全文获取类型
收费全文 | 7570篇 |
免费 | 151篇 |
国内免费 | 39篇 |
专业分类
电工技术 | 93篇 |
综合类 | 5篇 |
化学工业 | 1000篇 |
金属工艺 | 123篇 |
机械仪表 | 199篇 |
建筑科学 | 97篇 |
能源动力 | 193篇 |
轻工业 | 235篇 |
水利工程 | 27篇 |
石油天然气 | 5篇 |
无线电 | 905篇 |
一般工业技术 | 915篇 |
冶金工业 | 3005篇 |
原子能技术 | 25篇 |
自动化技术 | 933篇 |
出版年
2024年 | 9篇 |
2023年 | 31篇 |
2022年 | 111篇 |
2021年 | 108篇 |
2020年 | 35篇 |
2019年 | 56篇 |
2018年 | 66篇 |
2017年 | 76篇 |
2016年 | 103篇 |
2015年 | 103篇 |
2014年 | 178篇 |
2013年 | 375篇 |
2012年 | 270篇 |
2011年 | 323篇 |
2010年 | 232篇 |
2009年 | 266篇 |
2008年 | 271篇 |
2007年 | 241篇 |
2006年 | 231篇 |
2005年 | 197篇 |
2004年 | 165篇 |
2003年 | 163篇 |
2002年 | 126篇 |
2001年 | 116篇 |
2000年 | 86篇 |
1999年 | 174篇 |
1998年 | 1051篇 |
1997年 | 556篇 |
1996年 | 401篇 |
1995年 | 228篇 |
1994年 | 216篇 |
1993年 | 236篇 |
1992年 | 75篇 |
1991年 | 78篇 |
1990年 | 65篇 |
1989年 | 65篇 |
1988年 | 83篇 |
1987年 | 68篇 |
1986年 | 54篇 |
1985年 | 49篇 |
1984年 | 28篇 |
1983年 | 25篇 |
1982年 | 23篇 |
1981年 | 26篇 |
1980年 | 41篇 |
1979年 | 9篇 |
1978年 | 16篇 |
1977年 | 70篇 |
1976年 | 142篇 |
1974年 | 8篇 |
排序方式: 共有7760条查询结果,搜索用时 484 毫秒
1.
Chen Wen-Kuo Chang Jing-Rong Chen Long-Sheng Hsu Rui-Yang 《Multimedia Tools and Applications》2022,81(6):8317-8347
Multimedia Tools and Applications - With the advancement of technology and the spread of the COVID19 epidemic, learning can no longer only be done through face-to-face teaching. Numerous digital... 相似文献
2.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
3.
Ping-Chi Hsu Jia-Ying Jhong Li-Ping Huang Kuo-Hsin Lee Hsin-Pao Chen Yue-Leon Guo 《International journal of molecular sciences》2021,22(8)
Di(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in the manufacture of polyvinylchloride plastics and has been associated with concerns regarding male reproductive toxicity. In this study, we hypothesized that maternal exposure to DEHP induces transgenerational inheritance of adult-onset adverse reproductive outcomes through the male germline in the F1, F2, and F3 generations of male offspring. Pregnant rats were treated with 5 or 500 mg of DEHP/kg/day through gavage from gestation day 0 to birth. The offspring body weight, anogenital distance (AGD), anogenital index (AGI), sperm count, motility, and DNA fragmentation index (DFI) were measured for all generations. Methyl-CpG binding domain sequencing was performed to analyze sperm DNA methylation status in the F3. DEHP exposure at 500 mg/kg affected AGD, AGI, sperm count, mean DFI, and %DFI in the F1; AGD, sperm count, and mean DFI in the F2; and AGD, AGI, mean DFI, and %DFI in the F3. DEHP exposure at 5 mg/kg affected AGD, AGI, sperm count, and %DFI in the F1; sperm count in the F2; and AGD and AGI in F3. Compared with the control group, 15 and 45 differentially hypermethylated genes were identified in the groups administered 5 mg/kg and 500 mg/kg DEHP, respectively. Moreover, 130 and 6 differentially hypomethylated genes were observed in the groups administered 5 mg/kg and 500 mg/kg DEHP. Overall, these results demonstrated that prenatal exposure to DEHP caused transgenerational epigenetic effects, which may explain the observed phenotypic changes in the male reproductive system. 相似文献
4.
5.
6.
