全文获取类型
收费全文 | 1480篇 |
免费 | 10篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 17篇 |
综合类 | 6篇 |
化学工业 | 127篇 |
金属工艺 | 22篇 |
机械仪表 | 29篇 |
建筑科学 | 17篇 |
矿业工程 | 1篇 |
能源动力 | 46篇 |
轻工业 | 30篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
武器工业 | 1篇 |
无线电 | 163篇 |
一般工业技术 | 137篇 |
冶金工业 | 807篇 |
原子能技术 | 3篇 |
自动化技术 | 87篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 60篇 |
2012年 | 25篇 |
2011年 | 28篇 |
2010年 | 29篇 |
2009年 | 34篇 |
2008年 | 38篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 20篇 |
2004年 | 26篇 |
2003年 | 34篇 |
2002年 | 22篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 46篇 |
1998年 | 268篇 |
1997年 | 154篇 |
1996年 | 95篇 |
1995年 | 61篇 |
1994年 | 42篇 |
1993年 | 83篇 |
1992年 | 15篇 |
1991年 | 30篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 22篇 |
1987年 | 22篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 17篇 |
1976年 | 59篇 |
1974年 | 1篇 |
排序方式: 共有1497条查询结果,搜索用时 15 毫秒
1.
气相二氧化硅生产现状及其在涂料中的应用 总被引:5,自引:0,他引:5
介绍了气相二氧化硅国内外生产状况,根据气相二氧化硅在涂料方面的应用特点及主 要技术关键的分析,提出了建议。 相似文献
2.
Shiue-Lung Chen Shui-Jinn Wang Kai-Ming Uang Tron-Min Chen Wei-Chi Lee Bor-Wen Liou 《Photonics Technology Letters, IEEE》2007,19(6):351-353
Through the use of selective nickel (Ni) electroplating, patterned laser liftoff technique, and surface roughing of the top n-GaN epilayer, a novel process for the fabrication of vertical-structured metal-substrate GaN-based light-emitting diodes (VM-LEDs) to avoid difficulties in Ni substrate dicing and improve device yield was proposed and demonstrated. In conjunction with a sidewall passivation with SiO2 and keeping the size of epilayer smaller than that of Ni island, a considerable improvement in yield and device performance were shown. As compared to conventional lateral-structured GaN-based LEDs, VM-LEDs show an increase in light output power about 174% at 350 mA with a significant decrease in forward voltage from 3.5 to 3.17 V 相似文献
3.
Ohtsu M. Liou K.-Y. Burrows E.C. Burrus C.A. Eisenstein G. 《Electronics letters》1987,23(21):1111-1113
A problem in frequency-tuning of external-cavity lasers is mode-hopping between neighbouring external-cavity modes. We demonstrate a new interferometric method for monitoring mode-hoping and an automatic control circuit for a 1.3 ?m grating external-cavity laser that maintains single-mode operation when the lasing frequency is tuned. 相似文献
4.
G Knowles GJ Grindlay MS Campo LM Chandrachud BW O''Neil 《Canadian Metallurgical Quarterly》1997,62(3):289-291
In vivo dosimetry performed with semiconductor detectors is a reliable method for patient dose control. The purpose of this study is to evaluate the perturbations introduced in the patient's absorbed dose distribution by three types of commercially available diodes (Isorad, Sun Nuclear Corp.; model 114200, 114300 and 114400) from the same company and to present possible solutions for minimizing this side-effect. 相似文献
5.
We report two cases of massive, solitary, plexiform schwannoma. One was a 9-cm subcutaneous lesion on the hip of a 72-year-old man who had become aware of the slow-growing tumor 50 years earlier; the other is the first reported plexiform schwannoma to arise in a visceral organ: it arose in the ascending colon of a 54-year-old man and exhibited a dumbbell configuration with submucosal and subserosal components. Neither patient had neurofibromatosis or schwannomatosis. Both tumors were well-circumscribed and multinodular, and both showed a plexiform architecture. Microscopically, the nodules were composed primarily of Antoni A tissue, replete with nuclear palisading and Verocay bodies. Examination by immunohistochemistry and electron microscopy demonstrated the features of well-differentiated Schwann cells; nodules were surrounded by attenuated, residual perineurium. Both patients followed a benign clinical course, without recurrence or metastasis. Neither the large tumor size nor the unusual locations affected the biologic behavior of these neoplasms. A massive plexiform schwannoma must be distinguished from a malignant peripheral nerve sheath tumor and from a plexiform neurofibroma, a tumor prone to malignant transformation. 相似文献
6.
