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   1508篇
  免费   15篇
电工技术   14篇
综合类   1篇
化学工业   101篇
金属工艺   18篇
机械仪表   13篇
建筑科学   38篇
矿业工程   3篇
能源动力   24篇
轻工业   144篇
水利工程   7篇
石油天然气   4篇
无线电   113篇
一般工业技术   156篇
冶金工业   785篇
原子能技术   14篇
自动化技术   88篇
  2022年   10篇
  2021年   21篇
  2018年   11篇
  2016年   8篇
  2015年   11篇
  2014年   13篇
  2013年   31篇
  2012年   24篇
  2011年   22篇
  2010年   17篇
  2009年   21篇
  2008年   30篇
  2007年   32篇
  2006年   32篇
  2005年   34篇
  2004年   22篇
  2003年   30篇
  2002年   28篇
  2001年   22篇
  2000年   22篇
  1999年   52篇
  1998年   236篇
  1997年   165篇
  1996年   94篇
  1995年   45篇
  1994年   46篇
  1993年   45篇
  1992年   17篇
  1991年   16篇
  1990年   21篇
  1989年   12篇
  1988年   20篇
  1987年   16篇
  1986年   19篇
  1985年   17篇
  1984年   12篇
  1983年   12篇
  1982年   8篇
  1981年   14篇
  1980年   19篇
  1979年   7篇
  1978年   12篇
  1977年   24篇
  1976年   43篇
  1975年   15篇
  1974年   10篇
  1973年   10篇
  1972年   10篇
  1970年   8篇
  1926年   6篇
排序方式: 共有1523条查询结果,搜索用时 458 毫秒
51.
Photolithography to produce TiO2 patterns from amorphous films of (5-C5H5)2Ti(N3)2 has been demonstrated. The efficiency of the reaction has been measured yielding a quantum yield of 0.025. The mechanism of the photoreactions of (5-C5H5)2Ti(N3)2 has been studied using Fourier transform-infrared spectroscopy in both a low-temperature 1,2-epoxyethylbenzene glass and as surface films. In each case the primary photochemical process was found to be loss of a single azido group. The result of subsequent photolysis was found to be dependent upon medium and temperature. In the low-temperature glass no further photochemistry was observed. The exhaustive photolysis of films at 20 K, or room temperature, under a vacuum or in air led to loss of all ligands and the formation of TiO2.  相似文献   
52.
The ground-state properties of bulk atomic hydrogen are calculated for the low-density gas, assuming that the atoms interact via the 3 u + pair potential. The Monte Carlo technique is applied to a system consisting of 32 hydrogen atoms in a box, with periodic boundary conditions. These results are compared with those derived from the hard-sphere Bose-Einstein gas model.Work supported by NASA Grant No. NGR 06-002-159.  相似文献   
53.
Preoperative radiotherapy for adenocarcinoma of the rectosigmoid   总被引:2,自引:0,他引:2  
Ninety-seven patients with adenocarcinoma of the rectosigmoid have been treated with high dose (5000-6000 rad) preoperative irradiation from 1960 through 1972 at the University of Oregon Health Sciences Center. Fifty-seven were initially clinically resectable and 40 were initially inoperable. Forty of the 57 initially clinically resectable patients had "curative" resections and are at risk for more than 5 years. An increase in 5-year survival (from 38% to 53%) and an absence of pelvic recurrence have occurred in those patients receiving preoperative irradiation and "curative" resection. Four of the 40 initially inoperable patients are alive without tumor. Three of the four survivors had irradiation and surgery; one had irradiation only. An additional four patients had no evidence of tumor at death. Tumor was totally sterilized by irradiation and nine patients and reduced to microfocal extent in an additional three of the 97 patients. Incidence of complications was no greater than has been reported in a surgical series from the same institution.  相似文献   
54.
55.
The aim of this study was to evaluate the combined effect of salt (sodium chloride, 0–8% w/v), sorbate (potassium sorbate, 0–4.5% w/v), nisin (0–500 ppm) and lysozyme (0–500 ppm) on the survival of Clostridium sporogenes as a non‐toxigenic surrogate of Clostridium botulinum in terms of the probability of growth by using a central composite rotatable design. The results indicated that salt and sorbate were the most effective factors in preventing the growth of Cl. sporogenes in high‐moisture (>95%) and low‐acid conditions. The probability of growth of Cl. sporogenes in broth was reduced by combinations of salt and sorbate. Nisin and lysozyme had insignificant effects on the probability of growth of Cl. sporogenes (P > 0.05). Lysozyme individually and in combination with nisin had no inhibitory effect on Cl. sporogenes. Overall, the addition of sorbate and lysozyme may allow the salt concentration to be reduced while preventing growth.  相似文献   
56.
