全文获取类型
收费全文 | 1947篇 |
免费 | 105篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 34篇 |
综合类 | 2篇 |
化学工业 | 450篇 |
金属工艺 | 69篇 |
机械仪表 | 140篇 |
建筑科学 | 32篇 |
矿业工程 | 4篇 |
能源动力 | 85篇 |
轻工业 | 136篇 |
水利工程 | 12篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 290篇 |
一般工业技术 | 409篇 |
冶金工业 | 113篇 |
原子能技术 | 21篇 |
自动化技术 | 257篇 |
出版年
2024年 | 1篇 |
2023年 | 36篇 |
2022年 | 30篇 |
2021年 | 83篇 |
2020年 | 57篇 |
2019年 | 73篇 |
2018年 | 58篇 |
2017年 | 58篇 |
2016年 | 83篇 |
2015年 | 53篇 |
2014年 | 119篇 |
2013年 | 152篇 |
2012年 | 135篇 |
2011年 | 149篇 |
2010年 | 96篇 |
2009年 | 111篇 |
2008年 | 101篇 |
2007年 | 102篇 |
2006年 | 82篇 |
2005年 | 56篇 |
2004年 | 54篇 |
2003年 | 48篇 |
2002年 | 26篇 |
2001年 | 38篇 |
2000年 | 24篇 |
1999年 | 27篇 |
1998年 | 44篇 |
1997年 | 26篇 |
1996年 | 23篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1977年 | 7篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1964年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有2059条查询结果,搜索用时 343 毫秒
21.
Chi Nguyen Quynh Ho Minh Thi Tran Chung Chinh Doan Son Nghia Hoang Diem Hong Tran Long Thanh Le 《International journal of molecular sciences》2021,22(9)
Simulated microgravity (SMG) induced the changes in cell proliferation and cytoskeleton organization, which plays an important factor in various cellular processes. The inhibition in cell cycle progression has been considered to be one of the main causes of proliferation inhibition in cells under SMG, but their mechanisms are still not fully understood. This study aimed to evaluate the effects of SMG on the proliferative ability and cytoskeleton changes of Chang Liver Cells (CCL-13). CCL-13 cells were induced SMG by 3D clinostat for 72 h, while the control group were treated in normal gravity at the same time. The results showed that SMG reduced CCL-13 cell proliferation by an increase in the number of CCL-13 cells in G0/G1 phase. This cell cycle phase arrest of CCL-13 cells was due to a downregulation of cell cycle-related proteins, such as cyclin A1 and A2, cyclin D1, and cyclin-dependent kinase 6 (Cdk6). SMG-exposed CCL-13 cells also exhibited a downregulation of α-tubulin 3 and β-actin which induced the cytoskeleton reorganization. These results suggested that the inhibited proliferation of SMG-exposed CCL-13 cells could be associate with the attenuation of major cell cycle regulators and main cytoskeletal proteins. 相似文献
23.
Sergey Kucheiko Ji-Won Choi Hyun-Jai Kim Hyung-Jin Jung 《Journal of the American Ceramic Society》1996,79(10):2739-2743
The microwave dielectric properties of CaTi1-χ (Al1/2 Ta1/2 )cH O3 solid solutions (0.3 ≤χ≤ 0.5) have been investigated. The ceramic samples had perovskite structures similar to CaTiO3 . The partial substitution of Ti4+ by a coupled Al3+ /Tas+ permitted improvement of the quality factor Q . The dielectric constant (τr ) and temperature coefficient of resonant frequency (τr ) decrease rapidly with an increase of χ. A new high-quality microwave dielectric material was found at χ= 0.46 with σr = 46.5, Q f = 27300 GHz, and πf = 0 ppm/°C. The relationship between microstructures and dielectric properties is presented. 相似文献
24.
Oligomerization of glycine (gly) and diglycine (gly2) on montmorillonite was performed as cyclic, drying-wetting process at temperatures below 100°C, under varying reaction conditions. The influence of substrate/clay ratio, temperature and pH was found to be different for amino acid (AA) dimerization, cyclic anhydride (CA) formation and peptide chain elongation. High temperatures and neutral pH favour CA formation over diglycine production. An AA/catalyst ratio of 0.2 mmol/g leads to optimal yields. This supports the assumption that amino acid dimerization and CA formation take place at the edges of clay particles. Peptide chain elongation, starting from gly2, produces higher yields at higher temperatures and neutral pH. 相似文献
25.
Novel polypyrrole (PPy)/polydimethylsiloxane (PDMS) composite membrane was prepared by interfacial polymerization to make a very effective gas separation membrane. We found that Polymerized PPy films as thin as ~200 nm could be chemically synthesized as freestanding membranes by using the interfacial polymerization technique. Additionally, we show that difference morphology of PPys films was obtained by controlling polymerization rate and more dense films were formed at low polymerization rate. Wide X-ray diffraction study showed the d spacing value of the PPy film decreased from 4.89 å to 3.67 å by the rate of polymerization decreases. According to d spacing value decrease, selectivity of a PPy composite membrane was increased dramatically and permeability was reduced gradually. This high selectivity was derived from d spacing closed to the kinetic diameter of nitrogen. These results indicated that the permeability is controlled by the diffusion coefficient, reflecting the packed structure of the PPy film. The highest selectivity value of composite membrane that was prepared by interfacial polymerization was O2/N2=17.2 and permeability for O2 was 40.2 barrer. 相似文献
26.
