全文获取类型
收费全文 | 784篇 |
免费 | 17篇 |
国内免费 | 5篇 |
专业分类
化学 | 511篇 |
晶体学 | 7篇 |
力学 | 37篇 |
数学 | 68篇 |
物理学 | 183篇 |
出版年
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 9篇 |
2013年 | 27篇 |
2012年 | 38篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 11篇 |
2008年 | 44篇 |
2007年 | 45篇 |
2006年 | 50篇 |
2005年 | 42篇 |
2004年 | 43篇 |
2003年 | 29篇 |
2002年 | 28篇 |
2001年 | 15篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 15篇 |
1997年 | 5篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 12篇 |
1976年 | 6篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1972年 | 6篇 |
1970年 | 5篇 |
1968年 | 10篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有806条查询结果,搜索用时 17 毫秒
151.
Treado T.A. Doggett W.O. Thomas G.E. Smith R.S. III Jackson-Ford J. Jenkins D.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(2):237-248
The operating characteristics of a relativistic 16-vane rising-sun magnetron were investigated with particular emphasis on determining the operating regimes of different modes. The magnetron performance was studied as a function of voltage, magnetic field, cathode geometry, axial boundary conditions, and output coupling. Operation was observed in the 3π/8 mode at 3.3 GHz, in the π/2 or 3π/8 mode at 3.5 GHz, and in the π or 7π/8 mode at 4.6 GHz. A maximum power of 80 MW was emitted in the 3π/8 mode with an efficiency of 4.5%. Typical pulse lengths were 40-50 ns. Cold tests were performed to measure the resonant frequencies and azimuthal electric fields in the interaction space which agreed within 1-4% of theoretical calculations. The operating modes were inferred from close agreement between hot-test frequencies and cold-test results and because high-power RF emission occurred at, or just above, the Buneman-Hartree threshold calculated for these modes. The characteristics of a six-vane A6-magnetron operating in the π and 2π modes were also studied. A unique transmitting-receiving system, which was used as a microwave diagnostic, is described 相似文献
152.
153.
154.
R. Wadsworth P. Regan S. M. Mullins G. J. Gyapong D. L. Watson P. J. Nolan M. J. Godfrey I. Jenkins Y. J. He B. J. Varley J. Simpso W. Gelletly 《Zeitschrift für Physik A Hadrons and Nuclei》1989,333(4):411-412
The states in the yrast band of132 Sm have been identified for the first time up to Jπ=16+. The yrast band of130Nd has also been extended from Jπ=16+ to 24+. The energy of the first 2+ state in132Sm indicates that the quadrupole deformation ε2 ~ 0.3 and is still increasing as the neutron number N decreases across the samarium isotopes. The results for130Nd allow the (h2/11)2 proton crossing frequency to be determined as ω=0.325 ± 0.005 MeV/?. This result is compared with cranked shell model predictions. 相似文献
155.
R. Wadsworth P. Regan S. M. Mullins G. J. Gyapong D. L. Watson P. J. Nolan M. J. Godfrey I. Jenkins Y. J. He B. J. Varley W. Gelletly J. Simpson 《Zeitschrift für Physik A Hadrons and Nuclei》1989,333(4):409-410
A rotational band of nine γ-rays has been observed in133Sm. The moment of inertia of the band indicates that it has a higher deformation than expected for states in nuclei in this region. The properties are such that it can be interpreted as being due to the odd neutron occupying the ν i2/13 nn intruder orbital. This is the first evidence for the occupation of this orbital in nuclei with neutron number N<73. 相似文献
156.
The novel complex trans-[PdCl2(η1-N-2-ethyl-2-oxazoline)2] is shown to be an active and oxidatively robust catalyst for C-C bond-forming reactions (Heck, Sonogashira, Ullman, Suzuki), which can be carried out in air without rigorous solvent/substrate purification and in the absence of additional free ligand. 相似文献
157.
158.
