全文获取类型
收费全文 | 602888篇 |
免费 | 9334篇 |
国内免费 | 1787篇 |
专业分类
电工技术 | 10609篇 |
综合类 | 478篇 |
化学工业 | 93657篇 |
金属工艺 | 25822篇 |
机械仪表 | 22423篇 |
建筑科学 | 14765篇 |
矿业工程 | 2977篇 |
能源动力 | 15447篇 |
轻工业 | 52928篇 |
水利工程 | 6036篇 |
石油天然气 | 9985篇 |
武器工业 | 23篇 |
无线电 | 71745篇 |
一般工业技术 | 120277篇 |
冶金工业 | 98703篇 |
原子能技术 | 11538篇 |
自动化技术 | 56596篇 |
出版年
2021年 | 5076篇 |
2020年 | 3811篇 |
2019年 | 4486篇 |
2018年 | 14272篇 |
2017年 | 14791篇 |
2016年 | 11928篇 |
2015年 | 5981篇 |
2014年 | 9359篇 |
2013年 | 25041篇 |
2012年 | 17601篇 |
2011年 | 27873篇 |
2010年 | 23093篇 |
2009年 | 23986篇 |
2008年 | 24205篇 |
2007年 | 25168篇 |
2006年 | 16481篇 |
2005年 | 17995篇 |
2004年 | 15791篇 |
2003年 | 15193篇 |
2002年 | 13895篇 |
2001年 | 13361篇 |
2000年 | 12370篇 |
1999年 | 12735篇 |
1998年 | 29704篇 |
1997年 | 21168篇 |
1996年 | 16475篇 |
1995年 | 12447篇 |
1994年 | 10995篇 |
1993年 | 10786篇 |
1992年 | 8058篇 |
1991年 | 7772篇 |
1990年 | 7433篇 |
1989年 | 7320篇 |
1988年 | 7106篇 |
1987年 | 5893篇 |
1986年 | 5774篇 |
1985年 | 6924篇 |
1984年 | 6409篇 |
1983年 | 5807篇 |
1982年 | 5432篇 |
1981年 | 5591篇 |
1980年 | 5303篇 |
1979年 | 5111篇 |
1978年 | 5040篇 |
1977年 | 5796篇 |
1976年 | 7415篇 |
1975年 | 4496篇 |
1974年 | 4285篇 |
1973年 | 4325篇 |
1972年 | 3627篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
93.
94.
95.
Yachao Dong Christos T. Maravelias Norman F. Jerome 《Optimization and Engineering》2018,19(4):937-976
We study a maritime inventory routing problem, in which shipments between production and consumption nodes are carried out by a fleet of vessels. The vessels have specific capacities and can be chartered under different agreements. The inventory levels of all consumption nodes and some production nodes should be maintained within specified bounds; for the remaining production nodes, orders should be picked up within pre-defined time windows. We propose a discrete-time mixed-integer programming model. In the face of new information and uncertainty, this optimization model has to be re-solved, as the horizon is rolled forward. We discuss how to account for different sources of uncertainty. We present a rolling-horizon reoptimization framework that allows us to study different policies that impact the quality of the implemented solution, so we can identify the optimal set of policies. 相似文献
96.
Seong‐Hee Kim 《Quality and Reliability Engineering International》2015,31(6):923-934
We present a distribution‐free tabular cumulative sum chart for monitoring the variability of an autocorrelated process. A quantity known as the asymptotic variance parameter is employed as a measure of the variability, and a distribution‐free tabular cumulative sum chart is applied to variance estimates calculated from batches of nonoverlapping samples. The proposed chart is applicable to a stationary process with a general marginal distribution and a general autocorrelation structure. It also determines control limits analytically without trial‐and‐error simulations. The performance of the proposed chart is tested on stationary processes with both normal and nonnormal marginals with various autocorrelation structures. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
97.
A new constitutive equation of thermoelasticity for crystals is presented based on the interatomic potential and solid mechanics at finite temperature. Using the new constitutive equation, the calculations for crystal copper and graphene are carried out under different loading paths at different temperatures. The calculated results are in good agreement with those of the previous thermoelasticity constitutive equation based on quantum mechanics, which clearly indicates that our new constitutive equation of thermoelasticity is correct. A lot of comparisons also show that the present theory is more concise and efficient than the previous thermal stress theory in the practical application. 相似文献
98.
99.
J Comas I Rodríguez-Roda M Poch K V Gernaey C Rosen U Jeppsson 《Water science and technology》2006,53(4-5):303-311
Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance. 相似文献
100.
This report compares the enterococci count on samples obtained with Azide NutriDisk (AND) (sterile, dehydrated culture medium) and Slanetz and Bartley (SB) medium when exposed to a variable in incubation time and temperature. Three experiments were performed to examine the recovery of enterococci on AND and SB media using membrane filtration with respect to: (a) incubation time; (b) incubation temperature; and (c) a combination of the two. Presumptive counts were observed at 37, 41, 46 and 47 degrees C and at 20, 24, 28 and 48 h. These were compared to AWWA standard method 9230 C (44 degrees C, 44 h). Samples were confirmed using Kanamycin Aesculin Azide (KAA) agar. Friedman's ANOVA and Students t-test analysis indicated higher enumeration of enterococci when grown on AND (p = 0.45) than SB (p = < 0.001) at all temperatures with a survival threshold at 47 degrees C. Significant results for AND medium were noted at 20 h (p = 0.021), 24 h (p = 0.278) and 28 h (p = 0.543). The study concluded that the accuracy of the AND medium at a greater time and temperature range provided flexibility in incubator technology making it an appropriate alternative to SB medium for monitoring drinking water using field testing kits in developing countries. 相似文献