全文获取类型
收费全文 | 2768篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 15篇 |
建筑科学 | 6篇 |
轻工业 | 27篇 |
石油天然气 | 2篇 |
无线电 | 7篇 |
一般工业技术 | 16篇 |
冶金工业 | 2689篇 |
自动化技术 | 6篇 |
出版年
2021年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 2篇 |
2008年 | 1篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 81篇 |
1998年 | 817篇 |
1997年 | 475篇 |
1996年 | 305篇 |
1995年 | 169篇 |
1994年 | 138篇 |
1993年 | 175篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 27篇 |
1989年 | 34篇 |
1988年 | 49篇 |
1987年 | 35篇 |
1986年 | 30篇 |
1985年 | 28篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 50篇 |
1976年 | 155篇 |
1975年 | 10篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1957年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有2769条查询结果,搜索用时 15 毫秒
991.
DR Joseph 《Canadian Metallurgical Quarterly》1997,62(8-9):578-588
Androgen-binding protein/sex hormone-binding globulin (ABP/SHBG) is an extracellular binding protein that regulates the bioavailability of sex steroids. ABP/SHBG is closely related to the globular (G) domain of vitamin K-dependent protein S family of proteins and more distantly related to the G domains of several extracellular matrix proteins. ABP/SHBG appears to have evolved from the fusion of two ancestral G domains. Expanding evidence suggests that ABP/SHBG has other functions that are mediated through membrane binding, including signal transduction; however, the types of binding proteins (receptors) have not been identified. Sequence comparisons of ABP/SHBG with G domains of its homologs protein S, Gas6, laminin, and agrin have identified regions of ABP/SHBG that may bind receptors related to homolog receptors. These membrane receptors include beta-integrins, alpha-dystroglycan, and receptor tyrosine kinases. The G domains of laminin and related proteins have clearly evolved from a common ancestor to interact with specific receptors and binding proteins. It remains to be determined if ABP/SHBG followed this evolutionary pathway. 相似文献
992.
DR Brooks P Wang M Read WM Watkins PF Sims JE Hyde 《Canadian Metallurgical Quarterly》1994,224(2):397-405
Dihydropteroate synthase (H2Pte synthase) is the target of the sulfur-based antimalarial drugs, which are frequently used in synergistic combination with inhibitors of dihydrofolate reductase (H2folate reductase) to combat chloroquine-resistant malaria. We have isolated the H2Pte synthase coding sequence of the most pathogenic human parasite Plasmodium falciparum. It forms part of a longer coding sequence, located on chromosome 8, that also specifies 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (CH2OH-H2pterinPP kinase) at its 5' proximal end. This domain is unusually large, with two long insertions relative to other CH2OH-H2pterinPP kinase molecules. To investigate a possible genetic basis for clinical resistance to sulfa drugs, we sequenced the complete H2Pte synthase domains from eleven isolates of P. falciparum with diverse geographical origins and levels of sulfadoxine resistance. Overall, point mutations in five positions were observed, affecting four codons. Parasite lines exhibiting high-level resistance were found to carry either a double mutation, altering both Ser436 and Ala613, or a single mutation affecting Ala581. The mutations at positions 436 and 581 have the same location relative to each of two degenerate repeated amino acid motifs that are conserved across all other known H2Pte synthase molecules. The amino acid alteration at residue 613 is identically positioned relative to a different conserved motif. The fourth amino acid residue (437) affected by mutation, though adjacent to the apparently crucial residue 436, shows no obvious correlation with resistance. Although these mutations have no exact counterparts in any other organism, that at position 581 falls within a region of three amino acids where H2Pte synthase is modified in various ways in a number of sulfonamide-resistant pathogenic bacteria. Copy-number analysis indicated that there was no amplification of the H2Pte synthase domain in resistant parasite lines of P. falciparum, compared to sensitive lines. 相似文献
993.
A retrospective study was performed of 30 women who had undergone breast reduction and subsequently wished to breastfeed. Breastfeeding capabilities were assessed by a trained lactation consultant. Findings indicate that in women who have a physiological type of operation then breastfeeding is usually possible (18 patients out of 19), although complementary feeds may be required. We strongly suggest that all functioning breast tissue that remains after reduction mammaplasty be left attached to the nipple in a physiological manner to allow subsequent breastfeeding. 相似文献
994.
CM Hanes DR Myers CM Russell JT Barenie SM Adair DR Sams FJ Krakowiak 《Canadian Metallurgical Quarterly》1996,18(4):272-276
OBJECTIVE: To observe the features of the changes of color pattern electroretinogram (CP-ERG) in early primary open-angle glaucoma (POAG). METHOD: The detection and analyses of CP-ERGs in 29 patients (48 eyes) with POAG, 10 patients (16 eyes) with ocular hypertension and 33 age-matched normal volunteers (48 eyes) were made. RESULTS: The changes of CP-ERG in early POAG included reduction of amplitudes of P1 and N2 waves, prolongation of the peak times of red/black N2 and blue/black P1 waves. Part of the patients with ocular hypertension had the amplitude of N2 wave reduced. Five factors including the amplitude of blue/black N2 wave, the amplitudes of red/black P1 and N2 waves, the peak time of red/black N2 wave and the white/black P1 to N2 wave amplitude ratio from CP-ERG which are significantly correlated to the diagnosis of early POAG were selected by the multiple factor stepwise discriminatory analysis, and the stepwise discriminatory function was set up. CONCLUSIONS: CP-ERG is a useful method in detecting the retinal functions in early POAG, and is helpful to its early diagnosis. 相似文献
995.