Antoniazzi L Arenton M Cao Z Chen T Conetti S Cox B Delchamps S Fortney L Guffey K Haire M Ioannou P Jenkins CM Judd DJ Kourkoumelis C Manousakis-Katsikakis A Kuzminski J LeCompte T Marchionni A He M Mazur PO Murphy CT Pramantiotis P Rameika R Resvanis LK Rosati M Rosen J Shen C Shen Q Simard A Smith RP Spiegel L Stairs DG Tan Y Tesarek RJ Turkington T Turnbull L Turkot F Tzamarias S Voulgaris G Wagoner DE Wang C Yang W Yao N Zhang N Zhang X Zioulas G Zou B 《Physical review D: Particles and fields》1992,46(11):4828-4835
159.
Geoffrey R. County Ron S. Dickson Susan M. Jenkins Julian Johnson Olga Paravagna 《Journal of organometallic chemistry》1997,530(1-2)
Treatment of (η5-C5H5)2Rh2(CO)η1-Ph2P(CH2)n PPh2(μ-η1:η1-CF3C2CF3) (I) with (η5-CH3C5H4)Mn(CO)2(thf) or Cr(CO)5(thf) gives the hetero-trinuclear products (η-C5H5)2Rh2(CO)(μ-CF3C2CF3)μ:η1:η1-Ph2P(CH2)nPPh2(η-CH3C5H3C4)Mn(CO2) (II, n = 1–4) and (η5-C5H5)2Rh2(CO)(μ-CF3C2CF3)μ:η1:η1-Ph2P(CH2)nPPh2Cr(CO)5 (IV, n = 1–4) in good yields. In these products, the configuration of the CO and bisphosphine units on the Rh-Rh bond is trans. Related reactions between (η5:η5-C5H4CH2C5H4)Rh2(CO)η1-Ph2P(CH2)nPPh2(μ-η1:η1- (V) and the same solvated manganese and chromium complexes give (η5:η5-C5H4CH2C5H4)Rh2(CO)(μ-CF3C2CF3)μ:η1:η1-Ph2P(CH2) (VI, n = 1, 2 or 4) and (η5:η5-C5H4CH2C5H4)Rh2(CO)(μ-CF3C2CF3)μ:η1:η1-Ph2P(CH2) (VIII). The complexes (VI) and (VIII) have a mutually cis arrangement of CO and the bisphosphine on the Rh-Rh bond. Attempts to induce the complexes (IV), (V), (VI), and (VIII) to form clusters by loss of CO and Rh-M bond formation were not successful. Treatment with trimethylamine oxide or sunlight irradiation generally resulted in loss of the hetero-metal and formation of the dirhodium phosphine oxide complexes (III, n = 2 or 4) and (VII, n = 2, 3). 相似文献
160.
Dr. Laurence R. Doyle Dr. Ashley J. Wooles Lucy C. Jenkins Dr. Floriana Tuna Prof. Eric J. L. McInnes Prof. Stephen T. Liddle 《Angewandte Chemie (International ed. in English)》2018,57(21):6314-6318
Catalytic reduction of N2 to NH3 by a Ti complex has been achieved, thus now adding an early d‐block metal to the small group of mid‐ and late‐d‐block metals (Mo, Fe, Ru, Os, Co) that catalytically produce NH3 by N2 reduction and protonolysis under homogeneous, abiological conditions. Reduction of [TiIV(TrenTMS)X] (X=Cl, 1A ; I, 1B ; TrenTMS=N(CH2CH2NSiMe3)3) with KC8 affords [TiIII(TrenTMS)] ( 2 ). Addition of N2 affords [{(TrenTMS)TiIII}2(μ‐η1:η1‐N2)] ( 3 ); further reduction with KC8 gives [{(TrenTMS)TiIV}2(μ‐η1:η1:η2:η2‐N2K2)] ( 4 ). Addition of benzo‐15‐crown‐5 ether (B15C5) to 4 affords [{(TrenTMS)TiIV}2(μ‐η1:η1‐N2)][K(B15C5)2]2 ( 5 ). Complexes 3 – 5 treated under N2 with KC8 and [R3PH][I], (the weakest H+ source yet used in N2 reduction) produce up to 18 equiv of NH3 with only trace N2H4. When only acid is present, N2H4 is the dominant product, suggesting successive protonation produces [{(TrenTMS)TiIV}2(μ‐η1:η1‐N2H4)][I]2, and that extruded N2H4 reacts further with [R3PH][I]/KC8 to form NH3. 相似文献