全文获取类型
收费全文 | 605篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 31篇 |
化学工业 | 169篇 |
金属工艺 | 13篇 |
机械仪表 | 41篇 |
建筑科学 | 15篇 |
能源动力 | 25篇 |
轻工业 | 52篇 |
水利工程 | 3篇 |
无线电 | 40篇 |
一般工业技术 | 124篇 |
冶金工业 | 23篇 |
原子能技术 | 11篇 |
自动化技术 | 73篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 33篇 |
2012年 | 27篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 49篇 |
2007年 | 48篇 |
2006年 | 31篇 |
2005年 | 28篇 |
2004年 | 14篇 |
2003年 | 22篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 16篇 |
1997年 | 5篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有620条查询结果,搜索用时 78 毫秒
11.
Carbon molecular sieve membranes for gas separation prepared using poly(phenylene oxide) (PPO) as precursor have been examined. The PPO precursor was modified by introducing a trimethylsilyl (TMS) substituent and its effect on the gas transport property of the resulting carbon membrane was examined. TMS-substituted PPO (TMSPPO) was prepared in a high yield by a simple one-step reaction, and its carbon membrane was successfully fabricated. The modification improved the gas permeability of the resulting membrane which also exhibited excellent O2/N2 and CO2/CH4 separation performance comparable to those of polyimide-derived carbon membranes. From the analysis of the microstructure of the TMSPPO carbon membranes, it is believed that the TMS groups improve gas diffusivity by increasing the micropore volume. 相似文献
12.
Ichiro Kudo Toshiyuki Kato Hidetoshi Hayashi Ryohei Yanoshita Koichi Ikizawa Hiroko Uda Keizo Inoue 《Lipids》1991,26(12):1065-1070
We have previously reported that platelet-activating factor (PAF) induces proliferation and microbicidal activity of guinea
pig bone marrow cells. In the present study, we have found that the conditioned medium of PAF- or nonmetabolizable PAF agonist-treated
guinea pig bone marrow cells augmented DNA synthesis and induced microbicial activity of bone marrow cells. A PAF specific
antagonist, CV-6209, inhibited generation of the active conditioned medium by PAF. Addition of the PAF antagonist only partially
suppressed the augmentative effect of the active conditioned medium on DNA synthesis; this is consistent with the fact that,
because of the rapid breakdown, no appreciable amount of PAF remained in the conditioned medium of PAF-treated cells. Although
mouse bone marrow cells did not respond to PAF unlike guinea pig cells, their DNA synthesis was significantly enhanced by
the conditioned medium of PAF-treated guinea pig bone marrow cells. Thus, some newly generated factor(s) distinct from the
originally inoculated PAF seemed to modulate the bioactions of PAF on bone marrow cells. An appreciable amount of PAF was
produced by calcium ionophore-treated guinea pig bone marrow cells. These findings indicate that PAF synthesized in guinea
pig bone marrow cells induces generation in the cells of some factor(s) which affects proliferation or microbicidal activity.
Presented at The Third International Conference on Platelet-Activating Factor and Structurally Related Ether Lipids, Tokyo,
Japan, May 1989. 相似文献
13.
Poly(ethylene phthalate) (PEP) and poly(ethylene phthalate–co‐ethylene terephthalate) were used to improve the brittleness of the cycloaliphatic epoxy resin 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexane carboxylate (Celoxide 2021?), cured with methyl hexahydrophthalic anhydride. The aromatic polyesters used were soluble in the epoxy resin without solvents and effective as modifiers for toughening the cured epoxy resin. For example, the inclusion of 20 wt % PEP (MW, 7400) led to a 130% increase in the fracture toughness (KIC) of the cured resin with no loss of mechanical and thermal properties. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 388–399, 2002; DOI 10.1002/app.10363 相似文献
14.
Komeiji Yuto; Uebayasi Masami; Someya Jun-ichiro; Yamato Ichiro 《Protein engineering, design & selection : PEDS》1992,5(8):759-767
The Ser88Cys mutant of the trp-repressor showed a lower affinityfor the corepressor than the wild-type repressor [G = 1.7 ±0.3 kcal/mol, Chou and Matthews (1989) J. Biol. Chem., 264,1831418319].A molecular dynamics/free energy cycle perturbation study wasperformed to understand the origin of the decreased affinity.A value (G = 1.58 ± 0.28 kcal/mol) comparable with theexperimental value was obtained by the simulation. Free energycomponent analysis revealed that destabilization of the vander Waals interaction between Ser88 and Trp109 (corepressor)mainly contributed to the decreased affinity of the mutant.The rotational transition of the hydroxyl (sulfhydryl) groupof Ser88 (Cys88) during the simulations affected the contributionsof Arg84 and water to the free energy change in the aporepressorand those of Arg84 and Trp 109 to that in the holorepressor.However, the contributions from different residues compensatedeach other, and the total free energy changes were almost invariablein the various simulations. 相似文献
15.
