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   1073篇
  免费   13篇
  国内免费   4篇
电工技术   47篇
综合类   1篇
化学工业   273篇
金属工艺   22篇
机械仪表   14篇
建筑科学   13篇
能源动力   57篇
轻工业   65篇
水利工程   1篇
无线电   104篇
一般工业技术   165篇
冶金工业   211篇
原子能技术   22篇
自动化技术   95篇
  2023年   8篇
  2022年   14篇
  2021年   19篇
  2020年   9篇
  2019年   13篇
  2018年   11篇
  2017年   13篇
  2016年   17篇
  2015年   10篇
  2014年   30篇
  2013年   43篇
  2012年   38篇
  2011年   50篇
  2010年   38篇
  2009年   46篇
  2008年   50篇
  2007年   40篇
  2006年   32篇
  2005年   39篇
  2004年   28篇
  2003年   35篇
  2002年   28篇
  2001年   23篇
  2000年   23篇
  1999年   28篇
  1998年   85篇
  1997年   50篇
  1996年   52篇
  1995年   20篇
  1994年   22篇
  1993年   27篇
  1992年   11篇
  1991年   6篇
  1990年   11篇
  1989年   13篇
  1988年   8篇
  1987年   5篇
  1986年   12篇
  1985年   10篇
  1984年   13篇
  1983年   7篇
  1982年   10篇
  1981年   7篇
  1980年   5篇
  1979年   4篇
  1978年   4篇
  1977年   4篇
  1976年   7篇
  1975年   4篇
  1971年   2篇
排序方式: 共有1090条查询结果,搜索用时 19 毫秒
21.
In cancer cells, cell-surface sialylation is altered, including a change in oligo/polysialic acid (oligo/polySia) structures. Since they are unique and rarely expressed in normal cells, oligo/polySia structures may serve as promising novel biomarkers and targets for therapies. For the diagnosis and treatment of the disease, a precise understanding of the oligo/polySia structures in cancer cells is necessary. In this study, flow cytometric analysis and gene expression datasets were obtained from sixteen different cancer cell lines. These datasets demonstrated the ability to predict glycan structures and their sialylation status. Our results also revealed that sialylation patterns are unique to each cancer cell line. Thus, we can suggest promising combinations of antibody and cancer cell for glycan prediction. However, the precise prediction of minor glycans need to be further explored.  相似文献   
22.
23.
A new type fluid dynamic bearing spindle motor has been developed for use in a small hard disk drive for mobile applications. Classified as an untied type motor in its basic construction, the new motor is constructed so that it prevents oil leakage and enhances the rigidity of the hard disk drive chassis. The characteristic structural feature of the motor is a hollow rotary spindle through which a stationary shaft is installed. The stationary shaft does not interfere with spindle rotation. Since the stationary shaft is secured between the top cover and base chassis, the motor enhances hard disk drive chassis rigidity, which is an advantage that cannot be achieved by the conventional untied type motor. Although measuring small and thin, the motor has excellent rotational accuracy and shock resistance.  相似文献   
24.
Structure and viscoelastic properties of segmented polyurethanurea (SPU) blends were investigated. The glass transition temperature (Tg) of poly(tetramethylene glycohol) (PTMG) in a soft-segment block of the component SPU increased with decreasing molecular weight of PTMG. The blend samples showed two Tgs of PTMG in the temperature dispersions of the loss modulus (E″) and loss tangent (tan δ). The value of E′ in the leathery region for the blend specimens was trongly affected by the morphology. The blends were considered to have a morphology where PTMG differing in molecular weight was localized. © 1996 John Wiley & Sons, Inc.  相似文献   
25.
