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   382篇
  免费   10篇
电工技术   2篇
化学工业   52篇
金属工艺   5篇
机械仪表   5篇
建筑科学   14篇
能源动力   26篇
轻工业   54篇
水利工程   1篇
石油天然气   1篇
无线电   79篇
一般工业技术   53篇
冶金工业   78篇
原子能技术   4篇
自动化技术   18篇
  2024年   2篇
  2023年   4篇
  2022年   4篇
  2021年   12篇
  2020年   6篇
  2018年   2篇
  2017年   5篇
  2016年   2篇
  2015年   5篇
  2014年   7篇
  2013年   14篇
  2012年   14篇
  2011年   12篇
  2010年   8篇
  2009年   11篇
  2008年   13篇
  2007年   13篇
  2006年   13篇
  2005年   17篇
  2004年   16篇
  2003年   7篇
  2002年   15篇
  2001年   7篇
  2000年   8篇
  1999年   14篇
  1998年   27篇
  1997年   17篇
  1996年   23篇
  1995年   14篇
  1994年   8篇
  1993年   7篇
  1992年   9篇
  1991年   3篇
  1990年   3篇
  1989年   4篇
  1988年   4篇
  1987年   4篇
  1985年   3篇
  1984年   5篇
  1982年   2篇
  1977年   4篇
  1976年   3篇
  1975年   4篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1971年   1篇
  1970年   1篇
  1968年   1篇
  1960年   1篇
排序方式: 共有392条查询结果,搜索用时 15 毫秒
91.
Biologic scaffolds composed of extracellular matrix components have been proposed to repair and reconstruct a variety of tissues in clinical and pre-clinical studies. Injectable gels can fill and conform any three-dimensional shape and can be delivered to sites of interest by minimally invasive techniques. In this study, a biological gel was produced from a decellularized porcine urinary bladder by enzymatic digestion with pepsin. The enzymatic digestion was confirmed by visual inspection after dissolution in phosphate-buffered saline solution and Fourier-transform infrared spectroscopy. The rheological and biological properties of the gel were characterized and compared to those of the MatrigelTM chosen as a reference material. The storage modulus G’ reached 19.4 ± 3.7 Pa for the 30 mg/mL digested decellularized bladder gels after ca. 3 h at 37 °C. The results show that the gel formed of the porcine urinary bladder favored the spontaneous differentiation of human and rabbit adipose-derived stem cells in vitro into smooth muscle cells to the detriment of cell proliferation. The results support the potential of the developed injectable gel for tissue engineering applications to reconstruct for instance the detrusor muscle part of the human urinary bladder.  相似文献   
92.
Particulate matter is linked to adverse health effects, however, little is known about health effects of particles emitted from typical indoor sources. We examined acute health effects of short-term exposure to emissions from cooking and candles among asthmatics. In a randomized controlled double-blinded crossover study, 36 young non-smoking asthmatics attended three exposure sessions lasting 5 h: (a) air mixed with emissions from cooking (fine particle mass concentration): (PM2.5: 96.1 μg/m3), (b) air mixed with emissions from candles (PM2.5: 89.8 μg/m3), and c) clean filtered air (PM2.5: 5.8 μg/m3). Health effects (spirometry, fractional exhaled Nitric Oxide [FeNO], nasal volume and self-reported symptoms) were evaluated before exposure start, then 5 and 24 h after. During exposures volatile organic compounds (VOCs), particle size distributions, number concentrations and optical properties were measured. Generally, no statistically significant changes were observed in spirometry, FeNO, or nasal volume comparing cooking and candle exposures to clean air. In males, nasal volume and FeNO decreased after exposure to cooking and candles, respectively. Participants reported additional and more pronounced symptoms during exposure to cooking and candles compared to clean air. The results indicate that emissions from cooking and candles exert mild inflammation in asthmatic males and decrease comfort among asthmatic males and females.  相似文献   
93.
Process water deriving from digested sludge dewatering at municipal wastewater treatment plants (WWTP) represents an additional load for the plant in terms of nitrogen. Münster WWTP is the first German plant to operate an innovative full-scale membrane contactor facility for nitrogen removal and recovery from process water. Within the scope of this study, aspects influencing the membrane performance and operation as well as utilization of the produced fertilizer are investigated. First results reveal nitrogen removal efficiencies around 85 % and a regional usability of the produced fertilizer.  相似文献   
94.
Mono- and disubstitution of HCo(CO)4 with tertiary phosphines and phosphites was studied by IR and1H-NMR spectroscopy. It was found that these substitutions proceed through phosphonium tetracarbonylcobaltate intermediates, leading to a mixture of isomers. The crystal and molecular structure of trans-HCo(CO)3[P(O-p-C6H4Ph)3] was determined by X-ray diffraction.GDR research fellow at the University of Veszprém.  相似文献   
95.
