全文获取类型
收费全文 | 1475篇 |
免费 | 27篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 47篇 |
综合类 | 4篇 |
化学工业 | 236篇 |
金属工艺 | 37篇 |
机械仪表 | 40篇 |
建筑科学 | 22篇 |
矿业工程 | 1篇 |
能源动力 | 35篇 |
轻工业 | 125篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 159篇 |
一般工业技术 | 217篇 |
冶金工业 | 436篇 |
原子能技术 | 39篇 |
自动化技术 | 103篇 |
出版年
2023年 | 9篇 |
2022年 | 18篇 |
2021年 | 20篇 |
2020年 | 8篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 48篇 |
2012年 | 41篇 |
2011年 | 55篇 |
2010年 | 43篇 |
2009年 | 39篇 |
2008年 | 44篇 |
2007年 | 41篇 |
2006年 | 41篇 |
2005年 | 40篇 |
2004年 | 45篇 |
2003年 | 53篇 |
2002年 | 42篇 |
2001年 | 32篇 |
2000年 | 33篇 |
1999年 | 46篇 |
1998年 | 172篇 |
1997年 | 89篇 |
1996年 | 84篇 |
1995年 | 51篇 |
1994年 | 34篇 |
1993年 | 50篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 17篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有1506条查询结果,搜索用时 15 毫秒
71.
The refractive index profile of germanium doped preforms for optical fibers is determined by the radial distribution of germanium concentration. Knowing that there is a correlation between the germanium doping profile and the deposition surface profile of vapor-phase axial deposition (VAD) preforms, the study of this correlation has been carried out in order to estimate, indirectly, the refractive index profile of VAD preforms for optical fibers during the deposition stage. This correlation was studied through the parameterization of the preform deposition surface using two parameters: the power law index profile that best fits the preform bottom profile (/spl alpha/) and the axial distance from the bottom tip to a reference height (h). A range of values of these parameters to produce VAD preforms with standard and special doping profiles has been presented. Preforms with triangular index profile can be fabricated with /spl alpha/ and h values of about 2.0 and 5.0 mm, respectively, and preforms with parabolic index profiles can be produced with /spl alpha/ and h values of about 2.0 and 4.0 mm, respectively. 相似文献
72.
Watanabe Y Ichikawa H Kayama O Ono K Kaneoka K Inami S 《Accident; analysis and prevention》2000,32(2):243-250
To analyze the effect of the seat characteristics on dummy motions and human volunteer motions, sled tests simulating low-speed rear impacts were conducted with some seats which had different characteristics. Volunteer's cervical vertebral motions were photographed with an X-ray cineradiographic system at a speed of 90 frames/s as well as the visible motions of dummy's and volunteer's were recorded. Although the tests were conducted under limited conditions, the results indicated the relationship between the occupant's visible motions, which are assumed to be closely related to the whiplash injury mechanism, and seat characteristics. It should be noted that the volunteer sled tests were discussed and approved by the Tsukuba University Ethics Committee and the volunteer submitted his informed consent in writing in line with the Helsinki Declaration. 相似文献
73.
Ono Y Kushibiki J 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(4):1042-1050
The propagation characteristics, viz., phase velocity and attenuation, of leaky surface acoustic waves (LSAWs), excited on the water/sample boundary are obtained through analyzing the V(z) curves measured by line-focus-beam acoustic microscopy. However, different values of these characteristics are obtained, depending upon different ultrasonic devices and operating frequencies employed. The construction mechanism of V(z) curves was investigated experimentally by measuring the amplitude and phase for Teflon to provide an understanding of the device performance for velocity measurements. A V(z) curve measured for Teflon, on which no leaky waves are excited when water is the coupling medium, can be used for the characteristic device response, depending only upon the device parameters and the operating frequencies. From the investigation of the ultrasonic device and the frequency dependences of the characteristic device responses, the phase gradient was found to be directly related to values of measured LSAW velocities. From this result, apparent frequency dependences in LSAW velocity measurements are explained quantitatively for a specimen of gadolinium gallium garnet. 相似文献
74.