K Stelwagen DG Grieve JS Walton JL Ball BW McBride 《Canadian Metallurgical Quarterly》1993,76(4):992-1001
Twenty-five primigravid ewes were used to investigate the effect of bST, between 97 and 124 d of gestation, on mammogenesis and subsequent milk production. Five ewes (reference group) were slaughtered at 96 d of gestation, and the remaining ewes were injected daily with saline (control group: n = 10) or .1 mg/kg of BW of bST (bST group: n = 10). Following bST treatment, 5 control and 5 bST group ewes were slaughtered (slaughter group). The remaining ewes were slaughtered after lambing and being milked for 8 wk (production group). Weekly blood samples were obtained from both slaughter and production group ewes. Slaughter group ewes were also subjected to 8-h serial blood sampling at 98 d (period 1) and 123 d (period 2) of gestation. Milk production was 42% higher in ewes treated prepartum with bST than in those treated with saline. Results suggest that the increase in milk was due to an increase in mammary parenchymal cell number rather than to an increase in cellular activity. The high rate of [3H]thymidine incorporation into parenchymal tissue in reference group ewes suggests that the increase in parenchyma during the second trimester of gestation is due to cellular hyperplasia but that cellular hypertrophy may be more important during the last trimester. Plasma IGF-I concentrations were significantly higher during bST treatment and remained elevated between daily injections; the increase was greatest in period 2. 相似文献
7.
ME Goldberg BW Lex NK Mello JH Mendelson TA Bower 《Canadian Metallurgical Quarterly》1996,66(2):228-238
Research on achievement goal orientation in sport has relied primarily on traditional statistical methodology to examine group mean differences. Unfortunately, examination of the measurement model is generally ignored prior to means testing. This study reports an application of structural equation modeling (SEM) in testing measurement invariance and latent mean structure of the Task and Ego Orientation in Sport Questionnaire (TEOSQ; Duda & Nicholls, 1989) using male and female college students. A confirmatory factor analysis for testing invariance revealed invariant measurement properties and factor structures across gender, indicating that task and ego orientation are similarly conceptualized by male and female students. Subsequent testing of latent mean structures, however, showed significant gender differences with respect to ego orientation, but no difference in task orientation. The SEM procedures used in the present study demonstrate additional construct validity and internal consistency reliability for the TEOSQ and, by confirming its factor structure, provide a sound psychometric basis for its continued use in substantive studies focusing on the comparison of achievement goal orientation across gender. 相似文献
8.
In this paper, we present efficient VLSI architectures for full-search block-matching motion estimation (BMME) algorithm. Given a search range, we partition it into sub-search arrays called tiles. By fully exploiting data dependency within a tile, efficient VLSI architectures can be obtained. Using the proposed VLSI architectures, all the block-matchings in a tile can be processed in parallel. All the tiles within a search range can be processed serially or concurrently depending on various requirements. With the consideration of processing speed, hardware cost, and I/O bandwidth, the optimal tile size for a specific video application is analyzed. By partitioning a search range into tiles with appropriate size, flexible VLSI designs with different throughput can be obtained. In this way, cost effective VLSI designs for a wide range of video applications, from H.261 to HDTV, can be achieved. 相似文献
9.
BW Woodward JW Mabry MT See JK Bertrand LL Benyshek 《Canadian Metallurgical Quarterly》1993,71(8):2040-2046
An animal model and computer software were developed to conduct across-herd genetic evaluations using data from producers participating in the Sow Productivity Index program of the American Yorkshire Club. The final data set consisted of 61,596 litter records from 1986 to early 1990. The animal model included fixed contemporary group effects and random additive direct, service sire, permanent environmental, and residual effects. Additive genetic relationships among animals were included. A separate relationship matrix for service sires and their sires was also included. A data set similar to the Yorkshire field data was simulated to use in testing the animal model. The simulated data set consisted of 40 herds, each with 120 reproducing dams and either four or five sires. Six generations of simulated data were produced, resulting in 20,605 litter records. These records were then evaluated using the animal model for number of pigs born alive. Finally, correlations between the true breeding values from the simulation and the predicted breeding values were computed. The correlation between the 918 true and predicted sire breeding values was considerably lower for the animal model without a service sire effect than when it was included (.53 vs .74, respectively). However, the difference was cut in half (.66 vs .77) when only sires with greater than five daughter records were included. The high accuracy of the animal model with a random service sire effect indicates that the proposed model adequately accounts for the variation found in records for number of pigs born alive. 相似文献
10.