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991.
邻硝基苯基荧光酮-吐温80吸光光度法测定钢铁中微量钼 总被引:4,自引:1,他引:3
研究了Mo(Ⅵ)-(o-NPF)-Tween 80的尤度分析条件,在0.1m01·L-1硫酸介质中,配合物组成为Mo(Ⅵ)(o-NPF)=12,λmax=528nm,ε表现=1. 4×105,0~20μg/25m1符合比耳定律。体系允许较大量氟离子存在,可消除一定量Ti(Ⅵ)、Nb(Ⅴ)、zr(Ⅳ)、Sn(Ⅳ)、Sb(Ⅱ)等离予的严重干扰影响。可直接测定钢铁中微量钼,操作简便,结果满意。 相似文献
992.
Der‐Jang Liaw Ching‐Cheng Huang Chun‐Wei Fu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(15):4428-4434
A novel organosoluble polynorbornene bearing a polar, pendant, ester‐bridged epoxy group [poly(oxiran‐2‐ylmethyl 2‐methylbicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate) (polyOMMC)] was prepared via the living ring‐opening metathesis polymerization (ROMP) of active norbornenes with a Ru catalyst. PolyOMMC exhibited excellent solubility in a variety of solvents. The number‐average molecular weight of polyOMMC linearly increased with the [M]/[I] ratio (where [M] is the monomer concentration and [I] is the initiator concentration), and a narrow polydispersity of 1.09–1.19 was observed; this was considered a living polymerization. When ROMP of oxiran‐2‐ylmethyl 2‐methylbicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate with [M]/[I] = 350 was carried out at 30 °C in CH2Cl2, the number‐average molecular weight (7.01 × 104; polydispersity index = 1.07) was close to the calculated molecular weight (7.28 × 104), and a diblock copolymer was observed after the addition of another monomer ([M]/[I] = 350) with an increase in the number‐average molecular weight (1.60 × 105; polydispersity index = 1.11), which was close to the calculated molecular weight (1.61 × 105). The modified polynorbornenes retained good solubility in methylene chloride, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, N,N‐dimethylacetamide, and N‐methyl‐2‐pyrrdione. High‐performance polynorbornenes with active epoxy groups could be designed with great potential for applications in photoresists, UV curing, and elastomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4428–4434, 2006 相似文献
993.
Ga‐Young Lee Han‐Na Jang Ju‐Yeon Lee 《Journal of polymer science. Part A, Polymer chemistry》2008,46(9):3078-3087
2,4‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐1‐(2,2‐dicyanovinyl)benzene dianhydride (4) was prepared and reacted with 4,4′‐oxydianiline, 4,4′‐diaminobenzanilide and 4,4′‐(hexafluoroisopropylidene)dianiline to yield novel Y‐type polyimides 5‐7 containing 2,4‐dioxybenzylidenemalononitrile groups as nonlinear optical (NLO) chromophores, which constitute parts of the polymer backbone. The resulting polyimides 5‐7 are soluble in polar solvents such as dimethylsulfoxide and N,N‐dimethylformamide. Polymers 5‐7 showed a thermal stability up to 330 °C in thermogravimetric analysis thermograms with Tg values obtained from differential scanning calorimetry thermograms in the range 179–194 °C. The second harmonic generation (SHG) coefficients (d33) of poled polymer films at the 1064 nm fundamental wavelength were around 5.56 × 10?9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 20 °C higher than the glass‐transition temperature there was no SHG decay below 215 °C because of the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3078–3087, 2008 相似文献
994.
Byong Sun Chun Jae Youn Hwang Jang Roh Rhee Taewan Kim Shin Saito Satoru Yoshimura Masakiyo Tsunoda Migaku Takahashi Young Keun Kim 《Journal of magnetism and magnetic materials》2006
Magnetic tunnel junctions (MTJs) comprising amorphous Co70.5Fe4.5Si15B10, possessing low saturation magnetization of 560 emu/cm3, as a free layer have been investigated. The switching behaviours were confirmed for the micrometer-sized elements experimentally, using the scanning magneto-optical Kerr effect (scanning MOKE). A micromagnetic modelling study was also carried out for the submicrometer-sized elements. By using either a CoFeSiB single or a synthetic antiferromagnetic free-layer structure, the magnetization switching field became much lower than conventionally used CoFe free layered MTJs. 相似文献
995.
Hyun-Jun Ha Sun-Shin Jung Zan-Zhi Huang Dong-Ho Jang Gun-Sik Park Jin-Gyu Song Gong-Man Park Hyee-Jea Kang 《International Journal of Infrared and Millimeter Waves》1999,20(12):2099-2106
Ku-band (14-14.5 GHz) folded waveguide TWT operated at the beam voltage and current of 6 kV and 0.1 A, respectively, has been studied experimentally. The RF circuit is designed by using a linear theory [1] and its predicted gain for a single stage is 20 dB. The cold test of the assembled RF circuit shows a good agreement with the theoretical prediction [2]. 相似文献
996.