Kushibiki J Ohashi Y Ono Y 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(4):1068-1076
This paper demonstrates the evaluation and selection of commercially available LiNbO(3) and LiTaO(3) single crystals and wafers for surface acoustic wave (SAW) devices using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. This system enables measuring leaky-SAW (LSAW) propagation characteristics precisely and efficiently for a number of specimens. The wafers are prepared from the top, middle, and bottom parts of four 128 degrees YX LiNbO(3) and seven X-112 degrees Y LiTaO(3) single crystals. For both series of crystals, the measured LSAW velocities increase from top to bottom in the crystals and with the increasing crystal growth number. The velocity changes for all wafers are 0.036% for 128 degrees YX LiNbO(3) and 0.035% for X-112 degrees Y LiTaO(3), corresponding to changes of 0.038 mol% and 0.075 mol% in Li(2)O concentration, respectively. Moreover, the inhomogeneity in the first X-112 degrees Y LiTaO(3) single crystal caused by some undesirable wafer fabrication processes can be detected precisely, although it is difficult for the conventional methods to obtain such information. 相似文献
75.
76.
Shigeta S Suzuki O Aki Y Kawamoto S Ono K 《Journal of Bioscience and Bioengineering》2000,89(1):84-86
Sea squirt alpha-N-acetylgalactosaminidase was purified to homogeneity. Its molecular weight was estimated to be approximately 160,000 by gel filtration and 40,000 by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing condition. The chromatographic and electrophoretic behaviors indicated that the enzyme was composed of four subunits. The optimum pH of the enzyme reaction was about 4.0 at 37 degrees C, while the enzyme was stable in the range of pH 5.0 to 6.0 during 4 h preincubation at 37 degrees C. Although the enzyme (0.1 unit) was stable at 0 degrees C for 30 min in the presence of 7.5 mM metal ions (Al3+, Ba2+, Ca2+, K+, Mn2+, Pb2+, Sr2+, and Zn2+), almost 40% of the enzyme activity was lost in the presence of Cu2+, Hg2+, monoiodoacetic acid, and EDTA. The enzyme hydrolyzed aryl N-acetyl-alpha-D-galactosaminide as well as GalNAcalpha1(-->4GalNAcalpha1-->)n 4GalNAc-p-aminobenzoic acid ethyl ester (ABEE) (n = 1-4), but GalNAcalpha1-->4GalNAc-ABEE only scarcely. Furthermore, an allergenic pentasaccharitol ABEE derivative, GalNAcalpha1-->2Fucalpha1-->3(GalNAcbeta1-->4) GlcNAcbeta1-->2(3-acetoamido-3-deoxy)L-threose-ABEE, the minimum structural unit for the sea squirt allergenicity was hydrolyzed to 95 mol% for 72 h incubation with the enzyme. The enzyme could be utilized as a powerful tool for the structural analyses of the carbohydrate epitopes of the sea squirt allergen molecules. 相似文献
77.
Simone Fujii Ricardo Marcelo Reche Ribeiro Maria Brígida Dos Santos Scholz Elisabete Yurie Sataque Ono Cássio Egidio C Prete Eiko Nakagawa Itano Yoshio Ueno Osamu Kawamura Elisa Yoko Hirooka 《Food Additives & Contaminants》2006,23(9):902-909
The performance of an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) based on a monoclonal antibody (mAb) for ochratoxin A (OTA) detection was evaluated in a comparative study with high-performance liquid chromatography (HPLC) analysis using 68 freshly harvested coffee samples from the North of Paraná State, Brazil. The anti-OTA mAb showed high specificity and low cross-reactivity with OTA analogues (OTB and OTalpha), but cross-reacted with OTC. This ic-ELISA showed a detection limit of 3.75 ngg-1 sample, when compared to 0.80 ngg-1 by HPLC, with an ic-ELISA/HPLC correlation coefficient of 0.90. As regards OTA analysis of these coffee samples, natural contamination was detected in 10 samples (14.7%) by both methods, where the ic-ELISA values (range 3.9-7.3 ngg-1) were 1.1 to 1.6-fold higher than HPLC data (2.7-4.7 ngg-1). Five samples (7.4%) were OTA positive (range 0.84-1.30 ngg-1) only by HPLC assay, probably due to the higher detection limit reached by ic-ELISA. OTA was undetectable in 53 samples (77.9%) by both methods, while all positive samples (range 0.84-7.30 ngg-1) showed OTA levels lower than 8 ngg-1 (maximum limit recommended by the European Union). The matrix interference of green coffee was minimized by dilution of sample extracts before carrying out the ELISA assay. This mAb-based ic-ELISA can be effectively applied for OTA screening in coffee, because it is simple, sensitive and sample preparation is easy. 相似文献
78.
