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   466篇
  免费   23篇
  国内免费   1篇
电工技术   6篇
化学工业   106篇
金属工艺   25篇
机械仪表   14篇
建筑科学   21篇
能源动力   12篇
轻工业   72篇
水利工程   2篇
石油天然气   6篇
无线电   13篇
一般工业技术   72篇
冶金工业   47篇
原子能技术   11篇
自动化技术   83篇
  2024年   3篇
  2023年   5篇
  2022年   10篇
  2021年   14篇
  2020年   16篇
  2019年   19篇
  2018年   16篇
  2017年   19篇
  2016年   27篇
  2015年   15篇
  2014年   26篇
  2013年   54篇
  2012年   37篇
  2011年   34篇
  2010年   12篇
  2009年   24篇
  2008年   14篇
  2007年   22篇
  2006年   15篇
  2005年   13篇
  2004年   16篇
  2003年   16篇
  2002年   11篇
  2001年   9篇
  2000年   5篇
  1999年   2篇
  1998年   10篇
  1997年   6篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   2篇
  1989年   1篇
  1988年   2篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1968年   1篇
排序方式: 共有490条查询结果,搜索用时 78 毫秒
31.
Scope: Cancer cachexia is characterized by muscle and adipose tissue wasting caused partly by chronic, systemic inflammation. Conjugated linoleic acids (CLAs) are a group of fatty acids with various properties including anti‐inflammatory cis9, trans11 (c9t11)‐CLA and lipid‐mobilizing trans10, cis12 (t10c12)‐CLA. The purpose of this study was to test whether dietary supplementation of a c9t11‐CLA‐rich oil (6:1 c9t11:t10c12) could attenuate wasting of muscle and adipose tissue in colon‐26 adenocarcinoma‐induced cachexia in mice. Methods and results: Loss of body weight, muscle and adipose tissue mass caused by tumors were not rescued by supplementation with the c9t11‐CLA‐rich oil. In quadriceps muscle, c9t11‐CLA‐rich oil exacerbated tumor‐induced gene expression of inflammatory markers tumor necrosis factor‐α, IL‐6 receptor and the E3 ligase MuRF‐1 involved in muscle proteolysis. In epididymal adipose tissue, tumor‐driven delipidation and atrophy was aggravated by the c9,t11‐CLA‐rich oil, demonstrated by further reduced adipocyte size and lower adiponectin expression. However, expression of inflammatory cytokines and macrophage markers were not altered by tumors, or CLA supplementation. Conclusion: These data suggest that addition of c9t11‐CLA‐rich oil (0.6% c9t11, 0.1% t10c12) in diet did not ameliorate wasting in mice with cancer cachexia. Instead, it increased expression of inflammatory markers in the muscle and increased adipose delipidation.  相似文献   
32.
The synthesis and characterization of the resin Amberlite XAD-4 functionalized with 2,6-pyridinedicarboxaldehyde and its application in an on-line system for the preconcentration of cadmium, cobalt, copper, lead and manganese prior to determination using flame atomic absorption spectrometry (FAAS) is proposed. Metal ions retained on the modified resin were eluted using 1.0 mol L−1 HNO3 solution and aspirated directly to the nebulizer–burner system of a FAAS instrument using a flow injection system. Detection limits (3σ) were determined to be 0.13 μg L−1 for Cd, 0.29 μg L−1 for Cu, 0.23 μg L−1 for Mn, 0.58 μg L−1 for Co and 2.19 μg L−1 for Pb using a 10 mL of water sample loading volume. The limits of detection would be 100 times higher with units of μg kg−1 for the solid samples in which their dilution ratios as (volume/weight) were 100. Enrichment factors ranged from 23.6 to 28.9 (for Co and Mn, respectively). The proposed method was successfully applied to determination of the analytes in natural water samples and certified reference materials.  相似文献   
33.
The aim of this study was to prepare magnetic beads that could be used for the removal of heavy‐metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [m‐poly(EGDMA–VTAZ)] beads were produced by suspension polymerization in the presence of a magnetite Fe3O4 nanopowder. The specific surface area of the m‐poly(EGDMA–VTAZ) beads was 74.8 m2/g with a diameter range of 150–200 μm, and the swelling ratio was 84%. The average Fe3O4 content of the resulting m‐poly(EGDMA–VTAZ) beads was 14.8%. The maximum binding capacities of the m‐poly(EGDMA–VTAZ) beads from aquous solution were 284.3 mg/g for Hg2+, 193.8 mg/g for Pb2+, 151.5 mg/g for Cu2+, 128.1 mg/g for Cd2+, and 99.4 mg/g for Zn2+. The affinity order on a mass basis was Hg2+ > Pb2+ > Cu2+ > Cd2+> Zn2+. The binding capacities from synthetic waste water were 178.1 mg/g for Hg2+, 132.4 mg/g for Pb2+, 83.5 mg/g for Cu2+, 54.1 mg/g for Cd2+, and 32.4 mg/g for Zn2+. The magnetic beads could be regenerated (up to ca. 97%) by a treatment with 0.1M HNO3. These features make m‐poly(EGDMA–VTAZ) beads potential supports for heavy‐metal removal under a magnetic field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   
34.
