全文获取类型
收费全文 | 2732篇 |
免费 | 67篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 27篇 |
化学工业 | 441篇 |
金属工艺 | 45篇 |
机械仪表 | 35篇 |
建筑科学 | 96篇 |
矿业工程 | 21篇 |
能源动力 | 110篇 |
轻工业 | 328篇 |
水利工程 | 19篇 |
石油天然气 | 9篇 |
无线电 | 259篇 |
一般工业技术 | 358篇 |
冶金工业 | 748篇 |
原子能技术 | 22篇 |
自动化技术 | 284篇 |
出版年
2022年 | 15篇 |
2021年 | 36篇 |
2020年 | 14篇 |
2019年 | 23篇 |
2018年 | 41篇 |
2017年 | 28篇 |
2016年 | 38篇 |
2015年 | 41篇 |
2014年 | 68篇 |
2013年 | 119篇 |
2012年 | 100篇 |
2011年 | 122篇 |
2010年 | 82篇 |
2009年 | 87篇 |
2008年 | 126篇 |
2007年 | 108篇 |
2006年 | 89篇 |
2005年 | 91篇 |
2004年 | 69篇 |
2003年 | 67篇 |
2002年 | 53篇 |
2001年 | 71篇 |
2000年 | 43篇 |
1999年 | 58篇 |
1998年 | 220篇 |
1997年 | 142篇 |
1996年 | 92篇 |
1995年 | 66篇 |
1994年 | 47篇 |
1993年 | 64篇 |
1992年 | 42篇 |
1991年 | 32篇 |
1990年 | 34篇 |
1989年 | 38篇 |
1988年 | 26篇 |
1987年 | 24篇 |
1986年 | 29篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 27篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 19篇 |
1978年 | 17篇 |
1977年 | 21篇 |
1976年 | 57篇 |
1975年 | 12篇 |
1973年 | 17篇 |
1972年 | 12篇 |
1969年 | 12篇 |
排序方式: 共有2802条查询结果,搜索用时 15 毫秒
991.
AT Jensen A Gaafar A Ismail CB Christensen M Kemp AM Hassan A Kharazmi TG Theander 《Canadian Metallurgical Quarterly》1996,55(5):490-495
An enzyme-linked immunosorbent assay (ELISA) using a 28 amino acid sequence of the repetitive element of gene B protein (GBP) from Leishmania major was developed for serodiagnosis of cutaneous leishmaniasis (CL). The assay was compared to ELISAs using crude amastigote and promastigote antigens from L. donovani and the major surface glycoprotein (Gp63) from either L. donovani or L. major as a solid-phase ligand. The sensitivity of the assays was tested in 33 patients suffering from CL caused by L. major. The sensitivity of the GBP peptide (GBPP) ELISA was 82%. This was higher than in the assays using crude amastigote (67%) or promastigote (67%) antigens, but the difference was not statistically significant. The sensitivity in the assays using Gp63 from L. donovani (52%) or L. major (39%) was significantly lower than in the assay using GBPP (P = 0.019 and P < 0.001, respectively). Plasma samples from healthy Sudanese individuals living in an area endemic for malaria but free of leish-maniasis were negative in all the assays. Significantly higher levels of antibodies were found in the patients who had suffered from the disease for more than eight weeks than in patients with a shorter clinical history (GBPP ELISA; P = 0.038; amastigote ELISA; P = 0.004; and promastigote ELISA; P = 0.017). In the former group, the sensitivities of the five ELISAs were 100% (GBPP), 87% (amastigote), 93% (promastigote), 67% (L. donovani), and 53% (L. major), respectively. 相似文献
992.
J Maguire T Santoro P Jensen U Siebenlist J Yewdell K Kelly 《Canadian Metallurgical Quarterly》1994,265(5169):241-244
A gene encoding a 35-kilodalton guanosine triphosphate (GTP)-binding protein, Gem, was cloned from mitogen-induced human peripheral blood T cells. Gem and Rad, the product of a gene overexpressed in skeletal muscle in individuals with Type II diabetes, constitute a new family of Ras-related GTP-binding proteins. The distinct structural features of this family include the G3 GTP-binding motif, extensive amino- and carboxyl-terminal extensions beyond the Ras-related domain, and a motif that determines membrane association. Gem was transiently expressed in human peripheral blood T cells in response to mitogenic stimulation; the protein was phosphorylated on tyrosine residues and localized to the cytosolic face of the plasma membrane. Deregulated Gem expression prevented proliferation of normal and transformed 3T3 cells. These results suggest that Gem is a regulatory protein, possibly participating in receptor-mediated signal transduction at the plasma membrane. 相似文献
993.
JS Jensen B Feldt-Rasmussen K Borch-Johnsen P Clausen M Appleyard G Jensen 《Canadian Metallurgical Quarterly》1997,11(11):727-732
Microalbuminuria has been proposed as a potential atherosclerotic risk factor in hypertensive individuals. The aim of this cross-sectional population study was to analyse whether microalbuminuria is related to a higher prevalence of cardiovascular disease, and a more atherogenic risk profile, and reversely related to the use of antihypertensive drugs. In a major health screening at the State University Hospital in Copenhagen, including urinary albumin excretion, glomerular filtration rate, blood pressure (BP), electrocardiogram, body mass index, plasma lipoproteins, fibrinogen, and albumin, and information regarding a history of acute myocardial infarction, smoking, and antihypertensive drugs, 1254 participants without diabetes mellitus or renal/urinary tract disease had arterial hypertension. Age range was 30-70 years. Microalbuminuria (nocturnal urinary albumin excretion >15 microg/min) occurred in 5%, and cardiovascular disease (previous acute myocardial infarction or electrocardiographic Q-waves) also in 5% of the study population. Microalbuminuric hypertensive subjects were characterized by higher age and systolic BP, and a male predominance, as compared to normoalbuminuric hypertensive subjects. The frequency of cardiovascular disease was similar in the two groups. In contrast, when analysed as a continuous variable, a one unit increase in the logarithmically transformed urinary albumin excretion significantly increased the likelihood of cardiovascular disease (odds ratio [95% confidence interval] 1.32 (1.02-1.70); P < 0.05), and this relation was independent of age, sex, and conventional atherosclerotic risk factors. Participants who were effectively treated with antihypertensive drugs did not have a lower urinary albumin excretion than insufficiently treated or untreated participants. It is concluded that slightly elevated albumin excretion in the urine is not only a pressure-dependent functional phenomenon in the glomerular vessel walls, but associated with permanent atherosclerotic abnormalities in the entire vascular system. 相似文献
994.