57.
58.
Infrastructure for fuel-cell and other alternative-fuel vehicles is lacking not only in the paucity of fuel stations, but also in inadequate web-based support to help drivers complete their trips via the few stations that do exist. In this paper, we present an online mapping tool for finding the shortest feasible path in a road network given the vehicle's driving range and station locations. Users input their origin, destination, type of fuel, and driving range, and the algorithm generates a new reduced feasible network in which the vertices are the origin and destination nodes and reachable fuel stations and the edges represent feasible paths between them. Dijkstra's shortest path algorithm is applied to this reduced network to find the shortest feasible path. Efficiency is substantially improved by preprocessing and storing the shortest-path distances between stations. We present a web-mapping prototype (www.afvrouting.com) for hydrogen and compressed natural gas stations in the United States. Sample results illustrate the need for this kind of globally optimal solution method by showing that the optimal feasible path and refueling stops can vary tremendously as a result of user inputs for driving range, initial tank level, and one-way or round-trip.  相似文献   
59.
The extractable, protein-bound and fibre-bound condensed tannin (CT) concentrations in the leaves of tropical legumes grown in both Colombia and Northern Australia were determined by the butanol–HCl method, whilst extractable CT was also determined by the vanillin–HCl method. With the exception of Senna siamea all species contained CT. The very high CT concentration found in many plants growing in Colombia may have been partly due to soil fertility being much lower at the Colombian than the Northern Australian site. Acacia boliviana , Arachis pintoi , Centrosema latidens , Senna velutina and Gliricidia sepium contained <55 g total CT kg−1 DM, which suggests that they could comprise a reasonable proportion of ruminant diets. All other species grown in South America contained 100–240 g CT kg−1 DM, which suggests that they should only be fed in small amounts as supplements to dilute the CT concentration. Leucaena species and Calliandra calothyrsus grown in Northern Australia contained intermediate concentrations of total CT (60–90 g kg−1 DM). Most species contained 70–95% of total CT as extractable CT, with the exception of Flemingia macrophylla , where 60% was extractable and 40% bound, and Gliricidia sepium , where almost all the CT was bound to protein. Values for Flemingia macrophylla differed between accessions. Extractable CT determined with vanillin–HCl was generally higher than extractable CT determined with butanol–HCl. Three accessions showed negligible (<1 g kg−1 DM) extractable CT with butanol–HCl but 10–12 g extractable CT kg−1 DM with vanillin–HCl. Two accessions showed undetectable levels of extractable CT but substantial levels of protein-bound CT, illustrating the importance of using a bound CT method for identifying forages containing CT. Relative to freeze drying, oven drying of Leucaena species reduced the concentration of extractable CT and increased concentrations of bound CT. The significance of the results for the nutrition of ruminant livestock are discussed, including the possible roles of protein-bound and fibre-bound CT.  相似文献   
60.
One-quarter of patients with acute decompensated heart failure (ADHF) experience acute kidney injury (AKI)—an abrupt reduction or loss of kidney function associated with increased long-term mortality. There is a critical need to identify early and real-time markers of AKI in ADHF; however, to date, no protein biomarkers have exhibited sufficient diagnostic or prognostic performance for widespread clinical uptake. We aimed to identify novel protein biomarkers of AKI associated with ADHF by quantifying changes in protein abundance in the kidneys that occur during ADHF development and recovery in an ovine model. Relative quantitative protein profiling was performed using sequential window acquisition of all theoretical fragment ion spectra–mass spectrometry (SWATH–MS) in kidney cortices from control sheep (n = 5), sheep with established rapid-pacing-induced ADHF (n = 8), and sheep after ~4 weeks recovery from ADHF (n = 7). Of the 790 proteins quantified, we identified 17 candidate kidney injury markers in ADHF, 1 potential kidney marker of ADHF recovery, and 2 potential markers of long-term renal impairment (differential abundance between groups of 1.2–2.6-fold, adjusted p < 0.05). Among these 20 candidate protein markers of kidney injury were 6 candidates supported by existing evidence and 14 novel candidates not previously implicated in AKI. Proteins of differential abundance were enriched in pro-inflammatory signalling pathways: glycoprotein VI (activated during ADHF development; adjusted p < 0.01) and acute phase response (repressed during recovery from ADHF; adjusted p < 0.01). New biomarkers for the early detection of AKI in ADHF may help us to evaluate effective treatment strategies to prevent mortality and improve outcomes for patients.  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