全文获取类型
收费全文 | 112465篇 |
免费 | 11758篇 |
国内免费 | 7362篇 |
专业分类
化学 | 39856篇 |
晶体学 | 1794篇 |
力学 | 15034篇 |
综合类 | 1271篇 |
数学 | 27135篇 |
物理学 | 46495篇 |
出版年
2025年 | 375篇 |
2024年 | 1511篇 |
2023年 | 1684篇 |
2022年 | 2484篇 |
2021年 | 2834篇 |
2020年 | 3445篇 |
2019年 | 3412篇 |
2018年 | 3001篇 |
2017年 | 3166篇 |
2016年 | 3527篇 |
2015年 | 3375篇 |
2014年 | 4971篇 |
2013年 | 7443篇 |
2012年 | 6191篇 |
2011年 | 6343篇 |
2010年 | 5266篇 |
2009年 | 6677篇 |
2008年 | 6853篇 |
2007年 | 6633篇 |
2006年 | 5899篇 |
2005年 | 5035篇 |
2004年 | 4359篇 |
2003年 | 4355篇 |
2002年 | 4582篇 |
2001年 | 3525篇 |
2000年 | 3423篇 |
1999年 | 2899篇 |
1998年 | 3091篇 |
1997年 | 2127篇 |
1996年 | 1878篇 |
1995年 | 1444篇 |
1994年 | 1435篇 |
1993年 | 1123篇 |
1992年 | 1208篇 |
1991年 | 859篇 |
1990年 | 744篇 |
1989年 | 571篇 |
1988年 | 508篇 |
1987年 | 441篇 |
1986年 | 363篇 |
1985年 | 375篇 |
1984年 | 342篇 |
1983年 | 210篇 |
1982年 | 296篇 |
1981年 | 248篇 |
1980年 | 164篇 |
1979年 | 213篇 |
1978年 | 169篇 |
1977年 | 167篇 |
1976年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
《Journal of Coordination Chemistry》2012,65(19):3492-3501
Four MnIII-porphyrin complexes, chloro(tetraphenylporphinato)MnIII(1,6-diaminohexane), bromo(tetraphenylporphinato)MnIII(1,6-diaminohexane), azido(tetraphenylporphinato)MnIII(1,6-diaminohexane), and thiocyanato(tetraphenylporphinato)MnIII(1,6-diaminohexane), have been synthesized. These complexes have been characterized using UV-Vis, IR, ESI-mass spectra, elemental analyses, magnetic susceptibility measurements, and conductivity measurement. The molar conductance values of these complexes in ethanol indicate non-electrolytes. The utility of these complexes in de-polymerization of coal using humic acid as the coal model has been tested by the optical density method. 相似文献
92.
93.
Summary The problem of the electronic, ionic and atomic density profiles in a nonuniform liquid metal which can locally exist in partially
ionized states is examined using the density functional formalism. Ions and electrons are allowed to bind into atoms through
a ?reaction? governed by the mass action law. Formally exact equations for the density profiles are given in terms of the
inverse response matrix of the nonuniform system, which consists of two terms: the first corresponding to to a mixture of
ions, electrons and structureless atoms and the other to the atomic internal degrees of freedom. Approximate schemes are proposed
for both contributions, stressing, in partieular, i) how ionization of the atoms arises with increasing density and the relation
with Mott’s criterion for the metal-insulator transition, and ii) the usefulness of a weak-coupling assumption for interspecies
correlations. This formalism used together with properly parametrized trial functions for the density profiles should be particularly
useful for studying the liquid-vapour interface of alkali metals.
Riassunto Il lavoro usa il formalismo del funzionale di densità per discutere la determinazione dei profili di densità in un fluido non omogeneo che può trovarsi localmente in stati di ionizzazione parziale. Con riferimento specifico ai metalli alcalini, la formazione di atomi per legame di ioni ed electtroni è descritta come una ?reazione? governata dalla legge di azione di massa. Le condizioni di equilibrio microscopico del fluido sono espresse tramite una matrice di risposta in cui appaiono due contributi, associati rispettivamente ai gradi di libertà interni degli atomi e ad una miscela di tre specie di particelle senza struttura interna. Si propongono quindi schemi approssimati per il calcolo di questi due contributi, con attenzione particolare all’uso di teorie perturbative e alla relazione tra grado di ionizzazione locale e densità localle, in connessione col criterio di Mott per la transizione isolante-metallo. Il formalismo proposto è in particolare appropriato per lo studio dell’interfaccia liquido-vapore in metalli alcalini.
