全文获取类型
收费全文 | 5970篇 |
免费 | 104篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 282篇 |
综合类 | 11篇 |
化学工业 | 1484篇 |
金属工艺 | 250篇 |
机械仪表 | 149篇 |
建筑科学 | 124篇 |
矿业工程 | 5篇 |
能源动力 | 200篇 |
轻工业 | 324篇 |
水利工程 | 19篇 |
石油天然气 | 4篇 |
无线电 | 547篇 |
一般工业技术 | 1182篇 |
冶金工业 | 934篇 |
原子能技术 | 174篇 |
自动化技术 | 408篇 |
出版年
2023年 | 24篇 |
2022年 | 62篇 |
2021年 | 86篇 |
2020年 | 33篇 |
2019年 | 56篇 |
2018年 | 74篇 |
2017年 | 67篇 |
2016年 | 81篇 |
2015年 | 66篇 |
2014年 | 111篇 |
2013年 | 272篇 |
2012年 | 182篇 |
2011年 | 316篇 |
2010年 | 225篇 |
2009年 | 257篇 |
2008年 | 291篇 |
2007年 | 204篇 |
2006年 | 205篇 |
2005年 | 187篇 |
2004年 | 164篇 |
2003年 | 197篇 |
2002年 | 165篇 |
2001年 | 118篇 |
2000年 | 119篇 |
1999年 | 114篇 |
1998年 | 400篇 |
1997年 | 257篇 |
1996年 | 230篇 |
1995年 | 137篇 |
1994年 | 121篇 |
1993年 | 135篇 |
1992年 | 72篇 |
1991年 | 65篇 |
1990年 | 64篇 |
1989年 | 89篇 |
1988年 | 75篇 |
1987年 | 73篇 |
1986年 | 77篇 |
1985年 | 74篇 |
1984年 | 82篇 |
1983年 | 76篇 |
1982年 | 59篇 |
1981年 | 50篇 |
1980年 | 53篇 |
1979年 | 40篇 |
1978年 | 33篇 |
1977年 | 36篇 |
1976年 | 43篇 |
1974年 | 17篇 |
1973年 | 14篇 |
排序方式: 共有6097条查询结果,搜索用时 15 毫秒
961.
Konishi T Yamashiro T Koide M Nishizono A 《Journal of Bioscience and Bioengineering》2006,101(6):478-484
Bacterial growth is influenced by several different culture conditions. Temperature is one of an essential component which regulates bacterial growth and their morphology. The influence of temperature on the length of bacteria was investigated in broth and on agar in a temperature range from 30.0 degrees C to 47.0 degrees C in 0.5 degrees C steps using a newly developed temperature gradient incubator. The incubator is able to reach a set temperature within 2 h and maintain temperature as accurate as +/-0.1 degrees C of the set temperature. Three Legionella pneumophila serotype 1 strains were incubated for 48 h in BCYE-alpha agar at various temperatures ranging from 30.0 degrees C to 48.0 degrees C and length of bacteria grown at each temperature was microscopically measured. Ability of bacteria to multiply at a given temperature was also determined. L. pneumophila serotype 1 strains ATCC 33152, a clinical isolate Okinawa 02-001 were going to elongate to longer than 100 mum when cultured higher than at 39.5 degrees C and at 41.5 degrees C, respectively. Each strain was unable to multiply when cultured higher than at 44.2 degrees C (ATCC 33152) or at 44.0 degrees C (Okinawa 02-001). Those data would provide insights for establishing regulations in terms of maintaining hot water temperature in a facility where a circulating hot water supply-system is available and contamination with Legionella spp. is likely to happen. 相似文献
962.
Kashii M Fujisawa R Adachi H Mori Y Sasaki T Koga Y Takano K Kanaya S Matsumura H Inoue T Murakami S Sugamoto K Yoshikawa H 《Journal of Bioscience and Bioengineering》2006,102(4):372-374
We developed a novel technique for detaching protein crystals from glass capillary tube using the counter diffusion crystallization technique by femtosecond laser irradiation. X-ray diffraction analysis demonstrated that femtosecond laser irradiation has little effect on crystallinity. This technique will contribute to progress in structural genomics as a powerful tool. 相似文献
963.
964.
965.
A specimen heating holder equipped with a gas injector and an evaporator has been developed for use with conventional transmission electron microscopes (TEMs). The developed specimen holder allows both synthesis of metal oxide support and deposition of catalyst nano-particles in situ. Since the holder is designed to be used in small gapped high-resolution objective lens pole-piece, all the procedure from the synthesis of support material to the deposition of catalyst as well as the behavior of the catalyst nano-particles on the support can be observed at near atomic resolution. The developed specimen holder was applied to the study of AuPd catalyst. First, air was injected onto heated aluminum particles via a gas injector to synthesize Al(2)O(3) support. Then, nano-particles of AuPd were deposited on the Al(2)O(3) support. After the deposition, the synthesized Al(2)O(3) support was heated and air was injected again to observe behaviors of the deposited AuPd nano-particles at elevated temperatures in the aerial environment. Behaviors of the AuPd nano-particles such as coalescence, segmentation and diffusion to the Al(2)O(3) support were dynamically observed at atomic level high resolution. 相似文献
966.
