全文获取类型
收费全文 | 3237篇 |
免费 | 14篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 19篇 |
综合类 | 12篇 |
化学工业 | 37篇 |
金属工艺 | 21篇 |
机械仪表 | 11篇 |
建筑科学 | 12篇 |
矿业工程 | 1篇 |
能源动力 | 5篇 |
轻工业 | 74篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 3篇 |
一般工业技术 | 44篇 |
冶金工业 | 2978篇 |
自动化技术 | 43篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 44篇 |
2012年 | 23篇 |
2011年 | 17篇 |
2010年 | 16篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 98篇 |
1998年 | 932篇 |
1997年 | 563篇 |
1996年 | 351篇 |
1995年 | 172篇 |
1994年 | 143篇 |
1993年 | 206篇 |
1992年 | 25篇 |
1991年 | 12篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 20篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 21篇 |
1980年 | 26篇 |
1979年 | 2篇 |
1978年 | 11篇 |
1977年 | 94篇 |
1976年 | 208篇 |
1975年 | 7篇 |
1973年 | 2篇 |
1955年 | 4篇 |
1939年 | 1篇 |
排序方式: 共有3264条查询结果,搜索用时 0 毫秒
991.
F Inserra LA Romano EM de Cavanagh L Ercole LF Ferder RA Gomez 《Canadian Metallurgical Quarterly》1996,7(5):676-680
Microwave effects on drosophila morphogenesis were studied. Drosophila embryo were exposed by continuous wave 460 MHz at SAR = 1-5 Wt/kg. It was found that irradiation induced some morphosis such as imago legs and wings form alterations. These effects depended on embryo age, SAR and period exposure. It was proposed that the local microwave heating is responsible for describe effects. 相似文献
992.
SS Bo?ko VP Zherdev AA Dvorianinov SB Seredenin LIu Alfeeva LA Andreeva SV Bezmenova NF Miasoedov 《Canadian Metallurgical Quarterly》1998,61(5):42-45
The lymphocyte blast transformation test (LBTT) with three tuberculin dilutions was used to examine 190 patients with varying pulmonary tuberculosis activity, of them 63 patients received chemotherapy. According to the blast formation in the patients' cultured peripheral blood cells by three tuberculin dilutions, a correlation was found between the clinical manifestations of the process and the functional activity of T lymphocytes. Thus, the greatest percentage (500 TU) of blasts in LBTT per mean PPD dose was detectable in patients with low LBTT results by three tuberculin dilutions with positive dynamics during chemotherapy. With further positive dynamics, the proportion of blasts in the cultured peripheral blood cells was highest per high PPD doses (5000 TU). On the contrary, patients with progressive tuberculosis displayed a oppositely directed phasic pattern. 相似文献
993.
LA Gaudette A Richardson S Huang 《Canadian Metallurgical Quarterly》1998,10(3):35-45 (ENG); 35-47 (FRE)
OBJECTIVES: This article examines differences by occupation in daily cigarette smoking prevalence and intensity among full-time workers, and how these differences are associated with smoking restrictions at work. DATA SOURCES: Most of the data are from a Health Canada-sponsored Supplement to the 1994/95 National Population Health Survey (NPHS). The analysis is based on 5,674 respondents aged 15 to 64 who were full-time workers at the time of their interview. Comparable information is presented from the 1978/79 Canada Health Survey and the 1986 Labour Force Survey Smoking Supplement. MAIN RESULTS: In 1994/95, 28% of full-time workers were daily smokers, and about a third of them smoked 25 or more cigarettes a day. Smoking prevalence and intensity were lowest among white-collar workers and highest among blue-collar workers. Since 1978/79, there has been an overall decline in smoking prevalence, and since 1986, a decline in smoking intensity among all workers except those in outdoor blue-collar occupations. About 6 in 10 full-time workers who smoked daily encountered restrictions at work. 相似文献
994.