Резюме Используя функционала плотности, исследуется проблема профилей электронной, ионной и атомой ллотностей В неоднодном зидком металле, которий мозет локалщно существоватщ в частично иониэированных состояних. Ионы и электроны могут şвяэыватщся в атомщ череэ ?реакцию, определяемую эаконом дейşтвуюших масс. Приводятся формалщно точные уравнения для профнлеи плотности в термина⇆ обратной матрици отклика для неоднородной системы, которая состоит иэ двух чуленов: первий соответствует ссмеси ионов, электронов и бесстрктурных атмов и второй член соответствует атомным внутренним степеням свобды. Предлагаются приближенные схемы для обоых вкладов, обрашая особое бнмание, в частности, 1) как иониэация атомов воэликает бри увеличени влотности, на свяэы с критерием Мота для берехода ?металл-иеолятор?, и 2) на полеэносты предположения слабой свяэи для межвидовых кореляций. Предложенный Формалиэм, исполыеовалный вместе с параметриэованными пробными функциями для профилей плотнорти, окаэываетця оробенне полеэным для исследования грраницы ?жидкостъ-пар? в шелочлых металлах.相似文献
94.
Quantum Ising models in a transverse field are related to continuous-time percolation processes whose oriented percolation versions are contact processes. We study such models in the presence of quasiperiodic disorder and prove localization in the ground state, no percolation, and extinction, respectively, for sufficiently large disorder. 相似文献
95.
The collisional broadening and shift of four spectral lines of neon (747.2, 748.8, 753.5, 754.4 nm) arising from 2p5 3p - 2p5 3d transitions, emitted from a low-pressure glow discharge in pure neon and neon-helium mixtures have been measured using a Fabry-Perot interferometer. The values of pressure broadening and shift coefficients are determined and analyzed in terms of the impact theory. 相似文献
96.
稀土对小麦(Triticum aestivum)体内光合和呼吸速率及磷酸化功能的影响 总被引:1,自引:0,他引:1
沈博礼 《新疆大学学报(理工版)》1995,12(2):92-95
以适当浓度稀土溶液处理小麦后,其光合和氧化磷酸化的磷氧比(P/O)、光合控制(Pc)、呼吸控制(RC)、状态3.4光合和呼吸速率(S3.S4)与对照样比均无显著性差异。状态2(S2)光合和呼吸速率提高,差异极显著。说明小麦用最适浓度稀土处理后,对其光合和呼吸的磷酸化机构和功能膜影响不大,但显著促进了光合和呼吸速率(S2),从而促进了电子传递链的活性,使ATP形成量增加。 相似文献
97.
98.
99.
A. Alsaad A. Ahmad 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):151-156
First-principles calculations are performed to compute the e33
piezoelectric coefficients of GaN, ScN and (ScxGa1-xN) alloys
exhibiting an alternation of hexagonal GaN, with hexagonal ScN along the c-axis. For Sc compositions larger than 50%, each atom has nearly five nearest
neighbors (i.e., the ground state exhibits a phase that is five-fold
coordinated). On the other hand, Sc-deficient (Sc, Ga) N alloys adopt a
ground-state that is four-fold coordinated). The magnitude of e33 in
the Sc-deficient ideally ordered (Sc0.25Ga0.75N) is found to be larger
than the magnitude of the corresponding e33 coefficients resulting from
the compositional weighted average over the hexagonal (h-ScN) and the wurtzite (w-GaN) parent compounds. On the other hand, the e33 coefficients of the Sc-rich
ordered (Sc0.75Ga0.25N) is found to be negligibly small. In addition, e33
piezoelectric coefficients in ordered (Sc0.5Ga0.5N) exhibit quite
large magnitudes, due to the nonpolar to polar transition occurs at Sc composition x = 0.5, and thus can bridge the corresponding coefficients of (Ga, In) N and
ferroelectric alloys. The microscopic origins for this huge enhancement in
the piezoelectric behavior in Sc-low and Sc-intermediate alloys and the role
of each atom are revealed and discussed. 相似文献
100.
ZONG Hong-Shi SUN Wei-Min 《理论物理通讯》2006,46(11)
By differentiating the inverse dressed quark propagator at finite chemical potential μ with respect to μ, the linear response of the dressed quark propagator to the chemical potential can be obtained. From this we extract a modelindependent formula for the linear chemical potential dependence of the in-medium two-quark condensate and show by two independent methods (explicit calculation and Lorentz covariance arguments) that the first-order contribution in μto the in-medium two-quark condensate vanishes identically. Therefore if one wants to study the in-medium two-quark condensate one should expand to at least the second order in the chemical potential μ. 相似文献