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   3828篇
  免费   263篇
  国内免费   4篇
电工技术   77篇
综合类   19篇
化学工业   981篇
金属工艺   81篇
机械仪表   64篇
建筑科学   310篇
矿业工程   18篇
能源动力   102篇
轻工业   262篇
水利工程   27篇
石油天然气   2篇
无线电   330篇
一般工业技术   821篇
冶金工业   233篇
原子能技术   14篇
自动化技术   754篇
  2024年   6篇
  2023年   58篇
  2022年   133篇
  2021年   148篇
  2020年   119篇
  2019年   98篇
  2018年   127篇
  2017年   110篇
  2016年   162篇
  2015年   167篇
  2014年   189篇
  2013年   265篇
  2012年   255篇
  2011年   313篇
  2010年   260篇
  2009年   207篇
  2008年   209篇
  2007年   217篇
  2006年   163篇
  2005年   155篇
  2004年   102篇
  2003年   92篇
  2002年   82篇
  2001年   53篇
  2000年   46篇
  1999年   53篇
  1998年   47篇
  1997年   33篇
  1996年   46篇
  1995年   31篇
  1994年   18篇
  1993年   18篇
  1992年   11篇
  1991年   10篇
  1990年   10篇
  1989年   13篇
  1988年   5篇
  1986年   7篇
  1985年   7篇
  1984年   3篇
  1982年   4篇
  1981年   3篇
  1979年   8篇
  1977年   3篇
  1976年   5篇
  1975年   3篇
  1974年   3篇
  1973年   5篇
  1970年   3篇
  1969年   2篇
排序方式: 共有4095条查询结果,搜索用时 15 毫秒
101.
102.
Cancer is a disease exhibiting uncontrollable cell growth and spreading to other parts of the organism. It is a heavy, worldwide burden for mankind with high morbidity and mortality. Therefore, groundbreaking research and innovations are necessary. Research in space under microgravity (µg) conditions is a novel approach with the potential to fight cancer and develop future cancer therapies. Space travel is accompanied by adverse effects on our health, and there is a need to counteract these health problems. On the cellular level, studies have shown that real (r-) and simulated (s-) µg impact survival, apoptosis, proliferation, migration, and adhesion as well as the cytoskeleton, the extracellular matrix, focal adhesion, and growth factors in cancer cells. Moreover, the µg-environment induces in vitro 3D tumor models (multicellular spheroids and organoids) with a high potential for preclinical drug targeting, cancer drug development, and studying the processes of cancer progression and metastasis on a molecular level. This review focuses on the effects of r- and s-µg on different types of cells deriving from thyroid, breast, lung, skin, and prostate cancer, as well as tumors of the gastrointestinal tract. In addition, we summarize the current knowledge of the impact of µg on cancerous stem cells. The information demonstrates that µg has become an important new technology for increasing current knowledge of cancer biology.  相似文献   
103.
104.
Prion‐reduction in standard biodiesel processes is caused by acidic and alkaline conditions. In the alternative RepCat biodiesel process, efficient prion‐reduction can be achieved by high‐temperature/pressure. However, a possible increase in thermostability of prions in the presence of methanol during these conditions has not previously been investigated, and is verified in this work. Samples are spiked with prions, treated with methanol, and incubated at 220 °C at 80 bar for 30 min. No traces of protease‐resistant prion protein (as proxy for prions) are detected in tallow or glycerine (as the final by‐product) after treatment. Serial dilutions of spiked prions show at least 6 log10 prion reduction. More importantly, similar effects are detected using milder conditions of 200 °C at 70 bar for 15 min, representing the worst‐case conditions of the process. In conclusion, this study shows that methanol does not increase the thermostability of prions and the RepCat process can efficiently eliminate prions and is therefore safe for the usage of category 1 tallow. Practical Applications: The study further supports the applicability of RepCat process in reducing prion‐contamination in the presence of methanol. Furthermore, the conditions leads to a considerable reduction of prions in glycerine obtained as by‐product.  相似文献   
105.
Three experiments were carried out to study the effects on problem solving of visualization when subjects (secondary-school students and undergraduates) were instructed to generate mental images before the problem was presented and when they received such a hint after being given the problem. In each experiment an arithmetic, a geometric, and a practical problem were presented in three different conditions, a control condition, an "imagery-before" condition, and an "imagery-after" condition. Analysis showed that, in general, the "imagery-after" task helps subjects to overcome the misleading or fixating tendencies which interfere with problem solution; in contrast, the "imagery-before" task may enhance such tendencies.  相似文献   
106.