Viscoelastic properties of poly(isoprene-b-styrene) in dioctylphthalate under steady shear flow were measured near the order—disorder transition temperature. In ordered states, first normal stress difference N1 is proportional to shear rate
at low
region, but becomes proportional to
at the high
region, similar to the N1 behaviour of polymer blends undergoing shear-induced homogenization. Because the existence of microdomains was confirmed at the high
region by the flow birefringence method, it is concluded that the above N1 behaviour is not caused by shear-induced homogenization, but is probably caused by the shear-induced alignment of the microdomain structure. 相似文献
16.
Gopal P. Khanal Ichiro Fujii Shintaro Ueno Satoshi Wada 《Journal of the American Ceramic Society》2021,104(9):4649-4658
The <110>-oriented BaTiO3 ceramics were fabricated using BaCO3 matrix and H1.08Ti1.73O4.nH2O (HTO) template particles, and the mechanism of BaTiO3 phase formation was investigated. The dielectric, ferroelectric, and piezoelectric properties were also investigated. The transformation of the HTO phase into the TiO2 bronze or TiO2 (B) phase was observed at 600°C, where the BaTiO3 nucleation was accompanied by the formation of a Ba2TiO4 phase. The TiO2 phase reacted with the Ba2TiO4 phase at 800°C to give a BaTiO3 phase, whereas its reaction with the BaTiO3 resulted in the formation of BaTi2O5 phase that got decomposed into BaTiO3 and Ba6Ti17O40 phase at sintering temperature ≥1300°C. Sintering with samples’ embedding in BaTiO3 powders prevented the formation of the Ba6Ti17O40 secondary phase. The crystallographic orientation along the <110> direction (F110) was developed by the epitaxial grain growth mechanism. In addition to the contribution of the grain-size increment for enhancing the F110, the preservation of the platelike structure was also found to have a significant impact. The ceramics prepared by the embedded sintering (grain size ≈12.4 µm and F110 = 83%) exhibited the room-temperature dielectric constant of 1708 and piezoelectric strain constant of 445 pm/V, which are higher than those of the BaTiO3 ceramics with randomly oriented grains. 相似文献
17.
Sun-Chan Jeong Ichiro Katayama Hirokane Kawakami Yutaka Watanabe Hironobu Ishiyama Nobuaki Imai Yoshikazu Hirayama Hiroari Miyatake Masao Sataka Satoru Okayasu Hiroyuki Sugai Shin-Ichi Ichikawa Katsuhisa Nishio Shinichi Mitsuoka Takamitsu Nakanoya Masahito Yahagi Takanori Hashimoto Kazunori Takada Mamoru Watanabe Tomoko Ishikawa Akihiro Iwase 《Journal of Phase Equilibria and Diffusion》2005,26(5):472-476
For the effective use of short-lived radioactive beams, soon to be available at the Tokai Radioactive Ion Accelerator Complex, the authors have developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound βLiAl using an α-emitting radiotracer of 8Li (T1/2=0.84 s). It was found that the time-dependent yields of the α particles from the diffusing 8Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in βLiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects (i.e., the existence of the atomic vacancies of Li and the defects in Ga sites that are replaced by Li). 相似文献
18.
Ichiro Nakamori 《Computers & Fluids》2008,37(2):161-169
Hybridization comprised of an algebraic turbulence model based on the Reynolds average Navier-Stokes (RANS) equations with a monotonically integrated large eddy simulation (MILES) is proposed to simulate transient fluid motion during separation and vortex shedding at high Reynolds numbers. The proposed hybridization utilizes the Baldwin-Lomax model with the Degani-Schiff modification as the RANS model in the near-wall region and a MILES far from the wall. Although the hybridization is assumed to be a MILES with wall modeling, the transition line between the RANS and the MILES modes is determined by the turbulent intensity that is dominated by the large eddies in the grid-scale. This hybrid model is applied to the flows past three different types of airfoils (NACA633-018, NACA631-012 and NACA64A-006) near stall, at a chord Reynolds number of Re = 5.8 × 106. These airfoils are classified as trailing-edge-stall, leading-edge-stall and thin-airfoil-stall airfoils, respectively. The computed results are compared with wind tunnel experiments. The hybrid model successfully demonstrates accurate stall angle and surface pressure distribution predictions near the stall for each type of airfoil. The airfoil simulation results confirmed that the hybrid model provides a better prediction than the RANS model for unsteady turbulent flows with separation and vortex shedding simulations. 相似文献
19.
We propose a computationally efficient method for cross-validation of the Support Vector Regression (SVR) by generalizing the decremental algorithm of SVR. Incremental and decremental algorithm of Support Vector Machines (SVM) 2, 8, 9) efficiently update the trained SVM model when a single data point is added to or removed from the training set. The computational cost of leave-one-out cross-validation can be reduced using the decremental algorithm. However, when we perform leave-m-out cross-validation (m > 1), we have to repeatedly apply the decremental algorithm for each data point. In this paper, we extend the decremental algorithm of SVR8, 9) in such a way that several data points can be removed more efficiently. Experimental results indicate that the proposed approach can reduce the computational cost. In particular, we observed that the number of breakpoints, which is the main computational cost of the involved path-following, were reduced from \({\mathcal O}(m)\) to \({\mathcal O}(\sqrt{m})\). 相似文献
20.