全文获取类型
收费全文 | 8422篇 |
免费 | 184篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 26篇 |
综合类 | 4篇 |
化学工业 | 746篇 |
金属工艺 | 82篇 |
机械仪表 | 54篇 |
建筑科学 | 123篇 |
矿业工程 | 13篇 |
能源动力 | 64篇 |
轻工业 | 280篇 |
水利工程 | 14篇 |
石油天然气 | 7篇 |
武器工业 | 3篇 |
无线电 | 181篇 |
一般工业技术 | 543篇 |
冶金工业 | 6077篇 |
原子能技术 | 10篇 |
自动化技术 | 388篇 |
出版年
2023年 | 27篇 |
2022年 | 60篇 |
2021年 | 95篇 |
2020年 | 66篇 |
2019年 | 71篇 |
2018年 | 80篇 |
2017年 | 88篇 |
2016年 | 112篇 |
2015年 | 92篇 |
2014年 | 108篇 |
2013年 | 200篇 |
2012年 | 168篇 |
2011年 | 146篇 |
2010年 | 158篇 |
2009年 | 118篇 |
2008年 | 136篇 |
2007年 | 126篇 |
2006年 | 97篇 |
2005年 | 75篇 |
2004年 | 63篇 |
2003年 | 58篇 |
2002年 | 48篇 |
2001年 | 37篇 |
2000年 | 45篇 |
1999年 | 205篇 |
1998年 | 1982篇 |
1997年 | 1130篇 |
1996年 | 748篇 |
1995年 | 411篇 |
1994年 | 299篇 |
1993年 | 379篇 |
1992年 | 55篇 |
1991年 | 48篇 |
1990年 | 62篇 |
1989年 | 58篇 |
1988年 | 47篇 |
1987年 | 50篇 |
1986年 | 48篇 |
1985年 | 55篇 |
1984年 | 17篇 |
1983年 | 27篇 |
1982年 | 31篇 |
1981年 | 53篇 |
1980年 | 70篇 |
1978年 | 21篇 |
1977年 | 140篇 |
1976年 | 301篇 |
1975年 | 23篇 |
1974年 | 15篇 |
1973年 | 12篇 |
排序方式: 共有8615条查询结果,搜索用时 31 毫秒
61.
Victor Chabanenko Roman Puźniak Adam Nabiałek Sergei Vasiliev Vladimir Rusakov Loh Huanqian Ritta Szymczak Henryk Szymczak Jan Jun Janusz Karpiński Vitaly Finkel 《Journal of Low Temperature Physics》2003,130(3-4):175-191
We present a study of magneto-thermal instabilities in polycrystalline MgB2 superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated. 相似文献
62.
63.
Cell cycle. The NIMA kinase joins forces with Cdc2 总被引:1,自引:0,他引:1
The NIMA and Cdc2 protein kinases cooperate to regulate mitosis in Aspergillus nidulans. NIMA-related pathways have now begun to emerge in higher eukaryotes. 相似文献
64.
R Albrecht TC Awes C Baktash P Beckmann F Berger R Bock G Claesson G Clewing L Dragon A Eklund RL Ferguson A Franz S Garpman R Glasow HA Gustafsson HH Gutbrod J Idh P Jacobs K Kampert BW Kolb P Kristiansson IY Lee H Loehner I Lund FE Obenshain A Oskarsson I Otterlund T Peitzmann S Persson F Plasil AM Poskanzer M Purschke H Ritter S Saini R Santo HR Schmidt T Siemiarczuk SP Sorensen E Stenlund ML Tincknell GR Young 《Canadian Metallurgical Quarterly》1991,44(6):2736-2752
65.
66.
