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   837篇
  免费   0篇
  国内免费   1篇
电工技术   1篇
综合类   6篇
化学工业   78篇
金属工艺   3篇
机械仪表   29篇
建筑科学   65篇
能源动力   1篇
轻工业   122篇
水利工程   8篇
石油天然气   4篇
无线电   15篇
一般工业技术   464篇
冶金工业   3篇
自动化技术   39篇
  2021年   1篇
  2013年   1篇
  2012年   117篇
  2011年   167篇
  2010年   36篇
  2009年   19篇
  2008年   105篇
  2007年   81篇
  2006年   72篇
  2005年   57篇
  2004年   36篇
  2003年   22篇
  2002年   23篇
  2001年   21篇
  2000年   11篇
  1999年   10篇
  1998年   10篇
  1997年   6篇
  1996年   5篇
  1995年   1篇
  1994年   3篇
  1992年   2篇
  1991年   3篇
  1990年   4篇
  1989年   7篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1983年   4篇
  1982年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1973年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有838条查询结果,搜索用时 46 毫秒
11.
A simple regression method for quantifying endogenous leucine in S30 extract was developed. This method enabled the quantity of translated protein in a cell-free protein synthesis system to be exactly determined.  相似文献   
12.
Foxtail millet is one of the world's oldest cultivated crops. It has been adopted as a model organism for providing a deeper understanding of plant biology. In this study, 45 simple sequence repeats (SSR) markers of Setaria italica were developed. These markers showing polymorphism were screened in 223 samples from 12 foxtail millet populations around Taiwan. The most common dinucleotide and trinucleotide repeat motifs are AC/TG (84.21%) and CAT (46.15%). The average number of alleles (N(a)), the average heterozygosities observed (H(o)) and expected (H(e)) are 3.73, 0.714, 0.587, respectively. In addition, 24 SSR markers had shown transferability to six related Poaceae species. These new markers provide tools for examining genetic relatedness among foxtail millet populations and other related species. It is suitable for germplasm management and protection in Poaceae.  相似文献   
13.
The sex pheromone of Synanthedon bicingulata (Staudinger), a major pest of Prunus species in many regions of northeast Asia, was identified. Two major components from the pheromone gland extracts of female moths are (E,Z)-3,13-octadecadienyl acetate (E3,Z13-18:OAc) and (Z,Z)-3,13-octadecadienyl acetate (Z3,Z13-18:OAc), and the average ratio of these components is about 4:6, respectively. In addition to the major components, four minor components, (Z)-13-octadecenyl acetate (Z13-18:OAc), (E,Z)-2,13-octadecadienyl acetate (E2,Z13-18:OAc), (E,Z)-3,13-octadecadien-1-ol (E3,Z13-18:OH), and (Z,Z)-3,13-octadecadien-1-ol (Z3,Z13-18:OH) also were identified from pheromone gland extracts. Field tests showed that E3,Z13-18:OAc and Z3,Z13-18:OAc are essential for attraction of male S. bicingulata moths, and males are optimally attracted to the blend ratio found in pheromone gland extracts of conspecific females. Addition of the minor glandular components (Z13-18:OAc, E2,Z13-18:OAc, E3,Z13-18:OH, and Z3,Z13-18:OH) did not affect captures of males to the primary binary blend. Thus, the blend of E3,Z13-18:OAc and Z3,Z13-18:OAc at the natural ratio can be used for monitoring populations of this species.  相似文献   
14.
Myo-inositol trispyrophosphate (ITPP), a synthetic allosteric effector of hemoglobin, increases the regulated oxygen-releasing capacity of red blood cells (RBCs), leading to suppression of hypoxia-inducible factor 1α (HIF-1α) and to down-regulation of hypoxia-inducible genes such as vascular endothelial growth factor (VEGF). As a consequence, tumor growth is markedly affected. The effect of weekly intravenous injection of ITPP on an orthotopic, syngenic rat hepatocellular carcinoma (HCC) model was compared to that for untreated animals and animals subjected to conventional Doxorubicin chemotherapy. The longitudinal examination of HCC was performed by microCT imaging, and the cellular and molecular changes were evaluated by histology and Western blotting analysis of HIF-1α, VEGF, and caspase-3 gene expression in the tumor and in the surrounding liver. Hematologic impact was evaluated by blood cell-count measurement and determination of P50 (oxygen partial pressure for a 50 % oxygen saturation of hemoglobin). The HCC evaluation by microCT revealed a high potency of ITPP for tumor growth inhibition, thus allowing long-term survival and even cure of almost all the treated animals. The P50 value of hemoglobin in RBCs underwent a shift of 30 % following ITPP injection. Under these conditions, HIF-1α activity was strongly decreased, VEGF expression was down-regulated, and apoptosis was induced in HCC and surrounding liver cells, as indicated by Caspase-3 expression. ITPP did not affect hematologic parameters during treatment. The observations of in vivo tumor eradication suggest a significant clinical potential for ITPP in cancer therapy.  相似文献   
15.
