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   1663篇
  免费   28篇
  国内免费   3篇
电工技术   7篇
化学工业   87篇
金属工艺   4篇
机械仪表   2篇
建筑科学   29篇
能源动力   6篇
轻工业   30篇
水利工程   3篇
无线电   79篇
一般工业技术   81篇
冶金工业   1335篇
原子能技术   2篇
自动化技术   29篇
  2023年   5篇
  2021年   7篇
  2020年   5篇
  2019年   3篇
  2018年   8篇
  2017年   9篇
  2016年   6篇
  2015年   7篇
  2014年   6篇
  2013年   15篇
  2012年   13篇
  2011年   14篇
  2010年   14篇
  2009年   17篇
  2008年   11篇
  2007年   8篇
  2006年   12篇
  2005年   11篇
  2004年   10篇
  2003年   13篇
  2002年   11篇
  2001年   6篇
  2000年   8篇
  1999年   54篇
  1998年   443篇
  1997年   227篇
  1996年   171篇
  1995年   88篇
  1994年   79篇
  1993年   88篇
  1992年   13篇
  1991年   21篇
  1990年   18篇
  1989年   23篇
  1988年   17篇
  1987年   6篇
  1986年   8篇
  1985年   12篇
  1984年   10篇
  1983年   8篇
  1982年   12篇
  1981年   10篇
  1980年   15篇
  1978年   8篇
  1977年   33篇
  1976年   79篇
  1975年   10篇
  1974年   5篇
  1972年   4篇
  1943年   5篇
排序方式: 共有1694条查询结果,搜索用时 15 毫秒
81.
The concentrations of the soluble adhesion molecules E-cadherin, E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were investigated in 48 patients with colorectal cancer before treatment, and their relation to clinical, histological and routine laboratory parameters was examined. Data were collected on tumour stage at presentation, presence and sites of metastatic disease, tumour pathology and results of routine laboratory tests. Serum concentrations of ICAM-1 and VCAM-1 were significantly elevated in the patients with colorectal cancer in comparison with a group of healthy subjects (P < 0.00001). Levels of circulating ICAM-1 and VCAM-1 were increased both in patients with local and those with metastatic disease. Although elevated in some patients soluble E-cadherin and E-selectin concentrations were not significantly elevated compared with the control group (P = 0.71 and P = 0.052 respectively). The levels of circulating ICAM-1 were significantly correlated with those of VCAM-1 and E-selectin. A correlation was also found between the serum concentrations of E-selectin and ICAM-1 and alkaline phosphatase, total white cell count and platelet count. VCAM-1 was positively correlated with age and negatively with degree of tumour differentiation and haemoglobin concentration. The biological implications and possible clinical relevance of these findings are discussed.  相似文献   
82.
The utility of modified vaccinia virus Ankara (MVA) as a vector for eliciting AIDS virus-specific cytotoxic T lymphocytes (CTL) was explored in the simian immunodeficiency virus (SIV)/rhesus monkey model. After two intramuscular immunizations with recombinant MVA-SIVSM gag pol, the monkeys developed a Gag epitope-specific CTL response readily detected in peripheral blood lymphocytes by using a functional killing assay. Moreover, those immunizations also elicited a population of CD8+ T lymphocytes in the peripheral blood that bound a specific major histocompatibility complex class I/peptide tetramer. These Gag epitope-specific CD8+ T lymphocytes also were demonstrated by using both functional and tetramer-binding assays in lymph nodes of the immunized monkeys. These observations suggest that MVA may prove a useful vector for an HIV-1 vaccine. They also suggest that tetramer staining may be a useful technology for monitoring CTL generation in vaccine trials in nonhuman primates and in humans.  相似文献   
83.
In addition to causing embarassment and unease, flatulence is linked to a variety of symptoms, some of which may be distressing. This review describes the origins of intestinal gas, its composition and methods which have been developed for its analysis. Emphasis is placed upon the effects of legumes in the diet in producing excessive intestinal gas and, particularly, on the role of raffinose-type oligosaccharides, containing α-galactosidic groupings. Suggestions for overcoming the problem are presented, including drug treatment, enzyme treatment, food processing and plant breeding. It is emphasised that removal of all raffinose-oligosaccharides from beans does not remove the problem of flatulence in animals and man; the compounds responsible — though assumed to be polysaccharides (or polysaccharide-derived oligomers formed by processing or cooking) — have yet to be characterised.  相似文献   
84.
