全文获取类型
收费全文 | 78102篇 |
免费 | 330篇 |
国内免费 | 374篇 |
专业分类
化学 | 24276篇 |
晶体学 | 792篇 |
力学 | 6733篇 |
数学 | 31942篇 |
物理学 | 15063篇 |
出版年
2018年 | 10435篇 |
2017年 | 10261篇 |
2016年 | 6065篇 |
2015年 | 838篇 |
2014年 | 291篇 |
2013年 | 312篇 |
2012年 | 3780篇 |
2011年 | 10492篇 |
2010年 | 5627篇 |
2009年 | 6034篇 |
2008年 | 6604篇 |
2007年 | 8752篇 |
2006年 | 232篇 |
2005年 | 1306篇 |
2004年 | 1534篇 |
2003年 | 1976篇 |
2002年 | 1013篇 |
2001年 | 247篇 |
2000年 | 291篇 |
1999年 | 153篇 |
1998年 | 192篇 |
1997年 | 146篇 |
1996年 | 200篇 |
1995年 | 122篇 |
1994年 | 80篇 |
1993年 | 98篇 |
1992年 | 58篇 |
1991年 | 62篇 |
1990年 | 52篇 |
1989年 | 59篇 |
1988年 | 60篇 |
1987年 | 61篇 |
1986年 | 58篇 |
1985年 | 52篇 |
1984年 | 48篇 |
1983年 | 38篇 |
1982年 | 46篇 |
1981年 | 42篇 |
1980年 | 51篇 |
1979年 | 46篇 |
1978年 | 37篇 |
1973年 | 32篇 |
1919年 | 24篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
1907年 | 32篇 |
1904年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Aftab Aslam Parwaz Khan Anish Khan Abdullah M Asiri Heba A Kashmery 《Russian Journal of Physical Chemistry B, Focus on Physics》2018,12(3):412-421
The oxidation of Rizatriptan by diperiodatoargentate(III) has been studied by spectrophotometry at neutral pH. The kinetics of the reaction of Rizatriptan has been shown to principle of non-complementary oxidation steps. The initial step involves the deprotonated of the diperiodatoargentate(III) with the alkali; this rearranges during the displacement of a ligand to give free periodate and takes up another ligand monoperiodateargentate(III), combines with a substrate to endow with an intermediate complex which decomposes within a slow step to provide the final product in the following step with a first-order rate constant. The main product was identified by spot test, Fourier- transform infrared spectroscopy, Nuclear magnetic resonance and Liquid chromatography-mass spectrometry spectrum. A conceivable mechanism including pre equilibrium of adducts development between the complex and reductant was planned from the kinetics study. The rate conditions got from system can clarify all exploratory phenomena, and the activation parameters alongside rate constants of the rate determining step were ascertained. 相似文献
992.
We analyze a pair of delay-coupled FitzHugh–Nagumo oscillators exhibiting in-out intermittency as a part of the generating mechanism of extreme events. We study in detail the characteristics of in-out intermittency and identify the invariant subsets involved – a saddle fixed point and a saddle periodic orbit – neither of which are chaotic as in the previously reported cases of in-out intermittency. Based on the analysis of a periodic attractor possessing in-out dynamics, we can characterize the approach to the invariant synchronization manifold and the spiralling out to the saddle periodic orbit with subsequent ejection from the manifold. Due to the striking similarities, this analysis of in-out dynamics also explains in-out intermittency 相似文献
993.
994.
Qiang Lai Xiao-Wen Zhao Jian-Ning Huang Viet-Thanh Pham Karthikeyan Rajagopal 《The European physical journal. Special topics》2018,227(7-9):719-730
This letter gives a general review on the monostability, bistability, periodicity and chaos in gene regulatory network. Some simple motifs that generate monostability, bistability, periodicity and chaos are analytically and numerically reported. Further research directions of the nonlinear dynamics of gene regulatory network are discussed. 相似文献
995.
Chen Yang Ying Chen Dan Liu Jinfeng Wang Cheng Chen Jiemin Wang Ye Fan Shaoming Huang Weiwei Lei 《Frontiers of Physics》2018,13(4):138101
Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperature (25, 80, and 120 ?C) and time (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45 min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the assynthesized γ-AlOOH NSs exhibit an outstanding NH3 adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH3 adsorption on the in-plane of the γ-AlOOH NSs is explained by the Lewis acid/base theory. The H-bond interactions among the NH3 molecules and the edge groups (-OH) further improve the capture ability of the nanosheets. 相似文献
996.
The search for and study of exotic quantum states in novel low-dimensional quantum materials have triggered extensive research in recent years. Here, we systematically study the electronic and magnetic structures in the newly discovered two-dimensional quantum material C3N within the framework of density functional theory. The calculations demonstrate that C3N is an indirect-band semiconductor with an energy gap of 0.38 eV, which is in good agreement with experimental observations. Interestingly, we find van Hove singularities located at energies near the Fermi level, which is half that of graphene. Thus, the Fermi energy easily approaches that of the singularities, driving the system to ferromagnetism, under charge carrier injection, such as electric field gating or hydrogen doping. These findings not only demonstrate that the emergence of magnetism stems from the itinerant electron mechanism rather than the effects of local magnetic impurities, but also open a new avenue to designing field-effect transistor devices for possible realization of an insulator–ferromagnet transition by tuning an external electric field. 相似文献
997.
998.
999.