全文获取类型
收费全文 | 1613篇 |
免费 | 2篇 |
专业分类
化学工业 | 8篇 |
金属工艺 | 1篇 |
机械仪表 | 2篇 |
建筑科学 | 4篇 |
轻工业 | 5篇 |
水利工程 | 1篇 |
一般工业技术 | 4篇 |
冶金工业 | 1588篇 |
自动化技术 | 2篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2014年 | 2篇 |
2011年 | 3篇 |
2008年 | 2篇 |
2006年 | 2篇 |
2004年 | 2篇 |
2003年 | 6篇 |
1999年 | 41篇 |
1998年 | 464篇 |
1997年 | 273篇 |
1996年 | 190篇 |
1995年 | 109篇 |
1994年 | 79篇 |
1993年 | 87篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 29篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1982年 | 6篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 45篇 |
1976年 | 104篇 |
1975年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有1615条查询结果,搜索用时 0 毫秒
991.
KA McLean AB Lawrence JC Petherick L Deans J Chirnside A Vaughan BL Nielsen R Webb 《Canadian Metallurgical Quarterly》1998,50(1-2):95-109
The involvement of cAMP-dependent phosphorylation sites in establishing the basal activity of cardiac L-type Ca2+ channels was studied in HEK 293 cells transiently cotransfected with mutants of the human cardiac alpha1 and accessory subunits. Systematic individual or combined elimination of high consensus protein kinase A (PKA) sites, by serine to alanine substitutions at the amino and carboxyl termini of the alpha1 subunit, resulted in Ca2+ channel currents indistinguishable from those of wild type channels. Dihydropyridine (DHP)-binding characteristics were also unaltered. To explore the possible involvement of nonconsensus sites, deletion mutants were used. Carboxyl-terminal truncations of the alpha1 subunit distal to residue 1597 resulted in increased channel expression and current amplitudes. Modulation of PKA activity in cells transfected with the wild type channel or any of the mutants did not alter Ca2+ channel functions suggesting that cardiac Ca2+ channels expressed in these cells behave, in terms of lack of PKA control, like Ca2+ channels of smooth muscle cells. 相似文献
992.
SM Kornblau M Andreeff SX Hu HJ Xu S Patel A Theriault C Koller H Kantarjian E Estey AB Deisseroth WF Benedict 《Canadian Metallurgical Quarterly》1998,4(8):1955-1963
A prior retrospective study suggested that the level of retinoblastoma protein (RB) expression was prognostic for survival in acute myelogenous leukemia (AML). Individuals with no/low RB protein expression were considered to have loss of RB function, and those with maximally phosphorylated (maxphos) RB were also felt to have nonfunctional RB. To confirm this, we prospectively investigated whether the level of RB expression was prognostic in AML in a larger cohort of patients. RB level was measured by Western blot and immunohistochemical analysis on peripheral blood samples from 210 newly diagnosed AML patients. Patients were divided into three groups based on the level of RB protein expression (i.e., no or low, elevated, and maxphos) or into two groups on the basis of presumed RB function, altered function (AF-RB, low and maxphos RB), versus normal function (NF-RB, elevated RB). By combined results of Western blot and immunohistochemical analysis, 20%, 65%, and 15% of patients had low, elevated, and maxphos RB, respectively. Most patients with acute promyelocytic leukemia (APL) with a French-American-British classification of M3 were in the low RB group, likely reflecting a lower proliferative rate of promyelocytes. Analysis was performed with and without these APL patients. The median survival was significantly shorter for both patients with low RB expression (48 weeks, P = 0.05, including APL patients; 34 weeks, corrected P = 0.008, with APL patients excluded) and maxphos RB expression (51 weeks, P = 0.007) compared to those with elevated RB expression (122 weeks including and 98 weeks excluding APL patients). Differences were greatest among patients with nonfavorable prognosis cytogenetics (median survival, 34 weeks versus 85 weeks; corrected P = 0.001 for AF-RB versus NF-RB). Remission duration was also significantly shorter for non-APL patients with AF-RB versus NF-RB (median survival, 36 weeks versus not reached; corrected P = 0.02). In multivariate analyses, including cytogenetics, performance status, age, antecedent hematological disorder, and RB status, with and without APL patients included, no/low and maxphos-RB protein expression were independent predictors for poorer survival. This prospective study confirms that the level of expression of RB is a strong prognostic factor in AML, with an inferior survival experience being associated with no/low RB and maxphos RB expression. Therefore, therapeutic decisions based on the level of RB expression may be indicated, and protocols to incorporate this are currently under development. 相似文献
993.
