全文获取类型
收费全文 | 2694篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 7篇 |
金属工艺 | 1篇 |
建筑科学 | 1篇 |
轻工业 | 5篇 |
水利工程 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 30篇 |
冶金工业 | 2627篇 |
自动化技术 | 8篇 |
出版年
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 5篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 76篇 |
1998年 | 879篇 |
1997年 | 503篇 |
1996年 | 258篇 |
1995年 | 167篇 |
1994年 | 155篇 |
1993年 | 166篇 |
1992年 | 10篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 33篇 |
1988年 | 32篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 16篇 |
1980年 | 23篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 55篇 |
1976年 | 138篇 |
1975年 | 2篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有2696条查询结果,搜索用时 10 毫秒
91.
92.
SB Christensen A Guider CJ Forster JG Gleason PE Bender JM Karpinski WE DeWolf MS Barnette DC Underwood DE Griswold LB Cieslinski M Burman S Bochnowicz RR Osborn CD Manning M Grous LM Hillegas JO Bartus MD Ryan DS Eggleston RC Haltiwanger TJ Torphy 《Canadian Metallurgical Quarterly》1998,41(6):821-835
Evaluation of a variety of PDE4 inhibitors in a series of cellular and in vivo assays suggested a strategy to improve the therapeutic index of PDE4 inhibitors by increasing their selectivity for the ability to inhibit PDE4 catalytic activity versus the ability to compete for high affinity [3H]rolipram-binding sites in the central nervous system. Use of this strategy led ultimately to the identification of cis-4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexane-1-carboxyl ic acid (1, SB 207499, Ariflo), a potent second-generation inhibitor of PDE4 with a decreased potential for side effects versus the archetypic first generation inhibitor, (R)-rolipram. 相似文献
93.
M Krause KA Beauchemin LM Rode BI Farr P N?rgaard 《Canadian Metallurgical Quarterly》1998,76(11):2912-2920
We conducted a study to determine the effects of treating barley grain with a fibrolytic enzyme mixture on chewing activities, ruminal fermentation, and total tract digestibility in cattle. We also investigated the potential benefits of using barley straw rather than barley silage as a roughage source in high-grain diets for feedlot cattle. Steers were given ad libitum access to one of four diets that consisted of 95% barley-based concentrate and 5% forage (DM basis). The concentrate was either control or enzyme-treated, and the forage was either barley silage or barley straw. Applying the enzyme mixture onto the barley lowered the concentrations of dietary ADF and NDF. However, it is not certain when this fiber hydrolysis occurred relative to feed consumption because the fiber analyses were conducted after the study was completed. Enzyme treatment of barley increased total tract dietary ADF digestibility by 28% (P<.05). Acetate-to-propionate ratio tended to decrease, which suggests that enzymes may have increased ruminal starch digestion as a result of enhanced digestion of barley hulls. Replacing silage with straw increased ADF intake (P<.05) and resulted in 1-h/d increase in rumination time (P<.05). Even though there was no effect of diet on ruminal pH, replacing silage with straw increased ruminal acetate, as a percentage of total VFA, and total tract ADF digestion (P<.01). This study demonstrates that using a fibrolytic enzyme mixture in high-grain diets that contain mainly barley grain can improve fiber digestion and grain utilization, but the mode of action is unclear. Straw can be used rather than silage to increase the effective fiber content of a high-grain feedlot diet. 相似文献
94.
95.
Idiopathic thrombocytopenic purpura (ITP, also known as immune thrombocytopenic purpura) in adults is principally a disease of young women. Although in some patients the onset is acute and complete resolution occurs, in most patients, the onset is insidious and the course is chronic. In spite of the relative frequency of ITP, there are important unresolved issues in its diagnosis and management. For this reason, the American Society of Hematology (ASH) chose ITP as the disease topic for its initial sponsored practice guideline in 1993. A major conclusion of the published guideline was the lack of firm evidence on which to base diagnostic procedures and management strategies. This review describes the clinical features of ITP in adults, emphasizes the principal unresolved issues in diagnosis and management, and outlines the critical areas for future research. 相似文献
96.
Prevention of T cell anergy by signaling through the gamma c chain of the IL-2 receptor 总被引:1,自引:0,他引:1
VA Boussiotis DL Barber T Nakarai GJ Freeman JG Gribben GM Bernstein AD D'Andrea J Ritz LM Nadler 《Canadian Metallurgical Quarterly》1994,266(5187):1039-1042
When stimulated through their antigen receptor without requisite costimulation, T cells enter a state of antigen-specific unresponsiveness termed anergy. In this study, signaling through the common gamma chain of the interleukin-2 (IL-2), IL-4, and IL-7 receptors in the presence of antigen was found to be sufficient to prevent the induction of anergy. After culture with IL-2, IL-4, or IL-7, Jak3 kinase was tyrosine-phosphorylated, which correlated with the prevention of anergy. Therefore, a signal through the common gamma chain may regulate the decision of T cells to either clonally expand or enter a state of anergy. 相似文献
97.
98.
LM Benson 《Canadian Metallurgical Quarterly》1998,18(5):92-93
Thirty-eight patients diagnosed as having continuous schizophrenia progrediens, 35 patients with shift-like schizophrenia and six patients with hypertoxic (feverish) schizophrenia were studied. The examinees displayed a marked increase in the blood content of lipid peroxidation products, such as malonic dialdehyde and conjugated dienes, together with an enhancement of the degree of erytrocytolysis, which events are particularly noticeable in hypertoxic- and continuous schizophrenia. Blood catalase activity gets higher, that of superoxide dismutase is on the decrease, which facts suggest to us some faults in the system of antioxidant defence. 相似文献
99.
Isolated reaction centers (RCs) from Rhodobacter sphaeroides were found to bind Zn(II) stoichiometrically and reversibly in addition to the 1 equiv of non-heme Fe(II). Metal and EPR analyses confirm that Zn(II) is ligated to a binding site that is distinct from the Fe site. When Zn(II) is bound to this site, electron transfer between the quinones QA and QB (QA-QB --> QAQB-) is slowed and the room-temperature kinetics become distributed across the microsecond to millisecond time domain. This effect of metal binding on the kinetics is similar to the more global effect of cooling RCs to 2 degreesC in the absence of Zn(II). This suggests that Zn(II) binding alters localized protein motions that are necessary for rapid QA-QB --> QAQB- electron transfer. Inspection of the RC crystal structure suggests a cluster of histidine ligands located beneath the QB binding pocket as a potential binding site. 相似文献
100.