全文获取类型
收费全文 | 2365篇 |
免费 | 115篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 30篇 |
综合类 | 3篇 |
化学工业 | 626篇 |
金属工艺 | 32篇 |
机械仪表 | 77篇 |
建筑科学 | 74篇 |
矿业工程 | 4篇 |
能源动力 | 115篇 |
轻工业 | 266篇 |
水利工程 | 17篇 |
石油天然气 | 9篇 |
无线电 | 191篇 |
一般工业技术 | 396篇 |
冶金工业 | 86篇 |
原子能技术 | 15篇 |
自动化技术 | 546篇 |
出版年
2024年 | 6篇 |
2023年 | 36篇 |
2022年 | 93篇 |
2021年 | 83篇 |
2020年 | 88篇 |
2019年 | 82篇 |
2018年 | 104篇 |
2017年 | 90篇 |
2016年 | 97篇 |
2015年 | 77篇 |
2014年 | 122篇 |
2013年 | 181篇 |
2012年 | 184篇 |
2011年 | 184篇 |
2010年 | 143篇 |
2009年 | 113篇 |
2008年 | 112篇 |
2007年 | 96篇 |
2006年 | 85篇 |
2005年 | 49篇 |
2004年 | 67篇 |
2003年 | 56篇 |
2002年 | 44篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 15篇 |
1998年 | 22篇 |
1997年 | 30篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 3篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有2487条查询结果,搜索用时 15 毫秒
91.
Phenyl‐γ‐valerolactones,flavan‐3‐ol colonic metabolites,protect brown adipocytes from oxidative stress without affecting their differentiation or function 下载免费PDF全文
92.
Li-Xia Pang Sen Ren Xiao-Long Wang Di Zhou Wei-Guo Liu Charanjeet Singh Antonio Sergio Bezerra Sombra Moustafa Adel Darwish 《Advanced Engineering Materials》2023,25(16):2300321
The compounds xBi(Mg2/3Nb1/3)O3-(1 − x)(Ba0.8Sr0.2)TiO3 (xBMN-(1 − x)BST, 0.08 ≤ x ≤ 0.14) are prepared via the traditional solid-state reaction method and the ceramics are well densified in the sintering temperature range of 1280–1330 °C. X-ray diffraction analysis shows that all the ceramics crystallize into perovskite structure. Proper amounts of BMN additions can effectively reduce grain sizes of the xBMN-(1 − x)BST ceramics, resulting in more uniform microstructures. Accordingly, breakdown strength Eb is improved and a maximum value 250 kV cm−1 is obtained in ceramic with x = 0.10. Meanwhile, recoverable energy storage density Wrec of the 0.1BMN-0.9BST ceramics reaches 2.03 J cm−3, and energy storage efficiency (η) is 96.8%. When the operating temperature increases to 150 °C, the Wrec and η values are about 1.02 J cm−3 under 150 kV cm−1 and 89.8%, respectively. 相似文献
93.
Dissolved trace metal (Ag, Cd, Cu, Fe, Ni, Pb, and Zn), inorganic nutrient (NO3, NH4, PO4, H4SiO4), and DOC concentrations were measured at 43 stations during low (July 2000) and high (April 2001) river discharge conditions in surface waters of Long Island Sound (LIS). To evaluate the impact of fluvial sources to the total metal budget of the sound, samples were collected from major tributaries discharging into LIS (Thames, Quinnipiac, Housatonic, Connecticut, and East Rivers). To compare LIS with other coastal embayments, samples were also collected from five LIS coastal embayments (Manhassett Bay, Huntington Harbor, Oyster Bay, Hempstead Harbor, and Port Jefferson Harbor), which are monitored by the U.S. National Status and Trends Program. Metal and nutrient distributions identified two biogeochemical regimes within LIS: an area of relatively high nutrient and metal concentrations in the East River/Narrows region in western LIS and an area in the eastern region of the sound that had comparatively lower concentrations. Mass balance estimates indicated that, during low flow conditions, the East River was the dominant allochthonous source of most trace metals (Ag, Cd, Cu, Ni, Zn) and inorganic nutrients (NO3 and PO4); during high flow conditions, the most influential source of these constituents was the Connecticut River. Mass balance estimates also evidenced a large autochthonous source of Cu, Ni, and Zn, as their spatial distributions displayed elevated concentrations away from point sources such as the East River. Principal component analysis suggested that metal and nutrient distributions in the LIS system were influenced by different seasonal processes: remobilization from contaminated sediments, anthropogenic inputs from sewage discharges and phytoplankton scavenging during the spring freshet, and benthic remobilization during summer conditions. 相似文献
94.
