全文获取类型
收费全文 | 1783篇 |
免费 | 65篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 38篇 |
综合类 | 4篇 |
化学工业 | 450篇 |
金属工艺 | 30篇 |
机械仪表 | 52篇 |
建筑科学 | 84篇 |
矿业工程 | 3篇 |
能源动力 | 43篇 |
轻工业 | 176篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 148篇 |
一般工业技术 | 307篇 |
冶金工业 | 168篇 |
原子能技术 | 12篇 |
自动化技术 | 327篇 |
出版年
2023年 | 22篇 |
2022年 | 54篇 |
2021年 | 67篇 |
2020年 | 33篇 |
2019年 | 36篇 |
2018年 | 41篇 |
2017年 | 43篇 |
2016年 | 67篇 |
2015年 | 34篇 |
2014年 | 51篇 |
2013年 | 118篇 |
2012年 | 95篇 |
2011年 | 104篇 |
2010年 | 77篇 |
2009年 | 86篇 |
2008年 | 76篇 |
2007年 | 85篇 |
2006年 | 69篇 |
2005年 | 57篇 |
2004年 | 54篇 |
2003年 | 45篇 |
2002年 | 48篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 51篇 |
1997年 | 50篇 |
1996年 | 22篇 |
1995年 | 25篇 |
1994年 | 28篇 |
1993年 | 22篇 |
1992年 | 16篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1971年 | 6篇 |
1970年 | 4篇 |
1966年 | 5篇 |
1932年 | 4篇 |
排序方式: 共有1853条查询结果,搜索用时 15 毫秒
31.
Guido Camata Enrico Spacone Riadh Al-Mahaidi Victor Saouma 《Canadian Metallurgical Quarterly》2004,8(6):528-538
The failure mechanisms of reinforced concrete (RC) members change due to the application of externally bonded fiber-reinforced polymer reinforcement. Although an extensive literature is available describing the failure mechanisms of poststrengthened flexural systems, brittle failure modes caused by bond failure, such as midspan debonding and end peeling, need to be further investigated in order to identify and quantify the fracture processes that result in bond failure. Simplified experimental tests have been designed to idealize the bond between the laminate and the RC member. However, it is unclear how the simplified test results can be related to the actual flexural debonding failures. This paper investigates and compares two bond failure tests: a simplified test (or simple shear test) and a recently proposed shear/normal test. After discussing the characteristics of both tests and how they relate to the midspan debonding and end peeling failures, the shear/normal test is studied in more detail using a nonlinear finite-element fracture mechanics program. The program accounts for cohesive localized and distributed concrete crack damage and is capable of describing the geometrical discontinuities that induce different brittle failure mechanisms. The numerical results compare well with available experimental data and help explain the crack formation and propagation pattern up to specimen failure. Parametric studies are presented to elucidate the influence of different material parameters on the failure mechanisms. 相似文献
32.
Biological membranes are often poorly visible with the electron microscope after high‐pressure freezing and freeze‐substitution. The water content of the sample and of the substitution medium is one factor among others that strongly influences membrane visibility. In order to investigate this effect, high‐pressure frozen yeast cells, rat‐pancreas tissue and arthropod tissue were freeze‐substituted with and without adding water to the substitution medium. The visibility of the biological membranes was generally improved if the substitution medium contained 1–5% water. The effect was especially pronounced in yeast cells, where membrane visibility was poor after freeze‐substitution with water‐free medium but good after addition of 5% water to the substitution medium. 相似文献
33.
Belforte G Eula G 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2012,226(1):21-32
Functional magnetic resonance imaging analysis has made major strides in recent years, both because of the development of new scanners and owing to magnetic resonance compatible systems that make it possible to stimulate parts of the human body during analysis. The significant gains in our knowledge of the brain that can thus be achieved justify efforts to construct machines with control circuits suitable for this purpose. This paper presents a magnetic resonance compatible mechatronic device with electropneumatic control that can be used to move one or both feet during functional magnetic resonance imaging analysis of the cerebral motor zones. The system is innovative and original. The results obtained at the end of the investigation were good, and demonstrated that the design is feasible. 相似文献
34.
Definition of the problem
The concept of “ethics” has recently been incorporated into both the 2014 Model Professional Code for Dentists and the current version of the “National Competence-Based Catalog of Learning Objectives in Dental Medicine” (NKLZ, Nationaler Kompetenzbasierter Lernzielkatalog Zahnmedizin). The study presented here addresses the question which relevance this has for the relevance of the new concept accomplished for the dental profession and society.Arguments
To this end, the societal processes that are related to the autonomous freedom of action of the dental profession are discussed. Therefore the sociological fields of discourse such as profession (and the effect of its constitutive antinomies), trust, education, expertise, practice of treatments and sanction are reviewed for their potential of having connections to each other and serving as a structural frame concerning an ethically reflected acting of the professional. The basis of the professional freedom of action is the trust of society and the individual patient in the professionally acting dentist.Conclusion
The study arrives at the conclusion that it was a serious omission for many decades not to make young dentists aware of the ethical foundations of dental activity on an institutionally established basis and thus failing to encourage them to constantly reflect their professional expertise in relation to the problems to be solved. This deficit has now been identified. It is absolutely essential to implement an institutionalized structure dealing with ethical questions within the scope of dental medicine.35.
