全文获取类型
收费全文 | 20923篇 |
免费 | 889篇 |
国内免费 | 311篇 |
专业分类
电工技术 | 462篇 |
综合类 | 543篇 |
化学工业 | 3620篇 |
金属工艺 | 515篇 |
机械仪表 | 727篇 |
建筑科学 | 846篇 |
矿业工程 | 178篇 |
能源动力 | 558篇 |
轻工业 | 2065篇 |
水利工程 | 242篇 |
石油天然气 | 176篇 |
武器工业 | 27篇 |
无线电 | 2362篇 |
一般工业技术 | 2773篇 |
冶金工业 | 4062篇 |
原子能技术 | 168篇 |
自动化技术 | 2799篇 |
出版年
2023年 | 91篇 |
2022年 | 259篇 |
2021年 | 460篇 |
2020年 | 262篇 |
2019年 | 328篇 |
2018年 | 377篇 |
2017年 | 356篇 |
2016年 | 395篇 |
2015年 | 347篇 |
2014年 | 521篇 |
2013年 | 1010篇 |
2012年 | 785篇 |
2011年 | 964篇 |
2010年 | 740篇 |
2009年 | 806篇 |
2008年 | 792篇 |
2007年 | 814篇 |
2006年 | 703篇 |
2005年 | 602篇 |
2004年 | 679篇 |
2003年 | 896篇 |
2002年 | 1185篇 |
2001年 | 1013篇 |
2000年 | 588篇 |
1999年 | 539篇 |
1998年 | 1446篇 |
1997年 | 919篇 |
1996年 | 678篇 |
1995年 | 456篇 |
1994年 | 335篇 |
1993年 | 375篇 |
1992年 | 194篇 |
1991年 | 153篇 |
1990年 | 146篇 |
1989年 | 135篇 |
1988年 | 132篇 |
1987年 | 112篇 |
1986年 | 116篇 |
1985年 | 155篇 |
1984年 | 85篇 |
1983年 | 90篇 |
1982年 | 87篇 |
1981年 | 106篇 |
1980年 | 103篇 |
1979年 | 61篇 |
1978年 | 50篇 |
1977年 | 120篇 |
1976年 | 223篇 |
1975年 | 51篇 |
1973年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
952.
De Vos Lotte Bellemans Inge Vercruyssen Carina Verbeken Kim 《Metallurgical and Materials Transactions B》2019,50(6):2647-2666
Metallurgical and Materials Transactions B - Modeling of the basic oxygen furnace (BOF) process, both for online monitoring and fundamental research, has gained importance in steelmaking industry... 相似文献
953.
强化石油企业财务管理的对策探讨 总被引:9,自引:0,他引:9
议论石油企业经济管理上存在的不足,对加强管理的措施提出了建设性建议. 相似文献
954.
Biagio Barone Luigi Napolitano Marco Abate Luigi Cirillo Pasquale Reccia Francesco Passaro Carmine Turco Simone Morra Francesco Mastrangelo Antonio Scarpato Ugo Amicuzi Vincenzo Morgera Lorenzo Romano Francesco Paolo Calace Savio Domenico Pandolfo Luigi De Luca Achille Aveta Enrico Sicignano Massimiliano Trivellato Gianluca Spena Carlo DAlterio Giovanni Maria Fusco Raffaele Vitale Davide Arcaniolo Felice Crocetto 《International journal of molecular sciences》2022,23(7)
Testosterone is the most important hormone in male health. Aging is characterized by testosterone deficiency due to decreasing testosterone levels associated with low testicular production, genetic factors, adiposity, and illness. Low testosterone levels in men are associated with sexual dysfunction (low sexual desire, erectile dysfunction), reduced skeletal muscle mass and strength, decreased bone mineral density, increased cardiovascular risk and alterations of the glycometabolic profile. Testosterone replacement therapy (TRT) shows several therapeutic effects while maintaining a good safety profile in hypogonadal men. TRT restores normal levels of serum testosterone in men, increasing libido and energy level and producing beneficial effects on bone density, strength and muscle as well as yielding cardioprotective effects. Nevertheless, TRT could be contraindicated in men with untreated prostate cancer, although poor findings are reported in the literature. In addition, different potential side effects, such as polycythemia, cardiac events and obstructive sleep apnea, should be monitored. The aim of our review is to provide an updated background regarding the pros and cons of TRT, evaluating its role and its clinical applicability in different domains. 相似文献
955.
