全文获取类型
收费全文 | 941篇 |
免费 | 38篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 202篇 |
金属工艺 | 10篇 |
机械仪表 | 19篇 |
建筑科学 | 36篇 |
矿业工程 | 6篇 |
能源动力 | 20篇 |
轻工业 | 137篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
无线电 | 54篇 |
一般工业技术 | 147篇 |
冶金工业 | 222篇 |
原子能技术 | 4篇 |
自动化技术 | 101篇 |
出版年
2023年 | 20篇 |
2022年 | 24篇 |
2021年 | 49篇 |
2020年 | 20篇 |
2019年 | 24篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 28篇 |
2015年 | 21篇 |
2014年 | 25篇 |
2013年 | 46篇 |
2012年 | 49篇 |
2011年 | 64篇 |
2010年 | 50篇 |
2009年 | 37篇 |
2008年 | 55篇 |
2007年 | 43篇 |
2006年 | 45篇 |
2005年 | 30篇 |
2004年 | 20篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 31篇 |
1997年 | 17篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有981条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
When using magnetic nanoparticles as a heating source for magnetic particle hyperthermia it is of particular interest to know if the particles are free to move in the interstitial fluid or are fixed to the tumour tissue. The immobilization state determines the relaxation behaviour of the administered particles and thus their specific heating power. To investigate this behaviour, magnetic multicore nanoparticles were injected into experimentally grown tumours in mice and magnetic heating treatment was carried out in an alternating magnetic field (H = 25 kA m(-1), f = 400 kHz). The tested particles were well suited for magnetic heating treatment as they heated a tumour of about 100 mg by about 22 K within the first 60 s. Upon sacrifice, histological tumour examination showed that the particles form spots in the tissue with a mainly homogeneous particle distribution in these spots. The magnetic ex vivo characterization of the removed tumour tissue gave clear evidence for the immobilization of the particles in the tumour tissue because the particles in the tumour showed the same magnetic behaviour as immobilized particles. Therefore, the particles are not able to rotate and a temperature increase due to Brown relaxation can be neglected. To accurately estimate the heating potential of magnetic materials, the respective environments influencing the nanoparticle mobility status have to be taken into account. 相似文献
945.
In the present work, we show that a porous alumina template can easily be filled with magnetic nanoparticles and then be sealed by a hot water treatment (by forming an aluminium oxyhydroxide (AlOOH) sealant layer). The porous layer then can be separated from the substrate by an etch to form free magnetic AlOOH nano-capsules. The process allows for a straightforward and highly defined size control of the magnetic units and can easily be scaled up. Furthermore, as AlOOH is biocompatible and has been used as a drug adjuvant for human use, the nanorod shaped capsules are highly promising for biomedical applications such as hyperthermal effects (heating in alternating magnetic fields). 相似文献
946.
Kettering M Richter H Wiekhorst F Bremer-Streck S Trahms L Kaiser WA Hilger I 《Nanotechnology》2011,22(50):505102
Localized magnetic heating treatments (hyperthermia, thermal ablation) using superparamagnetic iron oxide nanoparticles (MNPs) continue to be an active area of cancer research. For generating the appropriate heat to sufficiently target cell destruction, adequate MNP concentrations need to be accumulated into tumors. Furthermore, the knowledge of MNP bio-distribution after application and additionally after heating is significant, firstly because of the possibility of repeated heating treatments if MNPs remain at the target region and secondly to study potential adverse effects dealing with MNP dilution from the target region over time. In this context, little is known about the behavior of MNPs after intra-tumoral application and magnetic heating. Therefore, the present in vivo study on the bio-distribution of intra-tumorally injected MNPs in mice focused on MNP long term monitoring of pre and post therapy over seven days using multi-channel magnetorelaxometry (MRX). Subsequently, single-channel MRX was adopted to study the bio-distribution of MNPs in internal organs and tumors of sacrificed animals. We found no distinct change of total MNP amounts in vivo during long term monitoring. Most of the MNP amounts remained in the tumors; only a few MNPs were detected in liver and spleen and less than 1% of totally injected MNPs were excreted. Apparently, the application of magnetic heating and the induction of apoptosis did not affect MNP accumulation. Our results indicate that MNP mainly remained within the injection side after magnetic heating over a seven-days-observation and therefore not affecting healthy tissue. As a consequence, localized magnetic heating therapy of tumors might be applied periodically for a better therapeutic outcome. 相似文献
947.
The material properties of cytoskeletal F-actin networks facilitate a broad range of cellular behaviors, whereby in some situations cell shape is preserved in the presence of force and, at other times, force results in irreversible shape change. These behaviors strongly suggest that F-actin networks can variably deform elastically or viscously. While a significant amount is known about the regulation of the elastic stiffness of F-actin networks, our understanding of the regulation of viscous behaviors of F-actin networks is largely lacking. Here, we study the rheological behavior of F-actin networks formed with heavy meromyosin non-muscle IIB (NMMIIB). We show that NMMIIB quenched with ADP crosslinks F-actin into networks that, for sufficient densities, display stress stiffening behavior. By performing a series of creep tests, we show that densely crosslinked actin/NMMIIB-ADP networks undergo viscous deformation over a wide range of stresses, ranging from 0.001 to 10 Pa. At high stresses, networks that stress stiffen are also observed to shear thicken, whereby the effective viscosity increases as a function of stress. Shear thickening results in a reduction in the extent of irreversible, viscous deformation in actin/NMMIIB-ADP networks at high stresses compared to that expected for a linear viscoelastic material. Thus, viscous deformation contributes less to the overall mechanical response at high levels of applied force. Our results indicate mechanisms by which the fluid-like nature of the actomyosin cytoskeleton can be reduced under high load. 相似文献
948.
