全文获取类型
收费全文 | 852篇 |
免费 | 16篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 161篇 |
金属工艺 | 17篇 |
机械仪表 | 11篇 |
建筑科学 | 39篇 |
能源动力 | 16篇 |
轻工业 | 43篇 |
水利工程 | 5篇 |
无线电 | 47篇 |
一般工业技术 | 120篇 |
冶金工业 | 306篇 |
原子能技术 | 5篇 |
自动化技术 | 89篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 39篇 |
2012年 | 23篇 |
2011年 | 49篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 22篇 |
2007年 | 27篇 |
2006年 | 35篇 |
2005年 | 27篇 |
2004年 | 15篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 24篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1972年 | 9篇 |
1970年 | 9篇 |
1955年 | 8篇 |
排序方式: 共有874条查询结果,搜索用时 0 毫秒
41.
This paper introduces two improved forms of the ant colony optimization (ACO) algorithm applied to a proportional integral derivative (PID) controller and Smith predictor design. Derivative free optimization methods, namely simplex derivative based pattern search (SDPS) and implicit filtering (IMF), are used to intensify the search mechanism in the ACO algorithm with improved convergence over the original ACO. The effectiveness of the controller schemes using the proposed algorithms, namely SDPS-ACO, and IMF-ACO, is demonstrated using unit step set point response for a class of dead-time systems, and the results are compared with some existing methods of controller tuning. 相似文献
42.
Auffan M Decome L Rose J Orsiere T De Meo M Briois V Chaneac C Olivi L Berge-Lefranc JL Botta A Wiesner MR Bottero JY 《Environmental science & technology》2006,40(14):4367-4373
Although the current production of oxide nanoparticles may be modest, the wide range of proposed applications and forecasted growth in production has raised questions about the potential impact of these nanoparticles on the environment and human health. Iron oxide nanoparticles have been proposed for an increasing number of biomedical applications although in vitro toxicity depending on the particles coating has been evidenced. The aim of this study was to examine the potential in vitro cyto- and genotoxicity on human dermal fibroblasts of DMSA-coated maghemite nanoparticles (NmDMSA) as a function of well-defined physicochemical states. Well-stabilized NmDMSA produced weak cytotoxic and no genotoxic effects. This is attributed in part to the DMSA coating, which serves as a barrier for a direct contact between nano-oxide and fibroblasts, inhibiting a potential toxic effect. 相似文献
43.
Connectionist learning models have had considerable empirical success, but it is hard to characterize exactly what they learn. The learning of finite-state languages (FSL) from example strings is a domain which has been extensively studied and might provide an opportunity to help understand connectionist learning. A major problem is that traditional FSL learning assumes the storage of all examples and thus violates connectionist principles. This paper presents a provably correct algorithm for inferring any minimum-state deterministic finite-state automata (FSA) from a complete ordered sample using limited total storage and without storing example strings. The algorithm is an iterative strategy that uses at each stage a current encoding of the data considered so far, and one single sample string. One of the crucial advantages of our algorithm is that the total amount of space used in the course of learning for encoding any finite prefix of the sample is polynomial in the size of the inferred minimum state deterministic FSA. The algorithm is also relatively efficient in time and has been implemented. More importantly, there is a connectionist version of the algorithm that preserves these properties. The connectionist version requires much more structure than the usual models and has been implemented using the Rochester Connectionist Simulator. We also show that no machine with finite working storage can iteratively identify the FSL from arbitrary presentations. 相似文献
44.
Wen-Yi Lin Hai Huang Fang Yang Jerome J. Schmitt Andrew T. Hunt Robert R. Romanofsky 《Integrated ferroelectrics》2013,141(1-2):1-12
Abstract Epitaxial barium strontium titanate and strontium titanate thin films were deposited on (100) MgO single-crystal substrates, utilizing Combustion Chemical Vapor Deposition. The as-deposited films were patterned with gold electrodes to form interdigitated structure to function as electrically tunable devices, namely, coupled microstripline phase shifters (CMPS). Microwave dielectric properties were characterized at 11–20 GHz with an applied electric field up to ±35 V/μm. A maximum figure of merit of 53°/dB at 20 GHz and 23°C was measured. The demonstrated high degree of tunability and relatively low loss showed great potential of these films for the targeted frequency agile device applications. Characterization, using SEM, EDS, and XRD, is presented in addition to microwave performance as a function of dc bias and frequency. 相似文献
45.
Jinjie Liu Moysey Brio Jerome V. Moloney 《International Journal of Numerical Modelling》2014,27(1):22-33
A novel stable anisotropic finite‐difference time‐domain (FDTD) algorithm based on the overlapping cells is developed for solving Maxwell's equations of electrodynamics in anisotropic media with interfaces between different types of materials, such as the interface between anisotropic dielectrics and dispersive medium or perfect electric conductor (PEC). The previous proposed conventional anisotropic FDTD methods suffer from the late‐time instability due to the extrapolation of the field components near the material interface. The proposed anisotropic overlapping Yee FDTD method is stable, as it relies on the overlapping cells to provide the collocated field values without any interpolation or extrapolation. Our method has been applied to simulate electromagnetic invisibility cloaking devices with both anisotropic dielectrics and PEC included in the computational domain. Numerical results and eigenvalue analysis confirm that the conventional anisotropic FDTD method is weakly unstable, whereas our method is stable. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
46.