We have compared the ability of two mammalian Notch homologs, mouse Notchl and Notch2, to inhibit the granulocytic differentiation of 32D myeloid progenitor cells. 32D cells undergo granulocytic differentiation when stimulated with either granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF). Expression of the activated intracellular domain of Notch1 inhibits the differentiation induced by G-CSF but not by GM-CSF; conversely, the corresponding domain of Notch2 inhibits differentiation in response to GM-CSF but not to G-CSF. The region immediately C-terminal to the cdc10 domain of Notch confers cytokine specificity on the cdc10 domain. The cytokine response patterns of Notch1 and Notch2 are transferred with this region, which we have termed the Notch cytokine response (NCR) region. The NCR region is also associated with differences in posttranslational modification and subcellular localization of the different Notch molecules. These findings suggest that the multiple forms of Notch found in mammals have structural differences that allow their function to be modulated by specific differentiation signals. 相似文献
995.
996.
OBJECTIVE: To demonstrate that humans can learn to control selected electroencephalographic components and use that control to answer simple questions. METHODS: Four adults (one with amyotrophic lateral sclerosis) learned to use electroencephalogram (EEG) mu rhythm (8 to 12Hz) or beta rhythm (18 to 25Hz) activity over sensorimotor cortex to control vertical cursor movement to targets at the top or bottom edge of a video screen. In subsequent sessions, the targets were replaced with the words YES and NO, and individuals used the cursor to answer spoken YES/NO questions from single- or multiple-topic question sets. They confirmed their answers through the response verification (RV) procedure, in which the word positions were switched and the question was answered again. RESULTS: For 5 consecutive sessions after initial question training, individuals were asked an average of 4.0 to 4.6 questions per minute; 64% to 87% of their answers were confirmed by the RV procedure and 93% to 99% of these answers were correct. Performances for single- and multiple-topic question sets did not differ significantly. CONCLUSIONS: The results indicate that (1) EEG-based cursor control can be used to answer simple questions with a high degree of accuracy, (2) attention to auditory queries and formulation of answers does not interfere with EEG-based cursor control, (3) question complexity (at least as represented by single versus multiple-topic question sets) does not noticeably affect performance, and (4) the RV procedure improves accuracy as expected. Several options for increasing the speed of communication appear promising. An EEG-based brain-computer interface could provide a new communication and control modality for people with severe motor disabilities. 相似文献
997.
SC Humphreys SD Hodges A Patwardhan JC Eck LA Covington M Sartori 《Canadian Metallurgical Quarterly》1998,23(20):2180-2184
STUDY DESIGN: This study was intended to identify normal degenerative morphologic evolution in the bony foramen in asymptomatic subjects by decade in comparison with symptomatic subjects of like decades. OBJECTIVES: To determine normal degenerative changes in the cervical spine caused by the aging process that predispose a person to foraminal stenosis and radiculopathy. SUMMARY OF BACKGROUND DATA: Cervical radiculopathy is a common problem caused by degenerative changes as people age. The characteristics of the foramen that result in stenosis are not known. METHODS: Five to six symptomatic and asymptomatic people in each decade volunteered for magnetic resonance imaging. Lordosis, disc heights, and ratio of spinal cord diameter to spinal canal diameter were measured at C4-C5, C5-C6, and C6-C7 from sagittal magnetic resonance images. Foraminal heights, widths, and areas were measured at the isthmus of the same foramen from oblique images. RESULTS: Foraminal heights, widths, and areas were larger in asymptomatic patients than in symptomatic patients. Morphologic analysis showed that inferior facet hypertrophy tended to decrease the width of the foramen in aging people. Disc heights, lordosis, and ratio of spinal cord diameter to spinal canal diameter showed no significant differences. CONCLUSIONS: Foraminal height affects overall foraminal area but tends to change little with age. Width also affects overall area and not only decreases in older people but also significantly affects the available area for the exiting nerve root. 相似文献
998.
Value of CT angiography for postoperative assessment of patients with iliac artery aneurysms who have received endovascular grafts 总被引:1,自引:0,他引:1
AM Rozenblit J Cynamon S Maddineni ML Marin LA Sanchez J Yuan FJ Veith 《Canadian Metallurgical Quarterly》1998,170(4):913-917
OBJECTIVE: To determine the pathologic outcome in human immunodeficiency virus (HIV)-seropositive individuals with nonspecific bronchoalveolar lavage (BAL) cytology. STUDY DESIGN: The study group consisted of 126 cytologically negative or nonspecific BAL specimens from HIV-seropositive adults. Concurrent microbial cultures and transbronchial biopsies, as well as subsequent pulmonary cytology, lung biopsy or autopsy results were reviewed. Additionally, the cytologic morphology of specimens from patients found to have a potential bacterial pathogen was reviewed. RESULTS: In the 126 cases with nonspecific BAL cytology, a potential pulmonary pathogen was identified from a concurrent or subsequent pathologic specimen in 27% of cases, while no pathogen was identified in 73% of cases. Bacteria and fungi were the most common pathogens identified. Microbial cultures alone identified the pathogen in 59% of cases, while transbronchial biopsy added information in only 9%. Specimens with marked acute inflammation often yielded bacterial pathogens on microbial culture. CONCLUSION: A potential pulmonary pathogen can be identified in 27% of HIV-seropositive individuals with negative BAL cytology using other diagnostic modalities. Bacterial pathogens are most common and are usually identified by microbial culture. Marked acute inflammation in a BAL specimen is often associated with bacterial pneumonia. 相似文献
999.
