全文获取类型
收费全文 | 3969篇 |
免费 | 3篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 44篇 |
金属工艺 | 1篇 |
机械仪表 | 2篇 |
建筑科学 | 6篇 |
能源动力 | 2篇 |
轻工业 | 33篇 |
水利工程 | 3篇 |
无线电 | 5篇 |
一般工业技术 | 11篇 |
冶金工业 | 3848篇 |
自动化技术 | 16篇 |
出版年
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 13篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 141篇 |
1998年 | 1263篇 |
1997年 | 787篇 |
1996年 | 483篇 |
1995年 | 237篇 |
1994年 | 218篇 |
1993年 | 225篇 |
1992年 | 23篇 |
1991年 | 31篇 |
1990年 | 37篇 |
1989年 | 47篇 |
1988年 | 33篇 |
1987年 | 27篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 64篇 |
1976年 | 137篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有3972条查询结果,搜索用时 15 毫秒
991.
SM Riordan CJ McIver D Wakefield VM Duncombe TD Bolin MC Thomas 《Canadian Metallurgical Quarterly》1997,92(8):1335-1338
Unknown proteins isolated from mutant tissues of rice (Oryza sativa L.) recovered from inhibitor selections were subsequently peptide microsequenced. Database searches putatively identified one peptide as fructose 1,6-bisphosphate aldolase (EC 4.1.2.13). Tissues of mutant rice, PI564784, and wild type (cv Calrose 76) tissues were evaluated for aldolase activity. Total enzyme activities were slightly lower in the mutant than the control but the differences were not significant. Although the mutant phenotype is for enhanced lysine and protein, we ascribe the small aldolase differences to physiological adjustments, rather than to DNA modifications of the aldolase gene(s). Homologies of rice peptides with aldolases from a range of species, as well as rice cell culture expressed sequence tags (ESTs) are presented. Some amino acids sequences are highly conserved. The mutant phenotype expressing stress proteins is not likely to be defined by a change in rice aldolases. 相似文献
992.
993.
G Lizard MC Chignol P Roignot C Souchier Y Chardonnet D Schmitt 《Canadian Metallurgical Quarterly》1997,29(7):545-554
Human papillomavirus (HPV) infection with potentially oncogenic types 16 or 18 is common in genital lesions especially in uterine carcinomas. In such lesions, in situ hybridization with non-radioactive probes is a powerful tool for the histopathologist to detect and type HPV DNA either on cell deposits or on tissue sections. The use of an immunohistochemical method involving alkaline phosphatase and Fast Red TR salt/naphthol AS-MX phosphate is proposed for use with conventional bright-field or fluorescence microscopy as well as by laser scanning confocal microscopy. The alkaline phosphatase-Fast Red reaction has the advantage of producing a red precipitate that permits the detection of in situ hybridization signals by bright-field microscopy, and of obtaining a strong red fluorescence characterized by a lack of bleaching when excited by a green light. Therefore, the alkaline phosphatase-Fast Red reaction is well adapted for observations by fluorescence and confocal microscopy, the latter method allowing the detection, in tissue sections of cervical intraepithelial lesions, of small punctate and large diffuse hybridization signals, considered as integrated and episomal states of HPV DNA respectively. The combination of in situ hybridization with the alkaline phosphatase-Fast Red reaction and confocal microscopy is particularly convincing when hybridization signals are of small size and/or of low fluorescence intensity, especially if they are present in various focal planes; in such conditions, infected cells are easily detected by three-dimensional reconstruction. Therefore, this combination is a suitable method for identifying and characterizing HPV DNA in cells and tissue sections. 相似文献
994.
995.