Paola Maura Tricarico Donatella Mentino Aurora De Marco Cecilia Del Vecchio Sabino Garra Gerardo Cazzato Caterina Foti Sergio Crovella Giuseppe Calamita 《International journal of molecular sciences》2022,23(7)
The skin is the largest organ of the human body, serving as an effective mechanical barrier between the internal milieu and the external environment. The skin is widely considered the first-line defence of the body, with an essential function in rejecting pathogens and preventing mechanical, chemical, and physical damages. Keratinocytes are the predominant cells of the outer skin layer, the epidermis, which acts as a mechanical and water-permeability barrier. The epidermis is a permanently renewed tissue where undifferentiated keratinocytes located at the basal layer proliferate and migrate to the overlying layers. During this migration process, keratinocytes undertake a differentiation program known as keratinization process. Dysregulation of this differentiation process can result in a series of skin disorders. In this context, aquaporins (AQPs), a family of membrane channel proteins allowing the movement of water and small neutral solutes, are emerging as important players in skin physiology and skin diseases. Here, we review the role of AQPs in skin keratinization, hydration, keratinocytes proliferation, water retention, barrier repair, wound healing, and immune response activation. We also discuss the dysregulated involvement of AQPs in some common inflammatory dermatological diseases characterised by skin barrier disruption. 相似文献
956.
Shuo Li Jianlin Cao Xiang Feng Yupeng Du De Chen Chaohe Yang Wenhua Wang Wanzhong Ren 《中国化学工程学报》2022,47(7):174-184
Elucidating the confinement effect harbours tremendous significance for isobutane alkylation with C4 olefin. Herein, the confinement effect over zeolite catalysts was elucidated by combining DFT calculations, experiments(using the novel Beta zeolite exposing only external surfaces(Beta-E) and conventional Beta-I zeolite with both external and internal surfaces) and multi-techniques(e.g., TGA-DTG,HRTEM, SEM and XRD). It is found that the main active sites for C4 alkylation r... 相似文献
957.
Valdezate S Arroyo M González-Sanz R Ramíro R Herrera-León S Usera MA De la Fuente M Echeita A 《Journal of food protection》2007,70(12):2741-2748
The aims of this study were to ascertain the population structure and antimicrobial susceptibility of Salmonella enterica serovars isolated in 2002 from food in 16 Spanish regions. Serovars were characterized by serotyping, phage typing, antimicrobial susceptibility, and pulsed-field gel electrophoresis (PFGE) typing, and 264 nonrelated strains were selected for further analysis. The main sources were eggs and their derivatives (21.6% of strains), poultry and related products (16.6%), and seafood (16.3%). High serotype diversity was detected (51 serotypes); the most common were Enteritidis (n = 96, 36.3%) and Typhimurium (n = 53, 20.1%), followed by a miscellaneous group of 49 different serotypes (n = 115, 43.5%). A 15% increase in Salmonella Enteritidis isolation was observed. Common phage types for Salmonella Enteritidis were PT1 (41.6% of isolates), PT4 (9.4%), PT6 (9.4%), and PT6a (9.4%), and common types for Salmonella Typhimurium were DTU302 (18.8%), DT104 (15.1%), and DT104B (13.2%). Salmonella Enteritidis strains were categorized into eight PFGE types with a similarity of 81 to 96%, and 73.9% of the strains were grouped into just one cluster. Salmonella Typhimurium isolates were divided into 13 PFGE types with a similarity of 64 to 86%, and one predominant clone contained 41.5% of the strains. Resistance rates for Salmonella Enteritidis, Salmonella Typhimurium, and the miscellaneous group were, respectively, 8.3, 69.8, and 13.9% for ampicillin, 3.1, 52.8, and 59% for streptomycin, 40.6, 22.6, and 10.4% for nalidixic acid, 15.6, 71.7, and 31.1% for tetracycline, 7.3, 18.8, and 9.5% for trimethoprim-sulfamethoxazole, 0, 50.9, and 4.3% for chloramphenicol, and 6.2, 71.7, and 17.4% for multiple (at least four) antimicrobials. All the strains remained susceptible to other beta-lactams and fluoroquinolones. Surveillance of S. enterica isolated from food is strongly recommended to reduce community exposure to antimicrobial resistant strains. 相似文献
958.