Masanori Seki Masahiro Fujii Yuji Kobayashi Masaaki Sato Akira Yoshida 《Journal of Mechanical Science and Technology》2010,24(1):141-144
To investigate the influence of shot peening on the surface durability of powder-forged rollers, the case-hardened powder-forged
rollers with a forging density of 7.5 g/cm3 treated by the single shot peening and the double shot peening were fatigue-tested under a sliding-rolling contact condition.
The surface roughness, the surface hardness and the surface compressive residual stress of the rollers were increased by the
shot peening. In addition, the pores near the roller surface were deformed by the shot peening. The failure mode of all the
test rollers was spalling due to subsurface cracking. The fatigue lives of all the test rollers were improved by the shot
peening, and that of the test roller S08, which was shot-peened with the hardest steel shots in this experimental range, was
especially improved. The surface durability of the test roller S08 was also most improved by the shot peening. Cracks became
difficult to occur and propagate under the roller surface since the pores near the roller surface were deformed by the stronger
shot peening. In this study, double shot peening, which generally restrains the increase in surface roughness, was not particularly
effective for the improvement in the surface durability of the powder-forged rollers, because the influence of tangential
force on fatigue was not always great in a case of subsurface cracking. 相似文献
967.
A method for fabricating epoxy resin films dispersing the surface‐modified barium titanate (BT) particles (BT‐epoxy resin composite films) are proposed. BT particles with a size of 7.8 nm and a crystal size of 8.6 nm were synthesized with a complex alkoxide method. To introduce epoxy groups on the BT particle surface, the BT particles were surface‐modified with 2‐(3,4‐epoxycyclohexyl)‐ethyltrimethoxysilane. A precursor solution, which was prepared by prereacting 2,2‐bis(4‐glycidyloxyphenyl)propane (BGPP) and phthalic anhydride in 4‐butyrolactone and adding the surface‐modified BT particles to the prereacting solution, was spin‐coated on glass substrates to fabricate the composite films. An increase in BT volume fraction in film increased dielectric constant of the composite film while keeping dissipation factor below 0.03. The dielectric constant attained 10.8 at a BT volume fraction of 30% in film that was around twice higher than pure epoxy resin film. POLYM. COMPOS., 31:1179–1183, 2010. © 2009 Society of Plastics Engineers 相似文献
968.
Gazy F. Al-Sumaily Akira Nakayama John Sheridan Mark C. Thompson 《International Journal of Heat and Mass Transfer》2012,55(13-14):3366-3378
A detail numerical analysis of the effect of particle diameter of a packed bed of spherical particles on forced convection about an embedded circular cylinder is presented. This parametric study focusses on the two-phase energy (LTNE—local thermal non-equilibrium) model, which does not assume local thermal equilibrium (LTE) between the solid medium and the fluid. The investigation is performed for a cylinder-to-particle diameter ratio Dcy/dp = 10–100, at a wide ranges of Reynolds number ReD = 1–250 and solid-to-fluid thermal conductivity ratio kr = 0.01–1000. A comparison of predictions from the LTNE and LTE energy models is also made. This paper quantifies the influence of the key non-dimensional parameters on the heat transfer rate. It is also shown that although the presence of the porous materials around the heated cylinder enhances the overall heat transfer and increases the pressure drop in the bed compared to an empty channel, using a porous medium with large particle diameters increases considerably this enhancement in heat transfer and decreases significantly the unfavorable pressure drop. 相似文献
969.
Isao Saeki Yusuke Sugiyama Shigenari Hayashi Akira Yamauchi Takashi Doi Yoshitaka Nishiyama Shoji Kyo Shigeru Suzuki Masugu Sato Shinji Fujimoto 《Corrosion Science》2012
Changes in the crystal structure of type 430 stainless steel and the oxides on its surface were studied in situ at 1373 K using a high-intensity synchrotron X-ray source provided by SPring-8 in Japan. The surface of the steel was initially covered with Cr2O3, which was then converted to FeCr2O4, and finally Fe3O4 and Fe2O3 formed on it. These results indicated that the reason for the breakaway oxidation in type 430 stainless steel is Cr depletion beneath Cr2O3 layer and the subsequent ionisation of Fe, not the simple mechanical failure of Cr2O3. 相似文献
970.
Makoto Sugiyama Yutaka FujimotoTakayuki Yanagida Daisuke Totsuka Shunsuke KurosawaYoshisuke Futami Yuui YokotaValery Chani Akira Yoshikawa 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2012,664(1):127-131
Er-doped Lu3Al5O12 (Er:LuAG) single crystalline scintillators with different Er concentrations of 0.1, 0.5, 1, and 3% were grown by the micro-pulling-down (μ-PD) method. The grown crystals were composed of single-phase material, as demonstrated by powder X-ray diffraction (XRD). The radioluminescence spectra measured under 241Am α-ray excitation indicated host emission at approximately 350 nm and Er3+ 4f-4f emissions. According to the pulse height spectra recorded under γ-ray irradiation, the 0.5% Er:LuAG exhibited the highest peak channel among the samples. The γ-ray excited decay time profiles were well fitted by the two-component exponential approximation (0.8 μs and 6-10 μs). 相似文献