全文获取类型
收费全文 | 2172篇 |
免费 | 285篇 |
国内免费 | 269篇 |
专业分类
化学 | 957篇 |
晶体学 | 35篇 |
力学 | 288篇 |
综合类 | 2篇 |
数学 | 420篇 |
物理学 | 1024篇 |
出版年
2024年 | 1篇 |
2023年 | 40篇 |
2022年 | 112篇 |
2021年 | 113篇 |
2020年 | 128篇 |
2019年 | 75篇 |
2018年 | 59篇 |
2017年 | 100篇 |
2016年 | 83篇 |
2015年 | 138篇 |
2014年 | 160篇 |
2013年 | 227篇 |
2012年 | 235篇 |
2011年 | 181篇 |
2010年 | 206篇 |
2009年 | 148篇 |
2008年 | 95篇 |
2007年 | 120篇 |
2006年 | 93篇 |
2005年 | 41篇 |
2004年 | 23篇 |
2003年 | 20篇 |
2002年 | 21篇 |
2001年 | 30篇 |
2000年 | 23篇 |
1999年 | 23篇 |
1998年 | 17篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 22篇 |
1987年 | 42篇 |
1986年 | 40篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 5篇 |
1957年 | 1篇 |
排序方式: 共有2726条查询结果,搜索用时 11 毫秒
1.
Y. Z. Song J. M. Xie Y. Song Y. Ye 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(10):1669-1676
The geometric parameters, vibrational frequencies, and thermochemical values of p-quinonimine (p-AQ) and p-aminophenol (p-AP) were computed ab initio (IIF) and by the density functional theory (DFT) method with the 6-31G(d, p) basis set. Cyclic voltammetry with a golden electrode of p-AP solutions in phosphate buffers at pH 7.30 showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.728 V. The standard electrode potentials of half reactions for p-QI and p-AP were calculated using the free energies and solvation energies of p-QI, p-AP, p-benzoquinone (p-BQ), and hydroquinone (p-HQ). The results showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.743 V at the B3LYP/6-31G(d, p) level and 0.755 V at the HF/6-31G(d, p) level. The standard electrode potentials computed at the B3LYP/6-31G(d, p) and HF/6-31G(d, p) levels were close to their experimental values.
The article is published in the original. 相似文献
2.
《Annals of Physics》1986,166(1):250-252
In a recent paper on the theory of subdynamics, Ch. Obcemea and E. Brändas (Ann. Phys (N.Y.)151 (1983), 383–430) claimed to correct a recently published result (M. Courbage, J. Math. Phys.23 (1982), 646, 652). It is shown that this criticism is unfounded. Some additional remarks are made. 相似文献
3.
《Solid State Communications》1986,57(8):611-613
The 87Rb NMR measurement was carried out in a single-crystal Rb0.3MoO3. Below 180 K the NMR line well characterized the existence of incommensurate CDW. The absence of lock-in transition was confirmed from the temperature dependence of line shape. The CDW held the incommensurate phase even at 77 K, in spite of the nearly commensurate value of CDW wave vector observed in the neutron diffraction experiment. The CDW amplitude obtained from NMR was consistent with the BCS curve. 相似文献
4.
《Solid State Communications》1986,57(8):643-647
The elastic constants of monoclinic KHCO3 have been determined from resonance frequencies of thick plates at ca. 15 MHz in the range between 250 and 370 K. A strong elastic anisotropy is present with a maximum of the longitudinal stiffness near the direction of the hydrogen bonds within the (HCO3)2-2 dimers. The shear stiffness c66 related to transversal waves propagating along the twofold axis [0 1 0]′ and [1 0 0]′ with displacement vectors nearly parallel to [1 0 0]′ and [0 1 0]′, respectively, shows a drastic softening approaching 318 K from below and from above, indicating a ferroelastic transition. All other elastic constants behave normally except in the close vicinity of the transition temperature where in some cases a small discontinuity is visible. The components of the thermal expansion tensor undergo a discontinuous change at the transition. The pressure derivative of the transition temperature is 2.3 K kbar-1. A comparison with alkali cyanides and KH2PO4 reveals that the interactions driving the transition are rather originating from order-disorder processes of protons as in KH2PO4 than from an orientational molecular disorder as in alkali cyanides. 相似文献
5.
《Solid State Communications》1986,57(2):89-92
Crystals of β-(BEDT-TTF)2AuI2, derived from the sulfur-based organic donor bis(ethylenedithio) tetrathiafulvalene [BEDT-TTF or “ET”] have been synthesized by electrocrystallization and studied by rf penetration depth measurements at ambient pressure and at temperatures down to 0.45 K. The crystals were found to be superconducting at ambient pressure with Tc = 3.93–4.98 K, which represent the highest values of Tc thus far observed at ambient pressure for an organic superconductor. Measurements of the upper critical field anisotropy are reported. 相似文献
6.
《Surface science》1986,177(2):L956-L962
7.
《Journal of organometallic chemistry》1986,301(2):153-160
A novel series of bicyclic organogermanium derivatives: 5-germaspiro[4.4]nona-2,7-dienes have been prepared by reaction of 1,1-dihalogermacyclopent-3-enes with the appropriate conjugated diene and an alkali metal in a suitable organic solvent. The best results were obtained by using 1,1-dichlorogermacyclopentenes with isoprene or 2,3-dimethylbutadiene and lithium in 5/1 ether/tetrahydrofuran. Except for 2,3,7,8-tetramethyl-5-germaspiro[4.4]nona-2,7-diene, which is crystalline, the 5-germaspirononadienes are colourless liquids, which distil without decomposition under reduced pressure but which slowly polymerize on standing. In the mass spectra of all the spiradienes, the main peak corresponds to the loss of one ring, the less substituted in the case of unsymmetrical molecules. Attempts to obtain 5-germaspiro[4.4]nona-2,7-diene were unsuccessful. 相似文献
8.
《Operations Research Letters》1986,5(2):73-77
A linear stochastic program where the right-hand side elements are linear transformations of independent stochastic variables is considered. We show how bounds on the recouse (second-stage) problem can be found by working directly on the independent stochastic variables instead of the right-hand side elements. 相似文献
9.
《Journal of solid state chemistry》1986,63(3):386-390
Shock-recovery experiments on Nb2O5 powder specimens are made in pressure ranges up to 50 GPa using the gun method. “NbO2” with the rutile structure is formed above about 40 GPa when an open recovery fixture is used. The tetragonal unit cell dimensions are measured to be a = 4.784(2) Å, c = 3.029(2) Å, and V = 69.34(6) Å3. The metal-to-oxygen ratio is determined to be Nb0.94O2 by means of thermogravimetry. A comparative study is made on the shock reduction behavior of Nb2O5 and Ta2O5. 相似文献
10.
《Tetrahedron》1986,42(2):739-746
Indirect, but compelling evidence for the intermediacy of dithiiranes 1 and thiosulfines 2 has been found by us and is also provided by literature data. The intriguing dithiirane → dithioester rearrangement as well as most of the interrelations and conversions postulated in Scheme 1 have been demonstrated experimentally. In a number of cases acetyl α-chloroalkyl disulfides 16 (X = Cl, Y = COCH3) are useful starting materials for the synthesis of thioamides such as 40. 相似文献