全文获取类型
收费全文 | 13918篇 |
免费 | 2684篇 |
国内免费 | 1321篇 |
专业分类
电工技术 | 664篇 |
技术理论 | 1篇 |
综合类 | 965篇 |
化学工业 | 1944篇 |
金属工艺 | 364篇 |
机械仪表 | 1732篇 |
建筑科学 | 382篇 |
矿业工程 | 149篇 |
能源动力 | 363篇 |
轻工业 | 568篇 |
水利工程 | 150篇 |
石油天然气 | 781篇 |
武器工业 | 219篇 |
无线电 | 3683篇 |
一般工业技术 | 2438篇 |
冶金工业 | 222篇 |
原子能技术 | 574篇 |
自动化技术 | 2724篇 |
出版年
2024年 | 39篇 |
2023年 | 362篇 |
2022年 | 462篇 |
2021年 | 681篇 |
2020年 | 697篇 |
2019年 | 647篇 |
2018年 | 660篇 |
2017年 | 736篇 |
2016年 | 784篇 |
2015年 | 848篇 |
2014年 | 980篇 |
2013年 | 952篇 |
2012年 | 1116篇 |
2011年 | 1082篇 |
2010年 | 816篇 |
2009年 | 770篇 |
2008年 | 751篇 |
2007年 | 855篇 |
2006年 | 664篇 |
2005年 | 553篇 |
2004年 | 537篇 |
2003年 | 400篇 |
2002年 | 377篇 |
2001年 | 291篇 |
2000年 | 274篇 |
1999年 | 245篇 |
1998年 | 190篇 |
1997年 | 174篇 |
1996年 | 175篇 |
1995年 | 113篇 |
1994年 | 125篇 |
1993年 | 95篇 |
1992年 | 73篇 |
1991年 | 62篇 |
1990年 | 49篇 |
1989年 | 50篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 23篇 |
1984年 | 25篇 |
1983年 | 26篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1976年 | 4篇 |
1959年 | 8篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Ioannis-Dimosthenis S. Adamakis Ilektra Sperdouli Anetta Han Anelia Dobrikova Emilia Apostolova Michael Moustakas 《International journal of molecular sciences》2021,22(1)
Five-day exposure of clary sage (Salvia sclarea L.) to 100 μM cadmium (Cd) in hydroponics was sufficient to increase Cd concentrations significantly in roots and aboveground parts and affect negatively whole plant levels of calcium (Ca) and magnesium (Mg), since Cd competes for Ca channels, while reduced Mg concentrations are associated with increased Cd tolerance. Total zinc (Zn), copper (Cu), and iron (Fe) uptake increased but their translocation to the aboveground parts decreased. Despite the substantial levels of Cd in leaves, without any observed defects on chloroplast ultrastructure, an enhanced photosystem II (PSII) efficiency was observed, with a higher fraction of absorbed light energy to be directed to photochemistry (ΦPSΙΙ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in an important decrease in the dissipated non-regulated energy (ΦNO), modifying the homeostasis of reactive oxygen species (ROS), through a decreased singlet oxygen (1O2) formation. A basal ROS level was detected in control plant leaves for optimal growth, while a low increased level of ROS under 5 days Cd exposure seemed to be beneficial for triggering defense responses, and a high level of ROS out of the boundaries (8 days Cd exposure), was harmful to plants. Thus, when clary sage was exposed to Cd for a short period, tolerance mechanisms were triggered. However, exposure to a combination of Cd and high light or to Cd alone (8 days) resulted in an inhibition of PSII functionality, indicating Cd toxicity. Thus, the rapid activation of PSII functionality at short time exposure and the inhibition at longer duration suggests a hormetic response and describes these effects in terms of “adaptive response” and “toxicity”, respectively. 相似文献
32.
