全文获取类型
收费全文 | 3187篇 |
免费 | 73篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 11篇 |
化学工业 | 558篇 |
金属工艺 | 13篇 |
机械仪表 | 27篇 |
建筑科学 | 33篇 |
矿业工程 | 1篇 |
能源动力 | 49篇 |
轻工业 | 224篇 |
水利工程 | 7篇 |
石油天然气 | 1篇 |
无线电 | 59篇 |
一般工业技术 | 209篇 |
冶金工业 | 1971篇 |
原子能技术 | 5篇 |
自动化技术 | 94篇 |
出版年
2024年 | 3篇 |
2023年 | 29篇 |
2022年 | 85篇 |
2021年 | 103篇 |
2020年 | 34篇 |
2019年 | 40篇 |
2018年 | 56篇 |
2017年 | 46篇 |
2016年 | 53篇 |
2015年 | 45篇 |
2014年 | 48篇 |
2013年 | 74篇 |
2012年 | 61篇 |
2011年 | 91篇 |
2010年 | 73篇 |
2009年 | 50篇 |
2008年 | 79篇 |
2007年 | 67篇 |
2006年 | 52篇 |
2005年 | 28篇 |
2004年 | 25篇 |
2003年 | 33篇 |
2002年 | 23篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 61篇 |
1998年 | 586篇 |
1997年 | 315篇 |
1996年 | 253篇 |
1995年 | 155篇 |
1994年 | 111篇 |
1993年 | 110篇 |
1992年 | 24篇 |
1991年 | 42篇 |
1990年 | 38篇 |
1989年 | 22篇 |
1988年 | 28篇 |
1987年 | 33篇 |
1986年 | 29篇 |
1985年 | 37篇 |
1984年 | 3篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1978年 | 4篇 |
1977年 | 33篇 |
1976年 | 104篇 |
1975年 | 9篇 |
1970年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有3262条查询结果,搜索用时 0 毫秒
1.
2.
3.
Andreja ?gajnar Gotvajn Jana Zagorc-Kon?an Tatjana Ti?ler 《Canadian Metallurgical Quarterly》2007,133(1):89-94
The preoxidation of a highly polluted waste pharmaceutical fermentation broth using wet air oxidation (WAO) has been studied as a possible method for the effective removal of organics. The applied (pre)treatment method should enhance the biotreatability of the pharmaceutical fermentation broth in terms of reduced initial toxicity and higher biodegradability. Preliminary experiments in the pilot biological treatment plant were successful only at low organic loads, whereas the system collapses at higher ones. The characterization of the fermentation broth was started by common physicochemical analysis, whereas several bioassays were used to determine its impact on biological treatment plants and the environment. Toxicity prior to and after WAO was determined using the acute Vibrio fischeri test, measurement of inhibition of O2 consumption, and the Daphnia magna acute test. Ready biodegradability of the treated and untreated broth has also been assessed. WAO experiments were accomplished in the 2?L batch reactor at different temperatures (240/280°C) and operating pressures. WAO experiments confirmed reduction of the toxicity toward microorganisms, whereas oxidized wastewater was more toxic to daphnids. Biodegradability of the oxidized broth has also been enhanced. Further work has been focused on designing appropriate combination of WAO and biological processes. 相似文献
4.
A 78-year-old Chinese woman presented with recurrent postprandial abdominal pain. Computerised tomography revealed a small bowel tumour causing volvulus of a segment of the small bowel. Laparotomy confirmed an extraluminal ileal tumour with partial volvulus of the involved small bowel segment. Small bowel resection was done. Histological and ultrastructural studies confirmed a gastrointestinal autonomic nerve tumour. We review the medical literature on this rare tumour. 相似文献
5.
BD Shenstone A Mahmoud R Woodward D Elvins R Palmer EF Ring AK Bhalla 《Canadian Metallurgical Quarterly》1994,33(6):541-545
A prospective longitudinal study of patients with early RA was performed to examine the influence of disease duration, disease activity and physical activity on bone loss. Sixty-seven patients with non-steroid treated RA of less than 5 yr duration, including 16 patients with disease duration less than 6 months, had BMD measurements of the femoral neck and the lumbar spine over a 12-month period using dual energy X-ray absorptiometry. The BMD changes were compared with values from 72 control patients and were also correlated with serial measurements of disease activity (measured by the Stoke Index) and disability [measured by the Health Assessment Questionnaire (HAQ) score], at 3-monthly intervals over the 12-month period. No significant differences in BMD changes were found between RA patients and controls overall. Patients with disease duration of less than 6 months had significantly greater loss of BMD at the femoral neck (-3.9%, S.E.M. 1.5) than the remainder of the cohort (-0.2%, S.E.M. 0.7) (P = 0.02) and controls (-0.8%, S.E.M. 0.6). Lumbar spine BMD changes correlated with the initial Stoke Index (Rs-0.373, P = 0.01) but not mean Stoke Indices. There was no correlation of BMD changes with age or HAQ scores. These findings suggest that significant bone loss occurs within the first few months of disease in patients with RA. 相似文献
6.
A genetic algorithm for multiple molecular sequence alignment 总被引:1,自引:0,他引:1
MOTIVATION: Multiple molecular sequence alignment is among the most important and most challenging tasks in computational biology. The currently used alignment techniques are characterized by great computational complexity, which prevents their wider use. This research is aimed at developing a new technique for efficient multiple sequence alignment. APPROACH: The new method is based on genetic algorithms. Genetic algorithms are stochastic approaches for efficient and robust searching. By converting biomolecular sequence alignment into a problem of searching for optimal or near-optimal points in an 'alignment space', a genetic algorithm can be used to find good alignments very efficiently. RESULTS: Experiments on real data sets have shown that the average computing time of this technique may be two or three orders lower than that of a technique based on pairwise dynamic programming, while the alignment qualities are very similar. AVAILABILITY: A C program on UNIX has been written to implement the technique. It is available on request from the authors. 相似文献
7.
8.
9.
10.
Kreppner Jana M.; Rutter Michael; Beckett Celia; Castle Jenny; Colvert Emma; Groothues Christine; Hawkins Amanda; O'Connor Thomas G.; Stevens Suzanne; Sonuga-Barke Edmund J. S. 《Canadian Metallurgical Quarterly》2007,43(4):931
Longitudinal analyses on normal versus impaired functioning across 7 domains were conducted in children who had experienced profound institutional deprivation up to the age of 42 months and were adopted from Romania into U.K. families. Comparisons were made with noninstitutionalized children adopted from Romania and with nondeprived within-U.K. adoptees placed before the age of 6 months. Specifically, the validity of the assessment, the degree of continuity and change in levels of functioning from 6 to 11 years, and the factors in the pre- and postadoption environment accounting for heterogeneity in outcome were examined. Pervasive impairment was significantly raised in children experiencing institutional deprivation for ≥6 months of life, with a minority within this group showing no impairment. There was no additional significant effect of duration of deprivation beyond the 6-month cutoff, and few other predictors explained outcome. The pattern of normality/impairment was mainly established by 6 years of age, with considerable continuity at the individual level between 6 and 11 years. The findings are discussed in terms of the possibility of a sensitive period for development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献