全文获取类型
收费全文 | 4275篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 11篇 |
综合类 | 3篇 |
化学工业 | 58篇 |
金属工艺 | 3篇 |
机械仪表 | 5篇 |
建筑科学 | 15篇 |
能源动力 | 15篇 |
轻工业 | 58篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 29篇 |
一般工业技术 | 122篇 |
冶金工业 | 3928篇 |
原子能技术 | 6篇 |
自动化技术 | 36篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 14篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 10篇 |
2013年 | 14篇 |
2012年 | 17篇 |
2011年 | 25篇 |
2010年 | 27篇 |
2009年 | 17篇 |
2008年 | 29篇 |
2007年 | 19篇 |
2006年 | 26篇 |
2005年 | 10篇 |
2004年 | 19篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 143篇 |
1998年 | 1246篇 |
1997年 | 694篇 |
1996年 | 434篇 |
1995年 | 229篇 |
1994年 | 200篇 |
1993年 | 256篇 |
1992年 | 31篇 |
1991年 | 53篇 |
1990年 | 52篇 |
1989年 | 65篇 |
1988年 | 67篇 |
1987年 | 56篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1983年 | 9篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 99篇 |
1976年 | 208篇 |
1975年 | 10篇 |
1974年 | 1篇 |
1967年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有4296条查询结果,搜索用时 31 毫秒
101.
JS Sheffield DM Twickler C Timmons K Land MJ Harrod RM Ramus 《Canadian Metallurgical Quarterly》1998,17(9):585-589
From 1988 to 1995, 96 patients (161 feet) underwent a modified Mitchell distal metatarsal osteotomy performed for mild-to-moderate hallux valgus. On AP x-rays of the standing foot, the average intermetatarsal angle was corrected from 15 degrees to 9 degrees, and the first metatarsophalangeal angles were corrected from an average of 41 degrees to 15 degrees. Criteria for evaluation of clinical results included relief of pain, appearance of foot, and shoe wear. After an average follow-up of 38 months, the overall satisfaction rate was 92.5%. Complications included 13 pin tract infections, two delayed unions, and two correction losses. The most common late sequela was transfer metatarsalgia of the lesser toes, which occurred in 20 feet (12.4%), leading to some dissatisfaction. The Mitchell osteotomy can be used on cases with less than 20 degrees of intermetatarsal angle, offering a stable construct with easy postoperative care. 相似文献
102.
KL Margolis N Lurie PG McGovern M Tyrrell JS Slater 《Canadian Metallurgical Quarterly》1998,13(8):515-521
Active cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS) was treated with an intraocular sustained-release ganciclovir implant. A total number of 19 implants were performed in 15 eyes of 9 AIDS patients. The intraocular sustained-release ganciclovir was effective in preventing reactivation of CMV retinitis in 15 of the 19 implants, ineffective in 3, and undetermined in 1. All ineffective cases had been resistant to ganciclovir therapy before the implants. Vision after the therapy was maintained at better than 0.5 except for one eye. There were no serious ocular complications caused by the therapy. Among 5 patients with unilateral CMV retinitis, 2 unaffected eyes developed CMV retinitis during this therapy. In addition, another patient developed presumed CMV infection in other systemic organs. Based on these data, the intraocular sustained-release ganciclovir implant was considered to be useful for the treatment of CMV retinitis in AIDS. 相似文献
103.
FM-FM neurons in the auditory cortex of the mustached bat are highly specialized for echolocation, responding facilitatively to the combination of frequency modulated (FM) components of biosonar pulse and its echo. Here we propose they are also specialized for processing bat communication calls. FM-FM neurons respond facilitatively to natural call syllable pairs, and exhibit inter-syllable interval tuning to the natural range of intervals. Our results support a role for 'combination-sensitive' neurons in communication, and suggest that cortical neurons can possess multiple distinct specialized modes of response. 相似文献
104.
