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排序方式: 共有715条查询结果,搜索用时 31 毫秒
41.
This experimental study focuses on generation and control of annular impinging jets. The annular nozzle used in the investigations was designed with an active flow control system using 12 synthetic jets issuing radially from the central nozzle body. Measurements of the control effects were made on the impingement wall. The data acquisition involved wall pressure and wall mass transfer (by the naphthalene sublimation technique) using air as the working fluid. Also measured was time-mean flow velocity (by a Pitot probe) in the jet flow field. Moreover, flow visualization was carried out. Two main flow-field patterns (A and B) were identified. The patterns differ in the size of the separated-flow recirculation regions that develop attached to the nozzle central body: While pattern A is characterized by a quite small recirculation region (bubble) extending not far from the nozzle exit, pattern B exhibits a large recirculation region, reaching up to the impingement wall, on which it forms a stagnation circle. The control action modifies the flow field, resulting in changes of the corresponding heat/mass transfer distributions. The convective transfer rate on the stagnation circle can be demonstrably enhanced by 20% at a moderate nozzle-to-wall distance, equal to 0.6 of the nozzle outer diameter. 相似文献
42.
Meinald T. Thielsch Lisa Tr?umer Leoni Pytlik 《Information Technology and Management》2012,13(2):59-67
More and more companies currently recruit online, partly because of cost savings and competitive pressure, and partly because
it is the best way to reach their target group of applicants. In our study, applicants’ perceptions of procedural fairness
were examined in e-recruiting contexts. Using an adapted form of the Social Process Questionnaire on Selection, we found that
1,373 participants’ expectations regarding fairness were mediocre and always lower than the perceived importance of five procedural
fairness aspects. Based on an experimental manipulation, we showed that feedback was particularly important in online application
procedures, whereas participation had smaller effects. Furthermore, participants tend to rate procedural fairness for offline
application procedures as fairer than for online procedures although they reported generally positive experiences with online
applications in the past. Based on our results, we discuss practical implications and limitations. 相似文献
43.
Ferreira NC Trébossen R Comtat C Grégoire MC Bendriem B 《IEEE transactions on medical imaging》2000,19(5):485-492
The calculation of the intrinsic efficiency of individual crystals is one of the steps needed to obtain accurate images of the radioisotope distribution in positron emission tomography (PET). These efficiencies can be computed by comparing the number of coincidence counts obtained when the crystals are equally illuminated by the same source. However, because the number of coincidence counts acquired for one crystal also depends on the efficiency of the other crystals in coincidence, most methods of crystal efficiency calculation need to assume that the influence of the other crystals is negligible. If there are large crystal efficiency variations, this approximation may lead to systematic errors. We have recently implemented an iterative method for a single ring of detectors that does not rely on this assumption. In this paper, we describe a fully three-dimensional (3-D) iterative method that better exploits the sensitivity of the tomograph and allows reduced acquisition times or the use of narrow energy windows. We compare the performance of the iterative method (single-ring and extended to fully 3-D) with noniterative techniques for different acquisition times of a uniform cylinder. Two different energy windows were used to assess the performance of each method with different levels of variations of crystal efficiency. The results showed that the iterative methods are more accurate when large efficiency variations exist and that only the fully 3-D methods provided good efficiency estimates with very low duration scans. We, thus, conclude that iterative fully 3-D methods provide the best estimations and can be used in a larger range of situations than can the other methods tested. 相似文献
44.
E. Träbert 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1985,9(4):626-629
The term values of 2s22p53l and 2s2p63l levels have been derived from an analysis of the EUV spectrum of foil-excited titanium ions. The results are graphically compared with several theoretical calculations. The comparison with isoelectronic data up to Ar8+ shows several changes in the sequence of levels between argon and titanium. 相似文献
45.
KE Lyons R Pahwa KL Busenbark AI Tr?ster S Wilkinson WC Koller 《Canadian Metallurgical Quarterly》1998,13(4):690-692
Deep brain stimulation (DBS) of the thalamus reduces tremor in patients with essential tremor (ET). However, few studies have determined the degree of improvement in daily functioning associated with DBS. We developed a self-report Tremor Activities of Daily Living Scale (TADLS) to compare daily functioning with the stimulator turned on and off. Patients rated their performance on the 30 items of the TADLS with the stimulator turned off and then on. They also performed 10 activities under the supervision of a clinician who rated their functional ability with stimulation off and then on. There was a 58% improvement in self-rated TADLS scores in patients with DBS with the stimulator on compared with stimulation off. When activities were rated by the clinician, the average improvement in functioning with the stimulator on was 54%. There were reasonably high correlations between patient and clinician ratings of functioning. ET patients have a marked improvement in daily functioning with thalamic DBS. 相似文献
46.
