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   1180篇
  免费   4篇
  国内免费   2篇
电工技术   1篇
化学工业   6篇
金属工艺   17篇
机械仪表   9篇
建筑科学   6篇
能源动力   3篇
轻工业   45篇
水利工程   3篇
石油天然气   1篇
无线电   1篇
一般工业技术   16篇
冶金工业   1060篇
原子能技术   1篇
自动化技术   17篇
  2023年   2篇
  2022年   2篇
  2020年   1篇
  2019年   2篇
  2018年   5篇
  2017年   4篇
  2016年   6篇
  2015年   3篇
  2014年   6篇
  2013年   24篇
  2012年   6篇
  2011年   5篇
  2010年   8篇
  2009年   5篇
  2008年   3篇
  2007年   1篇
  2006年   5篇
  2005年   1篇
  2004年   4篇
  2002年   2篇
  1999年   32篇
  1998年   282篇
  1997年   191篇
  1996年   111篇
  1995年   72篇
  1994年   58篇
  1993年   63篇
  1992年   9篇
  1991年   14篇
  1990年   22篇
  1989年   27篇
  1988年   18篇
  1987年   20篇
  1986年   13篇
  1985年   13篇
  1984年   1篇
  1983年   4篇
  1982年   8篇
  1981年   8篇
  1980年   9篇
  1978年   2篇
  1977年   43篇
  1976年   66篇
  1975年   2篇
  1955年   3篇
排序方式: 共有1186条查询结果,搜索用时 15 毫秒
51.
52.
Treatment and prognosis of urinary bladder cancer largely are determined by the tumor stage and presence of metastases. MR imaging and clinical staging complement each other. MR imaging is the most accurate technique for differentiating the various stages of deep tumor infiltration and detection of metastases, whereas clinical staging is the best technique for differentiating between postbiopsy effects and the various stages of superficial tumors. The role of MR imaging in staging of this disease and monitoring of therapy is reviewed and illustrated. Finally, the authors present an overview of current and future applications of this technique.  相似文献   
53.
54.
Deletions of the distal short arm of chromosome 1 (1p36) represent a common, newly delineated deletion syndrome, characterized by moderate to severe psychomotor retardation, seizures, growth delay, and dysmorphic features. Previous cytogenetic underascertainment of this chromosomal deletion has made it difficult to characterize the clinical and molecular aspects of the syndrome. Recent advances in cytogenetic technology, particularly FISH, have greatly improved the ability to identify 1p36 deletions and have allowed a clearer definition of the clinical phenotype and molecular characteristics of this syndrome. We have identified 14 patients with chromosome 1p36 deletions and have assessed the frequency of each phenotypic feature and clinical manifestation in the 13 patients with pure 1p36 deletions. The physical extent and parental origin of each deletion were determined by use of FISH probes on cytogenetic preparations and by analysis of polymorphic DNA markers in the patients and their available parents. Clinical examinations revealed that the most common features and medical problems in patients with this deletion syndrome include large anterior fontanelle (100%), motor delay/hypotonia (92%), moderate to severe mental retardation (92%), growth delay (85%), pointed chin (80%), eye/vision problems (75%), seizures (72%), flat nasal bridge (65%), clinodactyly and/or short fifth finger(s) (64%), low-set ear(s) (59%), ear asymmetry (57%), hearing deficits (56%), abusive behavior (56%), thickened ear helices (53%), and deep-set eyes (50%). FISH and DNA polymorphism analysis showed that there is no uniform region of deletion but, rather, a spectrum of different deletion sizes with a common minimal region of deletion overlap.  相似文献   
55.
An agile manufacturing workcell design   总被引:1,自引:0,他引:1  
This paper introduces a design for agile manufacturing worked Is intended for light mechanical assembly of products made from similar components (i.e., parts families). We define agile manufacturing as the ability to accomplish rapid changeover from the assembly of one product to the assembly of a different product. Rapid hardware changeover is made possible through the use of robots, flexible part feeders, modular grippers, and modular assembly hardware. The division of assembly, feeding, and unloading tasks between multiple robots is examined with prioritization based upon assembly time. Rapid software changeover will be facilitated by the use of a real-time, object-oriented software environment utilizing graphical simulations for off-line software development. An innovative dual VMEbus controller architecture permits an open software environment while accommodating the closed nature of most commercial robot controllers. These agile features permit new products to be introduced with minimal downtime and system reconfiguration.  相似文献   
56.