Latchup-free ESD protection design with complementary substrate-triggered SCR devices 总被引:2,自引:0,他引:2
Ming-Dou Ker Kuo-Chun Hsu 《Solid-State Circuits, IEEE Journal of》2003,38(8):1380-1392
The turn-on mechanism of silicon-controlled rectifier (SCR) devices is essentially a current triggering event. While a current is applied to the base or substrate of an SCR device, it can be quickly triggered on into its latching state. In this paper, latchup-free electrostatic discharge (ESD) protection circuits, which are combined with the substrate-triggered technique and an SCR device, are proposed. A complementary circuit style with the substrate-triggered SCR device is designed to discharge both the pad-to-V/sub SS/ and pad-to-V/sub DD/ ESD stresses. The novel complementary substrate-triggered SCR devices have the advantages of controllable switching voltage, adjustable holding voltage, faster turn-on speed, and compatible to general CMOS process without extra process modification such as the silicide-blocking mask and ESD implantation. The total holding voltage of the substrate-triggered SCR device can be linearly increased by adding the stacked diode string to avoid the transient-induced latchup issue in the ESD protection circuits. The on-chip ESD protection circuits designed with the proposed complementary substrate-triggered SCR devices and stacked diode string for the input/output pad and power pad have been successfully verified in a 0.25-/spl mu/m salicided CMOS process with the human body model (machine model) ESD level of /spl sim/7.25 kV (500 V) in a small layout area. 相似文献
7.
The intent of a binomial effect size display (BESD) is to show "the [real-world] importance of [an] effect indexed by a correlation [r]" (R. Rosenthal, 1994, p. 242) by reexpressing this correlation as a success rate difference (SRD) (e.g., treatment group success rate - control group success rate). However, SRDs displayed in BESDs generally overestimate real-world SRDs implied by correlations of (a) dichotomous X and Y variables (φ coefficients), (b) dichotomous X and continuous Y variables (point-biserial coefficients [rphs]). and (c) continuous X and Y variables (rxys). Furthermore, overestimation biases are larger for rxys than for rphs. Differences in the sizes of biases linked to different correlations suggest that BESD SRDs reported for different correlations are not comparable. The stochastic difference index (N. Cliff, 1993: A. Vargha & H. D. Delaney, 2000) is recommended as an alternative to the BESD. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
The aim of this study was to assess the association between the length of maternity leave and the quality of mother-infant interactions; 198 employed mothers of 4-month-old infants were interviewed and videotaped in their homes during a feeding time. Hierarchical multiple regression analyses indicated a direct association between shorter length of leave and more negative affect and behavior in maternal interactions with their infants. Infant and mother stressor/protective variables added significantly in predicting the quality of the mother-infant relationship. There were also significant interaction effects between the length of leave and these variables. Mothers who either reported more depressive symptoms or who perceived their infant as having a more difficult temperament and who had shorter leaves, compared with mothers who had longer leaves, were observed to express less positive affect, sensitivity, and responsiveness in interactions with their infants. The public policy implications of the relation between length of maternity leave, maternal and infant individual differences, and the quality of mother-infant interactions are discussed. 相似文献
9.
MH Hennington AM D'Armini JJ Lemasters TM Egan 《Canadian Metallurgical Quarterly》1996,61(7):1009-1014
In an effort to increase the donor pool for lung transplantation (LTX), we have demonstrated the feasibility of LTX from circulation-arrested cadavers in a canine LTX model. We hypothesized that ventilation of the cadaver lung with alveolar gas (20% O2, 5% CO2, balance N2) (AG) would be superior to ventilation with 100% oxygen (O2) after circulatory arrest of the donor. Twelve mongrel dogs were intubated, heparinized and euthanized by pentothal injection and ventilated with AG (n=6) or O2 (n=6). Four hours later, donor animals underwent sternotomy, and the lungs were flushed with cold modified Euro-Collins solution, harvested, and stored inflated in ice slush. Left lung allotransplantation was performed, and recipients were made dependent o n the transplanted lung by occlusion of the contralateral bronchus and pulmonary artery. Recipient animals were ventilated with an FiO2 of 0.4 and followed for 8 hr. Total ischemic time was 7.9 hr for both groups. Pulmonary edema developed in all recipients of AG lungs; one recipient survived the 8-hr observation period with poor oxygenation. In contrast, three of six recipients of O2-ventilated lungs survived for 8-hr with excellent gas exchange. Specimens of donor lungs before and after transplant were evaluated histologically utilizing trypan blue exclusion as an indicator of cell viability. At the time of organ retrieval 4 hr after death, 6% of cells were nonviable in the O2-ventilated cadaver lungs. Circulation-arrested cadaver lungs ventilated with 100% O2 prior to organ retrieval have superior pulmonary function after transplant compared with lungs ventilated with AG. Ventilation of cadaver lungs with AG induces pulmonary injury in this model. retrieval of donor lungs from circulation-arrested cadavers has potential for increasing the pulmonary donor pool. 相似文献
10.
The Department of Veterans Affairs, Social Work Service has designed, developed and implemented the Social Work Information Management System (SWIMS) which provides for the collection and reporting of both administrative and clinical information. This paper describes the implementation of one component of SWIMS, the automated Social Work Data Base/Assessment. The discussion details the implementation process and discusses issues encountered in the implementation of a computerized documentation system. 相似文献