包装机械CAI课件设计 总被引:1,自引:0,他引:1
本文结合包装机械学课程的特点,对其CAI课件进行了研究和开发。课件系统包括三个主要部分:包装机械学计算机辅助学习系统,主要内容包括包装机械学的基本概念、方法、理论、例题、练习题;包装机械的仿真与模拟系统,基本内容包括典型整机的图片、基本构件工作原理的仿真与模拟;包装机械学综合测评系统,内容有检测题、试卷、试卷答卷。 相似文献
959.
José Diana Di Mavungu Svetlana V. Malysheva Melanie Sanders Daria Larionova Johan Robbens Peter Dubruel Carlos Van Peteghem Sarah De Saeger 《Food chemistry》2012
A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of six major ergot alkaloids, ergometrine, ergosine, ergotamine, ergocornine, ergokryptine and ergocristine, as well as their corresponding epimers in food and feed samples. The method involves extraction under alkaline conditions and subsequent clean-up by applying a simple and rapid liquid–liquid partitioning procedure prior to LC–MS/MS analysis. Evaluation of the method revealed good linearity, accuracy and precision. The limits of quantification varied from 0.1 to 1 μg/kg depending on the analyte and matrix. The average extraction and clean-up recoveries in different matrices were between 45 (only for ergometrine in biscuit) and 90%. The uncertainty associated with the analytical method was not higher than 51% and 30%, at concentration levels of 2.5 and 150 μg/kg respectively. Analyte epimerization proved to be minimal during the analytical procedure. The method has been successfully applied to the determination of ergot alkaloids in some Belgian food and feed commodities. Ergot alkaloids were found in 104 out of 122 samples investigated. Ergosine was the most frequently occurring alkaloid, while the highest levels were observed for ergotamine, ergocristine or ergosine, depending on the product type. The total alkaloid content in positive samples varied from 1 to 1145 μg/kg. 相似文献
960.
Effect of sourdough fermentation on stabilisation,and chemical and nutritional characteristics of wheat germ 总被引:4,自引:0,他引:4
Carlo Giuseppe Rizzello Luana NionelliRossana Coda Maria De AngelisMarco Gobbetti 《Food chemistry》2010
Lactic acid bacteria strains were identified from wheat germ by 16S rRNA partial sequencing, subjected to RAPD-PCR typing and screened. Lactobacillus plantarum LB1 and Lactobacillus rossiae LB5 were used as starters to produce sourdough fermented wheat germ (SFWG). The chemical and nutritional characteristics of SFWG were compared to those of the raw wheat germ (RWG). Lipase activity in SFWG was ca. 2.6-fold lower than that found in RWG. As shown by SPME/GC/MS analysis, most of the volatile compounds derived from lipid oxidation during storage (40 days) were at markedly lower levels in SFWG compared to RWG. Fermentation of wheat germ increased of ca. 50% the concentration of free amino acids. Glu markedly decreased in SFWG, due to its conversion in GABA. The concentration of the anti-nutritional factor raffinose also decreased in SFWG. The in vitro protein digestibility, the concentration of total phenols, phytase and antioxidant activities were increased by fermentation. 相似文献