全文获取类型
收费全文 | 50739篇 |
免费 | 4292篇 |
国内免费 | 2194篇 |
专业分类
电工技术 | 2869篇 |
技术理论 | 3篇 |
综合类 | 2869篇 |
化学工业 | 8278篇 |
金属工艺 | 2258篇 |
机械仪表 | 2478篇 |
建筑科学 | 3171篇 |
矿业工程 | 907篇 |
能源动力 | 1387篇 |
轻工业 | 4406篇 |
水利工程 | 918篇 |
石油天然气 | 1674篇 |
武器工业 | 360篇 |
无线电 | 6103篇 |
一般工业技术 | 6767篇 |
冶金工业 | 4925篇 |
原子能技术 | 573篇 |
自动化技术 | 7279篇 |
出版年
2024年 | 231篇 |
2023年 | 772篇 |
2022年 | 1454篇 |
2021年 | 1873篇 |
2020年 | 1395篇 |
2019年 | 1273篇 |
2018年 | 1410篇 |
2017年 | 1466篇 |
2016年 | 1419篇 |
2015年 | 1673篇 |
2014年 | 2137篇 |
2013年 | 2880篇 |
2012年 | 2802篇 |
2011年 | 3155篇 |
2010年 | 2638篇 |
2009年 | 2576篇 |
2008年 | 2544篇 |
2007年 | 2532篇 |
2006年 | 2362篇 |
2005年 | 1910篇 |
2004年 | 1615篇 |
2003年 | 1834篇 |
2002年 | 2341篇 |
2001年 | 2008篇 |
2000年 | 1225篇 |
1999年 | 1111篇 |
1998年 | 1747篇 |
1997年 | 1227篇 |
1996年 | 969篇 |
1995年 | 701篇 |
1994年 | 544篇 |
1993年 | 520篇 |
1992年 | 360篇 |
1991年 | 241篇 |
1990年 | 209篇 |
1989年 | 197篇 |
1988年 | 174篇 |
1987年 | 146篇 |
1986年 | 137篇 |
1985年 | 171篇 |
1984年 | 102篇 |
1983年 | 105篇 |
1982年 | 94篇 |
1981年 | 103篇 |
1980年 | 103篇 |
1979年 | 63篇 |
1977年 | 100篇 |
1976年 | 198篇 |
1975年 | 53篇 |
1973年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Luginbuhl P. Collins S.D. Racine G.-A. Gretillat M.-A. De Rooij N.F. Brooks K.G. Setter N. 《Journal of microelectromechanical systems》1997,6(4):337-346
The fabrication using silicon micromachining and characterization of an acoustic Lamb wave actuator is presented. The intended use of the device is for mass transport and sensor applications. The device consists of dual interdigitated transducers patterned on a thin-film composite membrane of silicon nitride, platinum, and a sol-gel-derived piezoelectric ceramic (PZT) thin film. The acoustic properties of the device are presented along with preliminary applications to mechanical transport and liquid delivery systems. Improved acoustic signals and improved mass transport are achieved with PZT over present Lamb wave devices utilizing ZnO or AlN as the piezoelectric transducer 相似文献
92.
A Nu?ez C De la Roza ML Rodrigo-Angulo W Bu?o F Reinoso-Suárez 《Canadian Metallurgical Quarterly》1997,754(1-2):1-11
This study analyses the relationship between the use of rotating instruments, the production of a smear layer and the presence of alterations to enamel microstructures. The rotating instruments used were carbide (8-12 blade) and diamond tipped (30-15 m) cutters. Cavities were made in extracted teeth. Subsequently, half the sample was analysed using the rugosimeter before and after the application of ortophosphoric acid at 35% for 15 and the other half suing a Scansion Electronic microscope (SEM). The results obtained showed on the one hand that carbide cutters leave a smoother surfacer than diamond tipped cutters, and on the other that the smear layer is eliminated better by carbide cutters compared to diamond tipped cutters. Moreover, there are no major traumatic-type alterations at the level of the enamel affecting the microstructure after the use of carbide cutters. 相似文献
93.
从冷却曲线上相变段倾角最小原则出发,研究了新型激冷剂的配比与热分析法检测铸铁成分精度的关系,实验结果表明,能使相变段倾角最小的成分配比,也能提高对铸铁成分的热分析和检测精度。 相似文献
94.
Analysis of Combined Systems of Two Endoreversible Engines 总被引:3,自引:0,他引:3
A single endoreversible engine can operate as a cooler, a true heat engine, a heat pump, or a refrigerator. We investigate how many different modes of operation a combined system of two endoreversible engines may display. Special attention is paid to the independent combined system which neither consumes nor supplies power. 相似文献
95.
JA Alaejos Fuentes T López-Alburquerque J De Portugal Alvarez 《Canadian Metallurgical Quarterly》1997,14(5):239-240
We report a 20-year-old man affected by glycogenosis type III with distal muscle weakness, more severe in distal leg muscles. The electromyogram showed myopathic features. Nerve conduction studies and central motor conduction after magnetic stimulation of the brain were normal. Our results suggest that there is no involvement of central motor pathways in this disease. 相似文献
96.
97.
本文应用常规的守恒方程及湍流模型,对二维池内热分层流动建立了数学模型,并在Patankar的压力校正法基础上对该数学模型进行了数值计算,计算中的差分格式为乘方格式、一阶迎风、二阶迎风和QUICK。通过与实验的比较分析,建议计算应采用QUICK格式,并在进行风格独立性试验的基础上使用加密网络。 相似文献
98.
AM De Mattos MA Head J Everett J Hosenpud R Hershberger A Cobanoglu G Ott R Ratkovec DJ Norman 《Canadian Metallurgical Quarterly》1994,57(4):626-630
To determine if cardiac allograft outcome is improved among patients with fewer HLA-DR mismatches with their donors, we studied 132 recipients of a primary cardiac allograft who were transplanted between December 1985 and December 1991. These recipients and their donors all had high-confidence-level serological HLA-DR typing, previously shown to correlate highly with DNA DR typing. Patients were divided in two groups based on the HLA-DR mismatch with their donors. Group I consisted of 78 patients with 1 or zero DR mismatch and group II of 54 patients with 2 DR mismatches. Allograft outcome measurements included incidence of moderate rejection, incidence of allograft vasculopathy at 12 months, cardiac function measured as left ventricular ejection fraction (LVEF) and cardiac index (CI), and actuarial graft survival up to 7 years. Groups I and group II were not different with regard to recipient age, donor age, ischemia time, pulmonary vascular resistance, sex, or PRA greater than 0%. Group II had a higher incidence of moderate rejection on the first-week biopsy (47% vs. 25%, P = 0.019), and during the first month (84% vs. 58%, P = 0.006), but no difference was found in frequency of rejection from months 2 to 12. LVEF was not different in the groups at any point. CI was better in group I at 12 months (2.76 vs. 2.5, P = 0.03). No statistically significant difference was found in incidence of allograft vasculopathy (17% vs. 26%, P = 0.204). Actual graft survival at 1 year was better for group I (91% vs. 74%, P = 0.008), and actuarial graft survival at 6 years also favored group I (76% vs. 56%, P = 0.04). Using high-confidence-level serological HLA-DR typing assignments we demonstrated that HLA-DR mismatching correlates highly with cardiac allograft outcome. Implications are that heart transplant survival could be improved if prospective matching were feasible and prioritized or if immunosuppression were tailored to the HLA-DR match. 相似文献
99.
100.