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   1414篇
  免费   64篇
  国内免费   3篇
电工技术   76篇
综合类   3篇
化学工业   433篇
金属工艺   55篇
机械仪表   23篇
建筑科学   22篇
矿业工程   1篇
能源动力   81篇
轻工业   110篇
水利工程   4篇
石油天然气   3篇
无线电   89篇
一般工业技术   342篇
冶金工业   47篇
原子能技术   45篇
自动化技术   147篇
  2023年   8篇
  2022年   19篇
  2021年   38篇
  2020年   17篇
  2019年   37篇
  2018年   40篇
  2017年   33篇
  2016年   49篇
  2015年   39篇
  2014年   38篇
  2013年   77篇
  2012年   80篇
  2011年   107篇
  2010年   68篇
  2009年   86篇
  2008年   81篇
  2007年   69篇
  2006年   45篇
  2005年   47篇
  2004年   56篇
  2003年   42篇
  2002年   37篇
  2001年   34篇
  2000年   18篇
  1999年   27篇
  1998年   23篇
  1997年   30篇
  1996年   23篇
  1995年   11篇
  1994年   16篇
  1993年   19篇
  1992年   18篇
  1991年   25篇
  1990年   11篇
  1989年   14篇
  1988年   5篇
  1987年   9篇
  1986年   7篇
  1985年   7篇
  1984年   9篇
  1983年   6篇
  1982年   8篇
  1981年   5篇
  1980年   9篇
  1979年   7篇
  1978年   5篇
  1977年   4篇
  1976年   3篇
  1975年   5篇
  1973年   3篇
排序方式: 共有1481条查询结果,搜索用时 15 毫秒
101.
Catalytic NO–H2–CO–O2 reaction was studied over Pt-supported Ln-incorporated FSM-16 (Ln = La, Ce and Pr). Pr-FSM-16 exhibited the highest activity for NO x reduction at ≤200 °C. Pr has an effect of increasing the basicity to promote the oxidative adsorption of NO, which is a key for efficient de-NO x .  相似文献   
102.
Reaction between epoxidized natural rubber and poly(L ‐lactide) (PLLA) was investigated quantitatively in terms of conversion of the epoxidized natural rubber. The epoxidized natural rubber was prepared by epoxidation of high ammonia natural rubber (HA‐NR) or deproteinized natural rubber (DPNR) with peracetic acid followed by depolymerization with ammonium persulfate. The resulting liquid HA‐NR having epoxy group (LENR) or liquid DPNR having epoxy group (LEDPNR) were subjected to heating at 473 K for 20 min, after blending with PLLA. The products were characterized through morphology observation, DSC measurement, and 1H‐NMR spectroscopy. The conversions of the rubbers were estimated from intensity ratio of signals in 1H‐NMR spectrum for the products after removing unreacted rubber with toluene. Difference in the estimated conversion between the LENR/PLLA and LEDPNR/PLLA blends was interpreted in relation to proteins present in the rubber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   
103.
104.
The present study systemically decolorized soy sauce using a membrane process to analyze the separation mechanism. An ultrafiltration (UF) membrane (NTU-2120) exhibited only slight decolorization ability. A nanofiltration (NF) membrane with a lower molecular weight cut-off and produced by sulfonated polysulfone (NTR-7400 series) rather than polyvinyl alcohol/polyamide (NTR-7250) had higher decolorization ability. The NF membranes rejected total nitrogen by 17–24%, unsalted soluble solid content by 24–32%, reducing sugar by 25–43%, and amino acids by 10–25%. The NTR-7400 series membrane rejected lactic acid by 6–9%, and pyroglutamic acid by 11–21%; other quality indexes were maintained. In the NF membrane processes, higher rejection of acidic amino acids than neutral and base amino acids was observed. The separation performance was governed by the electrical effect as well as the sieve effect. Soy sauce color could be controlled by blending NF membrane-processed soy sauce with feed soy sauce. Color can be matched to preference in accordance with dishes by suitably blending NF membrane-processed soy sauce with feed soy sauce.  相似文献   
105.
