全文获取类型
收费全文 | 1042篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 568篇 |
晶体学 | 19篇 |
力学 | 35篇 |
数学 | 52篇 |
物理学 | 299篇 |
无线电 | 88篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 23篇 |
2017年 | 15篇 |
2016年 | 32篇 |
2015年 | 16篇 |
2014年 | 34篇 |
2013年 | 54篇 |
2012年 | 64篇 |
2011年 | 77篇 |
2010年 | 54篇 |
2009年 | 55篇 |
2008年 | 71篇 |
2007年 | 77篇 |
2006年 | 57篇 |
2005年 | 47篇 |
2004年 | 33篇 |
2003年 | 36篇 |
2002年 | 27篇 |
2001年 | 16篇 |
2000年 | 19篇 |
1999年 | 15篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1918年 | 2篇 |
排序方式: 共有1061条查询结果,搜索用时 10 毫秒
971.
Adams J Adler C Aggarwal MM Ahammed Z Amonett J Anderson BD Anderson M Arkhipkin D Averichev GS Badyal SK Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellwied R Berger J Bezverkhny BI Bhardwaj S Bhaskar P Bhati AK Bichsel H Billmeier A Bland LC Blyth CO Bonner BE Botje M Boucham A Brandin A Bravar A Cadman RV Cai XZ Caines H Calderón de la Barca Sánchez M Carroll J Castillo J Castro M Cebra D Chaloupka P Chattopadhyay S Chen HF Chen Y Chernenko SP Cherney M Chikanian A Choi B 《Physical review letters》2003,91(7):072304
We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au collisions at sqrt[s(NN)]=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions. 相似文献
972.
973.
J. W. Kooi J. A. Stern G. Chattopadhyay H. G. LeDuc B. Bumble J. Zmuidzinas 《International Journal of Infrared and Millimeter Waves》1998,19(3):373-383
Recent results at 1 THz using normal-metal tuning circuits have shown that SIS mixers can work well up to twice the gap frequency of the junction material (niobium). However, the performance at 1 THz is limited by the substantial loss in the normal metal films. For better performance superconducting films with a higher gap frequency than niobium and with low RF loss are needed. Niobium nitride has long been considered a good candidate material, but typical NbN films suffer from high RF loss. To circumvent this problem we are currently investigating the RF loss in NbTiN films, a 15K Tc compound superconductor, by incorporating them into quasi-optical slot antenna SIS devices. 相似文献
974.
We discuss the capabilities of STAR in exploring the physics at highp
T in ultrarelativistic heavy-ion colisions from RHIC at √s
NN = 130 GeV Preliminary results show that the spectra of negatively charged particles get suppressed at largerp
T in comparison top-p data. A strong azimuthal anisotropy observed at large transverse momentum region. A preliminary ratio -p/p has been measured by STAR-RICH detector. Some ongoing studies and future plans are discussed. 相似文献
975.
976.
Surfactants from either polyisobutylene or alkylsuccinic anhydrides derivatized with diethanolamine in a 1:1 molar ratio with hydrocarbon and polyisobutylene chains of similar length formed lamellar liquid crystals in situ and also with added water. The repeat distance between layers was determined using low angle X-ray diffraction (LAXD), and the water penetration into the hydrocarbon space in the lamellar structure was calculated.
The results revealed a significantly increased repeat distance for the polyisobutylene chain surfactants compared to the alkyl analogues. The water penetration was significantly greater for a surfactant with a decyl chain compared to the one with a dodecyl chain and was intermediate for the polyisobutylene based surfactant. 相似文献
The results revealed a significantly increased repeat distance for the polyisobutylene chain surfactants compared to the alkyl analogues. The water penetration was significantly greater for a surfactant with a decyl chain compared to the one with a dodecyl chain and was intermediate for the polyisobutylene based surfactant. 相似文献
977.