Tan CY  Zhong RZ  Tan ZL  Han XF  Tang SX  Xiao WJ  Sun ZH  Wang M 《Lipids》2011,46(3):239-247
This study was conducted to examine dietary tea catechins (TC) supplementation on the fatty acid composition of muscle and ruminal bacteria in goats fed a maize stover-based diet. Forty goats, 8 months old (16.2 ± 1.2 kg), were randomly divided into four equal groups (10 animals in each group) and assigned to four experiment diets with TC supplementation at four levels (0, 2,000, 3,000 and 4,000 mg TC/kg feed, namely TC0, TC2000, TC3000 and TC4000, respectively). After a 60-day feeding period, all the goats were slaughtered and sampled. The results showed that dietary TC inclusion increased the average daily gain (ADG), protein content in the semimembranosus muscle and dry matter in the longissimus dorsi muscle (LD). Dietary TC supplementation increased the ratio of n-6 to n-3 fatty acid, the ratio of polyunsaturated fatty acids to saturated fatty acids was higher in TC3000 and TC4000 than in TC0 and TC2000 for LD. The current results implied that dietary inclusion of a suitable TC dose could improve the growth performance and increase the proportions of unsaturated fatty acids in muscle, and the biohydrogenation of ruminal microorganisms might change the profiles of fatty acids in the muscle of growing goats.  相似文献   
16.
Gao JM  Wang CY  Zhang AL  Liu JK 《Lipids》2001,36(12):1365-1370
From the chloroform/methanol extract of the fruiting bodies of the ascomycete Chinese truffle Tuber indicum Cooke et Massee, a new trihydroxylated monounsaturated fatty acid (1) has been isolated. The structure of this new linoleic acid-derived metabolite was established as 9,10,11-trihydroxy-(12Z)-12-octadecenoic acid by means of spectroscopic and chemical methods. The fatty acid composition of the chloroform-soluble fraction of this fungus was analyzed by gas chromatography-mass spectrometry. The content of the predominant unsaturated fatty acids (oleic and linoleic acids) is as high as 68%. The use of dimethyl disulfide adduct was effective in the determination of the position of the double bond, and the glycol oxidation fission reaction with sodium metaperiodate supported on silica gel was helpful in establishing the location of the trihydroxylic groups in the new fatty acid.  相似文献   
17.
ABSTRACT: BACKGROUND: Previous studies reported divergent results on nutraceutical actions and free radical scavenging capability of ginseng extracts. Variations in ginsenoside profile of ginseng due to different soil and cultivating season may contribute to the inconsistency. To circumvent this drawback, we assessed the effect of major ginsenoside-Rg1 (Rg1) on skeletal muscle antioxidant defense system against exhaustive exercise-induced oxidative stress. METHODS: Forty weight-matched rats were evenly divided into control (N = 20) and Rg1 (N = 20) groups. Rg1 was orally administered at the dose of 0.1 mg/kg bodyweight per day for 10- week. After this long-term Rg1 administration, ten rats from each group performed an exhaustive swimming, and remaining rats considered as non-exercise control. Tibialis anterior (TA) muscles were surgically collected immediately after exercise along with nonexercise rats. RESULTS: Exhaustive exercise significantly (p <0.05) increased the lipid peroxidation of control group, evidenced by elevated malondialdehyde (MDA) levels. The increased oxidative stress after exercise was also confirmed by decreased reduced glutathione to oxidized glutathione ratio (GSH/GSSG ratio) in control rats. However, these changes were completely eliminated in Rg1 group. Catalase (CAT) and glutathione peroxidase (GPx) activities were significantly (p <0.05) increased by Rg1 in non-exercise rats, while no significant change after exercise. Nevertheless, glutathione reductase (GR) and glutathione S-transferase (GST) activities were significantly increased after exercise in Rg1 group. CONCLUSIONS: This study provide compelling evidences that Rg1 supplementation can strengthen antioxidant defense system in skeletal muscle and completely attenuate the membrane lipid peroxidation induced by exhaustive exercise. Our findings suggest that Rg1 can use as a nutraceutical supplement to buffer the exhaustive exercise-induced oxidative stress.  相似文献   
18.
In recent years, zinc oxide (ZnO) has become one of the most popular research materials due to its unique properties and various applications. ZnO is an intrinsic semiconductor, with a wide bandgap (3.37 eV) and large exciton binding energy (60 meV) making it suitable for many optical applications. In this experiment, the simple hydrothermal method is used to grow indium-doped ZnO nanostructures on a silicon wafer, which are then annealed at different temperatures (400°C to 1,000°C) in an abundant oxygen atmosphere. This study discusses the surface structure and optical characteristic of ZnO nanomaterials. The structure of the ZnO nanostructures is analyzed by X-ray diffraction, the superficial state by scanning electron microscopy, and the optical measurements which are carried out using the temperature-dependent photoluminescence (PL) spectra. In this study, we discuss the broad peak energy of the yellow-orange emission which shows tendency towards a blueshift with the temperature increase in the PL spectra. This differs from other common semiconductors which have an increase in their peak energy of deep-level emission along with measurement temperature.  相似文献   
19.
ABSTRACT: Thiol group functionalized silica-coated magnetic nanoparticles (Si-MNPs@SH) were synthesized for rapid and selective magnetic field-based separation of mixed proteins. The highest adsorption efficiencies of binary proteins, bovine serum albumin (BSA; 66 kDa; pI = 4.65) and lysozyme (LYZ; 14.3 kDa; pI = 11) were shown at the pH values corresponding to their own pI in the single-component protein. In the mixed protein, however, the adsorption performance of BSA and LYZ by Si-MNPs@SH was governed not only by pH but also by the molecular weight of each protein in the mixed protein.  相似文献   
20.
ABSTRACT: One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.  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