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排序方式: 共有4520条查询结果,搜索用时 15 毫秒
161.
Carlos Guerra Sarvesh Kumar Fernando Aguilar-Galindo Sergio Díaz-Tendero Ana I. Lozano Mnica Mendes Juan C. Oller Paulo Limo-Vieira Gustavo García 《International journal of molecular sciences》2022,23(3)
In this study, novel experimental total electron detachment cross sections for O2− collisions with benzene molecules are reported for the impact energy range (10–1000 eV), as measured with a transmission beam apparatus. By analysing the positively charged species produced during the collision events, relative total ionisation cross sections were derived in the incident energy range of 160–900 eV. Relative partial ionisation cross sections for fragments with m/z ≤ 78 u were also given in this energy range. We also confirmed that heavier compounds (m/z > 78 u) formed for impact energies between 550 and 800 eV. In order to further our knowledge about the collision dynamics governing the fragmentation of such heavier molecular compounds, we performed molecular dynamics calculations within the framework of the Density Functional Theory (DFT). These results demonstrated that the fragmentation of these heavier compounds strongly supports the experimental evidence of m/z = 39–42, 50, 60 (u) cations formation, which contributed to the broad local maximum in the total ionisation observed from 550 to 800 eV. This work reveals the reactivity induced by molecular anions colliding with hydrocarbons at high energies, processes that can take place in the interstellar medium under various local conditions. 相似文献
162.
Deiweson Souza-Monteiro Mrcia Cristina dos Santos Guerra Leonardo Oliveira Bittencourt Walessa Alana Bragana Arago Aline Dionizio Felipe Martins Silveira Marília Afonso Rebelo Buzalaf Manoela Domingues Martins Maria Elena Crespo-Lopez Rafael Rodrigues Lima 《International journal of molecular sciences》2022,23(4)
Aluminum (Al) is one of the most abundant elements on Earth, and its high extraction rate and industrial use make human exposure very common. As Al may be a human toxicant, it is important to investigate the effects of Al exposure, mainly at low doses and for prolonged periods, by simulating human exposure. This work aimed to study the effects of low-dose exposure to chloride aluminum (AlCl3) on the oxidative biochemistry, proteomic profile, and morphology of the major salivary glands. Wistar male rats were exposed to 8.3 mg/kg/day of AlCl3 via intragastric gavage for 60 days. Then, the parotid and submandibular glands were subjected to biochemical assays, proteomic evaluation, and histological analysis. Al caused oxidative imbalance in both salivary glands. Dysregulation of protein expression, mainly of those related to cytoarchitecture, energy metabolism and glandular function, was detected in both salivary glands. Al also promoted histological alterations, such as acinar atrophy and an increase in parenchymal tissue. Prolonged exposure to Al, even at low doses, was able to modulate molecular alterations associated with morphological impairments in the salivary glands of rats. From this perspective, prolonged Al exposure may be a risk to exposed populations and their oral health. 相似文献
163.
The chemical interaction of 2,3-butanedione with amino acids through Strecker reaction has been studied extensively. However, the formation of previously reported 4,5-dimethyl-1,2-benzoquinone from 2,3-butanedione/amino acid model systems has not been investigated in detail. In this study such model systems containing 2,3-butanedione were investigated under pyrolytic conditions using glycine, sodium glycinate and glycine hydrochloride as amino acids able to modulate acid/base catalytic activity of the reaction medium. The analysis of the data indicated that replacing glycine with its corresponding salts promoted significantly the generation of 2,3,6,7-tetramethylquinoxaline relative to tetramethylpyrazine, the indicator compound for the Strecker reaction. The origin of the 2,3,6,7-tetramethylquinoxaline was traced back to the formation of 4,5-dimethyl-1,2-benzoquinone through isotope labelling studies. Furthermore, these studies have also indicated the ability of glycine not only to catalyse the cyclocondensation of butanedione into 4,5-dimethyl-1,2-benzoquinone but also its conversion into 4,5-dimethyl-1,2-phenylenediamine through Strecker-type transformations. The trapping of 2,3-butanedione by this in situ generated 4,5-dimethyl-1,2-phenylenediamine gave rise to the observed 2,3,6,7-tetramethylquinoxaline. 相似文献
164.
Olivia Guerra Santin 《Energy and Buildings》2011,43(10):2662-2672
The difference between the actual and predicted energy consumption for heating in housing is thought to be partly attributable to the use of HVAC systems. More reliable data on energy consumption could help in determining the actual energy performance of dwellings and in the search for the most adequate design for housing and home amenities. Further reductions on energy consumption might also be achieved if energy-saving policy programmes were geared to different household groups. The aim of this paper is to statistically determine Behavioural Patterns associated with the energy spent on heating and to identify household and building characteristics that could contribute to the development of energy-User Profiles. This study had two outcomes: it identified Behavioural Patterns to be used in energy calculations and it discerned User Profiles with different behaviours. Five underlying groups of behavioural variables were found, which were used to define the Behavioural Patterns and User Profiles. The groups showed statistically significant differences in the scores for most of the behavioural factors. This study established clear relationships between occupant behaviour and household characteristics. However, it seems difficult to establish relationships between energy consumption and Behavioural Patterns and household groups. 相似文献
165.
