全文获取类型
收费全文 | 1732篇 |
免费 | 105篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 544篇 |
金属工艺 | 24篇 |
机械仪表 | 48篇 |
建筑科学 | 46篇 |
矿业工程 | 2篇 |
能源动力 | 42篇 |
轻工业 | 363篇 |
水利工程 | 10篇 |
石油天然气 | 19篇 |
无线电 | 81篇 |
一般工业技术 | 251篇 |
冶金工业 | 197篇 |
原子能技术 | 19篇 |
自动化技术 | 172篇 |
出版年
2024年 | 4篇 |
2023年 | 11篇 |
2022年 | 73篇 |
2021年 | 72篇 |
2020年 | 49篇 |
2019年 | 55篇 |
2018年 | 71篇 |
2017年 | 68篇 |
2016年 | 61篇 |
2015年 | 49篇 |
2014年 | 85篇 |
2013年 | 155篇 |
2012年 | 93篇 |
2011年 | 102篇 |
2010年 | 75篇 |
2009年 | 84篇 |
2008年 | 76篇 |
2007年 | 77篇 |
2006年 | 52篇 |
2005年 | 47篇 |
2004年 | 40篇 |
2003年 | 36篇 |
2002年 | 36篇 |
2001年 | 30篇 |
2000年 | 29篇 |
1999年 | 16篇 |
1998年 | 61篇 |
1997年 | 42篇 |
1996年 | 42篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 13篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1980年 | 7篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1974年 | 4篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 4篇 |
排序方式: 共有1841条查询结果,搜索用时 0 毫秒
101.
Arcamone N Lucini C Borzacchiello G Castaldo L Gargiulo G De Girolamo P 《Microscopy research and technique》2005,66(1):17-24
By means of immunochemistry and immunohistochemistry, we investigated in the kidney of freshwater and marine teleostean species for the presence and localization of three neurotrophins: nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin (NT)-3. In both species studied, NGF-like and NT-3-like immunoreactivity were present in the kidney with different distribution patterns, while BDNF-like immunoreactivity was never detected. In goldfish, NGF-like and NT-3-like immunoreactivity were identified extensively in cells along part of the arterial branches adjacent to the afferent arterioles. In scorpion fish, NGF-like and NT-3-like immunoreactive cells were observed both on afferent arterioles and on adjacent secondary branches derived from renal arteries. No immunoreactivity was detected in other renal structures. A staining pattern of immunoreactivity similar to that obtained for NGF and NT-3 was detected utilizing S100 antibody as a juxtaglomerular (JG) cell marker. Double immunolabellings NGF/S100 and NT-3/S100 evidenced the coexistence of neurotrophin-like proteins and S100-like protein in the same immunoreactive cells, thus identifying them as juxtaglomerular cells. Western blot analysis revealed the presence of molecules immunoreactive to NGF and NT-3, whose molecular weights were very similar to those of the corresponding mammalian neurotrophins. These findings extend the presence and distribution of NGF-like and NT-3-like IR in the kidney to teleost species, suggesting a probable participation of these proteins in the renal functions of freshwater and marine teleosts. 相似文献
102.
Photoelectrochemical degradation of lignin 总被引:4,自引:0,他引:4
R. Pelegrini J. Reyes N. Durán P.P. Zamora A.R. de Andrade 《Journal of Applied Electrochemistry》2000,30(8):953-958
We have evaluated the efficient of degradation of lignin by an photoelectrochemical process. Using a Ti/Ru0.1Sn0.6Ti0.3O2 electrode, a quartz reaction device and an artificial ultraviolet light, decoloration ratios higher than 70%, and reductions of 51% and 83% in TOC and total phenol products, respectively, were observed for a reaction time of 6 h. Comparing these values with the sum of the decoloration ratios (or TOC and total phenol reductions) obtained by separate measuring of electrochemical and photochemical procedures, a significant synergetic effect between these two processes was observed. Furthermore, the degradation capacity of the photoelectrochemical process increases as the SnO2 content is increased. 相似文献
103.