Propagation in fretting fatigue from a surface defect 总被引:3,自引:0,他引:3
This paper analyses the growth of cracks in fretting fatigue from an initial flaw at the surface. Different crack growth laws are used in order to take into consideration the particular behaviour of short cracks. This methodology is applied to estimate life in various fretting fatigue tests with spherical contact characterized by two different geometries. The material used in the experiments is Al7075. The two geometries present significant differences in the evolution of the stresses, crack growth, etc. which are discussed. The approaches used to model short crack growth give different results, some of them being in good agreement with the experiments. 相似文献
95.
96.
Activity of Fluorine‐Containing Analogues of WC‐9 and Structurally Related Analogues against Two Intracellular Parasites: Trypanosoma cruzi and Toxoplasma gondii 下载免费PDF全文
María N. Chao Catherine Li Melissa Storey Dr. Bruno N. Falcone Dr. Sergio H. Szajnman Prof. Dr. Sergio M. Bonesi Prof. Dr. Roberto Docampo Prof. Dr. Silvia N. J. Moreno Prof. Dr. Juan B. Rodriguez 《ChemMedChem》2016,11(24):2690-2702
Two obligate intracellular parasites, Trypanosoma cruzi, the agent of Chagas disease, and Toxoplasma gondii, an agent of toxoplasmosis, upregulate the mevalonate pathway of their host cells upon infection, which suggests that this host pathway could be a potential drug target. In this work, a number of compounds structurally related to WC‐9 (4‐phenoxyphenoxyethyl thiocyanate), a known squalene synthase inhibitor, were designed, synthesized, and evaluated for their effect on T. cruzi and T. gondii growth in tissue culture cells. Two fluorine‐containing derivatives, the 3‐(3‐fluorophenoxy)‐ and 3‐(4‐fluorophenoxy)phenoxyethyl thiocyanates, exhibited half‐maximal effective concentration (EC50) values of 1.6 and 4.9 μm , respectively, against tachyzoites of T. gondii, whereas they showed similar potency to WC‐9 against intracellular T. cruzi (EC50 values of 5.4 and 5.7 μm , respectively). In addition, 2‐[3‐ (phenoxy)phenoxyethylthio]ethyl‐1,1‐bisphosphonate, which is a hybrid inhibitor containing 3‐phenoxyphenoxy and bisphosphonate groups, has activity against T. gondii proliferation at sub‐micromolar levels (EC50=0.7 μm ), which suggests a combined inhibitory effect of the two functional groups. 相似文献
97.
Massimo Venditti Davide Arcaniolo Marco De Sio Sergio Minucci 《International journal of molecular sciences》2021,22(15)
Herein, for the first time, the potential relationships between the cytoskeleton-associated proteins DAAM1 and PREP with different testicular disorders, such as classic seminoma (CS), Leydig cell tumor (LCT), and Sertoli cell-only syndrome (SOS), were evaluated. Six CS, two LCT, and two SOS tissue samples were obtained during inguinal exploration in patients with a suspect testis tumor based on clinical examination and ultrasonography. DAAM1 and PREP protein levels and immunofluorescent localization were analyzed. An increased DAAM1 protein level in CS and SOS as compared to non-pathological (NP) tissue was observed, while LCT showed no significant differences. Conversely, PREP protein level increased in LCT, while it decreased in CS and SOS compared to NP tissue. These results were strongly supported by the immunofluorescence staining, revealing an altered localization and signal intensity of DAAM1 and PREP in the analyzed samples, highlighting a perturbed cytoarchitecture. Interestingly, in LCT spermatogonia, a specific DAAM1 nuclear localization was found, probably due to an enhanced testosterone production, as confirmed by the increased protein levels of steroidogenic enzymes. Finally, although further studies are needed to verify the involvement of other formins and microtubule-associated proteins, this report raised the opportunity to indicate DAAM1 and PREP as new potential markers, supporting the cytoskeleton dynamics changes occurring during normal and/or pathological cell differentiation. 相似文献
98.
