全文获取类型
收费全文 | 576篇 |
免费 | 2篇 |
专业分类
化学工业 | 10篇 |
轻工业 | 8篇 |
无线电 | 8篇 |
一般工业技术 | 7篇 |
冶金工业 | 543篇 |
自动化技术 | 2篇 |
出版年
2020年 | 5篇 |
2018年 | 3篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2006年 | 2篇 |
2004年 | 2篇 |
2001年 | 1篇 |
1999年 | 13篇 |
1998年 | 192篇 |
1997年 | 92篇 |
1996年 | 54篇 |
1995年 | 34篇 |
1994年 | 36篇 |
1993年 | 28篇 |
1992年 | 2篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 14篇 |
1976年 | 44篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有578条查询结果,搜索用时 12 毫秒
11.
G Illuminati FG Calio A Bertagni V Martinelli 《Canadian Metallurgical Quarterly》1998,383(3-4):259-264
Two month-old Wistar male albino rats were exposed during a 30-day period to a daily oral intake ad libitum of either 200 microg/mL Cd (as CdCl2), 0.1 microg/mL Se (as Na-selenite), or the same dosages of Cd + Se in drinking water. The daily intake from the water was calculated to be 15 mg Cd/kg and 7 microg Se/kg. Cadmium (Cd) accumulates in the heart (p < 0.005) and, in rats, decreases both body mass growth (p < 0.005) and heart mass (p < 0.02). Selenium (Se) significantly decreases the negative effect of Cd on body mass growth. In the hearts of Cd-treated rats, cadmium caused the decrease (p < 0.05) of selenium-dependent glutathione peroxidase (GSH-Px, EC 1.11.1.9) activity. At the same time, the activities of total superoxide dismutase (total SOD, EC 1.15.1.1), manganese-containing superoxide dismutase (Mn SOD), and copper-zinc-containing superoxide dismutase (CuZn SOD) were increased (p < 0.005). The activities of total SOD, CuZn SOD (p < 0.005), GSH-Px (p < 0.02), and glutathione-S-transferase (GST, p < 0.005) were increased in the hearts of Se-treated rats. However, by concomitant administration of Cd and Se, these changes were diminished (total SOD, GST) or were completely eliminated (Mn SOD, GSH-Px). These results indicate that Se only partly diminishes the effects of Cd cardiotoxicity. 相似文献
12.
KN Prasad E Carvalho J Edwards-Prasad FG La Rosa S Kumar JH Kim A Meyers S Kentroti 《Canadian Metallurgical Quarterly》1994,(5):312-320
This study reports the establishment of alpha-amylase-producing human parotid pleomorphic adenoma cell lines (2HP and 2HP1) which have been maintained in culture for over 1 yr. The procedures required preparation of cellular clumps from tumor tissue and plating them on plasma clot or precoated dishes. During the initial phase of growth they required modified MCDB-153 medium without serum. When cells showed signs of degeneration they were changed to MCDB-153 medium containing first 2% and then 10% heat inactivated fetal bovine serum. Although cells grew well in MCDB-153 containing 10% serum, the epithelial cell morphology was not distinct. Therefore, the growth and morphology of cells grown in MCDB-10% serum were compared with those in RPMI growth medium containing 10% fetal bovine serum and F12 containing 10% agammaglobulin newborn bovine serum. Although the growth of cells was a little slower in F12 medium than those in MCDB and RPMI, the epithelial cell morphology was maintained better than in other growth media. The cells of 2HP and 2HP1 produce low levels of alpha-amylase and relatively high levels of alpha-amylase mRNAs of 1176 and 702 bp and contain neurofilament-160, a neuronal-specific marker. The cells of 2HP1 are tumorigenic when tested in athymic mice, but the cells of 2HP are not. The establishment of amylase-producing human parotid adenoma cell lines of different characteristics in culture provides a new opportunity to study the mechanisms of differentiation and transformation, and regulation of alpha-amylase in these cells. 相似文献
13.
14.
