全文获取类型
收费全文 | 1200篇 |
免费 | 49篇 |
国内免费 | 10篇 |
专业分类
化学 | 831篇 |
晶体学 | 13篇 |
力学 | 35篇 |
数学 | 141篇 |
物理学 | 239篇 |
出版年
2023年 | 13篇 |
2022年 | 25篇 |
2021年 | 28篇 |
2020年 | 29篇 |
2019年 | 30篇 |
2018年 | 40篇 |
2017年 | 22篇 |
2016年 | 54篇 |
2015年 | 34篇 |
2014年 | 50篇 |
2013年 | 99篇 |
2012年 | 76篇 |
2011年 | 88篇 |
2010年 | 49篇 |
2009年 | 54篇 |
2008年 | 97篇 |
2007年 | 72篇 |
2006年 | 75篇 |
2005年 | 71篇 |
2004年 | 44篇 |
2003年 | 36篇 |
2002年 | 26篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1998年 | 12篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1967年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有1259条查询结果,搜索用时 31 毫秒
101.
Siddiqi I Vijay R Pierre F Wilson CM Metcalfe M Rigetti C Frunzio L Devoret MH 《Physical review letters》2004,93(20):207002
We have constructed a new type of amplifier whose primary purpose is the readout of superconducting quantum bits. It is based on the transition of a rf-driven Josephson junction between two distinct oscillation states near a dynamical bifurcation point. The main advantages of this new amplifier are speed, high sensitivity, low backaction, and the absence of on-chip dissipation. Pulsed microwave reflection measurements on nanofabricated Al junctions show that actual devices attain the performance predicted by theory. 相似文献
102.
[reaction: see text] Lewis acid-promoted addition of allyltri-n-butylstannane to o-quinonediimines afforded tetrahydroquinoxaline derivatives or allylated amides depending on the nature of the substituent on imine nitrogen. 相似文献
103.
Vijay Gupta 《Journal of Mathematical Analysis and Applications》2004,289(1):292-300
Guo (Approx. Theory Appl. 4 (1988) 9-18) introduced the integral modification of Meyer-Konig and Zeller operators and studied the rate of convergence for functions of bounded variation. In this paper we introduce the Bézier variant of these integrated MKZ operators and study the rate of convergence by means of the decomposition technique of functions of bounded variation together with some results of probability theory and the exact bound of MKZ basis functions. Recently, Zeng (J. Math. Anal. Appl. 219 (1998) 364-376) claimed to improve the results of Guo and Gupta (Approx. Theory Appl. 11 (1995) 106-107), but there is a major mistake in the paper of Zeng. For special case our main theorem gives the correct estimate on the rate of convergence, over the result of Zeng. 相似文献
104.
We explore the phases of
supersymmetric U(N) gauge theories with fundamental matter that arise as deformations of
SQCD by the addition of a superpotential for the adjoint chiral multiplet. As the parameters in the superpotential are varied, the vacua of this theory sweep out various branches, which in some cases have multiple semiclassical limits. In such limits, we recover the vacua of various product gauge group theories, with flavors charged under some group factors. We describe in detail the structure of the vacua in both classical and quantum regimes, and develop general techniques such as an addition and a multiplication map which relate vacua of different gauge theories. We also consider possible indices characterizing different branches and potential relationships with matrix models. 相似文献
105.
We propose an efficient method for the prediction of protein folding rate constants and mechanisms. We use molecular dynamics simulation data to build Markovian state models (MSMs), discrete representations of the pathways sampled. Using these MSMs, we can quickly calculate the folding probability (P(fold)) and mean first passage time of all the sampled points. In addition, we provide techniques for evaluating these values under perturbed conditions without expensive recomputations. To demonstrate this method on a challenging system, we apply these techniques to a two-dimensional model energy landscape and the folding of a tryptophan zipper beta hairpin. 相似文献
106.
