全文获取类型
收费全文 | 12617篇 |
免费 | 1172篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 129篇 |
综合类 | 8篇 |
化学工业 | 3152篇 |
金属工艺 | 176篇 |
机械仪表 | 386篇 |
建筑科学 | 584篇 |
矿业工程 | 29篇 |
能源动力 | 329篇 |
轻工业 | 2415篇 |
水利工程 | 94篇 |
石油天然气 | 22篇 |
无线电 | 879篇 |
一般工业技术 | 2464篇 |
冶金工业 | 877篇 |
原子能技术 | 46篇 |
自动化技术 | 2213篇 |
出版年
2024年 | 40篇 |
2023年 | 168篇 |
2022年 | 155篇 |
2021年 | 397篇 |
2020年 | 344篇 |
2019年 | 344篇 |
2018年 | 479篇 |
2017年 | 491篇 |
2016年 | 613篇 |
2015年 | 506篇 |
2014年 | 677篇 |
2013年 | 1240篇 |
2012年 | 1068篇 |
2011年 | 919篇 |
2010年 | 651篇 |
2009年 | 634篇 |
2008年 | 684篇 |
2007年 | 600篇 |
2006年 | 548篇 |
2005年 | 392篇 |
2004年 | 328篇 |
2003年 | 311篇 |
2002年 | 273篇 |
2001年 | 188篇 |
2000年 | 160篇 |
1999年 | 134篇 |
1998年 | 192篇 |
1997年 | 157篇 |
1996年 | 113篇 |
1995年 | 112篇 |
1994年 | 95篇 |
1993年 | 89篇 |
1992年 | 56篇 |
1991年 | 44篇 |
1990年 | 36篇 |
1989年 | 39篇 |
1988年 | 43篇 |
1987年 | 34篇 |
1986年 | 33篇 |
1985年 | 42篇 |
1984年 | 34篇 |
1983年 | 31篇 |
1982年 | 34篇 |
1981年 | 28篇 |
1980年 | 22篇 |
1979年 | 30篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1976年 | 22篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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
102.
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
103.
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
104.
A note on the min-max formulation of stiffness optimization including non-zero prescribed displacements 总被引:1,自引:0,他引:1
The present theoretical note shows how a natural objective function in stiffness optimization, including both prescribed forces
and non-zero prescribed displacements, is the equilibrium potential energy. It also shows how the resulting problem has a
saddle point character that may be utilized when calculating sensitivities. 相似文献
105.
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
106.
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
107.
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
108.
109.
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
110.
Katarzyna Jasieniecka-Gazarkiewicz Kamil Demski Satinder K. Gidda Sylwia Kliska Janusz Niedojado Ida Lager Anders S. Carlsson Elena A. Minina Robert T. Mullen Peter V. Bozhkov Sten Stymne Antoni Bana 《International journal of molecular sciences》2021,22(6)
Arabidopsis thaliana possesses two acyl-CoA:lysophosphatidylethanolamine acyltransferases, LPEAT1 and LPEAT2, which are encoded by At1g80950 and At2g45670 genes, respectively. Both single lpeat2 mutant and double lpeat1 lpeat2 mutant plants exhibit a variety of conspicuous phenotypes, including dwarfed growth. Confocal microscopic analysis of tobacco suspension-cultured cells transiently transformed with green fluorescent protein-tagged versions of LPEAT1 or LPEAT2 revealed that LPEAT1 is localized to the endoplasmic reticulum (ER), whereas LPEAT2 is localized to both Golgi and late endosomes. Considering that the primary product of the reaction catalyzed by LPEATs is phosphatidylethanolamine, which is known to be covalently conjugated with autophagy-related protein ATG8 during a key step of the formation of autophagosomes, we investigated the requirements for LPEATs to engage in autophagic activity in Arabidopsis. Knocking out of either or both LPEAT genes led to enhanced accumulation of the autophagic adaptor protein NBR1 and decreased levels of both ATG8a mRNA and total ATG8 protein. Moreover, we detected significantly fewer membrane objects in the vacuoles of lpeat1 lpeat2 double mutant mesophyll cells than in vacuoles of control plants. However, contrary to what has been reported on autophagy deficient plants, the lpeat mutants displayed a prolonged life span compared to wild type, including delayed senescence. 相似文献