全文获取类型
收费全文 | 7479篇 |
免费 | 208篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 99篇 |
综合类 | 10篇 |
化学工业 | 1184篇 |
金属工艺 | 195篇 |
机械仪表 | 220篇 |
建筑科学 | 256篇 |
矿业工程 | 16篇 |
能源动力 | 254篇 |
轻工业 | 431篇 |
水利工程 | 34篇 |
石油天然气 | 24篇 |
无线电 | 1094篇 |
一般工业技术 | 1295篇 |
冶金工业 | 1196篇 |
原子能技术 | 48篇 |
自动化技术 | 1346篇 |
出版年
2023年 | 36篇 |
2021年 | 103篇 |
2020年 | 60篇 |
2019年 | 88篇 |
2018年 | 110篇 |
2017年 | 112篇 |
2016年 | 133篇 |
2015年 | 135篇 |
2014年 | 192篇 |
2013年 | 578篇 |
2012年 | 333篇 |
2011年 | 460篇 |
2010年 | 363篇 |
2009年 | 418篇 |
2008年 | 417篇 |
2007年 | 338篇 |
2006年 | 291篇 |
2005年 | 249篇 |
2004年 | 227篇 |
2003年 | 208篇 |
2002年 | 185篇 |
2001年 | 148篇 |
2000年 | 112篇 |
1999年 | 140篇 |
1998年 | 272篇 |
1997年 | 175篇 |
1996年 | 164篇 |
1995年 | 127篇 |
1994年 | 152篇 |
1993年 | 122篇 |
1992年 | 108篇 |
1991年 | 69篇 |
1990年 | 78篇 |
1989年 | 73篇 |
1988年 | 72篇 |
1987年 | 49篇 |
1986年 | 51篇 |
1985年 | 48篇 |
1984年 | 59篇 |
1983年 | 51篇 |
1982年 | 57篇 |
1981年 | 32篇 |
1980年 | 39篇 |
1979年 | 46篇 |
1978年 | 44篇 |
1977年 | 41篇 |
1976年 | 42篇 |
1975年 | 32篇 |
1974年 | 37篇 |
1973年 | 36篇 |
排序方式: 共有7702条查询结果,搜索用时 15 毫秒
1.
Knowledge and Information Systems - Many data mining algorithms cannot handle incomplete datasets where some data samples are missing attribute values. To solve this problem, missing value... 相似文献
2.
The flame retardant polypropylene containing the micro-envelope core-shell structure flame retardant, which encapsulated ammonium polyphosphate into melamine-formaldehyde resin and sodium silicate through in situ polymerization was prepared with polyamide 6, added as a carbon-forming agent. The composition of ammonium polyphosphate, encapsulated ammonium polyphosphate with melamine-formaldehyde resin and the micro-envelope core-shell structure flame retardant were characterized. The fire safety and thermal stability were investigated and showed an improvement including limiting oxygen index, thermogravimetric analysis, vertical burning tests, and microscale combustion calorimeter. The burned compounds were also studied to confirm the burning mechanism. The results showed the flame retardant performance had been greatly improved, while polyamide 6 had better char-forming effect. Besides, the water solubility of flame retardants and their influence on the mechanical properties of polypropylene were also investigated. The results on the effects of additives demonstrated a high efficiency flame retardant to polypropylene. A core-shell flame retardant that sodium silicate and melamine-formaldehyde resin-coated ammonium polyphosphate had been constructed. The effect of the built flame retardant system on the combustion performance of polypropylene was studied from the mechanism and performance. The LOI of the most flame retardant polypropylene reached 28.6%, and UL-94 reached the V-0 level. 相似文献
3.
4.
Alison Jee Samantha Christine Sernoskie Jack Uetrecht 《International journal of molecular sciences》2021,22(6)
Idiosyncratic drug-induced liver injury (IDILI) remains a significant problem for patients and drug development. The idiosyncratic nature of IDILI makes mechanistic studies difficult, and little is known of its pathogenesis for certain. Circumstantial evidence suggests that most, but not all, IDILI is caused by reactive metabolites of drugs that are bioactivated by cytochromes P450 and other enzymes in the liver. Additionally, there is overwhelming evidence that most IDILI is mediated by the adaptive immune system; one example being the association of IDILI caused by specific drugs with specific human leukocyte antigen (HLA) haplotypes, and this may in part explain the idiosyncratic nature of these reactions. The T cell receptor repertoire likely also contributes to the idiosyncratic nature. Although most of the liver injury is likely mediated by the adaptive immune system, specifically cytotoxic CD8+ T cells, adaptive immune activation first requires an innate immune response to activate antigen presenting cells and produce cytokines required for T cell proliferation. This innate response is likely caused by either a reactive metabolite or some form of cell stress that is clinically silent but not idiosyncratic. If this is true it would make it possible to study the early steps in the immune response that in some patients can lead to IDILI. Other hypotheses have been proposed, such as mitochondrial injury, inhibition of the bile salt export pump, unfolded protein response, and oxidative stress although, in most cases, it is likely that they are also involved in the initiation of an immune response rather than representing a completely separate mechanism. Using the clinical manifestations of liver injury from a number of examples of IDILI-associated drugs, this review aims to summarize and illustrate these mechanistic hypotheses. 相似文献
5.
