全文获取类型
收费全文 | 8092篇 |
免费 | 94篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 71篇 |
综合类 | 1篇 |
化学工业 | 672篇 |
金属工艺 | 85篇 |
机械仪表 | 96篇 |
建筑科学 | 178篇 |
矿业工程 | 17篇 |
能源动力 | 85篇 |
轻工业 | 522篇 |
水利工程 | 53篇 |
石油天然气 | 17篇 |
无线电 | 607篇 |
一般工业技术 | 751篇 |
冶金工业 | 4329篇 |
原子能技术 | 40篇 |
自动化技术 | 663篇 |
出版年
2021年 | 43篇 |
2020年 | 33篇 |
2019年 | 65篇 |
2018年 | 68篇 |
2017年 | 54篇 |
2016年 | 53篇 |
2015年 | 43篇 |
2014年 | 69篇 |
2013年 | 219篇 |
2012年 | 121篇 |
2011年 | 175篇 |
2010年 | 135篇 |
2009年 | 127篇 |
2008年 | 179篇 |
2007年 | 182篇 |
2006年 | 166篇 |
2005年 | 145篇 |
2004年 | 118篇 |
2003年 | 113篇 |
2002年 | 113篇 |
2001年 | 119篇 |
2000年 | 99篇 |
1999年 | 196篇 |
1998年 | 1202篇 |
1997年 | 714篇 |
1996年 | 484篇 |
1995年 | 353篇 |
1994年 | 285篇 |
1993年 | 325篇 |
1992年 | 113篇 |
1991年 | 89篇 |
1990年 | 127篇 |
1989年 | 125篇 |
1988年 | 105篇 |
1987年 | 90篇 |
1986年 | 88篇 |
1985年 | 100篇 |
1984年 | 77篇 |
1983年 | 65篇 |
1982年 | 63篇 |
1981年 | 65篇 |
1980年 | 79篇 |
1979年 | 63篇 |
1978年 | 63篇 |
1977年 | 153篇 |
1976年 | 335篇 |
1975年 | 54篇 |
1974年 | 38篇 |
1973年 | 37篇 |
1972年 | 36篇 |
排序方式: 共有8187条查询结果,搜索用时 9 毫秒
91.
92.
JM Sorof EP Hawkins ED Brewer II Boydstun AS Kale DR Powell 《Canadian Metallurgical Quarterly》1998,12(9):764-768
In patients with proteinuria, African-American (AA) ethnicity is reported to be a risk factor for focal segmental glomerulosclereosis (FSGS) and its progression to end-stage renal disease (ESRD). We reviewed our single-center experience to determine the probability of FSGS and its progression to ESRD based on ethnicity and age at presentation in children with proteinuria with or without nephrotic syndrome. Proteinuria without systemic disease or acute glomerulonephritis was the presenting feature in 17% (236/1,403) of children in the renal patient database of Texas Children's Hospital, Baylor College of Medicine. Histopathological diagnoses were established in 107 of 236 patients (45%). FSGS was identified in 65 patients, accounting for 28% of all patients with proteinuria and 61% of patients who underwent renal biopsy. FSGS was more prevalent in AA (45%) than in non-AA patients (22%) (P=0.001), and AA patients with FSGS were older at presentation (12.7+/-4.4 years) than non-AA patients (5.6+/-4.6 years) (P<0.001). Among patients who underwent renal biopsy, increasing age at presentation increased the probability of having FSGS in AA but not non-AA patients (P=0.04). Five-year actuarial renal survival of FSGS was worse in AA (8%) than in non-AA patients (31%) (P=0.01). These data suggest an increased risk and worse outcome of FSGS in AA compared with non-AA children. 相似文献
93.
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
94.
95.
96.
