全文获取类型
收费全文 | 12168篇 |
免费 | 1164篇 |
国内免费 | 335篇 |
专业分类
电工技术 | 272篇 |
综合类 | 1363篇 |
化学工业 | 2612篇 |
金属工艺 | 225篇 |
机械仪表 | 318篇 |
建筑科学 | 4711篇 |
矿业工程 | 795篇 |
能源动力 | 207篇 |
轻工业 | 591篇 |
水利工程 | 300篇 |
石油天然气 | 625篇 |
武器工业 | 18篇 |
无线电 | 128篇 |
一般工业技术 | 782篇 |
冶金工业 | 288篇 |
原子能技术 | 134篇 |
自动化技术 | 298篇 |
出版年
2024年 | 27篇 |
2023年 | 122篇 |
2022年 | 259篇 |
2021年 | 334篇 |
2020年 | 329篇 |
2019年 | 284篇 |
2018年 | 261篇 |
2017年 | 375篇 |
2016年 | 383篇 |
2015年 | 392篇 |
2014年 | 705篇 |
2013年 | 789篇 |
2012年 | 966篇 |
2011年 | 985篇 |
2010年 | 713篇 |
2009年 | 694篇 |
2008年 | 659篇 |
2007年 | 814篇 |
2006年 | 713篇 |
2005年 | 610篇 |
2004年 | 493篇 |
2003年 | 416篇 |
2002年 | 336篇 |
2001年 | 326篇 |
2000年 | 264篇 |
1999年 | 226篇 |
1998年 | 185篇 |
1997年 | 276篇 |
1996年 | 138篇 |
1995年 | 115篇 |
1994年 | 83篇 |
1993年 | 68篇 |
1992年 | 71篇 |
1991年 | 50篇 |
1990年 | 39篇 |
1989年 | 45篇 |
1988年 | 37篇 |
1987年 | 22篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1963年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Theodoros Eleftheriadis Georgios Pissas Marta Crespo Evdokia Nikolaou Vassilios Liakopoulos Ioannis Stefanidis 《International journal of molecular sciences》2021,22(4)
Direct allorecognition is the earliest and most potent immune response against a kidney allograft. Currently, it is thought that passenger donor professional antigen-presenting cells (APCs) are responsible. Further, many studies support that graft ischemia-reperfusion injury increases the probability of acute rejection. We evaluated the possible role of primary human proximal renal tubular epithelial cells (RPTECs) in direct allorecognition by CD4+ T-cells and the effect of anoxia-reoxygenation. In cell culture, we detected that RPTECs express all the required molecules for CD4+ T-cell activation (HLA-DR, CD80, and ICAM-1). Anoxia-reoxygenation decreased HLA-DR and CD80 but increased ICAM-1. Following this, RPTECs were co-cultured with alloreactive CD4+ T-cells. In T-cells, zeta chain phosphorylation and c-Myc increased, indicating activation of T-cell receptor and co-stimulation signal transduction pathways, respectively. T-cell proliferation assessed with bromodeoxyuridine assay and with the marker Ki-67 increased. Previous culture of RPTECs under anoxia raised all the above parameters in T-cells. FOXP3 remained unaffected in all cases, signifying that proliferating T-cells were not differentiated towards a regulatory phenotype. Our results support that direct allorecognition may be mediated by RPTECs even in the absence of donor-derived professional APCs. Also, ischemia-reperfusion injury of the graft may enhance the above capacity of RPTECs, increasing the possibility of acute rejection. 相似文献
2.
Reliable prediction of flooding conditions is needed for sizing and operating packed extraction columns. Due to the complex interplay of physicochemical properties, operational parameters and the packing-specific properties, it is challenging to develop accurate semi-empirical or rigorous models with a high validity range. State of the art models may therefore fail to predict flooding accurately. To overcome this problem, a data-driven model based on Gaussian processes is developed to predict flooding for packed liquid-liquid and high-pressure extraction columns. The optimized Gaussian process for the liquid-liquid extraction column results in an average absolute relative error (AARE) of 15.23 %, whereas the algorithm for the high-pressure extraction column results in an AARE of 13.68 %. Both algorithms can predict flooding curves for different packing geometries and chemical systems precisely. 相似文献
3.
In this paper, the dynamic behaviors on the basis of simulation for high-purity heat integrated air separation column (HIASC) are studied. A nonlinear generic model control (GMC) scheme is proposed based on the nonlinear behavior analyses of a HIASC process, and an adaptive generic model control (AGMC) scheme is further presented to correct the model parameters online. Related internal model control (IMC) scheme and multi-loop PID (M-PID) scheme are also developed as the comparative base. The comparative researches are carried out among these linear and nonlinear control schemes in detail. The simulation research results show that the proposed AGMC schemes present advantages in both servo control and regulatory control for the high-purity HIASC. 相似文献
4.
5.
Jincy Joy Jessica Pereira Rachida Aid‐Launais Graciela Pavon‐Djavid Alok R Ray Didier Letourneur Anne Meddahi‐Pell Bhuvanesh Gupta 《Polymer International》2019,68(7):1367-1377
The work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry 相似文献
6.
根据延迟焦化装置露天栈桥的工程设计实践,围绕一炉两塔(一个加热炉两个焦炭塔)的焦化装置,分析了露天栈桥设计中的要点及难点,对其在平面布置、基础安排和吊车梁选型等设计方面做一些介绍和论述。 相似文献
7.
8.
本文以NH3-H2O系统Gibbs自由能、熵、焓和汽液相平衡的热力学模型为基础,用松弛法进行了无水氨精馏塔的模拟计算。改变无水氨采出比、回流比(直汽量)和进料板位置均影响蒸馏效果。 相似文献
9.
10.