全文获取类型
收费全文 | 1536篇 |
免费 | 89篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 376篇 |
金属工艺 | 7篇 |
机械仪表 | 4篇 |
建筑科学 | 55篇 |
矿业工程 | 2篇 |
能源动力 | 28篇 |
轻工业 | 236篇 |
水利工程 | 15篇 |
石油天然气 | 4篇 |
无线电 | 85篇 |
一般工业技术 | 286篇 |
冶金工业 | 343篇 |
原子能技术 | 3篇 |
自动化技术 | 164篇 |
出版年
2024年 | 4篇 |
2023年 | 26篇 |
2022年 | 71篇 |
2021年 | 105篇 |
2020年 | 41篇 |
2019年 | 43篇 |
2018年 | 56篇 |
2017年 | 55篇 |
2016年 | 45篇 |
2015年 | 42篇 |
2014年 | 72篇 |
2013年 | 80篇 |
2012年 | 102篇 |
2011年 | 175篇 |
2010年 | 92篇 |
2009年 | 94篇 |
2008年 | 100篇 |
2007年 | 99篇 |
2006年 | 57篇 |
2005年 | 45篇 |
2004年 | 31篇 |
2003年 | 26篇 |
2002年 | 20篇 |
2001年 | 18篇 |
2000年 | 10篇 |
1999年 | 17篇 |
1998年 | 9篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1957年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有1628条查询结果,搜索用时 15 毫秒
991.
Cornelia Peterson Robert Moore Jessica L. Hicks Laura A. Morsberger Angelo M. De Marzo Ying Zou Charles G. Eberhart Ashley A. Campbell 《International journal of molecular sciences》2021,22(16)
Ocular adnexal (OA) sebaceous carcinomas generally demonstrate more aggressive clinical and histopathological phenotypes than extraocular cases, but the molecular drivers implicated in their oncogenesis remain poorly defined. A retrospective review of surgical and ocular pathology archives identified eleven primary resection specimens of OA sebaceous carcinomas with adequate tissue for molecular analysis; two extraocular cases were also examined. Next-generation sequencing was used to evaluate mutations and copy number changes in a large panel of cancer-associated genes. Fluorescence in situ hybridization (FISH) confirmed MYC copy number gain in select cases, and immunohistochemistry to evaluate MYC protein expression. The commonest mutations occurred in TP53 (10/13) and RB1 (7/13). Additional mutations in clinically actionable genes, or mutations with a frequency of at least 25%, included the NF1 (3/12), PMS2 (4/12), ROS1 (3/12), KMT2C (4/12), MNX1 (6/12), NOTCH1 (4/12), PCLO (3/12), and PTPRT (3/12) loci. Low level copy number gain suggestive of amplification of the MYC locus was seen in two cases, and confirmed using FISH. MYC protein expression, as assessed by immunohistochemistry, was present in almost all sebaceous carcinoma cases. Our findings support the concept that alterations in TP53 and RB1 are the commonest alterations in sebaceous carcinoma, and suggest that MYC may contribute to the oncogenesis of these tumors. 相似文献
992.
Polyphasic study of microbial communities of two Spanish farmhouse goats' milk cheeses from Sierra de Aracena 总被引:1,自引:0,他引:1
Antonio M. Martín-Platero Mercedes Maqueda Eva Valdivia Jessica Purswani Manuel Martínez-Bueno 《Food microbiology》2009
The microbial communities present in 2 different types of farmhouse goats' milk cheese from the Aracena mountains (southwest Spain), Quesailla Arochena (hard cheese) and Torta Arochena (soft cheese), have been studied using both culture-dependent and culture-independent techniques. All bacterial isolates were clustered by using randomly amplified polymorphic DNA (RAPD) and identified by 16S rRNA gene sequencing, species-specific PCR and multiplex PCR. Thus a total of 26 different species were identified, the majority belonging to the lactic-acid bacteria (LAB), mainly represented by Lactococcus lactis and Lactobacillus species such as Lactobacillus plantarum and Lactobacillus paracasei, together with a significant proportion of enterococci. Amongst the non-lactic-acid bacteria (NLAB), which represented 37% of the isolates in Torta Arochena, enterobacteria were the most important, Hafnia alvei and Serratia liquefaciens being the predominant species in Quesailla Arochena and Torta Arochena respectively. Moreover, RAPD analysis of the isolates revealed that most of the genotypes were specific to one of the cheeses, although a few genotypes common to both cheeses were found. 相似文献
993.
