全文获取类型
收费全文 | 514篇 |
免费 | 15篇 |
专业分类
电工技术 | 11篇 |
化学工业 | 89篇 |
金属工艺 | 17篇 |
机械仪表 | 18篇 |
建筑科学 | 11篇 |
矿业工程 | 1篇 |
能源动力 | 11篇 |
轻工业 | 76篇 |
水利工程 | 1篇 |
无线电 | 39篇 |
一般工业技术 | 94篇 |
冶金工业 | 116篇 |
原子能技术 | 3篇 |
自动化技术 | 42篇 |
出版年
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 18篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 21篇 |
2006年 | 9篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 20篇 |
1998年 | 31篇 |
1997年 | 20篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1972年 | 3篇 |
1966年 | 3篇 |
1943年 | 3篇 |
1941年 | 5篇 |
1940年 | 9篇 |
1939年 | 13篇 |
1938年 | 4篇 |
排序方式: 共有529条查询结果,搜索用时 15 毫秒
51.
This paper reflects on existing caching concepts in proxies and stubs of component technologies and lines out their advantages and deficiencies. A new concept is introduced that averts proliferation of component stubs on client side while transparently providing efficient caching of attributes that doesn't require any changes to existing code at all. Common object-oriented design facilities and code generation tools are leveraged to support seamless integration of these caching concepts into the development cycle. 相似文献
52.
C.J. Strauss P.W.J. van Wyk E.J. Lodolo P.J. Botes C.H. Pohl S. Nigam J.L.F. Kock 《Journal of the Institute of Brewing》2007,113(1):42-47
Mitochondrial function is generally accepted as important for expression of yeast flocculation. In this study, a correlation between mitochondrial activity and flocculation is demonstrated using the XTT reduction assay. The mitochondrial activity of strongly flocculent cells was higher than those of weakly flocculent cells and cells cultivated in the presence of acetylsalicylic acid. Furthermore, we show the first oxylipin‐containing flocculation binding sites on yeast cell surfaces using scanning electron microscopy. We propose that in addition to zymolectin‐mediated flocculation, oxylipin interactions may also play a role in yeast flocculation. 相似文献
53.
54.
Breast-feeding exposure of infants to cadmium, lead, and mercury: a public health viewpoint 总被引:2,自引:0,他引:2
The purpose of this report is to provide an overview of the public health implications of exposure via breast milk to cadmium, lead, and mercury for nursing infants and to provide health-based guidance. Daily intakes were calculated and compared with guidance values used for public health assessments at hazardous waste sites. Cadmium, lead, and mercury under normal conditions are found in breast milk at concentration ranges of < 1 microgram/L, 2-5 micrograms/L, and 1.4-1.7 micrograms/L, respectively. Women exposed environmentally or occupationally can have higher levels in their breast milk. Concentrations of about 5 micrograms/L (cadmium), 20 micrograms/L (lead), and 3.5 micrograms/L (mercury) appear to be adequate screening levels. Many factors affect both the distribution of cadmium, lead, and mercury in breast milk and the health consequences to an infant. It is not clear what additional impact low-level exposure via breast milk may have on an infant born with a body burden to one of these metals. There is sufficient evidence to make the case that contaminated breast milk is a source of potential risk to infants in certain populations. Prevention strategies that include behavior modification and proper nutrition should be communicated to women at risk. Identification and elimination of exposure pathways and a critical analysis of the benefits of breast feeding versus heavy metal exposure are needed on a site-specific or individual basis. Research is required to better understand the impact of low-level exposure to heavy metals via breast milk. Breastfeeding should be encouraged under most circumstances. 相似文献
55.