Samuel Brando Susin Vinicius Pistor Sandro Campos Amico Luiz Antonio Ferreira Coelho Sergio Henrique Pezzin Ademir José Zattera 《应用聚合物科学杂志》2014,131(3)
With the increased interest in thermoset resin nanocomposites, it is important to understand the effects of the material on nanoscale characteristics. In this study, a curing reaction of an epoxy resin, which contained 0.25, 0.50, or 1.00 wt % of multiwalled carbon nanotubes (MWCNTs), at different heating rates was monitored by differential scanning calorimetry; cure kinetics were also evaluated to establish a relationship between crosslinking (network formation) and mechanical properties. MWCNT concentrations above 0.25 wt % favored crosslinking formation and decreased the activation energy (Ea) in the curing reaction. Examination of the kinetic mechanism suggests that the MWCNT locally restricted the spatial volume and favored the formation of nodular morphology in the resin, especially for high MWCNT concentrations. The MWCNT exhibited some entanglement in the matrix, which hindered a more pronounced effect on the mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39857. 相似文献
99.
Ruben Ramírez‐Gómez Daniel García‐Cortés Gaston Martínez‐de Jesús Margarita M. González‐Brambila Alejandro Alonso Sergio A. Martínez‐Delgadillo Jorge Ramírez‐Muñoz 《化学工程与技术》2015,38(9):1519-1529
High‐shear impellers (HSIs) are mixers used in industrial stirred tanks to incorporate powders into liquids and break down particle agglomerates. A detailed numerical study of two commercial ring‐style HSIs of laboratory scale was carried out and their performance was compared with the Rushton turbine (RT). It was found that power and pumping numbers or their ratio cannot be simply connected for properly selecting an impeller in applications where highly localized viscous dissipation is desirable. The ratio of the average viscous dissipation in the impeller swept volume to the mean in the entire volume at two constant values of power input turned out to be lower for HSIs compared to that evaluated for RT. However, at higher power input, the dimensionless average viscous dissipation in the blade swept volume was found to be similar for the HSI of two rings and the RT, corroborating the high local viscous dissipation of this HSI when operated at higher speeds. 相似文献
100.
Structural Determinants of the Selectivity of 3‐Benzyluracil‐1‐acetic Acids toward Human Enzymes Aldose Reductase and AKR1B10 下载免费PDF全文
Dr. Francesc X. Ruiz Alexandra Cousido‐Siah Dr. Sergio Porté Dr. Marta Domínguez Isidro Crespo Chris Rechlin Dr. André Mitschler Prof. Dr. Ángel R. de Lera Dr. María Jesús Martín Dr. Jesús Ángel de la Fuente Prof. Dr. Gerhard Klebe Prof. Dr. Xavier Parés Prof. Dr. Jaume Farrés Dr. Alberto Podjarny 《ChemMedChem》2015,10(12):1989-2003
The human enzymes aldose reductase (AR) and AKR1B10 have been thoroughly explored in terms of their roles in diabetes, inflammatory disorders, and cancer. In this study we identified two new lead compounds, 2‐(3‐(4‐chloro‐3‐nitrobenzyl)‐2,4‐dioxo‐3,4‐dihydropyrimidin‐1(2H)‐yl)acetic acid (JF0048, 3 ) and 2‐(2,4‐dioxo‐3‐(2,3,4,5‐tetrabromo‐6‐methoxybenzyl)‐3,4‐dihydropyrimidin‐1(2H)‐yl)acetic acid (JF0049, 4 ), which selectively target these enzymes. Although 3 and 4 share the 3‐benzyluracil‐1‐acetic acid scaffold, they have different substituents in their aryl moieties. Inhibition studies along with thermodynamic and structural characterizations of both enzymes revealed that the chloronitrobenzyl moiety of compound 3 can open the AR specificity pocket but not that of the AKR1B10 cognate. In contrast, the larger atoms at the ortho and/or meta positions of compound 4 prevent the AR specificity pocket from opening due to steric hindrance and provide a tighter fit to the AKR1B10 inhibitor binding pocket, probably enhanced by the displacement of a disordered water molecule trapped in a hydrophobic subpocket, creating an enthalpic signature. Furthermore, this selectivity also occurs in the cell, which enables the development of a more efficient drug design strategy: compound 3 prevents sorbitol accumulation in human retinal ARPE‐19 cells, whereas 4 stops proliferation in human lung cancer NCI‐H460 cells. 相似文献