B Trümpi 《Canadian Metallurgical Quarterly》1976,131(4):305-360
Biochemical properties of the crystalline delta-endotoxin of Bacillus thuringiensis, such as stability and solubility in different solvents, were investigated. The dissolved compounds were characterized by gel-electrophoresis and gel-filtration. Covalent and non-covalent bonds are responsible for the crystallisation of the protein molecules. The solubilisation of crystals with non-enzymatic solvents led to high molecular weight products (MW greater than or equal to 800,000) and to components with a molecular weight less than or equal to 10,000. Only the high molecular weight compounds showed toxic activity. The enzymatic degradation of the protein crystals yielded components with molecular weights of greater than or equal to 800,000, 250,000, 100,000, and less than or equal to 10,000. Again, the fraction less than or equal to 10,000 showed no toxic activity. Digestion of the crystals with proteases isolated from the gut juice of Pieris brassicae resulted in a highly toxic fraction with a molecular weight of 100,000. This component, which is resistant to further degradation, appears to be the toxic unit of the protein crystal. 相似文献
47.
Raddatz S Marcello M Kliem HC Tröster H Trendelenburg MF Oeser T Granzow C Wiessler M 《Chembiochem : a European journal of chemical biology》2004,5(4):474-482
The synthesis of a new ortho-carborane derivative, tetracarboranylketone 4, is reported here. Ketone 4 was prepared from a tetraalkynylated ketone by the addition of decaborane. The keto group was then easily modified to yield the glycosides 17alpha and 18beta, which contain glucose or galactose, respectively, and the nucleotide 13b. In addition to ketone 4, which is acyclic, cyclic ketone 8 was also synthesised. X-ray diffraction analysis of compound 4 indicated the presence of two toluene guest molecules per molecule of the host compound. Furthermore, compound 4 displays a rather low cytotoxicity. These novel products can be used as building blocks to create a new class of biomolecules containing high-density carborane clusters. Such molecules may constitute powerful tools for applications like Boron Neutron Capture Therapy or Energy-Filtering Transmission Electron Microscopy. 相似文献
48.
Towards trust management standardization 总被引:4,自引:0,他引:4
Recent research in the field of security has evolved into trust issues, which are now one of the interesting research topics. A majority of current approaches proposes techniques that support users' trust processes, while a minority of them addresses the essence of trust. The latter approaches form the basis for the work presented in this paper. Outer manifestations of trust phenomenon are formalized in order to facilitate the development in this field. The main goal is to provide means for computable trust that can be used in a standardized way for contemporary internet-based applications, independently of its cognitive principles. 相似文献
49.
Information represents one of the most important factors in the success of any enterprise today. Moreover, confidential information is becoming increasingly integrated into complex info-innovation solutions and is accordingly exposed to novel means of manipulation and theft. The legal requirements concerning information security (IS) policies in organizations are mainly based on reactive approaches that follow the standards applied in this area and are regularly updated every few years. However, a complementary approach that takes into account a fast-changing information/innovation security threats landscape and that is of proactive nature is required. Such an approach is presented in this article by linking the information security field with the field of innovation management. 相似文献
50.
F. Bédard G. Reichert R. Dobbins I. Trépanier 《International journal of remote sensing》2013,34(7):2041-2054
This paper describes single‐date and multi‐date land‐cover classification accuracy results using segment‐based, gap‐filled Landsat 7 Enhanced Thematic Mapper data compared with Landsat 5 Thematic Mapper data captured one day apart. Maximum likelihood and Decision tree classification algorithms were evaluated. The same training and verification sets of ground data were used for each classification evaluation. For the comparison with the single‐date classification, an average decrease of 2.8% in the classification accuracy was obtained with the use of the gap‐filled Landsat data. Area estimates for the mid‐summer images differed, on average, from 0.6% to 1.9% for a four‐class and eight‐class classification, respectively. A multi‐date land‐cover classification was also completed with the addition of a late spring Landsat 5 image, resulting in an average decrease in classification accuracy of 1.8%. 相似文献