全文获取类型
收费全文 | 1845篇 |
免费 | 32篇 |
专业分类
电工技术 | 17篇 |
综合类 | 3篇 |
化学工业 | 152篇 |
金属工艺 | 15篇 |
机械仪表 | 57篇 |
建筑科学 | 43篇 |
能源动力 | 46篇 |
轻工业 | 69篇 |
水利工程 | 10篇 |
无线电 | 152篇 |
一般工业技术 | 220篇 |
冶金工业 | 904篇 |
原子能技术 | 4篇 |
自动化技术 | 185篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 24篇 |
2019年 | 20篇 |
2018年 | 20篇 |
2017年 | 30篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 69篇 |
2012年 | 42篇 |
2011年 | 67篇 |
2010年 | 44篇 |
2009年 | 35篇 |
2008年 | 48篇 |
2007年 | 48篇 |
2006年 | 46篇 |
2005年 | 45篇 |
2004年 | 39篇 |
2003年 | 36篇 |
2002年 | 30篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 49篇 |
1998年 | 284篇 |
1997年 | 186篇 |
1996年 | 128篇 |
1995年 | 73篇 |
1994年 | 48篇 |
1993年 | 51篇 |
1992年 | 18篇 |
1991年 | 21篇 |
1990年 | 15篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 27篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1978年 | 2篇 |
1977年 | 27篇 |
1976年 | 43篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有1877条查询结果,搜索用时 0 毫秒
51.
RA Barton IR Storch VP Adiga R Sakakibara BR Cipriany B Ilic SP Wang P Ong PL McEuen JM Parpia HG Craighead 《Nano letters》2012,12(9):4681-4686
By virtue of their low mass and stiffness, atomically thin mechanical resonators are attractive candidates for use in optomechanics. Here, we demonstrate photothermal back-action in a graphene mechanical resonator comprising one end of a Fabry-Perot cavity. As a demonstration of the utility of this effect, we show that a continuous wave laser can be used to cool a graphene vibrational mode or to power a graphene-based tunable frequency oscillator. Owing to graphene's high thermal conductivity and optical absorption, photothermal optomechanics is efficient in graphene and could ultimately enable laser cooling to the quantum ground state or applications such as photonic signal processing. 相似文献
52.
Digital twin (DT) has garnered attention in both industry and academia. With advances in big data and internet of things (IoTs) technologies, the infrastructure for DT implementation is becoming more readily available. As an emerging technology, there are both potential and challenges. DT is a promising methodology to leverage the modern data explosion to aid engineers, managers, healthcare experts and politicians in managing production lines, patient health and smart cities by providing a comprehensive and high fidelity monitoring, prognostics and diagnostics tools. New research and surveys into the topic are published regularly, as interest in this technology is high although there is a lack of standardization to the definition of a DT. Due to the large amount of information present in a DT system and the dual cyber and physical nature of a DT, augmented reality (AR) is a suitable technology for data visualization and interaction with DTs. This paper seeks to classify different types of DT implementations that have been reported, highlights some researches that have used AR as data visualization tool in DT, and examines the more recent approaches to solve outstanding challenges in DT and the integration of DT and AR.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00375-w 相似文献
53.
Modality-independent elastography (MIE) is a method of elastography that reconstructs the elastic properties of tissue using images acquired under different loading conditions and a biomechanical model. Boundary conditions are a critical input to the algorithm and are often determined by time-consuming point correspondence methods requiring manual user input. This study presents a novel method of automatically generating boundary conditions by nonrigidly registering two image sets with a demons diffusion-based registration algorithm. The use of this method was successfully performed in silico using magnetic resonance and X-ray-computed tomography image data with known boundary conditions. These preliminary results produced boundary conditions with an accuracy of up to 80% compared to the known conditions. Demons-based boundary conditions were utilized within a 3-D MIE reconstruction to determine an elasticity contrast ratio between tumor and normal tissue. Two phantom experiments were then conducted to further test the accuracy of the demons boundary conditions and the MIE reconstruction arising from the use of these conditions. Preliminary results show a reasonable characterization of the material properties on this first attempt and a significant improvement in the automation level and viability of the method. 相似文献
54.