Microbial synthesis of copolymers of [R]-3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB), P(3HB-co-4HB), by Alcaligenes eutrophus, Alcaligenes latus, and Comamonas acidovorans from various carbon sources has been studied. The copolyester compositions varied from 0 to 100 mol% 4HB, depending on the microorganism and the combination of carbon substrates supplied. The thermal and physical properties of compositions with 0–100 mol% 4HB were investigated. The copolyesters represented a wide variety of polymeric materials, from hard crystalline plastic to very elastic rubbers, depending on composition. The copolyester films with high 4HB fractions (64–100 mol% 4HB) exhibited the characteristics of a thermoplastic elastomer, and the tensile strength increased from 17 to 104 MPa as the 4HB fraction increased. The enzymatic degradation of P(3HB-co-4HB) films was studied in an aqueous solution of extracellular polyhydroxybutyrate (PHB) depolymerase from Alcaligenes faecalis or lipase from Rhizopus delemer. The erosion rate of P(3HB-co-4HB) films was strongly dependent on the copolymer composition. In addition, environmental degradation of P(3HB-co-4HB) films in sea water was investigated.  相似文献   
26.
On May 2008, Kyoto city government set up a low-carbon target of a 50% GHG reduction by 2030 compared to the 1990 level. To contribute to these discussions, we developed a local (city-scale) low-carbon scenario creation method. An estimation model was developed to show a quantitative and consistent future snapshot. The model can explicitly treat the uncertainty of future socio-economic situations, which originate from the openness of local economy. The method was applied to Kyoto city, and countermeasures to achieve the low-carbon target were identified. Without countermeasures, emissions would increase 12% from 2000. Among the measures, the reduction potential of energy efficiency improvements to residential and commercial sectors was found to be relatively large (15% and 18% of total reductions, respectively). The reduction potential of the passenger transport sector, in which the city government's policy is especially important, was 17% of the total amount. A sensitivity analysis showed that a 10% increase in exports leads to an 8.5% increase in CO2 emissions, and a 20% increase in the share of the commuters from outside the city leads to a 3.5% decrease of CO2 emissions because of the smaller number of residents in the city.  相似文献   
27.
Using the electrochemical deposition (ECD) method, we prepared tin sulfide thin films, which are suitable for the absorption layer in solar cells because of its bandgap energy (1 eV). We first optimized pulse-form biasing for ECD by characterizing deposited samples with scanning electron microscope, Auger electron spectroscopy and X-ray diffraction measurements. Then, we investigated the electrical properties of deposited SnS thin films and the properties of contacts with several different metals. Furthermore, we observed the photoconductivity of the films by means of photoelectrochemical measurements. From these results, we confirmed that the SnS thin films show p-type conduction.  相似文献   
28.
In order to determine appropriate value for threshold stress intensity factor for hydrogen-assisted cracking (KIH), constant-displacement and rising-load tests were conducted in high-pressure hydrogen gas for JIS-SCM435 low alloy steel (Cr-Mo steel) used as stationary storage buffer of a hydrogen refuelling station with 0.2% proof strength and ultimate tensile strength equal to 772 MPa and 948 MPa respectively. Thresholds for crack arrest under constant displacement and for crack initiation under rising load were identified. The crack arrest threshold under constant displacement was 44.3 MPa m1/2 to 44.5 MPa m1/2 when small-scale yielding and plane-strain criteria were satisfied and the crack initiation threshold under rising load was 33.1 MPa m1/2 to 41.1 MPa m1/2 in 115 MPa hydrogen gas. The crack arrest threshold was roughly equivalent to the crack initiation threshold although the crack initiation threshold showed slightly more conservative values. It was considered that both test methods could be suitable to determine appropriate value for KIH for this material.  相似文献   
29.
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.  相似文献   
30.
Flameless combustion is considered as a flexible and efficient combustion process for low heating value gas fuel. This paper presents numerical simulations of premixed flameless combustion using producer gas as a fuel. Different initial conditions of the premixed fresh reactant (air/fuel mixture) and dilution levels are taken into account for the investigation. The numerical simulations were investigated using a network of chemical reactor models with the detailed reaction mechanism of GRI‐Mech 3.0. A threshold dilution level for flameless combustion fuelled by producer gas was determined. The numerical results show that dilution of the fresh reactant with hot combustion products and initial fresh reactant temperature play important roles in flameless combustion formation and its auto‐ignition behaviour, rather than equivalence ratio of the fresh reactant. In the flameless combustion regime, temperature and chemical concentrations were reduced while chemical kinetics process was decelerated, resulting in delay of the auto‐ignition process.  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