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   3494篇
  免费   46篇
  国内免费   14篇
电工技术   54篇
综合类   30篇
化学工业   116篇
金属工艺   20篇
机械仪表   105篇
建筑科学   35篇
矿业工程   6篇
能源动力   55篇
轻工业   367篇
水利工程   16篇
无线电   44篇
一般工业技术   141篇
冶金工业   2418篇
原子能技术   9篇
自动化技术   138篇
  2022年   23篇
  2020年   21篇
  2019年   33篇
  2018年   8篇
  2017年   7篇
  2016年   12篇
  2015年   6篇
  2014年   14篇
  2013年   167篇
  2012年   42篇
  2011年   43篇
  2010年   38篇
  2009年   42篇
  2008年   49篇
  2007年   58篇
  2006年   37篇
  2005年   44篇
  2004年   40篇
  2003年   32篇
  2002年   22篇
  2001年   11篇
  2000年   17篇
  1999年   90篇
  1998年   785篇
  1997年   456篇
  1996年   299篇
  1995年   161篇
  1994年   132篇
  1993年   156篇
  1992年   28篇
  1991年   32篇
  1990年   49篇
  1989年   43篇
  1988年   43篇
  1987年   55篇
  1986年   42篇
  1985年   39篇
  1984年   12篇
  1983年   10篇
  1982年   18篇
  1981年   23篇
  1980年   21篇
  1979年   8篇
  1977年   64篇
  1976年   127篇
  1975年   7篇
  1969年   5篇
  1958年   5篇
  1955年   18篇
  1954年   16篇
排序方式: 共有3554条查询结果,搜索用时 15 毫秒
41.
Cookies enriched with 0, 5, 10, 15, 20, and 25% full-fat sweet lupine flour (FFSL) were evaluated by a sensory panel using the rank of preference and paired comparison tests. Cookies with 0, 5, and 10% FFSL were preferred while those containing 20 and 25% FFSL were rejected (p≤0.01). Studies conducted with school children showed similar acceptability for 0 and 10% FFSL-containing cookies which was different (p = 0.05) from those containing 20% FFSL. Fortification of the basic formula with 10% FFSL was recommended on the basis of acceptability.  相似文献   
42.
43.
Burkholderia pseudomallei is the causative agent of melioidosis, a disease increasingly recognized as an important cause of morbidity and mortality in many regions of the world. B. pseudomallei is a facultative intracellular pathogen capable of invading eukaryotic cells. We used Tn5-OT182 mutagenesis to generate mutants deficient in the ability to invade a human type II pneumocyte cell line (A549 cells). One of these mutants, AJ1D8, exhibited approximately 10% of the ability of the parental strain, 1026b, to invade A549 cells. There was no difference in the abilities of 1026b and AJ1D8 to resist killing by RAW macrophages or the human defensin HNP-1. The nucleotide sequence flanking the Tn5-OT182 integration in AJ1D8 was determined, and two open reading frames were identified. The predicted proteins shared considerable homology with two-component regulatory systems involved in the regulation of heavy-metal resistance in other organisms. AJ1D8 was 16-fold more sensitive to Cd2+ and twofold more sensitive to Zn2+ than was 1026b but was not sensitive to any of the other heavy metals examined. The B. pseudomallei two-component regulatory system, termed irlRS, complemented the invasion-deficient and heavy-metal-sensitive phenotype of AJ1D8 in trans. There was no significant difference between the virulence of AJ1D8 and that of 1026b in infant diabetic rats and Syrian hamsters, suggesting that the irlRS locus is probably not a virulence determinant in these animal models of acute B. pseudomallei infection.  相似文献   
44.
45.
46.
47.
介绍了卷烟信息网络防伪管理系统构建原理、技术特点和功能 ,及其在烟草行业中的应用。  相似文献   
48.
Symptom-limited, graded exercise treadmill testing was performed by 4,968 white and black adults, ages 18-30 yr, during the baseline examination for the Coronary Artery Risk Development in Young Adults (CARDIA) study. Compared with nonsmokers, the mean exercise test duration of smokers was 29-64 s shorter depending on race/gender group (all P < 0.001), but mean duration to heart rate 130 (beats.min-1) ranged from 20-50 s longer (P < 0.05). In each race/gender group, test duration to heart rates up to 150 was 15-35 s longer (P < 0.05) in smokers than in nonsmokers after adjustment for age, sum of skinfolds, hemoglobin, and physical activity score. The mean maximum heart rate was lower in smokers than in nonsmokers (difference ranging from 6.7 beats.min-1 in white men to 11.2 beats.min-1 lower in black women, P < 0.001), although maximum rating of perceived exertion was nearly identical in smokers and nonsmokers. Chronic smoking appears to blunt the heart rate response to exercise, so that exercise duration to submaximal heart rates is increased even though maximal performance is impaired. This may result from downloading of beta-receptors caused by smoking. Smoking status should be considered in the evaluation of physical fitness data utilizing submaximal test protocols, or else the fitness of smokers relative to nonsmokers is likely to be overestimated.  相似文献   
49.
This case report details the multidisciplinary treatment of peripartum left iliac vein thrombosis using percutaneous catheter-directed urokinase thrombolysis and balloon thromboplasty. Enhanced chances for long-term patency and the normalization of venous function make these minimally invasive procedures accepted options for the treatment of iliofemoral deep venous thrombosis in selected peripartum patients.  相似文献   
50.
The preparation and characteristics of compound-specific and group-specific antibodies against 7-alkylguanines (7-alkGua) are described. A compound-specific antibody against 7-methylguanine was prepared using a hapten bound to carrier protein through the N2 position. In a competitive enzyme-linked immunosorbent assay (ELISA) 7-methylguanine (7-MeGua) showed 50% inhibition (I50%) at 10 pmol/well at room temperature, but the inhibition was found to be 40 times better at 4 degrees C (I50% at 250 fmol/well). When the antibody was bound to protein A-Sepharose CL4B 7-MeGua was retained in immunoaffinity columns. A group-specific antibody to 7-alkGua was prepared using 7-(2-carboxyethyl)guanine (7-CEGua) bound to carrier protein via the carboxyl group. In a competitive ELISA, this antibody cross-reacted well with 7-CEGua, 7-ethylguanine (7-EtGua), 7-(2-hydroxyethyl)guanine (7-HOEtGua) and 7-(2',3'-dihydroxy)-propylguanine (7-DHPGua) and some inhibition was seen with 7-MeGua. Immunoaffinity columns prepared from this antibody retained a number of 7-alkGua of diverse structure. 7-EtGua in calf thymus DNA treated with diethylsulphate and ethylnitrosourea was isolated by immunoaffinity purification and quantified by HPLC-fluorescence. These results illustrate the potential of immunoaffinity purification for both individual DNA adducts and groups of adducts.  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