To more completely describe acromion morphology and its relationship to impingement syndrome, we performed three-dimensional magnetic resonance imaging (N = 111) or computed tomography (N = 27) on 132 symptomatic shoulders. The mean patient age was 46.2 years (range, 14 to 86). Four parameters were evaluated: the angle of anterior slope of the acromion in the midsagittal and lateral-sagittal planes, lateral acromial angulation in the coronal plane, and the presence or absence of medial encroachment in the acromioclavicular joint. Twenty-five asymptomatic age-matched shoulders were used as controls. All imaging data were combined because no significant differences existed between the two imaging techniques. The mean acromion angle was 19.4 degrees in the midsagittal plane and 20 degrees in the lateral-sagittal plane. In the coronal plane, 97 (73%) acromions were neutral and 35 (27%) were downward sloping. Medial encroachment was present in 31 (24%) shoulders. Age distribution from the 2nd to 8th decade demonstrated a consistent and gradual transition from a flat acromion in the younger decades to a more hooked acromion in the older decades that was significant in both the midsagittal and lateral-sagittal planes. Furthermore, a greater percentage of patients were found to have downward angulating acromions with increasing age. Ninety-eight patients (74%) had stage II or III impingement. Of these shoulders, 39 (40%) had type I acromions, 51 (52%) type II, and 8 (8%) type III. Twenty-eight of 33 acromions with coronal lateral downward sloping had impingement, and all 31 shoulders with medial encroachment had impingement. 相似文献
79.
T Shiina G Tamiya A Oka T Yamagata N Yamagata E Kikkawa K Goto N Mizuki K Watanabe Y Fukuzumi S Taguchi C Sugawara A Ono L Chen M Yamazaki H Tashiro A Ando T Ikemura M Kimura H Inoko 《Canadian Metallurgical Quarterly》1998,47(3):372-382
The biomechanics of medialization laryngoplasty are not well understood. An excised canine larynx model was used to test the effects of various sized silicon implants. The vocal fold length, position, and tension were measured. Medialization laryngoplasty did not affect vocal fold length. At the mid-membranous vocal fold, larger shims resulted in greater medialization and tension. Medialization laryngoplasty neither medialized nor stiffened the vocal process to resist lateralizing forces. We conclude that medialization laryngoplasty provides bulk and support for defects of the membranous region of the vocal fold, but does not appear to close a posterior glottal gap. The selection of a surgical procedure to treat glottal incompetence should take into account the unique biomechanical properties of the anterior (membranous vocal folds) and posterior (cartilaginous portion) glottis. 相似文献
80.
K Ono 《Canadian Metallurgical Quarterly》1998,18(2):132-141
OBJECTIVE: (1) To determine which facial landmarks show the greatest movement during specific facial animations and (2) to determine the sensitivity of our instrument in using these landmarks to detect putatively abnormal facial movements. DESIGN: Movements of an array of skin-based landmarks on five healthy human subjects (2 men and 3 women; mean age, 27.6 years; range, 26 to 29 years) were observed during the execution of specific facial animations. To investigate the instrument sensitivity, we analyzed facial movements during maximal smile animations in six patients with different types of functional problems. In parallel, a panel was asked to view video recordings of the patients and to rate the degree of motor impairment. Comparisons were made between the panel scores and those of the measurement instrument. RESULTS: Specific regions of the face display movement that is representative of specific animations. During the smile animation, landmarks on the mid- and lower facial regions demonstrated the greatest movement. A similar pattern of movement was seen during the cheek puff animation, except that the infraorbital and chin regions demonstrated minimal movement. For the grimace and eye closure animations, the upper, mid-facial, and upper-lip regions exhibited the greatest movement. During eye opening, the upper and mid-facial regions, excluding the upper lip and cheek, moved the most, and during lip purse, markers on the mid- and lower face demonstrated the most movement. We used the smile-sensitive landmarks to evaluate individuals with functional impairment and found good agreement between instrument rankings based on the data from these landmarks and the panel rankings. CONCLUSION: The present method of three-dimensional tracking has the potential to detect and characterize a range of clinically significant functional deficits. 相似文献