FA Sastre-Janer J Regis P Belin JF Mangin D Dormont MC Masure P Remy V Frouin Y Samson 《Canadian Metallurgical Quarterly》1998,8(7):641-647
OBJECTIVE: To examine the impact of ethnic group on aspects of weight concern and to assess the role of family values in explaining this association. SUBJECTS AND MEASURES: 20 Asian and 20 white daughters gave a questionnaire to their mother, father and sibling closest in age, concerning their profile characteristics (age, education) values and beliefs and completed a matched questionnaire containing additional measures of aspects of their weight concern. RESULTS: The results showed no differences between the white and Asian daughters in terms of either their restrained eating or body dissatisfaction. However, the results showed consistent differences between the members of the two family groups in terms of the value placed on achievement, child/parent relationships, competition, the role of women, and some differences in terms of materialism, the value of appearance and their idea of the perfect female body. The results were then analysed to assess the best predictors of the daughter's weight concern. Whereas restrained eating was related to the mother's rating of the value of physical appearance and the sibling's ratings of competitiveness and a non-traditional role for women (40% of the variance), the results showed that body dissatisfaction was related to the daughter's rating of materialism, having a father who preferred a thinner female body, the siblings ratings of a non-traditional role for women, degree of concordance within the family concerning the value of competitiveness and the educational level of the 'head of the family' (49% of variance). CONCLUSION: Whereas a dichotomous model of ethnicity may be insufficient to explain differences in aspects of weight concern, an expanded model of cultural beliefs may be a more powerful construct. Accordingly, the absence or presence of differences in weight concern according to ethnic group may simply reflect the extent to which the different groups chosen for analysis are differentiated by these predictive values. 相似文献
996.
In the chronically denervated muscles of patients with prior paralytic poliomyelitis, there are secondary myopathic features, including endomysial inflammation and rare vacuolated fibers. To assess the frequency and characteristics of the vacuoles and their similarities with those seen in inclusion body myositis (IBM), we examined 58 muscle biopsy specimens from patients with prior paralytic poliomyelitis for (1) the presence of rimmed vacuoles; (2) acid-phosphatase reactivity; (3) Congo-red-positive amyloid deposits; (4) electron microscopy, searching for tubulofilaments; and (5) immunoelectron microscopy, using antibodies against beta-amyloid and ubiquitin. We found vacuolated muscle fibers in 18 of 58 (31%) biopsies, with a mean frequency of 2.06 +/- 0.42 fibers per specimen. The vacuoles contained acid phosphatase-positive material in 6 of the 18 (33.30%) specimens and stained positive for Congo red in five (27.80%). By immunoelectron microscopy, the vacuoles contained 5.17 +/- 0.13 nm fibrils and 14.9 +/- 0.31 nm filaments that immunoreacted with antibodies to beta-amyloid and ubiquitin in a pattern identical to the one seen in IBM. We conclude that vacuolated muscle fibers containing filamentous inclusions positive for amyloid and ubiquitin are not unique to IBM and the other vacuolar myopathies but can also occur in a chronic neurogenic condition, such as postpoliomyelitis. The chronicity of the underlying disease, rather than the cause, may lead to vacuolar formation, amyloid deposition, and accumulation of ubiquitinated filaments. 相似文献
997.
PURPOSE: To determine whether patients with early-stage bilateral breast cancer can be treated with definitive irradiation following breast-conserving surgery with acceptable survival, local control, complications, and cosmesis. METHODS AND MATERIALS: During the period 1977-1992, 55 women with Stage 0, I, or II concurrent (n = 12) or sequential (n = 43) bilateral breast cancer were treated with definitive irradiation following breast-conserving surgery. The records of these 55 patients with 110 treated breasts were reviewed for tumor size, histology, pathologic axillary lymph node status, first and overall site(s) of failure, and adjuvant chemotherapy or hormonal therapy. Curves for survival, local control, and regional control were determined. Cosmetic outcome, complication rates, and matching technique were analyzed. The median total radiation dose delivered was 64 Gy (range 42-72) using tangential whole-breast irradiation followed by an electron or iridium implant boost. The tangential fields were matched with no overlap in 40 patients (73%); there was overlap on skin of up to 4 cm in 14 patients (25%); and the matching technique was unknown in 1 patient (2%). The median follow-up for the 12 women with concurrent bilateral breast cancer was 4.0 years. The median follow-up for the other 43 women with sequential cancer was 9.3 and 4.9 years, respectively, after the first and second cancers. RESULTS: For the overall group of 55 patients, the 5- and 10-year overall survival rates were 96% and 94%, respectively, after treatment of the first cancer, and 96% and 92%, respectively, after treatment of the second cancer. The 5- and 10-year actuarial relapse-free survival rates were 90% and 75%, respectively, after treatment of the first cancer, and 83% and 72%, respectively, after treatment of the second cancer. For the 110 treated breast cancers, the 5- and 10-year actuarial local failure rates were 5% and 15%, respectively. Complication rates were: 28% breast edema, 8% arm edema, 4% pneumonitis, 3% cellulitis, 1% rib fracture, and 1% brachial plexopathy; no patient developed matchline fibrosis. For patients with a minimum of 3 years of relapse-free follow-up, the rate of excellent or good cosmetic outcome for 104 treated breasts was 85%. CONCLUSION: Definitive irradiation after breast-conserving surgery is technically feasible for selected patients with concurrent or sequential early-stage bilateral breast cancer. Survival, local control, complication rates, and cosmetic outcomes appear comparable to historical reports of breast conservation treatment for unilateral disease. Bilateral definitive breast irradiation after breast-conservation surgery should be considered an acceptable alternative treatment to bilateral mastectomy for selected patients with concurrent or sequential early-stage bilateral breast cancer. 相似文献
998.