Azcan N  Kara M  Demirci B  Başer KH 《Lipids》2004,39(5):487-489
Seed oils of Origanum onites L. from the Antalya and Mugla regions and O. vulgare L. from the Kirklareli region of Turkey were extracted with hexane in a Soxhlet apparatus. The oil yields were 14.1–20.0 and 18.5%, respectively. FA compositions of the seed oils were determined by GC and GC/MS. Twenty FA were identified in both O. onites and O. vulgare seeds. The major FA of both species were linolenic (56.3–57.0%; 61.8%), linoleic (21.5–21.7%; 18.8%), oleic (8.7–8.9%; 5.9%), palmitic (5.9–6.5%; 5.5%), stearic (2.1–2.4%; 2.1%), and (Z)-11-octadecenoic (0.6–0.8%; 0.5%), respectively.  相似文献   
35.
In this study, the effects of deep cryogenic treatment (DCT) on the wear resistance of AISI 52100 bearing steel were investigated. For this purpose, a number of bearing steel samples were held for different times (12, 24, 36, 48, 60 h) at deep cryogenic temperatures (?145 °C). The wear experiments were carried out in a ball–disk arrangement, by applying loads of 10 and 20 N and a sliding velocity of 0.15 m/s. After conducting the experimental studies, 36 h was found to be the optimal holding time. At this holding time, the wear rate and friction coefficient were decreased, while the hardness reached to maximum values. It was observed that DCT led to significant microstructural changes, which resulted in improved tribological properties.  相似文献   
36.
Advanced fusion structural materials (FSMs) have impact role in terms of efficiency of nuclear energy production. Besides engineering and design of fusion reactors, radiation durability of FSMs is another valuable issue that cannot be ignored. 17.9–22.3 MeV proton irradiation of bcc-Zirconium Fusion Structural Material was evaluated by using Monte Carlo based simulation tools. Total binary reaction cross sections were respectively calculated as 1167.6 and 1273.92 mb for 17.3- and 22.3 MeV proton energies via TALYS-1.6 version. Additionally, residual production cross sections and total particle production cross sections were obtained and analyzed by the TALYS code. Radiation damage parameters as Displacement Per Atom (DPA) and Stopping Power (SP) were studied by SRIM-2013 version. FLUKA 2011.1 used for only DPA calculations and making a complete comparison with the other calculation results. SP and Number of Secondaries were found by using GEANT4.10.p.04 version simulations. Natural Zr(p,x) reactions were studied in the given energy values in the plane of reaction probability and radiation damage calculations.  相似文献   
37.
In this paper, we investigate service‐level assurance in high‐availability multi‐unit systems using the M‐for‐N backup scheme. M‐for‐N shared protection (backup) systems with priority control (i.e. prioritized protection switching and prioritized re‐housing of repaired units) can be applied to actual telecommunication devices that are subject to service‐level agreement (SLA) involving reliability measures. A priority level is assigned to each end user in such a system and the switching and unit re‐housing process is subject to the priority. The main contribution of this paper is to give a practical computation method of the user‐perceived availability under the priority control. Our case studies for real telecommunication systems reveal the effect of priority control on the user‐perceived availability. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
38.
In situ photon transmission experiments were performed using UV‐visible (UVV) spectrometer during the drying of polyacrylamide (PAAm) gels. These gels are formed from acrylamide (AAm) with various N,N′‐methylenebis(acrylamide) (Bis) contents by free radical crosslinking copolymerization (FCC) in water. The transmitted light intensity, Itr increased continuously as PAAm gels are dried. Increase in Itr was attributed to the decrease in the scattered light intensity, Isc, which might be originated from the contrast between “frozen blob clusters” and holes in the drying gel. Decrease in Isc was modeled using Rayleigh's equation, where drying times with various exponents were found to be proportional to the volume of frozen blob clusters. It was observed that the radius of frozen blob cluster (correlation length), ξc increased in various power of time, depending on Bis contents during drying of gels. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1898–1906, 2001  相似文献   
39.
40.
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