AB Niculescu X Chen M Smeets L Hengst C Prives SI Reed 《Canadian Metallurgical Quarterly》1998,18(1):629-643
It has been proposed that the functions of the cyclin-dependent kinase inhibitors p21(Cip1/Waf1) and p27Kip1 are limited to cell cycle control at the G1/S-phase transition and in the maintenance of cellular quiescence. To test the validity of this hypothesis, p21 was expressed in a diverse panel of cell lines, thus isolating the effects of p21 activity from the pleiotropic effects of upstream signaling pathways that normally induce p21 expression. The data show that at physiological levels of accumulation, p21, in addition to its role in negatively regulating the G1/S transition, contributes to regulation of the G2/M transition. Both G1- and G2-arrested cells were observed in all cell types, with different preponderances. Preponderant G1 arrest in response to p21 expression correlated with the presence of functional pRb. G2 arrest was more prominent in pRb-negative cells. The arrest distribution did not correlate with the p53 status, and proliferating-cell nuclear antigen (PCNA) binding activity of p21 did not appear to be involved, since p27, which lacks a PCNA binding domain, produced similar arrest distributions [corrected], DNA endoreduplication occurred in pRb-negative but not in pRb-positive cells, suggesting that functional pRb is necessary to prevent DNA replication in p21 G2-arrested cells. These results suggest that the primary target of the Cip/Kip family of inhibitors leading to efficient G1 arrest as well as to blockade of DNA replication from either G1 or G2 phase is the pRb regulatory system. Finally, the tendency of Rb-negative cells to undergo endoreduplication cycles when p21 is expressed may have negative implications in the therapy of Rb-negative cancers with genotoxic agents that activate the p53/p21 pathway. 相似文献
994.
For the first time sirdalud was used in the treatment of 32 patients with chronic form of tension-type headache. The preparation was applied during 14 days (4 or 6 mg daily). Positive effect was observed in 75% of patients (a decrease of both headache and tension of pericranial muscles). However, sirdalud was so effective neither in patients with pronounced depression nor in ones without pericranial muscular tension. The drug had a number of psychotropic effects: it decreased anxious-depressive manifestations, normalized night sleep, significantly increased the thresholds of both ache and nociceptive flexor reflex. 相似文献
995.
W Zhang SM Kornblau T Kobayashi A Gambel D Claxton AB Deisseroth 《Canadian Metallurgical Quarterly》1995,1(9):1051-1057
The WAF1/Cip1 gene product is an important regulator at the G1 checkpoint in the cell cycle. WAF1/Cip1 expression can be activated through p53-dependent and p53-independent pathways. The WAF1/Cip1 protein binds to cyclin-dependent kinase complexes and inhibits the kinase activity that is required for cell cycle progression. In this preliminary study, we analyzed with Western blot assays the steady-state levels of the WAF1/Cip1 protein in the leukemia cells of 100 untreated acute myelogenous leukemia (AML) patients. Normal bone marrow cells from six donors were used as a control. The results of these analyses showed that the levels of the WAF1/Cip1 protein were very low in normal marrow cells and in the leukemia cells of 83 AML patients. High levels of WAF1/Cip1 were detected in 17 patients; these patients with high WAF1/Cip1 levels were significantly less likely to achieve complete remission (41% versus 69%, P = 0.03) and were four times as likely to be resistant to therapy (47% versus 12%, P = 0.003) as patients with very low levels of WAF1/Cip1. Median survival was 38 weeks for patients having very low expression levels versus 11 weeks for patients having high expression levels (P = 0.04). The WAF1/Cip1 level was an independent predictor for response but not survival in a stepwise multivariate regression analysis. Southern blotting analyses did not detect deletion of the WAF1/Cip1 gene in the 12 negative WAF1/Cip1 AML samples tested. Also, the level of WAF1/Cip1 protein expression was not correlated with overexpression of cyclin D1, cyclin E, proliferating cell nuclear antigen, cyclin-dependent kinase 4, or p53 in the leukemia cells. However, the levels of cyclin D1, cyclin E, and cyclin-dependent kinase 4 were elevated in most of the AML samples compared with that in normal marrow. We hypothesize that high-level constitutively expressed WAF1/Cip1 in tumor cells may result in an indolent state that is refractory to chemotherapy drugs. We conclude that the WAF1/Cip1 expression level may be an important prognostic factor for response to therapy and survival in AML patients. 相似文献
996.
