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   559篇
  免费   7篇
  国内免费   2篇
电工技术   18篇
化学工业   70篇
金属工艺   4篇
机械仪表   11篇
建筑科学   9篇
矿业工程   2篇
能源动力   9篇
轻工业   57篇
水利工程   3篇
石油天然气   2篇
无线电   27篇
一般工业技术   68篇
冶金工业   222篇
原子能技术   10篇
自动化技术   56篇
  2023年   2篇
  2022年   8篇
  2021年   6篇
  2020年   5篇
  2019年   7篇
  2018年   4篇
  2017年   2篇
  2016年   8篇
  2015年   5篇
  2014年   11篇
  2013年   9篇
  2012年   15篇
  2011年   22篇
  2010年   10篇
  2009年   13篇
  2008年   14篇
  2007年   12篇
  2006年   19篇
  2005年   14篇
  2004年   16篇
  2003年   7篇
  2002年   15篇
  2001年   15篇
  2000年   12篇
  1999年   20篇
  1998年   83篇
  1997年   46篇
  1996年   30篇
  1995年   22篇
  1994年   20篇
  1993年   16篇
  1992年   9篇
  1991年   5篇
  1989年   13篇
  1988年   11篇
  1987年   4篇
  1986年   3篇
  1985年   3篇
  1984年   4篇
  1983年   3篇
  1981年   2篇
  1980年   3篇
  1979年   3篇
  1977年   3篇
  1976年   5篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1969年   2篇
  1967年   1篇
排序方式: 共有568条查询结果,搜索用时 31 毫秒
61.
This paper presents an extension to the existing dynamic relaxation method to include equality constraint conditions in the process. The existing dynamic relaxation method is presented as a general, gradient‐based, minimization technique. This representation allows for the introduction of the projected gradient, discrete parallel transportation and pull back operators that enable the formulation of the geodesic dynamic relaxation method, a method that accounts for equality constraint conditions. The characteristics of both the existing and geodesic dynamic relaxation methods are discussed in terms of the system's conservation of energy, damping (viscous, kinetic, and drift), and geometry generation. Particular attention is drawn to the introduction of a novel damping approach named drift damping. This technique is essentially a combination of viscous and kinetic damping. It allows for a smooth and fast convergence rate in both the existing and geodesic dynamic relaxation processes. The case study was performed on the form‐finding of an iconic, ridge‐and‐valley, pre‐stressed membrane system, which is supported by masts. The study shows the potential of the proposed method to account for specified (total) length requirements. The geodesic dynamic relaxation technique is widely applicable to the form‐finding of force‐modeled systems (including mechanically and pressurized pre‐stressed membranes) where equality constraint control is desired. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
62.
For full understanding of the optical properties of alumina ceramics which are used as a substrate of thin film c-Si solar cells, we carried out computer simulations of diffuse reflectance and measurements of angle-resolved reflectance. As the result of the computer simulations, we obtained a theoretical expression for the reflectance properties of alumina ceramics with flat surface. The expression can be applied for the measured reflectance of alumina ceramics with rough surface when an effect of surface condition was taken into account.  相似文献   
63.
We performed randomized controlled study to compare the short-term therapeutic effect of total parenteral nutrition (TPN), elemental diet (ED) and polymeric diet (PD) given as primary therapy in active phase of Crohn's disease. In hospital for Crohn's disease, twenty-eight patients were given nutritional therapy: 9 patients by TPN, 10 by ED, and 9 by PD. Nutritional state, inflammatory reactions, disease activity and clinical remission rate were assessed two weeks and four weeks after treatment, and morphological findings were assessed before and after each nutritional therapy by radiographic and colonoscopic findings. Inflammatory reactions were more effectively controlled by TPN and ED than by PD, and early improvement achieved by TPN and ED was especially note-worthy. Clinical remission rate after treatment by TPN was highest in three types of nutritional approach, but no significant difference was seen at any point. In nutritional state, disease activity and morphological findings, comparable changes were effected without preference. These results suggest that nutritional therapy by total parenteral nutrition and elemental diet is superior to polymeric diet for treating active phase of Crohn's disease with marked inflammatory reactions.  相似文献   
64.
65.
The pathophysiology of preeclampsia has not been fully clarified. A variety of factors have been implicated with this disease including vasoactive peptides and hormones during the last 20 years. Inadequate generation of atrial natriuretic peptide (ANP) has been one of the mechanisms discussed as to possibly contribute to the development of hypertension. In human pregnancy multiple studies of ANP-plasma-concentration in normal or hypertensive pregnancies showed conflicting results. The complexity of the clinical findings of hypertension in pregnancy makes it very difficult to carry out comparative clinical and biochemical studies in humans. In an animal experience genetic as environmental influences could be excluded. Therefore, the present study shows an experimental preeclampsia-like syndrome in the rat by reduction of the utero-placental flow. We observed a significant increase of plasma ANP in pregnant rats with experimentally induced hypertension. Furthermore, our results suggest that the ventricles could be an important source of ANP gene expression.  相似文献   
66.