Charles E. CarraherJr. Michael R. Roner Anthony G. Campbell Alisa Moric-Johnson Lindsey Miller Paul Slawek Francesca Mosca Jeffrey D. Einkauf Jerome E. Haky Ryan Crichton 《Journal of Inorganic and Organometallic Polymers and Materials》2018,28(2):481-491
Organotin polyesters were synthesized from d-camphoric acid. Since d-camphoric acid is a natural product, this is part of the green chemistry initiative. Further, synthesis occurred employing commercially available reactants and the interfacial system which is used industrially to synthesize aramids and polycarbonates. Thus, scale-up is straightforward. Polymers were synthesized employing the interfacial reaction between various organotin dihalides and the salt of d-camphoric acid. Reaction was rapid occurring in 30 s and less. Product yield was good except for the product from dioctyltin dichloride. The products are polymeric with chain lengths from 230 to 2200. Structural characterization with infrared spectrometry and MALDI MS are consistent with the formation of organotin polyesters containing the camphoric acid moiety within its backbone. IR shows formation of the Sn–OOC(O) linkage with the polymer having a combination of bridging and non-bridging geometrical arrangements about the tin atom. MALDI MS shows ion fragment to two and three repeat units. The products exhibit good ability to inhibit a battery of cancer cells including those from pancreatic cancer. The effective concentration for inhibition of the cancer cell lines are generally in the same range as those found for cisplatin and in the ng/mL range. 相似文献
47.
Discusses an unexpected outcome of heroin addiction treatment; namely, the failure inherent in successfully removing patients from illicit drug use, only to find that in doing so, expectations on the part of clients regarding their ability to effectively function in society have risen beyond their ability to realistically attain their goals. Recidivism becomes likely when addicts cannot cope with the stress of low status employment, specific situations of the nondrug world, recreational drug use of straight co-workers, and the effort of maintaining gains made in treatment. Cognitive interpersonal problem-solving skills are recommended as a means of focusing the addict on developing habitual thinking on alternatives, consequences, means and ends, different perspectives, and social influences on the addict's own actions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
48.
Yi-Chun Chen Yii-Der I. Chen Xiaohui Li Wendy Post David Herrington Joseph F. Polak Jerome I. Rotter Kent D. Taylor 《Lipids》2009,44(8):733-743
HMG-CoA reductase (HMGCR) is an enzyme involved in cholesterol synthesis. To investigate the contribution of the HMGCR gene to lipids and lipoprotein subfractions in different ethnicities, we performed an association study in the Multi-Ethnic
Study of Atherosclerosis (MESA). In total, 2,444 MESA subjects [597 African-Americans (AA), 627 Chinese-Americans (CHA), 612
European-Americans (EA), and 608 Hispanic-Americans (HA)] without statin use were included. Participants had measurements
of blood pressure, anthropometry, and fasting blood samples. Subjects were genotyped for 10 single nucleotide polymorphisms
(SNPs). After excluding SNPs with minor allele frequency <5%, a single block was constructed. The most frequent haplotype
was H1 (41–56%) in all ethnic groups except AA (H2a, 44.9%). Lower triglyceride level was associated with the H2a haplotype
in AA and H2 in HA. In HA, H4 carriers had higher levels of triglyceride and small low-density lipoprotein (s-LDL), and lower
high-density lipoprotein cholesterol (HDL-c), while carriers with H7 or H8 had associations with these traits in the opposite
direction. No significant association was discovered in both CHA and EA. The total variation for triglyceride that could be
explained by H2 alone was 2.6% in HA and 1.4% in AA. In conclusion, HMGCR gene variation is associated with multiple lipid/lipoprotein traits, especially with triglyceride, s-LDL, and HDL-c. The
impact of the genetic variance is modest and differs greatly among ethnicities. 相似文献
49.
This article explores the relationship between concepts of object loss and mourning and the loss of a bodily part or psychological or physical function in a rehabilitation context. The psychoanalytic literature on object loss and the mourning process is reviewed and related to existing literature on the adjustment-to-disability process. Similarities and differences between the classical mourning process and the adjustment-to-disability process are discussed, and suggestions are offered for using psychoanalytic strategies to facilitate adjustment to disability. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Examined whether antecedents are reactivated by anaphor, in 3 experiments with a total of 144 undergraduates, using additional control sentences and an alternative response time measure. Ss read a series of texts each containing a target item. Immediately after the last line of each text, the item was probed using a recognition task in Exp I and a naming task in Exp II. Ss were faster to respond to the item when the last line contained an anaphoric reference to it than when the last line referred to a different item from the text. Additional control conditions ensured that the effect was not due to semantic priming and that the probed item was not in working memory when the last line was encountered. Findings in Exp III, which compared reading and naming times when the last sentence continued the established topic with times when the last sentence changed the topic, suggest that previous evidence for reinstatement reflected interference from a change of topic in the last line rather than facilitation due to reinstatement of the probed item. It is suggested that the paradigm developed by G. McKoon and R. Ratcliff (see record 1981-24997-001) requires careful control of variables. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献