Fuller-Rowell Thomas E.; Burrow Anthony L.; Ong Anthony D. 《Canadian Metallurgical Quarterly》2011,47(6):1608
The current study considered the influence of the 2008 presidential election on the racial identity of African American college students (Mage = 19.3 years; 26.3% male). The design of the study consisted of 2 components: longitudinal and daily. The longitudinal component assessed 3 dimensions of racial identity (centrality, private regard, and public regard) 2 weeks before and 5 months after the election, and the daily diary component assessed racial identity and identity exploration on the days immediately before and after the election. Daily items measuring identity exploration focused on how much individuals thought about issues relating to their race. Analyses considered the immediate effects of the election on identity exploration and the extent to which changes in exploration were shaped by racial identity measured prior to the election. We also considered immediate and longer term changes in racial identity following the election and the extent to which longer term changes were conditioned by identity exploration. Findings suggest that the election served as an “encounter” experience (Cross, 1991, 1995, pp. 60–61), which led to increases in identity exploration. Moreover, analyses confirmed that changes in identity exploration were most pronounced among those with higher levels of racial centrality. Results also suggest that the election had both an immediate and a longer term influence on racial identity, which in some instances was conditioned by identity exploration. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
55.
Feng Mao James A. Gaunt Chu-Lin Cheng Say Kee Ong 《Canadian Metallurgical Quarterly》2011,137(2):137-145
Organic contaminants may permeate through plastic pipes in water distribution systems and adversely affect the quality of drinking water. In this study, we developed a microscopic visualization technique to investigate the permeation of common organic contaminants (benzene, toluene, ethylbenzene, xylene, and trichloroethene) through polyvinyl chloride (PVC) pipes. By observing the propagation of organic moving fronts in the pipe materials with a light microscope, the technique was able to predict the permeation breakthrough times through PVC pipes that were determined in the pipe-bottle test. The advance of an organic moving front was found to be linearly dependent on the square-root of time and the propagation rate increased with an increase in the external organic chemical activity. Permeation of organic mixtures into PVC pipes was found to be additive in proportion to the permeation rates and volume percents of each component. In combination with a 2-year pipe-bottle test for PVC pipes exposed to premium gasoline, mathematical extrapolations based on the microscopic visualization tests predicted that PVC pipe are likely to resist permeation by commercial gasoline for the service life of the pipe. 相似文献
56.
S. Baunack D. Balaguer Ríos L. Capozza J. Diefenbach R. Frascaria B. Glser D.v. Harrach Y. Imai R. Kothe R. Kunne J.H. Lee F.E. Maas M.C. Mora Espí M. Morlet S. Ong E. Schilling J. van de Wiele C. Weinrich 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,640(1):561
57.
Pavithra Shyamsunder Shree Pooja Sridharan Vikas Madan Pushkar Dakle Cao Zeya Deepika Kanojia Wee-Joo Chng S. Tiong Ong H. Phillip Koeffler 《International journal of molecular sciences》2022,23(3)
Multiple myeloma (MM) is a hematological disease marked by abnormal growth of B cells in bone marrow. Inherent chromosomal instability and DNA damage are major hallmarks of MM, which implicates an aberrant DNA repair mechanism. Studies have implicated a role for CDK12 in the control of expression of DNA damage response genes. In this study, we examined the effect of a small molecule inhibitor of CDK12–THZ531 on MM cells. Treatment of MM cells with THZ531 led to heightened cell death accompanied by an extensive effect on gene expression changes. In particular, we observed downregulation of genes involved in DNA repair pathways. With this insight, we extended our study to identify synthetic lethal mechanisms that could be exploited for the treatment of MM cells. Combination of THZ531 with either DNA-PK inhibitor (KU-0060648) or PARP inhibitor (Olaparib) led to synergistic cell death. In addition, combination treatment of THZ531 with Olaparib significantly reduced tumor burden in animal models. Our findings suggest that using a CDK12 inhibitor in combination with other DNA repair inhibitors may establish an effective therapeutic regimen to benefit myeloma patients. 相似文献
58.
