全文获取类型
收费全文 | 28567篇 |
免费 | 1500篇 |
国内免费 | 660篇 |
专业分类
电工技术 | 1712篇 |
综合类 | 2980篇 |
化学工业 | 8058篇 |
金属工艺 | 1244篇 |
机械仪表 | 1814篇 |
建筑科学 | 1281篇 |
矿业工程 | 1114篇 |
能源动力 | 627篇 |
轻工业 | 1538篇 |
水利工程 | 332篇 |
石油天然气 | 2890篇 |
武器工业 | 163篇 |
无线电 | 1648篇 |
一般工业技术 | 1215篇 |
冶金工业 | 1745篇 |
原子能技术 | 244篇 |
自动化技术 | 2122篇 |
出版年
2024年 | 35篇 |
2023年 | 135篇 |
2022年 | 361篇 |
2021年 | 465篇 |
2020年 | 380篇 |
2019年 | 263篇 |
2018年 | 409篇 |
2017年 | 533篇 |
2016年 | 509篇 |
2015年 | 498篇 |
2014年 | 1701篇 |
2013年 | 1340篇 |
2012年 | 2008篇 |
2011年 | 1351篇 |
2010年 | 1289篇 |
2009年 | 1594篇 |
2008年 | 1654篇 |
2007年 | 2631篇 |
2006年 | 2884篇 |
2005年 | 2115篇 |
2004年 | 1136篇 |
2003年 | 1383篇 |
2002年 | 993篇 |
2001年 | 846篇 |
2000年 | 822篇 |
1999年 | 725篇 |
1998年 | 527篇 |
1997年 | 390篇 |
1996年 | 318篇 |
1995年 | 266篇 |
1994年 | 209篇 |
1993年 | 164篇 |
1992年 | 128篇 |
1991年 | 105篇 |
1990年 | 72篇 |
1989年 | 56篇 |
1988年 | 59篇 |
1987年 | 52篇 |
1986年 | 41篇 |
1985年 | 65篇 |
1984年 | 47篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 18篇 |
1980年 | 28篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
秦华 《计算机与数字工程》2012,40(3):136-139
基于IEC61131-3标准设计一个可编程逻辑控制器(PLC)编辑模块,并给出了主要数据结构和算法的设计。通过测试表明用户界面友好,操作简单,对后续开发具指导意义。 相似文献
82.
The behavioral and electrophysiological activity of a mimic [(Z,E)7,9,11-dodecatrienyl formate] of the major sex pheromone component [(Z,E) 9,11,13-tetradecatrienal] of carob moth was assessed. Wind-tunnel bioassays demonstrated that the formate was as effective as natural gland extracts, and significantly more effective than the trienal alone or than the trienal blended with two minor pheromone components, in evoking source contact. Dispensers containing the formate were as effective as trienal-containing blend lures in attracting males when placed at the same dosage in traps in date gardens. Single-cell recordings showed that at least two olfactory neurons, differentiated by spike amplitude, are located in the long trichoid hairs on male carob moth antennae. Dose-response relationships indicated that puffs from cartridges loaded with at least 0.1 g of the formate or of the trienal were necessary to elicit spiking by either the small or the large-spiking cell within a sensillum. Cross-adaptation studies demonstrated that both compounds stimulated the same large-spiking cell. The frequencies of spikes evoked from the large cell when stimulated by emissions from 0.1-g, 1-g, or 10-g cartridges of either the formate or the trienal were not significantly different, suggesting that the formate is an effective mimic of the trienal at the antennal receptor cell level. 相似文献
83.
FTIR spectroscopy was applied to study the initial steps of ethylene polymerization on reduced chromia-silica (0.5 wt% Cr/SiO2). To decrease the speed of the reaction small doses of gas were introduced to the catalyst in each run and C2D4 was used to confirm band assignments. At the initial steps of the reaction only ethylene molecules coordinated to probably Cr
A
2+
cations were observed. The concentration of such complexes was estimated to be about 50% of the total amount of Cr atoms in the sample. The FTIR spectrum of the polymer formed at the initial doses of C2H4 (when [C2H4] [Cr]) was found to be slightly different from that formed after excess ethylene was introduced onto the catalyst ([C2H4] > [Cr]). 相似文献
84.
