首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   513篇
  免费   38篇
电工技术   4篇
综合类   1篇
化学工业   106篇
金属工艺   5篇
机械仪表   10篇
建筑科学   55篇
矿业工程   1篇
能源动力   22篇
轻工业   54篇
水利工程   3篇
石油天然气   1篇
无线电   60篇
一般工业技术   119篇
冶金工业   24篇
原子能技术   3篇
自动化技术   83篇
  2023年   9篇
  2022年   9篇
  2021年   26篇
  2020年   14篇
  2019年   14篇
  2018年   25篇
  2017年   14篇
  2016年   16篇
  2015年   15篇
  2014年   23篇
  2013年   28篇
  2012年   41篇
  2011年   46篇
  2010年   24篇
  2009年   27篇
  2008年   27篇
  2007年   29篇
  2006年   27篇
  2005年   31篇
  2004年   19篇
  2003年   15篇
  2002年   12篇
  2001年   4篇
  2000年   9篇
  1999年   7篇
  1998年   2篇
  1997年   4篇
  1995年   3篇
  1994年   3篇
  1993年   4篇
  1992年   2篇
  1991年   1篇
  1990年   3篇
  1989年   3篇
  1988年   1篇
  1987年   2篇
  1986年   3篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1981年   2篇
  1972年   1篇
  1963年   1篇
  1958年   1篇
排序方式: 共有551条查询结果,搜索用时 15 毫秒
101.
Ceramic Matrix Composites (CMCs) are increasingly demanded especially for the production of structural components for several industries such as aerospace because of their excellent thermo-mechanical and fatigue properties. As one of the last production steps final machining is necessary to meet the required tolerances. From the economic point of view final machining of CMCs is highly critical and special knowledge is assumed to avoid irreparable damage, because of their heterogeneous, anisotropic and brittle nature. In this work diamond grinding and diamond milling have been applied to a 2D C/C-SiC composite at various feed rates and cutting speeds and in both main laminate directions, in-plane and out-of-plane. The microstructures of in-plane and out-of-plane machining indicate different material removal mechanisms due to different composite architecture. Increasing feed rate leads generally to more surface defects and consequently to higher roughness. Little influence on the four-point-bending strength was observed when changing the machining speed.  相似文献   
102.
Imaging mass spectrometry (IMS) is a rapidly advancing molecular imaging modality that can map the spatial distribution of molecules with high chemical specificity. IMS does not require prior tagging of molecular targets and is able to measure a large number of ions concurrently in a single experiment. While this makes it particularly suited for exploratory analysis, the large amount and high-dimensional nature of data generated by IMS techniques make automated computational analysis indispensable. Research into computational methods for IMS data has touched upon different aspects, including spectral preprocessing, data formats, dimensionality reduction, spatial registration, sample classification, differential analysis between IMS experiments, and data-driven fusion methods to extract patterns corroborated by both IMS and other imaging modalities. In this work, we review unsupervised machine learning methods for exploratory analysis of IMS data, with particular focus on (a) factorization, (b) clustering, and (c) manifold learning. To provide a view across the various IMS modalities, we have attempted to include examples from a range of approaches including matrix assisted laser desorption/ionization, desorption electrospray ionization, and secondary ion mass spectrometry-based IMS. This review aims to be an entry point for both (i) analytical chemists and mass spectrometry experts who want to explore computational techniques; and (ii) computer scientists and data mining specialists who want to enter the IMS field. © 2019 The Authors. Mass Spectrometry Reviews published by Wiley Periodicals, Inc. Mass SpecRev 00:1–47, 2019.  相似文献   
103.
Emerging research demonstrates that co-inhibitory immune checkpoints (ICs) remain the most promising immunotherapy targets in various malignancies. Nonetheless, ICIs have offered insignificant clinical benefits in the treatment of advanced prostate cancer (PCa) especially when they are used as monotherapies. Current existing PCa treatment initially offers an improved clinical outcome and overall survival (OS), however, after a while the treatment becomes resistant leading to aggressive and uncontrolled disease associated with increased mortality and morbidity. Concurrent combination of the ICIs with radionuclides therapy that has rapidly emerged as safe and effective targeted approach for treating PCa patients may shift the paradigm of PCa treatment. Here, we provide an overview of the contextual contribution of old and new emerging inhibitory ICs in PCa, preclinical and clinical studies supporting the use of these ICs in treating PCa patients. Furthermore, we will also describe the potential of using a combinatory approach of ICIs and radionuclides therapy in treating PCa patients to enhance efficacy, durable cancer control and OS. The inhibitory ICs considered in this review are cytotoxic T-lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD1), V-domain immunoglobulin suppressor of T cell activation (VISTA), indoleamine 2,3-dioxygenase (IDO), T cell Immunoglobulin Domain and Mucin Domain 3 (TIM-3), lymphocyte-activation gene 3 (LAG-3), T cell immunoreceptor with Ig and ITIM domains (TIGIT), B7 homolog 3 (B7-H3) and B7-H4.  相似文献   
104.
