全文获取类型
收费全文 | 1296篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 38篇 |
化学工业 | 307篇 |
金属工艺 | 19篇 |
机械仪表 | 23篇 |
建筑科学 | 9篇 |
矿业工程 | 1篇 |
能源动力 | 19篇 |
轻工业 | 65篇 |
无线电 | 91篇 |
一般工业技术 | 270篇 |
冶金工业 | 340篇 |
原子能技术 | 67篇 |
自动化技术 | 75篇 |
出版年
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 20篇 |
2020年 | 20篇 |
2019年 | 16篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 27篇 |
2015年 | 9篇 |
2014年 | 16篇 |
2013年 | 54篇 |
2012年 | 43篇 |
2011年 | 64篇 |
2010年 | 31篇 |
2009年 | 42篇 |
2008年 | 38篇 |
2007年 | 47篇 |
2006年 | 46篇 |
2005年 | 42篇 |
2004年 | 35篇 |
2003年 | 32篇 |
2002年 | 27篇 |
2001年 | 25篇 |
2000年 | 30篇 |
1999年 | 36篇 |
1998年 | 118篇 |
1997年 | 83篇 |
1996年 | 62篇 |
1995年 | 26篇 |
1994年 | 51篇 |
1993年 | 30篇 |
1992年 | 20篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 17篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有1324条查询结果,搜索用时 31 毫秒
81.
82.
Summary
Organocobalt poly(arylene-vinylene)s composed of 1,2- or 1,3- linkage at their cyclobutadiene moieties (3 and 4, respectively) were prepared by the Heck reaction of p-divinylbenzene with (cyclobutadiene)cobalt-containing monomers having two aryl bromide moieties (1 and 2, respectively). The number average molecular weights (M
n) of the obtained organocobalt poly(arylene-vinylene)s (3 and 4) were 4,100 and 4,000, respectively (GPC, on the basis of polystyrene). UV-vis spectra of 3 and 4 exhibited main π-π* absorption peaks at 362 and 397 nm, respectively, which were ca. 60 nm bathochromically shifted from those of the corresponding
monomeric units. Both polymers were found to show thermotropic liquid crystallinity in the range of room temperature to ca.
80 °C by employing differential scanning calorimetry (DSC) and the optical measurement using crossed polarizers.
Received: 2 July 1999/Accepted: 29 July 1999 相似文献
83.
This paper presents a technique to differentially diagnose two types of localized gear tooth faults: a spall and a crack in the gear tooth fillet region. These faults could have very different prognoses, but existing diagnostic techniques only detect the presence of localized tooth faults without being able to differentiate between a spall and a crack. The effects of spalls and cracks on the behaviour of gear assemblies were studied using static and dynamic simulation models. Changes in the kinematics of a pair of meshing gears due to a gear tooth fillet crack (TFC) and a tooth flank spall were compared using a static analysis model. The difference in the variation of the transmission error (TE) caused by the two faults reveals their characteristics. The effect of a tooth crack depends on the change in stiffness of the tooth while the effect of a spall is dominantly determined by the geometry of the fault. A technique has previously been proposed to detect spalls [M. EL Badaoui, J. Antoni, F. Guillet, J. Daniere, Use of the moving cepstrum integral to detect and localize tooth spalls in gears, Mechanical System and Signal Processing, 15 (5) (2001) 873–885; M. EL Badaoui, V. Cahouet, F. Guillet, J. Daniere P. Velex, Modelling and detection of localized tooth defects in geared systems, Transaction of ASME, 123 (2001) 422–430], using the cepstrum to detect a negative echo in the signal (from entry into and exit from the spall) and successfully performed differential diagnosis on the simulated vibration signals. While the result of the experimental study showed some differences from the result of the simulation study, the differential diagnosis was successfully performed based on the technique presented in this paper. Further investigation revealed non-linear gearmesh behaviour which was causing differences in the experimental and simulation model results. 相似文献
84.
I Hirao S Yoshinari S Yokoyama Y Endo AD Ellington 《Canadian Metallurgical Quarterly》1997,(37):283-284
Ribosome-inactivating proteins, such as ricin, pepocin and gypsophilin, catalyze the hydrolysis of a single N-glycosidic bond at a specific position in rRNAs. Aptamers targeting pepocin were selected from a random sequence RNA pool that spanned 30 positions. After 8 rounds, the anti-pepocin aptamers were sequenced and a conserved hairpin motif was identified. Interestingly, the selected motif is quite different from the toxin-binding domains of rRNAs. 相似文献
85.