According to classical theories, automatic processes are autonomous and independent of higher level cognitive influence. In contrast, the authors propose that automatic processing depends on attentional sensitization of task-congruent processing pathways. In 3 experiments, the authors tested this hypothesis with a modified masked semantic priming paradigm during a lexical decision task by measuring event-related potentials (ERPs): Before masked prime presentation, participants attended an induction task either to semantic or perceptual stimulus features designed to activate a semantic or perceptual task set, respectively. Semantic priming effects on the N400 ERP component, an electrophysiological index of semantic processing, were obtained when a semantic task set was induced immediately before subliminal prime presentation, whereas a previously induced perceptual task set attenuated N400 priming. Across experiments, comparable results were obtained regardless of the difficulty level and the verbal or nonverbal nature of the induction tasks. In line with the proposed attentional sensitization model, unconscious semantic processing is enhanced by a semantic and attenuated by a perceptual task set. Hence, automatic processing of unconscious stimuli is susceptible to top-down control for optimizing goal-related information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
107.
Oncostatin M (OSM), a member of the interleukin-6 family, functions as a major mediator of cardiomyocyte remodeling under pathological conditions. Its involvement in a variety of human cardiac diseases such as aortic stenosis, myocardial infarction, myocarditis, cardiac sarcoidosis, and various cardiomyopathies make the OSM receptor (OSMR) signaling cascades a promising therapeutic target. However, the development of pharmacological treatment strategies is highly challenging for many reasons. In mouse models of heart disease, OSM elicits opposing effects via activation of the type II receptor complex (OSMR/gp130). Short-term activation of OSMR/gp130 protects the heart after acute injury, whereas chronic activation promotes the development of heart failure. Furthermore, OSM has the ability to integrate signals from unrelated receptors that enhance fetal remodeling (dedifferentiation) of adult cardiomyocytes. Because OSM strongly stimulates the production and secretion of extracellular proteins, it is likely to exert systemic effects, which in turn, could influence cardiac remodeling. Compared with the mouse, the complexity of OSM signaling is even greater in humans because this cytokine also activates the type I leukemia inhibitory factor receptor complex (LIFR/gp130). In this article, we provide an overview of OSM-induced cardiomyocyte remodeling and discuss the consequences of OSMR/gp130 and LIFR/gp130 activation under acute and chronic conditions.  相似文献   
108.
Many therapeutic peptides can still be improved with respect to target specificity, target affinity, resistance to peptidases/proteases, physical stability, and capacity to pass through membranes required for oral delivery. Several modifications can improve the peptides’ properties, in particular those that impose (a) conformational constraint(s). Screening of constrained peptides and the identification of hits is greatly facilitated by the generation of genetically encoded libraries. Recent breakthrough bacterial, phage, and yeast display screening systems of ribosomally synthesized post-translationally constrained peptides, particularly those of lanthipeptides, are earning special attention. Here we provide an overview of display systems for constrained, genetically encoded peptides and indicate prospects of constrained peptide-displaying phage and bacterial systems as such in vivo.  相似文献   
109.
Repair of composite structures and the impact of demanding environmental conditions is a crucial issue for the aircraft industry because of the increasing use of composites in modern aircraft. Consequently, the impact of environmental conditions common for aircraft applications on repair specimens in comparison to nonrepaired specimens is studied. All specimens are produced from a woven carbon fiber-reinforced epoxy-based prepreg. For the repair-specimens, an epoxy-based film adhesive is used for the soft patch repair approach. During the repair process, the surface of the precured prepreg is prepared by a mechanical method (sanding) and an additional chemical functionalization, respectively. Moisture absorption of the repair specimens is independent of the surface preparation method and higher for the repaired than for the nonrepaired specimens. The key influencing environmental conditions for the tensile strength and the failure mode of the repair specimens are elevated temperature testing as well as hot/wet conditioning and conditioning in deionized water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47506.  相似文献   
110.
Cazade PA  Lutz S  Lee MW  Meuwly M 《Chimia》2011,65(5):326-329
Physico- and bio-chemical processes on the femto- to picosecond time scale are ideally suited to be investigated with all-atom simulations. They include, amongst others, vibrational relaxation, ligand migration in sterically demanding environments (proteins, ices), or vibrational spectra. By comparing with experimental data, the results can be used to obtain an understanding of the mechanisms underlying the observations. Furthermore, most of these processes are sensitive to the intermolecular interactions. Therefore, detailed refinement of such interaction potentials is possible.  相似文献   
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