Iwona Kuźniarska-Biernacka Ana R. Silva Ana P. Carvalho João Pires Cristina Freire 《Catalysis Letters》2010,134(1-2):63-71
The chiral Mn(III) salen complex (C1) was immobilised onto a natural clay (BEN) and a porous clay heterostructure (PCH) functionalised with 3-aminopropyltriethoxysilane (APTES). FTIR, XPS and Mn chemical analysis confirm the C1 anchorage in both materials, but with higher efficiency in BEN_APTES clay. The catalytic activity of C1@BEN_APTES and C1@PCH_APTES, was assessed in the epoxidation of styrene (sty) and ∝-methylstyrene (∝-Mesty) using NaOCl and m-chloroperoxybenzoic acid (m-CPBA)/N-methylmorpholine-N-oxide (NMO). Both materials behave as moderate catalysts, show high epoxide selectivity but low enantiomeric excesses. In the case of sty epoxidation with m-CBPA/NMO the C1@PCH_APTES catalyst showed the highest catalytic activity, whereas in ∝-Mesty epoxidation, the C1@PCH_APTES catalyst, although leading to lower substrate conversion than the BEN analogue, presented the lowest complex leaching. In all cases, the oxidant NaOCl had some destructive effect in the hybrid catalysts, highlighting the importance of a careful choice of catalyst and oxidant system. 相似文献
104.
105.
Gabriela de Paula Arrifano Marcus Augusto-Oliveira Megan Sealey-Bright Jaezah Zainal Luciana Imbiriba Luanna Melo Pereira Fernandes Cristiane Socorro Ferraz Maia Daniel Anthony Maria Elena Crespo-Lopez 《International journal of molecular sciences》2021,22(19)
Human exposure to methylmercury (MeHg) is currently high in regions such as the Amazon. Understanding the molecular changes associated with MeHg-induced neurotoxicity and the crosstalk with the periphery is essential to support early diagnoses. This work aimed to evaluate cellular and molecular changes associated with behavioral alterations in MeHg acute exposure and the possible changes in extracellular vesicles (EVs) number and S100β content. Adults male Wistar rats were orally treated with 5 mg/kg for four days. Behavioral performance, molecular and histological changes in the cerebellum, and plasma EVs were assessed. MeHg-intoxicated animals performed significantly worse in behavioral tests. MeHg increased the number of GFAP+ cells and GFAP and S100β mRNA expression in the cerebellum but no change in NeuN+ or IBA-1+ cells number was detected. The number of exosomes isolated from plasma were decreased by the metal. S100B mRNA was detected in circulating plasma EVs cargo in MeHg exposure. Though preliminary, our results suggest astrocytic reactivity is displaying a protective role once there was no neuronal death. Interestingly, the reduction in exosomes number could be a new mechanism associated with MeHg-induced neurotoxicity and plasma EVs could represent a source of future biomarkers in MeHg intoxication. 相似文献
106.
Alejandra P. Magnoli Luciana Tallone Carlos A.R. Rosa Ana M. Dalcero Stella M. Chiacchiera Rosa M. Torres Sanchez 《Applied Clay Science》2008,40(1-4):63-71
Some bentonites have been probed to be efficient as sequestering agents for aflatoxins; they decreased the bioavailability of the toxin in the gastrointestinal tracts of birds when they are incorporated in the diets. The binding capacity of these adsorbents varied with the rheological source and even among batches of a given source. Three bentonites from different sources in Argentina, which have very different aflatoxins (AFs) adsorption capacity, were studied. The characterization comprises chemical analysis, scanning electron microscopy (SEM), X-ray power diffraction (XRD), Hg intrusion porosimetry, swelling capacity, etc. The main factors affecting the adsorption of AFs seem to be related to the isomorphic substitution of the montmorillonite and to electrostatic interactions generated by the surface charge of the samples. Neither the mean pore size nor the percentage of quartz has any effect upon the AFs adsorption. 相似文献
107.
Adriano Pinto Mariano Caliane Bastos Borba Costa Dejanira de Franceschi de Angelis Francisco Maugeri Filho Daniel Ibraim Pires Atala Maria Regina Wolf Maciel Rubens Maciel Filho 《Chemical Engineering Research and Design》2010,88(5-6):562-571
Factorial design and response surface techniques were used in combination with mathematical modelling and computational simulation to optimise an innovative industrial bioprocess, the production of biobutanol employing the flash fermentation technology. A parametric analysis performed by means of a full factorial design at two levels determined the influence of operating variables on butanol yield and productivity. A second set of simulations were carried out based on the central composite rotatable design. This procedure generated simplified statistical models that describe butanol yield and productivity as functions of the significant operating variables. From these models, response surfaces were obtained and used to optimise the process. For a range of substrate concentration from 130 to 180 g/l, the optimum operating ranges ensure butanol productivity between 7.0 and 8.0 g/l h, butanol yield between 19 and 22%, substrate conversion above 90% and final butanol concentration around 25 g/l. 相似文献
108.
