全文获取类型
收费全文 | 4816篇 |
免费 | 184篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 39篇 |
综合类 | 5篇 |
化学工业 | 1149篇 |
金属工艺 | 82篇 |
机械仪表 | 79篇 |
建筑科学 | 215篇 |
矿业工程 | 20篇 |
能源动力 | 166篇 |
轻工业 | 366篇 |
水利工程 | 35篇 |
石油天然气 | 36篇 |
武器工业 | 2篇 |
无线电 | 430篇 |
一般工业技术 | 804篇 |
冶金工业 | 867篇 |
原子能技术 | 14篇 |
自动化技术 | 696篇 |
出版年
2023年 | 32篇 |
2022年 | 72篇 |
2021年 | 91篇 |
2020年 | 59篇 |
2019年 | 72篇 |
2018年 | 88篇 |
2017年 | 91篇 |
2016年 | 89篇 |
2015年 | 88篇 |
2014年 | 129篇 |
2013年 | 363篇 |
2012年 | 221篇 |
2011年 | 298篇 |
2010年 | 190篇 |
2009年 | 221篇 |
2008年 | 220篇 |
2007年 | 237篇 |
2006年 | 197篇 |
2005年 | 156篇 |
2004年 | 123篇 |
2003年 | 119篇 |
2002年 | 127篇 |
2001年 | 97篇 |
2000年 | 79篇 |
1999年 | 81篇 |
1998年 | 109篇 |
1997年 | 101篇 |
1996年 | 78篇 |
1995年 | 95篇 |
1994年 | 61篇 |
1993年 | 58篇 |
1992年 | 47篇 |
1991年 | 50篇 |
1990年 | 64篇 |
1989年 | 46篇 |
1988年 | 45篇 |
1987年 | 38篇 |
1986年 | 39篇 |
1985年 | 57篇 |
1984年 | 58篇 |
1983年 | 44篇 |
1982年 | 42篇 |
1981年 | 36篇 |
1980年 | 42篇 |
1979年 | 46篇 |
1978年 | 49篇 |
1977年 | 40篇 |
1976年 | 40篇 |
1975年 | 36篇 |
1973年 | 35篇 |
排序方式: 共有5005条查询结果,搜索用时 46 毫秒
991.
A 3D Hybrid of Chemically Coupled Nickel Sulfide and Hollow Carbon Spheres for High Performance Lithium–Sulfur Batteries 下载免费PDF全文
Chao Ye Lei Zhang Chunxian Guo Dongdong Li Anthony Vasileff Haihui Wang Shi‐Zhang Qiao 《Advanced functional materials》2017,27(33)
Lithium–sulfur batteries are a promising next‐generation energy storage device owing to their high theoretical capacity and the low cost and abundance of sulfur. However, the low conductivity and loss of active sulfur material during operation greatly limit the rating capabilities and cycling stability of lithium–sulfur batteries. In this work, a unique sulfur host hybrid material comprising nanosized nickel sulfide (NiS) uniformly distributed on 3D carbon hollow spheres (C‐HS) is fabricated using an in situ thermal reduction and sulfidation method. In the hybrid material, the nanosized NiS provides a high adsorption capability for polysulfides and the C‐HS serves as a physical confinement for polysulfides and also a 3D electron transfer pathway. Moreover, NiS has strong chemical coupling with the C‐HS, favoring fast charge transfer and redox kinetics of the sulfur electrode. With a sulfur loading of up to 2.3 mg cm?2, the hybrid material‐based lithium–sulfur batteries offer a capacity decay as low as 0.013% per cycle and a capacity of 695 mA h g?1 at 0.5 C after 300 cycles. This unique 3D hybrid material with strong chemical coupling provides a promising sulfur host for high performance lithium–sulfur batteries. 相似文献
992.
993.