Finite element and boundary element methods are described for predicting high-frequency electromagnetic heating of tissue as a cancer therapy. For the class of clinical problems of interest, the patient is electrically inhomogeneous and best discretized by finite elements, but the unbounded nature of practical source configurations calls for a boundary element approach. A hybrid is introduced which couples the two methods and is superior in algebraic requirements to either method alone. The formulation is three-dimensional and allows exact satisfaction of the electromagnetic jump conditions at interfaces separating distinct tissue types. Test cases show its validity for transverse magnetic and electric situations with known solutions. Examples of clinical applications are shown.  相似文献   
96.
One hundred consecutive patients were treated with the Herbst appliance in the period of puberty to adulthood. The orthopaedic effects on the morphology of the condyles were described from orthopantomographic and transpharyngeal radiographs. The orthopaedic treatment effect was, in most cases, visible as a change in morphology of the condyle, a double contour in the distocranial part of the condyle and sometimes also at the distal surface of the ramus. In patients at the peak of puberty, the double contour was distinct for a short time. In patients in late puberty, the double contour could be seen several months after treatment. At adulthood, males showed, in most cases, double contours, while females showed in most cases nearly unchanged condyles. When double contours were seen, these persisted for a few months to several years after Herbst treatment. The newly formed bone was stable and no TMJ problems were observed. The change in morphology and the double contour of the condyle can be interpreted as bone modelling. The newly formed bone on the posterior part of the condyle can be explained as a response to hypertropic chondrocytes, and that on the posterior part of the ramus as a response of resting osteoblasts to mechanically induced changes in the condyle (adaptive bone growth). In two cases, remodelling resorption was found in the anterior part of the condyle after Herbst treatment, again as a sign of adaptation to changed mechanical influence. In both cases, later refilling with bone was registered during the remodelling process. The biomechanical effect of Herbst treatment on the mandible is also analogous with an impeded matrix rotation combined with relocation of the mandible.  相似文献   
97.
The definitive function of pancreatic polypeptide in mammalian physiology remains unknown. The identification of specific PP target tissues should be helpful to further investigations into the possible regulatory actions of this peptide. An in vivo radioreceptor assay was used in the rat to locate potential binding sites of I(125) bovine PP. In vitro, high concentrations of unlabeled hormone competitively inhibit binding to receptors by low concentrations of labeled hormone. In vivo studies showed that, in the presence of concentrated unlabeled pancreatic polypeptide, labeled PP distributes between the plasma and interstitial fluid. When excess unlabeled PP is replaced with saline in the companion animals, the labeled peptide appears to distribute in a volume that exceeds the combined plasma volume and interstitial fluid volume of the tissue. Using this in vivo receptor assay, the distribution volume that exceeds the anatomic extracellular volume has been identified as the receptor compartment. With this assay we demonstrated in the rat specific and displaceable PP binding to the ductus choledochus, duodenum, ileum, and adrenal gland. The NVV determined in the adrenal gland of experimental animals was 3.9 times greater than that found in the control group. Binding was rapid and was displaced only by excess unlabeled pancreatic polypeptide. Neither excess insulin nor excess neuropeptide Y significantly reduced this binding.  相似文献   
98.
A method is presented for computing accurate solutions of Maxwell's equations in the presence of perfect electrical conductors (PECs) with sharp corners and highly curved surfaces using conventional nodal finite elements and a scalar/vector (S/V) potential formulation. This technique approximates the PEC with an impedance boundary condition (IBC) where the impedance is small. Critically, it couples both potentials through this boundary condition, rather than setting the scalar potential to zero. This permits cancellation of the tangential components of the vector potential, resulting in an accurate normal electric field. The cause for the inaccuracies that nodal methods experience In the presence of sharp PEC corners or highly curved PEC surfaces is elucidated. It is then shown how the inclusion of the scalar potential cures these deficiencies permitting accurate solutions. Spectral analysis of the resulting finite element matrices are shown validating the boundary conditions used. Examples are presented comparing a benchmark solution, conventional PEC and IBC boundary conditions, and the new S/V potential IBC on a PEC wedge and PEC ellipse. In both cases the new S/V IBC produces superior results  相似文献   
99.
Interactive media need their own idioms that exploit the characteristics of the computer based sign. The fact that the reader can physically influence the course of events in the system changes the author's role, since he no longer creates a linear text but anarrative space that the reader can use to generate stories. Although stories are not simulations of the real world, they must still contain recognizable parts where everyday constraints of time and space hold. AI-techniques can be used to implement these constraints. In fact, we suggest that AI is probably best seen as an aesthetic phenomenon.  相似文献   
100.
Finite, boundary, and hybrid element approaches are presented as numerical methods for computing electromagnetic (EM) fields inside lossy dielectric objects. These techniques are implemented as computer algorithms for solving the Maxwell equations in heterogeneous media in three dimensions. Algorithm verification takes the form of comparisons of test cases with analytic solutions. Computed results for each technique are in good agreement with exact solutions, especially in light of the coarse computational grid resolutions used. Implementation was in FORTRAN on a moderate-sized computer (MicroVax II). The basic problem formulation is quite general; however, it has direct application in hyperthermia as a cancer therapy where the EM fields produced inside the patient by external sources are of interest. An example of the application of these numerical methods in a three-dimensional clinical setting is shown  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