QY Yao DS Croom-Carter RJ Tierney G Habeshaw JT Wilde FG Hill C Conlon AB Rickinson 《Canadian Metallurgical Quarterly》1998,72(5):4352-4363
In apparent contrast to earlier work on Epstein-Barr virus (EBV) carriage in the general Caucasian population, in vitro virus isolations from human immunodeficiency virus (HIV)-positive male homosexual cohorts have shown frequent examples of multiple EBV infection and an overall prevalence of type 2 EBV strains exceeding 30%. Here we ask to what extent these findings might hold true in another T-cell-immunocompromised cohort, HIV-positive hemophilic patients. Resident EBV strains were rescued within lymphoblastoid cell lines derived from the blood and throat washings of 39 such individuals, using the same in vitro protocols of virus isolation as for the homosexual cohort. A mean of 19 independent cell lines was made per patient, and in each case the resident virus was characterized by PCR-based viral genomic analysis and by immunoblotting to reveal the viral "EBNAprint." By these criteria a significant proportion (14 of 39) of the hemophilic cohort carried more than one EBV strain, suggesting that T-cell impairment does indeed sensitize virus carriers to reinfection with new strains of exogenously transmitted virus. However, the overall incidence of type 2 EBV infection was 10%, which is close to that observed in the earlier work with healthy carriers and substantially lower than that seen in HIV-positive homosexuals. We infer that type 2 EBV is relatively rare in the general Caucasian population but has become endemic in the homosexual community. 相似文献
15.
16.
D Zhang I Botos FX Gomis-Rüth R Doll C Blood FG Njoroge JW Fox W Bode EF Meyer 《Canadian Metallurgical Quarterly》1994,91(18):8447-8451
The structure of the metalloproteinase and hemorrhagic toxin atrolysin C form d (EC 3.4.24.42), from the venom of the western diamondback rattlesnake Crotalus atrox, has been determined to atomic resolution by x-ray crystallographic methods. This study illuminates the nature of inhibitor binding with natural (< Glu-Asn-Trp, where < Glu is pyroglutamic acid) and synthetic (SCH 47890) ligands. The primary specificity pocket is exceptionally deep; the nature of inhibitor and productive substrate binding is discussed. Insights gained from the study of these complexes facilitate the design of potential drugs to treat diseases where matrix metalloproteinases have been implicated, e.g., arthritis and tumor metastasis. 相似文献
17.
BJ Conway OH Suleiman FG Rueter RG Antonsen RJ Slayton 《Canadian Metallurgical Quarterly》1994,191(2):323-330
PURPOSE: To determine trends in mammography in the United States. MATERIALS AND METHODS: A sample of mammographic facilities was selected for each year of the Nationwide Evaluation of X-ray Trends. The same protocol was followed for the 1985, 1988, and 1992 surveys. Data were collected with use of the same imaging phantom for all three surveys and also with a different phantom in the 1988 and 1992 surveys. RESULTS: Of the 356 facilities surveyed in 1992, 59% claimed to be in compliance with the Health Care Financing Administration (HCFA) mammography requirements, 42% were accredited by the American College of Radiology (ACR), and 23% did not hold credentials from either the HCFA or the ACR. Since 1985, there has been a 34% improvement in acceptable phantom image quality score and a 20% decrease in the mean glandular dose. CONCLUSION: Mammography as practiced today is essentially a screen-film technique. Mammographic phantom image quality has improved considerably. The overall mean glandular dose has decreased primarily because of the elimination of xeroradiography. 相似文献
18.
