全文获取类型
收费全文 | 11271篇 |
免费 | 948篇 |
国内免费 | 222篇 |
专业分类
电工技术 | 381篇 |
综合类 | 342篇 |
化学工业 | 2188篇 |
金属工艺 | 402篇 |
机械仪表 | 483篇 |
建筑科学 | 717篇 |
矿业工程 | 263篇 |
能源动力 | 246篇 |
轻工业 | 1264篇 |
水利工程 | 166篇 |
石油天然气 | 302篇 |
武器工业 | 17篇 |
无线电 | 1152篇 |
一般工业技术 | 1739篇 |
冶金工业 | 1134篇 |
原子能技术 | 97篇 |
自动化技术 | 1548篇 |
出版年
2024年 | 41篇 |
2023年 | 159篇 |
2022年 | 272篇 |
2021年 | 403篇 |
2020年 | 306篇 |
2019年 | 324篇 |
2018年 | 394篇 |
2017年 | 381篇 |
2016年 | 421篇 |
2015年 | 413篇 |
2014年 | 547篇 |
2013年 | 751篇 |
2012年 | 654篇 |
2011年 | 783篇 |
2010年 | 625篇 |
2009年 | 572篇 |
2008年 | 626篇 |
2007年 | 562篇 |
2006年 | 494篇 |
2005年 | 451篇 |
2004年 | 314篇 |
2003年 | 291篇 |
2002年 | 298篇 |
2001年 | 224篇 |
2000年 | 232篇 |
1999年 | 227篇 |
1998年 | 201篇 |
1997年 | 180篇 |
1996年 | 174篇 |
1995年 | 132篇 |
1994年 | 139篇 |
1993年 | 99篇 |
1992年 | 97篇 |
1991年 | 66篇 |
1990年 | 76篇 |
1989年 | 67篇 |
1988年 | 51篇 |
1987年 | 45篇 |
1986年 | 42篇 |
1985年 | 36篇 |
1984年 | 40篇 |
1983年 | 31篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 26篇 |
1976年 | 19篇 |
1975年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
To examine the separate effects of viscosity and sweetness on astringency, aqueous solutions of grape seed tannin (GST) were thickened with carboxymethyl cellulose (CMC) from 2 to 45 cP (experiment 1) or sweetened with 0 to 1.8 g/L aspartame (experiment 2). Trained subjects continuously rated astringency and bitterness in duplicate. Subjects were categorized by the salivary flow induced by citric acid and ability to taste n-propyl thiouracil (PROP). In experiment 1, maximum intensity and total duration of astringency were significantly decreased as viscosity rose, although time to maximum intensity of astringency was not affected. Maximum intensity and total duration of bitterness were not significantly affected by increasing viscosity; however, the onset of bitterness was significantly delayed. In experiment 2, increasing sweetness had no affect on any astringency parameter, although maximum intensity of bitterness was significantly decreased. Neither PROP nor salivary flow-status had any effect on perception of bitterness or astringency in either experiment. 相似文献
62.
63.
Yoon-Ha Jeong Seong-Kue Jo Bong-Hoon Lee Sugano T. 《Electron Device Letters, IEEE》1995,16(3):109-111
High performance enhancement mode InP MISFET's have been successfully fabricated by using the sulfide passivation for lower interface states and with photo-CVD grown P3N5 film used as gate insulator. The MISFET's thus fabricated exhibited exhibited pinch-off behavior with essentially no hysteresis. Furthermore the device showed a superior stability of drain current. Specifically under the gate bias of 2 V for 104 seconds the room temperature drain current was shown to reduce from the initial value merely by 2.9% at the drain voltage of 4 V. The effective electron mobility and extrinsic transconductance are found to be about 2300 cm 2/V·s and 2.7 mS/mm, respectively. The capacitance-voltage characteristics of the sulfide passivated InP MIS diodes show little hysteresis and the minimum density of interface trap states as low as 2.6×1014/cm2 eV has been attained 相似文献
64.