Maryam Oroujeni Sara S. Rinne Anzhelika Vorobyeva Annika Loftenius Joachim Feldwisch Per Jonasson Vladimir Chernov Anna Orlova Fredrik Y. Frejd Vladimir Tolmachev 《International journal of molecular sciences》2021,22(5)
Radionuclide imaging of HER2 expression in tumours may enable stratification of patients with breast, ovarian, and gastroesophageal cancers for HER2-targeting therapies. A first-generation HER2-binding affibody molecule [99mTc]Tc-ZHER2:V2 demonstrated favorable imaging properties in preclinical studies. Thereafter, the affibody scaffold has been extensively modified, which increased its melting point, improved storage stability, and increased hydrophilicity of the surface. In this study, a second-generation affibody molecule (designated ZHER2:41071) with a new improved scaffold has been prepared and characterized. HER2-binding, biodistribution, and tumour-targeting properties of [99mTc]Tc-labelled ZHER2:41071 were investigated. These properties were compared with properties of the first-generation affibody molecules, [99mTc]Tc-ZHER2:V2 and [99mTc]Tc-ZHER2:2395. [99mTc]Tc-ZHER2:41071 bound specifically to HER2 expressing cells with an affinity of 58 ± 2 pM. The renal uptake for [99mTc]Tc-ZHER2:41071 and [99mTc]Tc-ZHER2:V2 was 25–30 fold lower when compared with [99mTc]Tc-ZHER2:2395. The uptake in tumour and kidney for [99mTc]Tc-ZHER2:41071 and [99mTc]Tc-ZHER2:V2 in SKOV-3 xenografts was similar. In conclusion, an extensive re-engineering of the scaffold did not compromise imaging properties of the affibody molecule labelled with 99mTc using a GGGC chelator. The new probe, [99mTc]Tc-ZHER2:41071 provided the best tumour-to-blood ratio compared to HER2-imaging probes for single photon emission computed tomography (SPECT) described in the literature so far. [99mTc]Tc-ZHER2:41071 is a promising candidate for further clinical translation studies. 相似文献
33.
Margarida S. C. A. Brito Joana Matos Marina V. L. Torres Claudio P. Fonte Madalena M. Dias José Carlos B. Lopes Ricardo J. Santos 《American Institute of Chemical Engineers》2022,68(4):e17597
Product formulations for industrial processes are typically developed at laboratory scale. However, the mixing conditions are not easily mimicked in the laboratory. A rotational device is proposed in this study as a fast laboratory-scale formulation development, which enables mimicking the mixing conditions in the industrial process. The geometrical configurations of the rotational device are from rheometry devices (plate-plate and cone-plate). The main advantages of this method are the small amounts of raw materials and shorter testing times. This methodology is applied to an industrial case study, the reaction injection molding (RIM) process. The mixing length scales evolution in the rotational rheometer were matched to those in RIM machines. The main novelty of this study is the introduction of a protocol that bridges the processing conditions at laboratory using small amounts of raw materials to high throughput continuous flow reactors. 相似文献
34.
Chemical engineering systems often involve a functional porous medium, such as in catalyzed reactive flows, fluid purifiers, and chromatographic separations. Ideally, the flow rates throughout the porous medium are uniform, and all portions of the medium contribute efficiently to its function. The permeability is a property of a porous medium that depends on pore geometry and relates flow rate to pressure drop. Additive manufacturing techniques raise the possibilities that permeability can be arbitrarily specified in three dimensions, and that a broader range of permeabilities can be achieved than by traditional manufacturing methods. Using numerical optimization methods, we show that designs with spatially varying permeability can achieve greater flow uniformity than designs with uniform permeability. We consider geometries involving hemispherical regions that distribute flow, as in many glass chromatography columns. By several measures, significant improvements in flow uniformity can be obtained by modifying permeability only near the inlet and outlet. 相似文献
35.
36.
