首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   65475篇
  免费   5897篇
  国内免费   2695篇
电工技术   3595篇
技术理论   4篇
综合类   3655篇
化学工业   12168篇
金属工艺   3454篇
机械仪表   3959篇
建筑科学   4555篇
矿业工程   1766篇
能源动力   2176篇
轻工业   6145篇
水利工程   1265篇
石油天然气   2972篇
武器工业   553篇
无线电   7024篇
一般工业技术   8120篇
冶金工业   2974篇
原子能技术   841篇
自动化技术   8841篇
  2024年   304篇
  2023年   1192篇
  2022年   2335篇
  2021年   3112篇
  2020年   2245篇
  2019年   2057篇
  2018年   2307篇
  2017年   2369篇
  2016年   2300篇
  2015年   2713篇
  2014年   3444篇
  2013年   4291篇
  2012年   4606篇
  2011年   4817篇
  2010年   4112篇
  2009年   3989篇
  2008年   3694篇
  2007年   3408篇
  2006年   3170篇
  2005年   2643篇
  2004年   2023篇
  2003年   1805篇
  2002年   1867篇
  2001年   1617篇
  2000年   1307篇
  1999年   1271篇
  1998年   897篇
  1997年   716篇
  1996年   666篇
  1995年   574篇
  1994年   414篇
  1993年   361篇
  1992年   292篇
  1991年   198篇
  1990年   163篇
  1989年   129篇
  1988年   135篇
  1987年   74篇
  1986年   81篇
  1985年   62篇
  1984年   46篇
  1983年   38篇
  1982年   30篇
  1981年   24篇
  1980年   29篇
  1979年   22篇
  1978年   16篇
  1977年   18篇
  1976年   23篇
  1974年   10篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
The equilibrium Ca3P2(s) = 3[Ca] + 2[P] was studied at 1600 ° by equilibrating liquid iron, saturated with Ca3P2, and contained in a TiN crucible, with Ca vapor. The source of Ca was liquid Ca contained in an Mo crucible, and the vapor pressure of Ca was varied by varying the position of the Mo crucible in the temperature gradient of a vertical tube furnace. A least-squares analysis of the data gave and. The simultaneous equilibria CaO(s) = [Ca] + [O] and CaS(s) = [Ca] + [S] were studied at 1600 ° by equilibrating liquid iron, contained in a pressed and sintered CaO-CaS crucible with Ca vapor. The advantage of this technique is that two equilibrium constants,K cas andK cao, and two interaction coefficients, and can be determined from one set of experiments. It was determined that, at 1600 °,K cas = 5.9 × 10−8 K cao = 5.5 × 10−9,, and. Formerly Graduate Students  相似文献   
33.
朱东 《电焊机》1991,(3):19-23
本文分析提出焊接设备中影响计算机控制系统的几种主要干扰。结合实际工作,提出了解决的措施和方法。  相似文献   
34.
35.
Dong  Yibiao  Han  Ru  Wang  Danghui  Wang  Ruofei  Guo  Chenmeng 《SILICON》2021,13(9):3101-3111
Silicon - In this paper, an analytical model for negative capacitance double gate field effect transistor (NC-DG-FET) is proposed. This model includes interface traps and temperature effects, which...  相似文献   
36.
Immune checkpoint inhibitors (ICIs) have demonstrated remarkable efficacy in a growing number of malignancies. However, overcoming primary or secondary resistances is difficult due to pharmacokinetics issues and side effects associated with high systemic exposure. Local or regional expression of monoclonal antibodies (mAbs) using gene therapy vectors can alleviate this problem. In this work, we describe a high-capacity adenoviral vector (HCA-EFZP-aPDL1) equipped with a mifepristone-inducible system for the controlled expression of an anti-programmed death ligand 1 (PD-L1) blocking antibody. The vector was tested in an immune-competent mouse model of colorectal cancer based on implantation of MC38 cells. A single local administration of HCA-EFZP-aPDL1 in subcutaneous lesions led to a significant reduction in tumor growth with minimal release of the antibody in the circulation. When the vector was tested in a more stringent setting (rapidly progressing peritoneal carcinomatosis), the antitumor effect was marginal even in combination with other immune-stimulatory agents such as polyinosinic-polycytidylic acid (pI:C), blocking mAbs for T cell immunoglobulin, mucin-domain containing-3 (TIM-3) or agonistic mAbs for 4-1BB (CD137). In contrast, macrophage depletion by clodronate liposomes enhanced the efficacy of HCA-EFZP-aPDL1. These results highlight the importance of addressing macrophage-associated immunoregulatory mechanisms to overcome resistance to ICIs in the context of colorectal cancer.  相似文献   
37.
The magnesium (Mg) alloy low-pressure expendable pattern casting (EPC) process is a newly developed casting technique combining the advantages of both EPC and low-pressure casting. In this article, metal filling and the effect of the flow quantity of inert gas on the filling rate in the low-pressure EPC process are investigated. The results showed that the molten Mg alloy filled the mold cavity with a convex front laminar flow and the metal-filling rate increased significantly with increasing flow quantity when flow quantity was below a critical value. However, once the flow quantity exceeded a critical value, the filling rate increased slightly. The influence of the flow quantity of inert gas on melt-filling rate reveals that the mold fill is controlled by flow quantity for a lower filling rate, and, subsequently, controlled by the evaporation of polystyrene and the evaporation products for higher metal velocity. Meanwhile, the experimental results showed that the melt-filling rate significantly affected the flow profile, and the filling procedure for the Mg alloy in the low-pressure EPC process. A slower melt-filling rate could lead to misrun defects, whereas a higher filling rate results in folds, blisters, and porosity. The optimized filling rate with Mg alloy casting is 140 to 170 mm/s in low-pressure EPC.  相似文献   
38.
Yuda Yürüm  Ismail Yiginsu 《Fuel》1981,60(11):1027-1030
A lignite (C, 67.4 wt%) was depolymerized with phenol, p-nitrophenol and o-chlorophenol using sulphuric acid as catalyst. The solubility of the lignite was enhanced by these treatments, with phenol being the most reactive reagent whereas p-nitrophenol was the least reactive. The distribution of nitro- and chloro-groups in the solubilized products was investigated by infrared spectrometry and it was found that these groups were redistributed among the pyridine- and methanol-soluble materials. It is suggested that benzene-soluble material is produced by self-depolymerization of coal or by degradation of pyridine- and methanol-soluble material.  相似文献   
39.
Electron Emission from Barium Strontium Titanate Ceramics   总被引:1,自引:0,他引:1  
This paper focuses on understanding the influence of materials' properties on the ferroelectric electron emission. Ferroelectric ( x =1.0 and 0.8) and paraelectric ( x =0.67 and 0.5) compositions of barium strontium titanate (Ba x Sr(1− x )TiO3) system were chosen for study based on their different ferroelectric and dielectric properties. Similar emission current waveforms were obtained from four compositions with negative triggering voltage applied to the rear electrode of the samples. It was difficult to explain the experimental results using the spontaneous polarization-switching model. The mechanism of electron emission from Ba x Sr(1− x )TiO3 ceramics was ascertained to surface plasma emission.  相似文献   
40.
马冬 《中国氯碱》2003,(5):25-26
讨论了常见扩链剂的功能及在聚氯乙烯树脂生产中的应用。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号