In this paper, an extended sliding mode controller is applied to control a hyperchaotic motion in Rössler system. The sliding surface of this paper used is one dimension higher than traditional sliding surface and guarantees it passing through the activated initial states of controlled system. Therefore, using the characteristic of this sliding mode to design a controller not only can meet the desired specification but also without chattering phenomenon and abrupt state change. By comparing with the result in the existed literatures, the results show that the proposed controller can steer Rössler system to the desired state accurately. It also provides a good characteristic for disturbance rejection. 相似文献
997.
Jae‐Pil Kim Jae‐Wook Kang Jang‐Joo Kim Jae‐Suk Lee 《Journal of polymer science. Part A, Polymer chemistry》2003,41(10):1497-1503
Fluorinated dihydroxy phosphine oxide monomers were synthesized via chlorination, Grignard, and demethylation techniques. The prepared monomer was successfully polymerized with each of the three perfluorinated monomers (decafluorobiphenyl, decafluorobenzophenone, and pentafluorophenylsulfide) by nucleophilic aromatic substitution. The average molecular weight ranged between 7800 and 14,900 g/mol. The glass‐transition temperatures of the polymers were registered in the range of 185–235 °C, and all the polymers exhibited high thermal stability up to 326–408 °C. The results of the refractive‐index measurements indicated control of the refractive index between 1.5181 and 1.5536 and an optical loss of 0.53 dB/cm at 1550 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1497–1503, 2003 相似文献
998.
Myoungsouk Jang James V. Crivello 《Journal of polymer science. Part A, Polymer chemistry》2003,41(19):3056-3073
A series of difunctional silicon‐containing monomers were prepared with a novel method consisting of the monohydrosilation of an α,ω‐difunctional Si? H‐terminated siloxane with a vinyl‐functional epoxide or oxetane followed by the dehydrodimerization of the resulting Si? H‐functional intermediate. This method used simple, readily available starting materials and could be conducted as a streamlined one‐pot, two‐step synthesis. This novel method was also applied to the synthesis of several epoxy–silicone oligomers. The reactivities of these new monomers and oligomers were examined with Fourier transform real‐time infrared spectroscopy and optical pyrometry. Those monomers containing epoxycyclohexyl groups displayed excellent reactivity in cationic ring‐opening polymerization in the presence of lipophilic onium salt photoinitiators. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3056–3073, 2003 相似文献
999.
We demonstrate the transmission of directly modulated 10-Gb/s WDM signals over 320 km of negative dispersion fiber (dispersion:-2.5 ps/km/nm @1550 nm) without dispersion compensation. The results indicate that a regional metro WDM network could be implemented cost-effectively by using the proposed negative dispersion fiber and direct modulated lasers. 相似文献
1000.
Ignac Capek Der‐Jang Liaw Ching‐Cheng Huang 《Journal of Polymer Science.Polymer Physics》2003,41(6):571-581
The extent of intra‐ and interchain associations of (un)charged water‐soluble monomers in the homogeneous and micellar solutions was studied with steady‐state fluorescence spectroscopy. Fluorescence spectroscopic experiments were performed on uncharged (acryl amide) and charged hydrophilic monomers [zwitterionic 3‐dimethyl(methacryloyloxyethyl)ammonium propane sulfonate (DMAPS), etc.] with pyrene as a probe. In both the homogeneous and micellar solutions, linear Stern–Volmer plots were obtained that implied that the quenching process can be considered as totally dynamic. The Stern–Volmer constant (KSV) for DMAPS decreased with an increasing dielectric constant of solvent and the concentration of simple electrolyte. An abrupt decrease in KSV was observed in the presence of a small amount of anionic emulsifier [below the critical micelle concentration (cmc)]. The dependence of KSV on pH for DMAPS was described by a curve with a maximum at about pH = 7. This was interpreted in terms of segregation of DMAPS and the variation of a optimal microenvironment for the probe and quencher with pH. The quenching rate in the micellar solutions strongly increased above the cmc but was lower than that in the homogeneous solutions. In the micellar solutions (above the cmc), the microenvironment for an interaction between the probe and quencher was suggested to be the whole microdroplet. The dependence of KSV on pH for DMAPS is described by a curve with a maximum at about pH = 9.3. The synergistic effect arises from the segregation of charged quencher molecules within the microdroplets. The complex (or strong interaction) between quencher and additive(s) is supposed to increase the dynamic nature of microdroplets that provides an optimal microenvironment for probe and quencher. A good coemulsifier, however, removes quencher from the interface and creates a barrier for entering monomer (quencher) into the core of micelles; therefore, quenching is depressed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 571–581, 2003 相似文献