996.
A 31% incidence of focal posterior knee pain was noted in our initial experience with all-inside meniscal repair using the absorbable Meniscal Arrow system (Bioscience, Tampere, Finland). The pain was transient, resolved by 6 months in all cases, and was unrelated to the length of implant. A typical case is presented to assist surgeons in counseling patients who experience transient posterior knee pain after meniscal repair with this system. 相似文献
997.
PN Lara DR Gandara GT Wurz D Lau M Uhrich C Turrell J Raschko MJ Edelman T Synold J Doroshow F Muggia EA Perez M DeGregorio 《Canadian Metallurgical Quarterly》1998,42(6):504-508
OBJECTIVE: To determine changes in the incidence of candidemia in a neonatal intensive care unit (NICU) during a 15-year period (1981 to 1995) and to compare the prevalence and case fatality rates of Candida albicans and Candida parapsilosis infections. METHODS: A retrospective study was conducted of candidemia occurring in infants in a NICU between January 1, 1981, and December 31, 1995. Cases were identified through computerized searching of a microbiology blood culture database. Candidemia was considered contributory to mortality if death occurred within 3 days of positive blood cultures or if there was autopsy evidence of disseminated candidiasis. RESULTS: One hundred eleven cases of candidemia occurred in 107 infants, representing 1% of all NICU patients during the study period. The rate of candidemia in the NICU increased from 2.5 cases per 1000 admissions in 1981 to 1985, to 4.6 per 1000 admissions in 1986 to 1990 and to 28.5 per 1000 in 1991 to 1995 (P = 0.001). C. albicans was the predominant cause of candidemia between 1981 and 1990. C. parapsilosis was the most prevalent species between 1991 and 1995, causing 53 of 89 cases (60%). The mortality from C. albicans, 13 of 50 cases (26%), was significantly higher than the mortality from C. parapsilosis, 2 of 54 (4%) (P = 0.002; relative risk, 7; 95% confidence interval, 1.7 to 30). CONCLUSIONS: The rate of candidemia in our neonatal intensive care unit increased >11-fold in the 15 years from 1981 to 1995; the prevalent Candida species shifted from C. albicans to C. parapsilosis; and candidemia associated with C. albicans has significantly higher mortality than with C. parapsilosis. 相似文献
998.
DR McEwen 《Canadian Metallurgical Quarterly》1994,59(1):225-32; quiz 235-7, 239-40
Long-term hemodialysis remains the most important support for patients with ESRD, and reliable vascular access is an essential component of this management plan. Recent refinements in AV fistula surgical techniques have produced this dependable, well-tolerated, long-term access route for hemodialysis. 相似文献
999.
DR Franken HS Bastiaan A Kidson P Wranz UF Habenicht 《Canadian Metallurgical Quarterly》1997,29(6):311-317
PURPOSE: The Octopus program Octosmart is able to classify visual fields into six classes. In the program a horizontal bar indicates these classes, and an indicator points to the most probable position, related to the measured pathology. The width of this dashed indicator shows the range of possible fluctuations in the measurement and, therefore, its precision. This study sets out to analyse the suitability of this display mode using other visual-field index data. METHODS: The visual fields of 83 glaucomatous eyes of 61 patients of various etiological groups and glaucoma suspects were studied for periods varying from 1 to 5 years in a retrospective study. All examinations were performed with the G1 Octopus program and analyzed with the Octosmart program. The statistical significance of linear trends of the visual-field indices, mean defect (MD) and corrected loss variance (CLV), and the class shown by the indicator (POI = position of indicator) were determined, and their regression coefficients were analyzed by means of a linear trend test as a function of time. RESULTS: Of the sample of 83 tested eyes, a total of 18 significant trends were recorded after five examinations. All visual-field indices showed a trend towards amelioration. CONCLUSIONS: The 18 significant trends observed must be attributed to perturbing long-term fluctuations and, despite their statistical significance, are of little clinical value. It is questionable whether an increased number of examinations per eye would have attenuated the threshold fluctuations sufficiently to make the change in field class more reliable. 相似文献
1000.
JH Palma DR Almeida AC Carvalho JC Andrade E Buffolo 《Canadian Metallurgical Quarterly》1997,63(4):1081-1084
BACKGROUND: The surgical treatment of acute complicated type B aortic dissection continues to be a challenge and is still associated with high morbidity and mortality rates. METHODS: Seventy consecutive patients with an acute type B aortic dissection underwent an elephant trunk procedure through a median sternotomy during deep hypothermic circulatory arrest. An endoprosthesis that was 22 to 24 mm in diameter was inserted through an incision in the arch and held in place with only proximal sutures. RESULTS: The mean arrest time was 31.4 +/- 8.7 minutes, and it was possible to adequately position the endoluminal graft in every patient. The procedure was done in association with other procedures in 13 patients. There were six in-hospital deaths not related to the endoprosthesis, and four late deaths. Late reoperation was necessary in 6 patients to manage leakage at the proximal suture line. CONCLUSIONS: The insertion of an endoprosthesis through the arch for the management of a complicated acute type B dissection has several advantages over the conventional thoracotomy approach. The hospital mortality rate in this series of 70 patients was 20%, and the actuarial 5-year survival rate was 62.5%. We consider the elephant trunk procedure the treatment of choice in patients with type B acute dissections, regardless of whether the dissection is complicated or not. 相似文献