全文获取类型
收费全文 | 942篇 |
免费 | 17篇 |
国内免费 | 5篇 |
专业分类
化学 | 489篇 |
晶体学 | 7篇 |
力学 | 23篇 |
数学 | 129篇 |
物理学 | 316篇 |
出版年
2023年 | 8篇 |
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 13篇 |
2019年 | 17篇 |
2018年 | 20篇 |
2017年 | 22篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 30篇 |
2013年 | 51篇 |
2012年 | 46篇 |
2011年 | 51篇 |
2010年 | 42篇 |
2009年 | 42篇 |
2008年 | 57篇 |
2007年 | 37篇 |
2006年 | 46篇 |
2005年 | 36篇 |
2004年 | 30篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 19篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 15篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1965年 | 4篇 |
1957年 | 4篇 |
1936年 | 4篇 |
排序方式: 共有964条查询结果,搜索用时 31 毫秒
61.
Vishal Kesari P. K. Jain B. N. Basu 《International Journal of Infrared and Millimeter Waves》2007,28(6):443-449
In the method of tapering the cross section of the interaction structure for broadbanding a gyro-TWT, the different portions
of the interaction length of the tapered-cross-section waveguide become effective for different frequency ranges if the magnetic
field and beam parameters are profiled to maintain the condition of electron cyclotron resonance throughout the interaction
length. In the present paper, the study of profiling the magnetic field and beam parameters in steps of the stepped analytical
model of a double-tapered disc-loaded circular waveguide was made throughout the steps of the model. In the observed profile,
the magnetic flux density in a typical step relative to its value in first-step decreases from first-step (gun-end) to end-step
(collector-end) of the model considering the up-tapering schemes, in which structure parameters increase from gun-end to collector-end.
Also, the transverse beam velocity in a typical step relative to its value in first-step decreases from gun-end to collector-end.
However, the Larmor radius in a typical step relative to its value in first-step as well as the hollow-beam radius in a typical
step relative to its value in first-step, both increase from gun-end to collector-end in the model considering the up-tapering
schemes. 相似文献
62.
The mixing of the glueball candidate?i(1,460) with η and η′ is studied in a chiral symmetry breaking framework. Using the solutions of anomalous Ward identities for flavourU(3)×U(3), we find that the octet-singlet mixing angle is quite large and that our results are consistent with a large glueball component in?i(1,460) with moderate gluonium mixing in η and η′. 相似文献
63.
In this Letter, we describe the novel synthetic approach to the tricyclic core of (±)-galanthamine from the easily available starting material isovanillin. 相似文献
64.
Asis Basu 《Annals of Physics》2005,319(2):274-285
The enveloping algebra, Dn, of fermions is extended on the lattice to include the discrete space invariance. This extended algebra, denoted X, has the space symmetry as a factor: X/Dn = space group. 相似文献
65.
66.
67.
Birefringent filters can be used for tuning lasers, with some advantages over prisms, gratings and tilted etalons. In this paper the transmission characteristics of a new mixed birefringent filter are investigated. The term ‘mixed’ is used because both circular birefringence and linear birefringence have been utilized in the fabrication of this filter.It has a loss-less core, formed by a cascaded system of alternate rotators and retarders, and a linear polarizer at each end. The performance of this filter is better because of the more effective suppression of side peaks. Unlike previous birefringent filters, this one may be used inside a linear resonator. 相似文献
68.
In this paper we report a new geometry for diode laser pumping. We show that an efficient moving-disc laser can be designed which can operate at 20 kW of average power with existing diode laser technology. 相似文献
69.
A model forN-N interaction proposed earlier by two of us (VSB and VKG), has been extended to incorporate the tensor component of the nuclear
force. Based on the quark compound bag model (QCB), the nucleon-nucleon potential has a short range repulsive core which is
non-local and has a characteristic energy dependence and is expressed in terms of the parameters relating to the six-quark
compound bag. To account for the low energy properties, this repulsive core interaction is supplemented by a phenomenological
non-local potential containing both central (S-wave) and tensor components and operates only outside the QCB. Using this model, we analyse and compare the results with
the experimental data for the electromagnetic form factors of the deuteron, theD-state observables, such as the quadrupole moment, theD-state probability, and theD/S ratio along with then-p scattering phase shifts up to about 400 MeV. 相似文献
70.