TM Reshetniak RV Derksen ZS Alekberova D Horbach F De Groot EL Nasonov LA Kalashnikova ES Match VA Nasonova 《Canadian Metallurgical Quarterly》1998,76(3):36-40
Antibodies to beta 2-glycoprotein in the serum of patients with antiphospholipid syndrome (APS) were found by many investigators, but their results appeared contraversional. We studied clinical significance of antibodies to beta 2-glycoprotein I (anti-beta 2-GPI) in patients with SLE. 69 patients with verified SLE were examined for lupus anticoagulant (LA), antibodies to cardiolipin (aCL) and anti-beta 2-GPI. 44(65%), 46(67%), 49(71%), 19(28%), 16(23%) patients were positive for LA, IgG-aCL, IgM-aCL, IgG-anti-beta 2-GPI and IgM-anti-beta 2-GPI, respectively. Hyperproduction of IgG-anti-beta 2-GPI correlated with APS development as a whole, its separate clinical symptoms (venous and arterial thromboembolism, obstetric pathology and thrombocytopenia) and some comcomitant clinical signs (trophic crural ulcer, hemolytic anemia, valvular heart disorders). Moreover, an increase in concentration of IgM-anti-beta 2-GPI was associated with habitual abortion. Both isotypes of anti-beta 2-GPI occurred more frequently in the sera positive by LA and aCL. It is interesting that we discovered IgG-anti-beta 2-GPI more often in early than late postthrombolytic period. Thus, anti-2b2-GPI is a new serological marker of APS. Its detection is clinically important for upgrading diagnosis of APS. 相似文献
1000.
A Ribas J Albanell LA Solé-Calvo E Gallardo J Bellmunt R Vera R Vidal J Carulla J Baselga 《Canadian Metallurgical Quarterly》1998,82(5):878-885
BACKGROUND/AIMS/METHODS: The distribution characteristics of a human colon carcinoma cell line, KM12-HX cells, were examined. After intraportal vein (i.p.v.) or intravenous (i.v.) injection into rats, almost all the injected tumor cells are distributed to liver or lung, respectively, both after 30 s and 30 min. Our previous kinetic analysis of the fate of tumor cells revealed that the cumulative amount of tumor cells distributed in the liver is a factor determining the degree of metastasis. Thus, we examined the mechanism of initial efficient trapping of tumor cells by the liver in more detail. RESULTS: Thirty minutes after tumor cells were injected into the left ventricle of the heart, the distribution of tumor cells was more restricted in several tissues (kidney, small intestine, large intestine and spleen), as compared with the distribution of microspheres undergoing 100% extraction, indicating that the first-pass extraction of KM12-HX cells is incomplete in these organs. The hepatic first-pass distribution of these tumor cells was unaffected by pretreatment of liposomes, such that the preinjected amount was sufficient to saturate the phagocytotic function of macrophages. Thus, the mechanism of initial distribution of the tumor cells to the liver is different from the mechanism of liposome uptake by macrophages. Considering that the diameter of microvessels in sinusoid and KM12-HX cells is approximately 7 and 12 microm, respectively, it is possible that these tumor cells are trapped physically in hepatic microvessels. In fact, after i.p.v. injection of microspheres 5 microm in diameter, only 20% of the dose was distributed to liver and the rest to other tissues. In contrast, almost 100% of microspheres 10 microm in diameter were distributed to the liver. CONCLUSIONS: These results support the hypothesis that the initial organ distribution of blood-borne tumor cells is determined by mechanical and physical properties of the cells. 相似文献