36.
37.
38.
Kay-Arne Walther Jos Roberto Gonzales Sabine Grger Benjamin Ehmke Dogan Kaner Katrin Lorenz Peter Eickholz Thomas Kocher Ti-Sun Kim Ulrich Schlagenhauf Raphael Koch Jrg Meyle 《International journal of molecular sciences》2022,23(13)
Periodontitis is a multifactorial disease. The aim of this explorative study was to investigate the role of Interleukin-(IL)-1, IL-4, GATA-3 and Cyclooxygenase-(COX)-2 polymorphisms after non-surgical periodontal therapy with adjunctive systemic antibiotics (amoxicillin/metronidazole) and subsequent maintenance in a Caucasian population. Analyses were performed using blood samples from periodontitis patients of a multi-center trial (ClinicalTrials.gov =ABPARO-study). Polymorphisms were analyzed using quantitative real-time PCR. Clinical attachment levels (CAL), percentage of sites showing further attachment loss (PSAL) ≥1.3 mm, bleeding on probing (BOP) and plaque score were assessed. Exploratory statistical analysis was performed. A total of 209 samples were genotyped. Patients carrying heterozygous genotypes and single-nucleotide-polymorphisms (SNP) on the GATA-3-IVS4 +1468 gene locus showed less CAL loss than patients carrying wild type. Heterozygous genotypes and SNPs on the IL-1A-889, IL-1B +3954, IL-4-34, IL-4-590, GATA-3-IVS4 +1468 and COX-2-1195 gene loci did not influence CAL. In multivariate analysis, CAL was lower in patients carrying GATA-3 heterozygous genotypes and SNPs than those carrying wild-types. For the first time, effects of different genotypes were analyzed in periodontitis progression after periodontal therapy and during supportive treatment using systemic antibiotics demonstrating a slight association of GATA-3 gene locus with CAL. This result suggests that GATA-3 genotypes are a contributory but non-essential risk factor for periodontal disease progression. NCT00707369相似文献
39.
Axel Haarmann Lena Zimmermann Michael Bieber Christine Silwedel Guido Stoll Michael K. Schuhmann 《International journal of molecular sciences》2022,23(13)
In large vessel occlusion stroke, recanalization to restore cerebral perfusion is essential but not necessarily sufficient for a favorable outcome. Paradoxically, in some patients, reperfusion carries the risk of increased tissue damage and cerebral hemorrhage. Experimental and clinical data suggest that endothelial cells, representing the interface for detrimental platelet and leukocyte responses, likely play a crucial role in the phenomenon referred to as ischemia/reperfusion (I/R)-injury, but the mechanisms are unknown. We aimed to determine the role of endoglin in cerebral I/R-injury; endoglin is a membrane-bound protein abundantly expressed by endothelial cells that has previously been shown to be involved in the maintenance of vascular homeostasis. We investigated the expression of membranous endoglin (using Western blotting and RT-PCR) and the generation of soluble endoglin (using an enzyme-linked immunosorbent assay of cell culture supernatants) after hypoxia and subsequent reoxygenation in human non-immortalized brain endothelial cells. To validate these in vitro data, we additionally examined endoglin expression in an intraluminal monofilament model of permanent and transient middle cerebral artery occlusion in mice. Subsequently, the effects of recombinant human soluble endoglin were assessed by label-free impedance-based measurement of endothelial monolayer integrity (using the xCELLigence DP system) and immunocytochemistry. Endoglin expression is highly inducible by hypoxia in human brain endothelial monolayers in vitro, and subsequent reoxygenation induced its shedding. These findings were corroborated in mice during MCAO; an upregulation of endoglin was displayed in the infarcted hemispheres under occlusion, whereas endoglin expression was significantly diminished after transient MCAO, which is indicative of shedding. Of note is the finding that soluble endoglin induced an inflammatory phenotype in endothelial monolayers. The treatment of HBMEC with endoglin resulted in a decrease in transendothelial resistance and the downregulation of VE-cadherin. Our data establish a novel mechanism in which hypoxia triggers the initial endothelial upregulation of endoglin and subsequent reoxygenation triggers its release as a vasoactive mediator that, when rinsed into adjacent vascular beds after recanalization, can contribute to cerebral reperfusion injury. 相似文献
40.
Kaan
cal Michael U. Gutmann Guido Sanguinetti Ramon Grima 《Journal of the Royal Society Interface》2022,19(192)
Estimating uncertainty in model predictions is a central task in quantitative biology. Biological models at the single-cell level are intrinsically stochastic and nonlinear, creating formidable challenges for their statistical estimation which inevitably has to rely on approximations that trade accuracy for tractability. Despite intensive interest, a sweet spot in this trade-off has not been found yet. We propose a flexible procedure for uncertainty quantification in a wide class of reaction networks describing stochastic gene expression including those with feedback. The method is based on creating a tractable coarse-graining of the model that is learned from simulations, a synthetic model, to approximate the likelihood function. We demonstrate that synthetic models can substantially outperform state-of-the-art approaches on a number of non-trivial systems and datasets, yielding an accurate and computationally viable solution to uncertainty quantification in stochastic models of gene expression. 相似文献