MW Cho MK Lee MC Carney JF Berson RW Doms MA Martin 《Canadian Metallurgical Quarterly》1998,72(3):2509-2515
The chemokine receptors CCR5 and CXCR4, in combination with CD4, mediate cellular entry of macrophage-tropic (M-tropic) and T-cell-tropic strains of human immunodeficiency virus type 1 (HIV-1), respectively, while dualtropic viruses can use either receptor. We have constructed a panel of chimeric viruses and envelope glycoproteins in which various domains of the dualtropic HIV-1(DH12) gp160 were introduced into the genetic background of an M-tropic HIV-1 isolate, HIV-1(AD8). These constructs were employed in cell fusion and virus infectivity assays using peripheral blood mononuclear cells, MT4 T cells, primary monocyte-derived macrophages, or HOS-CD4 cell lines, expressing various chemokine receptors, to assess the contributions of different gp120 subdomains in coreceptor usage and cellular tropism. As expected, the dualtropic HIV-1(DH12) gp120 utilized either CCR3, CCR5, or CXCR4, whereas HIV-1(AD8) gp120 was able to use only CCR3 or CCR5. We found that either the V1/V2 or the V3 region of HIV-1(DH12) gp120 individually conferred on HIV-1(AD8) the ability to use CXCR4, while the combination of both the V1/V2 and V3 regions increased the efficiency of CXCR4 use. In addition, while the V4 or the V5 region of HIV-1(DH12) gp120 failed to confer the capacity to utilize CXCR4 on HIV-1(AD8), these regions were required in conjunction with regions V1 to V3 of HIV-1(DH12) gp120 for efficient utilization of CXCR4. Comparison of virus infectivity analyses with various cell types and cell fusion assays revealed assay-dependent discrepancies and indicated that events occurring at the cell surface during infection are complex and cannot always be predicted by any one assay. 相似文献
999.
JC Lambert J Pérez-Tur MJ Dupire D Galasko D Mann P Amouyel J Hardy A Delacourte MC Chartier-Harlin 《Canadian Metallurgical Quarterly》1997,6(12):2151-2154
The APOE epsilon4 allele is a strong genetic susceptibility factor for Alzheimer's disease. Interaction with other biological factors may modulate the effect of the apoE isoforms. However, previous work suggested that other genetic variability within the APOE locus, influencing the effect of the epsilon4 allele, may exist. Such variability could modify the expression of the APOE gene and, in particular, the level of expression of APOE alleles could be an important determinant of disease pathogenesis. To test this hypothesis we examined the levels of expression of APOE in heterozygotes with AD and in controls, using a new method of semi-quantitation. We report that relative epsilon4 mRNA expression is increased in AD compared with controls and suggest that genetic variability in the neural expression of APOE contributes to disease risk. 相似文献
1000.
GV Carbonell AF Alfieri AA Alfieri MC Vidotto CE Levy AL Darini RM Yanaguita 《Canadian Metallurgical Quarterly》1997,30(11):1291-1298
Cytotoxin production was studied in 60 Serratia marcescens strains isolated from hospitalized patients. Association of cytotoxic activity with serotype, source of isolation and presence of plasmids was also evaluated. Thirteen of the 60 S. marcescens strains produced a cytotoxic effect on Vero cells. These strains were isolated from distinct clinical sources and classified into seven different serotypes (O1:H7; O4:NM; O10:NT; O19:NM; O6,14:H4; O6,14:NM and O6,14:H1). No relationship was observed between cytotoxic activity and clinical source or serotypes of the strains. Plasmids from five cytotoxin-producing S. marcescens strains were transferred to E. coli K12/711. The transconjugants did not exhibit cytotoxicity, indicating that the cytotoxic effect is not plasmid-mediated among these strains. Although a cytotoxic activity was demonstrated in filtrates of some S. marcescens strains, further studies should be performed to assess the role of this toxin in pathogenesis. 相似文献