M Tristam AS Alaamer JS Fleming VJ Lewington MA Zivanovic 《Canadian Metallurgical Quarterly》1996,37(6):1058-1063
In the treatment of neural crest tumors, such as pheochromocytoma, with[131I]MIBG, bone marrow toxicity limits the amount of administered activity and, thus, a therapeutically useful tumor dose. METHODS: We calculated tumor doses in a series of diagnostic studies with [123I]MIBG using accurate quantification of SPECT and planar scintigraphy. By extrapolating diagnostic results to therapeutic activities of [131I]MIBG, we could compare the results with whole-body doses from a series of therapies. RESULTS: The tumor dose was DT = 2.2 mGy MBq(-1) (median value of 27 measurements, range 0.04 < or = DT < or = 20 mGy MBq(-1) and the whole-body dose in a series of 16 patients undergoing 50 therapies was DWB = 0.12 +/- 0.04 mGy MBq(-1) (mean +/- s.d.). The therapeutic ratio varied between 130 to below 10 in some patients. CONCLUSION: The results were compared with published data. We found clearly skewed distribution of tumor doses, with a majority of tumors receiving only a few mGy per MBq administered activity. In some patients, however, doses did reach 20 mGy MBq(-1). 相似文献
105.
The antifibrotic effect of the mismatched double-stranded RNA, Ampligen (poly(I).poly(C12U)), was evaluated in a bleomycin-mouse model of pulmonary fibrosis. Mice received a single intratracheal dose of bleomycin (0.125 U/mouse) or saline (50 microL) at the beginning of the experiment, followed by 5 or 6 intraperitoneal injections of Ampligen (1.0, 5.0, 10.0, 15.0, or 25.0 mg/kg) or saline at regular intervals for 2 weeks. Ampligen did not produce increased mortality or weight loss by itself. However, it produced varying degrees of mortality in combination with bleomycin. Five injections of 10 mg/kg Ampligen or three injections of 25 mg/kg Ampligen plus three injections of 10 mg/kg Ampligen in combination with bleomycin .produced significant reductions in lung collagen accumulation as indicated by lung hydroxyproline content compared to the bleomycin control group. Animals receiving bleomycin plus Ampligen at all dosages had significantly reduced prolyl hydroxylase activity compared to the bleomycin control group. Lipid peroxidation and bronchoalveolar lavage fluid (BALF)-supernatant protein content for the groups receiving bleomycin plus Ampligen were not reduced compared to the bleomycin control group. In the BALF-supernatant, the activity of acid phosphatase, a lysosomal enzyme produced by neutrophils, monocytes, and macrophages, was significantly decreased in the group receiving bleomycin plus 10 mg/kg Ampligen. Also, selected BALF differential immune cell counts were reduced in some of the groups receiving bleomycin plus Ampligen, but not in a consistent or dose-dependent manner. The results of this study indicate that Ampligen can significantly reduce the bleomycin-induced increased collagen accumulation and may be therapeutically useful in the management of lung fibrosis in humans. 相似文献
106.
GP Xue JS Johnson DJ Smyth LM Dierens X Wang GD Simpson KS Gobius JH Aylward 《Canadian Metallurgical Quarterly》1996,45(1-2):120-126
Temperature-regulated expression of recombinant proteins in the tac promoter (Ptac) system was investigated. Expression levels of fungal xylanase and cellulase from N. patriciarum in E. coli strains containing the natural lacI gene under the control of the Ptac markedly increased with increasing cultivation temperature in the absence of a chemical inducer. The specific activities (units per milligram protein of crude enzyme) of the fungal xylanase and cellulase produced from recombinant E. coli strain pop2136 grown at 42 degrees C were about 4.5 times higher than those of the cells grown at 23 degrees C and were even slightly higher when compared with cells grown in the presence of the inducer isopropyl beta-D-thiogalactopyranoside. The xylanase expression level in the temperature-regulated Ptac system was about 35% of total cellular protein. However, this system can not be applied to E. coli strains containing lacIq, which confers over production of the lac repressor, for high-level expression of recombinant proteins. In comparison with the lambda PL system, the Ptac-based xylanase plasmid in E. coli pop2136 gave a considerably higher specific activity of the xylanase than did the best lambda PL-based construct using the same thermal induction procedure. The high-level expression of the xylanase using the temperature-regulated Ptac system was also obtained in 10-litre fermentation studies using a fed-batch process. These results unambiguously demonstrated that the temperature-modulated Ptac system can be used for overproduction of some non-toxic recombinant proteins. 相似文献
107.