Biosynthesis of the Peptide Antibiotic Feglymycin by a Linear Nonribosomal Peptide Synthetase Mechanism
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Melanie Gonsior Dr. Agnes Mühlenweg Marcel Tietzmann Dr. Saskia Rausch Annette Poch Prof. Dr. Roderich D. Süssmuth 《Chembiochem : a European journal of chemical biology》2015,16(18):2610-2614
Feglymycin, a peptide antibiotic produced by Streptomyces sp. DSM 11171, consists mostly of nonproteinogenic phenylglycine‐type amino acids. It possesses antibacterial activity against methicillin‐resistant Staphylococcus aureus strains and antiviral activity against HIV. Inhibition of the early steps of bacterial peptidoglycan synthesis indicated a mode of action different from those of other peptide antibiotics. Here we describe the identification and assignment of the feglymycin (feg) biosynthesis gene cluster, which codes for a 13‐module nonribosomal peptide synthetase (NRPS) system. Inactivation of an NRPS gene and supplementation of a hydroxymandelate oxidase mutant with the amino acid l ‐Hpg proved the identity of the feg cluster. Feeding of Hpg‐related unnatural amino acids was not successful. This characterization of the feg cluster is an important step to understanding the biosynthesis of this potent antibacterial peptide. 相似文献
949.
Johannes Leierer Paul Perco Benedikt Hofer Susanne Eder Alexander Dzien Julia Kerschbaum Michael Rudnicki Gert Mayer 《International journal of molecular sciences》2021,22(13)
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disorder leading to deterioration of kidney function and end stage kidney disease (ESKD). A number of molecular processes are dysregulated in ADPKD but the exact mechanism of disease progression is not fully understood. We measured protein biomarkers being linked to ADPKD-associated molecular processes via ELISA in urine and serum in a cohort of ADPKD patients as well as age, gender and eGFR matched CKD patients and healthy controls. ANOVA and t-tests were used to determine differences between cohorts. Spearman correlation coefficient analysis was performed to assess coregulation patterns of individual biomarkers and renal function. Urinary epidermal growth factor (EGF) and serum apelin (APLN) levels were significantly downregulated in ADPKD patients. Serum vascular endothelial growth factor alpha (VEGFA) and urinary angiotensinogen (AGT) were significantly upregulated in ADPKD patients as compared with healthy controls. Arginine vasopressin (AVP) was significantly upregulated in ADPKD patients as compared with CKD patients. Serum VEGFA and VIM concentrations were positively correlated and urinary EGF levels were negatively correlated with urinary AGT levels. Urinary EGF and AGT levels were furthermore significantly associated with estimated glomerular filtration rate (eGFR) in ADPKD patients. In summary, altered protein concentrations in body fluids of ADPKD patients were found for the mechanistic markers EGF, APLN, VEGFA, AGT, AVP, and VIM. In particular, the connection between EGF and AGT during progression of ADPKD warrants further investigation. 相似文献
950.
Desiree Loreth Moritz Schuette Jenny Zinke Malte Mohme Andras Piffko Svenja Schneegans Julia Stadler Melanie Janning Sonja Loges Simon A. Joosse Katrin Lamszus Manfred Westphal Volkmar Müller Markus Glatzel Jakob Matschke Christoffer Gebhardt Stefan W. Schneider Iwona Belczacka Beate Volkmer Rüdiger Greinert Marie-Laure Yaspo Patrick N. Harter Klaus Pantel Harriet Wikman 《International journal of molecular sciences》2021,22(13)
Up to 40% of advance lung, melanoma and breast cancer patients suffer from brain metastases (BM) with increasing incidence. Here, we assessed whether circulating tumor cells (CTCs) in peripheral blood can serve as a disease surrogate, focusing on CD44 and CD74 expression as prognostic markers for BM. We show that a size-based microfluidic approach in combination with a semi-automated cell recognition system are well suited for CTC detection in BM patients and allow further characterization of tumor cells potentially derived from BM. CTCs were found in 50% (7/14) of breast cancer, 50% (9/18) of non-small cell lung cancer (NSCLC) and 36% (4/11) of melanoma patients. The next-generation sequencing (NGS) analysis of nine single CTCs from one breast cancer patient revealed three different CNV profile groups as well as a resistance causing ERS1 mutation. CD44 and CD74 were expressed on most CTCs and their expression was strongly correlated, whereas matched breast cancer BM tissues were much less frequently expressing CD44 and CD74 (negative in 46% and 54%, respectively). Thus, plasticity of CD44 and CD74 expression during trafficking of CTCs in the circulation might be the result of adaptation strategies. 相似文献