全文获取类型
收费全文 | 11082篇 |
免费 | 1112篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 100篇 |
综合类 | 6篇 |
化学工业 | 2738篇 |
金属工艺 | 138篇 |
机械仪表 | 346篇 |
建筑科学 | 500篇 |
矿业工程 | 26篇 |
能源动力 | 251篇 |
轻工业 | 2240篇 |
水利工程 | 84篇 |
石油天然气 | 20篇 |
无线电 | 823篇 |
一般工业技术 | 2219篇 |
冶金工业 | 747篇 |
原子能技术 | 31篇 |
自动化技术 | 1938篇 |
出版年
2024年 | 32篇 |
2023年 | 162篇 |
2022年 | 137篇 |
2021年 | 369篇 |
2020年 | 319篇 |
2019年 | 312篇 |
2018年 | 444篇 |
2017年 | 460篇 |
2016年 | 564篇 |
2015年 | 478篇 |
2014年 | 618篇 |
2013年 | 1136篇 |
2012年 | 990篇 |
2011年 | 782篇 |
2010年 | 576篇 |
2009年 | 557篇 |
2008年 | 594篇 |
2007年 | 520篇 |
2006年 | 465篇 |
2005年 | 311篇 |
2004年 | 279篇 |
2003年 | 251篇 |
2002年 | 248篇 |
2001年 | 150篇 |
2000年 | 130篇 |
1999年 | 117篇 |
1998年 | 165篇 |
1997年 | 133篇 |
1996年 | 103篇 |
1995年 | 95篇 |
1994年 | 86篇 |
1993年 | 77篇 |
1992年 | 54篇 |
1991年 | 39篇 |
1990年 | 26篇 |
1989年 | 27篇 |
1988年 | 32篇 |
1987年 | 21篇 |
1986年 | 26篇 |
1985年 | 34篇 |
1984年 | 28篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 18篇 |
1979年 | 24篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 17篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
René Schneider 《Computing and Visualization in Science》2012,15(5):247-270
Adaptive anisotropic refinement of finite element meshes allows one to reduce the computational effort required to achieve a specified accuracy of the solution of a PDE problem. We present a new approach to adaptive refinement and demonstrate that this allows one to construct algorithms which generate very flexible and efficient anisotropically refined meshes, even improving the convergence order compared to adaptive isotropic refinement if the problem permits. 相似文献
92.
Alexandre Petrenko Adenilso Simao José Carlos Maldonado 《International Journal on Software Tools for Technology Transfer (STTT)》2012,14(4):383-386
Model-based testing is focused on testing techniques which rely on the use of models. The diversity of systems and software to be tested implies the need for research on a variety of models and methods for test automation. We briefly review this research area and introduce several papers selected from the 22nd International Conference on Testing Software and Systems (ICTSS). 相似文献
93.
José M. Cecilia José M. García Ginés D. Guerrero Miguel A. Martínez-del-Amor Mario J. Pérez-Jiménez Manuel Ujaldón 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(2):231-246
Membrane Computing is a discipline aiming to abstract formal computing models, called membrane systems or P systems, from the structure and functioning of the living cells as well as from the cooperation of cells in tissues, organs, and
other higher order structures. This framework provides polynomial time solutions to NP-complete problems by trading space
for time, and whose efficient simulation poses challenges in three different aspects: an intrinsic massively parallelism of
P systems, an exponential computational workspace, and a non-intensive floating point nature. In this paper, we analyze the
simulation of a family of recognizer P systems with active membranes that solves the Satisfiability problem in linear time
on different instances of Graphics Processing Units (GPUs). For an efficient handling of the exponential workspace created
by the P systems computation, we enable different data policies to increase memory bandwidth and exploit data locality through
tiling and dynamic queues. Parallelism inherent to the target P system is also managed to demonstrate that GPUs offer a valid
alternative for high-performance computing at a considerably lower cost. Furthermore, scalability is demonstrated on the way
to the largest problem size we were able to run, and considering the new hardware generation from Nvidia, Fermi, for a total
speed-up exceeding four orders of magnitude when running our simulations on the Tesla S2050 server. 相似文献
94.
We discuss how the standard Cost-Benefit Analysis should be modified in order to take risk (and uncertainty) into account. We propose different approaches used in finance (Value at Risk, Conditional Value at Risk, Downside Risk Measures, and Efficiency Ratio) as useful tools to model the impact of risk in project evaluation. After introducing the concepts, we show how they could be used in CBA and provide some simple examples to illustrate how such concepts can be applied to evaluate the desirability of a new project infrastructure. 相似文献
95.
