全文获取类型
收费全文 | 997篇 |
免费 | 42篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 77篇 |
综合类 | 2篇 |
化学工业 | 266篇 |
金属工艺 | 34篇 |
机械仪表 | 32篇 |
建筑科学 | 14篇 |
能源动力 | 56篇 |
轻工业 | 48篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 63篇 |
一般工业技术 | 211篇 |
冶金工业 | 89篇 |
原子能技术 | 37篇 |
自动化技术 | 108篇 |
出版年
2023年 | 10篇 |
2022年 | 9篇 |
2021年 | 28篇 |
2020年 | 9篇 |
2019年 | 17篇 |
2018年 | 13篇 |
2017年 | 27篇 |
2016年 | 27篇 |
2015年 | 18篇 |
2014年 | 40篇 |
2013年 | 66篇 |
2012年 | 42篇 |
2011年 | 78篇 |
2010年 | 59篇 |
2009年 | 53篇 |
2008年 | 57篇 |
2007年 | 53篇 |
2006年 | 32篇 |
2005年 | 34篇 |
2004年 | 30篇 |
2003年 | 42篇 |
2002年 | 25篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 17篇 |
1998年 | 44篇 |
1997年 | 23篇 |
1996年 | 17篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 14篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有1042条查询结果,搜索用时 156 毫秒
51.
Shiplu Roy Chowdhury Yuichi Muneyuki Yasunori Takezawa Masahiro Kino-oka Atsuhiro Saito Yoshiki Sawa Masahito Taya 《Journal of Bioscience and Bioengineering》2010,109(3):310-313
The transitional behaviors of myoblasts toward differentiation were investigated in the cultures at the low and high seeding densities (respectively, X0 = 1.0 × 103 and 2.0 × 105 cells/cm2). In the culture at the low seeding density, an increase in confluence degree accompanied a decrease in growth potential (Rp), being Rp = 0.85 and 0.11 at t = 48 and 672 h, respectively. Myoblasts seeded at the high density resulted in the immediate cessation of growth with keeping the low range of Rp = 0.02–0.09 throughout the culture. The reduction of Rp led to the generation of three subpopulations of cells in proliferative, quiescent and differentiated states. Close cell contacts in the confluent state of high seeding culture induced cell quiescence to a higher extent with suppressing differentiation. 相似文献
52.
T. Katsumi H. Kodama T. Matsuo H. Ogawa N. Tsuboi K. Hori 《Combustion, Explosion, and Shock Waves》2009,45(4):442-453
A new composition of hydroxylammonium nitrate based solution containing ammonium nitrate, methanol, and water was developed
for monopropellant in a reaction control system (RCS) as an alternative to conventional hydrazine. In comparison with hydrazine,
this solution has a 20% higher specific impulse, 1.4 times higher density, and lower freezing point and toxicity. The linear
burning rate of the solution is moderate at the operating pressures of RCS thrusters. It was found that the linear burning
rate had some characteristics whose mechanisms had not been understood. The combustion mechanism of this solution was investigated.
The burning behavior was observed using a medium speed camera, and a temperature profile for the combustion wave was measured
with a 2.5 μm diameter thermocouple. From these results, the instability of the liquid-gas interface may trigger a sudden
increase in the burning rate, and methanol was found to be effective in reducing the bubble growth rate in the solution. The
reactivity of several catalysts was evaluated in an open-cup test, and the S405 catalyst for hydrazine showed the best performance
among them. Thruster tests were conducted using the S405 catalyst with variation in the propellant mass flow rate, catalyst
bed configuration, and length-to-diameter ratio of the combustor. As a result, parameters were determined that ensured long
operating time. The model thruster operated stably for up to 100 sec with a specific impulse I
sp = 240 sec, which corresponds to a 90% efficiency.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 4, pp. 109–120, July–August, 2009.
An erratum to this article can be found at 相似文献
53.
Koga Y Kobayashi K Yang J Nakano H Yamane T 《Journal of Bioscience and Bioengineering》2002,94(1):84-86
A mutant library of Burkholderia cepacia lipase KWI-56 was constructed on microplates by a cell-free process and tested with a chromogenic assay. This high-throughput construction system can be used to screen mutant proteins based on their catalytic activity. 相似文献
54.
