全文获取类型
收费全文 | 1474篇 |
免费 | 49篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 47篇 |
综合类 | 4篇 |
化学工业 | 390篇 |
金属工艺 | 24篇 |
机械仪表 | 29篇 |
建筑科学 | 22篇 |
能源动力 | 39篇 |
轻工业 | 196篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 75篇 |
一般工业技术 | 278篇 |
冶金工业 | 304篇 |
原子能技术 | 22篇 |
自动化技术 | 93篇 |
出版年
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 21篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 35篇 |
2017年 | 22篇 |
2016年 | 31篇 |
2015年 | 17篇 |
2014年 | 31篇 |
2013年 | 57篇 |
2012年 | 56篇 |
2011年 | 76篇 |
2010年 | 51篇 |
2009年 | 41篇 |
2008年 | 52篇 |
2007年 | 78篇 |
2006年 | 54篇 |
2005年 | 54篇 |
2004年 | 33篇 |
2003年 | 45篇 |
2002年 | 49篇 |
2001年 | 29篇 |
2000年 | 25篇 |
1999年 | 39篇 |
1998年 | 129篇 |
1997年 | 77篇 |
1996年 | 56篇 |
1995年 | 40篇 |
1994年 | 25篇 |
1993年 | 38篇 |
1992年 | 21篇 |
1991年 | 28篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1973年 | 2篇 |
1972年 | 4篇 |
排序方式: 共有1525条查询结果,搜索用时 31 毫秒
101.
R. Nishida J. Taniguchi R. Nomura Y. Okuda 《Journal of Low Temperature Physics》2007,148(3-4):109-113
We observed a profile of nonequilibrium superfluid-normal (SN) interface of 4He near a vertical wall. A glass, brass or copper wall was used. The SN interface was produced by cooling liquid 4He in a bath from the bottom, where liquid 4He was pumped through a flow impedance in order to cool down the liquid. Superfluid (Normal fluid) occupied the lower (upper)
part of the bath. The SN interface was visualized by three methods: simple visualization, shadowgraphy and schlieren method.
The interface touched a vertical glass wall at almost 90°. A large hollow was observed near a brass wall which had intermediate
thermal conductivity. Downward flow was observed on a copper wall due to the very good thermal conductivity of the wall. Various
types of interface profile were observed depending on the thermal conductivity of the wall used.
相似文献
102.
Fujisawa H. Kubouchi S. Kuroki K. Nishioka N. Riho Y. Noda H. Fujii I. Yoko H. Takishita R. Ito T. Tanaka H. Nakamura M. 《Solid-State Circuits, IEEE Journal of》2007,42(1):201-209
Three circuit techniques for an 8.1-ns column-access 1.6-Gb/s/pin 512-Mb DDR3 SDRAM using 90-nm dual-gate CMOS technology were developed. First, an 8:4 multiplexed data-transfer scheme, which operates in a quasi-4-bit prefetch mode, achieves a 3.17-ns reduction in column-access time, i.e., from 11.3 to 8.13 ns. Second, a dual-clock latency counter reduces standby power by 22% and cycle time from 1.7 to 1.2 ns. Third, a multiple-ODT-merged output buffer enables selection of five effective-resistance values Rtt (20, 30, 40, 60, and 120 Omega) without increasing I/O capacitance. Based on these techniques, 1.6-Gb/s/pin operation with a 1.36-V power supply and a column latency of 7 was accomplished 相似文献
103.
Interferograms obtained with ordinary interferometers, such as the Fizeau interferometer or the Twyman-Green interferometer, show the contour maps of a wave front under test. On the other hand, lateral shearing interferograms show the difference between a wave front under test and a sheared wave front, that is, the inclination of the wave front. Therefore the shape of the wave front under test is reconstructed by means of analyzing the difference. To reconstruct the wave front, many methods have been proposed. An integration method is usually used to reconstruct the wave front under test rapidly. However, this method has two disadvantages: The analysis accuracy of the method is low, and part of the wave front cannot be measured. To overcome these two problems, a new, to our knowledge, integration method, improved by use of polynomials, is proposed. The validity of the proposed method is evaluated by computer simulations. In the simulations the analysis accuracy achieved by the proposed method is compared with the analysis accuracy of the ordinary integration method and that of the method proposed by Rimmer and Wyant. The results of the simulations show that the analysis accuracy of the newly proposed method is better than that of the integration method and that of the Rimmer-Wyant method. 相似文献
104.
