首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   459篇
  免费   0篇
电工技术   6篇
综合类   1篇
化学工业   28篇
金属工艺   6篇
机械仪表   6篇
建筑科学   224篇
能源动力   6篇
轻工业   9篇
水利工程   16篇
无线电   60篇
一般工业技术   13篇
冶金工业   43篇
原子能技术   4篇
自动化技术   37篇
  2023年   3篇
  2022年   2篇
  2021年   10篇
  2020年   1篇
  2019年   3篇
  2018年   1篇
  2016年   3篇
  2015年   2篇
  2014年   4篇
  2013年   6篇
  2012年   7篇
  2011年   10篇
  2010年   48篇
  2009年   67篇
  2008年   82篇
  2007年   66篇
  2006年   6篇
  2005年   6篇
  2004年   5篇
  2003年   4篇
  2002年   6篇
  2001年   8篇
  2000年   6篇
  1999年   6篇
  1998年   20篇
  1997年   13篇
  1996年   12篇
  1995年   5篇
  1994年   7篇
  1993年   7篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1987年   1篇
  1986年   2篇
  1985年   2篇
  1982年   8篇
  1981年   3篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   3篇
  1976年   2篇
  1975年   1篇
  1971年   1篇
排序方式: 共有459条查询结果,搜索用时 0 毫秒
101.
The effect of beta-carotene on the susceptibility of low density lipoprotein (LDL) to oxidative modification was investigated in a double-blind, randomized placebo-controlled study. Hypercholesterolaemic, postmenopausal women were given 30 mg beta-carotene per day (n = 15 subjects) or placebo capsules (n = 15 subjects) for 10 weeks. They were instructed to follow the American Heart Association Step One diet. LDL, isolated before and after treatment was subjected to copper-catalysed lipid peroxidation. There were no significant differences between LDL from the beta-carotene and placebo groups, as assessed by measuring the lag time for formation of conjugated dienes; the rate of formation and the amount of conjugated dienes formed; the amount of lipid peroxides generated; and the relative electrophoretic mobility, at baseline and after treatment. Dietary records showed that the subjects were consuming similar amounts and types of fat. No significant differences were found in the lipid composition and fatty acid pattern of LDL from the two groups. In conclusion, the results indicated that supplementation with beta-carotene in non-smoking, hypercholesterolaemic, postmenopausal women had no protective effect on the susceptibility of LDL to copper-catalysed modification in vitro.  相似文献   
102.
103.
104.
There are an ample number of commercial testing kits available for mycotoxin analysis on the market today, including enzyme-linked immunosorbent assays, membrane-based immunoassays, fluorescence polarisation immunoassays and fluorometric assays. It can be observed from the literature that not only are developments and improvements ongoing for these assays but there are also novel assays being developed using biosensor technology. This review focuses on both the currently available methods and recent innovative methods for mycotoxin testing. Furthermore, it highlights trends that are influencing assay developments such as multiplexing capabilities and rapid on-site analysis, indicating the possible detection methods that will shape the future market.  相似文献   
105.
überschaubare kurzfristige Verz?gerungen, die der Sph?re des Werkbesteller zuzurechnen sind, gleichviel ob sie von ihm angeordneten Leistungs?nderungen oder der z?gerlichen Erfüllung von dessen Mitwirkungspflichten entspringen, verl?ngern die vertraglich festgelegten Fertigstellungsfristen entsprechend; die Vertragsstrafe sichert dann die Einhaltung der so modifizierten (verl?ngerten) Ausführungsfristen. überschreiten indes die aus der Sph?re des Werkbestellers herrührenden Verz?gerungen das in erster Linie am Umfang der zu erbringenden Werkleistungen und an der wirtschaftlichen Leistungskraft des Werkunternehmers abzulesende zeitliche Ma? des üblichen, auf das sich jeder Werkunternehmer einzustellen hat, wird also der Zeitplan "über den Haufen geworfen", dann gibt es keine verbindliche Fertigstellungsfrist mehr und die Strafabrede geht ins Leere, selbst wenn der Unternehmer zur Leistung in angemessener Frist verhalten bleibt und insofern auch in Verzug geraten kann. Wird das zeitliche Ma? des üblichen überschritten, kann nur ein tats?chlich eingetretener Verz?gerungsschaden geltend gemacht werden.  相似文献   
106.