Younggon Son Kalman B Migler 《Polymer》2002,43(10):3001-3006
This paper describes an improvement of the technique to measure interfacial tension in immiscible polymer blends. Our method is based on the droplet retraction method, in which one relates the kinetics of relaxation of a deformed droplet to the interfacial tension between the matrix and droplet. Previously, the problem with this technique has been the difficulty in preparing axisymmetric ellipsoidal droplets. In our work, we demonstrate that perfect axisymmetric ellipsoidal droplets are produced at a later stage of relaxation of short imbedded fibers. With this technique, we utilize the strengths of both the deformed droplet method and the imbedded fiber retraction method while overcoming their shortcomings. The interfacial tension value thus obtained was compared to that by conventional methods. Additionally, the effect of confinement by external walls on the interfacial tension measurement was studied. Confinement affects interfacial tension measurement when the gap between the walls is less than two times the equilibrium drop size. 相似文献
27.
Stormer-numerov approximation for numerical solutions of ordinary and partial differential equations
Stormer-Numerov approximations of high accuracy were developed for solutions of non-linear boundary value problems and nonlinear
elliptic partial differential equations. The approximations can be easily adopted also for parabolic partial differential
equations in one and more space dimensions and feature fourth-order accuracy. For boundary value problems only three nodes
are necessary to obtain the desired fourth order accuracy. The finite difference formula for parabolic partial differential
equations can be readily generalized to a nonequidistant mesh so that automatic regridding in space may be used. The Stomer-Numerov
approximations are important for solution of problems where storage limitations and computer time expenditure preclude standard
second order methods. Because of the fourth order approximations a low number of mesh points can be used for a majority of
chemical engineering problems. The application of Stormer-Numerov approximations is illustrated on a number of examples. 相似文献
28.
Eungsun Byon Myungsook Son Kee-Seok Nam Katsuhisa Sugimoto 《Electrochimica acta》2006,51(13):2662-2668
The electrochemical behavior of B1.0C2.4N1.0 thin film was investigated in acidic, neutral and alkaline solutions. The anodic polarization curve of the film in 1 M NaOH showed the anodic dissolution of the film. The curve of the film in 1 M HCl showed no anodic dissolution. The cathodic polarization curve in 1 M NaCl showed shift to a negative potential side, but the anodic polarization curve was the same as that of Pt. The anodic dissolution in 1 M NaOH depended on potentials, that is, no anodic dissolution was recognized in a potential range of −0.2 to 0.1 V but the dissolution rate increased with increasing potential in a range of 0.1-0.6 V. The anodic current density of the film is directly proportional to the dissolution rate at potentials higher than 0.1 V. The dissolution rate of the film was increased with increasing solution pH. 相似文献
29.
Joo-Young Lee Yota Yamamoto Riichi Oe Su-Young Son Hitoshi Wakabayashi Yutaka Tochihara 《Ergonomics》2014,57(8):1213-1221
The purpose of this study was to investigate the physiological and subjective responses of the European, Japanese (JPN) and US firefighters' helmet, gloves and boots for international standardisation. Three experimental conditions were evaluated (clothing mass: 9.4, 8.2 and 10.1 kg for the three conditions, respectively) at the air temperature of 32°C and 60% relative humidity. The results showed that there was no significant difference among the three conditions in oxygen consumption, heart rate, total sweat rate, rectal temperature and mean skin temperature, whereas peripheral temperatures and subjective perceptions were lower in the JPN condition than in the other conditions (P < 0.05). These results indicate that a 0.5-kg reduction in helmet mass and a 1.1-kg reduction in boot mass during exercise resulted in a significant decrease in head and leg temperatures and subjective perceptions, while a 1.9-kg reduction in total clothing mass had insignificant influences on the metabolic burden and overall body temperature. 相似文献
30.
Min-Jae Yoon Yoan-Sang Bae Sang-Ha Son Jae-Wook Lee Chang-Ha Lee 《Korean Journal of Chemical Engineering》2007,24(5):877-880
Luminescent yttrium aluminum garnet (YAG, Y3Al5O12) nanoparticles doped with Eu (10 at%) were synthesized in batch-type and continuous-type supercritical water (SCW) reactors.
In the case of the continuous-type SCW method, the particles of YAG: Eu phosphors were much smaller and demonstrated a uniform
spherical-like shape. Inversely, in the case of the batch-type SCW method, a needle-like or elliptical-like shape was formed
because a finite amount of time was required to reach SCW conditions from ambient conditions. However, the emission intensity
of YAG: Eu phosphors synthesized by using the batch-type SCW method was stronger. Therefore, it is concluded that the continuous-type
SCW method is superior to the batch-type SCW method from the viewpoint of the particle size and shape, but the luminescence
property of phosphors in the continuous-type SCW method needs to be improved. In addition, a calcination process slightly
improved the luminescence intensities of YAG: Eu phosphors generated by using either the batch-type or continuous-type SCW
methods. 相似文献