85.
Checklists and other tools help doctors to use published evidence in clinical practice. Two other important sources of evidence, however, are the patient and his or her medical record. This series aims to advance the practice of evidence-based medicine by helping in redesign of medical records, drawing on insights from psychology, information design, and medical informatics; and by promoting changes analogous to those occurring in the medical literature. The four papers look at: the uses of medical records and importance of organising them so doctors can use the data they contain; different methods doctors use to search for data and how design of records can help or hinder these approaches; how we interpret data once found, and how record formatting assists this process; and the issues raised by computerisation of records.  相似文献   
86.
87.
Homomeric and heteromeric alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor subunits GluR1o and GluR3o were expressed in Spodoptera frugiperda (Sf9) insect cells. Membranes containing the recombinant receptors showed a doublet of bands of the expected size (99-109 kDa) after western immunoblotting which was shifted to a single band upon deglycosylation. In (R,S)-[3H]AMPA binding experiments, high expression was seen (Bmax = 0.8-3.8 pmol/mg protein) along with high affinity binding to a single site (Kd, nM+/-S.D.): GluR1o, 32.5+/-2.7; GluR3o, 23.7+/-2.4; GluR1o + GluR3o, 18.1+/-2.9. The pharmacological profiles of these receptors resembled that of native rat brain AMPA receptors: AMPA analogues > L-glutamate > quinoxaline-2,3-diones > kainate. In the Xenopus oocyte expression system we had previously shown that the agonist (R,S)-2-amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionate (ACPA) exhibited an 11-fold selectivity for GluR3o vs. GluR1o. In this study, it was found that ACPA has 3-fold higher affinity at homomeric GluR3o and heteromeric receptors than at homomeric GluR1o, suggesting that its efficacy and/or desensitisation properties are different at GluR1o vs. GluR3o.  相似文献   
88.
Fecal neutral steroids and bile acids were measured in patients with familial polyposis, family controls who are immediate relatives of patients, and controls other than relatives. All subjects were consuming a mixed Western diet at the time of collection of stool specimens. Although the total fecal neutral sterol concentrations were not different between the groups, the patients with familial polyposis excreted a high amount of cholesterol and low levels of coprostanol and coprostanone compared with other groups. Patients with familial polyposis excreted levels of total bile acids in their feces comparable to those excreted by controls; lithocholic acid excretion was decreased in patients with familial polyposis. These findings suggest that analysis of stools for cholesterol and its metabolites be useful in screening the siblings of polyposis families for latent disease.  相似文献   
89.
Four cases of intrauterine fetal demise in term infants are presented. From these cases and other published reports, a sequence of fetal heart rate changes preceding intrapartum death is presented. Late or variable decelerations, if unrelieved or uncorrected, lead to baseline heart rate changes of tachycardia and loss of variability reflecting loss of fetal reserve and fetal distress. This is followed by an unstable heart rate, a sinusoidal pattern, or a rapidly changing fetal heart rate. The final event is a profound bradycardia just prior to fetal demise.  相似文献   
90.
P.A. Mawer  T. Wyatt 《Desalination》1973,13(3):333-342
Two case studies are described relating to the integrated use of desalination with conventional water resources.The first study describes work undertaken at the request of the Government of Cyprus to advise on the potential role of desalination in the long-term development of the island's water resources. Special features of the study are the strong influence of irrigation demands and the need to devise plans which are flexible against an only partially defined future.The second study relates to the 1.5 mgd MSF plant operated by the Jersey New Water Works Company (Jersey. Channel Islands) where the objective is to maintain overall supply reliability at minimum cost. The plant is operated in conjunction with an unusually complex system of surface water resources which present special difficulties in the optimization of control rules for the desalination plant.  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