全文获取类型
收费全文 | 4422篇 |
免费 | 23篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 45篇 |
综合类 | 3篇 |
化学工业 | 422篇 |
金属工艺 | 82篇 |
机械仪表 | 168篇 |
建筑科学 | 57篇 |
矿业工程 | 3篇 |
能源动力 | 117篇 |
轻工业 | 90篇 |
水利工程 | 27篇 |
石油天然气 | 9篇 |
无线电 | 517篇 |
一般工业技术 | 493篇 |
冶金工业 | 1860篇 |
原子能技术 | 20篇 |
自动化技术 | 537篇 |
出版年
2024年 | 25篇 |
2023年 | 34篇 |
2022年 | 59篇 |
2021年 | 64篇 |
2020年 | 58篇 |
2019年 | 60篇 |
2018年 | 66篇 |
2017年 | 57篇 |
2016年 | 81篇 |
2015年 | 54篇 |
2014年 | 65篇 |
2013年 | 171篇 |
2012年 | 88篇 |
2011年 | 130篇 |
2010年 | 107篇 |
2009年 | 99篇 |
2008年 | 102篇 |
2007年 | 96篇 |
2006年 | 90篇 |
2005年 | 81篇 |
2004年 | 59篇 |
2003年 | 61篇 |
2002年 | 67篇 |
2001年 | 57篇 |
2000年 | 63篇 |
1999年 | 107篇 |
1998年 | 632篇 |
1997年 | 344篇 |
1996年 | 255篇 |
1995年 | 139篇 |
1994年 | 125篇 |
1993年 | 155篇 |
1992年 | 60篇 |
1991年 | 54篇 |
1990年 | 54篇 |
1989年 | 52篇 |
1988年 | 48篇 |
1987年 | 40篇 |
1986年 | 40篇 |
1985年 | 46篇 |
1984年 | 23篇 |
1983年 | 34篇 |
1982年 | 36篇 |
1981年 | 38篇 |
1980年 | 36篇 |
1979年 | 34篇 |
1978年 | 17篇 |
1977年 | 53篇 |
1976年 | 74篇 |
1975年 | 14篇 |
排序方式: 共有4450条查询结果,搜索用时 0 毫秒
901.
A review of studies made in the compost production industry showed the biological agents posing a risk for workers were fungi and thermophile bacteria, gram-negative bacteria and endotoxins, with a prevalent inhalation exposure to airborne contaminated dusts. Medical examinations revealed cases of extrinsic allergic alveolitis due to A. fumigatus, and more frequently irritative and infectious disorders occurring especially in conditions of poor environmental hygiene and macroscopic dust pollution. For the evaluation of the air dispersion of microorganisms, which is high in compost transport and turning operations, at present no exposure limit values are available for biological agents; nevertheless, the concentrations measured were often higher than the limit values proposed for other manufacturing sectors by individual authors and by regulatory agencies in Europe, and were comparable to values observed in other industrial settings for which adverse health effects have been shown. Although the number of studies available are few in number, the results suggest that the hazards posed by microorganisms and the poor environmental hygiene conditions often encountered can undoubtedly be a source of risk for workers, which at present is difficult to establish but significant considering the high airborne concentrations of contaminated dust. Besides technical measures to avoid environmental macroscopic dispersion of dusts, measurement of airborne microbiological contaminants is also recommended. Health surveillance needs to be aimed at identifying subjects with hypersusceptibility to the infectious action of the pathogenetic and/or allergenic agents or with hypersensitivity to the same, and also to periodic control of respiratory organs. 相似文献
902.
903.
904.
MK Popkin AL Callies EA Colón RD Lentz DE Sutherland 《Canadian Metallurgical Quarterly》1993,34(3):251-258
To examine the role of psychiatric diagnosis in the surgical outcome of pancreas transplantation, we studied candidates with type I diabetes mellitus. Eighty of 140 candidates underwent transplantation. Survival analysis found the extent of human leukocyte antigen-DR (HLA-DR) matching, two diagnoses, and patients' perceived support from first-degree relatives to be related to duration of full-graft function. Lifetime diagnoses of tobacco use disorder (P = 0.029) and alcohol abuse/dependence (P = 0.006) were associated with less favorable outcomes; perceived support was associated with positive outcomes (P = 0.048). Subsequent analysis suggested that the four variables independently and directly affect outcome. 相似文献
905.
