全文获取类型
收费全文 | 3635篇 |
免费 | 291篇 |
国内免费 | 676篇 |
专业分类
化学 | 3205篇 |
晶体学 | 72篇 |
力学 | 102篇 |
综合类 | 43篇 |
数学 | 381篇 |
物理学 | 799篇 |
出版年
2024年 | 7篇 |
2023年 | 37篇 |
2022年 | 91篇 |
2021年 | 109篇 |
2020年 | 101篇 |
2019年 | 111篇 |
2018年 | 93篇 |
2017年 | 128篇 |
2016年 | 156篇 |
2015年 | 116篇 |
2014年 | 151篇 |
2013年 | 337篇 |
2012年 | 230篇 |
2011年 | 177篇 |
2010年 | 155篇 |
2009年 | 177篇 |
2008年 | 203篇 |
2007年 | 219篇 |
2006年 | 187篇 |
2005年 | 185篇 |
2004年 | 174篇 |
2003年 | 175篇 |
2002年 | 158篇 |
2001年 | 125篇 |
2000年 | 129篇 |
1999年 | 120篇 |
1998年 | 105篇 |
1997年 | 79篇 |
1996年 | 88篇 |
1995年 | 60篇 |
1994年 | 73篇 |
1993年 | 62篇 |
1992年 | 58篇 |
1991年 | 42篇 |
1990年 | 21篇 |
1989年 | 38篇 |
1988年 | 23篇 |
1987年 | 21篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有4602条查询结果,搜索用时 31 毫秒
161.
Different physical chemical methods were used to study the thermochemical processes in a system involving a natural phosphate and complex acid salts of ammonium sulphate. The products of decomposition of the double ammonium salt and the products of their interactions with the phosphate were identified. The formation of ammonium and calcium polyphosphates and the disproportionation of P3O 10 5? and P2O 7 4? to PO 4 3? and PO 3 ? were found to depend on the circumstances of the thermal interactions. 相似文献
162.
Dr. Valentin Radtke Niklas Gebel Denis Priester Andreas Ermantraut Monika Bäuerle Dr. Daniel Himmel Regina Stroh Prof. Thorsten Koslowski Prof. Ivo Leito Prof. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(40):e202200509
Utilizing the “ideal” ionic liquid salt bridge to measure Gibbs energies of transfer of silver ions between the solvents water, acetonitrile, propylene carbonate and dimethylformamide results in a consistent data set with a precision of 0.6 kJ mol−1 over 87 measurements in 10 half-cells. This forms the basis for a coherent experimental thermodynamic framework of ion solvation chemistry. In addition, we define the solvent independent - and the values that account for the electronating potential of any redox system similar to the value of a medium that accounts for its protonating potential. This scale is thermodynamically well-defined enabling a straightforward comparison of the redox potentials (reducities) of all media with respect to the aqueous redox potential scale, hence unifying all conventional solvents′ redox potential scales. Thus, using the Gibbs energy of transfer of the silver ion published herein, one can convert and unify all hitherto published redox potentials measured, for example, against ferrocene, to the scale. 相似文献
163.
This paper concerns the application of excess adsorption isotherms, measured for solvent mixture/adsorbent systems, to the characterization of TLC data. For this purpose the excess adsorption isotherms for three liquid mixtures: cyclohexane/ benzene, benzene/acetone, and carbon tetrachloride/ethyl acetate on silica gel at 20°C have been measured. These mixtures have been used as binary mobile phases in TLC measurements. It has been shown for a given solute in binary mobile phase that the quantity RM is a simple function of the excess adsorption. Parameters of this function have been used to characterize chromatographic systems with binary mobile phases. 相似文献
164.
165.
166.
Maria Cyfert Barbara Latko Maria Wronska 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):619-626
The influence of NaClO4, NaCl and Na2SO4 on the oxidation of Fe(phen)
3
2+
by Ce(IV) was investigated by means of the stopped-flow method. At the concentrations range of NaClO4 and NaCl 0.1–1.0M the rate constant values decrease from 1.03·105 to 0.56·105M–1s–1 and from 1.08·105 to 0.81·105M–1s–1 respectively.In varying concentrations of Na2SO4 solutions (0.05–0.35M) the rate constant values decrease from 1.05·105M–1s–1 to 0.45·105M–1s–1.Taking into account the negative salt effect the mechanism of the reaction progress is proposed. 相似文献
167.
