全文获取类型
收费全文 | 882篇 |
免费 | 14篇 |
专业分类
化学 | 519篇 |
晶体学 | 43篇 |
力学 | 35篇 |
数学 | 70篇 |
物理学 | 229篇 |
出版年
2022年 | 5篇 |
2020年 | 9篇 |
2019年 | 5篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 31篇 |
2012年 | 39篇 |
2011年 | 30篇 |
2010年 | 18篇 |
2009年 | 18篇 |
2008年 | 32篇 |
2007年 | 43篇 |
2006年 | 35篇 |
2005年 | 34篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 23篇 |
2000年 | 27篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 27篇 |
1995年 | 30篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 17篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1978年 | 17篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1972年 | 12篇 |
1970年 | 10篇 |
1935年 | 4篇 |
排序方式: 共有896条查询结果,搜索用时 0 毫秒
81.
82.
N. Haas D. Herlach W. Jacobs H. -J. Mundinger J. Rosenkranz H. -E. Schaefer M. Schmolz A. Seeger K. -P. Döring K. Fürderer M. Gladisch 《Hyperfine Interactions》1986,31(1-4):217-222
The transverse spin relaxation of positive muons has been measured on an Al single crystal and on polycrystalline In after
irradiation with 2 MeV electrons at 9 K or 11 K, sample transfer at 4.2 K, and various subsequent annealing treatments. The
Al data are analysed in terms of diffusion-limited trapping by vacancies. This yields a muon diffusivityD
μ which within experimental accuracy is proportional toT between 4 K and 50 K, indicating that in this temperature intervalD
μ is dominated by one-phonon-assisted incoherent tunnelling. In In only very small effects due to the irradiation could be
observed. The muons appear to be localized in octahedral interstices. From the motional averaging taking place above about
20 K the diffusivity ofD
μ in In is deduced. 相似文献
83.
Background oriented schlieren for flow visualisation in hypersonic impulse facilities 总被引:1,自引:0,他引:1
Experiments to demonstrate the use of the background-oriented schlieren (BOS) technique in hypersonic impulse facilities are
reported. BOS uses a simple optical set-up consisting of a structured background pattern, an electronic camera with a high
shutter speed and a high intensity light source. The visualization technique is demonstrated in a small reflected shock tunnel
with a Mach 4 conical nozzle, nozzle supply pressure of 2.2 MPa and nozzle supply enthalpy of 1.8 MJ/kg. A 20° sharp circular
cone and a model of the MUSES-C re-entry body were tested. Images captured were processed using PIV-style image analysis to
visualize variations in the density field. The shock angle on the cone measured from the BOS images agreed with theoretical
calculations to within 0.5°. Shock standoff distances could be measured from the BOS image for the re-entry body. Preliminary
experiments are also reported in higher enthalpy facilities where flow luminosity can interfere with imaging of the background
pattern.
A version of this paper was presented at the 25th International Symposium on Shock Waves in Bangalore in July 2005. 相似文献
84.
Cole JJ Barry CR Knuesel RJ Wang X Jacobs HO 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):7321-7329
Contact electrification creates an invisible mark, overlooked and often undetected by conventional surface spectroscopic measurements. It impacts our daily lives macroscopically during electrostatic discharge and is equally relevant on the nanoscale in areas such as soft lithography, transfer, and printing. This report describes a new conceptual approach to studying and utilizing contact electrification beyond prior surface force apparatus and point-contact implementations. Instead of a single point contact, our process studies nanocontact electrification that occurs between multiple nanocontacts of different sizes and shapes that can be formed using flexible materials, in particular, surface-functionalized poly(dimethylsiloxane) (PDMS) stamps and other common dielectrics (PMMA, SU-8, PS, PAA, and SiO(2)). Upon the formation of conformal contacts and forced delamination, contacted regions become charged, which is directly observed using Kelvin probe force microscopy revealing images of charge with sub-100-nm lateral resolution. The experiments reveal chemically driven interfacial proton exchange as the dominant charging mechanism for the materials that have been investigated so far. The recorded levels of uncompensated charges approach the theoretical limit that is set by the dielectric breakdown strength of the air gap that forms as the surfaces are delaminated. The macroscopic presence of the charges is recorded using force-distance curve measurements involving a balance and a micromanipulator to control the distance between the delaminated objects. Coulomb attraction between the delaminated surfaces reaches 150 N/m(2). At such a magnitude, the force finds many applications. We demonstrate the utility of printed charges in the fields of (i) nanoxerography and (ii) nanotransfer printing whereby the smallest objects are ~10 nm in diameter and the largest objects are in the millimeter to centimeter range. The printed charges are also shown to affect the electronic properties of contacted surfaces. For example, in the case of a silicon-on-insulator field effect transistors are in contact with PDMS and subsequent delamination leads to threshold voltage shifts that exceed 500 mV. 相似文献
85.