Novel phenolic type of thermoset resins were synthesized, and their mechanical and toughness properties were evaluated. Phenol Formaldehyde (PF) phenolic resins were modified to broaden their applications for modern composite structures. A first modification consisted of copolymerization of Phenol with Cardanol during the synthesis of resole phenolic (CPF) resins. The modified phenolic resins (CPF) were prepared at various molar ratios of total Phenol to Formaldehyde (F : P ratio) and with different weight ratios of Phenol to Cardanol. CPF resins with a maximum content of 40 wt % of Cardanol were synthesized and used. The CPF resins were applied as a plasticizer and toughening agent to the base PF resins. Both resins (CPF/PF) were mixed in different proportions, and their thermal and mechanical properties were then established. A full miscibility of the two resins was observed with the formation of a single‐phase system. An increase in the content of Cardanol resulted in a proportional increase of the flexural strength and fracture toughness together with a decrease of the flexural modulus of the cured CPF/PF resins. Further increased plasticizing and toughening effect was also observed by the blending of the CPF resins with propylene glycol. The higher toughness and flexibility effect of the CPF resins was obtained with a F : P molar ratio equal to 1.25 and with a Cardanol content of 40% (w/w). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
994.
Taylor N. Plank Jessica L. Drake Daniel K. Kim Timothy W. Funk 《Advanced Synthesis \u0026amp; Catalysis》2012,354(4):597-601
A series of air‐stable, nitrile‐ligated (cyclopentadienone)iron dicarbonyl compounds was synthesized and their activities as catalysts in the transfer reduction of acetophenone were explored. While all were active catalysts, the acetonitrile adduct was chosen for further study and was found to be active in the transfer reduction of aldehydes and ketones and in the Oppenauer‐type oxidation of secondary alcohols. The acetonitrile catalyst exhibited activities similar to those of an analogous air‐sensitive iron hydride, but unlike the iron hydride it was unreactive in carbonyl reductions using hydrogen gas. 相似文献
995.
Vibrio cholerae is well recognized as the causative agent of cholera, an acute intestinal infection characterized by watery diarrhea that may lead to dehydration and death in some cases. V. cholerae is a natural inhabitant of the aquatic environment in the tropical regions. Jakarta has the highest percentage of individuals affected by sporadic diarrheal illness compared with other areas in Indonesia. Inadequate safety measures for drinking water supplies, improper sanitation, and poor hygiene can increase the risk of cholera outbreaks. Few studies have been conducted on the prevalence of these bacteria in ice and beverages that are popularly sold and consumed in Jakarta. In this study, we detected and quantified V. cholerae from ice and beverages collected from several areas in five regions of Jakarta. Levels of V. cholerae in both ice and beverages were determined with the three-tube most-probable-number (MPN) method and ranged from < 0.3 to > 110 MPN/ml. The presence of regulatory and virulence gene sequences was determined by using uniplex and multiplex PCR assays. Of 110 samples tested, 33 (30%) were positive for V. cholerae; 21 (64%) were ice samples and the remaining 12 (36%) were beverages. A total of 88 V. cholerae strains were isolated, based on the presence of the toxR gene sequence identified by PCR. Other genetic markers, such as hlyA (59%), ompU (16%), and ctxA (19%), also were found during the search for potential pathogenic strains. The detection and isolation of potentially harmful V. cholerae from ice and beverages in Jakarta indicate that these products pose a health risk from choleragenic vibrios, particularly because of the emergence of classical biotypes of V. cholerae O1 and potentially harmful non-O1 serovars of this species. 相似文献
996.
Yang YY Gray JL Furlong ET Davis JG Revello RC Borch T 《Environmental science & technology》2012,46(5):2746-2754
The potential presence of steroid hormones in runoff from sites where biosolids have been used as agricultural fertilizers is an environmental concern. A study was conducted to assess the potential for runoff of seventeen different hormones and two sterols, including androgens, estrogens, and progestogens from agricultural test plots. The field containing the test plots had been applied with biosolids for the first time immediately prior to this study. Target compounds were isolated by solid-phase extraction (water samples) and pressurized solvent extraction (solid samples), derivatized, and analyzed by gas chromatography-tandem mass spectrometry. Runoff samples collected prior to biosolids application had low concentrations of two hormones (estrone <0.8 to 2.23 ng L(-1) and androstenedione <0.8 to 1.54 ng L(-1)) and cholesterol (22.5 ± 3.8 μg L(-1)). In contrast, significantly higher concentrations of multiple estrogens (<0.8 to 25.0 ng L(-1)), androgens (<2 to 216 ng L(-1)), and progesterone (<8 to 98.9 ng L(-1)) were observed in runoff samples taken 1, 8, and 35 days after biosolids application. A significant positive correlation was observed between antecedent rainfall amount and hormone mass loads (runoff). Hormones in runoff were primarily present in the dissolved phase (<0.7-μm GF filter), and, to a lesser extent bound to the suspended-particle phase. Overall, these results indicate that rainfall can mobilize hormones from biosolids-amended agricultural fields, directly to surface waters or redistributed to terrestrial sites away from the point of application via runoff. Although concentrations decrease over time, 35 days is insufficient for complete degradation of hormones in soil at this site. 相似文献
997.