OBJECTIVE: This study aimed to investigate the incidence of cystoid macular edema and anterior uveitis associated with the use of latanoprost. DESIGN: A retrospective review of patients treated with latanoprost in the authors' practice between September 1, 1996, and August 1, 1997, was performed. PARTICIPANTS: Ninety-four patients and 163 eyes were studied. INTERVENTION: Patients presenting with signs and symptoms of ocular inflammation while receiving latanoprost were noted, and their response to the discontinuation of the drug was recorded. MAIN OUTCOME MEASURES: The presence and degree of anterior uveitis and cystoid macular edema were measured. RESULTS: Six (6.4%) of 94 patients (8 [4.9%] of 163 eyes) had anterior uveitis develop, and 2 (2.1%) of 94 patients (2 [1.2%] of 163 eyes) had cystoid macular edema develop while being treated with latanoprost. CONCLUSION: Although latanoprost is an effective ocular-hypotensive agent, the authors' experience with the drug has shown a significant incidence of anterior uveitis and cystoid macular edema. To the authors' knowledge, this is the first study to report the incidence of both cystoid macular edema and anterior uveitis associated with latanoprost therapy. Treating physicians should be aware of these potential complicating side effects of latanoprost.  相似文献   
67.
Improving the detection of requirements discordances among stakeholders   总被引:1,自引:1,他引:0  
This paper introduces a technique to identify requirements discordances among stakeholders. This technique is validated in experiments. An extended version of the goal-oriented requirements elicitation method, named attributed goal-oriented analysis (AGORA), and its supporting tool are used. Two types of requirements discordances among stakeholders are defined: the first arises from the different interpretations by the stakeholders and the second is the result of different evaluations of preferences. Discordances are detected by the preference matrices in AGORA. Each preference matrix represents both preferences of each stakeholder and the estimated preferences of other stakeholders. A supporting tool for the AGORA method was developed. This tool is a groupware that seamlessly combines face-to-face meetings for goal elicitation and distributed individual sessions for scoring preference values. The experimental results showed that the proposed classification of discordances was sound and that the occurrences of the requirements discordances could be detected by preference matrices.  相似文献   
68.
We designed the present study to examine the cross-sectional relation between age-related lens opacities and vitamin C supplement use over a 10-12-y period before assessment of lens status in women without diagnosed cataract or diabetes. This design avoids biased measurement of nutrient intake that results when knowledge of lens opacities influences nutrition-related behavior or its reporting. The participants were 247 Boston-area women aged 56-71 y selected from the Nurses' Health Study cohort with oversampling of women with high or low vitamin C intakes. Lens opacities were graded with the Lens Opacification Classification System II. Use of vitamin C supplements for > or = 10 y (n = 26) was associated with a 77% lower prevalence of early lens opacities (odds ratio: 0.23; 95% CI: 0.09, 0.60) at any lens site and a 83% lower prevalence of moderate lens opacities (odds ratio: 0.17; 95% CI: 0.03, 0.85) at any lens site compared with women who did not use vitamin C supplements (n = 141) after adjustment for age and other potentially confounding variables. Women who consumed vitamin C supplements for < 10 y showed no evidence of a reduced prevalence of early opacities. These data, together with data from earlier experimental and epidemiologic studies, suggest that long-term consumption of vitamin C supplements may substantially reduce the development of age-related lens opacities.  相似文献   
69.
70.
Oligosaccharides, especially mannose residues, expressed on the cell surface, are thought to be important for virus-induced membrane fusion. We examined the effect of mannose-binding compounds, pradimicin derivative BMY-28,864 (PRM) and concanavalin A (Con A), on cell fusion of human parainfluenza type 2 virus (hPIV2)-infected HeLa cells. Syncytium formation of hPIV2-infected HeLa cells was suppressed in the presence of Con A. On the other hand, PRM enhanced cell fusion of hPIV2-infected HeLa cells. These effects were blocked by addition of mannose-rich mannan. However, PRM shows little effect on virus growth and the expression of viral glycoproteins on the cell surface in hPIV2-infected HeLa cells. Fluorescein-isothiocyanate-labeled pradimicin and Con A bound to both uninfected and hPIV2-infected mononuclear cells, indicating that these compounds have an affinity to several cellular component(s). In contrast to Con A, PRM had little affinity to the viral glycoproteins. It is inferred from these results that the enhancement of hPIV2-induced cell fusion is probably due to the interaction between PRM and cellular component(s).  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