86.
Unsaturated acyloxy sulfones 3 undergo intramolecular cyclization upon deprotonation with LHMDS in THF. Dehydration and double bond isomerization of the products upon exposure to acid, gave the fused ring furans, 4, in good yields. This strategy could be readily adapted to prepare substituted benzofurans 12 from the cyclization reactions of acyloxy sulfones 11 prepared from phenols. Finally, this approach could be successfully modified to access dihydropyrans and benzopyrans. 相似文献
87.
Dreyfuss JM Jacobs C Gindin Y Benson G Staples GO Zaia J 《Analytical and bioanalytical chemistry》2011,399(2):727-735
Hydrophilic interaction chromatography (HILIC) liquid chromatography/mass spectrometry (LC/MS) is appropriate for all native
and reductively aminated glycan classes. HILIC carries the advantage that retention times vary predictably according to oligosaccharide
composition. Chromatographic conditions are compatible with sensitive and reproducible glycomics analysis of large numbers
of samples. The data are extremely useful for quantitative profiling of glycans expressed in biological tissues. With these
analytical developments, the rate-limiting factor for widespread use of HILIC LC/MS in glycomics is the analysis of the data.
In order to eliminate this problem, a Java-based open source software tool, Manatee, was developed for targeted analysis of
HILIC LC/MS glycan datasets. This tool uses user-defined lists of compositions that specify the glycan chemical space in a
given biological context. The program accepts high-resolution LC/MS data using the public mzXML format and is capable of processing
a large data file in a few minutes on a standard desktop computer. The program allows mining of HILIC LC/MS data with an output
compatible with multivariate statistical analysis. It is envisaged that the Manatee tool will complement more computationally
intensive LC/MS processing tools based on deconvolution and deisotoping of LC/MS data. The capabilities of the tool were demonstrated
using a set of HILIC LC/MS data on organ-specific heparan sulfates. 相似文献
88.
89.
We present a pedagogical treatment of the formalism of continuous quantum measurement. Our aim is to show the reader how the equations describing such measurements are derived and manipulated in a direct manner. We also give elementary background material for those new to measurement theory, and describe further various aspects of continuous measurements that should be helpful to those wanting to use such measurements in applications. Specifically, we use the simple and direct approach of generalized measurements to derive the stochastic master equation describing the continuous measurements of observables, give a tutorial on stochastic calculus, treat multiple observers and inefficient detection, examine a general form of the measurement master equation, and show how the master equation leads to information gain and disturbance. To conclude, we give a detailed treatment of imaging the resonance fluorescence from a single atom as a concrete example of how a continuous position measurement arises in a physical system. 相似文献
90.
While feedback control has many applications in quantum systems, finding optimal control protocols for this task is generally challenging. So-called ‘verification theorems’ and ‘viscosity solutions’ provide two useful tools for this purpose: together they give a simple method to check whether any given protocol is optimal, and provide a numerical method for finding optimal protocols. While treatments of verification theorems usually use sophisticated mathematical language, this is not necessary. In this article we give a simple introduction to feedback control in quantum systems, and then describe verification theorems and viscosity solutions in simple language. We also illustrate their use with a concrete example of current interest. 相似文献