The decreased availability of economic resources requires the use of methods to assess hospital efficiency. The aim of our study was to retrospectively evaluate the applicability to the Italian reality of a catalogue of medical acts (CdAM-champs beta) set up for the French Health System. We wanted to evaluate the amount of resource utilization of a Cardiothoracic Operating Room of a IRCCS regional general hospital. The study included 83 admissions, occurring in October 1996, to the cardiac surgery department. Medical acts were recorded for all admissions taking into account both the number of acts and the weight of acts expressed as standard cost index or ICR. This takes into account the use of human (medical and nursing staff) and technical resources. Calculation of ICR beta scores was achieved by means of two different expressions. We observed a lack of correlation between the two values of each ICR. The previous formula (1991) gives more emphasis on the different conditions in which the operation was carried out (American Society of Anesthesiology score), duration of anesthesia and patients disease with a statistical significant difference. The last formula (1995) only evaluate patients' disease. None of the two formula of ICR beta turns out to be completely appropriate index of resource utilization during anesthesia; therefore this analysis still remains a difficult problem. Yet it must be recognized that this system deserves the merit of having evaluated the anesthesiological duties, by separating them from the surgical ones. 相似文献
55.
56.
Ribotyping and a study of transmission of Staphylococcus aureus collected from food preparation facilities 总被引:1,自引:0,他引:1
Kishimoto M Hioki Y Okano T Konuma H Takamizawa K Kashio H Kasuga F 《Journal of food protection》2004,67(6):1116-1122
Food poisoning from Staphylococcus aureus is sometimes caused by improper handling of food items in food preparation facilities. Prevention of contamination by employees is particularly important in facilities where a significant amount of food preparation is performed by hand. Some experiments have been performed to describe bacterial cross-contamination in the food preparation process, but there have been few studies of cross-contamination in actual food preparation facilities. Aiming to shed light on the transmission of S. aureus in food preparation facilities, this study collected samples of 66 strains of this bacterium from the fingers of food preparation staff, foodstuffs, prepared foods, cooking utensils, and cooking equipment and typed them with the ribotyping method. S. aureus from the same ribogroup was detected on the hands of a study participant, a faucet, knife, frying pan, and a salad, indicating that bacteria found on the hands of the study participant was transmitted to cooking utensils and prepared foods. Transmission (from a faucet to a frying pan handle) of bacteria by another person, a third party, was also detected. 相似文献
57.
Kamino T Yaguchi T Kuroda Y Ohnishi T Ishitani T Miyahara Y Horita Z 《Journal of electron microscopy》2004,53(5):459-463
Transmission electron microscopy (TEM) samples of an Mg-Al alloy has been prepared using a Ga-focused ion beam (FIB) milling at two different operating voltages of 10 kV and 40 kV to investigate the influence of the FIB energy on the sample quality. The fine structures of the samples have been studied using a high resolution TEM, and the concentration of the implanted Ga was analysed using an energy dispersive X-ray (EDX) analysis. The result of the TEM observation revealed that point defects were introduced to the sample finally milled at 40 kV but not at 10 kV. However, crystal lattice images and electron diffraction patterns were clearly observed on both the samples. The typical influence of the FIB energy was indicated in the elemental analysis. The relative Ga concentration in the thin sample finally milled at 10 kV was 1.0-2.0 at% that is less than half of 4.0-6.0 at% of the Ga concentration in the sample finally milled at 40 kV. A comparison between the experimental results of the Ga concentration measurement with simulation was also discussed. 相似文献
58.
59.
Koizumi H Yamamoto T Maki A Yamashita Y Sato H Kawaguchi H Ichikawa N 《Applied optics》2003,42(16):3054-3062
We will briefly review the present status of optical topography and then discuss the method of improving practicality, i.e., the signal-to-noise (S/N) ratio and the spatial resolution in observations of higher-order brain functions. The optimum wavelength pair improved the S/N ratio sixfold for deoxyhemoglobin, and new configurations of light irradiation and detection positions doubled the spatial resolution. We also report on developing application fields of optical topography. This modality will bridge the gap between natural sciences, neuroscience, and pedagogy, and show actual real-time brain activity. 相似文献
60.
We demonstrated an intrinsic conversion efficiency of 56% from the input fundamental power to the generated second-harmonic power. The second-harmonic power of 581 mW was obtained from the external cavity with a LiB3O5 crystal through the frequency doubling of a 1.17-W Ti:sapphire laser at 746 nm, when the finesse of the robust external cavity was 260. 相似文献