全文获取类型
收费全文 | 4182篇 |
免费 | 164篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 47篇 |
综合类 | 14篇 |
化学工业 | 914篇 |
金属工艺 | 86篇 |
机械仪表 | 94篇 |
建筑科学 | 176篇 |
矿业工程 | 13篇 |
能源动力 | 88篇 |
轻工业 | 503篇 |
水利工程 | 24篇 |
石油天然气 | 10篇 |
无线电 | 297篇 |
一般工业技术 | 671篇 |
冶金工业 | 866篇 |
原子能技术 | 50篇 |
自动化技术 | 499篇 |
出版年
2023年 | 26篇 |
2022年 | 48篇 |
2021年 | 77篇 |
2020年 | 47篇 |
2019年 | 70篇 |
2018年 | 55篇 |
2017年 | 64篇 |
2016年 | 104篇 |
2015年 | 104篇 |
2014年 | 114篇 |
2013年 | 141篇 |
2012年 | 132篇 |
2011年 | 215篇 |
2010年 | 166篇 |
2009年 | 166篇 |
2008年 | 160篇 |
2007年 | 167篇 |
2006年 | 108篇 |
2005年 | 127篇 |
2004年 | 103篇 |
2003年 | 102篇 |
2002年 | 96篇 |
2001年 | 66篇 |
2000年 | 73篇 |
1999年 | 99篇 |
1998年 | 219篇 |
1997年 | 145篇 |
1996年 | 130篇 |
1995年 | 100篇 |
1994年 | 78篇 |
1993年 | 88篇 |
1992年 | 52篇 |
1991年 | 49篇 |
1990年 | 47篇 |
1989年 | 38篇 |
1988年 | 36篇 |
1987年 | 33篇 |
1986年 | 45篇 |
1985年 | 45篇 |
1984年 | 36篇 |
1983年 | 24篇 |
1982年 | 25篇 |
1981年 | 29篇 |
1978年 | 27篇 |
1977年 | 47篇 |
1976年 | 50篇 |
1975年 | 28篇 |
1972年 | 32篇 |
1970年 | 26篇 |
1969年 | 22篇 |
排序方式: 共有4352条查询结果,搜索用时 15 毫秒
61.
Uwe Helmke 《Theory of Computing Systems》1986,19(1):155-187
This paper deals with the algebraic topology of the space
n,m
of complex reachable linear dynamical systems. Topological invariants such as the singular homology groups of
n,m
are explicitly computed and they are shown to coincide with those of a certain Grassmann manifold. From this some new results on the topology of rational transfer matrices with fixed McMillan degree are obtained. 相似文献
62.
Jan Haas Karen S. Frese Farbod Sedaghat-Hamedani Elham Kayvanpour Rewati Tappu Rouven Nietsch Oguz Firat Tugrul Michael Wisdom Carsten Dietrich Ali Amr Tanja Weis Torsten Niederdrnk Michael P. Murphy Thomas Krieg Marcus Drr Uwe Vlker Jens Fielitz Norbert Frey Stephan B. Felix Andreas Keller Hugo A. Katus Benjamin Meder 《International journal of molecular sciences》2021,22(4)
With more than 25 million people affected, heart failure (HF) is a global threat. As energy production pathways are known to play a pivotal role in HF, we sought here to identify key metabolic changes in ischemic- and non-ischemic HF by using a multi-OMICS approach. Serum metabolites and mRNAseq and epigenetic DNA methylation profiles were analyzed from blood and left ventricular heart biopsy specimens of the same individuals. In total we collected serum from n = 82 patients with Dilated Cardiomyopathy (DCM) and n = 51 controls in the screening stage. We identified several metabolites involved in glycolysis and citric acid cycle to be elevated up to 5.7-fold in DCM (p = 1.7 × 10−6). Interestingly, cardiac mRNA and epigenetic changes of genes encoding rate-limiting enzymes of these pathways could also be found and validated in our second stage of metabolite assessment in n = 52 DCM, n = 39 ischemic HF and n = 57 controls. In conclusion, we identified a new set of metabolomic biomarkers for HF. We were able to identify underlying biological cascades that potentially represent suitable intervention targets. 相似文献
63.
