全文获取类型
收费全文 | 3233篇 |
免费 | 15篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 17篇 |
综合类 | 12篇 |
化学工业 | 46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 | 75篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 2篇 |
一般工业技术 | 40篇 |
冶金工业 | 2975篇 |
自动化技术 | 40篇 |
出版年
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 43篇 |
2012年 | 24篇 |
2011年 | 16篇 |
2010年 | 14篇 |
2009年 | 20篇 |
2008年 | 16篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 10篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 98篇 |
1998年 | 932篇 |
1997年 | 564篇 |
1996年 | 349篇 |
1995年 | 170篇 |
1994年 | 144篇 |
1993年 | 206篇 |
1992年 | 25篇 |
1991年 | 12篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 21篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 21篇 |
1980年 | 26篇 |
1979年 | 2篇 |
1978年 | 11篇 |
1977年 | 94篇 |
1976年 | 209篇 |
1975年 | 7篇 |
1973年 | 2篇 |
1969年 | 2篇 |
1964年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有3261条查询结果,搜索用时 15 毫秒
101.
RA Nugent M Murphy ST Schlachter CJ Dunn RJ Smith ND Staite LA Galinet SK Shields DG Aspar KA Richard 《Canadian Metallurgical Quarterly》1993,36(1):134-139
Vinylidenebisphosphonic acid tetraethyl ester (1) and diazo ketones 7a-1 in ether at 22 degrees C yield pyrazoline bisphosphonate tetraethyl esters 8a-1 in moderate to good yield. These compounds were evaluated in animal models of arthritis: rat adjuvant-induced polyarthritis (AIP) and murine antigen-induced arthritis (AIA) and a murine model of chronic inflammation, the delayed type hypersensitivity granuloma reaction (DTH-GRA). (5-Benzoyl-2,4-dihydro-3H-pyrazol-3-ylidene)-bisphosphonic acid tetraethyl ester (8a), and [5-(3-fluorobenzoyl)-2,4-dihydro-3H-pyraxol-3-ylidene]- bisphosphonic acid tetraethyl ester (8d) significantly inhibited the arthritis models, AIP (15 mg/kg) and AIA (25 mg/kg), as well as the DTH-GRA (25 mg/kg). Conversion of 8a to the corresponding bisphosphonic acid, 10a, resulted in loss of activity. Compounds with alkyl substituents on the pyrazoline nitrogen, 9a-d, were inactive in the DTH-GRA. These results show that 8a and 8d have novel antiinflammatory activity and are capable of inhibiting chronic arthritis and inflammation in animals. Such compounds might be useful in man for treating chronic tissue injury associated with arthropathies such as inflammatory joint disease as well as other chronic inflammatory diseases. 相似文献
102.
GIu Sharaevski? LA Tiunov VV Chumakov VS Sukhorukov 《Canadian Metallurgical Quarterly》1996,317(8):66-70, 80
From position of the uniform concept of the accident medicine the problems of toxicological supply of the ships of MNF are considered. Peculiarities of chemical accidents in the ship conditions are marked. The question about principles of harmful chemical substances regulating, forming air environment of ship living quarters is discussed. The prospects of practical use of antidotal means, intended for protection of personnel from toxic action of carbon dioxide and chemical combinations, causing development of toxic edema of lungs are given. 相似文献
103.
Diabetic ulcers are the most common foot injuries leading to lower extremity amputation. Family physicians have a pivotal role in the prevention or early diagnosis of diabetic foot complications. Management of the diabetic foot requires a thorough knowledge of the major risk factors for amputation, frequent routine evaluation and meticulous preventive maintenance. The most common risk factors for ulcer formation include diabetic neuropathy, structural foot deformity and peripheral arterial occlusive disease. A careful physical examination, buttressed by monofilament testing for neuropathy and noninvasive testing for arterial insufficiency, can identify patients at risk for foot ulcers and appropriately classify patients who already have ulcers or other diabetic foot complications. Patient education regarding foot hygiene, nail care and proper footwear is crucial to reducing the risk of an injury that can lead to ulcer formation. Adherence to a systematic regimen of diagnosis and classification can improve communication between family physicians and diabetes subspecialists and facilitate appropriate treatment of complications. This team approach may ultimately lead to a reduction in lower extremity amputations related to diabetes. 相似文献
104.