Hemant K. Jain 《Information & Management》1985,9(5):269-281
This paper presents an overview of an interactive system for the design of a distributed computer system. The system helps the designer in finding the optimal combination of processors of varying power to be located at various nodes of the system. It also helps in finding the optimal allocation of data files or databases. The system allows the designer to trade-off between the conflicting objectives: low investment and operating cost and high availability of data. Reasonable relative weights are assigned to each data file, and design objectives can be assigned priorities. A value added network such as TELENET is assumed for data communication. Also, multiple copies of the data file or database may exist in the system to achieve higher data availability and better response time. 相似文献
906.
We evaluated the respiratory effects of intravenous morphine infusions in 30 patients (2 to 570 days old, mean 155 days) after cardiac surgery. PaCO2 during spontaneous breathing and CO2 response curves during rebreathing were obtained on morphine infusions at drug steady state and during drug washout. Steady state morphine serum levels > 20 ng/mL resulted in hypercarbia (PaCO2 > 55 mm Hg) and depressed CO2 response curve slopes (< 10 mL.min-1.mm Hg ETCO2(-1).kg-1) in 67% and 70% of patients, respectively (P < 0.05, compared to those with levels < 20 ng/mL). During washout, morphine levels more than 15 ng/mL resulted in hypercarbia in 46%, whereas levels less than 15 ng/mL were associated with hypercarbia in 13% (P = 0.025). No age-related differences in respiratory effect were seen in these studies at the same serum morphine level. Careful observation of any patient receiving morphine remains necessary, but neonates and young infants seem to have the same respiratory response to morphine infusions as older infants and children at the same blood level. 相似文献
907.
A new keratinophilic species, Chrysosporium gourii, an isolate of cattle farm soil of Sagar, India, is described and illustrated. The differences between this and other similar keratinophilic species of Chrysosporium are discussed. 相似文献
908.
909.
AB Mason MK Miller WD Funk DK Banfield KJ Savage RW Oliver BN Green RT MacGillivray RC Woodworth 《Canadian Metallurgical Quarterly》1993,32(20):5472-5479
The coding sequence for human serum transferrin was assembled from restriction fragments derived from a full-length cDNA clone isolated from a human liver cDNA library. The assembled clone was inserted into the expression vector pNUT and stably transfected into transformed baby hamster kidney (BHK) cells, leading to secretion of up to 125 mg/L recombinant protein into the tissue culture medium. As judged by mobility on NaDodSO4-PAGE, immunoreactivity, spectral properties (indicative of correct folding and iron binding), and the ability to bind to receptors on a human cell line, initial studies showed that the recombinant transferrin, is identical to three commercial human serum transferrin samples. Electrospray mass spectrometry (ESMS), anion-exchange chromatography, and urea gel analysis showed that the recombinant protein has an extremely complex carbohydrate pattern with 16 separate masses ranging from 78,833 to 80,802 daltons. Mutation of the two asparagine carbohydrate linkage sites to aspartic acid residues led to the expression and secretion of up to 25 mg/L nonglycosylated transferrin. ESMS, anion-exchange chromatography, and urea gel analysis showed a single molecular species that was consistent with the expected theoretical mass of 75,143 daltons. In equilibrium binding experiments, the nonglycosylated mutant bound to HeLa S3 cells with the same avidity and to the same extent as the glycosylated protein and the three commercial samples. These studies demonstrate conclusively that carbohydrate has no role in this function. 相似文献
910.
A tunable sandwich transducer is reported which has its fundamental resonant frequency controlled by varying a passive reactive load. The structure consists of four PZT-4 rings sandwiched between an aluminium head-mass and a brass tail-mass. The electromechanical coupling coefficient and the radiation efficiency into water of the transducer are given over the frequency range 25 to 75 kHz. A theoretical analysis based on an electromechanical equivalent circuit shows good agreement with the experimental results 相似文献