Silicon-incorporated diamond-like carbon (Si-DLC) films were deposited via dc plasma-enhanced chemical vapor deposition (PECVD), on glass and alumina substrates at a substrate temperature 300 °C. The precursor gas used was acetylene and for Si incorporation, tetraethyl orthosilicate dissolved in methanol was used. Si atomic percentage in the films was varied from 0% to 19.3% as measured from energy-dispersive X-ray analysis (EDX). The binding energies of C 1s, Si 2s and Si 2p were determined from X-ray photoelectron spectroscopic studies. We have observed low-macroscopic field electron emission from Si-DLC thin films deposited on glass substrates. The emission properties have been studied for a fixed anode-sample separation of 80 μm for different Si atomic percentages in the films. The turn-on field was also found to vary from 16.19 to 3.61 V/μm for a fixed anode-sample separation of 80 μm with a variation of silicon atomic percentage in the films 0% to 19.3%. The turn-on field and approximate work function are calculated and we have tried to explain the emission mechanism there from. It was found that the turn-on field and effective emission barrier were reduced by Si incorporation than undoped DLC. 相似文献
978.
Milan Maji Mossaraf Hossain Madhumita Chatterjee Shyamal Kumar Chattopadhyay Vedavati G. Puranik Pinak Chakrabarti Saktiprosad Ghosh 《Polyhedron》1999,18(27):1436-3739
Reaction of Ru(PPh3)2Br2 with the NNS chelating tridentate ligand 2-pyridyl-N-(2′-methylthiophenyl)methyleneimine (L) led to the isolation of the ruthenium(II) complex [Ru(L)(PPh3)Br2]. Reactivity of this complex with different bidentate chelating ligands revealed that the products are quite different from those obtained by reacting Ru(L)(PPh3)Cl2 (the corresponding cis dichloro complex) with the same ligands under comparable conditions. The mixed chelates were isolated and characterised by elemental analysis, magnetic moment measurement and by different spectroscopic methods along with their precursor. Electrochemistry of the complexes was examined by cyclic voltammetry using a platinum working electrode and a Ag/AgCl electrode as reference. The crystal structure of [Ru(L)(PPh3)Br2] disclosed that, unlike Ru(L)(PPh3)Cl2, the two bromo ligands are in trans position and this explained the difference in its reactivity pattern from the corresponding chloro complex. 相似文献
979.
K.M. Abdul Malik Samiran Mitra Raj Kumar Bhubon Singh 《Journal of chemical crystallography》1999,29(8):877-883
Complexes [Co(tren)(Tsal)]ClO4·H2O 1 and [Ni(pn)(py)2(NCS)2] 2, (tren = tris(2-aminoethyl)amine, Tsal = thiosalicylate ion, pn = 1, 2-diamino propane and py = pyridine) have been synthesized and structurally characterized. Both complexes crystallize in the monoclinic space group C2/c with a = 21.3340(6), b = 11.7754(2), c = 14.8076(5) Å, = 100.3831(10)°, Z = 8 (1), and a = 7.2573(8), b = 17.8810(11), c = 15.2681(12) Å, = 101.170(2)°, Z = 4 (2). The metal atoms in both cases have distorted octahedral geometry. In 1, the tren ligand is quadridentate and Tsal is bidentate chelate. In 2, the pn ligand forms a bidentate chelate with the NCS ligands in trans positions. Complex 1 is diamagnetic whereas 2 shows paramagnetism with a magnetic moment of 3.10 B. M. 相似文献
980.
S. Chattopadhyay S.K. Neogi A. Sarkar M.D. Mukadam S.M. Yusuf A. Banerjee S. Bandyopadhyay 《Journal of magnetism and magnetic materials》2011,323(3-4):363-368
Single phase Mn doped (2 at%) ZnO samples have been synthesized by the solid-state reaction technique. Before the final sintering at 500 °C, the mixed powders have been milled for different milling periods (6, 24, 48 and 96 h). The grain sizes of the samples are very close to each other (~32±4 nm). However, the defective state of the samples is different from each other as manifested from the variation of magnetic properties and electrical resistivity with milling time. All the samples have been found to be ferromagnetic with clear hysteresis loops at room temperature. The maximum value for saturation magnetization (0.11 μB/Mn atom) was achieved for 96 h milled sample. Electrical resistivity has been found to increase with increase in milling time. The most resistive sample bears the largest saturation magnetization. Variation of average positron lifetime with milling time bears a close similarity with that of the saturation magnetization. This indicates the key role played by open volume vacancy defects, presumably zinc vacancies near grain surfaces, in inducing ferromagnetic order in Mn doped ZnO. To attain optimum defect configuration favorable for ferromagnetism in this kind of samples proper choice of milling period and annealing conditions is required. 相似文献