Mukhopadhyay S Zerella M Bell AT Srinivas RV Smith GS 《Chemical communications (Cambridge, England)》2004,(4):472-473
Methane is transformed selectively to methanesulfonyl chloride at low temperature by liquid-phase reaction of methane with SO(2)Cl(2) in the presence of a free radical initiator and a promoter using 100% H(2)SO(4) as the solvent. 相似文献
107.
Vijay Gupta 《分析论及其应用》2003,19(1):81-88
In the present paper, we introduce Szasz-Durrmeyer-Bezier operators M.,.(f,x) , which generalize the Szasz-Durrmeyer operators. Here we obtain an estimate on the rate of convergence of Mn,a(f,x) for functions of bounded variation. Our result extends and improves that of Sahai and Prasad and Gupta and Pant. 相似文献
108.
By using distributed computing techniques and a supercluster of more than 20,000 processors we simulated folding of a 20-residue Trp Cage miniprotein in atomistic detail with implicit GB/SA solvent at a variety of solvent viscosities (gamma). This allowed us to analyze the dependence of folding rates on viscosity. In particular, we focused on the low-viscosity regime (values below the viscosity of water). In accordance with Kramers' theory, we observe approximately linear dependence of the folding rate on 1/gamma for values from 1-10(-1)x that of water viscosity. However, for the regime between 10(-4)-10(-1)x that of water viscosity we observe power-law dependence of the form k approximately gamma(-1/5). These results suggest that estimating folding rates from molecular simulations run at low viscosity under the assumption of linear dependence of rate on inverse viscosity may lead to erroneous results. 相似文献
109.
Vijay Natraj Robert J.D. Spurr 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,107(2):263-293
We calculate the reflection matrix for the first two orders of scattering in a vertically inhomogeneous, scattering-absorbing medium. We take full account of polarization and perform a complete linearization (analytic differentiation) of the reflection matrix with respect to both the inherent optical properties of the medium and the surface reflection condition. Further, we compute a scalar-vector correction to the total intensity due to the effect of polarization; this correction is also fully linearized. The solar beam attenuation has been computed for a pseudo-spherical atmosphere.Results from the two orders of scattering (2OS) model have been tested against scalar intensities for an inhomogeneous atmosphere, and against Stokes vector results for a homogeneous atmosphere. We have also performed backscatter simulations of reflected sunlight in the O2A band for a variety of geometries, and compared our results with those from a full vector multiple scattering code. Our results are exact in the center of strong lines and most inaccurate in the continuum, where polarization is least significant. The s- and p-polarized radiances are always computed very accurately. The effect of gas absorption optical depth, solar zenith angle, viewing geometry, surface albedo and wind speed (in the case of ocean glint) on the intensity, polarization and corresponding weighting functions have been investigated. It is shown that the 2OS model provides fast and reliably accurate polarization corrections to the scalar-model radiance and weighting function fields. The model can be implemented in operational retrieval algorithms as an adjunct radiative transfer code to deal with polarization effects. 相似文献
110.
Muhammad Ejaz Bhanukiran Sunkara Lakhinder Kamboj Jibao He Vijay T. John Noshir S. Pesika Scott M. Grayson 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3314-3322
An efficient and novel one‐pot process is developed to immobilize the atom transfer radical polymerization (ATRP) initiators onto the surface of fully pyrolyzed carbon hard spheres (CHSs) via a radical trapping process from the in situ thermal decomposition of bis(bromomethylbenzoyl)peroxide. The CHSs do not require any additional preparative treatment prior to the initiator immobilization. Styrene and methyl methacrylate are polymerized onto initiator‐immobilized CHSs by surface‐initiated atomic transfer radical polymerization (SI‐ATRP). Samples are characterized using Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. These methods of characterization confirmed that all the CHSs are coated with a uniform layer of grafted polymer. This efficient, one‐pot immobilization of ATRP‐initiators represents an exceptionally simple route for the rapid preparation of various polymer‐coated carbon‐based nanomaterials using SI‐ATRP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3314–3322 相似文献