Miniaturized Flexible Electronic Systems with Wireless Power and Near‐Field Communication Capabilities 下载免费PDF全文
Jeonghyun Kim Anthony Banks Zhaoqian Xie Seung Yun Heo Philipp Gutruf Jung Woo Lee Sheng Xu Kyung‐In Jang Fei Liu Gregory Brown Junghyun Choi Joo Hyun Kim Xue Feng Yonggang Huang Ungyu Paik John A. Rogers 《Advanced functional materials》2015,25(30):4761-4767
A class of thin, lightweight, flexible, near‐field communication (NFC) devices with ultraminiaturized format is introduced, and systematic investigations of the mechanics, radio frequency characteristics, and materials aspects associated with their optimized construction are presented. These systems allow advantages in mechanical strength, placement versatility, and minimized interfacial stresses compared to other NFC technologies and wearable electronics. Detailed experimental studies and theoretical modeling of the mechanical and electromagnetic properties of these systems establish understanding of the key design considerations. These concepts can apply to many other types of wireless communication systems including biosensors and electronic implants. 相似文献
994.
Three-dimensional segmentation and growth-rate estimation of small pulmonary nodules in helical CT images 总被引:11,自引:0,他引:11
Kostis WJ Reeves AP Yankelevitz DF Henschke CI 《IEEE transactions on medical imaging》2003,22(10):1259-1274
Small pulmonary nodules are a common radiographic finding that presents an important diagnostic challenge in contemporary medicine. While pulmonary nodules are the major radiographic indicator of lung cancer, they may also be signs of a variety of benign conditions. Measurement of nodule growth rate over time has been shown to be the most promising tool in distinguishing malignant from nonmalignant pulmonary nodules. In this paper, we describe three-dimensional (3-D) methods for the segmentation, analysis, and characterization of small pulmonary nodules imaged using computed tomography (CT). Methods for the isotropic resampling of anisotropic CT data are discussed. 3-D intensity and morphology-based segmentation algorithms are discussed for several classes of nodules. New models and methods for volumetric growth characterization based on longitudinal CT studies are developed. The results of segmentation and growth characterization methods based on in vivo studies are described. The methods presented are promising in their ability to distinguish malignant from nonmalignant pulmonary nodules and represent the first such system in clinical use. 相似文献
995.
Ahn Woo-Young; Rass Olga; Fridberg Daniel J.; Bishara Anthony J.; Forsyth Jennifer K.; Breier Alan; Busemeyer Jerome R.; Hetrick William P.; Bolbecker Amanda R.; O'Donnell Brian F. 《Canadian Metallurgical Quarterly》2011,120(4):911
Patients with bipolar disorder (BD) and schizophrenia (SZ) often show decision-making deficits in everyday circumstances. A failure to appropriately weigh immediate versus future consequences of choices may contribute to these deficits. We used the delay discounting task in individuals with BD or SZ to investigate their temporal decision making. Twenty-two individuals with BD, 21 individuals with SZ, and 30 healthy individuals completed the delay discounting task along with neuropsychological measures of working memory and cognitive function. Both BD and SZ groups discounted delayed rewards more steeply than did the healthy group even after controlling for current substance use, age, gender, and employment. Hierarchical multiple regression analyses showed that discounting rate was associated with both diagnostic group and working memory or intelligence scores. In each group, working memory or intelligence scores negatively correlated with discounting rate. The results suggest that (a) both BD and SZ groups value smaller, immediate rewards more than larger, delayed rewards compared with the healthy group and (b) working memory or intelligence is related to temporal decision making in individuals with BD or SZ as well as in healthy individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
996.
Dodd Alyson L.; Mansell Warren; Morrison Anthony P.; Tai Sara 《Canadian Metallurgical Quarterly》2011,23(3):635
The Hypomanic Attitudes and Positive Predictions Inventory (HAPPI; W. Mansell, 2006) was developed to assess multiple, extreme, self-relevant appraisals of internal states. The present study aimed to validate the HAPPI in a clinical sample. Participants (N = 50) with a diagnosis of bipolar disorder (confirmed by a structured clinical interview) completed a series of questionnaires pertaining to clinical factors, reward motivation, cognitive style, symptoms, and functioning at baseline, in addition to the HAPPI. Over the following 4 weeks, participants were asked to complete self-report measures of symptoms (activation, perceived conflict, depression, and well-being), as well as work and social functioning, twice weekly. The authors hypothesized that the HAPPI would be associated with prospective bipolar symptoms and functioning, when controlling for baseline symptoms and potentially confounding measures. The HAPPI was positively, independently associated with activation and conflict after 4 weeks. Furthermore, individual HAPPI factors were associated with activation, conflict, and depression. The results provided preliminary support for the predictive validity of the HAPPI in a clinical sample. The HAPPI could be used in the future as a tool in cognitive behavioral therapy for bipolar disorder to identify problematic beliefs and guide formulation. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
997.