The aim of this randomized cross-over trial was to evaluate the dose effect and systemic absorption of epinephrine nebulized at 2 and 5 mg in comparison with salbutamol (5 mg). Thirteen asthmatic patients (29 +/- 15 years, 4 men and 9 women) were randomly assigned to receive one nebulization of each of the three treatment regimens at 24 h interval. The evaluation concerned forced expiratory volume in 1 second (FEV1), heart rate, respiratory rate and arterial pressure. All measurements were done at baseline, every 15 minutes during the first hour, and hourly thereafter until return to baseline FEV1. Serum potassium was measured at baseline (T0) and sixty minutes after (T60). Plasma levels of epinephrine were measured at T0, T20, T60. Fifteen minutes after the beginning of nebulization FEV1 improved significantly over baseline in the three groups. These changes were similar in the three groups until T45, while FEV1 improvement was significantly greater in A5 and S groups than A2 group (+640 +/- 470 ml, +721 +/- 349 ml, +406 +/- 306 ml in A5, S and A2 groups respectively, p < 0.01). Bronchodilation lasted significantly longer with salbutamol than with epinephrine (p < 0.05). No side effects were recorded in spite of substantial and dose-dependent systemic absorption of epinephrine. CONCLUSION: Increasing epinephrine doses produces greater bronchodilation without additional side effects. However this bronchodilation lasts shorter than with salbutamol. 相似文献
67.
KS Ghenghesh AS Altomi A Elgrari MR Alosta Omar AM Sharif Eddin SS Abied 《Canadian Metallurgical Quarterly》1995,72(1-2):13-15
Twenty seven Aeromonas strains (5A. hydrophila, 8A. sobria and 14A. caviae) isolated from children with diarrhoea and 34 Aeromonas strains (9A. hydrophila, 7A. sobria an 18A. caviae) isolated from children without diarrhoea were tested from haemolysin production. The results obtained showed that haemolysin production using human, horse or sheep erythrocytes was significantly associated with A.hydrophila and A sobria but not with A.caviae, regardless of whether these strains were isolated from children with or without diarrhoea. Human or horse rather than sheep erythrocytes are recommended for use in the haemolysin assay. 相似文献
68.
FM Scott AM Treston GL Shaw I Avis J Sorenson K Kelly EC Dempsey AB Cantor M Tockman JL Mulshine 《Canadian Metallurgical Quarterly》1996,14(2-3):239-251
Monitoring respiratory epithelial biology may reveal individuals with incipient lung cancer. The expression of neuroendocrine (NE) markers in pulmonary epithelium is thought to be central to lung development, repair of injury and may contribute to carcinogenesis. In this study, we evaluate several candidate NE markers to determine the feasibility of prospective analysis of clinical specimens. The potential NE markers include the enzyme L-DOPA decarboxylase (DDC), the neuropeptide gastrin releasing peptide (GRP), and peptidyl-glycine alpha-amidating monooxygenase (PAM), the bifunctional enzyme responsible for the final bioactivation step of many neuropeptides. A comparison of PAM activity and DDC levels in 30 lung cancer cell lines indicated that peptide amidating activity may be an indicator of NE status. Bronchoalveolar lavage (BAL) fluid from subjects at risk of developing second primary lung cancer and from volunteers was obtained. The activity of the first PAM enzyme, peptidylglycine alpha-hydroxylating monooxygenase (PHM), ranged from not detectable to 507 pmol/h/mg protein in 57 specimens. The second PAM enzyme, peptidylamidoglycolate lyase (PAL), ranged from not detectable to 414 pmol/h/mg protein in 56 specimens. Using cluster analysis by the average linkage method, a group of enzyme values with PHM greater than 230 pmol/h/mg protein was determined. Long-term follow-up of these patients for new second primary lung cancers may help to determine the potential predictive value of PAM detected in the BAL fluid. 相似文献
69.
To determine if hormone supplementation reduces the risk of failure for osseointegration of dental implants in postmenopausal women, the treatment outcomes of 116 women older than age 50, treated with 450 endosseous dental implants, were analyzed in this retrospective study. The findings indicated that hormone replacement therapy may not be linked with improved outcomes of endosseous dental implant treatment in postmenopausal women. Smoking, however, appears to significantly increase the implant failure rate in the group observed in this study. 相似文献
70.