AS Stein MR O'Donnell A Chai GM Schmidt A Nademanee PM Parker EP Smith DS Snyder A Molina DE Stepan R Spielberger G Somlo KA Margolin N Vora J Lipsett J Lee J Niland SJ Forman 《Canadian Metallurgical Quarterly》1996,14(8):2206-2216
PURPOSE: To evaluate in a prospective study the efficacy of autologous bone marrow transplantation (BMT) in adult patients with acute myelogenous leukemia (AML) in first remission, using a single course of high-dose Cytarabine (HD Ara-C) consolidation therapy as in vivo purging. PATIENTS AND METHODS: Sixty consecutive adult patients with AML in first complete remission (CR) were treated with HD Ara-C consolidation therapy as a method of in vivo purging before marrow collection. High-dose therapy consisted of fractionated total-body irradiation (FTBI) 12 Gy, intravenous etoposide 60 mg/kg, and cyclophosphamide 75 mg/kg, followed by reinfusion of cryopreserved marrow. RESULTS: Sixty patients underwent consolidation treatment with HD Ara-C with the intent to treat with autologous BMT. Sixteen patients were unable to proceed to autologous BMT (10 patients relapsed, one died of sepsis, one developed cerebellar toxicity, two had inadequate blood counts, and two refused). Forty-four patients underwent autologous BMT and have a median follow-up time of 37 months (range, 14.7 to 68.7) for patients who are alive with no relapse. The cumulative probability of disease-free survival (DFS) at 24 months in the intent-to-treat group is 49% (95% confidence interval [CI], 37% to 62%) and in those who actually underwent autologous BMT is 61% (95% CI, 46% to 74%). The probability of relapse was 44% (95% CI, 31% to 58%) and 33% (95% CI, 20% to 49%) for the intent-to-treat and autologous BMT patients, respectively. CONCLUSION: This approach offers a relatively high DFS rate to adult patients with AML in first CR. The results of this study are similar to those achieved with allogeneic BMT. 相似文献
97.
The present study investigates 1085 previously untreated patients with squamous cell carcinoma of the head and neck for factors that influence recurrence following treatment with definitive radiotherapy. In the second part of this study, those diagnosed with recurrence were studied with regard to treatment and were further analysed with regard to identification of prognostic factors which may affect outcome in the patient who actually develops a recurrence. 相似文献
98.
A simple extension to the staircase FDTD algorithm yielding accurate subcell models of flat metal walls and corners is presented. Electric field nodes on the edges of staircase models of perfect electric conductors are replaced by values obtained using interpolation or analytic continuation into the metal. The algorithm is validated by computing the resonant frequencies of cavities 相似文献
99.
Strength and electrical conductivity of deformation-processed Cu-15 Vol Pct Fe alloys produced by powder metallurgy techniques 总被引:16,自引:0,他引:16
G. A. Jerman I. E. Anderson J. D. Verhoeven 《Metallurgical and Materials Transactions A》1993,24(1):35-42
Powder metallurgical techniques have been employed to prepare the precursor billets in the preparation of Cu-15 vol pct Fe
alloys by deformation processing. It has been demonstrated that by (1) using high-purity gas-atomized Cu powders blended with
commercial high-purity Fe powders and (2) controlling the time/temperature processing conditions within specific limits, it
is possible to produce Cu-Fe deformation-processed alloys with strength/conductivity properties matching those of Cu-Nb, Cu-Ta,
and Cu-Cr alloys. These properties are significantly superior to the best commercial alloys.
formerly with the Department of Materials Science and Engineering and Ames Laboratory, Iowa State University
This article is based on a presentation made in the symposium “High Performance Copper-Base Materials” as part of the 1991
TMS Annual Meeting, February 17–21, 1991, New Orleans, LA, under the auspices of the TMS Structural Materials Committee. 相似文献
100.
LS Melchers M Apotheker-de Groot JA van der Knaap AS Ponstein MB Sela-Buurlage JF Bol BJ Cornelissen PJ van den Elzen HJ Linthorst 《Canadian Metallurgical Quarterly》1994,5(4):469-480
A novel chitinase gene of tobacco was isolated and characterized by DNA sequence analysis of a genomic clone and a cDNA clone. Comparative sequence analysis of both clones showed an identity of 94%. The proteins encoded by these sequences do not correspond to any of the previously characterized plant chitinases of classes I-IV and are designated as class V chitinases. Comparison of the chitinase class V peptide sequence with sequences in the Swiss Protein databank revealed significant sequence similarity with bacterial exo-chitinases from Bacillus circulans, Serratia marcescens and Streptomyces plicatus. It was demonstrated that class V chitinase gene expression is induced after treatment of tobacco with different forms of stress, like TMV-infection, ethylene treatment, wounding or ultraviolet irradiation. Two related chitinase class V proteins of 41 and 43 kDa were purified from Samsun NN tobacco leaves inoculated with tobacco mosaic virus. The proteins were purified by Chelating Superose chromatography and gel filtration. In vitro assays demonstrated that class V chitinases have endo-chitinase activity and exhibit antifungal activity toward Trichoderma viride and Alternaria radicina. In addition, it was shown that class V chitinase acts synergistically with tobacco class I beta-1,3-glucanase against Fusarium solani germlings. 相似文献