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   1355篇
  免费   67篇
  国内免费   2篇
电工技术   41篇
化学工业   396篇
金属工艺   13篇
机械仪表   30篇
建筑科学   41篇
矿业工程   3篇
能源动力   74篇
轻工业   154篇
石油天然气   2篇
无线电   110篇
一般工业技术   293篇
冶金工业   41篇
原子能技术   10篇
自动化技术   216篇
  2023年   10篇
  2022年   45篇
  2021年   85篇
  2020年   37篇
  2019年   36篇
  2018年   46篇
  2017年   27篇
  2016年   48篇
  2015年   47篇
  2014年   53篇
  2013年   111篇
  2012年   91篇
  2011年   105篇
  2010年   94篇
  2009年   63篇
  2008年   71篇
  2007年   53篇
  2006年   56篇
  2005年   43篇
  2004年   43篇
  2003年   32篇
  2002年   35篇
  2001年   14篇
  2000年   20篇
  1999年   15篇
  1998年   23篇
  1997年   14篇
  1996年   13篇
  1995年   15篇
  1994年   9篇
  1993年   10篇
  1992年   8篇
  1991年   7篇
  1990年   3篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   2篇
  1985年   2篇
  1983年   2篇
  1982年   4篇
  1981年   2篇
  1980年   2篇
  1976年   3篇
  1973年   1篇
  1972年   6篇
  1971年   1篇
  1970年   2篇
  1968年   1篇
  1965年   1篇
排序方式: 共有1424条查询结果,搜索用时 15 毫秒
991.
In this paper we present an empirical analysis of the residential demand for electricity using annual aggregate data at the state level for 48 US states from 1995 to 2007. Earlier literature has examined residential energy consumption at the state level using annual or monthly data, focusing on the variation in price elasticities of demand across states or regions, but has failed to recognize or address two major issues. The first is that, when fitting dynamic panel models, the lagged consumption term in the right-hand side of the demand equation is endogenous. This has resulted in potentially inconsistent estimates of the long-run price elasticity of demand. The second is that energy price is likely mismeasured.To address these issues, we estimate a dynamic partial adjustment model using the Kiviet corrected Least Square Dummy Variables (LSDV) (1995) and the Blundell–Bond (1998) estimators. We find that the long-term elasticities produced by the Blundell–Bond system GMM methods are largest, and that from the bias-corrected LSDV are greater than that from the conventional LSDV. From an energy policy point of view, the results obtained using the Blundell–Bond estimator where we instrument for price imply that a carbon tax or other price-based policy may be effective in discouraging residential electricity consumption and hence curbing greenhouse gas emissions in an electricity system mainly based on coal and gas power plants.  相似文献   
992.
The Cavity Beam Position Monitor (BPM) is a beam diagnostic instrument which, in a seeded Free Electron Laser (FEL), allows the measurement of the electron beam position in a non-destructive way and with sub-micron resolution. It is composed by two resonant cavities called reference and position cavity, respectively. The measurement exploits the dipole mode that arises when the electron bunch passes off axis. In this paper we describe the Cavity BPM that has been designed and realized in the context of the FERMI@Elettra project [1]. New strategies have been adopted for the microwave design, for both the reference and the position cavities. Both cavities have been simulated by means of Ansoft HFSS [2] and CST Particle Studio [3], and have been realized using high precision lathe and wire-EDM (Electro-Discharge) machine, with a new technique that avoids the use of the sinker-EDM machine. Tuners have been used to accurately adjust the working frequencies for both cavities. The RF parameters have been estimated, and the modifications of the resonant frequencies produced by brazing and tuning have been evaluated. Finally, the Cavity BPM has been installed and tested in the presence of the electron beam.  相似文献   
993.
994.
This preliminary study aimed at assessing whether the in vitro proliferation of peripheral blood mononuclear cells in response to lipopolysaccharide permits individual characterization of periparturient dairy cows, and whether this parameter may be associated with incidence of infections and with some of the single nucleotide polymorphisms located on the toll-like receptor 4 (TLR4) gene. Based on the average response of peripheral blood mononuclear cells to lipopolysaccharide over 7 time points during the transition period, 31 cows were categorized as low (LO), medium (MED), and high (HI) responders. This categorization identified 7 HI, 19 MED, and 5 LO cows, respectively. Genomic DNA was genotyped for P-226 C>G and E3+2021 C>T TLR4 single nucleotide polymorphisms. Monitoring of the health status revealed that 8 of the 31 cows suffered from clinical mastitis, metritis, or interdigital dermatitis during the first 60 d in milk. The association study pointed out that none of the HI cows and all of the LO cows developed an infection; cows with the CCGT haplotype remained healthy and none of them belonged to the LO responder category.  相似文献   
995.
