全文获取类型
收费全文 | 412篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 108篇 |
金属工艺 | 9篇 |
机械仪表 | 19篇 |
建筑科学 | 22篇 |
能源动力 | 10篇 |
轻工业 | 24篇 |
石油天然气 | 1篇 |
无线电 | 30篇 |
一般工业技术 | 75篇 |
冶金工业 | 68篇 |
原子能技术 | 5篇 |
自动化技术 | 45篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 20篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 22篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 24篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 4篇 |
1967年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有425条查询结果,搜索用时 93 毫秒
1.
The aditi deductive database system 总被引:2,自引:0,他引:2
Jayen Vaghanl BSc Kotagiri Ramamohanarao Ph.D. David B. Kemp Ph.D. Zoltan Somogyi Ph.D. Peter J. Stuckey Ph.D. Tim S. Leask BSc James Harland Ph.D. 《The VLDB Journal The International Journal on Very Large Data Bases》1994,3(2):245-288
Deductive databases generalize relational databases by providing support for recursive views and non-atomic data. Aditi is a deductive system based on the client-server model; it is inherently multi-user and capable of exploiting parallelism on shared-memory multiprocessors. The back-end uses relational technology for efficiency in the management of disk-based data and uses optimization algorithms especially developed for the bottom-up evaluation of logical queries involving recursion. The front-end interacts with the user in a logical language that has more expressive power than relational query languages. We present the structure of Aditi, discuss its components in some detail, and present performance figures. 相似文献
2.
Repetitive cyclic loading of a nerve has been proposed as a pathogenic factor in the development of occupational compression neuropathies. Little is known about the basic response of peripheral nerve to cyclic compression. We investigated the hypothesis that cyclic compression is more detrimental to nerve function than constant compression. We measured the amplitudes and velocities of distally evoked action potentials in the presence of constant or cyclic compression of the tibial nerve in rats. Seven groups were subjected to constant or cyclic compression for 6 h by a computer controlled, hydraulically activated compression chamber. Nerves were compressed with 0 (control group), 30, 60, or 90 mm Hg of constant pressure or 0-30, 20-50, or 30-60 mm Hg of cyclic compression for approximately 20,000 compression cycles. Action potentials were recorded every 15 min. The effects of cyclic compression on nerve conduction were equivalent to the effects of constant compression at the average applied pressure. Cyclic loading itself does not appear to be an important pathogenic factor in the development of nerve conduction block. 相似文献
3.
T Peelen M van Vliet A Petrij-Bosch R Mieremet C Szabo AM van den Ouweland F Hogervorst R Brohet MJ Ligtenberg E Teugels R van der Luijt AH van der Hout JJ Gille G Pals I Jedema R Olmer I van Leeuwen B Newman M Plandsoen M van der Est G Brink S Hageman PJ Arts MM Bakker P Devilee 《Canadian Metallurgical Quarterly》1997,60(5):1041-1049
We have identified 79 mutations in BRCA1 in a set of 643 Dutch and 23 Belgian hereditary breast and ovarian cancer families collected either for research or for clinical diagnostic purposes. Twenty-eight distinct mutations have been observed, 18 of them not previously reported and 12 of them occurring more than once. Most conspicuously, a 2804delAA mutation has been found 19 times and has never been reported outside the Netherlands. A common haplotype spanning > or = 375 kb could be identified for each of the nine examined recurrent mutations, indicating the presence of multiple BRCA1 founder mutations in the Dutch population. The 2804delAA mutation has been estimated to have originated approximately 32 generations ago. No specific breast or ovarian cancer phenotype could be assigned to any of the common mutations, and the ovarian cancer incidence among 18 families with the 2804delAA mutation was heterogeneous. 相似文献
4.
5.
Evolutionary multiobjective optimization for base station transmitter placement with frequency assignment 总被引:2,自引:0,他引:2
Weicker N. Szabo G. Weicker K. Widmayer P. 《Evolutionary Computation, IEEE Transactions on》2003,7(2):189-203
We propose a new solution to the problem of positioning base station transmitters of a mobile phone network and assigning frequencies to the transmitters, both in an optimal way. Since an exact solution cannot be expected to run in polynomial time for all interesting versions of this problem (they are all NP-hard), our algorithm follows a heuristic approach based on the evolutionary paradigm. For this evolution to be efficient, i.e., goal-oriented and sufficiently random at the same time, problem-specific knowledge is embedded in the operators. The problem requires both the minimization of the cost and of the channel interference. We examine and compare two standard multiobjective techniques and a new algorithm - the steady-state evolutionary algorithm with Pareto tournaments. One major finding of the empirical investigation is a strong influence of the choice of the multiobjective selection method on the utility of the problem-specific recombination leading to a significant difference in the solution quality. 相似文献
6.
The paper demonstrates the use of nonresistive secondary control of an induction motor to improve efficiency, power factor and torque. A mathematical algorithm is presented to predict the control requirements in terms of secondary capacitance. The required secondary capacitance is implemented by a novel electronic switching technique that effectively increases the value of the used capacitor. This overcomes the high-capacitance demand and provides a feasible solution. Experimental verification is presented in the results obtained from a small induction motor drive 相似文献
7.