Liegen die Umst?nde, die zu Mehraufwendungen führen, tats?chlich in der Sph?re des Bestellers (hier: Mehrerfordernis an Verputzarbeiten durch Wegfall von Holz- bzw Blechfassadenteilen), dann ist selbst bei einem "garantierten" Kostenvorschlag die unverzügliche Rüge einer unvermeidlichen betr?chtlichen überschreitung zur Wahrung des Anspruches des Werkunternehmers auf die Mehrkosten entbehrlich.  相似文献   
107.
运用有限元软件ABAQUS建立钢包包衬的线性弹性模型,模拟钢包预热过程包衬的热应力,分析包衬厚度及其材料物理性能对包衬内最大热应力和钢壳表面温度的影响;采用偏最小二乘法建立包衬厚度及材料物理性能与包衬内最大热应力、钢壳表面温度间的预报模型。结果表明,工作衬材料物理性能对包衬最大应力和钢壳表面温度起主要影响作用;较之于无绝热衬,有绝热衬钢包永久衬材料物理性能对钢包热应力和钢壳表面温度的影响作用显著降低。  相似文献   
108.
The application of heat storage systems in households or the industry is one possibility to optimize the degree of heat utilization and to reduce greenhouse gas emissions. In contrast to established heat storage systems based on water, zeolitic systems reach energy densities of 150–200 kWh m−3 and allow for seasonal storage with almost no heat loss. However, a commercial breakthrough was not yet successful. Given this background, it is the aim of the present study to identify appropriate operational parameters for a zeolite heat storage system in the laboratory and to prepare an upscaling to demonstration scale. To this end, the pressure drop of the zeolite bed, the cycle time, and the optimal process parameters during thermal loading and deloading were determined.  相似文献   
109.
Immunohistochemical expression of the tumour associated mucin-type glycoprotein A-80 was investigated in a series of 173 breast cancer patients with a clinical follow-up between 13 and 19 years. A routine immunoperoxidase technique was used in formalin-fixed, paraffin-embedded surgical tumour specimens. One hundred and fifty of 173 tumours (87%) immunostained with MAb A-80. The degree of A-80 immunoreactivity was related to the tumour grade but not to lymph node status, tumour size, or nuclear DNA distribution pattern. In univariate analysis the degree of A-80 expression was found to be of significant prognostic value both in node negative and in node positive breast cancer patients (P = 0.03). Patients with non-A-80 immunoreactive tumours had significant longer distant metastases-free survival times and fewer relapses than women with carcinomas composed of A-80 immunoreactive tumour cells. This prognostic value was reduced in a multivariate analysis, including lymph node status, tumour size, and nuclear DNA distribution pattern, but retained borderline significance (P = 0.08). In conclusion, the findings of this study indicate that expression of the mucin-type glycoprotein A-80 as determined by immunohistochemistry seems to be related to clinical outcome in breast cancer patients.  相似文献   
110.
Cost analysis for thoracoscopy: thoracoscopic wedge resection   总被引:1,自引:0,他引:1  
Video-assisted thoracic surgery (VATS) procedures are now being performed with increasing frequency. The instrumentation and video equipment continue to evolve and much of this new technology is expensive. We reviewed our experience with VATS in our most recent 150 cases for the purpose of cost analysis. The costs incurred in patients undergoing VATS wedge resection for nodules (n = 45) were compared with those in similar patients having wedge resection using open techniques (n = 31). We found that patients who undergo open resections were more likely to spend time in the intensive care unit after surgery. The anesthesia costs were similar in the two groups. Disposable instrument costs were $623 higher for VATS resection; however, the operative time was shorter (101.4 minutes for VATS versus 122.5 minutes for the open procedure), making the total operating room costs comparable. The length of hospital stay was shorter after VATS resection (4.4 days for VATS versus 6.5 days for the open procedure), resulting in lower total hospital charges in the VATS group; however, this difference was not statistically significant. The cost of a VATS wedge resection for removing peripheral nodules is competitive with that of open techniques. Additional benefits, such as reduced pain, shorter operating times, and decreased hospital stays, make thoracoscopy a valuable diagnostic tool. The length of hospital stay, operating room time, disposable instrument costs, complications, and patient acuity all have an impact on the total costs and vary for different procedures. The operative time has shortened and the use of disposable instrumentation has lessened as our experience with thoracoscopy has increased.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号