Fernanda Rodríguez-Enríquez Dr. Dolores Viña Dr. Eugenio Uriarte Dr. Reyes Laguna Dr. Maria J. Matos 《ChemMedChem》2021,16(1):179-186
This study explores the potential of 7-amidocoumarins as multitarget agents against Parkinson's and Alzheimer's diseases, by modulating the substitution patterns within the scaffold. Sixteen compounds were synthesized via 7-amino-4-methylcoumarin acylation, and in vitro evaluation of the molecules against hMAO-A, hMAO-B, hAChE, hBuChE and hBACE1 was performed. Five compounds turned out to be potent and selective hMAO-B inhibitors in the nanomolar range, six displayed inhibitory activity of hMAO-A in the low micromolar range, one showed hAChE inhibitory activity and another one hBACE1 inhibitory activity. MAO-B reversibility profile of 7-(4’-chlorobenzamido)-4-methylcoumarin ( 10 ) was investigated, with this compound being a reversible inhibitor. Neurotoxicity on motor cortex neurons and neuroprotection against H2O2 were also studied, corroborating the safety profile of these molecules. Finally, theoretical ADME properties were also calculated, showing these molecules as good candidates for the optimization of a lead compound. Results suggest that by modulating the substitution pattern at position 7 of the scaffold, selective or multitarget molecules can be achieved. 相似文献
109.
Luciana M. Rodriguez María B. Fernández Ethel E. Pérez Guillermo H. Crapiste 《European Journal of Lipid Science and Technology》2021,123(1):2000132
The main goal of this work is to evaluate the extraction of sunflower oil from enzyme-treated collets using ethanol and isopropanol (IPA) as solvents. The sunflower collets are pretreated with the multienzyme complex Viscozyme L prior to solvent extraction by the Soxhlet method. The influence of the moisture content of the collets, pretreatment, processing time, and solvent type on the amount of total extracted material and the oil extraction efficiency is studied. Some quality parameters such as phospholipid content of the oil and chlorogenic acid content of the residual meal are also analyzed. At low moisture content (7%) the solvents exhibit similar oil extraction ability (98–99%), but with increasing moisture the extraction efficiency of ethanol decreases to about 85%, while no significant differences are observed for IPA. The enzymatic treatment increases the extraction efficiency for all times, especially for ethanol. It is observed that IPA is more efficient in the extraction compared to ethanol, and the amount of nonlipid material is reduced by ≈70%. In addition, the oil extracted with IPA have lower phospholipid content and the residual meal presents a higher chlorogenic acid content. Practical Applications:This work would contribute toward the use of green solvents in the extraction of sunflower oil from collets. Ethanol and isopropanol, used as solvents, present attractive advantages, including low toxicity, good operational security, as well as being obtained from a renewable source. The obtained data provide up-to-date information on the use of these alcohols in the extraction of sunflower oil from collets and the influence of operating conditions, such as moisture content, enzymatic pretreatment of the collets, and the extraction time. Information about oil and meal quality is also reported. 相似文献
110.
Qianyu Yang Chen Gao Xuemei Zhang Chihui Tsou Xingyu Zhao Manuel Reyes De Guzman Zejun Pu Xinyue Li Yue Lu Chunyan Zeng Li Yuan Yiqing Xia Yuping Sheng Yiqing Fu 《大分子材料与工程》2021,306(7):2100093
Hydrogels with excellent stiffness, toughness, anti-fatigue, and self-recovery properties are regarded as promising water-containing materials. In this work, a dual physically cross-linked (DPC) sodium alginate (SA)/poly[acrylamide (AAm)-acrylic acid (AAc)-octadecyl methacrylate (OMA)]-Fe3+ hydrogel is reported, which is constructed by hydrophobic association (HA) and ionic coordination (IC). The optimal DPC hydrogel demonstrates excellent mechanical performance: tensile modulus of 0.65 MPa, tensile strength of 3.31 MPa, elongation at break of 1547%, and toughness of 27.8 MJ m–3. SA/P(AAm-AAc-OMA)-Fe3+ DPC hydrogels also exhibit prominent anti-fatigue and self-recovery performance (99.1–109.7% modulus recovery and 90.4–108.9% dissipated energy recovery after resting for 5 min without additional stimuli at ambient temperature) through the reconstruction of reversible physical cross-linking. Some of the SA/P(AAm-AAc-OMA)-Fe3+ DPC hydrogels even exhibit a stretching-induced strengthening effect, which is similar to the performance of muscle—“the more training, the more strength.” Hence, the combination of HA and IC will provide an effective approach to design DPC hydrogels with desirable mechanical performances and a longer service life for wider applications of soft materials. 相似文献