全文获取类型
收费全文 | 2263篇 |
免费 | 119篇 |
国内免费 | 11篇 |
专业分类
化学 | 1073篇 |
晶体学 | 15篇 |
力学 | 63篇 |
数学 | 120篇 |
物理学 | 482篇 |
无线电 | 640篇 |
出版年
2024年 | 5篇 |
2023年 | 27篇 |
2022年 | 35篇 |
2021年 | 47篇 |
2020年 | 37篇 |
2019年 | 44篇 |
2018年 | 39篇 |
2017年 | 35篇 |
2016年 | 73篇 |
2015年 | 59篇 |
2014年 | 76篇 |
2013年 | 153篇 |
2012年 | 146篇 |
2011年 | 139篇 |
2010年 | 106篇 |
2009年 | 105篇 |
2008年 | 156篇 |
2007年 | 145篇 |
2006年 | 146篇 |
2005年 | 128篇 |
2004年 | 110篇 |
2003年 | 100篇 |
2002年 | 105篇 |
2001年 | 62篇 |
2000年 | 50篇 |
1999年 | 31篇 |
1998年 | 29篇 |
1997年 | 27篇 |
1996年 | 38篇 |
1995年 | 31篇 |
1994年 | 17篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1968年 | 2篇 |
1963年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有2393条查询结果,搜索用时 0 毫秒
111.
Tae Oan Ahn Jung Ho Kim Han Mo Jeong Sang Won Lee Lee Soon Park 《Journal of Polymer Science.Polymer Physics》1994,32(1):21-28
The compatibilizing effect of polyarylate-polystyrene (PAR-PS) block copolymer prepared from macroazo initiator was examined in polyarylate/polystyrene blends from the view-points of morphology, density, and thermal, mechanical, and rheological properties. PARPS block copolymer enhanced the mutual dissolution of the homopolymers. Reduced dispersed-domain size and increased density showed the efficiency of the block copolymer as a compatibilizing agent. Results from mechanical and rheological properties could also be explained by the compatibilizing effect of PAR-PS block copolymer in the blends. © 1994 John Wiley & Sons, Inc. 相似文献
112.
The Percus-Yevick equation for the Widom-Rowlinson model is solved exactly in one and three dimensions. In one dimension the direct correlation function is obtained explicitely. In three dimensions only the thermodynamic properties have been obtained so far implicitely in terms of elliptic integrals, and there is a maximum density beyond which the P.Y. equation has no solution and that before that density is ‘critical density’ at which the homogenous state becomes unstable. 相似文献
113.
From Melampyrum silvaticum L. (Scrophulariaceae) the new Iridoid melampyrosid (2) was isolated beside aucubin (1). The structure of 2 is determined by spectral data and chemical reactions. 相似文献
114.
In space-division multiple access (SDMA), different beamforming or space-domain precoding techniques can be applied. We investigate two different space-domain precoding methods, the maximum capacity (MC) and the minimum mean square error (MMSE) precoders, for the downlink channel. It is shown that the MMSE precoding, which is practically implementable, can provide a reasonable performance in terms of the capacity and error probability, while the MC precoding is not practical (although it is optimum in terms of the capacity). Space-domain precoding methods are also applied to code-division multiple access (CDMA) systems.This work was supported by the HY-SDR Research Center at Hanyang University, Seoul, Korea, under the ITRC Program of MIC, Korea.Jinho Choi was born in Seoul, Korea. He recieved the B.E. degree (magna cum laude) in electronics engineering from Sogang University in 1989 and the M.S.E. and Ph.D. degree in electrical engineering from the Korea Advanced Institute of Science and Technology in 1991 and 1994, respectively. Currently he is a Senior Lecturer in the School of Electrical Engineering and Telecommunications,University of New South Wales, Australia. Dr. Choi received the 1999 Best Paper Award of Signal Processing from EURASIP.Seungwon Choi received the B.S. degree from Hanyang University, Seoul, Korea, in 1980 and the M.S. degree from Seoul National University, Seoul, in 1982, both the electronic engineering. He received the M.S. degree in computer engineering in 1985 and the Ph.D degree in electrical engineering in 1988 from Syracuse University, Syracuse, NY.From 1982 to 1984, he was with LG Electronics Co. Ltd., Seoul, where he helped developed the 8-mm camcorder system. From 1988 to 1989, he was with the Department of Electrical and Computer Engineering, Syracuse University, as an Assistant Professor. In 1989, he joined the Electronics and Telecommunications Research Institute, daejeon, Korea, where he developed the adaptive algorithm for real-time application in secure telephone systems. From 1990 to 1992, he was with yhe Communication Research Laboratory, Tokyo, Japan, as a science and Technology Agency Fellow, developing adaptive antenna array system and adaptive equalizing filters for applications in land-mobile communications. He joined Hanyang University, Seoul, in 1992 as an Assistant Professor. He is a Professor in the School of Electrical and Computer Engineering, Hanyang University. His research interests include digital communications and adaptive signal processing with a recent focus on the real-time implementation of smart antenna system for 3G mobile communication system. 相似文献
115.