Dora Szabo Zsolt Sarszegi Beata Polgar Eva Saghy Adam Nemeth Dora Reglodi Andras Makkos Aniko Gorbe Zsuzsanna Helyes Peter Ferdinandy Robert Herczeg Attila Gyenesei Attila Cziraki Andrea Tamas 《International journal of molecular sciences》2021,22(6)
Acute myocardial infarction (MI) is one of the most common causes of death worldwide. Pituitary adenylate cyclase activating polypeptide (PACAP) is a cardioprotective neuropeptide expressing its receptors in the cardiovascular system. The aim of our study was to examine tissue PACAP-38 in a translational porcine MI model and plasma PACAP-38 levels in patients with ST-segment elevation myocardial infarction (STEMI). Significantly lower PACAP-38 levels were detected in the non-ischemic region of the left ventricle (LV) in MI heart compared to the ischemic region of MI-LV and also to the Sham-operated LV in porcine MI model. In STEMI patients, plasma PACAP-38 level was significantly higher before percutaneous coronary intervention (PCI) compared to controls, and decreased after PCI. Significant negative correlation was found between plasma PACAP-38 and troponin levels. Furthermore, a significant effect was revealed between plasma PACAP-38, hypertension and HbA1c levels. This was the first study showing significant changes in cardiac tissue PACAP levels in a porcine MI model and plasma PACAP levels in STEMI patients. These results suggest that PACAP, due to its cardioprotective effects, may play a regulatory role in MI and could be a potential biomarker or drug target in MI. 相似文献
8.
Mucsi Zoltan; Gaspari Zoltan; Orosz Gyorgy; Perczel Andras 《Protein engineering, design & selection : PEDS》2003,16(9):673-681
Three peptides modelling a highly potent, 35-residue chymotrypsininhibitor (Schistocerca gregaria chymotrypsin inhibitor) weredesigned and synthesized by convergent peptide synthesis. Foreach model peptide, the inhibitory constant (Ki) on chymotrypsinand the solution structure were determined. In addition, moleculardynamics calculations were performed for all of them. Two modelscontaining approximately half of the parent inhibitor (17 of35 residues) were designed and subsequently found to have nosubstantial inhibitory activity (Ki values in the mM range).The third model composed of 24 amino acid residues proved tobe an effective (Ki 107) inhibitor of bovine chymotrypsin.Both the solution structure properties determined by NMR spectroscopyand the dynamic behaviour of the latter model system are comparableto the native inhibitor. In contrast, the structure and dynamicsof the first two related model peptides show characteristicdifferences. We suggest that the conformation and flexibilityof the modelled protease inhibitor are crucial for its biologicalefficiency. Moreover, the structural and dynamic features ofthe binding loop (2833) and those of the rest of themolecule appear to be interdependent. Most importantly, thesestructural characteristics can be rationally modified, at leastpartially, by peptide design. Received March 7, 2003; revised August 25, 2003; accepted August 26, 2003. 相似文献
9.
Addition of adenosine triphosphate (ATP) to [14C]ethanolamine-prelabeled NIH 3T3 fibroblasts resulted in rapid formation of [14C]ethanolamine from the prelabeled cellular phosphatidylethanolamine (PtdEtn) pool. After 2-min exposure, 10 μM ATP had near
maximal effects on PtdEtn hydrolysis. Several other nucleotides, including UTP, ITP, and the stable ATP analog adenosine 5′-O-(3-thiotriphosphate) (ATPγS), also had stimulatory effects on PtdEtn hydrolysis with a potency comparable to that observed
with ATP. The same nucleotides which acted on PtdEtn hydrolysis also had similar stimulatory effects on the hydrolysis of
phosphatidylcholine (PtdCho) in [14C]choline-labeled cells. In isolated membranes, Mg2+ greatly enhanced the stimulatory effects of ATP and ATPγS, but not of other nucleotides, on the hydrolysis of PtdEtn and
PtdCho. Results indicate that in isolated membranes, both ATP and ATPγS stimulate phospholipid hydrolysis by two different
mechanisms, but in intact cells only one of these mechanisms appears to be responsive to externally added nucleotides. 相似文献
10.
Z. Benzo T. Zoltan M. Murillo M. Quintal J. Salas E. Marcano C. Gómez 《Journal of the American Oil Chemists' Society》2006,83(5):401-405
An emulsion-based method was developed as an alternative for the introduction of oil-based samples into a graphite furnace
to produce a more rapid, precise, and accurate method of analysis. The combination of emulsion sampling and electrothermal
atomization for atomic absorption spectroscopy was developed and then applied to the determination of Ni and manganese in
neem oil from Venezuela. The optimal concentration of neem oil in the emulsion was 30 and 4% for Ni and Mn, respectively,
based on the metal concentration of the neem oil. The stability of the emulsion as a function of time was evaluated. The use
of aqueous calibration solutions and the accuracy attained using this method make it attractive for the analysis of oil samples.
The metal recovery was between 97 and 101%. Based on the emulsion method, the neem oil samples had 1.39 and 0.21 mg of Mn
and Ni per kg of oil, respectively. The wet digestion method indicated a Mn and Ni concentration in the neem oil sample of
1.42 and 0.24 mg/kg, respectively. 相似文献