全文获取类型
收费全文 | 445篇 |
免费 | 6篇 |
专业分类
化学工业 | 86篇 |
金属工艺 | 5篇 |
机械仪表 | 3篇 |
建筑科学 | 14篇 |
能源动力 | 10篇 |
轻工业 | 26篇 |
水利工程 | 9篇 |
无线电 | 10篇 |
一般工业技术 | 62篇 |
冶金工业 | 163篇 |
自动化技术 | 63篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 10篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 28篇 |
2010年 | 17篇 |
2009年 | 28篇 |
2008年 | 30篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 15篇 |
2003年 | 13篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有451条查询结果,搜索用时 15 毫秒
101.
Holroyd Kenneth A.; France Janis L.; Cordingley Gary E.; Rokicki Lori A.; Kvaal Steven A.; Lipchik Gay L.; McCool Heidi R. 《Canadian Metallurgical Quarterly》1995,63(2):327
This article evaluated the ability of propranolol to enhance results achieved with relaxation-biofeedback training. Thirty-three patients were randomized to relaxation-biofeedback training alone (administered in a limited-contact treatment format), or to relaxation-biofeedback training accompanied by long-acting propranolol (with dosage individualized at 60, 120, or 180 mg/day). Concomitant propranolol therapy significantly enhanced the effectiveness of relaxation-biofeedback training when either daily headache recordings (79% vs. 54% reduction in migraine activity) or neurologist clinical evaluations (90% vs. 66% reduction) were used to assess treatment outcome. Concomitant propranolol therapy also yielded larger reductions in analgesic medication use and greater improvements of quality of life measures than relaxation-biofeedback training alone but was more frequently associated with side effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
102.
Recent animal research has demonstrated that humans are not a uniquely aggressive species and that even in so-called violence-prone animals, aggression is always an optional strategy. Although some form of intraspecific aggression exists in every vertebrate species studied thus far, it is also true that all organisms have coevolved equally potent inhibitory mechanisms that enable them to use an aggressive strategy selectively or to suppress aggression when it is in their interest to do so. Parallel studies of aggression in children, assaultive adults, and even entire societies have suggested that humans are exquisitely sensitive to subtle social controls that could be used to reduce the frequency of individual acts of violence. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
Knowledge representation support 总被引:1,自引:1,他引:0
The representation of world knowledge in a machine translation system is discussed, especially in terms of the interlingua text that is adopted in KBMT-89. While knowledge about the world is at the core of a knowledge-based machine translation program, it cannot be extracted from a text without knowledge about how languages encode it syntactically. The paper therefore also presents the grammar formalism with which language-specific syntactic knowledge is presented. Details are presented of our version of unification-based grammar, its basis in linguistic theory and its role in a knowledge-based machine translation system. 相似文献
104.
Because human immunodeficiency virus type 1 (HIV-1) infection is characterized by a large number of viral replication cycles and rapid cell turnover in vivo, successful gene therapy requires an approach effective under these conditions. The antitat gene has been proposed for gene therapy because it effectively blocks Tat function and the replication of HIV-1. However, neither antitat nor any other antiviral gene has been shown to inhibit HIV in the presence of high viral load and inflammatory cytokines, a condition closer to the in vivo situation. We show that cells transduced with antitat retrovirus vector are resistant to high multiplicity of HIV infection. In the presence of inflammatory cytokines, including interleukin-1 and tumor necrosis factor, both known to activate viral gene expression independently of Tat, antitat suppressed virus replication. HIV-1 inhibition was observed when cell were treated with a mixture of inflammatory cytokines able to induce acquired immunodeficiency syndrome (AIDS) Kaposi's sarcoma cell growth. These molecules have been shown to be increased in HIV-1-infected individuals, and it is suggested they play a role in the pathogenesis of AIDS. Our results suggest that antitat is effective under conditions present in vivo and therefore a primary candidate for HIV-1 gene therapy. 相似文献
105.
A method for predicting the highly nonlinear stress-strain behavior and dilatation induced by cavitation of highly filled particulate composites from constituent properties has been developed. The approach presented uses a variation of linear elasticity throughout and has no adjustable parameters, unlike the methods currently used, which require large numbers of fitting factors and complicated nonlinear analyses. An energy balance derived from the first law of thermodynamics calculates critical strain values at which filler particles will debond when subjected to deformation. Repeated calculations of critical strain values using re-evaluated material properties accounting for the damage caused by debonding give very nonlinear stress-strain and dilatation curves. Experimentally observed dependencies on particle size, filler concentration, adhesion, and matrix and filler properties are correctly predicted. The method can be generalized for any state of stress or particle shape. Comparisons of experimental data with the model results give good agreement. 相似文献
106.