Flow profiles of commercially processed whole, two-percent, one-percent and nonfat milks with added solids as well as skim milk without added solids were measured using a rotational steady shear viscometer. Also tested were mixtures of concentrated skim milk added to skim milk over a range of 9.7% to 20.2% total solids. A shear rate range of 121 to 486 s-1 was used with a cone and plate geometry. In all cases, linear plots of shear stress versus shear rate with small nonzero intercepts were obtained.  相似文献   
57.
Systemic lupus erythematosus (SLE) is an inflammatory systemic disease that causes organ damage by the deposition of autoantibodies and complement activating immune complexes or by vascular occlusion due to procoagulant states associated with antiphospholipid antibodies. The vast majority of cases occur in women of childbearing age. SLE is diagnosed on the basis of its clinical manifestations and the demonstration of characteristic immunological phenomena, especially anti-nuclear antibodies. The prognosis in SLE has shown a distinct improvement over recent decades, the 5-year survival rate now approaching or exceeding 90%. The 15-year survival rate of 63 to 79%, on the other hand, underscores the need for further advances in diagnosis and treatment of the disease. Management of the disease includes regular monitoring of disease activity, avoidance of predisposing factors and close supervision of therapy. Drug therapy is guided by the activity and severity of the leading organ manifestations and ranges from nonsteroidal antirheumatic drugs to intensive treatment with cytotoxic agents. Corticosteroids remain irreplaceable for the control of acute flares. Antimalarials and azathioprine are important long term drugs for treating mild or moderate disease activity. Intravenous pulse cyclophosphamide is safer than other regimens and at least as effective as oral cyclophosphamide for severe lupus nephritis. It is also effective in the treatment of central nervous disease and of other organ-threatening manifestations. Recently, an intensified protocol which included cyclophosphamide induced long term treatment-free remission in 60% of patients. The toxicity of cyclophosphamide is considerable, but can be ameliorated by various measures. The value of several new immunosuppressants and other compounds remains to be determined.  相似文献   
58.
59.
The effect of 2 months of treatment with the oral growth hormone (GH) secretagogue MK-677 on markers of bone metabolism was determined in healthy obese male subjects. This was a randomized, double-blind, parallel, placebo-controlled study. Twenty-four healthy obese males, 19-49 years of age, with body mass index > 30 kg/m2 were treated with MK-677 (25 mg/day; n = 12) or placebo (n = 12) for 8 weeks. MK-677 increased markers of bone formation; a 23% increase in the carboxy-terminal propeptide of type I procollagen levels and a 28% increase in procollagen III peptide levels were seen with as little as 2 weeks of MK-677 treatment (p < 0.01 and p = 0.001 vs. placebo, respectively) while a 15% increase in serum levels of osteocalcin was not detected until 8 weeks of treatment (p < 0.01 vs. placebo). Markers of bone resorption were induced within 2 weeks of treatment with MK-677; serum levels of the carboxy-terminal cross-linked telopeptide of type I collagen were increased 26% at 8 weeks (p = 0.001 vs. placebo), and urine hydroxyproline/creatinine and calcium/creatinine ratios at 8 weeks were increased by 23% (p < 0.05 vs. placebo) and 46% (p < 0.05 vs placebo), respectively, MK-677 increased serum insulin-like growth factor binding protein-5 (IGFBP-5) by 43-44% after 2-8 weeks of treatment (p < 0.01 vs. placebo). Serum IGFBP-4 was increased by 25% after 2 weeks of treatment (p < 0.001 vs. placebo) but no significant change from baseline was observed after 8 weeks of treatment. Plasma interleukin-6 was not significantly changed by active treatment. In conclusion, short-term treatment of healthy obese male volunteers with the GH secretagogue MK-677 increases markers of both bone resorption and formation. Large increases in serum levels of IGF-1 and IGFBP-5 and a transient increase in serum IGFBP-4 were found. Future long-term studies are needed to investigate if prolonged treatment with MK-677 increases bone mass.  相似文献   
60.
In eastern U.S. oak forests, defoliation by gypsy moths and the risk of Lyme disease are determined by interactions among acorns, white-footed mice, moths, deer, and ticks. Experimental removal of mice, which eat moth pupae, demonstrated that moth outbreaks are caused by reductions in mouse density that occur when there are no acorns. Experimental acorn addition increased mouse density. Acorn addition also increased densities of black-legged ticks, evidently by attracting deer, which are key tick hosts. Mice are primarily responsible for infecting ticks with the Lyme disease agent. The results have important implications for predicting and managing forest health and human health.  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