全文获取类型
收费全文 | 4546篇 |
免费 | 197篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 58篇 |
综合类 | 14篇 |
化学工业 | 686篇 |
金属工艺 | 59篇 |
机械仪表 | 62篇 |
建筑科学 | 183篇 |
矿业工程 | 4篇 |
能源动力 | 91篇 |
轻工业 | 313篇 |
水利工程 | 30篇 |
石油天然气 | 24篇 |
无线电 | 237篇 |
一般工业技术 | 554篇 |
冶金工业 | 1780篇 |
原子能技术 | 22篇 |
自动化技术 | 628篇 |
出版年
2023年 | 52篇 |
2022年 | 78篇 |
2021年 | 110篇 |
2020年 | 58篇 |
2019年 | 61篇 |
2018年 | 76篇 |
2017年 | 77篇 |
2016年 | 120篇 |
2015年 | 112篇 |
2014年 | 120篇 |
2013年 | 191篇 |
2012年 | 166篇 |
2011年 | 221篇 |
2010年 | 205篇 |
2009年 | 149篇 |
2008年 | 154篇 |
2007年 | 137篇 |
2006年 | 139篇 |
2005年 | 112篇 |
2004年 | 96篇 |
2003年 | 73篇 |
2002年 | 71篇 |
2001年 | 65篇 |
2000年 | 49篇 |
1999年 | 115篇 |
1998年 | 536篇 |
1997年 | 308篇 |
1996年 | 225篇 |
1995年 | 119篇 |
1994年 | 103篇 |
1993年 | 105篇 |
1992年 | 24篇 |
1991年 | 26篇 |
1990年 | 33篇 |
1989年 | 46篇 |
1988年 | 36篇 |
1987年 | 29篇 |
1986年 | 30篇 |
1985年 | 34篇 |
1984年 | 10篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 40篇 |
1976年 | 95篇 |
1975年 | 8篇 |
1968年 | 6篇 |
排序方式: 共有4745条查询结果,搜索用时 15 毫秒
1.
Michael Lommel Vera Froese Moritz Sieber Marvin Jentzsch Tim Bierewirtz Ümit Hasirci Tim Rese Josef Seefeldt Sebastian Schimek Ulrich Kertzscher Christian Oliver Paschereit 《Indoor air》2021,31(6):1860-1873
The SARS-CoV-2 pandemic has created a great demand for a better understanding of the spread of viruses in indoor environments. A novel measurement system consisting of one portable aerosol-emitting mannequin (emitter) and a number of portable aerosol-absorbing mannequins (recipients) was developed that can measure the spread of aerosols and droplets that potentially contain infectious viruses. The emission of the virus from a human is simulated by using tracer particles solved in water. The recipients inhale the aerosols and droplets and quantify the level of solved tracer particles in their artificial lungs simultaneously over time. The mobile system can be arranged in a large variety of spreading scenarios in indoor environments and allows for quantification of the infection probability due to airborne virus spreading. This study shows the accuracy of the new measurement system and its ability to compare aerosol reduction measures such as regular ventilation or the use of a room air purifier. 相似文献
2.
3.
Dr. Blijke S. Kroezen Gabriele Conti Benedetta Girardi Dr. Jonathan Cramer Dr. Xiaohua Jiang Dr. Said Rabbani Jennifer Müller Maja Kokot Enrico Luisoni Prof. Daniel Ricklin Dr. Oliver Schwardt Prof. Beat Ernst 《ChemMedChem》2020,15(18):1706-1719
Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6’-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6’-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved. 相似文献
4.
van Dick Rolf; Wagner Ulrich; Pettigrew Thomas F.; Christ Oliver; Wolf Carina; Petzel Thomas; Castro Vanessa Smith; Jackson James S. 《Canadian Metallurgical Quarterly》2004,87(2):211
Furthering G. W. Allport's (1954) contentions for optimal contact, the authors introduce a new construct: the perceived importance of contact. They propose that perceived importance is the best proximal predictor of contact's reduction of prejudice. If individuals have opportunities for contact at work or in the neighborhood, their chances to have intergroup acquaintances and friends increase. Intergroup contact among acquaintances and friends can be perceived as more or less important, which in turn determines intergroup evaluations. A 1st study shows that the new measure of perceived importance is indeed distinct from established quantity and quality indicators. The results are cross-validated in a 2nd study that also sheds light on the meaning of importance. In 3rd and 4th studies, structural equation analyses and a meta-analysis support the hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
SG Bryant 《Canadian Metallurgical Quarterly》1996,53(19):2339-40, 2343
6.
SG Rijpkema RG Herbes N Verbeek-De Kruif JF Schellekens 《Canadian Metallurgical Quarterly》1996,117(3):563-566
Epiglottic disruption is an uncommon injury usually associated with significant supraglottic trauma. This injury may be overlooked because of the difficulty in examining the larynx or other associated severe injuries. We present two cases of clinically unsuspected epiglottic disruption that were first seen on MR images of the neck. 相似文献
7.
SA Khotimchenko VM Kodentsova IA Alekseeva SG Vlaskina OA Vrzhesinskaia AA Sokol''nikov LA Kharitonchik IP Aleshko-Ozhevskií LV Sheviakova 《Canadian Metallurgical Quarterly》1997,43(3):158-164
Gamma delta T-Cells represent a minor subpopulation of T-lymphocytes in man and their role in normal and diseased human skin is unknown. This article is a comprehensive review of T-lymphocytes bearing the gamma delta T-cell receptor in normal and pathological human skin. Firstly, we have documented the occurrence of gamma delta T-cells in normal skin and in a range of reactive and malignant skin conditions. We have then discussed the experimental findings regarding the repertoire used by gamma delta T-cells in normal human skin and in cutaneous disorders with an increased percentage of gamma delta T-cells. 相似文献
8.
9.
10.
Human immunodeficiency virus (HIV) infection of the thymus could have profound effects on development of the immune response, particularly in children. We and others have established that in addition to infecting and depleting CD4-bearing thymocytes, functional HIV proviruses are found in thymocytes lacking surface CD4 expression. Using in vitro thymocyte cultures, we show that neither HIV-mediated down regulation of CD4 nor CD4-independent infection contributes to the localization of HIV in cells lacking the primary virus receptor. Rather, infection of a CD4-positive precursor cell (CD4 positive/CD8 positive) with subsequent differentiation into a mature CD4-negative phenotype results in productively infected CD4-negative cells. This novel mechanism may contribute to pathogenesis by distributing viral sequences into functional subsets of T cells typically refractory to HIV infection and could account for the presence of viral DNA in CD8-positive lymphocytes recently observed in patients. 相似文献