全文获取类型
收费全文 | 4409篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
综合类 | 2篇 |
化学工业 | 209篇 |
金属工艺 | 18篇 |
机械仪表 | 30篇 |
建筑科学 | 136篇 |
矿业工程 | 1篇 |
能源动力 | 59篇 |
轻工业 | 131篇 |
水利工程 | 16篇 |
石油天然气 | 7篇 |
无线电 | 140篇 |
一般工业技术 | 153篇 |
冶金工业 | 3401篇 |
原子能技术 | 13篇 |
自动化技术 | 91篇 |
出版年
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 9篇 |
2017年 | 13篇 |
2016年 | 11篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 58篇 |
2012年 | 29篇 |
2011年 | 44篇 |
2010年 | 30篇 |
2009年 | 27篇 |
2008年 | 30篇 |
2007年 | 32篇 |
2006年 | 36篇 |
2005年 | 26篇 |
2004年 | 32篇 |
2003年 | 22篇 |
2002年 | 30篇 |
2001年 | 31篇 |
2000年 | 28篇 |
1999年 | 116篇 |
1998年 | 964篇 |
1997年 | 529篇 |
1996年 | 373篇 |
1995年 | 225篇 |
1994年 | 162篇 |
1993年 | 231篇 |
1992年 | 62篇 |
1991年 | 63篇 |
1990年 | 55篇 |
1989年 | 80篇 |
1988年 | 66篇 |
1987年 | 69篇 |
1986年 | 66篇 |
1985年 | 69篇 |
1984年 | 19篇 |
1983年 | 33篇 |
1982年 | 27篇 |
1981年 | 53篇 |
1980年 | 62篇 |
1979年 | 20篇 |
1978年 | 21篇 |
1977年 | 126篇 |
1976年 | 271篇 |
1975年 | 25篇 |
1973年 | 16篇 |
1955年 | 6篇 |
排序方式: 共有4427条查询结果,搜索用时 312 毫秒
71.
Combinations of EDTA-Tris and two aminoglycoside antibiotics (amikacin and neomycin) were tested for synergistic activities against the microorganisms associated with otitis externa in dogs and for the solutions' stability over time. Synergistic activity was observed when EDTA-Tris plus amikacin and EDTA-Tris plus neomycin were tested against Staphylococcus intermedius, Proteus mirabilis, Pseudomonas aeruginosa, and Escherichia coli, but not against Candida albicans. Stability studies over a 3-month period indicated that the test solutions were stable at room temperature and that their antimicrobial activity was maintained. 相似文献
72.
73.
S Nielsen A Schmitz RE Knudsen J Dollerup CE Mogensen 《Canadian Metallurgical Quarterly》1994,87(12):747-754
In a double-blind, double-dummy, randomized, multi-centre study, the effects of bendroflumethiazide vs. enalapril on blood pressure, glycaemic control, lipoprotein concentrations and albuminuria were compared in non-proteinuric, hypertensive type 2 diabetic patients; they were treated for 20 weeks with either bendroflumethiazide 2.5-5.0 mg (n = 59) or enalapril 10-20 mg (n = 55). Age, fasting plasma glucose, HbA1c and BMI were similar in the groups. Systolic and diastolic blood pressure were reduced in both groups. Bendroflumethiazide was accompanied by minor but significant elevations in fasting plasma glucose and serum C-peptide. HbA1c was increased during both treatments. Lipoproteins and urinary albumin/creatinine ratio were stable. Bendroflumethiazide caused a decrease in serum potassium and an increase in serum urate. No significant correlations were observed between the decline in blood pressure and changes in the metabolic risk factors. Baseline levels of age, sex, BMI, blood pressure or urinary albumin/creatinine ratio were not related to changes in blood pressure, metabolic parameters or urinary albumin/creatinine ratio. 相似文献
74.
ML Israel DA Connolly RE von Heyn JM Rock PW Smith 《Canadian Metallurgical Quarterly》1993,24(4):343-355
Fifty-two case-hardened, severely self-abusive and aggressive autistic and retarded students, living in six different community residences, were trained to exit their residences, without the presence or assistance of staff, when a fire alarm sounded at night. On a pretest, prior to an 11-week period of intensive environmental and behavioral interventions, only 25% of the students exited within 2 1/2 minutes and independent of staff assistance. At posttest, 100% exited successfully, in a mean evacuation time of 60 seconds. The study was conducted at the Behavior Research Institute (BRI). 相似文献
75.
AL Barry PC Fuchs C Thornsberry JC McLaughlin SG Jenkins DJ Hardy SD Allen 《Canadian Metallurgical Quarterly》1996,15(8):676-678
Three methods approved by the National Committee for Clinical Laboratory Standards for testing the susceptibility of anaerobic bacteria were used to evaluate the fluoroquinolone, trovafloxacin. The methods gave essentially comparable results with 126 anaerobes and with three quality control strains. A collaborative study defined the quality control range for trovafloxacin MICs. Trovafloxacin had good in vitro activity against the more common anaerobes (MIC 90 < = or 2.0 micrograms/ml). 相似文献
76.
