全文获取类型
收费全文 | 1311篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 35篇 |
化学工业 | 80篇 |
金属工艺 | 11篇 |
机械仪表 | 6篇 |
建筑科学 | 24篇 |
能源动力 | 5篇 |
轻工业 | 40篇 |
水利工程 | 1篇 |
无线电 | 35篇 |
一般工业技术 | 83篇 |
冶金工业 | 971篇 |
自动化技术 | 39篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 16篇 |
2009年 | 15篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 23篇 |
1999年 | 38篇 |
1998年 | 331篇 |
1997年 | 175篇 |
1996年 | 115篇 |
1995年 | 53篇 |
1994年 | 52篇 |
1993年 | 55篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 13篇 |
1978年 | 5篇 |
1977年 | 26篇 |
1976年 | 65篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1969年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有1330条查询结果,搜索用时 15 毫秒
61.
RA Blackwood AT Transue DM Harsh RC Brower SJ Zacharek JE Smolen RJ Hessler 《Canadian Metallurgical Quarterly》1996,59(5):663-670
Neutrophil stimulation results in the activation of a variety of phospholipases, including phospholipase A2 (PLA2), which releases arachidonic acid from the 2 position of membrane phospholipids, leaving a lysophospholipid. Because arachidonic acid is known to be a potent fusogen in vitro, we examined the effect of metabolism by PLA2 on the fusion of complex liposomes (liposomes prepared with a phospholipid composition similar to that found in neutrophil plasma membrane). We observed that PLA2 augmented the fusion of complex liposomes with each other as well as with specific granules isolated from human neutrophils, lowering the Ca2+ requirement for fusion by three orders of magnitude. Furthermore, although lysophospholipids inhibited fusion, the incorporation of arachidonic acid into liposome membranes overcame the inhibitory effects of the lysophospholipids. Thus with PLA2 and annexins we were able to obtain fusion of complex liposomes at concentrations of Ca2+ that are close to physiological. Our data suggest that the activation of PLA2 and the generation of arachidonic acid may be the major fusion-promoting event mediating neutrophil degranulation. 相似文献
62.
S Remadi K Burkhardt AT Straccia G Pizzolato W Mac Gee 《Canadian Metallurgical Quarterly》1998,194(5):371-374
OBJECTIVE: Oesophageal self-expanding metal endoprostheses (SEMS, or stents) are recognized as a safe means of palliating dysphagia caused by malignancy. Stent designs that have covered or uncovered walls are now available. The purpose of this study was to compare the outcome of use of these two designs. DESIGN: Thirty consecutive cases were reviewed. All the patients had been referred over a period of 25 months for palliation of dysphagia caused by malignant obstruction. Either a covered or an uncovered stent was placed in each patient. Palliation of dysphagia, 30 day mortality, mean survival time, and the number of endoscopic re-interventions required, were assessed. RESULTS: Uncovered Ultraflex stents were used in 14 patients, and Schneider Wallstents were used in 16 patients. Dysphagia improved by one grade or more in 69% of patients. The 30 day mortality was 27%, with an overall mean survival time of 99 days. There was no significant difference between the two groups for these three parameters. Ten patients needed a total of 28 repeat endoscopic procedures to maintain stent patency, with overall rates for each group of 1.64 procedures per patient, for uncovered stents, compared with 0.31 for covered stents (significant at the P < 0.05 level). The number of repeat procedures increased with survival time. CONCLUSION: The use of covered self-expanding metal oesophageal endoprostheses is associated with a significant reduction in the need for endoscopic reintervention after stent placement. 相似文献
63.
B Nicol DG Lambert DJ Rowbotham E Okuda-Ashitaka S Ito D Smart AT McKnight 《Canadian Metallurgical Quarterly》1998,356(2-3):R1-R3
We have examined the effects of the recently described heptadecapeptide nocistatin on K+-evoked glutamate release from rat cerebrocortical slices in vitro. In vivo, nocistatin reverses the action of nociceptin. Nocistatin (100 nM, n = 7) did not inhibit K+-evoked glutamate release alone. Nociceptin (100 nM) inhibited glutamate release by 51.7 +/- 8.3% (P < 0.05, n = 6) and this was fully reversed by nocistatin (100 nM). Nocistatin also appears to be an antagonist of nociceptin action in vitro. 相似文献
64.
J Kelly R Wolin M Connolly A Afonso L James P Kirshmeier WR Bishop AT McPhail 《Canadian Metallurgical Quarterly》1998,6(6):673-686
Blocking farnesylation of oncogenic Ras proteins is a mechanism based therapeutic approach that is of current interest for the development of antitumor agents to treat ras associated tumors. As part of a SAR study on the lead farnesyl protein transferase (FPT) inhibitor I, we report here the synthesis of novel geometric isomers II and III and the FPT inhibition activity of their N-acyl and N-sulfonamido derivatives 15-65. The N-acyl derivatives are markedly less active than the lead inhibitor I thereby demonstrating that the spatial location of the N-acyl group in I is critical for binding of the compound to FPT. In contrast to I, the N-sulfonamido-II series is a novel lead of non-sulfhydryl, nonpeptidic compounds that are dual FPT/GGPT inhibitors. In light of recent reports on the alternative prenylation of N- and K-Ras, dual FPT/GGPT inhibitors may be required to control cell proliferation in tumors containing activated Ras. 相似文献
65.
66.
67.
68.
In lexically based studies, we derived Filipino personality dimensions and related them to the Big Five model. In Study 1, Filipino high-school and college students (N = 629) rated themselves on a near-comprehensive list of 861 Filipino (Tagalog) trait adjectives. In Study 2, Filipino high-school and college students (N = 1,531) rated 280 markers of dimensions identified in Study 1. Some students (n = 473) also completed the NEO Five-Factor Inventory. Seven comparable Filipino dimensions were identified in factor analyses in the two studies. We concluded that the dimensions we labeled Concern for Others (vs. Egotism), Conscientiousness, Gregariousness, and Intellect were quite similar to Big Five Agreeableness, Conscientiousness, Extraversion, and Intellect, respectively. The Filipino Self-Assurance dimension was most similar to Big Five Neuroticism. The Filipino Temperamentalness dimension was more complex in Big Five terms, overlapping Agreeableness, Conscientiousness, and Neuroticism. A final Filipino factor resembled a Negative Valence or Infrequency dimension. More than five factors had to be extracted to obtain Philippine dimensions resembling all of the Big Five. 相似文献
69.
The model proposed in this paper presents a broad range of factors to predict individual human work output. The predictors include aerobic capacity, body size, motivation, work pattern, social environment and social network, caloric intake, drug and alcohol use, stress resistance and thermoregulation. Health is a major intervening variable, and its relationship to work output is a special concern of this research. We suggest that this model may be used as a template to explain human productivity in most societies. Its universality can be subjected to rigorous testing in a range of settings from tropical upland swidden horticulturalists to urban workers in a northern industrialized country. Observations are offered on some of those testing sites and on methodological issues implicit in research of this breadth. A major pilot study of urban Chinese workers has already demonstrated the predictive power of the model in one setting. 相似文献
70.