996.
The approach to the development of a chemically and physically consistent mathematical model of ASC dual-layer (SCR + PGM) washcoated monolith converters is herein presented. Steady-state and transient kinetic runs were performed over each one of the two ASC components (SCR and PGM) in the form of powders and also over the two mixed powdered catalysts, thus acquiring information on the interactions between the SCR and the PGM catalytic chemistries. Global kinetic models were fitted to the SCR and to the PGM catalyst data, and validated against experiments performed over both washcoated single-layered SCR and PGM monoliths and over a full dual-layer ASC honeycomb catalyst (SCR layer on top). It was found that the dual-layer (SCR + PGM) ASC architecture grants increased N2 selectivities compared to a PGM-only washcoat.  相似文献   
997.
The ATP2C1 gene encodes for the secretory pathway calcium (Ca2+)-ATPase pump (SPCA1), which localizes along the secretory pathway, mainly in the trans-Golgi. The loss of one ATP2C1 allele causes Hailey-Hailey disease in humans but not mice. Examining differences in genomic organization between mouse and human we speculate that the overlap between ATP2C1 and ASTE1 genes only in humans could explain this different response to ATP2C1 dysregulation. We propose that ASTE1, overlapping with ATP2C1 in humans, affects alternative splicing, and potentially protein expression of the latter. If dysregulated, the composition of the SPCA1 isoform pool could diverge from the physiological status, affecting cytosolic Ca2+-signaling, and in turn perturbing cell division, leading to cell death or to neoplastic transformation.  相似文献   
998.
An innovative ellipsometer sample holder has been designed and tested in order to measure thin films optical properties under different environments and so infer the porosity through effective medium approximation models. Compared to commercial cells that require a fixed angle of incidence or a cell with a cylindrical geometry, we present a simple cell in which the sample is mounted in “reverse side”, allowing multiple angle analyses without the need for cell windows. Standard ellipsometry measurements are compared to the “reverse side” approach in order to confirm the feasibility of this new procedure, obtaining the same refractive index dispersion curves in both cases. Then different samples have been tested in “reverse side” under different environments to measure porosity. The multiangle approach has been found useful to improve the fitting of the experimental data by reducing both the fitting error and the correlation between parameters.  相似文献   
999.
Melatonin exerts its actions through membrane MT1/MT2 melatonin receptors, which belong to the super family of G-protein-coupled receptors consisting of the typical seven transmembrane domains. MT1 and MT2 receptors are expressed in various tissues of the body either as single ones or together. A growing literature suggests that the melatonergic system may be involved in the pathophysiology of mood and anxiety disorders. In fact, some core symptoms of depression show disturbance of the circadian rhythm in their clinical expression, such as diurnal mood and other symptomatic variation, or are closely linked to circadian system functioning, such as sleep-wake cycle alterations. In addition, alterations have been described in the circadian rhythms of several biological markers in depressed patients. Therefore, there is interest in developing antidepressants that have a chronobiotic effect (i.e., treatment of circadian rhythm disorders). As melatonin produces chronobiotic effects, efforts have been aimed at developing agomelatine, an antidepressant with melatonin agonist activity. The present paper reviews the role of the melatonergic system in the pathophysiology of mood and anxiety disorders and the clinical characteristics of agomelatine. Implications of agomelatine in “real world” clinical practice will be also discussed.  相似文献   
1000.
Molecular dynamics simulations by a tight binding potential provide new interesting information on the ground state properties of the TiSi2 phases. In particular, we have compared some structural, elastic, thermodynamic and electronic properties of the C49, the C54 and the amorphous phases. It turns out that the C49 structure is much softer than the C54, also displaying a melting temperature some 300–400 K below the one for the C54, in agreement to very recent experimental results. The amorphous phase is energetically and structurally more akin to the C49 than to the C54 phase. On the basis of these results we suggest the higher formation kinetics of the former to be related to an intrinsic advantage in the growth stage.  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