A hybrid multiphase model is developed to simulate the simultaneous momentum, heat and mass transfer and heterogeneous catalyzed reaction in structured catalytic porous materials. The approach relies on the combination of the volume of fluid (VOF) and Eulerian–Eulerian models, and several plug-in field functions. The VOF method is used to capture the gas–liquid interface motion, and the Eulerian–Eulerian framework solves the temperature and chemical species concentration equations for each phase. The self-defined field functions utilize a single-domain approach to overcome convergence difficulty when applying the hybrid multiphase for a multi-domain problem. The method is then applied to investigate selective removal of specific species in multicomponent reactive evaporation process. The results show that the coupling of catalytic reaction and interface species mass transfer at the phase interface is conditional, and the coupling of catalytic reaction and momentum transfer across fluid–porous interface significantly affects the conversion rate of reactants. Based on the numerical results, a strategy is proposed for matching solid catalyst with operating condition in catalytic distillation application. 相似文献
37.
The thermosiphon is a passive heat exchange method, which circulates a fluid within a system without the need for any electrical or mechanical pumps. The thermosiphon is based on natural convection where the thermal expansion occurs when the temperature difference has a corresponding difference in density across the loop. Thermosiphons are used in different applications such as solar energy collection, automotive systems, and electronics. The current study aims to investigate thermosiphon thermal performance used in domestic applications. The thermal performance of a thermosiphon has been studied by many researchers; however, according to the knowledge of the authors, the influence of the amount of the working fluid on the thermal output has not yet been investigated. Therefore, the influence of the amount of working fluid within the riser pipe has been investigated on the thermal performance of the thermosiphon. In the current study, a computational fluid dynamics model is involved. This model has been validated by comparison with experimental findings. The maximum variation between numerical and experimental results is 14.2% and 11.2% for the working fluid at the inlet and outlet of the absorber pipe, respectively. Furthermore, the results show that the amount of working fluid inside the closed thermosiphon has a great influence on the thermal performance of the system. Additionally, it is found that Case-B, when the amount of working fluid is less than by 10% compared to the traditional model, is the best case among all cases under study. Furthermore, a correlation equation to predict water temperature at the exit of the absorber pipe has been established with an accuracy of 95.05%. 相似文献
38.
Naiyun Fan Guishan Liu Guoling Wan Jingjing Ban Ruirui Yuan Yourui Sun Yue Li 《International Journal of Food Science & Technology》2021,56(6):3066-3075
The study investigated the feasibility of using a combination of near-infrared hyperspectral imaging (NIR-HSI) with two-dimensional correlation (2DCOS) analysis for rapid and non-destructive determination of the content of biogenic amines in mutton during refrigerated storage. Total contents of biogenic amines (TBA) were used as the perturbation. By analysing the synchronous and asynchronous two-dimensional correlation spectra, sensitive variables that were closely related to TBA contents were obtained. The results showed that the wavelengths in the spectra range of 1002–1335 nm were the research area for the detection of TBA contents in mutton. The least-squares support vector machines (LSSVM) model based on effective wavelengths selected by competitive adaptive reweighted sampling (CARS) from 2DCOS analysis showed excellent results, with correlation coefficient in prediction (Rp) of 0.91, root mean square error in prediction (RMSEP) of 1.67 mg kg−1 and the ratio of performance deviation (RPD) of 2.76. The research demonstrated that the combination of NIR-HSI and 2DCOS could be used as an effective method for monitoring the content of biogenic amines in mutton. 相似文献
39.
40.
Modelling flow phenomena and their related weathering effects is often cumbersome due their dependence on the environment, materials and geometric properties of objects in the scene. Example‐based modelling provides many advantages for reproducing real textures, but little effort has been devoted to reproducing and transferring complex phenomena. In order to produce realistic flow effects, it is possible to take advantage of the widespread availability of flow images on the Internet, which can be used to gather key information about the flow. In this paper, we present a technique that allows the transfer of flow phenomena between photographs, adapting the flow to the target image and giving the user flexibility and control through specifically tailored parameters. This is done through two types of control curves: a fitted theoretical curve to control the mass of deposited material, and an extended colour map for properly adapting to the target appearance. In addition, our method filters and warps the input flow in order to account for the geometric details of the target surface. This leads to a fast and intuitive approach to easily transfer phenomena between images, providing a set of simple and intuitive parameters to control the process. 相似文献