Andrew Artzer Michael Moats Jack Bender 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(12):2856-2863
Antimony and bismuth recovery from copper electrorefining electrolyte could reduce the impacts of these problem elements and produce a new primary source for them. Two proprietary phosphonic acid ester extractants were examined (REX-1 and REX-2) for the removal of antimony and bismuth from copper electrorefining electrolytes. Experimentation included shakeout and break tests to determine the basic parameters for the extractants in terms of maximum loading, break times, and extraction and stripping efficiency. Five permutations of extractant mixtures (100 wt.% REX-1 and 25 wt.%, 50 wt.%, 75 wt.% and 100 wt.% REX-2) were studied. It was determined that REX-2 was able to extract Sb and Bi from the electrolyte, but required some mixture with REX-1 to better facilitate stripping with 400 g/L sulfuric acid. The laboratory electrorefining electrolyte containing glue had faster disengagement times than a synthetic solution without glue. 相似文献
6.
Solution‐Processed High‐Performance Tetrathienothiophene‐Based Small Molecular Blends for Ambipolar Charge Transport 下载免费PDF全文
Sureshraju Vegiraju Chih‐Yu Lin Pragya Priyanka Deng‐Yi Huang Xian‐Lun Luo Hsiang‐Chi Tsai Shao‐Huan Hong Chia‐Jung Yeh Wei‐Chieh Lien Chien‐Lung Wang Shih‐Huang Tung Cheng‐Liang Liu Ming‐Chou Chen Antonio Facchetti 《Advanced functional materials》2018,28(28)
Four soluble dialkylated tetrathienoacene ( TTAR) ‐based small molecular semiconductors featuring the combination of a TTAR central core, π‐conjugated spacers comprising bithiophene ( bT ) or thiophene ( T ), and with/without cyanoacrylate ( CA ) end‐capping moieties are synthesized and characterized. The molecule DbT‐TTAR exhibits a promising hole mobility up to 0.36 cm2 V?1 s?1 due to the enhanced crystallinity of the microribbon‐like films. Binary blends of the p‐type DbT‐TTAR and the n‐type dicyanomethylene substituted dithienothiophene‐quinoid ( DTTQ‐11 ) are investigated in terms of film morphology, microstructure, and organic field‐effect transistor (OFET) performance. The data indicate that as the DbT‐TTAR content in the blend film increases, the charge transport characteristics vary from unipolar (electron‐only) to ambipolar and then back to unipolar (hole‐only). With a 1:1 weight ratio of DbT‐TTAR DTTQ‐11 in the blend, well‐defined pathways for both charge carriers are achieved and resulted in ambipolar transport with high hole and electron mobilities of 0.83 and 0.37 cm2 V?1 s?1, respectively. This study provides a viable way for tuning microstructure and charge carrier transport in small molecules and their blends to achieve high‐performance solution‐processable OFETs. 相似文献
7.
Telecommunication Systems - This paper investigates an iterative multiuser detection for nonbinary low density parity check (LDPC) coded multicarrier multiple level frequency shift keying system to... 相似文献
8.
Shao‐Pu Tsai Shih‐Ning Tsai Yu‐Ting Tsai Yu‐Wen Chen Po‐Yen Tung Jer‐Ren Yang Hsueh‐Ren Chen Chih‐Yuan Chen Yuan‐Tsung Wang Ching‐Yuan Huang 《Microscopy research and technique》2019,82(1):4-11
Convergent beam electron diffraction (CBED) in transmission electron microscopy (TEM) was applied to determine local carbon concentrations in low‐carbon transformation‐induced plasticity (TRIP) steels. High‐order Laue‐zone (HOLZ) lines were experimentally obtained for comparison with simulation results. A new procedure for calculating carbon content is thus proposed. Retained austenite (RA) is classified into three types by morphology; the relationship between the carbon content and the corresponding RA morphology is discussed based on CBED results. Furthermore, results of X‐Ray diffractometry measurements are also used for comparison. 相似文献
9.
10.
The Journal of Supercomputing - The challenge of a mobile ad-hoc network (MANET) or hybrid wireless network (HWN) is that every node must rely on others to forward its messages, but selfish nodes... 相似文献