D Matecka RB Rothman L Radesca BR de Costa CM Dersch JS Partilla A Pert JR Glowa FH Wojnicki KC Rice 《Canadian Metallurgical Quarterly》1996,39(24):4704-4716
The design, synthesis, and biological evaluation of compounds related to the dopamine (DA) uptake inhibitors: 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine (1) and 1-[2-[bis-(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (2) (GBR 12395 and GBR 12909, respectively), directed toward the development and identification of new ligands interacting with high potency and selectivity at the dopamine transporter (DAT) is reported. The substitution of the piperazine ring in the GBR structure with other diamine moieties resulted in the retention of the high affinity of new ligands for the DAT. Some of the modified GBR analogs (e.g. 8, 10, (-)-49, or (-)-50) displayed substantially higher selectivity (4736- to 693-fold) for the dopamine (DA) versus the serotonin (5HT) reuptake site than the parent compounds. The bis(p-fluoro) substitution in the (diphenylmethoxy)ethyl fragment slightly increased the affinity of the ligands at the DA reuptake site but reduced their selectivity at this site (e.g. 9 and 8, 11 and 10, or 17 and 16, respectively). Congeners, such as the series of monosubstituted and symmetrically disubstituted piperazines and trans-2,5-dimethylpiperazines, which lack the (diphenylmethoxy)ethyl substituent lost the affinity for the DAT yet exhibited very high potency for binding to the sigma receptors (e.g.28). The chiral pyrrolidine derivatives of 1, (-)-49, and (+)-49, exhibited an enantioselectivity ratio of 181 and 146 for the inhibition of DA reuptake and binding to the DAT, respectively. 相似文献
108.
G. Garib C. Vial F. Negroni E. G. Thomsen 《Journal of Materials Shaping Technology》1988,5(3):191-195
A hollow punch-torque method was used to measure friction between tough pitch copper and three different lubricants. The tests indicated that the coefficient μ is not a function of the applied pressure, while the friction factorm is. Both μ andm depend only slightly on the degree of prior deformation. The range of pressure investigated was that encountered in drawing operations and is below that for lubricated sliding surfaces where sublayer plastic flow occurs. 相似文献
109.
The aim of this project was to investigate the potential of reducing number of mixers in the biological treatment process and thereby achieve energy and economical savings and contribute to cleaner environment. The project was carried out at Avedoere wastewater treatment plant and a full scale investigation was conducted to study the effect of reduced mixing on flow velocity, suspended solid sedimentation, concentration gradients of oxygen and SS with depth and treatment efficiency. The only negative effect observed was on flow velocity; however the velocity was above the critical velocity. The plant has been operating with 50% of its designed number of mixers since September 2007 and long term results also confirm that reduced mixing did not have any negative effect on treatment efficiency. The estimated yearly electricity saving is 0.75 GWh/year. 相似文献
110.
A. P. Litvinchuk C. Thomsen M. Cardona L. Börjesson M. Käll P. Berastegui L. -G. Johansson 《Journal of Superconductivity》1994,7(1):113-116
We report a reflectivity study of thez-polarized TO-phonons of Pr
x
Y1–x
Ba2Cu4O8 and YBa2–y
Sr
y
Cu4O8 alloys in the temperature range 10–300 K. Anomalies of the frequency and linewidth of the plane-oxygen vibration at300 cm–1 due to the opening of the superconducting gap are found to occur upon crossing the superconducting transition temperatureT
c
. Phonon self-energy effects are strongly dependent onT
c
, providing evidence for a relative shift of the gap with respect to the energy of phonon.On leave from the Institute for Semiconductor Physics, Ukrainian Academy of Sciences, 252650 Kiev-28, Ukraine. 相似文献