全文获取类型
收费全文 | 2436篇 |
免费 | 48篇 |
国内免费 | 10篇 |
专业分类
化学 | 1569篇 |
晶体学 | 33篇 |
力学 | 22篇 |
数学 | 426篇 |
物理学 | 444篇 |
出版年
2020年 | 13篇 |
2019年 | 23篇 |
2018年 | 14篇 |
2017年 | 19篇 |
2016年 | 34篇 |
2015年 | 29篇 |
2014年 | 32篇 |
2013年 | 114篇 |
2012年 | 74篇 |
2011年 | 94篇 |
2010年 | 45篇 |
2009年 | 55篇 |
2008年 | 114篇 |
2007年 | 92篇 |
2006年 | 87篇 |
2005年 | 127篇 |
2004年 | 84篇 |
2003年 | 87篇 |
2002年 | 88篇 |
2001年 | 47篇 |
2000年 | 45篇 |
1999年 | 30篇 |
1998年 | 41篇 |
1997年 | 31篇 |
1996年 | 55篇 |
1995年 | 46篇 |
1994年 | 54篇 |
1993年 | 45篇 |
1992年 | 41篇 |
1991年 | 29篇 |
1990年 | 34篇 |
1989年 | 31篇 |
1988年 | 36篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 28篇 |
1984年 | 35篇 |
1983年 | 20篇 |
1982年 | 23篇 |
1981年 | 41篇 |
1980年 | 36篇 |
1979年 | 31篇 |
1978年 | 23篇 |
1977年 | 27篇 |
1976年 | 22篇 |
1975年 | 24篇 |
1974年 | 24篇 |
1973年 | 26篇 |
1969年 | 10篇 |
1912年 | 8篇 |
排序方式: 共有2494条查询结果,搜索用时 15 毫秒
161.
M.W. Todd R.A. Provencal T.G. Owano B.A. Paldus A. Kachanov K.L. Vodopyanov M. Hunter S.L. Coy J.I. Steinfeld J.T. Arnold 《Applied physics. B, Lasers and optics》2002,75(2-3):367-376
A novel instrument, based on cavity-ringdown spectroscopy (CRDS), has been developed for trace gas detection. The new instrument
utilizes a widely tunable optical parametric oscillator (OPO), which incorporates a zinc–germanium–phosphide (ZGP) crystal
that is pumped at 2.8 μm by a 25-Hz Er,Cr:YSGG laser. The resultant mid-IR beam profile is nearly Gaussian, with energies
exceeding 200 μJ/pulse between 6 and 8 μm, corresponding to a quantum conversion efficiency of approximately 35%. Vapor-phase
mid-infrared spectra of common explosives (TNT, TATP, RDX, PETN and Tetryl) were acquired using the CRDS technique. Parts-per-billion
concentration levels were readily detected with no sample preconcentration. A collection/flash-heating sequence was implemented
in order to enhance detection limits for ambient air sampling. Detection limits as low as 75 ppt for TNT are expected, with
similar concentration levels for the other explosives.
Received: 1 April 2002 / Revised version: 13 June 2002 / Published online: 12 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-408/524-0551, E-mail: mtodd@picarro.com 相似文献
162.
163.
The 1:1 mole ratio reaction of t-Bu3In with Sb(SiMe3)3 results in the formation of the Lewis acid-base adduct t-Bu3In Sb(SiMe3)3 (1), while the dimeric compound [t-Bu2InSb(SiMe3)2]2 (2) is isolated from the 1:1 reaction of t-Bu2InCl with Sb(SiMe3)3. Both the 2:1 reactions of t-Bu2InCl with Sb(SiMe3)3 and t-Bu2InCl with 2 result in the formation of the mixed-bridge compound
(3), however, 1H NMR studies suggest that this compound is unstable in solution. Thermolysis of 1, 2, and t-Bu3Ga Sb(SiMe3)3 (4) results in the formation of nanocrystalline InSb or GaSb through a -hydride elimination pathway. 相似文献
164.
Al- and Co-substituted lithium nickel oxide of the nominal composition Li(Ni0.75Al0.17Co0.08)O2 was synthesised by a coprecipitation technique and by several solid state routes. Rietveld analysis of XRD profiles and galvanostatic
cycling in glass cells were performed for structural and electrochemical characterisation. Depending on the reactivity of
the respective precursor, there is in each case a minimal synthesis temperature, at which a single phase of the R
layered structure could be obtained. The coprecipitation technique and solid state routes using pre-substituted nickel hydroxide
are suitable for the synthesis of single phase Al- and Co-substituted lithium nickel oxide, even at rather low synthesis temperatures.
The electrochemical performance of lithium nickel oxide Li(Ni0.75Al0.17Co0.08)O2 synthesised in air is poor due to an enhanced lithium nickel disorder. Synthesis in oxygen atmosphere seems to be required.
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
165.
166.
Steven Arnold 《Journal of multivariate analysis》1984,15(3):325-335
Fairly general sufficient conditions are given to guarantee that invariant tests about means in the multivariate linear model and the repeated measures model have the correct asymptotic size when the normal assumption under which the tests are derived is relaxed. These conditions are the same as Huber's condition which guarantees asymptotic validity of the size of the F-test for the univariate linear model. 相似文献
167.
The interaction between morphological structure and phase behaviour of a LC side group block copolymer has been investigated using DSC, TEM and small angle X-ray diffraction. All samples of Polystyrene-block-2-(3-cholesteryloxycarbonyloxy)ethyl methacrylate (PS-b-PChEMA) show a phase separation between the two blocks. It was found that in the case of those samples where the liquid crystalline sub-phase is not continuous (spheres), only a nematic phase is seen, whereas in all samples in which there is a continuous liquid crystalline sub-phase, the smectic A phase of the homopolymer is formed. On the other hand, the block copolymer seems to stabilize the LC phase; no dependency of the clearing temperatures on the molecular weight of the LC blocks has been observed. 相似文献
168.
169.
B. Luk'yanchuk N. Bityurin N. Arnold D. Bäuerle 《Applied Physics A: Materials Science & Processing》1996,62(5):397-401
The role of non-stationary effects in nano-second ultraviolet (UV) excimer-laser ablation of organic polymers is discussed. The model includes reversible changes in absorption related to darkening and bleaching effects. Comparison of calculations and experimental data for polyimide demonstrates that the photophysical model describes the ablation kinetics quite well. 相似文献
170.