首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   987篇
  免费   43篇
电工技术   4篇
化学工业   201篇
金属工艺   8篇
机械仪表   5篇
建筑科学   35篇
能源动力   12篇
轻工业   129篇
水利工程   11篇
石油天然气   7篇
无线电   32篇
一般工业技术   164篇
冶金工业   334篇
原子能技术   1篇
自动化技术   87篇
  2024年   1篇
  2023年   11篇
  2022年   28篇
  2021年   40篇
  2020年   29篇
  2019年   22篇
  2018年   20篇
  2017年   31篇
  2016年   26篇
  2015年   24篇
  2014年   39篇
  2013年   54篇
  2012年   53篇
  2011年   74篇
  2010年   60篇
  2009年   44篇
  2008年   76篇
  2007年   54篇
  2006年   61篇
  2005年   56篇
  2004年   41篇
  2003年   26篇
  2002年   24篇
  2001年   12篇
  2000年   23篇
  1999年   12篇
  1998年   12篇
  1997年   15篇
  1996年   13篇
  1995年   9篇
  1994年   7篇
  1993年   6篇
  1992年   6篇
  1990年   4篇
  1989年   5篇
  1987年   5篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1975年   1篇
排序方式: 共有1030条查询结果,搜索用时 15 毫秒
51.
[Correction Notice: An erratum for this article was reported in Vol 7(3) of Psychological Services (see record 2010-17074-004). The copyright for the article was listed incorrectly. This article is in the Public Domain. The online version has been corrected.] The present study examined interest in family involvement in treatment and preferences concerning the focus of family oriented treatment for veterans (N = 114) participating in an outpatient Veterans Affairs outpatient posttraumatic stress disorder (PTSD) program. Most veterans viewed PTSD as a source of family stress (86%) and expressed interest in greater family involvement in their treatment (79%). These results suggest the need to consider increasing family participation in the clinical care of individuals with PTSD and to develop specialized family educational and support services for this population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
52.
The vegetative, or above ground, portion of radishes are not typically consumed and have not been characterized in terms of their phytochemical content or biological activity. The antioxidant capacity of the freeze-dried vegetative portion of mature Spanish black radishes (harvested 2 months after planting) was 3.7-, 3.6- and 2.9-fold greater than freeze-dried roots as assayed by ferric ion reducing antioxidant power (FRAP), total phenolics and oxygen radical absorbance capacity (ORAC), respectively. No carotenoids were detected in the roots, however the vegetative portion contained 905.0 and 421.2 μg/g of lutein and β-carotene, respectively. Despite differences in glucosinolate composition, a class of compounds related to the induction of detoxification enzymes, the aqueous extracts of roots and the vegetative portion similarly induced quinone reductase activity and the expression of multiple phase I and II detoxification enzymes in the HepG2 human hepatoma cell line. When juiced, the resulting freeze-dried juice and pulp of the vegetative portion maintained the ability to induce detoxification enzymes, although there were some differences in the phytochemical contents of these two dried materials. These data demonstrate that the ability of the vegetative portion of Spanish black radish, which has significantly greater antioxidant potential than roots, to induce detoxification enzyme expression was similar to that of the roots.  相似文献   
53.
Materials that respond to physiological stimuli are important in developing advanced biomaterials for modern therapies. The reversibility of covalent crosslinks formed by phenylboronate (PBA) and salicylhydroxamate (SHA) has been exploited to provide a pH‐responsive gel for application to the vaginal tract. Dynamic rheology reveals that the gel frequency‐dependent viscoelastic properties are modulated by pH. At pH 4.8 the viscous component dominates throughout most of the frequency range. As the pH increases, the characteristic relaxation time continues to increase while the GPlateau levels off above pH 6. At pH 7.5, the elastic component dominates throughout the frequency sweep and is predominately independent of frequency. Particle tracking assesses the transport of both fluorescently labeled HIV‐1 and 100‐nm latex particles in the PBA–SHA crosslinked gel as a function of pH. At pH 4.8 the ensemble‐averaged mean squared displacement at lag times greater than three seconds reveals that transport of the HIV‐1 and 100‐nm particles becomes significantly impeded by the matrix, exhibiting diffusion coefficients less than 0.0002 µm2 s?1. This pH‐responsive gel thus displays properties that have the potential to significantly reduce the transport of HIV‐1 to susceptible tissues and thus prevent the first stage of male‐to‐female transmission of HIV‐1.  相似文献   
54.