85.
水平连铸带坯QSn6.5-0.1的组织与性能 总被引:7,自引:2,他引:7
讨论了锡磷青铜QSn6.5-0.1水平连铸带坯的宏观组织特点、反偏析行为和显微缩孔。结果表明:横断面以柱状晶为主,结晶中心线普遍上移,大面出现结晶角,上下表面和侧边出现反偏析,紧临偏析区出现低Sn区,显微缩松是主要组织缺陷.是冷加工报废的主要原因,同时通过热处理试验,分析了热处理规范对锭坯性能及组织的影响,并制订出合理的热处理规范。 相似文献
86.
提出一种AutoCAD环境中基于标淮件库的螺钉联接自适应设计算法。利用螺钉和垫片以及被联接件之间设计信息的相关性自动确定装配方位及联接件的几何参数,自动检测和复原被联接件的剖面线,简化了设计过程。 相似文献
87.
Renata Gruszka Krzysztof Zakrzewski Pawe Piotr Liberski Magdalena Zakrzewska 《International journal of molecular sciences》2021,22(2)
Numerous molecular factors disrupt the correctness of the cell cycle process leading to the development of cancer due to increased cell proliferation. Among known causative factors of such process is abnormal gene expression. Nowadays in the light of current knowledge such alterations are frequently considered in the context of mRNA–miRNA correlation. One of the molecular factors with potential value in tumorigenesis is the feedback loop between MYC and E2F genes in which miR-17-5p and miR-20a from the miR-17-92 cluster are involved. The current literature shows that overexpression of the members of the OncomiR-1 are involved in the development of many solid tumors. In the present work, we investigated the expression of components of the MYC/E2F/miR-17-92 network and their closely related elements including members of MYC and E2F families and miRNAs from two paralogs of miR-17-92: miR-106b-25 and miR-106a-363, in the most common brain tumors of childhood, pilocytic astrocytoma (PA), WHO grade 1; ependymoma (EP), WHO grade 2; and medulloblastoma (MB), WHO grade 4. We showed that the highest gene expression was observed in the MYC family for MYCN and in the E2F family for E2F2. Positive correlation was observed between the gene expression and tumor grade and type, with the highest expression being noted for medulloblastomas, followed by ependymomas, and the lowest for pilocytic astrocytomas. Most members of miR-17-92, miR-106a-363 and miR-106b-25 clusters were upregulated and the highest expression was noted for miR-18a and miR-18b. The rest of the miRNAs, including miR-19a, miR-92a, miR-106a, miR-93, or miR-25 also showed high values. miR-17-5p, miR-20a obtained a high level of expression in medulloblastomas and ependymomas, while close to the control in the pilocytic astrocytoma samples. miRNA expression also depended on tumor grade and histology. 相似文献
88.
三维空间孔道的精确校核 总被引:1,自引:0,他引:1
二维空间孔道的传统校核方法是把三维问题化成二维问题,再简化或近似处理,这样的方法在高精度场合往往不能满足设计要求;还有的是对孔表面网格化、布尔运算等,算法复杂,难于实现。本文从计算几何理论上探讨了三维空间孔的精确校核方法,简单、易行、可靠。 相似文献
89.
超临界CO2对钢材的腐蚀实验研究 总被引:3,自引:0,他引:3
采用静态高温高压釜及SEM现代分析测试手段,在分析超临界CO2存在形式及与原油、水交互作用的基础上,进行了超临界CO2对钢材的腐蚀实验研究。结果表明,在腐蚀系统SCF-CO2气相中,存在CO2腐蚀现象;液相中,腐蚀速率随压力增加而上升,12MPa达到峰值后下降。在纯水中12MPa时,液相和气相中的腐蚀速率趋于一致,腐蚀形貌表现为腐蚀瘤。30%的原油含量可在液相促进钢材腐蚀。腐蚀形貌表现为腐蚀瘤与腐蚀坑并存;但随含油量增加,会抑制钢材腐蚀。 相似文献
90.
变频器干扰产生的原因及防范措施 总被引:1,自引:0,他引:1
介绍了电动设备中使用的变频器产生干扰的原因、传播途径,及相应的抗干扰措施,提出了在变频器系统设计和安装过程中应注意的问题。 相似文献