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   1060篇
  免费   6篇
电工技术   26篇
化学工业   14篇
金属工艺   22篇
机械仪表   6篇
建筑科学   29篇
矿业工程   2篇
能源动力   19篇
轻工业   58篇
石油天然气   2篇
无线电   59篇
一般工业技术   33篇
冶金工业   745篇
原子能技术   5篇
自动化技术   46篇
  2023年   3篇
  2022年   3篇
  2021年   3篇
  2020年   2篇
  2019年   2篇
  2018年   5篇
  2017年   4篇
  2016年   3篇
  2015年   2篇
  2014年   11篇
  2013年   18篇
  2012年   10篇
  2011年   17篇
  2010年   12篇
  2009年   13篇
  2008年   7篇
  2007年   12篇
  2006年   13篇
  2005年   12篇
  2004年   17篇
  2003年   10篇
  2002年   10篇
  2001年   9篇
  2000年   5篇
  1999年   29篇
  1998年   220篇
  1997年   135篇
  1996年   84篇
  1995年   53篇
  1994年   38篇
  1993年   48篇
  1992年   12篇
  1991年   13篇
  1990年   18篇
  1989年   26篇
  1988年   18篇
  1987年   18篇
  1986年   9篇
  1985年   13篇
  1984年   5篇
  1983年   7篇
  1982年   9篇
  1981年   9篇
  1980年   7篇
  1978年   2篇
  1977年   34篇
  1976年   44篇
  1975年   2篇
  1969年   2篇
  1955年   3篇
排序方式: 共有1066条查询结果,搜索用时 15 毫秒
1.
A phase III clinical trial was designed to determine if more intensive induction and consolidation therapy for acute myeloblastic leukemia increases the remission rate and prolongs survival. A minor objective was to determine if the use of non-cross resistant drugs was more effective than the same drugs used for induction. Patients with untreated leukemia between the ages of 15 and 50 were given daunorubicin 45 mg/m2 for the first 3 days of a 10-day continuous infusion of cytosine arabinoside, initially at a dose of 2000 mg/m2 but reduced to 100 mg/m2 because of toxicity. Those under 36 achieving a complete remission and with an histocompatible donor were assigned to a transplant arm. The rest were randomized to receive one of three consolidation arms: A, cytosine arabinoside, 200 mg/m2 daily for 7 days and daunorubicin 45 mg/m2 daily for 3 days for three courses; B, one course as in Arm A followed by amsacrine, 120 mg/m2 daily for 5 days followed by a 5-day continuous infusion of azacytidine, 150 mg/m2/day; C, thioguanine and cytosine arabinoside, 100 mg/m2 every 12 h and daunorubicin 10 mg/m2 daily for 5 days for three courses followed by four maintenance courses of cytosine arabinoside, 100 mg/m2 daily for 5 days and daunorubicin, 45 mg/m2 for 2 days every 13 weeks. From 1981 to 1986, 398 eligible patients were enrolled and 219 achieved a complete remission. The initial induction dose of cytosine arabinoside was reduced after five of 29 patients exhibited fatal gastrointestinal toxicity. Only 11 patients were assigned to the transplant arm. There were no significant differences in the consolidation arms. The 5 year disease-free survivals were 38, 31 and 27% in arms A, B, and C respectively. Intensive consolidation therapy with the same or different drugs used in induction was as effective as lower dose consolidation followed by maintenance therapy.  相似文献   
2.
3.
Global competition, commitment to the Kyoto Protocol and a deregulated, integrated European electricity market will in all probability increase the demand for energy efficiency on the part of companies in Sweden. Investment decisions are an important part of meeting the new demands, because they decide the future efficiency of industrial energy systems. The objective of this study is to investigate, from a managerial perspective, the need to improve decision support in some industries, which can help to facilitate and improve investment decisions concerning energy efficiency. This work has been conducted through in-depth interviews with representatives for a number of energy-intensive companies and non-energy-intensive companies from different sectors. One need that was identified was the improvement of working methods in order to support the decision-making process. Here, external players seem to be playing an increasingly important role. Access to correct information, better follow-up activities, and transparent, understandable calculations are also considered to be important. The study will form the foundation for subsequent work on decision support and energy efficiency in industry.  相似文献   
4.
