全文获取类型
收费全文 | 3238篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
化学 | 1215篇 |
晶体学 | 47篇 |
力学 | 98篇 |
数学 | 324篇 |
物理学 | 1570篇 |
出版年
2022年 | 27篇 |
2021年 | 58篇 |
2020年 | 61篇 |
2019年 | 66篇 |
2018年 | 106篇 |
2017年 | 86篇 |
2016年 | 117篇 |
2015年 | 43篇 |
2014年 | 82篇 |
2013年 | 140篇 |
2012年 | 106篇 |
2011年 | 111篇 |
2010年 | 128篇 |
2009年 | 103篇 |
2008年 | 151篇 |
2007年 | 150篇 |
2006年 | 122篇 |
2005年 | 124篇 |
2004年 | 98篇 |
2003年 | 99篇 |
2002年 | 82篇 |
2001年 | 96篇 |
2000年 | 76篇 |
1999年 | 44篇 |
1998年 | 39篇 |
1997年 | 46篇 |
1996年 | 41篇 |
1994年 | 24篇 |
1993年 | 38篇 |
1992年 | 37篇 |
1991年 | 42篇 |
1990年 | 34篇 |
1989年 | 37篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1985年 | 30篇 |
1984年 | 31篇 |
1983年 | 27篇 |
1982年 | 25篇 |
1981年 | 28篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1977年 | 43篇 |
1976年 | 34篇 |
1975年 | 28篇 |
1974年 | 29篇 |
1973年 | 34篇 |
1972年 | 29篇 |
1971年 | 28篇 |
1970年 | 22篇 |
排序方式: 共有3254条查询结果,搜索用时 734 毫秒
101.
For the five-coordinated complexes of ferroprotoporphynynn with imidazole, a quantum-chemical analysis of the electronic structure and Mossbauer spectral parameters has been canied out. Peripheral substituents (CH3, Cf13, C2H4COOH) were introduced into the porphynin macrocycle to model the real chemical structure of protopo'phynynn in the heme group of desoxyhemoglobin. The calculations have shown that near the occupation border in the complaes there are MO which are due to the -systems of the CH= CM2 and CH2CH2COOH substituents. The orientalion of the vinyl fragments has a considerable effect on the populations of the Fe d-orbitals and the quadrupole splitting EQ for the5B1 and5B2 terns.Institute of Biophysics, Ministry of Health, Russian Federation. Translated fromZhurnal Strukturmoi Khimii, Vol. 34, No. 5, pp. 90–93, September–October, 1993.Translated by L. Smolina 相似文献
102.
K. L. Rogozhin A. N. Rodionov S. G. Smirnov D. N. Shigorin O. P. Syutkina V. I. Lodochnikova K. A. Kocheshkov 《Russian Chemical Bulletin》1976,25(2):319-322
1. | There is a regular increase in the energy of the lowest singlet and triplet excited levels in the aromatic derivatives of the elements C, Si, Ge, Sn and N, P, As, Sb, Bi, which is consistent with the quantum-mechanical model of the mixing of the electronic states of the aromatic system with states involving p and s orbitals of the heteroatom with different energies and symmetries. |
2. | The yields of the radiative electronic transitions regularly decrease, and the probabilities of nonradiative intramolecular electronic transitions increase. |
3. | The temperature effects inthe 300–77°K range in the electronic absorption spectra have been found and are associated with a postulated change in the spatial configuration of the compounds investigated. |
103.
Smirnov N. B. Burmakin E. I. Shekhtman G. Sh. 《Russian Journal of Electrochemistry》2001,37(3):326-329
Transport numbers for potassium and rubidium cations in solid electrolytes (K1 – x
Rb
x
)3.8M0.1P2O7(M = Ca, Cd, Ba) are measured, and the co-cation nature of the electrolytes" conduction is confirmed. The concentration dependences of transport numbers are used to draw a conclusion about the ratio between mobilities of potassium and rubidium cations. The presence of an extremum in the concentration dependence of the activation energy for the rubidium-cation constituent of conduction is confirmed by the NMR method. The obtained results are explained by assuming that the polyalkaline effect is largely due to an ordering of mobile alkali cations. 相似文献
104.