A van der Lugt EJ Gussenhoven G Pasterkamp T Stijnen JA Reekers FG van den Berg AV Tielbeek JL Seelen H Pieterman 《Canadian Metallurgical Quarterly》1998,16(2):110-119
The skepticism surrounding the potential benefits of resistance exercise training prevalent just decades ago has evolved over the years to an understanding of the integral nature muscular overload plays in the training programs for athletes. The science of training elite athletes is progressing rapidly, as insights into the physiological adaptations resulting from varying program configurations become available. Resistance training impacts several body systems, including muscular, endocrine, skeletal, metabolic, immune, neural, and respiratory. An understanding and appreciation of basic scientific principles related to resistance training is necessary in order to optimize training responses. Careful selection of the acute program variables in a workout to simulate sports-specific movements is required for optimal transfer of gains made in training to competition. Thus, whether athletes require predominantly eccentric, isometric, slow-velocity, or high-velocity strength or power in their athletic event will dictate the time commitment to each component and form the basis for designing individual workouts. Program variation over a training period is essential to maximize gains and prevent overtraining. 相似文献
19.
L Lu W Li F Fu FG Chambers S Qian JJ Fung AW Thomson 《Canadian Metallurgical Quarterly》1997,64(12):1808-1815
BACKGROUND: Failure of costimulatory molecule-deficient donor dendritic cells (DCs) to induce indefinite allograft acceptance may be a result of the 'late" up-regulation of these molecules on the DCs after interaction with host T cells. Ligation of CD40 on antigen-presenting cells by its cognate ligand CD40L is thought to induce expression of CD80 (B7-1) and CD86 (B7-2). We examined the influence of anti-CD40L monoclonal antibody (mAb) on the capacity of donor-derived DC progenitors to induce long-term allograft survival. METHODS: High purity DC progenitors were grown from B10 (H2b) mouse bone marrow in granulocyte-macrophage colony-stimulating factor and transforming growth factor beta1 (TGFbeta1). Mature DC were propagated in granulocyte-macrophage colony-stimulating factor and interleukin-4. Their phenotype was characterized by flow cytometric analysis and their function by mixed leukocyte reactivity. Anti-donor cytotoxic T lymphocyte activity in grafts and spleens of vascularized heart allograft recipients was also assessed. RESULTS: The TGFbeta3-cultured cells were (1) DEC 205-positive, MHC class II-positive, CD80dim, CD86dim, and CD40dim, (2) poor stimulators of naive allogeneic T-cell proliferation, and (3) able to prolong significantly B10 cardiac allograft survival in C3H (H2k) recipients when given (2 x 10[6] i.v.) 7 days before organ transplantation (median survival time [MST] 26 days vs. 12 days in controls, and 5 days in interleukin-4 DC-treated animals). Their allostimulatory activity was further diminished by addition of anti-CD40L mAb at the start of the mixed leukocyte cultures. Anti-CD40L mAb alone (250 microg/mouse, i.p.; day -7) did not prolong cardiac graft survival (MST 12 days). In contrast, TGFbeta-cultured DCs + anti-CD40L mAb extended graft survival to a MST of 77 days, and inhibited substantially the anti-donor cytotoxic T lymphocyte activity of graft-infiltrating cells and host spleen cells assessed 8 days after transplant. CONCLUSIONS: The CD40-CD40L pathway appears important in regulation of allogeneic DC-T-cell functional interaction in vivo; its blockade increases markedly the potential of costimulatory molecule-deficient DCs of donor origin to induce long-lasting allograft survival. 相似文献
20.
Suying Xu Adam C. Sedgwick Souad A. Elfeky Wenbo Chen Ashley S. Jones George T. Williams A. Toby A. Jenkins Steven D. Bull John S. Fossey Tony D. James 《Frontiers of Chemical Science and Engineering》2020,14(1):112
A boronic acid-based anthracene fluorescent probe was functionalised with an acrylamide unit to incorporate into a hydrogel system for monosaccharide detection. In solution, the fluorescent probe displayed a strong fluorescence turn-on response upon exposure to fructose, and an expected trend in apparent binding constants, as judged by a fluorescence response where D-fructose>D-galactose>D-mannose>D-glucose. The hydrogel incorporating the boronic acid monomer demonstrated the ability to detect monosaccharides by fluorescence with the same overall trend as the monomer in solution with the addition of D-fructose resulting in a 10-fold enhancement (≤0.25 mol/L). 相似文献