Southern blot analysis was performed with a panel of DNA probes to detect rearrangements of c-myc, bcl-1, bcl-2 and bcl-3 in 14 cases of B-cell non-Hodgkin's lymphoma (NHL) with a clonal cytogenetic rearrangement involving the chromosome 14q32 locus and no known donor chromosome [t(14;?)(q32;?)]. In our experience, 21% of all chromosomal abnormalities involving the 14q32 locus in B-cell NHL are of this type. We found oncogene rearrangements in five of the 14 cases: bcl-1 rearrangement on one mantle zone lymphoma, bcl-2 rearrangements in two follicular lymphomas, and c-myc rearrangements in two small noncleaved cell lymphomas. We conclude that a 14q32+ abnormality of unknown origin is a relatively frequent karyotypic finding in B-cell NHL. In one third of the cases, known oncogenes that have been previously described in reciprocal translocations involving the immunoglobulin heavy chain locus were shown to be involved in the 14q32+ abnormality. The translocations in the other cases are likely to have involved one of the above oncogenes with breakpoints not revealed by the probes employed, other known oncogenes, or oncogenes that have not yet been identified.  相似文献   
5.
A method for simultaneously engineering multiple properties of a protein, based on the observed additivity of effects of individual mutations, is presented. We show that, for the gene V protein of bacteriophage f1, effects of double mutations on both protein stability and DNA binding affinity are approximately equal to the sums of the effects of the constituent single mutations. This additivity of effects implies that it is possible to deliberately construct mutant proteins optimized for multiple properties by combination of appropriate single mutations chosen from a characterized library.  相似文献   
6.
In the past, electrical heat tracing has been thought of as a minor addition to plant utilities. Today, it is recognized as a critical subsystem to be monitored and controlled. A marriage between process, mechanical, and electrical engineers must take place to ensure that optimum economic results are produced. The Internet, expert systems, and falling costs of instrumentation will all contribute to more reliable control systems and improved monitoring systems. There is a harmonization between Europe and North America that should facilitate design and installation using common components. The future holds many opportunities to optimize the design  相似文献   
7.
8.
The degradation of phytate (inositol hexaphosphate) in rapeseed meal diet not containing phytase activity was studied in 15 growing ileum-fistulated pigs. Stomach and small intestinal degradation and total gastrointestinal degradation were compared. The effect of addition of calcium carbonate to the rapeseed meal diet at two levels (9.2 and 18.5 g/kg diet) was investigated. A commercial barley-wheat-soybean diet with intrinsic phytase activity was used as reference. Phytate and its hydrolysis products in diets, ileal digesta and feces were determined by HPLC ion-pair chromatography. Hydrolysis of phytate in the stomach and small intestine was 35-45% in pigs fed the rapeseed meal diet independent of calcium addition, and 65% in pigs fed the reference diet. Total gastrointestinal degradation of phytate in pigs fed the rapeseed diet was 97, 77 and 42% (P < 0.001) when calcium intakes were 4.5, 9.9 and 15 g/d, respectively; total gastrointestinal degradation was 72% in pigs fed the reference diet. The intestinal phytate degradation pattern, when rapeseed diet was fed, indicated the activity of an unspecific phosphatase, whereas that of the reference diet indicated intrinsic dietary phytase activity. We conclude that dietary supplementation of calcium carbonate decreases the phytate degradation in the colon of pigs, but not in the stomach and small intestine.  相似文献   
9.
10.
Numerous investigators have suggested that cell glycoconjugates are modified by the development of cancer and the progression of this to a malignant form. Accordingly, in the present work, beta-D-galactosidase, alpha-L-fucosidase, beta-N-acetyl-D-glucosaminidase and beta-N-acetyl-D-galactosaminidase activities were studied in human thyroid and gastric tumours. Samples were obtained from human gastric mucosa and thyroid gland tumours together with a part of the surrounding normal tissue (control). Enzyme activity was determined spectrophotometrically based on the release of p-nitrophenol from suitable p-nitrophenyl-derivative substrates. Results showed that beta-D-galactosidase, alpha-L-fucosidase, beta-N-acetyl-D-glucosaminidase and beta-N-acetyl-D-galactosaminidase activities were detected in tumour and control samples from thyroid and gastric tissues. The gastric mucosa also showed alpha-L-mannosidase activity. The specific activities of these glycosidases were higher (two- or three-fold) in tumour tissues as compared with their controls. beta-D-galactosidase, beta-N-acetyl-D-glucosaminidase and beta-N-acetyl-D-galactosaminidase activities from thyroid and gastric tumours showed a significant increase in V(max) as compared with their respective controls (P < 0.05 or P < 0.001). Thyroid alpha-L-fucosidase activity showed a statistically and significantly increased affinity (lower K(m)) in tumour samples as compared to normal tissue. In conclusion both gastric and thyroid tumours showed enhanced glycosidase activity as compared with enzyme activity observed in normal tissue. These results are in agreement with the notion of a markedly raised degradation within lysosomes of tumour cells.  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