全文获取类型
收费全文 | 1051篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
化学 | 702篇 |
晶体学 | 20篇 |
力学 | 5篇 |
数学 | 215篇 |
物理学 | 142篇 |
出版年
2021年 | 18篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 21篇 |
2016年 | 37篇 |
2015年 | 46篇 |
2014年 | 29篇 |
2013年 | 65篇 |
2012年 | 56篇 |
2011年 | 53篇 |
2010年 | 42篇 |
2009年 | 38篇 |
2008年 | 46篇 |
2007年 | 52篇 |
2006年 | 37篇 |
2005年 | 39篇 |
2004年 | 25篇 |
2003年 | 16篇 |
2002年 | 22篇 |
2001年 | 7篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 15篇 |
1976年 | 7篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1966年 | 9篇 |
1958年 | 23篇 |
1957年 | 10篇 |
1956年 | 6篇 |
排序方式: 共有1084条查询结果,搜索用时 484 毫秒
81.
Pradeep K. Jaiswal Vashundhra Sharma Jaroslav Prikhodko Irina V. Mashevskaya Sandeep Chaudhary 《Tetrahedron letters》2017,58(22):2077-2083
For the first time, an efficient, simple, synthetic green protocol for the one-pot synthesis of functionalized 2-oxo-benzo[1,4]oxazines 24–29 in water under ultrasound irradiation is presented. As compared to conventional methods, the present protocol avoids traditional chromatography and purification steps and furnished the target molecules in excellent yields (upto 98%) with no side products. The methodology was also demonstrated on gram scale synthesis. Moreover, functionalized 2-oxo-quinoxaline analogues 31–33, another class of bio-active heterocyclic scaffolds, were also prepared using this method. For the first time, this protocol was successfully applied in the synthesis of the anticancer indole alkaloid, Cephalandole A 35. 相似文献
82.
Jaroslav Menčík 《Meccanica》2007,42(1):19-29
The paper reviews the current state of the depth-sensing indentation (sometimes called nanoindentation), where the information
on material behaviour and properties is obtained from the indenter load and depth, measured continuously during loading and
unloading. It is shown how the contact parameters and principal characteristics are determined using pointed or spherical
indenters. Indentation tests can be used for the measurement of hardness and elastic modulus, and also of the yield stress
and for the construction of stress–strain diagrams, for the determination of the work of indentation and its components. Most
devices use monotonic loading and unloading, but some also enable measurement under a small harmonic signal added to the basic
monotonously increasing load. This makes possible continuous measurement of contact stiffness and the study of dynamic properties
and the determination of properties of coatings. One section is devoted to the measurement on viscoelastic-plastic materials,
where the delayed deforming must be considered during the measurement as well as in data evaluation. Instrumented indentation
can also be used for the study of creep under high temperatures. The paper also discusses the errors arising in depth-sensing
measurements and informs briefly about some other possibilities of the method. 相似文献
83.
R. Yahiaoui H. Němec P. Kužel F. Kadlec C. Kadlec P. Mounaix 《Applied Physics A: Materials Science & Processing》2011,103(3):689-692
This work presents theoretical and experimental investigations of a tunable metamaterial which exhibits negative permeability
in the THz frequency range. The tunability is obtained by temperature changes, and the sample consists of an array of high-permittivity
SrTiO3 (STO) rods micromachined by a femtosecond laser. Structures exhibiting a negative permeability on multiple frequency bands
are also investigated and a proper choice of the dimensions of the pattern allows us to achieve a substantial broadening of
the frequency band with negative μ. 相似文献
84.
85.
It is possible to describe the pressure degradation of microorganisms as being analogous to thermal inactivation. Equation for baroinactivation is derived from thermal death time (TDT) model D p = D pref 10(pref-p)/z p , where D pref is decimal reduction time at the reference pressure (min), p ref is the reference pressure (MPa), z p is the pressure increase (MPa) required to reduce the D p value by a factor of 10. This method was used for the calculation of baroinactivation model parameters of the total number of microorganisms of pressurized germinated mung bean (green gram) seeds (Vigna radiata (L.) Wilczek). Microbial contamination of germinated mung bean (green gram) seeds can be effectively decreased by treatment at a high pressure of 400 MPa, time of pressurization 5 min. 相似文献
86.
Černý Miroslav Šandera Pavel Pokluda Jaroslav 《Czechoslovak Journal of Physics》1999,49(10):1495-1501
Ab initio calculation of ideal strength of cubic crystals under three-axial tension was performed using the LMTO-ASA method. Computed values are in a good agreement with those obtained previously by means of semi-empirical polynomial approach. The values of equilibrium lattice parameter obtained in the framework of ab initio method are well comparable with the experimental data whereas a less satisfactory agreement was achieved in the case of bulk moduli. 相似文献
87.
Abstract The main results of this paper give two criteria for certain infinite series of rational numbers to be Liouville. Some examples
are also included.
Keywords: Liouville numbers, Infinite series
Mathematics Subject Classification (2000): 11J82 相似文献
88.
We give conditions sufficient for sequences consisting of real numbers to ensure that their expressible sets have Hausdorff
dimension zero. 相似文献
89.
Ale Ricka Libor Dostl Roman Jambor Vladimír Buchta Jirí Brus Ivana Císarov Michal Holcapek Jaroslav Holecek 《应用有机金属化学》2002,16(6):315-322
A set of seven [2,6‐bis(dimethylaminomethyl)phenyl]diphenyltin(IV) ({[(CH3)2NCH2]2(C6H3)}(C6H5)2Sn+X?) ionic organotin(IV) compounds (X = Br, NO3, CN, SCN, SeCN, BF4 and PF6) has been prepared and characterized by electrospray ionization mass spectrometry, 1H NMR spectroscopy in CDCl3,119Sn NMR in CDCl3 and DMSO‐d6 solution, as well as by 13C and 119Sn CP/MAS NMR spectroscopy and X‐ray diffraction techniques in the solid state. The in vitro antifungal activity of these water‐soluble ionic organotin(IV) compounds was compared with starting compounds and the antifungal drugs currently in clinical use. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
90.