Chelsea N. Widener Alexandria N. Bone Mykhaylo Ozerov Rachael Richardson 路正光 Komalavalli Thirunavukkuarasu Dmitry Smirnov 陈学太 薛子陵 《无机化学学报》2020,36(6):1149-1156
最近Ruamps和同事发现三角双锥构型的Ni(Ⅱ)配合物[Ni(Me6tren)Cl]ClO4(1,Me6tren=tris(2-(dimethylamino)ethyl)amine)具有大的单轴磁各向异性(J.Am.Chem.Soc.,2013,135:3017-3026)。他们利用HF-EPR研究获得横向零场分裂(ZFS)参数E=1.56(5)cm-1但未能确定轴向零场分裂参数D。在本工作中,我们利用0~17.5 T和5 K的变磁场远红外光谱(FIRMS)来检测自旋基态S=1中的MS=±1和MS=0态之间的磁跃迁。在FIRMS中直接观察到Zeeman分裂态之间的跃迁,得出轴向ZFS参数D=-110.7(3)cm-1。我们对1的晶体结构进行了Hirshfeld表面分析,揭示了1分子中的阳离子与阴离子之间以及分子之间的相互作用。 相似文献
105.
MENG Jian REN Yu-Fang LI Xiao-GuangLaboratory of Rare Earth Chemistry Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin ChinaPopov V.V. Repin S.M. Smirnov LA. loffe Physicotechnical Institute Russian Academy of Sciences Saint Petersburg Russia 《中国化学》1994,12(5):419-424
YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected as an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)-O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of YBa2Cu3-xVxO7-v and also results in a depression of TC. 相似文献
106.
Yu. V. Kuznetsov L. G. Stolyarova V. P. Lezina L. D. Smirnov 《Russian Chemical Bulletin》1989,38(7):1494-1500
1. | New halogen derivatives of 1-ethyl-2-methyl-, 2-methyl- and 5-hydroxybenzimidazole were obtained. |
2. | A method for the chlorination of aromatic compounds by an alcoholic solution of hydrogen chloride in the presence of hydrogen peroxide was proposed, which enables carrying out the reaction with a high yield. |
3. | The reactivity of the series of 5(6)-hydroxybenzimidazole derivatives during the electrophilic substitution (halogenation) was shown to be as follows: 1-ethyl-2-methyl-5-hydroxybenzimidazole >5(6)-hydroxybenzimidazole 2-methyl-5-hydroxybenzimidazole. |
107.
G. Sh. Shekhtman E. I. Burmakin N. B. Smirnov N. O. Esina 《Russian Journal of Electrochemistry》2002,38(5):549-553
In the sodium-orthophosphate-based solid solutions in Na3 – 2x
M
x
PO4 systems (M = Cd, Pb), the electroconduction is maximum near the upper concentration boundaries of the single-phase regions: x 0.4 for M = Cd and x 0.25 for M = Pb. The conductivity values at 300°C are 6.25 × 10–3 and 2.5 × 10–3 S/cm, respectively. The conduction of synthesized solid electrolytes has a co-cation nature. Their electric characteristics, inferior to those of the Na3PO4-based solid solutions obtained via heterovalent substitutions of another type, may be a manifestation of an effect similar to the polyalkali effect. 相似文献
108.
L. I. Vereshchagin A. V. Petrov A. G. Proidakov F. A. Pokatilov A. I. Smirnov V. N. Kizhnyaev 《Russian Journal of Organic Chemistry》2006,42(6):912-917
Polynuclear nonfused blocks containing 1,2,3-triazole, 1,3,4-oxadiazole, and tetrazole rings were synthesized by reaction of C-substituted tetrazoles with carboxylic acid chlorides, as well as by cycloaddition of 2-azidomethyl-1,3,4-oxadiazoles at the triple bond of acetylenic compounds. 相似文献
109.
A. P. Kilimov M. A. Svechnikova V. I. Shevchenko V. V. Smirnov S. B. Zotov F. V. Kvasnyuk-Mudryi 《Chemistry of Heterocyclic Compounds》1969,5(2):156-159
The IR spectra of six monosubstituted and of four 2,6-disubstituted 1,4-dioxanes have been studied in the 650–1800cm–1 region. The assignment of the bands due to the vibrations of the 1,4-dioxane ring and to the deformation vibrations of the methylene groups of the ring is given. The appearance of a whole series of new absorption bands on passing from unsubstituted 1,4-dioxane to its derivatives is explained by the change in the symmetry of the molecule and the removal of the prohibition from the vibrations previously inactive in the IR spectra connected with this reduction in symmetry. It is proposed to use, in order to confirm the presence of a 1,4-dioxane ring in a molecule from the results of IR spectroscopy, not only the 1126-cm–1 band but the whole group of bands lying in the frequency ranges 800–950, 1000–1150, and 1200–1300 cm–1.For part I, see [3]. 相似文献
110.
The regions of variation of density, enthalpy of formation, and detonation velocity of all of the formally possible structual isomers were determined for several molecular formulas of C,H,N,O-containing explosives. The histograms of the distribution of the structual isomers over these parameters were constructed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 859–862, May, 1995.The authors are grateful to Mrs. I. D. Solodukhina for the design of the graphical material.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 94-03-09323). 相似文献