全文获取类型
收费全文 | 23950篇 |
免费 | 1238篇 |
国内免费 | 579篇 |
专业分类
电工技术 | 556篇 |
综合类 | 460篇 |
化学工业 | 4129篇 |
金属工艺 | 1056篇 |
机械仪表 | 735篇 |
建筑科学 | 1303篇 |
矿业工程 | 247篇 |
能源动力 | 680篇 |
轻工业 | 1992篇 |
水利工程 | 278篇 |
石油天然气 | 171篇 |
武器工业 | 59篇 |
无线电 | 1890篇 |
一般工业技术 | 3783篇 |
冶金工业 | 4776篇 |
原子能技术 | 214篇 |
自动化技术 | 3438篇 |
出版年
2023年 | 184篇 |
2022年 | 334篇 |
2021年 | 558篇 |
2020年 | 390篇 |
2019年 | 405篇 |
2018年 | 494篇 |
2017年 | 510篇 |
2016年 | 537篇 |
2015年 | 502篇 |
2014年 | 735篇 |
2013年 | 1479篇 |
2012年 | 1146篇 |
2011年 | 1472篇 |
2010年 | 1115篇 |
2009年 | 1157篇 |
2008年 | 1229篇 |
2007年 | 1189篇 |
2006年 | 1040篇 |
2005年 | 952篇 |
2004年 | 736篇 |
2003年 | 663篇 |
2002年 | 630篇 |
2001年 | 420篇 |
2000年 | 384篇 |
1999年 | 395篇 |
1998年 | 784篇 |
1997年 | 546篇 |
1996年 | 464篇 |
1995年 | 384篇 |
1994年 | 360篇 |
1993年 | 351篇 |
1992年 | 282篇 |
1991年 | 189篇 |
1990年 | 260篇 |
1989年 | 221篇 |
1988年 | 181篇 |
1987年 | 180篇 |
1986年 | 167篇 |
1985年 | 195篇 |
1984年 | 199篇 |
1983年 | 166篇 |
1982年 | 175篇 |
1981年 | 174篇 |
1980年 | 155篇 |
1979年 | 165篇 |
1978年 | 124篇 |
1977年 | 144篇 |
1976年 | 237篇 |
1975年 | 128篇 |
1973年 | 109篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
2.
Yixuan ZHOU Huajie WANG Yi YU Yihang CHEN Rui KE Min XU Chijie XIAO Zhanhui WANG Jiquan LI Xuru DUAN Minyou YE 《等离子体科学和技术》2021,23(7):75105-52
In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel. 相似文献
3.
Number entry is a ubiquitous activity and is often performed in safety- and mission-critical procedures, such as healthcare, science, finance, aviation and in many other areas. We show that Monte Carlo methods can quickly and easily compare the reliability of different number entry systems. A surprising finding is that many common, widely used systems are defective, and induce unnecessary human error. We show that Monte Carlo methods enable designers to explore the implications of normal and unexpected operator behaviour, and to design systems to be more resilient to use error. We demonstrate novel designs with improved resilience, implying that the common problems identified and the errors they induce are avoidable. 相似文献
4.
5.
Sarah Gilgunn Keefe Murphy Henning Stckmann Paul J. Conroy T. Brendan Murphy R. William Watson Richard J. OKennedy Pauline M. Rudd Radka Saldova 《International journal of molecular sciences》2020,21(23)
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies. 相似文献
6.
7.
Choi Paul Santos Christian Ariane Kim Min-Kun Jung Hyunsook Hong Do-Young Koo Junemo 《Journal of Mechanical Science and Technology》2021,35(11):5007-5022
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations... 相似文献
8.
Dr. Raysa Khan Tareque Dr. Storm Hassell-Hart Dr. Tobias Krojer Dr. Anthony Bradley Dr. Srikannathasan Velupillai Dr. Romain Talon Dr. Michael Fairhead Dr. Iain J. Day Kamlesh Bala Dr. Robert Felix Dr. Paul D. Kemmitt Prof. Paul Brennan Prof. Frank von Delft Dr. Laura Díaz Sáez Prof. Kilian Huber Prof. John Spencer 《ChemMedChem》2020,15(24):2513-2520
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified. 相似文献
9.
陕南山地烟田不同植烟年限土壤养分的变化 总被引:1,自引:0,他引:1
为给陕南山地烟草生产布局及有针对性的施肥措施提供依据,分析了陕南山地烟田不同植烟年限(0~15年)与土壤养分含量的关系。结果表明:随着植烟年限延长,有机质线性下降,全氮和速效钾显著上升,有效磷先上升后下降;氯、有效铁、有效锰、有效硼和有效铜无显著变化或变化很小,有效锌则在第1年急剧下降,之后保持稳定,10年后再次显著下降。认为陕南山地烟区烟叶生产中应适当增加有机肥的施用而合理控制氮肥、磷肥和钾肥的施用,并要注意锌肥的补充。 相似文献
10.
Paul Geoerg Florian Berchtold Steven Gwynne Karen Boyce Stefan Holl Anja Hofmann 《火与材料》2019,43(7):759-781
To quantify the evacuation process, evacuation practitioners use engineering egress data describing the occupant movement characteristics. These data are typically based to young and fit populations. However, the movement abilities of occupants who might be involved in evacuations are becoming more variable—with the building populations of today typically including increasing numbers of individuals: with impairments or who are otherwise elderly or generally less mobile. Thus, there will be an increasing proportion of building occupants with reduced ability to egress. For safe evacuation, there is therefore a need to provide valid engineering egress data considering pedestrians with disabilities. Gwynne and Boyce recently compiled a series of data sets related to the evacuation process to support practitioner activities in the chapter Engineering Data in the SFPE Handbook of Fire Protection Engineering. This paper supplements these data sets by providing information on and presenting data obtained from additional research related to the premovement and horizontal movement of participants with physical‐, cognitive‐, or age‐related disabilities. The aim is to provide an overview of currently available data sets related to, and key factors affecting the egress performance of, mixed ability populations which could be used to guide fire safety engineering decisions in the context of building design. 相似文献