全文获取类型
收费全文 | 7361篇 |
免费 | 517篇 |
国内免费 | 217篇 |
专业分类
电工技术 | 295篇 |
综合类 | 473篇 |
化学工业 | 1299篇 |
金属工艺 | 339篇 |
机械仪表 | 378篇 |
建筑科学 | 489篇 |
矿业工程 | 146篇 |
能源动力 | 244篇 |
轻工业 | 672篇 |
水利工程 | 90篇 |
石油天然气 | 232篇 |
武器工业 | 26篇 |
无线电 | 847篇 |
一般工业技术 | 1022篇 |
冶金工业 | 535篇 |
原子能技术 | 75篇 |
自动化技术 | 933篇 |
出版年
2024年 | 14篇 |
2023年 | 97篇 |
2022年 | 128篇 |
2021年 | 229篇 |
2020年 | 179篇 |
2019年 | 205篇 |
2018年 | 197篇 |
2017年 | 187篇 |
2016年 | 231篇 |
2015年 | 228篇 |
2014年 | 252篇 |
2013年 | 403篇 |
2012年 | 393篇 |
2011年 | 434篇 |
2010年 | 379篇 |
2009年 | 340篇 |
2008年 | 365篇 |
2007年 | 351篇 |
2006年 | 273篇 |
2005年 | 256篇 |
2004年 | 298篇 |
2003年 | 356篇 |
2002年 | 506篇 |
2001年 | 399篇 |
2000年 | 219篇 |
1999年 | 177篇 |
1998年 | 183篇 |
1997年 | 161篇 |
1996年 | 113篇 |
1995年 | 99篇 |
1994年 | 75篇 |
1993年 | 46篇 |
1992年 | 47篇 |
1991年 | 39篇 |
1990年 | 29篇 |
1989年 | 25篇 |
1988年 | 15篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1974年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有8095条查询结果,搜索用时 406 毫秒
21.
The transmission mode of holographic polymer‐dispersed liquid crystals (HPDLCs) was developed an under electric field. It is reported that orientation of LC molecules under an electric field induces orientation of oligomer molecules giving rise to low off‐state diffraction and small grating shrinkage. Copyright © 2005 Society of Chemical Industry 相似文献
22.
RobetKrause KhoiTran JohnConstantino 《世界电子元器件》2004,(4):31-32
电动汽车常被喻作“归来的孩子”,因为这项技术在多年前进入市场后便一直沉寂,直至最近才再次活跃起来。其实,电动汽车早于1835年首次于美国出现,到1899年,纽约市接近90%的出租车都是由电力驱动。然而,当电力启动器和内燃机变得完善时,电动汽车的使用就迅速衰退。随着如今对环境保护的关注,由燃烧碳氢化合物造成的污染,加之汽油成本高升的影响,再次 相似文献
23.
24.
SM Kornblau E Estey T Madden HT Tran S Zhao U Consoli V Snell G Sanchez-Williams H Kantarjian M Keating RA Newman M Andreeff 《Canadian Metallurgical Quarterly》1997,15(5):1796-1802
PURPOSE: Expression of the multidrug resistance gene (MDR1) p170 protein is frequent in leukemic blasts from patients with relapsed acute myelogenous leukemia (AML). A phase I study using the nonimmunosuppressive MDR1 blocker SDZ PSC-833 (PSC) in combination with mitoxantrone (MITO) and etoposide (VP) was performed. PATIENTS AND METHODS: Starting doses (LVL0) of MITO (3.25 mg/m2/d on days 1 and 3 to 6) and VP (210 mg/m2/d on days 1 and 3 to 5) were 40% of the maximal-tolerated dose (MTD) from a prior study. A 1.5-mg/kg loading dose of PSC was followed by a 120-hour continuous infusion of 10 mg/kg/d on days 2 to 6. Blood samples for PSC, MITO, and VP pharmacokinetics (PK) were taken on days 1 and 3, and samples for MDR1 expression were taken on day 0. RESULTS: Severe mucositis developed in all patients at LVL0; therefore, MITO and VP doses were reduced to 2.5 and 170 mg/m2 (LVL-1) for the next seven patients, and this dose proved to be MTD. All LVL0 and three LVL-1 patients had transient elevations in the serum bilirubin level to > or = 4 mg/dL. Serum creatinine level increased to greater than 2 mg/dL in one case. There were no other grade 3 or 4 nonhematologic toxicities observed. The peripheral blood was cleared of leukemia in three LVL0 and four LVL-1 patients. The marrow was cleared of leukemic cells in one LVL0 and five LVL-1 patients, and a significant reduction in marrow leukemic infiltrate was observed in eight of 10. No patient achieved complete remission (CR), and all died of progressive disease (n = 8) or infection (n = 2). MDR1 expression was detected by fluorescent-activated cell sorter (FACS) analysis in five of seven cases. An elevated MDR1 mRNA level was detected by quantitative polymerase chain reaction (Q-PCR) in six of eight cases studied. Clearing of leukemia cells from the marrow occurred in four of six MDR1-positive and one of three MDR1-negative patients. Despite the fact that LVL0 doses had to be reduced due to toxicity, coadministration of PSC did not produce a consistent effect on MITO PK; however, it did repeatedly lead to increased levels of VP in the serum. CONCLUSION: We conclude that PSC-MITO-VP is a tolerable regimen with antileukemic activity. Addition of PSC necessitated a 66% reduction in MITO and VP doses from a prior study without PSC. 相似文献
25.
冷成型模具低温锌系磷化 总被引:4,自引:1,他引:3
研制出适用于冷成型模具高硬度表面的低温锌系磷化工艺。其中磷化液含Zn(H2 PO4 ) 2 ·2H2 O 6 0g/L ,Zn(NO3) 2 ·6H2 O 90g/L ,NaNO2 1.5g/L ,稀土促进剂 0~ 1.0g/L ,游离酸度 4~ 6点 ,总酸度 70~ 75点。该磷化液在 4 0℃下 ,处理 30~ 4 0min后可获得厚约 10 μm的磷化膜。性能测试表明 ,其减摩、润滑性能良好 ,摩擦系数约降 0 .1,与未处理试样相比磨损量下降 96 % ,附着力 1级。 相似文献
26.
27.
28.
29.
V.J. Logeeswaran F.E.H. Tay M.L. Chan F.S. Chau Y.C. Liang 《Analog Integrated Circuits and Signal Processing》2003,37(1):17-33
In this paper, the response to the first harmonic component (2f) of the electrostatic force in single terminal driven electrostatic comb-drive and parallel-plate drive was used as a signal to extract device parameters, namely, the Q-factor and resonant frequency instead of the fundamental (1f) resonance response. It is shown that the difficulty in motional measurement due to electrical cross-talk (parasitics) using 1f measurement can be overcome with a higher signal-to-noise ratio of the 2f signal. Both atmospheric (low-Q) and reduced pressure environment were investigated using off-chip electronics and lock-in amplifier. The measurements were done on the electrostatic comb-drive and capacitive parallel plate sensing plates that form the two core modules of a yaw rate sensor (dual-axis resonator). The effects of AC and DC bias voltages on the measured response have been investigated. Experimental amplitude and phase response data have been analysed using the Lorentzian curve-fit, Resonance Curve Area (RCA) method, the half-power bandwidth method (3 dB) and the Nyquist plot for data fitting and determination of the Q-factor and resonance frequency. 相似文献
30.