An assessment was made of the microbiological quality of the final product (different retail cuts), produced by two different retail supermarket groups (A & B). The influence of sanitary conditions on the microbiological quality of the final product was evaluated, and the possible influences on shelf life were determined. Supermarket group A (Sup group A) received carcasses with significantly lower surface counts of micro-organisms than supermarket group B (Sup group B), while the latter had a more efficient overall sanitation programme than supermarket group A. Five cuts were monitored for the presence of total aerobic counts, psychrotrophic counts, lactobacilli, Enterobacteriaceae and numbers of Pseudomonadaceae present. A shelf life study was also executed by repeating these enumerations on the same meat samples after refrigerated storage at 5°C for 2 and 4 days, respectively. It is generally accepted that a good refrigeration or chilling regime will preserve the inherent meat quality, but in this study it was found that neither served as a guarantee of quality. The more stringent hygiene at retail level of Sup group B yielded consistently lower mean counts of the different bacterial groups for all the meat cuts monitored and, thus meat with an extended shelf life. The total count (at 30°C) on meat cuts was the highest, followed by the psychrotrophs, the Pseudomonadaceae the Enterobacteriaeae and the lactobacilli. Minced meat generally had the highest mean aerobic total microbial counts. This count on minced meat might be a suitable indicator for monitoring the overall sanitary condition of a retail premises. The results re-emphasized the multi-factorial complexity of fresh meat quality and shelf life. The microbial quality of the raw material (carcasses), the maintenance of the cold chain, sanitary condition of premises, equipment and personnel surfaces and general management practices are factors that collectively determine the microbiological quality of the product. 相似文献
96.
T. Sekiya A. Tzuzuki S. Kawakami Y. Torii N. Tsuboi T. Futakuchi 《Journal of Materials Science》1988,23(9):3300-3304
The rapidly quenched films in the Bi2O3-TiO2 system (0 to 60% TiO2) were prepared using a twin-roller type apparatus. The films precipitated Bi2O3 solid solutions of different types in the composition ranges, with TiO2 contents of 0 to 5, 7.5 to 10 and 12.5 to 40%, respectively. The first solid solution had a tetragonal structure of -form. The second, though also crystallized in the tetragonal structure, adopted a disordered modification of the -form. The third solid solution was -form (defect fluorite structure). The formation of amorphous phase commenced in the composition with 30% TiO2, and the films became completely amorphous beyond 50% TiO2. The quenched films showed a certain instability to decompose or transform into the different phase assemblage by annealing at higher temperatures (about 400 to 500° C, except 260° C for the pure Bi2O3 film). The quenched films were also characterized by a high photoconductivity. The photoconduction mechanism was suggested to be associated with a structural imperfection of Bi2O3 accompanied by a certain amount of pentavalent bismuth ion. 相似文献
97.
The influence of different centralised pre-packaging systems (PVC, modified atmosphere packaging (MAP), 25% CO(2) and 75% O(2), vacuum skin packaging (VSP) and the mother bag concept, 100% CO(2)) on the shelf-life (0, 7, 14 and 21 days at 0°C) of fresh pork was determined using microbiological, colour, odour and acceptability characteristics. All the packaging treatments were equally efficient for the first 4 days of retail display. In the extended shelf-life study (7, 14 and 21 days) the mother bag centralised packaging system gave the most promising shelf-life results (21 days) and was also judged superior in terms of odour. Modified atmosphere packaging (14 days) and VSP (7 days) may be considered as other possible options. 相似文献
98.
This study attempted to identify the major sources of work-related stress among telephone operators, with special emphasis on computer monitoring and telephone surveillance. A cross-sectional random sample of over 700 telephone operators participated in a questionnaire survey (response rate = 88%). The survey included items designed to measure perceived stress, management practices, specific job stressors and monitoring preferences. Call-time pressure items were most strongly linked to job stress by operators, with 70% reporting that difficulty in serving a customer well and still keeping call-time down contributed to their feelings of stress to a large or very large extent. About 55% of operators reported that telephone monitoring contributed to their feelings of job stress. If given the opportunity, 44% of operators stated they would prefer not to be monitored by telephone at all, while 23% stated they would prefer some monitoring; 33% had no preference. The setting of inappropriate individual-call-time objectives, which may be consistently unachievable for some operators and which create conflict between management demands for quantity and quality and also between workers values concerning quality and productivity demands, appears to be the most stress-inducing aspect of the job. In terms of telephone surveillance, the issues of timeliness and specificity of feedback appear to be less important than call-time pressure. 相似文献
99.
100.
Sápi András Rajkumar T. Kiss János Kukovecz Ákos Kónya Zoltán Somorjai Gabor A. 《Catalysis Letters》2021,151(8):2153-2175
Catalysis Letters - Heterogeneous catalysis is a chemical process achieved at solid–gas or solid–liquid interfaces. Many factors including the particle size, shape and metal-support... 相似文献