The diphtheria toxin repressor (DtxR) from Corynebacterium diphtheriae is a divalent-metal activated repressor of chromosomal genes responsible for siderophore-mediated iron-uptake and of a gene on several corynebacteriophages that encodes diphtheria toxin. Even though DtxR is the best characterized iron-dependent repressor to date, numerous key properties of the protein still remain to be explained. One is the role of the cation-anion pair discovered in its first metal-binding site. A second is the reason why zinc exhibits its activating effect only at a concentration 100-fold higher than other divalent cations. In the presently reported 1.85 A resolution Co-DtxR structure at 100K, the sulfate anion in the cation-anion-binding site interacts with three side chains that are all conserved in the entire DtxR family, which points to a possible physiological role of the anion. A comparison of the 1.85 A Cobalt-DtxR structure at 100K and the 2.4 A Zinc-DtxR structure at room temperature revealed no significant differences. Hence, the difference in efficiency of Co2+ and Zn2+ to activate DtxR remains a mystery and might be hidden in the properties of the intriguing second metal-binding site. Our studies do, however, provide a high resolution view of the cationanion-binding site that has most likely evolved to interact not only with a cation but also with the anion in a very precise manner. 相似文献
56.
Matthias Jarke Manfred A. Jeusfeld Peter Peters Klaus Pohl 《Data & Knowledge Engineering》1997,23(3):247-268
As organizations move from hierarchical towards market-like structures, their distributed units also take a larger role in the design and evolution of organizational information systems. This requires strategies which support the cooperative creation, evaluation and evolution of global information flow structures among autonomous organizational units through local knowledge acquisition and maintenance. Three such strategies are presented: cooperative conceptual modeling, multi-simulation, and explicit process support. These strategies are formally embedded in a meta modeling framework and implemented with a repository-based architecture. They are intended for the analysis of business processes in networked organizations, and as a basis for designing and evolving their federated information systems. 相似文献
57.
58.
OBJECTIVE: Our goal was to determine how often a transvaginal sacrospinous colpopexy procedure can be done bilaterally. STUDY DESIGN: Between August 1993 and July 1996, 66 patients were prospectively evaluated for uterine prolapse (19 patients) and posthysterectomy vaginal vault prolapse (47 patients). Twenty-six patients (25 with posthysterectomy vaginal vault prolapse) underwent an abdominal sacral colpopexy. The remaining 40 patients (18 with uterine prolapse, 22 with posthysterectomy vaginal vault prolapse) were preoperatively and intraoperatively assessed for a bilateral sacrospinous colpopexy. All patients with uterine prolapse underwent hysterectomy. RESULTS: In 10 of the 18 (56%) patients with uterine prolapse and in 16 of the 22 (73%) patients with posthysterectomy vaginal vault prolapse, bilateral suspension to the sacrospinous ligament was carried out. Follow-up has ranged from 6 to 40 months, and no recurrent vaginal cuff prolapses have been detected in any patients. In 3 patients, however, all in the bilateral fixation categories, distention cystoceles have developed; one patient has undergone a successful anterior colporrhaphy. CONCLUSIONS: The bilateral suspension is different from the unilateral suspension in that the former requires significant intraoperative judgment in its feasibility and in maintaining the width of the vaginal cuff to allow a bilateral suspension without tension. A bilateral fixation appears more attainable in a patient with posthysterectomy vaginal vault prolapse than in one with uterine prolapse. 相似文献
59.
Jeffrey R. Olson Henry E. Fischer Robert O. Pohl 《Journal of the American Ceramic Society》1991,74(3):564-568
A magnesium aluminosilicate glass-ceramic (Corning Code 9606) has been heat-treated at 900°, 1010°, 1200°, and 1260°C for up to 90 min., and the effect on the thermal conductivity between 30 and 300 K has been studied. It has been shown that the large increase of the thermal conductivity which results from the ceramming occurs predominantly when crystalline cordierite forms. At 1260°C, heat treatment for only 20 min leads to a thermal conductivity identical to that measured for commercial 9606, which has been cerammed for 8 h at the same temperature. This observation provides further evidence for the usefulness of commercial 9606 as a thermal conductivity standard. Measurements of the specific heats of Code 9606 before and after ceramming have been reviewed and have been found to be close to that of crystalline SiO2 above ∼ 30 K, regardless of the state of ceramming. A review has also been made of thermal conductivity and specific heat of several ZrTiO4 nucleated lithium aluminosilicate glass-ceramics at various states of ceramming. The thermal conductivity of these glass-ceramics seems to be sufficiently independent of chemical composition as well as of the degree of crystallization to warrant a recommended curve for this class of glass-ceramics. 相似文献
60.