The aim of this study was to estimate the risk of being hospitalized due to prolapsed cervical interverteral disc among male professional drivers in Denmark. A cohort consisting of all economically active persons in Denmark, identified January 1981, gives information on the most important occupation during 1980. The cohort was followed for ten years. Additional data on occupational exposures were extracted from a national survey. Occupational groups such as bus and taxi-cab drivers were found to have an increased risk, of cervical prolapse as did the group of professional drivers as a whole. 相似文献
995.
996.
Prof. Preben W. Jensen 《Forschung im Ingenieurwesen》1992,58(6):152-163
The Polode Synthesis method makes use of inversion letting the end point of the coupler of a dyad move on the desired curve
keeping the other end joint fixed. The resultant moving centrode and moving polodes yield information about where solutions
can be found. The method can be applied towards path generation, timed path generation, function generation, motion generation
and timed motion generation. If neither the corresponding centrode nor the polodes intersect then, in general, the resultant
coupler curve has only 4 points common with the desired curve. If the polodes intersect then 6-point solutions are obtained
etc. The method is applied to straight line mechanisms where the coupler curve is to deviate little from the straight line
over the entire range. The same kind of curve is generated so that certain crank positions correspond to certain positions
of the coupler point. The method is then applied to a circular arc. The generation of an approximate ellipse is shown for
illustrative purposes and the resultant curve is almost identical to the ellipse. The new method approximates the entire curve
rather than selecting a few precision points through which the resultant coupler curve is intended to pass. However, only
part of the desired curve may be prescribed. The method can be applied to any combination of links and joints. 相似文献
997.
The carrier concentration in heterostructure FETs (HFETs) with a p-i-p+ buffer is presented as a function of the gate bias, obtained by self-consistent one-dimensional calculation of 2-D electron density, subband levels, and electrostatic potential. These results quantify certain limitations on the range of geometrical and doping parameters and make it possible to optimize the HFET design and to compare modulation doped FET (MODFET) and doped channel HFET (DCHFET) structures. Monte Carlo simulations demonstrate that this p-i-p+ buffer drastically reduces the short-channel effects 相似文献
998.
Methods and preliminary results on enhanced boiling heat transfer in second generation microchannels
Michael K. Jensen Yoav Peles Ali Koşar Chih-Jung Kuo 《Microfluidics and nanofluidics》2006,2(5):387-397
This paper reviews literature on conventional scale boiling enhancement techniques by means of reentrant cavities and discusses various avenues the knowledge obtained from that research can be used to enhance boiling in microchannels. Fabrication techniques developed by the Micro Thermal-Fluids Laboratory at Rensselaer Polytechnic Institute together with the Advanced Microsystems Materials Laboratory at McGill University are discussed and preliminary data are given. These results demonstrate the potential for improving boiling heat transfer characteristics in microchannels and introduce next generation microchannel heat transfer technology. 相似文献
999.
A technique of epidural catheterization in rabbits is described. Twelve albino rabbits received a totally implanted epidural catheter system. The system was implanted surgically, and the functioning of the system tested for a period of 3 months. X-ray examinations following epidural contrast injections showed a distribution up to Th4 following 1.5 ml and Th8-9 following 1.0 and 1.25 ml. Epidural injection of lidocaine throughout the study period proved the system to be functioning for all 3 months. Another 12 rabbits were included for the neurotoxicological examinations following epidural catheterization, without any injections (three rabbits), epidural injections of saline (four rabbits) and meptazinol (five rabbits) once a day for 14 days. Histopathological examinations showed a fibrous cocoon, at the tip of the catheter, in all rabbits. In the group of rabbits which did not receive any injections, the cocoon was slightly infiltrated with leukocytes and local depression of the spinal cord was observed in one rabbit. In the saline-injected group this infiltration was more pronounced and in one rabbit it extended into the meninges. Three rabbits showed local depression of the spinal cord and local myelopathy of the white matter in the area adjacent to the cocoon. In the group of rabbits receiving meptazinol, three out of five had local depression and myelopathy of the white matter. In this group these findings were more pronounced. In two rabbits the myelopathy extended transversely through the white matter into the grey matter of the spinal cord. The number of pathological changes in the group receiving meptazinol was significantly higher compared to the control and placebo groups.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
1000.
Unlike the bulk of electronic media the computer game or video game is a distinctly gendered medium. All investigations confirm that we are dealing with a medium which almost exclusively appeals to and is used by, boys and young men. Therefore, the video games and computer games are very suited for investigating the form of entertainment, the pleasure, that appeals to men, i.e. the specific ‘masculine pleasure’. The paper deals with questions such as: What do computer games mean? What does violence in computer games signify? Why do computer games, especially the violent ones, mean something special to a certain group of men? These questions are discussed from the perspective of semiotics, media and control studies. Finally, the paper discusses the connections between women and the male dominated video games, and attempts to explain why, nevertheless, some girls and women do play these games. 相似文献