全文获取类型
收费全文 | 1479篇 |
免费 | 56篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 16篇 |
综合类 | 3篇 |
化学工业 | 431篇 |
金属工艺 | 41篇 |
机械仪表 | 28篇 |
建筑科学 | 70篇 |
矿业工程 | 15篇 |
能源动力 | 22篇 |
轻工业 | 165篇 |
水利工程 | 1篇 |
石油天然气 | 11篇 |
无线电 | 82篇 |
一般工业技术 | 297篇 |
冶金工业 | 175篇 |
原子能技术 | 14篇 |
自动化技术 | 168篇 |
出版年
2021年 | 19篇 |
2020年 | 14篇 |
2019年 | 25篇 |
2018年 | 25篇 |
2017年 | 17篇 |
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 35篇 |
2013年 | 50篇 |
2012年 | 51篇 |
2011年 | 61篇 |
2010年 | 51篇 |
2009年 | 53篇 |
2008年 | 50篇 |
2007年 | 47篇 |
2006年 | 47篇 |
2005年 | 36篇 |
2004年 | 39篇 |
2003年 | 18篇 |
2002年 | 28篇 |
2001年 | 26篇 |
2000年 | 33篇 |
1999年 | 35篇 |
1998年 | 38篇 |
1997年 | 38篇 |
1996年 | 26篇 |
1995年 | 27篇 |
1994年 | 29篇 |
1993年 | 20篇 |
1992年 | 32篇 |
1991年 | 23篇 |
1989年 | 21篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 25篇 |
1983年 | 27篇 |
1982年 | 27篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 27篇 |
1975年 | 36篇 |
1974年 | 19篇 |
1973年 | 24篇 |
1972年 | 14篇 |
1971年 | 15篇 |
1970年 | 19篇 |
排序方式: 共有1539条查询结果,搜索用时 15 毫秒
131.
Andrew J. Allen Susan Krueger Ganesh Skandan Gabrielle G. Long Horst Hahn Helen M. Kerch John C. Parker Mohammad N. All 《Journal of the American Ceramic Society》1996,79(5):1201-1212
Using small-angle scattering, together with density measurements, X-ray diffraction, nitrogen adsorption, and both transmission and scanning electron microscopy, the microstructural evolution during sintering in nanostructured ceramic oxides has been studied. The availability of samples with sufficient size and uniformity has permitted absolute calibration of the scattering data and made possible determinations of microstructural parameters and surface areas that are statistically representative of the undisturbed nanophase morphologies. A fully quantitative microstructural model has been developed, and the effects of varying processing parameters during powder synthesis and sintering have been assessed. Predictions are made regarding the achievable sintered full-density microstructures. 相似文献
132.
A mesh-vertex finite volume scheme for solving the Euler equations on triangular unstructured meshes is implemented on a MIMD (multiple instruction/multiple data stream) parallel computer. Three partitioning strategies for distributing the work load onto the processors are discussed. Issues pertaining to the communication costs are also addressed. We find that the spectral bisection strategy yields the best performance. The performance of this unstructured computation on the Intel iPSC/860 compares very favorably with that on a one-processor CRAY Y-MP/1 and an earlier implementation on the Connection Machine.The authors are employees of Computer Sciences Corporation. This work was funded under contract NAS 2-12961 相似文献
133.
134.
Horst S. Bairavasubramanian R. Tentzeris M.M. Papapolymerou J. 《Microwave Theory and Techniques》2007,55(11):2439-2446
A modification of the Wilkinson power divider is presented that eases planar implementation while maintaining performance. By adding transmission lines between the resistor and the quarter-wave transformers of the traditional design, a range of valid solutions exists that meet the conditions of being reciprocal, isolated between the output ports, and matched at all ports. The proposed design is particularly useful at millimeter-wave frequencies where reduced physical dimensions make a circuit configuration suitable for low-cost package-level implementation difficult using traditional methods. Two frequency bands are demonstrated. At V-band, the circuit gives 0.3-dB excess insertion loss, 19-dB isolation, and 50% bandwidth. At the W-band, the circuit gives 0.75-dB excess insertion loss, 24-dB isolation, and 39% bandwidth. 相似文献
135.
136.
137.
