decomposition shows the similar trend as surface properties. A suitable Mn(3+)Mn4+ couple favours H2O2 decomposition reaction. The activity has been correlated with various physico-chemical properties. 相似文献
116.
Precise measurements on the electrical conductivity of solutions of sodium salt of carboxymethylcellulose in acetonitrile/water mixed-solvent media containing 10, 20, and 40 vol % of acetonitrile are reported as a function of temperature. The degree of substitution of carboxymethylcellulose used was 0.70, and the concentrations were varied from approximately 1 x 10(-4) to approximately 1 x 10(-2) equiv L(-1). The results showed a decrease in the equivalent conductivity with increasing polyelectrolyte concentration. The applicability of Manning's theory for salt-free polyelectrolyte solutions was examined, and a major discrepancy against the theory was observed. The calculated values of the equivalent conductivity deduced on the basis of this theory were found to be higher than the experimental ones. Possible reasons for this discrepancy have been discussed. The fractions of uncondensed counterions were evaluated, and these were found to depend on the polyelectrolyte concentration. The effects of the temperature and relative permittivity of the medium on the equivalent conductivity as well as on the fraction of uncondensed counterions were also investigated. 相似文献
117.
The change in semiconductive properties of β-apo-8′-carotenal, astacene and methyl bixin on adsorption of various vapours
on the crystallite surfaces has been studied at a constant sample temperature. The adsorption of vapours enhances the semiconductivity
of the polyenes appreciably. This enhancement depends on the chemical nature and also on the pressure of the adsorbed vapour.
The adsorption and desorption kinetics follow the modified Roginsky-Zeldovich relation. A two stage desorption process, the
first stage of which gives a Lennard-Jones potential energy curve and is followed by a rate-determining transition over a
potential energy barrier to the second stage of adsorption forming weakly bound complexes between the vapour molecules and
the polyene crystallites, can explain satisfactorily the experimentally observed kinetic data. 相似文献
118.
Biswanath Das Kongara Damodar Darshanala Saritha Nikhil Chowdhury Martha Krishnaiah 《Tetrahedron letters》2007,48(45):7930-7933
The Sakurai reaction of N-alkoxycarbonylamino sulfones with allyltrimethylsilane in the presence of a catalytic amount of indium(III) chloride at room temperature produces the corresponding protected homoallylic amines in high yields. 相似文献
119.
120.
The Saccharomyces strains uvarum, montuliensis, bayanus, capensis and florentinus were grown in liquid media prepared from a 1% aqueous glucose solution to which 0.05% of ammonium sulfate or urea were added as the only nitrogen supply. The amino acids exuded during incubation were isolated by cation exchange and derivatized as the corresponding N,O-heptafluorobutyryl isopropyl esters. Separation was achieved on a highly deactivated glass capillary column coated with OV-101. A characteristic amino acid profile was obtained for each of the species studied, allowing the construction of a chemotaxonomic tree, on the basis of present or absent acids. 相似文献