首页 | 官方网站   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   1450篇
  免费   24篇
  国内免费   1篇
工业技术   1475篇
  2021年   6篇
  2020年   9篇
  2019年   9篇
  2018年   8篇
  2017年   15篇
  2016年   10篇
  2015年   12篇
  2014年   21篇
  2013年   60篇
  2012年   26篇
  2011年   53篇
  2010年   50篇
  2009年   27篇
  2008年   45篇
  2007年   45篇
  2006年   47篇
  2005年   29篇
  2004年   31篇
  2003年   37篇
  2002年   36篇
  2001年   21篇
  2000年   29篇
  1999年   34篇
  1998年   127篇
  1997年   78篇
  1996年   64篇
  1995年   49篇
  1994年   33篇
  1993年   41篇
  1992年   25篇
  1991年   14篇
  1990年   20篇
  1989年   24篇
  1988年   15篇
  1987年   16篇
  1986年   19篇
  1985年   18篇
  1984年   21篇
  1983年   19篇
  1982年   24篇
  1981年   20篇
  1980年   13篇
  1979年   20篇
  1978年   18篇
  1977年   20篇
  1976年   42篇
  1975年   9篇
  1974年   10篇
  1973年   5篇
  1966年   5篇
排序方式: 共有1475条查询结果,搜索用时 15 毫秒
1.
Planning is an essential function of project management. Yet, many small- and medium-sized contractors do a relatively poor job of operational planning. Better prebid plans will reduce costs, shorten schedules, and improve labor productivity. Unfortunately, the published literature offers little guidance for smaller contractors on what constitutes effective planning. Most papers describe planning as a macrolevel process for owners. Most emphasize scope definition for industrial projects. This paper describes a microlevel planning process for contractors. It consists of eight steps which are: (1) assess contract risks; (2) develop a preliminary execution plan; (3) develop site layout plans; (4) identify the sequences that are essential-to-success; (5) develop detailed operational plans; (6) develop proactive strategies to assure construction input into design; (7) revise the preliminary plan; and (8) communicate and enforce the plan. The entire process is illustrated with a case study project and is fully illustrated with figures which show how to integrate the work of multiple contractors, keep key resources (crews or equipment) fully engaged with no downtime, provide time buffers so the work of follow on crews can be efficiently done, expedite the schedule using multiple work stations and concurrent work, ways to communicate the work plan to the superintendent and foremen, and how to assess the feasibility of various work methods. The steps are easy to understand and implement. They will yield immediate positive results.  相似文献   
2.
BACKGROUND: The effects of stroke on classically nondominant hemisphere functions have received less attention than those on the dominant hemisphere, but visuospatial neglect and denial of illness both produce significant morbidity. SUMMARY OF COMMENT: The early literature on denial of illness is discussed and the etiological theories are examined. These are explanations based on deficits of higher mental function, impaired sensory input (especially proprioceptive), an abnormal representation of body image, psychodynamic defense mechanisms, and/or premorbid personality factors. CONCLUSIONS: Denial of illness is an important consequence of stroke. No explanation thus far proposed is entirely satisfactory. The consequences on rehabilitation and strategies for therapy have not been adequately investigated.  相似文献   
3.
The purpose of this study was to determine the outcome of patients with metastatic breast cancer treated with high-dose busulfan (Bu), melphalan (Mel) and thiotepa (TT) followed by peripheral blood stem cell (PBSC) infusion. Fifty-one patients with chemotherapy refractory (n = 32) or responsive (n = 19) metastatic breast cancer received Bu (12 mg/kg), Mel (100 mg/m2) and TT (500 mg/m2) followed by PBSC collected after chemotherapy and growth factor (n = 43) or growth factor alone (n = 8). The 100 day treatment-related mortality was 8% including one death from cytomegalovirus pneumonia, one from aspiration pneumonia and two from regimen-related toxicity (RRT). Seven of 28 refractory (25%) and 5/7 (71%) responsive patients with evaluable disease achieved a complete response of all measurable disease or all soft tissue disease with at least improvement in bone lesions (PR*). Fifteen of 51 patients (29%) are alive and progression-free a median of 423 days (range 353-934) after treatment, 5/32 (16%) with refractory disease and 10/19 (53%) with responsive disease. The probabilities of progression-free survival (PFS) at 1.5 years for the patients with refractory (n = 32) and responsive (n = 19) disease were 0.24 and 0.53, respectively. These preliminary data suggest that high-dose Bu/Mel/TT has significant activity in patients with advanced breast cancer and may be superior to some previously published regimens.  相似文献   
4.
Many cognitive tasks that are easy for humans to perform are proving difficult to emulate in computer systems. Combining the disciplines of psychology and engineering may offer a solution to some of these problems. A connectionist or neural network model of face recognition by humans which incorporates aspects of a model proposed by cognitive psychologists is presented. A comparative set of experiments has been performed using this simulation and human subjects for familiar face recognition. By employing the same stimuli for both humans and the computer model, it is possible to advance not only our understanding of human cognition but also to develop improved automated systems for face recognition  相似文献   
5.