The -514 polymorphism in the hepatic lipase gene (LIPC) is associated with decreased hepatic lipase activity. In the present study, the interaction between body mass index (BMI), the -514 polymorphism, and hepatic lipase activity was examined in 118 white men and in 51 African American men. BMI was significantly positively correlated with hepatic lipase activity in both populations. BMI was similar in men with genetic differences in hepatic lipase activity, indicating that high hepatic lipase activity did not cause increased BMI. The data therefore suggest that high BMI leads to increased hepatic lipase activity. The actions of BMI and the -514 polymorphism on hepatic lipase activity appear to be additive and independent, rather than synergistic. This finding indicates that hepatic lipase activity is a multifactorial trait, determined in part by polymorphism within the LIPC gene as well as by factors that influence BMI. 相似文献
105.
Many studies have shown the high correlation between Lunar and Hologic DXA bone mineral density (BMD) measurements despite differences in absolute calibration. However, in clinical practice, raw BMD values (in g/cm2) are not normally used for assessing skeletal status and fracture risk. Instead, the BMD values are expressed in terms of the number of standard deviations above or below the young normal value (commonly referred to as the T-score). If the normative populations of the various systems are consistent, the standard deviation scores should also be consistent. For this reason, the World Health Organization (WHO) recently established diagnostic criteria for osteoporosis based on T-scores and not BMD. However, few studies have compared the instruments in terms of their standard deviation scores. In this study, we used linear regression to compare T-scores in 83 women at L1-4 and 120 women at the femoral neck obtained on a Lunar DPX and a Hologic QDR-1000/W system. patient BMD and T-score measurements were highly correlated between the two systems (r > 0.95). No clinically significant difference in L1-4 T-scores was seen (less than 0.1 SD). However, linear regression analysis confirmed a systematic difference of 0.9 SD between the femoral neck T-scores. This discrepancy is caused by: (1) differences in the normal populations, and (2) differences in statistical models used to determine the young normal mean and standard deviation. In an attempt to correct the discrepancy, the female young normal mean and standard deviation were recalculated for the femoral neck using published epidemiological data from NHANES and existing DXA cross-calibration equations. The Hologic young normal value (mean +/- SD) was redefined as 0.85 +/- 0.11 g/cm2, while the Lunar value was redefined as 1.00 +/- 0.11 g/cm2. When the femoral neck T-scores for the study population were recalculated on the basis of these new values, the results were equivalent between manufactures, effectively eliminating the discrepancy. However, the revised values should be confirmed by additional measurements in young normal adults. 相似文献
106.
LA Pagan-Carlo JJ Allan KT Spencer CL Birkett R Myers RE Kerber 《Canadian Metallurgical Quarterly》1998,32(7):2065-2071
OBJECTIVES: This study was performed to determine the efficacy of new encircling overlapping multipulse, multipathway waveforms for transthoracic defibrillation. BACKGROUND: Alternative waveforms for transthoracic defibrillation may improve shock success. METHODS: First, we determined the shock success achieved by three different waveforms at varying energies (18-150 J) in 21 mongrel dogs after short-duration ventricular fibrillation. The waveforms tested included the traditional damped sinusoidal waveform, a single pathway biphasic waveform, and a new encircling overlapping multipulse waveform delivered from six electrode pads oriented circumferentially. Second, in 11 swine we compared the efficacy of encircling overlapping multipulse shocks given from six electrode pads and three capacitors versus encircling overlapping shocks given from a device utilizing three electrodes and one capacitor. RESULTS: In the first experiment, the encircling overlapping waveform performed significantly better than biphasic and damped sinusoidal waveforms at lower energies. The shock success rate of the overlapping waveform (six pads) ranged from 67+/-4% (at 18-49 J energy) to 99+/-3% at > or = 150 J; at comparable energies biphasic waveform shock success ranged from 26+/-5% (p < 0.01 vs. encircling overlapping waveforms) to 99+/-5% (p = NS). Damped sinusoidal waveform shock success ranged from 4+/-1% (p < 0.01 vs. encircling overlapping waveform) to 73+/-9% (p = NS). In the second experiment the three electrode pads, one capacitor encircling waveform achieved shock success rates comparable with the six-pad, three-capacitor waveform; at 18-49 J, success rates were 45+/-15% versus 57+/-12%, respectively (p = NS). At 100 J, success rates for both were 100%. CONCLUSIONS: We conclude that encircling overlapping multipulse multipathway waveforms facilitate transthoracic defibrillation at low energies. These waveforms can be generated from a device that requires only three electrodes and one capacitor. 相似文献
107.