The migration of endocrine-disrupting di-(2-ethylhexyl) phthalate (DEHP) poses a serious threat to public health and the environment. In this study, we successfully prepared a plasticizerwith reduced DEHP migration by directly incorporating 2,3,6-per-O-benzoyl-beta-cyclodextrin (Bz-beta-CD) into DEHP. Bz-beta-CD was prepared by esterification between the hydroxyl groups of beta-CD and benzoyl chloride. The presence of this cyclodextrin is expected to facilitate formation of stable complexes through pi-pi association with DEHP molecules. The flexible PVC was prepared with a gelation-fusion process that uses the prepared migration-resistant plasticizer, and its properties (flexibility, thermal stability, and clarity) were evaluated by carrying out DSC and tensile testing, TGA, and haze testing, respectively. No significant changes in the physical properties of the flexible PVC were observed when Bz-beta-CD was added. DEHP migration tests were carried out for the flexible PVC according to the ISO 3826:1993(E) test method, and the quantity of migrated DEHP was then determined with UV-vis spectroscopy. It was found that the addition of Bz-beta-CD decreases the levels of DEHP migration from the flexible PVC samples by almost 40%. We investigated the molecular interaction between Bz-beta-CD and DEHP using molecular mechanics simulations, and we conclude that this reduction in DEHP migration is due to the formation of stabilized pi-pi attractive association and inclusion complexes of Bz-beta-CD and DEHP in flexible PVC. 相似文献
59.
Rats were intravenously injected with a mixture of free (14-14C) erucic acid (22∶1) and (9–103H) oleic acid (18∶1). After 2, 4, 8, 16, and 30 min, radioactivity was examined in blood, liver, heart, kidneys, and spleen.
Free (14C) 22∶1 disappeared from the blood more rapidly than free (14C) 18∶1 between 0 and 8 min. Incorporation of label into triglycerides only appeared after 16 min and at 30 min they represented
4% of the injected radioactivity. In this fraction, 63% of14C radioactivity was present as 18∶1 and not as the original 22∶1, while almost all3H radioactivity was recovered as unchanged 18∶1. At all times studied, the majority of radioactivity was found in the liver,
primarily as triglycerides (60% of radioactivity in total lipids) and as phospholipids (20–30%).14C was present in nearly the same proportion as3H (13% of injected radioactivity after only 2 min, 11% at 30 min).14C radioactivity was contained in 18∶1 in higher proportion than 22∶1 (45% in triglycerides, 65% in phospholipids). Since labeled
triglycerides of blood, rich in (14C) 18∶1, mainly originate from the liver triglycerides, it appears that 18∶1 is the major form of utilization of 22∶1 in the
tissues after its conversion in liver. In the other organs tested, radioactivity was found 10–15 times lower than in liver.
In the heart,14C was 3 to 4 times higher than3H. More than 80% was recovered as 22∶1 in triglycerides. In spleen and kidneys, the14C:3H ratio was particularly high in free fatty acids and monoglycerides. In kidneys, 60% of14C was present as nervonic acid (24∶1) in monoglycerides and 40% in phospholipids, suggesting that the mononervonin formed
was used for phospholipid biosynthesis.
A preliminary report of this work was presented at the 10th International Congress of Nutrition, Kyoto, Japan, August 1975. 相似文献
60.
Connie Tee Goh Michael Kah Ong Teoh Andrew Beng Jin 《Multimedia Tools and Applications》2018,77(21):28457-28482
Multimedia Tools and Applications - Gait recognition has become popular due to the rising demand for nonintrusive biometrics. At its nascent stage of development, gait recognition faces a number of... 相似文献