自由电子激光的小型化研究 总被引:2,自引:0,他引:2
本文通过对自由电子激光输出波长的分析,指出了自由电子激光小型化的研究方向─-微型摆动器的研究。在分析了小周期摆动器研究现状的基础上,提出了电流摆动器。它不但具有与静磁摆动器相同的效果,而且它的周期可以任意调节。因而,它便于控制。最后,还指出了有待进一步研究的问题。 相似文献
65.
Mueser Kim T.; Bellack Alan S.; Wade Julie H.; Sayers Steven L.; Tierney Ann; Haas Gretchen 《Canadian Metallurgical Quarterly》1993,102(3):339
Examined social skills and social perception of 48 schizophrenia/schizoaffective disorder patients (aged 18–55 yrs) in response to negative affect as a function of family expressed emotion (EE). Ss participated in a role-play test, a social perception test, and a problem-solving discussion with a family member and were assessed on several measures of symptomatology. EE of family members was evaluated with the Camberwell Family Interview. On the role-play test, Ss with less critical relatives became more assertive in response to increased negative affect from a confederate portraying either a family member or friend, but Ss with highly critical relatives did not. Ss with highly critical relatives were also less assertive when confronted with negative affect from a confederate portraying a family member rather than a friend. The behaviors of both relatives and Ss during a family problem-solving interaction were related to the EE dimensions of criticism, emotional overinvolvement, and warmth. Patient gender was also related to family problem solving but was independent of EE. S's ratings of affect on a videotaped social perception task were not related to family EE, and there were few differences in psychopathology between Ss with high and low EE relatives.… (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
66.
以单片机8031 为核心组成的采集、保护和通信模块,通过RS485 的连接,与486 工控微机构成了分布式35 kV 变电站的自控系统,实现变电站的计量、保护和控制等功能,以达到变电站的无人值守或少人值守。 相似文献
67.
粘结剂是粘钢加固技术的关键材料,通过对粘结剂的试验研究,得到了粘结剂的拉压试验曲线与材料力学指标以及粘附于各种标号混凝土时,粘结层的抗剪强度;并且还进行了粘结剂的短期流变试验。 相似文献
68.
The purpose of this study was to examine the relationships between computer use, identity formation, and self-esteem among Black and White emerging adult females. One hundred 56 female college students participated in this study by completing a survey that included the Internet/Computer Use Questionnaire, the Ego Identity Process Questionnaire, and the Rosenberg Self Esteem Scale. Racial differences were found between Black and White females with regard to perceived problematic use of the Internet and use of the computer for communication and use of the Internet for schoolwork. In addition, differences between Black and White females were found between identity formation and problematic use of the Internet and between self-esteem and type of use of the Internet. These findings were discussed in relation to future research and interventions. 相似文献
69.
In order to investigate the galvanic anodic protection (GAP) of ferrous metals (such as 410, 304 and 316 stainless steels) in acid solutions by doped polyaniline (PANi), separate doped PANi powder-pressed electrodes with different surface areas (the area ratio of the PANi electrode to stainless steel is between 1:1 and 1:2) have been prepared. These were coupled with ferrous metal in the following solutions: 5 M sulphuric acid, 5 M phosphoric acid and industrial phosphoric acid (containing 5 M phosphoric acid and 0.05% chloride ion) to construct a galvanic cell, in which PANi is cathode while ferrous metal is anode. The results indicate that a PANi electrode with sufficient area can provide corrosion protection to stainless steel in these acidic solutions. A pilot scale coupling experiment was carried out. The results indicate that PANi is a promising material as an electrode for the anodic protection of ferrous metals in acidic solutions in industrial situations. 相似文献
70.
An overview of FDA medical device regulation as it relates to deep brain stimulation devices. 总被引:1,自引:0,他引:1
Carlos Pe?a Kristen Bowsher Ann Costello Robert De Luca Sara Doll Khan Li Marie Schroeder Theodore Stevens 《IEEE transactions on neural systems and rehabilitation engineering》2007,15(3):421-424
The United States Food and Drug Administration (FDA) is charged with assuring the safety and effectiveness of a variety of medical products and the FDA's Center for Devices and Radiological Health is responsible for premarket and postmarket regulation of medical devices. In this paper, we review--from device classification and clinical studies to the final marketing application--FDA's premarket requirements and postmarket requirements as they relate to deep brain stimulation devices. 相似文献