Janete Deliberali Freo Neiva Deliberali Rosso Lidiane Borges Dias de Moraes Álvaro Renato Guerra Dias Moacir Cardoso Elias Luiz Carlos Gutkoski 《Journal of Stored Products Research》2011,47(4):316-320
This study was done to evaluate the physicochemical properties and to quantify the residual silicon in flour from wheat grains treated with different dosages of DE and stored in a conventional system for 180 days. Samples containing 10.0 kg of wheat grain were treated with 0.00, 2.00 and 4.00 g kg−1 of DE and then homogenized and stored in cotton bags at 22 °C and 70 ± 5 g 100 g−1 relative humidity. Physicochemical analyses were carried out at 0, 60, 120 and 180 days of storage. The experiment was conducted in a randomized design with a factorial 3 × 4 arrangement (three doses of DE × four storage periods), totaling 12 treatments, with three replicates for each treatment. The wheat flour samples were digested and the silicon residue quantification was conducted through colorimetry. The wheat treated with DE presented a lower test weight compared with control, +b∗ chromaticity coordinate for color and increased ash content and L∗. The physicochemical changes in the grain and wheat flour were proportional to the amount of DE applied. 相似文献
166.
Excessive frictional loading to the skin often results in the formation of blisters, due to the transmission of shear loading
to the interfaces between dermal cell strata. The consequences of blistering range from mild discomfort to serious infection.
In some patients, such as those disposed to epidermolysis bullosa or neuropathic diabetes, blisters can severely degrade life
quality. Investigation of environmental and application parameters that affect blister formation has occurred primarily as
a qualitative, observational pursuit on human subjects, which has often led to confounding of data and lack of repeatability.
The authors have developed a Synthetic Skin Simulant Platform (3SP) that reproduces the mechanical behavior of human skin
when exposed to tribological loading. The platform is an assembled construct of bonded elastomeric layers that act as surrogates
for the epidermis, basement membrane, dermis, and subdermal structure. Epidermal (top layer) materials are typically silicone
or polyurethane films with a friction coefficient akin to human skin, while sublayers display mechanical properties similar
to their anatomical analogs. Blistering is evident optically by examining the separation voids formed after applying shear
loads to the epidermal layer. The 3SP has been used in a two-axis pin-on-flat tribometer with a stainless steel indenter to
study the normal load and friction coefficients encountered at the onset of frictional blistering. The 3SP allows for modulation
of friction coefficient, interfacial adhesion strength, and subdermal stiffness for investigation of blistering damage to
various anatomical sites. Experimental results have been compared to human test data and have shown that the 3SP provides
the potential to make significant advances with respect to skin tribology research. 相似文献
167.
Health care providers and purchasers of health services have an opportunity to improve patient care and potentially save costs through the wise purchase of interactive health communication applications for patients and employees. Purchasing decisions based on evaluation and evidence should drive the design and development of new systems. The cycle of evaluation includes a needs assessment before system development, usability testing during development, and studies of use and outcomes in natural settings. This type of evidence is critical to our understanding of how best to provide health information and decision assistance to patients, employees, and others. 相似文献
168.
A fault-tolerant architectural approach for dependable systems 总被引:2,自引:0,他引:2
A system's structure enables it to generate its intended behavior from its components' behavior. A well-structured system simplifies relationships among components, which can increase dependability. With software systems, the architecture is an abstraction of the structure. Architectural reasoning about dependability has become increasingly important because emerging applications are increasingly complex. We've developed an architectural approach for effectively representing and analyzing fault-tolerant software systems. The proposed solution relies on exception handling to tolerate faults associated with component and connector failures, architectural mismatches, and configuration faults. Our approach, a specialization of the peer-to-peer architectural style, hides inside the architectural elements the complexities of exception handling and propagation. Our goal is to improve a system's overall reliability and availability by making it tolerant of nonmalicious faults. 相似文献
169.
170.
ML Loh TW McLean JD Buckley W Howells DG Gilliland FO Smith 《Canadian Metallurgical Quarterly》1998,22(5):461-464
The percutaneous cardiopulmonary support system (PCPS) was used in a 64-year-old woman with cardiogenic shock due to sustained ventricular fibrillation (Vf) caused by severe aortic stenosis and regurgitation. The Vf attack was resistant to cardioversion and adrenaline for lack of left ventricular support by PCPS. She was transported to the operation theater with PCPS in situ and emergency aortic valve replacement was performed. Although preoperative cardiac resuscitation time was long (35 minutes), she was discharged from the hospital on foot without any neurological complications on 84th postoperative day. Because PCPS does not decrease left ventricular systolic stress in poorly contracting dilated heart, early surgical treatment is needed in patients with severely damaged heart. 相似文献