The rate at which a facetted tetragonal cavity of nonequilibrium shape approaches a cubic equilibrium (Wulff) shape via surface diffusion was modeled. The shape relaxation rate of a facetted stretched cylinder was also modeled. For the first geometry, only an approximate solution based on linearizing the mean potential difference between the source and sink facets was obtained. For the stretched cylinder, both an approximate and an exact solution can be obtained; the approximate solution underestimates the evolution rate by a factor of ∼2. To assess the applicability of the models, nonequilibrium shape pores of identical initial geometry (∼20 μm × 20 μm × 0.5 μm) were introduced into (0001), {10[Onemacr]2}, {1120}, and {100} surfaces of sapphire single crystals using microfabrication techniques, ion-beam etching, and hot pressing. The large (∼20 μm × 20 μm) faces of the pore are low-index surfaces whose nature is dictated by the wafer orientation. A series of anneals was performed at 1900°C, and the approach of the pore shape to an equilibrium shape was monitored. The kinetics of shape evolution are highly sensitive to the crystallographic orientation and stability of the low-index surface that dominates the initial pore shape. The measured variations of the pore aspect ratio were compared to those predicted by the kinetic model. The observations suggest that when the initial bounding surface is unstable, shape relaxation may be controlled by diffusion. However, surface-attachment-limited kinetics (SALK) appears to play a major role in determining the pore shape evolution rate in cases where the initial bounding surfaces have orientations that are part of the Wulff shape.  相似文献   
106.
The kinetics of enthalpy relaxation (recovery) at the glass transition in x K2O·(20− x )MgO·80TeO2 glasses has been examined from heat capacity measurements using differential scanning calorimetry to clarify the features of the structural relaxation in ternary TeO2-based glasses. Ternary glasses such as 10K2O·10MgO·80TeO2 show high thermal resistance against crystallization compared with binary glasses. The degree of fragility m estimated from the activation energy for viscous flow E η and the glass transition temperature T g is m = 55–62, indicating a fragile character in TeO2-based glasses. Large heat capacity changes of 43.1–48.2 J·mol−1·K−1 are also observed at the glass transition. The activation energy for enthalpy relaxation Δ H is evaluated from the cooling rate dependence of the limiting fictive temperature, and values of Δ H = 897–1268 kJ·mol−1 are obtained. Negative deviation from additivity in Δ H is also observed. Values of the Kovacs–Aklonis–Huchinson–Ramos (KAHR) parameter θ estimated from Δ H and T g are 0.33–0.42 K−1. It has been proposed that ternary glasses have more homogeneous and constrained glass structure compared with binary glasses.  相似文献   
107.
Stress fields on elastic-creep bi-material interfaces with different geometry of the interface edge are analyzed by finite element method. The results reveal that the stress highly concentrates near the interface edge at the loading instant and it gradually decreases as the creep-dominated zone expands from the small-scale creep to the large-scale creep. The stress singularity due to creep which resembles the HRR stress singularity appears near the interface edge in all cases. The stress intensity near the interface edge time-dependently decreases and becomes constant when the transition reaches the steady state. The magnitude is scarcely influenced by the edge shape of elastic material, though it depends on the edge shape of creep material. The stress intensity during the transition can be approximately predicted by the J-integral at the loading instant.  相似文献   
108.
In this study, white organic electroluminescent devices with microcavity structures were developed. A flexible high‐resolution active‐matrix organic light‐emitting diode display with low power consumption using red, green, blue, and white sub‐pixels formed by a color‐filter method was fabricated. In addition, a side‐roll touch display was developed in combination with a capacitive flexible touch screen.  相似文献   
109.
Uphill transport of ammonium ions through a membrane with sulfonic acid groups were investigated with pH-controllers which keep the solution at a constant pH. A membrane with sulfonic acid groups was prepared by casting an aqueous solution containing poly(styrenesulfonic acid) and poly(vinyl alcohol) on a glass plate. When a membrane with one side alkaline and the other acidic was fixed as a diaphragm in a cell, ammonium ions were transported from the alkaline side to the acidic side through the membrane against the concentration gradient of the adjacent solutions. Uphill transport of ammonium ions with pH-controllers was more efficient than without, thus keeping the pH difference between both sides of the membrane constant, which is a driving force for the uphill transport. Furthermore, the effect of pH of the acidic side on the uphill transport was investigated and the mechanism of the pH-controlled uphill transport is discussed.  相似文献   
110.
In order for ultra-large-integrated (ULSI) circuits manufacturing to minimize the Cost of Ownership (CoO) aspect in the wiring process and realize fabricating semiconductor devices over 100 nm node, several Cu/low-k wiring technologies have been proposed. The evidential criteria in choosing the most probable one are physical or material limitation and requirements from manufacturing. A development of module processes (e.g., processing from low-k dielectrics to metal CMP) with proven equipment and material is an appropriate approach and has a high potential in overcoming those difficulties. In this paper, an advantage of dual Damascene Cu wiring accompanied with low-k (dielectric constant ∼2.7) and prediction of 100 nm Cu wiring module will be discussed.  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