105.
The synthesis of C/C-SiC via liquid silicon infiltration (LSI) with thermoplastic carbon precursors can lead to the formation of macropores in the C/C state. The macro-pore pattern formation can be controlled and used as a new level in microstructure for ceramic matrix composites. The pore formation occurs in the CFRP state with the remelting of the thermoplastic matrix and can be fixed to the C/C state after liquid phase pyrolysis. The macro-pores are primarily induced by a non-linear elastic recovery of the fiber preform and not via gas formation and release during pyrolysis. The formation of the macroporosity is described and explained. These pores can be tailored by process control in size and shape. The pore shapes can vary from isolated spherical pores to an interconnected tube like macro-pore network. The relationship between starting setting variables of the fiber preform, the process conditions, and the resulting structure are discussed.  相似文献   
106.
Cupin-type cysteine dioxygenases (CDOs) are non-heme iron enzymes that occur in animals, plants, bacteria and in filamentous fungi. In this report, we show that agaricomycetes contain an entirely unrelated type of CDO that emerged by convergent evolution from enzymes involved in the biosynthesis of ergothioneine. The activity of this CDO type is dependent on the ergothioneine precursor N-α-trimethylhistidine. The metabolic link between ergothioneine production and cysteine oxidation suggests that the two processes might be part of the same chemical response in fungi, for example against oxidative stress.  相似文献   
107.
Expression of progesterone receptor (PR) in various organs of sexually immature chickens and after estrogen treatment was studied by immunohistochemical and Western blotting analyses. Constitutive PR expression was observed in the mesothelium and stroma of the esophagus, proventriculus, liver, spleen, pancreas, heart and lung. In the urogenital tract, PR was expressed in the mesothelial and stromal cells and smooth muscle of blood vessels. Estrogen treatment induced PR expression in the stroma and smooth muscle of the gall bladder and in the epithelium and stroma of the trachea. In the ovary of immature chickens PR was localized in the epithelium, stroma and smooth muscle and was induced in the granulosal cells by estrogen. In most tissues there was more PR-B than PR-A expression and this PR-B dominance remained after estrogen treatment. These results suggest that progesterone and estrogen may have physiological effects on many organs outside the genital tract not previously known as steroid-target tissues.  相似文献   
108.
Ss in 2 studies were asked to report on 32 emotional states. Ss were asked to remember instances of experiencing these states and, for each experience, to fill out a questionnaire on appraisal dimensions and action readiness modes. Appraisal patterns as well as patterns of action readiness show distinct relations to various emotional categories, or names; the contributions of both kinds of components to emotion distinction are in part independent and additive. Multiple correlations, predicting action readiness scores from appraisal scores, demonstrated significant relations between particular modes of action readiness and particular appraisal patterns. The results of these studies are interpreted as providing support for the view that emotions can be regarded both as experiences of forms of appraisal and as states of action readiness. Emotions can profitably be analyzed in terms of sets of components, in which action readiness components take an important share. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
109.
Continuous fermentations using Clostridium spp. DSM 2152 immobilised in calcium alginate beads to produce butanol and isopropanol from glucose were carried out in a fluidised bed reactor with liquid recycle (FBR, 10.9 dm3 working volume, 41 % solids) and in a gas lift loop reactor (GLR, 11.4 dm3 working volume, 32% solids). In the FBR in-situ produced non-coalescing gas bubbles had a negligible influence on the fluidisation pattern and the steady state results of the fermentation were in accordance with those predicted by a reactor model. The FBR was operated reliably for 5 weeks without decrease of activity. The GLR behaved as a three phase reactor because of the recycled fermentation gas. The steady state fermentation results were as predicted by the GLR model. Scale up to a 50 m3 FBR and a 65 m3 GLR led to development of a plug flow with recycle model for the FBR and a stirred tank model for the GLR. On the basis of overall reactor performance and ease of integration with a simultaneous product recovery the FBR is preferred to the GLR for application in a large scale butanol/isopropanol process using immobilised Clostridia spp.  相似文献   
110.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号