Sigmon Stacey C.; Steingard Sandra; Badger Gary J.; Anthony Stacey L.; Higgins Stephen T. 《Canadian Metallurgical Quarterly》2000,8(4):509
The feasibility of using monetary incentives to promote abstinence from marijuana use among individuals with serious mental illness was examined by using a within-subjects experimental design. Participants were 18 adults with schizophrenia or other serious mental illness who reported regular marijuana use. During 2 baseline conditions, participants received payment for submitting urine specimens independent of urinalysis results. During 3 incentive conditions, participants received varying amounts of money if urinalysis results were negative for recent marijuana use. The number of marijuana-negative specimens obtained was significantly greater during incentive than baseline conditions. These results provide evidence that marijuana use among at least some mentally ill individuals is sensitive to contingent reinforcement and support the potential feasibility of using contingency management interventions to reduce substance abuse among the mentally ill. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
2D triaxially braided carbon fiber composites were subjected to off-axis compression under static and low velocity impact loading. Three types of specimens with axial fiber tows at angles of 30°, 60°, and 75° to the direction of loading were studied under uniaxial compression loading using a modified compression loading fixture that has anti-buckling guides. Static tests were carried out using a hydraulically activated MTS loading frame, while, low velocity impact tests were conducted using a drop tower facility. A three parameter homogenized orthotropic plasticity model was used to characterize the inelastic response and the constants associated with this characterization were determined uniquely. Results from this characterization were subsequently used to analyze the rate dependent interfacial effects in these materials. Two types of composites made from two different resins, but with the same textile architecture were used for this study. The effect of the resin properties on the unusual rate effects exhibited by the composite is seen to be captured well with the three parameter orthotropic plasticity model adopted. 相似文献
999.
The crystallography of martensite formed in 0.2C-2.0Mn-1.5Si-0.6Cr steel was studied using the electron backscattered diffraction(EBSD) technique.The results showed that the observed orientation relationship(OR) was closer to that of Nishiyama-Wassermann(N-W) than Kurdjumov-Sachs.The martensite consisted of parallel laths forming morphological packets.Typically,there were three different lath orientations in a morphological packet consisting of three specific N-W OR variants sharing the same {111} austenite plane.A packet of martensite laths with a common {111} austenite plane was termed a crystallographic packet.Generally,the crystallographic packet size corresponded to the morphological packet size,but occasionally the morphological packet was found to consist of two or more crystallographic packets.Therefore,the crystallographic packet size appeared to be finer than the morphological packet size.The relative orientation between the variants in crystallographic packets was found to be near 60 /<110>,which explains the strong peak observed near 60 in the grain boundary misorientation distribution.Martensite also contained a high fraction of boundaries with a misorientation in the range 2.5-8.Typically these boundaries were found to be located inside the martensite laths forming sub-laths. 相似文献
1000.
Glaura G. Silva Anthony W. Musumeci Ana Paula Gomes Jiang-Wen Liu Eric R. Waclawik Graeme A. George Ray L. Frost Marcos A. Pimenta 《Journal of Materials Science》2009,44(13):3498-3503
A purified commercial double-walled carbon nanotube (DWCNT) sample was investigated by transmission electron microscopy (TEM),
thermogravimetry (TG), and Raman spectroscopy. Moreover, the heat capacity of the DWCNT sample was determined by temperature-modulated
differential scanning calorimetry in the range of temperature between −50 and 290 °C. The main thermo-oxidation characterized
by TG occurred at 474 °C with the loss of 90 wt% of the sample. Thermo-oxidation of the sample was also investigated by high-resolution
TG, which indicated that a fraction rich in carbon nanotube represents more than 80 wt% of the material. Other carbonaceous
fractions rich in amorphous coating and graphitic particles were identified by the deconvolution procedure applied to the
derivative of TG curve. Complementary structural data were provided by TEM and Raman studies. The information obtained allows
the optimization of composites based on this nanomaterial with reliable characteristics. 相似文献