Vernonia galamensis oil, containing naturally epoxidized triglycerides, was reacted withn-butylamine,n-pentylamine andn-hexylamine to afford high yields of epoxidized secondary amides. Three reaction conditions were investigated: (i) reflux with amines as solvents, (ii) reflux with hexane as the solvent and (iii) room temperature with the amines as solvents. Reactions with amines as refluxing solvents were completed in 1–5 h, while those with hexane went to completion within 2 to 5 d. Room temperature reactions were onlyca. 80% complete after several days. Reactivity was increased with higher amine homologs at both reflux and room temperature reaction conditions. Isolated yields of epoxy-containing amides were about 80% with purity exceeding 96% in all cases. Spectroscopic characterization of the previously unreported alkyl-vernolamides is provided.  相似文献   
55.
56.
Recently, General Purpose Graphical Processing Units (GP-GPUs) have been identified as an intriguing technology to accelerate numerous data-parallel algorithms. Several GPU architectures and programming models are beginning to emerge and establish their niche in the High-Performance Computing (HPC) community. New massively parallel architectures such as the Nvidia??s Fermi and AMD/ATi??s Radeon pack tremendous computing power in their large number of multiprocessors. Their performance is unleashed using one of the two GP-GPU programming models: Compute Unified Device Architecture (CUDA) and Open Computing Language (OpenCL). Both of them offer constructs and features that have direct bearing on the application runtime performance. In this paper, we compare the two GP-GPU architectures and the two programming models using a two-level character recognition network. The two-level network is developed using four different Spiking Neural Network (SNN) models, each with different ratios of computation-to-communication requirements. To compare the architectures, we have chosen the two extremes of the SNN models for implementation of the aforementioned two-level network. An architectural performance comparison of the SNN application running on Nvidia??s Fermi and AMD/ATi??s Radeon is done using the OpenCL programming model exhausting all of the optimization strategies plausible for the two architectures. To compare the programming models, we implement the two-level network on Nvidia??s Tesla C2050 based on the Fermi architecture. We present a hierarchy of implementations, where we successively add optimization techniques associated with the two programming models. We then compare the two programming models at these different levels of implementation and also present the effect of the network size (problem size) on the performance. We report significant application speed-up, as high as 1095× for the most computation intensive SNN neuron model, against a serial implementation on the Intel Core 2 Quad host. A comprehensive study presented in this paper establishes connections between programming models, architectures and applications.  相似文献   
57.
Stereoscopic depth cues improve depth perception and increase immersion within virtual environments (VEs). However, improper display of these cues can distort perceived distances and directions. Consider a multi-user VE, where all users view identical stereoscopic images regardless of physical location. In this scenario, cues are typically customized for one "leader" equipped with a head-tracking device. This user stands at the center of projection (CoP) and all other users ("followers") view the scene from other locations and receive improper depth cues. This paper examines perceived depth distortion when viewing stereoscopic VEs from follower perspectives and the impact of these distortions on collaborative spatial judgments. Pairs of participants made collaborative depth judgments of virtual shapes viewed from the CoP or after displacement forward or backward. Forward and backward displacement caused perceived depth compression and expansion, respectively, with greater compression than expansion. Furthermore, distortion was less than predicted by a ray-intersection model of stereo geometry. Collaboration times were significantly longer when participants stood at different locations compared to the same location, and increased with greater perceived depth discrepancy between the two viewing locations. These findings advance our understanding of spatial distortions in multi-user VEs, and suggest a strategy for reducing distortion.  相似文献   
58.
Times New Roman and Arial typefaces in 10- and 12-point, dot-matrix and anti-aliased format conditions were compared for readability (accuracy, reading speed, and accuracy/reading speed), as well as perceptions of typeface legibility, sharpness, ease of reading, and general preference. In assessing readability, the 10-point anti-aliased Arial typeface was read slower than the other type conditions. Examining perceptions of typeface legibility, sharpness, and ease of reading detected significant effects for typeface, size, and format. Overall, the 12-point dot-matrix Arial typeface was preferred to the other typefaces. Recommendations for appropriate typeface combinations for computer-displayed text are discussed.  相似文献   
59.
This study investigated students' preference for e‐mail over face‐to‐face (FtF) communication for interpersonal goal achievement (i.e., instrumental, relational, self‐presentational) with faculty advisors. An exploratory analysis of undergraduate students revealed that they did not prefer computer‐mediated communication (i.e., e‐mail) over FtF communication with advisors when addressing all 3 interpersonal goal types. Significant gender differences were also found, with women reporting more use of e‐mail, and men preferring to address self‐presentational goals in FtF settings. It also was found that compared to Caucasians, African Americans did not prefer CMC to FtF interaction in achieving instrumental and self‐presentational goals. Results of this study suggest that despite the ubiquity of e‐mail communication, undergraduates did not prefer e‐mail over FtF contact with faculty advisors.  相似文献   
60.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号