Yuan Yang Jinnan Zhang Surong Luo Xiaohong Song Qi Li 《Frontiers of Chemistry in China》2007,2(3):296-302
Two new inclusion compounds (n-C4H9)4N+C18-H13O4
−·B(OH)3 (1) and (n-C4H9)4N+C18H13O4
− (2) were prepared and characterized by X-ray crystallography. Crystal data: compound 1, monoclinic P2(1)/c, a = 1.569 9(1) nm, b = 0.995 5(6) nm, c = 2.293 3(1) nm, β = 109.962(3)°, Z = 4, and R
1 = 0.0434, wR = 0.075 9; compound 2, monoclinic C2/c, a = 1.400 5(3) nm, b = 1,282 1(2) nm, c = 1.765 7(3) nm, β = 100.388(1)°, Z = 4, and R
1 = 0.0584, wR = 0.096 6. In the crystal structure of 1, the tetramers formed by two trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (EADA) anions and two boric acid molecules were connected through
O—H⋯O hydrogen bonds to generate a channel type host lattice. The tetra-n-butylammonium cations were stacked to give two columns within each channel with cross-sectional size of about 2.30 nm × 0.93
nm. In the crystal structure of 2, similar honeycomb host lattices with big size were also formed along the [101] direction
by three-dimensional accumulation of EADA anions. The tetra-n-butylammonium cations were accommodated in a zigzag fashion within each channel.
Translated from Acta Chimica Sinica, 2006, 64(18): 1904–1910 [译自: 化学学报] 相似文献
168.
固定有四硫富瓦烯.四氰基奎诺二甲烷的杂聚吡咯膜微葡萄糖电极 总被引:1,自引:0,他引:1
铂比互铂化处理后,形成疏松,粗糙的表面,将四硫富瓦烯-四氰基奎诺二甲烷导电有机盐入到铂化的铂黑微粒中。将3-羰基丁酸吡咯与吡咯按适当的比例在其表面用电化学聚合方法,将葡萄糖氧化酶固定于聚合形成的杂聚膜中制成微酶电极。该微酶电极测定时几乎不受氧分压影响,灵敏度高,响应快。 相似文献
169.
The dependent relation between temperature and pressure of supercritical CO2+ ethanol binary system under the pressure range from 5 to 10 MPa with the variety of densities and mole fractions of ethanol
that range from 0 to 2% was investigated by the static visual method in a constant volume. The critical temperature and pressure
were experimentally determined simultaneously. The PTρ figures at different ethanol contents were described based on the determined pressure and temperature data, from which pressure
of supercritical CO2 + ethanol binary system was found to increase linearly with the increasing temperature. P-T lines show certain convergent feature in a specific concentration of ethanol and the convergent points shift to the region
of higher temperature and pressure with the increasing ethanol compositions. Furthermore, the effect of density and ethanol
concentration on the critical point of CO2 + ethanol binary system was discussed in details. Critical points increase linearly with the increasing mole fraction of
ethanol in specific density and critical points change at different densities. The critical compressibility factors Zc of supercritical CO2 + ethanol binary systems at different compositions of ethanol were calculated and Z
c
-ρ figure was obtained accordingly. It was found from Z
c
-ρ figure that critical compressibility factors of supercritical CO2 unitary or binary systems decline linearly with the increasing density, by which the critical point can be predicted precisely. 相似文献
170.
Densities and sound velocities of binary mixtures of cyclohexanone, 2-butanone, 1,4-dioxane and 1,2-dimethoxyethane were measured
at 298.15 K and also the densities at 303.15 K. Excess volumes were determined from densities. Isentropic compressibilities
were determined from densities and sound velocities, and excess thermal expansion factors were determined from excess volumes
of two temperatures. Excess isothermal compressibilities and excess isochoric heat capacities were then estimated using excess
isobaric heat capacities previously reported. Excess volumes and excess isentropic and isothermal compressibilities were negative
except for cyclohexanone+1,4-dioxane system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献