Harel Z Wald R Liu JJ Bell CM 《Hemodialysis international. International Symposium on Home Hemodialysis》2012,16(2):286-293
Chronic dialysis patients are a vulnerable population that may be highly susceptible to medical errors, particularly when they are hospitalized. We performed a chart review of chronic hemodialysis patients admitted to surgical services at a tertiary care center in order to characterize lapses in patient safety. We conducted a retrospective chart review of admissions of patients receiving chronic hemodialysis to various surgical services at St. Michael's Hospital from January 1, 2009 to December 31, 2010. For each hospitalization, we collected data on four process of care indicators of potential safety lapses. When these lapses were identified, we sought to determine whether: (i) the lapse was detected and remedied; and (ii) the lapse resulted in an adverse event. Among the 41 patients, 96 process of care lapses were identified. Multiple lapses were detected in 83% of the cohort. Failure to order a renal diet (72%) occurred most often. There was one adverse event. Process of care lapses were detected 39% of the time, usually within 1.5 days of their occurrence. Patients receiving chronic hemodialysis admitted to surgical services experience multiple lapses in patient safety, which often remain undetected. As such, it is imperative that these patients be closely monitored in order to mitigate against potential adverse events. 相似文献
998.
Kim Y Hellmuth TJ Sysoiev D Pauly F Pietsch T Wolf J Erbe A Huhn T Groth U Steiner UE Scheer E 《Nano letters》2012,12(7):3736-3742
We report on the experimental analysis of the charge transport through single-molecule junctions of the open and closed isomers of photoswitching molecules. Sulfur-free diarylethene molecules are developed and studied via electrical and optical measurements as well as density functional theory calculations. The single-molecule conductance and the current-voltage characteristics are measured in a mechanically controlled break-junction system at low temperatures. Comparing the results with the single-level transport model, we find an unexpected behavior of the current-dominating molecular orbital upon isomerization. We show that both the side chains and end groups of the molecules are crucial to understand the charge transport mechanism of photoswitching molecular junctions. 相似文献
999.
Heterostructure nanowires have many potential applications due to the avoidance of interface defects by lateral strain relaxation. However, most heterostructure semiconductor nanowires suffer from persistent interface compositional grading, normally attributed to the dissolution of growth species in the common alloy seed particles. Although progress has been made for some material systems, most binary material combinations remain problematic due to the interaction of growth species in the alloy. In this work we investigate the formation of interfaces in InAs-GaAs heterostructures experimentally and theoretically and demonstrate a technique to attain substantially sharper interfaces. We show that by pulsing the Ga source during heterojunction formation, In is pushed out before GaAs growth initiates, greatly reducing In carry-over. This procedure will be directly applicable to any nanowire system with finite nonideal solubility of growth species in the alloy seed particle and greatly improve the applicability of these structures in future devices. 相似文献
1000.
A microstructure-dependent nonlinear theory for axisymmetric bending of circular plates, which accounts for through-thickness power-law variation of a two-constituent material, is developed using the principle of virtual displacements. The formulation is based on a modified couple stress theory, power-law variation of the material, temperature-dependent properties, and the von Kármán geometric nonlinearity. Classical and first-order shear deformation theories are considered in the study. The modified couple stress theory contains a material length scale parameter that can capture the size effect in a functionally graded material plate. The theories presented herein can be used to develop analytical solutions of bending, buckling, and free vibration for the linear case and finite-element models for the nonlinear case to determine the effect of the geometric nonlinearity, power-law index, and microstructure-dependent constitutive relations on linear and nonlinear response of axisymmetric analysis of circular plates. 相似文献