Knowledge conceptualization tool   总被引:3,自引:0,他引:3  
Knowledge acquisition is one of the most important and problematic aspects of developing knowledge-based systems. Many automated tools have been introduced in the past, however, manual techniques are still heavily used. Interviewing is one of the most commonly used manual techniques for a knowledge acquisition process, and few automated support tools exist to help knowledge engineers enhance their performance. The paper presents a knowledge conceptualization tool (KCT) in which the knowledge engineer can effectively retrieve, structure, and formalize knowledge components, so that the resulting knowledge base is accurate and complete. The KCT uses information retrieval technique to facilitate conceptualization, which is one of the human intensive activities of knowledge acquisition. Two information retrieval techniques employing best-match strategies are used: vector space model and probabilistic ranking principle model. A prototype of the KCT was implemented to demonstrate the concept. The results from KCT are compared with the outputs from a manual knowledge acquisition process in terms of amount of information retrieved and the process time spent. An analysis of the results shows that the process time to retrieve knowledge components (e.g., facts, rules, protocols, and uncertainty) of KCT is about half that of the manual process, and the number of knowledge components retrieved from knowledge acquisition activities is four times more than that retrieved through a manual process  相似文献   
6.
Human peripheral blood monocytes were examined for migration across an endothelial cell monolayer in an in vitro vessel wall construct. Few monocytes invaded in the absence of a chemotactic gradient, despite significant adhesion to the endothelial monolayer. However, the addition of zymosan-activated human plasma to the lower compartment, to create a chemotactic gradient across the vessel wall, resulted in significantly enhanced monocyte migration. Pretreatment of the monocytes with monoclonal antibodies to thrombospondin (TSP) dramatically inhibited monocyte diapedesis into the vessel wall. The same treatment inhibited monocyte adhesion to endothelial cells in two-dimensional monolayer cultures as well as in vessel wall constructs (no chemotactic gradient). Of interest, however, the monoclonal antibodies had no inhibitory effect on monocyte migration into collagen gels devoid of endothelial cells in response to the same chemotactic gradient, suggesting the importance of TSP in monocyte-endothelial cell interactions. Monoclonal antibodies to fibronectin and normal mouse immunoglobulin G did not inhibit migration in this model of a vessel wall. Furthermore, monoclonal antibodies to TSP showed no inhibition of human peripheral blood neutrophil migration. Previous studies have shown that monocytes synthesize TSP and express this moiety on their surface. The present data suggest that monocytes may utilize TSP to interact with endothelial cells lining the vessel wall during diapedesis.  相似文献   
7.
A technique for locating a transmission path failure in an inline cascade of semiconductor laser amplifier repeaters to within one fibre span is demonstrated. If a fault occurs, the loss of signal is detected in the following repeaters and a locally generated tone modulates the spontaneous emission of the repeater, signalling the fault to the system terminals.<>  相似文献   
8.
9.
A 6-year-old white female was found to have an adenoid cystic carcinoma originating in a lacrimal gland. Eighteen months following diagnosis, the tumor recurred. Conservative surgery has been the sole mode of therapy. To date, after four operations and quadrimenstral imaging surveillance, there is no sign of disease progression. Our purpose is to record the unusual occurrence of an adenoid cystic carcinoma of the lacrimal gland in a child. An interim report, 32 months after diagnosis, is presented.  相似文献   
10.
Recent studies from our laboratory have shown that in the mouse and rat nephron Ca2+ and Mg2+ are not reabsorbed in the medullary part of the thick ascending limb (mTAL) of Henle's loop. The aim of the present study was to investigate whether the absence of transepithelial Ca2+ and Mg2+ transport in the mouse mTAL is due to its relative low permeability to divalent cations. For this purpose, transepithelial ion net fluxes were measured by electron probe analysis in isolated perfused mouse mTAL segments, when the transepithelial potential difference (PDte.) was varied by chemical voltage clamp, during active NaCl transport inhibition by luminal furosemide. The results show that transepithelial Ca2+ and Mg2+ net fluxes in the mTAL are not driven by the transepithelial PDte. At zero voltage, a small but significant net secretion of Ca2+ into the tubular lumen was observed. With a high lumen-positive PDte generated by creating a transepithelial bath-to-lumen NaCl concentration gradient, no Ca2+ and Mg2+ reabsorption was noted; instead significant and sustained Ca2+ and Mg2+ net secretion occurred. When a lumen-positive PDte was generated in the absence of apical furosemide, but in the presence of a transepithelial bath-to-lumen NaCl concentration gradient, a huge Ca2+ net secretion and a lesser Mg2+ net secretion, not modified by ADH, were observed. Replacement of Na+ by K+ in the lumen perfusate induced, in the absence of PDte changes, important but reversible net secretions of Ca2+ and Mg2+. In conclusion, our results indicate that the passive permeability of the mouse mTAL to divalent cations is very low and not influenced by ADH. This nephron segment can secrete Ca2+ and Mg2+ into the luminal fluid under conditions which elicit large lumen-positive transepithelial potential differences. Given the impermeability of this epithelium to Ca2+ and Mg2+, the secretory processes would appear to be of cellular origin.  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-23

京公网安备 11010802026262号