EP Van Etten T van Popta PA Van Luyt PJ Bode AB Van Vugt 《Canadian Metallurgical Quarterly》1995,2(4):196-200
From January 1986 to January 1995, 99 consecutive cases with a ruptured spleen were analysed retrospectively. Diagnostic peritoneal lavage was replaced by abdominal ultrasound as a routine screening investigation in blunt abdominal trauma after 1991. An abdominal computed tomography scan carried out in stable circulatory conditions provided additional information in 80% of the cases. The choice of treatment was related to the extent of the splenic damage and associated injuries. Even in degree IV ruptures splenorrhaphy was carried out successfully in 38% (five out of 12). The Hospital Trauma Index-Injury Severity Score (HTI-ISS) was significantly lower (17.7; n = 43) in conservative treatment than in cases treated by splenorrhaphy (27.6; n = 25) or splenectomy (33.6; n = 31). Conservative treatment (n = 43) resulted in a secondary intervention in 19%, whereas primary splenorrhaphy (n = 25) failed once (4%). Clinical morbidity was 26%, with no significant differences between conservative treatment, splenorrhaphy and splenectomy. Early mortality (0-30 days post-trauma) reached 14%, and was related to extensive injuries in all cases. The mean HTI-ISS in patients with a fatal outcome was 50.5. Overall, 62% of the injured spleens were saved, with the rate of splenic preservation improving throughout the study period. A conservative policy was increasingly treatment of first choice in patients with stable circulatory parameters with major concomitant injuries. 相似文献
997.
CJ Damien JR Parsons AB Prewett F Huismans EC Shors RE Holmes 《Canadian Metallurgical Quarterly》1995,9(3):275-288
Coralline hydroxyapatite (cHA) is an osteoconductive material currently being used as a bone graft substitute. Created by the hydrothermal conversion of the calcium carbonate skeleton of coral to hydroxyapatite, this material has a porous structure similar to cancellous bone. Addition of demineralized bone matrix (DBM) would conceivably create a composite with both osteoconductive and osteoinductive properties. This pilot study evaluated the healing of rabbit cranial defects that had been filled with cHA or cHA augmented with a DBM gel formed by adding glycerol to the DBM particulate. Data from these were then compared to unfilled defects from a previous study. Results indicated enhancement of new bone formation and an increase in the rate of healing in the defects filled with the cHA-DBM gel composite. Further studies are warranted. 相似文献
998.
Glomerular hyperplasia and thickening of the glomerular basement membrane increase with age in humans and animals. This glomerulopathy can be enhanced by hyperglycemic conditions such as diabetes mellitus. When diabetic guinea pigs were examined by fluorescent microscopy, deposits of a substance similar to immunoglobulin G (IgG) were seen. Comparison with nondiabetic age-matched control animals suggest that glomerulopathy is related to aging, and can be further enhanced by hyperglycemia. 相似文献
999.
1000.
AB Burkashov TD Bol'shakova VA Siluianova VN Khomiakova VG Borisov 《Canadian Metallurgical Quarterly》1981,27(2):21-26
The total and aerobic productivity, the content of the thyroid hormones, thyrotropin, lactate, and acid-base balance in the blood of 52 highly skilled sportsmen were studied in the process of veloergometric exercises of different intensity. It was shown that thyroxin and thyrotropin content increased and triiodothyronine concentration decreased in the blood plasma under the action of veloergometric exercises. A rise in cell metabolism and changes in the internal medium of the organism influence the alteration of the blood thyroid hormone and thyrotropin levels. Thyroid and hypophyseal thyrotropic functions depend to a certain degree on the exercise intensity and functional preparedness of the sportsmen. 相似文献