JD Ragland DM Censits RC Gur DC Glahn F Gallacher RE Gur 《Canadian Metallurgical Quarterly》1996,60(2-3):135-145
The Paired Associate Recognition Test (PART) was developed to measure declarative memory using Wisconsin Card Sorting Test (WCST) stimuli, so that both tasks could be administered during functional neuroimaging to differentiate memory and executive function, and associated frontal and temporal lobe activation in schizophrenia. The current study was designed to compare PART and WCST performance in schizophrenic patients and to examine effects of medication and symptomatology. The PART, WCST, and standard declarative memory tasks were administered to 30 chronic schizophrenic patients and 30 matched healthy control subjects. Supporting task validity was the finding that patients were equally impaired on the PART and the WCST. Neuroleptics did not appear to affect performance. The effect of anticholinergic medication correlated negatively with WCST performance in a small subsample. Severity of schizophrenia-specific symptoms measured at intake on the Brief Psychiatric Rating Scale correlated negatively with performance on the WCST. These results support the application of the PART and WCST in future functional neuroimaging studies. 相似文献
77.
78.
The structure of pyramidatine [1], a new bisamide alkaloid from leaves of Aglaia pyramidata, was determined through extensive nmr studies, including homonuclear COSY, NOESY, APT, HETCOR, and selective INEPT techniques. Revision of the 13C-nmr assignment of piriferine [2], an alkaloid previously isolated from A. pirifera, was achieved by examination of several 2D nmr spectra (homonuclear COSY, NOESY, and HETCOR) and confirmed by selective INEPT nmr experiments. Evaluation of the cytotoxic potential of the two alkaloids, along with two other bisamides from Aglaia odorata, odorine [3] and 5'-epi-odorine [4], was carried out in eleven human cancer cell lines. None of these bisamides showed significant cytotoxicity. Nevertheless, piriferine [2], odorine [3], and 5'-epi-odorine [4] were found to inhibit the growth of the vinblastine-resistant KB cells by enhancing the anticancer activity of vinblastine. 相似文献
79.
AJ Morguet RE Gabriel AB Buchwald GS Werner R Nyga H Kreuzer 《Canadian Metallurgical Quarterly》1997,20(4):382-393
BACKGROUND AND OBJECTIVE: Spectroscopic guidance of laser angioplasty has been attempted using a diagnostic He-Cd laser in addition to the therapeutic laser system. This study evaluated a single-laser approach for simultaneous ablation and fluorescence excitation. STUDY DESIGN/MATERIALS AND METHODS: A spectroscopy system was coupled to a clinical XeCl excimer laser. Ablation of 162 human aortic samples in saline and blood with 45 mJ/mm2 per pulse yielded 676 fluorescence spectra validated histologically. The same equipment was used in 16 patients for angioplasty of 18 coronary stenoses applying 500 to 1,725 pulses with 45 to 60 mJ/mm2 under saline flushing. A total of 783 spectra were recorded and validated by intracoronary ultrasound (categories: atheroma, fibrous plaque, calcified lesion). RESULTS: In vitro, 5 types of spectra could be differentiated: (1) atheroma, (2) fibrous plaque, (3) calcified lesion in saline, (4) media, and (5) calcified lesion in blood. Discriminant analysis prospectively classified 576 validation spectra with the following sensitivity and specificity for each type: (1) 83.5 and 97.1%, (2) 85.7 and 96.8% (3) 100 and 98.5%, (4) 98.1 and 99.3%, (5) 98.9 and 100%, respectively. In vivo type 1, 2, 3, and 5 spectra were also observed, but not the media spectrum. The predominant sonographic category also prevailed in spectroscopy. Calcified lesions yielded type 3 and 5 as well as mixed spectra. CONCLUSIONS: Using an excimer laser for angioplasty allows combining ablation and fluorescence excitation without a diagnostic laser. Principal types of atherosclerotic lesions and the media can be differentiated spectroscopically with this approach. 相似文献
80.
RW Hanf RG Schreckhise GW Patton TM Poston RE Jaquish 《Canadian Metallurgical Quarterly》1997,73(4):700-705
In 1989, Pacific Northwest National Laboratory developed a program, for the U.S. Department of Energy, to involve local citizens in environmental surveillance at the Hanford Site. The Community-Operated Environmental Surveillance Program was patterned after similar community-involvement efforts at the Nevada Test Site and the Three Mile Island nuclear facility. Its purpose is to increase the flow of information to the public, thereby enhancing the public's awareness and understanding of surveillance activities. The program consists of two components: radiological air monitoring at nine offsite locations and agricultural product sampling at selected locations near the site. At each air-monitoring station, two local school teachers collect air particulate samples and operate equipment to monitor ambient radiation levels. Atmospheric tritium samples (as water vapor) are also collected at some locations. Four of the air-monitoring stations include large, colorful informational displays for public viewing. These displays provide details on station equipment, sample types, and sampling purposes. Instruments in the displays also monitor, record, and show real-time ambient radiation readings (measured with a pressurized ionization chamber) and meteorological conditions. Agricultural products, grown primarily by middle-school-aged students, are obtained from areas downwind of the site. Following analysis of these samples, environmental surveillance staff visit the schools to discuss the results with the students and their teachers. The data collected by these air and agricultural sampling efforts are summarized with other routinely collected sitewide surveillance data and reported annually in the Hanford Site environmental report. 相似文献