Lori L. Stonecipher Peggy S. Hurley David H. Netzly 《Journal of chemical ecology》1993,19(5):1021-1027
Apigeninidin, a 3-deoxyanthocyanidin present in sorghum, was chemically synthesized and effectively purified by extracting impurities from aqueous 2 N HC1 into ethyl acetate. Apigeninidin (50mol) applied to filter paper disks inhibited the growth on agar plates of selected gram-positive bacteria (Bacillus cereus, Staphylococcus aureus, Staphylococcus epidermidis, andStreptococcus faecalis) and to a lesser extent gram-negative bacteria (Escherichia coli, Serratia marcens, andShigella flexneri). Apigeninidin was not mutagenic based on the Ames assay. The ability of apigeninidin to precipitate proteins from plant extracts could be physiologically important if it can be shown to bind to specific plant proteins. 相似文献
107.
Paola Cappanera Luciano Lenzini Alessandro Lori Giovanni Stea Gigliola Vaglini 《Computer Networks》2013,57(11):2301-2312
We investigate the problem of joint routing and link scheduling in Time-Division Multiple Access (TDMA) Wireless Mesh Networks (WMNs) carrying real-time traffic. We propose a framework that always computes a feasible solution (i.e. a set of paths and link activations) if there exists one, by optimally solving a mixed integer-nonlinear problem. Such solution can be computed in minutes or tens thereof for e.g. grids of up to 4 × 4 nodes. We also propose heuristics based on Lagrangian decomposition to compute suboptimal solutions considerably faster and/or for larger WMNs, up to about 50 nodes. We show that the heuristic solutions are near-optimal, and we exploit them to gain insight on the schedulability in WMN, i.e. to investigate the optimal placement of one or more gateways from a delay bound perspective, and to investigate how the schedulability is affected by the transmission range. 相似文献
108.
Morphological changes in the anterior cingulate cortex are found in subjects with schizophrenia, attention deficit hyperactivity disorder, and obsessive–compulsive disorder. These changes are hypothesized to underlie the impairments these individuals show on tasks that require cognitive control. The anterior cingulate cortex has previously been shown to be active in situations involving high conflict, presentation of salient, distracting stimuli, and error processing, that is, situations that occur when a shift in attention or responding is required. However, there is some uncertainty as to what specific role the anterior cingulate cortex plays in these situations. The current study used converging evidence from two behavioral paradigms to determine the effects of excitotoxic lesions in the anterior cingulate cortex on executive control. The first assay tests reversal learning, attentional set formation and shifting. The second assesses sustained attention with and without distractors. Animals with anterior cingulate cortex lesions were impaired during reinforcement reversals, discriminations that required subjects to disregard previously relevant stimulus attributes and showed a more rapid decline in attentional ability than Sham-Lesioned subjects when maintaining sustained attention for extended periods of time. These results are consistent with the hypothesis that the anterior cingulate cortex is involved in attending to stimulus attributes that currently predict reinforcement in the presence of previously relevant, salient distractors and maintaining sustained attention over prolonged time on task. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
109.
Many consumers today are purchasing renewable energy in large part for the greenhouse gas (GHG) emissions benefits that they provide. Emerging carbon regulation in the US has the potential to affect existing markets for renewable energy. Carbon cap-and-trade programs are now under development in the Northeast under the Regional Greenhouse Gas Initiative (RGGI) and in early stages of development in the West and Midwest. There is increasing discussion about carbon regulation at the national level as well. While renewable energy will likely benefit from carbon cap-and-trade programs because compliance with the cap will increase the costs of fossil fuel generation, cap-and-trade programs can also impact the ability of renewable energy generation to affect overall CO2 emissions levels and obtain value for those emissions benefits. This paper summarizes key issues for renewable energy markets that are emerging with carbon regulation, such as the implications for emissions benefits claims and voluntary market demand and the use of renewable energy certificates (RECs) in multiple markets. It also explores policy options under consideration for designing carbon policies to enable carbon markets and renewable energy markets to work together. 相似文献
110.
Our current understanding of how programmers perform feature location during software maintenance is based on controlled studies or interviews, which are inherently limited in size, scope and realism. Replicating controlled studies in the field can both explore the findings of these studies in wider contexts and study new factors that have not been previously encountered in the laboratory setting. In this paper, we report on a field study about how software developers perform feature location within source code during their daily development activities. Our study is based on two complementary field data sets: one that reflects complete IDE activity of 67 professional developers over approximately one month, and the other that reflects usage of an IR-based code search tool by nearly 600 developers. Analyzing this data, we report results on how often developers use which type of code search tools, on the types of queries and retreival strategies used by developers, and on patterns of developer feature location behavior following code search. The results of the study suggest that there is (1) a need for helping developers to devise better code search queries; (2) a lack of adoption of niche code search tools; (3) a need for code search tool to handle both lookup and exploratory queries; and (4) a need for better integration between code search, structured navigation, and debugging tools in feature location tasks. 相似文献