LA Huber O Ullrich Y Takai A Lütcke P Dupree V Olkkonen H Virta MJ de Hoop K Alexandrov M Peter 《Canadian Metallurgical Quarterly》1994,91(17):7874-7878
For identification of Rab, Rac, Rho, Ral, Rap, and Arf proteins on two-dimensional polyacrylamide gels, we have expressed full-length cDNAs of members of these protein families with the T7 RNA polymerase-recombinant vaccinia virus expression system. Membrane preparations from cells expressing the cDNAs were subjected to high-resolution two-dimensional polyacrylamide gel electrophoresis followed by [alpha-32P]GTP ligand blotting. We have mapped 28 small GTP-binding proteins relative to their isoelectric points and according to their molecular weights and by immunoblotting with specific antibodies. Rab and Rho proteins could be specifically identified by extraction of streptolysin O-permeabilized Madin-Darby canine kidney (MDCK) cells with Rab- and Rho-GDP dissociation inhibitor. We applied the reference mapping to analyze the GTP-binding patterns of synaptosome fractions from rat brain. The purified synaptosomes exhibited specific enrichment of Rab3a, Rab5a, Ral, and several other GTPases. This approach and the map we have produced should provide a useful aid for the analysis of the expression and localization of members of all families of small GTP-binding proteins in various cell types and subcellular fractions. 相似文献
108.
The effects of intranasal syringing with 5% zinc sulfate were assessed in rats trained in a wind-tunnel olfactometer to detect the presence of an odor or to discriminate odors of graded intensities. The syringing produced a severe but brief interference in olfactory performance. Full recovery of detection performance occurred within 72 hr after treatment. Initial recovery of odor intensity discrimination occurred in 2-8 days and full recovery within 8-10 days. These results suggest that intranasal syringing with ZnSO4 is not an adequate control for the effects of anosmia produced by olfactory bulbectomy. 相似文献
109.
SN Magonov RM Davydov LA Bliumenfel'd AM Arutiunian IuA Sharonov 《Canadian Metallurgical Quarterly》1978,12(5):1191-1197
Absorption and magnetic curcular dichroism spectra of nonequilibrium states of peroxidase and its complexes with F-, N3-, CN- produced by reduction of oxidased forms of proteins by thermalysed electrons at 77 degrees K were studied. Mixtures of high spin and low spin ferroforms were found in nonequilibrium states of peroxidase and complexes with F- and N3-, the content of the high spin ferroform increasing as follows: N3- complex less than peroxidase less than fluorine complex. Only low spin ferroforms was found after low temperature reduction of the cyanide complex. The existence of the low spin ferroform in equilibrium states of peroxidase and its complex with F- was explained by location of iron near the porphyrine plane. In the case of azide and cyanide complexes the existence of the low spin form is due to the presence of these ligands in heme iron's coordination sphere. The temperature relaxation of all nonequilibrium forms was investigated and a possible mechanism of the process is proposed. 相似文献
110.