Shigeo Yamabe Kazuo Kobayashi-Hattori Kentaro Kaneko Hiroshi Endo Toshichika Takita 《Food chemistry》2007,100(1):369-374
To clarify the effect of soybean varieties on isoflavone, a useful component for human health, in soybean products, we investigated changes in the isoflavone content and composition in rice-koji miso, after fermentation/aging for 6 or 12 months using varieties of soybeans (Tohoku-126, Tohoku-135, Tohoku-139, Suzuyutaka and Chinese soybeans), by high performance liquid chromatography. In soybeans, the total isoflavone content in Tohoku-126 was 444 mg/100 g, which was 1.2–2.0 times the content in the other soybean varieties. The malonyl glycosides and aglycones in soybeans accounted for more than 60% and only a few percent, respectively. As for rice-koji miso, the total isoflavone and aglycone contents were the highest in miso prepared from Tohoku-126. The ratios of glycosides to aglycones (80.1–92.6%) in miso were higher than those in the original soybeans. The time course of the isoflavone composition during the fermentation/aging process of rice-koji miso indicated that glycosides decreased from 86.4% to 44.9% after 6 months but aglycones increased from 9.6% to 53.3%. 相似文献
86.
We study population dynamics of a trapped spin-1 Bose gas above the Bose-Einstein transition temperature. Starting from the semiclassical kinetic equation for a spin-1 gas, we derive coupled rate equations for the populations of internal states. Solving the rate equations, we study the dynamical evolution of spin populations. We also estimate the characteristic timescale in which the system reaches equilibrium. Finally, we briefly discuss the extension of the theory to Bose-condensed phase below the Bose-Einstein transition temperature, and discuss the static equilibrium condition for the spin-1 system. 相似文献
87.
Endo T. Murayama Y. Sakamoto Y. Sakuraba T. Shiota F. 《IEEE transactions on instrumentation and measurement》1989,38(2):229-232
A series of systems composed of cryogenic devices such as a Josephson potentiometer and a cryogenic current comparator, developed to precisely measure a current with any value up to 1 A, is proposed. These systems will be used to measure the injected electrical energy with an uncertainty of the order of 0.01 p.p.m. or less in the absolute measurement of the magnetic flux quantum by superconducting magnetic levitation. Some preliminary experiments are described 相似文献
88.
Some tetracycline (TC) antibiotics, including TC and anhydrotetracycline, have been found to enhance specific binding of low
density lipoprotein (LDL) to both LDL receptor-positive and-negative cells at relatively higher concentrations. When incubated
at 37°C, the ability of LDL receptor-negative human fibroblasts to bind 125I-LDL was increased from<2 to 45 ng/mg by 170 μM TC. In normal human fibroblasts and Hep G2 cells, 125I-LDL binding was elevated 1.4- to 2-fold by 113 μM TC. The 125I-LDL binding in the presence of TC was diminished by both heparin and EDTA. The enhancement by TC was not observed when 125I-LDL binding was assayed at 4°C. TC enhanced LDL binding to paraformaldehyde-fixed Hep G2 cells, excluding LDL receptor induction
in the mechanism. These results demonstrated that TC enhanced cellular LDL binding through a process not involving functional
LDL receptors. 相似文献
89.
90.
Sho Kataoka Takuji Yamamoto Yuki Inagi Akira Endo Masaru Nakaiwa Takao Ohmori 《Carbon》2008,46(10):1358-1360
Mesoporous carbon thin films with ordered structures were prepared by using resorcinol-surfactant self-assembly. A mixture of resorcinol, surfactant, and ethanol coated on silicon substrates was exposed to formaldehyde vapor as a cross-linking agent to form structured resorcinol/formaldehyde resin films. The films were then carbonized at 800 °C in an inert atmosphere to remove the surfactant and to obtain structured carbon materials. With this vapor infiltration method, thin films with several structures were obtained from the same precursor solution by employing different vapor infiltration temperatures. The results were interpreted from the transformation of the self-assembly during the vapor infiltration process. 相似文献