全文获取类型
收费全文 | 375篇 |
免费 | 11篇 |
专业分类
化学 | 149篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 24篇 |
物理学 | 204篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 20篇 |
2011年 | 21篇 |
2010年 | 10篇 |
2009年 | 10篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 21篇 |
2005年 | 14篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 15篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1966年 | 3篇 |
1930年 | 2篇 |
排序方式: 共有386条查询结果,搜索用时 0 毫秒
211.
P. Novak B.P. Somerday R.O. Ritchie 《Journal of the mechanics and physics of solids》2010,58(2):206-226
Intergranular cracking associated with hydrogen embrittlement represents a particularly severe degradation mechanism in metallic structures which can lead to sudden and unexpected catastrophic fractures. As a basis for a strategy for the prognosis of such failures, here we present a comprehensive physical-based statistical micro-mechanical model of such embrittlement which we use to quantitatively predict the degradation in fracture strength of a high-strength steel with increasing hydrogen concentration, with the predictions verified by experiment. The mechanistic role of dissolved hydrogen is identified by the transition to a locally stress-controlled fracture, which is modeled as being initiated by a dislocation pile-up against a grain-boundary carbide which in turn leads to interface decohesion and intergranular fracture. Akin to cleavage fracture in steel, the “strength” of these carbides is modeled using weakest-link statistics. We associate the dominant role of hydrogen with trapping at dislocations; this trapped hydrogen reduces the stress that impedes dislocation motion and also lowers the reversible work of decohesion at the tip of dislocation pile-up at the carbide/matrix interface. Mechanistically, the model advocates the synergistic action of both the hydrogen-enhanced local plasticity and decohesion mechanisms in dictating failure. 相似文献
212.
Chiatti O Nicholls JT Proskuryakov YY Lumpkin N Farrer I Ritchie DA 《Physical review letters》2006,97(5):056601
We use an electron thermometer to measure the temperature rise of approximately 2 x 10(5) electrons in a two-dimensional box, due to heat flow into the box through a ballistic one-dimensional (1D) constriction. Using a simple model we deduce the thermal conductance kappa(Vg) of the 1D constriction, which we compare to its electrical conductance characteristics; for the first four 1D subbands the heat carried by the electrons passing through the wire is proportional to its electrical conductance G(Vg). In the vicinity of the 0.7 structure this proportionality breaks down, and a plateau at the quantum of thermal conductance pi(2)k(2/B)T/3h is observed. 相似文献
213.
C. L. Bell M. Dhib G. Hancock G. A. D. Ritchie J. H. van Helden N. J. van Leeuwen 《Applied physics. B, Lasers and optics》2009,94(2):327-336
Cavity enhanced absorption spectroscopy is performed using an external cavity diode laser operating around 1516 nm. We demonstrate
a sensitivity of 6×10−8 cm−1 Hz−1/2 and utilise a simple method to measure pressure-induced broadening and shift coefficients. The broadening and shift coefficients
for six gases (helium, neon, argon, xenon, oxygen and nitrogen) have been determined at room temperature for four transitions
in the υ
1+υ
3 combination band of ammonia. Comparisons of the broadening coefficients with previous work in this region, where it exists,
show good agreement. The broadening and shift coefficients of nitrogen and oxygen are also in good agreement with calculated
values using the Robert and Bonamy theory. Both the broadening and shift coefficients show a clear trend through the rare
gases, which can be explained in terms of the varying magnitude of the long range attractive forces operating between the
colliding partners. We also demonstrate the application of the Parmenter–Seaver formalism to estimate the potential well depth
of the ammonia dimer from the obtained broadening coefficients. The obtained well depth agrees well with theoretical calculations. 相似文献
214.
Hew WK Thomas KJ Pepper M Farrer I Anderson D Jones GA Ritchie DA 《Physical review letters》2008,101(3):036801
When a quantum wire is weakly confined, a conductance plateau appears at e;{2}/h with decreasing carrier density in zero magnetic field accompanied by a gradual suppression of the 2e;{2}/h plateau. Applying an in-plane magnetic field B_{ parallel} does not alter the value of this quantization; however, the e;{2}/h plateau weakens with increasing B_{ parallel} up to 9 T, and then strengthens on further increasing B_{ parallel}, which also restores the 2e;{2}/h plateau. Our results are consistent with spin-incoherent transport in a one-dimensional wire. 相似文献
215.
Baenninger M Ghosh A Pepper M Beere HE Farrer I Ritchie DA 《Physical review letters》2008,100(1):016805
We report direct experimental evidence that the insulating phase of a disordered, yet strongly interacting two-dimensional electron system becomes unstable at low temperatures. As the temperature decreases, a transition from insulating to metal-like transport behavior is observed, which persists even when the resistivity of the system greatly exceeds the quantum of resistivity h/e2. The results have been achieved by measuring transport on a mesoscopic length scale while systematically varying the strength of disorder. 相似文献
216.
217.
This paper shows that, with the exception of the first lot quantity, the E.O.Q. can be used for determining replenishment quantities, when demand is increasing linearly, with little cost penalty. 相似文献
218.
219.
220.
We demonstrate and characterize the generation of single-tone frequency-modulated and frequency-doubled radiation at 400 MHz and 430 nm. We obtained the radiation at 430 nm by frequency doubling light from a current-modulated 860-nm diode laser, using noncritical type I phase matching in a KNbO(3) crystal. The optical spectrum of the doubled light was found to be in keeping with our expectations based on the measured frequency- and amplitude-modulation indices of the fundamental radiation. The experimentally measured diode laser and crystal parameters were used to simulate the in-phase and quadrature signals that would be observed in a single-tone frequency-modulation spectroscopy experiment. 相似文献