R Constantinides S Xenophontos P Neophytou S Nomura A Pierides CC Deltas 《Canadian Metallurgical Quarterly》1997,99(5):644-647
The PKD1 gene, which is responsible for the most common form of autosomal dominant polycystic kidney disease, has recently been cloned and sequenced. Many disease-causing mutations have been characterized in this gene, most of them resulting in premature protein termination. However, mutation analysis not routinely implemented for family investigations in a clinical setting, because of the large size and complexity of the gene. Instead, genetic linkage analysis using highly polymorphic CA dinucleotide repeats that map around the gene is still the method of choice. Recently, a few intragenic polymorphisms have been described that are also useful for linkage studies. Here, a new diallelic polymorphism is described for amino acid residue 4058, Ala/Val4058, with allelic frequencies of 0.88 and 0.12, respectively, and a heterozygosity of 0.23, in the Greek and Greek-Cypriot populations. Interestingly, this polymorphism and Ala4091-A/G, which has previously been described in Caucasians, were not detected in DNA from 44 Japanese samples tested. This is particularly important when allelic frequencies in a particular population are used for linkage analysis of families of different ethnic origin. Also, observation of the two polymorphisms together as haplotypes suggests that the Ala/Val4058 polymorphism occurred more recently than the establishment of the Ala4091-A/G polymorphism, and specifically on the G allele. 相似文献
105.
106.
107.
Yasuhiro Konishi Takeshi TsukiyamaKaori Ohno Norizoh SaitohToshiyuki Nomura Shinsuke Nagamine 《Hydrometallurgy》2006
Microbial reduction and intracellular precipitation of gold was achieved at 25 °C and pH 7 by using the mesophilic anaerobic bacterium Shewanella algae with H2 as the electron donor. The reductive precipitation of gold by S. algae was a fast process: 0.1–1 mol/m3 AuCl4− ions were completely reduced to insoluble gold within 30 min. The biogenic precipitates were crystalline gold nanoparticles of 10–20 nm present in the periplasmic space. The reducing power of S. algae at 3.2 × 1015 cells/m3 and 25 °C was comparable to that of aqueous citric acid solution (chemical reductant) at 20 mol/m3 and 50 °C. The intracellular recovery of gold is potentially attractive as an environmentally friendly alternative to conventional methods. 相似文献
108.
109.
Zen Kawasaki Koji Nomura Sachiko Yoshihashi Kenji Matsu‐ura 《Electrical Engineering in Japan》2001,134(4):62-69
Results of interferometric observations of cloud‐to‐ground flashes in Darwin (Australia) have been analyzed to investigate some features of the lightning phenomenon. Our study focused on comparison between multipoint and multiple negative cloud‐to‐ground flashes. The speed of leaders was estimated with submillisecond resolution for both multipoint and multiple strokes. Leaders preceding the first stroke in multiple‐stroke flashes progress in a stepped fashion, and their behavior exhibits the same features as leaders in multipoint flashes. The estimated average speed of the leaders is on the order of 105 m/s, and the mean step length is found to be 96 m with a mean pause time of 73 μs. The running time of the leader found from results of these observations has a mean value of 89 μs. The duration of UHF radiation bursts generated by leaders propagating along previously formed channels ranges from 0.2 to 55.3 ms with a mean value of 7.5 ms. By contrast, the duration of UHF radiation in leaders preceding multipoint strokes ranges from 21.1 to 90.6 ms with a mean value of 47.5 ms. The time intervals between strokes that strike at the same point as the previous stroke range from 22.5 to 330.6 ms with a mean value of 75.1 ms, while intervals between strokes in multipoint flashes range from 55.6 to 633.7 ms with a mean value of 149.1 ms. All leaders preceding multipoint strokes start in the same region inside the cloud. © 2001 Scripta Technica, Electr Eng Jpn, 134(4): 62–69, 2001 相似文献
110.
In this study, a new metabolic pathway for the synthesis of poly[(R)-3-hydroxybutyrate] [P(3HB)] was constructed in a recombinant Escherichia coli strain that utilized forward and reverse reactions catalyzed by two substrate-specific enoyl-CoA hydratases, R-hydratase (PhaJ) and S-hydratase (FadB), to epimerize (S)-3HB-CoA to (R)-3HB-CoA via a crotonyl-CoA intermediate. The R-hydratase gene (phaJ(Ac)) from Aeromonas caviae was coexpressed with the PHA synthase gene (phaC(Re)) and 3-ketothiolase gene (phaA(Re)) from Ralstonia eutropha in fadR mutant E. coli strains (CAG18497 and LS5218), which had constitutive levels of the beta-oxidation multienzyme FadB(Ec). When grown on glucose as the sole carbon source, the cells accumulated P(3HB) up to an amount 6.5 wt% of the dry cell weight, whereas the control cells without phaJ(Ac) or fadR mutation accumulated significantly smaller amounts of P(3HB). These results suggest that PhaJ(Ac) and FadB(Ec) played an important role in supplying monomers for P(3HB) synthesis in the pathway. Furthermore, by using this pathway, a P(3HB)-concentration-dependent fluorescent staining screening technique was developed to rapidly identify cells that possess active R-hydratase. 相似文献