Asher Ornoy Maria Becker Liza Weinstein-Fudim Zivanit Ergaz 《International journal of molecular sciences》2021,22(6)
In spite of the huge progress in the treatment of diabetes mellitus, we are still in the situation that both pregestational (PGDM) and gestational diabetes (GDM) impose an additional risk to the embryo, fetus, and course of pregnancy. PGDM may increase the rate of congenital malformations, especially cardiac, nervous system, musculoskeletal system, and limbs. PGDM may interfere with fetal growth, often causing macrosomia, but in the presence of severe maternal complications, especially nephropathy, it may inhibit fetal growth. PGDM may also induce a variety of perinatal complications such as stillbirth and perinatal death, cardiomyopathy, respiratory morbidity, and perinatal asphyxia. GDM that generally develops in the second half of pregnancy induces similar but generally less severe complications. Their severity is higher with earlier onset of GDM and inversely correlated with the degree of glycemic control. Early initiation of GDM might even cause some increase in the rate of congenital malformations. Both PGDM and GDM may cause various motor and behavioral neurodevelopmental problems, including an increased incidence of attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Most complications are reduced in incidence and severity with the improvement in diabetic control. Mechanisms of diabetic-induced damage in pregnancy are related to maternal and fetal hyperglycemia, enhanced oxidative stress, epigenetic changes, and other, less defined, pathogenic mechanisms. 相似文献
64.
65.
Dr. Qingyun Tang Assist. Prof. Dr. Ioannis V. Pavlidis Dr. Christoffel P. S. Badenhorst Prof. Dr. Uwe T. Bornscheuer 《Chembiochem : a European journal of chemical biology》2021,22(16):2584-2590
Halide methyltransferases (HMTs) enable the enzymatic synthesis of S-adenosyl-l -methionine (SAM) from S-adenosyl-l -homocysteine (SAH) and methyl iodide. Characterisation of a range of naturally occurring HMTs and subsequent protein engineering led to HMT variants capable of synthesising ethyl, propyl, and allyl analogues of SAM. Notably, HMTs do not depend on chemical synthesis of methionine analogues, as required by methionine adenosyltransferases (MATs). However, at the moment MATs have a much broader substrate scope than the HMTs. Herein we provide an overview of the discovery and engineering of promiscuous HMTs and how these strategies will pave the way towards a toolbox of HMT variants for versatile chemo- and regioselective biocatalytic alkylations. 相似文献
66.
67.
68.
Ole Becker Peter Sopade Romain Bourdonnay Peter J. Halley George P. Simon 《Polymer Engineering and Science》2003,43(10):1683-1690
The effect of an organically surface modified layered silicate on the viscosity of various epoxy resins of different structures and different functionalities was investigated. Steady and dynamic shear viscosities of the epoxy resins containing 0–10 Wt% of the organoclay were determined using parallel plate rheology. Viscosity results were compared with those achieved through addition of a commonly used micronsized CaCO3 filler. It was found that changes in viscosities due to the different fillers were of the same order, since the layered silicate was only dispersed on a micron‐sized scale in the monomer (prior to reaction), as indicated by X‐ray diffraction measurements. Flow activation energies at a low frequency were determined and did not show any significant changes due to the addition of organoclay or CaCO3. Comparison between dynamic and steady shear experiments showed good agreement for low layered silicate concentrations below 7.5 wt%, i.e. the Cox‐Merz rule can be applied. Deviations from the Cox‐Merz rule appeared at and above 10 wt%, although such deviations were only slightly above experimental error. Most resin organoclay blends were well predicted by the Power Law model, only concentrations of 10 wt% and above requiring the Herschel‐Buckley (yield stress) model to achieve better fits. Wide‐angle X‐ray measurements have shown that the epoxy resin swells the layered silicate with an increase in the interlayer distance of approximately 15 Å, and that the rheology behavior is due to the lateral, micron‐size of these swollen tactoids. 相似文献
69.
M A Rossi S Zucoloto J E Dutra de Oliveira P F Becker J S Oliveira 《Archivos latinoamericanos de nutrición》1978,28(1):29-40
A study of the effect of long-term alcohol consumption on the liver of well-nourished rats is described. Rats fed for 16 weeks on a semipurified diet supplemented with high levels of vitamins and lipotropic factors and alcohol corresponding to 35% of the total caloric intake developed marked fatty changes of the liver. Mild fatty changes were observed in pair-fed controls receiving as isoenergetic equivalent of sucrose instead of alcohol. Intracellular hyaline bodies, corresponding ultrastructurally to giant mitochondria were abundantly found in the hepatocytes of alcoholic rats, while in the controls they were not seen. Te findings in this investigation are postulated to provide further evidence that the long-term intake of alcohol exerts a direct causative role in the pathogenesis of liver damage. 相似文献
70.
H. R. Spiegel J. Juilfs U. Neubert K. J. Euler J. W. Beck D. Besdo H. Winter H. Becker W. Neuberger R. Jung K. Herfort H. Bühler H. Göppl H. W. Hahnemann W. Siegel 《Forschung im Ingenieurwesen》1970,36(2):64-68
Ohne Zusammenfassung
VDI 相似文献