CM van der Horst CA de Borgie JL Knopper PM Bossuyt 《Canadian Metallurgical Quarterly》1997,50(6):463-467
OBJECTIVE: To find out if lactulose can prevent the bacterial translocation that is induced by obstructive jaundice in rats. DESIGN: Laboratory experiment. SETTING: Teaching hospital, Turkey. MATERIAL: 50 male Wistar-albino rats. INTERVENTIONS: 10 rats were not operated on and used as controls; 20 rats underwent laparotomy and sham ligation of the common bile duct (CBD); 20 had the CBD ligated alone; and 20 had the CBD ligated and were given oral lactulose 2 ml/day until death. All rats were killed after 14 days. MAIN OUTCOME MEASURES: Presence of Escherichia coli in mesenteric lymph nodes (MLN), and bacterial overgrowth as indicated by counts of E coli in the caecum. RESULTS: There was significantly less bacterial translocation to MLN in the group that had been given lactulose compared with CBD-ligated and lactulose not given (2/20 compared with 8/20, p = 0.06). There was also a significant reduction in the number of Gram negative bacteria in that group (p = < 0.01). CONCLUSION: Lactulose seems to reduce the incidence of translocation from the gut to MLN in rats with obstructive jaundice. 相似文献
138.
DM Parenti PL Williams R Hafner MR Jacobs P Hojczyk TM Hooton TW Barber G Simpson C van der Horst J Currier WG Powderly M Limjoco JJ Ellner 《Canadian Metallurgical Quarterly》1998,12(18):2439-2446
OBJECTIVE: To determine the clinical and microbiologic benefit of adding amikacin to a four-drug oral regimen for treatment of disseminated Mycobacterium avium infection in HIV-infected patients. DESIGN: A randomized, open-labeled, comparative trial. SETTING: Outpatient clinics. PATIENTS: Seventy-four patients with HIV and symptomatic bacteremic M. avium infection. INTERVENTIONS: Rifampin 10 mg/kg daily, ciprofloxacin 500 mg twice daily, clofazimine 100 mg every day, and ethambutol 15 mg/kg orally daily for 24 weeks, with or without amikacin 10 mg/kg intravenously or intramuscularly 5 days weekly for the first 4 weeks. MAIN OUTCOME MEASURE: Clinical and microbiologic response at 4 weeks; quantitative level of bacteremia with M. avium. RESULTS: No difference in clinical response was noted with the addition of amikacin to the four-drug oral regimen, and only 25% in either group had a complete or partial response at 4 weeks. A comparable quantitative decrease in bacteremia was noted in both treatment groups, with 16% of patients being culture-negative at 4 weeks and 38% at 12 weeks. Toxicities were mainly gastrointestinal. Amikacin was well tolerated. Median survival was 30 weeks in both groups. CONCLUSIONS: The addition of amikacin to a four-drug oral regimen of rifampin, ciprofloxacin, clofazimine, and ethambutol did not provide clinical or microbiologic benefit. 相似文献
139.
Liu J.J. Olver K.A. Monica Taysing-Lara Taylor T. Wayne Chang Horst S. 《Components and Packaging Technologies, IEEE Transactions on》2003,26(3):548-553
Oxide-confined top-emitting 850 nm and bottom-emitting 980 nm vertical-cavity surface-emitting laser (VCSEL) 8/spl times/8 arrays were designed and fabricated for applications of optical interconnects. The arrays were flip-chip bonded onto sapphire substrates that contain complimentary metal-oxide-semiconductor (CMOS) driver and fan-out circuitries. The off-sited bonding contacts and minimized bonding force produced very high yield of the hybridization process without causing damage to the VCSEL mesas. The hybridized devices were further mounted either on printed circuit board (PCB) or in 68-pin pin-grid-array (PGA) packages. The transparent sapphire substrate allowed optical outputs from the top-emitting VCSEL arrays to transmit directly through without additional substrate removal procedure. Lasing thresholds below 250 /spl mu/A for 850 nm VCSELs and 800 /spl mu/A for 980 nm VCSEL were found at room temperature. The oxide confinement apertures of VCSELs were measured to be around 6 /spl mu/m in diameter. High-speed data transmission demonstrated a bandwidth of up to 1 Gbits/s per channel for these hybridized VCSEL transmitters. 相似文献
140.
Corrosion of 316L stainless welds in urea synthesis systems is not due to preferential attack of ferrite, but to dissolution of sigma phase formed from ferrite by successive weld passes. Proper element balancing of 316L filler metal, or welding with Alloy 20 or a high nitrogen 316 weld eliminates this problem. 相似文献