Ahn TK Yoon ZS Hwang IW Lim JK Rhee H Joo T Sim E Kim SK Aratani N Osuka A Kim D 《The journal of physical chemistry. B》2005,109(22):11223-11230
We have investigated the overall excitation energy relaxation dynamics in linear porphyrin arrays as well as the energy transport phenomena by attaching an energy acceptor to one end of a linear porphyrin array by using steady state and time-resolved spectroscopic measurements. We have revealed that the solvation dynamics as well as the conformational dynamics contributes significantly to the energy relaxation processes of linear porphyrin arrays. Consequently, long porphyrin arrays no longer serve as good energy transmission elements in donor-acceptor linked systems due to conformational heterogeneities which provide the non-radiative deactivation channels as energy quenchers. 相似文献
116.
Choi HC Bae SY Jang WS Park J Song HJ Shin HJ Jung H Ahn JP 《The journal of physical chemistry. B》2005,109(5):1683-1688
Nitrogen (N)-doped carbon nanotubes (CNTs) were heated to 1000 degrees C under an ultrahigh vacuum. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) reveal three different N structures; graphitelike, pyridine-like, and molecular N(2). The vibrationally resolved XANES peaks of N(2) were first observed, suggesting the existence of molecular N(2) as intercalated and trapped forms. The annealing process can decrease the average N content from 6.3 at. % to 3.3 at. %, mainly by releasing molecular N(2). Electron energy-loss spectroscopy (EELS) confirms that the annealing releases molecular N(2) from the CNTs. 相似文献
117.
The analysis of the interaction of threose 4-phosphate and 2-deoxyerythrose 4-phosphate with 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAH7PS) reveals previously unrecognised mechanistic differences between the DAH7PS-catalysed reaction and that catalysed by the closely related enzyme, 3-deoxy-D-manno-octulosonate 8-phosphate synthase (KDO8PS). 相似文献
118.
Abazov VM Abbott B Abolins M Acharya BS Adams M Adams T Agelou M Agram JL Ahn SH Ahsan M Alexeev GD Alkhazov G Alton A Alverson G Alves GA Anastasoaie M Andeen T Anderson S Andrieu B Arnoud Y Askew A Asman B Jesus AC Atramentov O Autermann C Avila C Badaud F Baden A Baldin B Balm PW Banerjee S Barberis E Bargassa P Baringer P Barnes C Barreto J Bartlett JF Bassler U Bauer D Bean A Beauceron S Begel M Bellavance A Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA 《Physical review letters》2005,95(5):051802
We present a measurement of the Zgamma production cross section and limits on anomalous ZZgamma and Zgammagamma couplings for form-factor scales of lambda = 750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eegamma (mumugamma) final state using 320(290) pb(-1) of pp(-1) collisions at square root of s = 1.96 TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are /h(10,30)Z/ < 0.23, /h(20,40)Z/ < 0.020, /h(10,30)gamma/ < 0.23, and /h(20,40)gamma/ < 0.019 for lambda = 1000 GeV. 相似文献
119.
Hyun-Soo Ahn Rhonda Righter J. George. Shanthikumar 《Mathematical Methods of Operations Research》2005,62(3):499-514
In this paper we consider a firm that employs heterogeneous workers to meet demand for its product or service. Workers differ
in their skills, speed, and/or quality, and they randomly leave, or turn over. Each period the firm must decide how many workers
of each type to hire or fire in order to meet randomly changing demand forecasts at minimal expense. When the number of workers
of each type can by continuously varied, the operational cost is jointly convex in the number of workers of each type, hiring
and firing costs are linear, and a random fraction of workers of each type leave in each period, the optimal policy has a
simple hire- up-to/fire-down-to structure. However, under the more realistic assumption that the number of workers of each
type is discrete, the optimal policy is much more difficult to characterize, and depends on the particular notion of discrete
convexity used for the cost function. We explore several different notions of discrete convexity and their impact on structural
results for the optimal policy. 相似文献
120.
Abazov VM Abbott B Abolins M Acharya BS Adams M Adams T Agelou M Agram JL Ahn SH Ahsan M Alexeev GD Alkhazov G Alton A Alverson G Alves GA Anastasoaie M Anderson S Andrieu B Arnoud Y Askew A Asman B Atramentov O Autermann C Avila C Badaud F Baden A Baldin B Balm PW Banerjee S Barberis E Bargassa P Baringer P Barnes C Barreto J Bartlett JF Bassler U Bauer D Bean A Beauceron S Begel M Bellavance A Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA Bhat PC Bhatnagar V 《Physical review letters》2005,94(10):102001
We present measurements of the Lambda(0)(b) lifetime in the exclusive decay channel Lambda(0)(b)--> J/psiLambda(0), with J/psi--> mu(+)mu(-) and Lambda(0)--> ppi(-), the B0 lifetime in the decay B0-->J/psiK(0)(S) with J/psi--> mu(+)mu(-) and K(0)(S)-->pi(+)pi(-), and the ratio of these lifetimes. The analysis is based on approximately 250 pb(-1) of data recorded with the D0 detector in pp collisions at sqrt[s] = 1.96 TeV. The Lambda(0)(b) lifetime is determined to be tau(Lambda(0)(b)) = 1.22(+0.22)(-0.18)(stat) +/- 0.04(syst) ps, the B0 lifetime tau(B0) = 1.40(+0.11)(-0.10)(stat) +/- 0.03(syst) ps, and the ratio tau(Lambda(0)(b))/tau(B0) = 0.87(+0.17)(-0.14)(stat) +/- 0.03(syst). In contrast with previous measurements using semileptonic decays, this is the first determination of the Lambda(0)(b) lifetime based on a fully reconstructed decay channel. 相似文献