全文获取类型
收费全文 | 35477篇 |
免费 | 3583篇 |
国内免费 | 2216篇 |
专业分类
电工技术 | 2841篇 |
技术理论 | 4篇 |
综合类 | 2779篇 |
化学工业 | 5063篇 |
金属工艺 | 2192篇 |
机械仪表 | 2226篇 |
建筑科学 | 3240篇 |
矿业工程 | 1022篇 |
能源动力 | 1118篇 |
轻工业 | 2313篇 |
水利工程 | 664篇 |
石油天然气 | 1739篇 |
武器工业 | 345篇 |
无线电 | 4261篇 |
一般工业技术 | 4207篇 |
冶金工业 | 1517篇 |
原子能技术 | 398篇 |
自动化技术 | 5347篇 |
出版年
2024年 | 186篇 |
2023年 | 704篇 |
2022年 | 1187篇 |
2021年 | 1822篇 |
2020年 | 1297篇 |
2019年 | 992篇 |
2018年 | 1097篇 |
2017年 | 1263篇 |
2016年 | 1093篇 |
2015年 | 1474篇 |
2014年 | 1788篇 |
2013年 | 2354篇 |
2012年 | 2462篇 |
2011年 | 2562篇 |
2010年 | 2335篇 |
2009年 | 2110篇 |
2008年 | 2135篇 |
2007年 | 2038篇 |
2006年 | 1926篇 |
2005年 | 1646篇 |
2004年 | 1174篇 |
2003年 | 1062篇 |
2002年 | 1192篇 |
2001年 | 1035篇 |
2000年 | 831篇 |
1999年 | 714篇 |
1998年 | 488篇 |
1997年 | 443篇 |
1996年 | 397篇 |
1995年 | 341篇 |
1994年 | 263篇 |
1993年 | 183篇 |
1992年 | 157篇 |
1991年 | 140篇 |
1990年 | 106篇 |
1989年 | 67篇 |
1988年 | 46篇 |
1987年 | 34篇 |
1986年 | 29篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1973年 | 4篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
To pick up serum high risk lithogenic factors predisposing one to gallstone formation and protective factors against gallstone formation in gallbladder. We compared serum lipid and apolipoprotein level of patients with gallbladder stone (stone group) with that of patients without gallbladder stone (control group). The correlation between serum lipid, apolipoprotein level and bile lipid level, cholesterol saturated index (CSI), characteristics of lipidemia in different kinds of gallbladder stones were studied. The results showed that the increase of serum Apo A1, C2 and E level in the stone group was more significant than in the control group. But there was no statistical significance in TC, TG, LDL-C, HDL-C, Apo A2, B, C3 level between the stone and control groups. These results suggested that serum apolipoproteins perhaps are more sensitive parameters than serum lipids in distinguishing patients with stones from those without stones. There were different profiles of serum lipid and apolipoproteins in different chemical types of gallbladder stones. Increased level in serum LDL-C, Apo B and ratio of LDL-C/HDL-C were characterized by an index for cholesterol stone, otherwise that in serum TG and Apo C2 an index for pigment stones. There was a positive correlation between serum total cholesterol (TC) or Apo B, C2, C3 and cholesterol amount or CSI in gallbladder bile. Therefore, TC, Apo B, C2, C3 could be considered as high risk lithogenic factors. A positive correlation existed between serum HDL-C and lecithin in gallbladder or common bile duct (CBD) bile as well as between HDL-C and bile acids in CBD bile. Thus, HDL-C might be a protective factor against gallstone formation in gallbladder. 相似文献
33.
本文深入讨论了脉冲啁啾的非线性起源及其对干涉相关测宽(等值宽度和条纹计数)法的影响。提出根据干涉相关曲线下包络最大值位置适当降低等值宽度位置和用计算机平均处理干涉相关信息的技术以消除啁啾的影响。 相似文献
34.
35.
Da SHU Baode SUN Ke LI Jun WANG Yaohe ZHOUState Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University Shanghai China 《材料科学技术学报》2003,19(3):221-225
The continuous separation of inclusions from aluminum melt flowing in a circular pipe using a high frequency magneticfield was investigated both theoretically and experimentally The separation efficiency was calculated based on thetrajectory method and compared with experimental results. It is found that the separation efficiency is a functilnondimensional parameters t_i·d_p~2B_e~2/μ_fμ_eα~2 and α/δ.The effective way to improve the separation efficiency is to increasethe effective magnetic flux density and decrease the pipe radius. and the value of α/δ should be kept about 2 in orderto obtain the optimum separation efficiency. 相似文献
36.
37.
节理岩体的代表单元集合体模型及弹性参数预测 总被引:8,自引:0,他引:8
本文明确提出了节理岩体“代表单元集合体”的概念和模型,通过对节理岩体的“代表单元集合体”进行数值模拟,研究了节理岩体的“代表单元集合体”的变形特性,建立了节理岩体的弹性模型,提出了预测节理岩体宏观等效弹性参数的计算机模拟方法,并将其应用于岩体工程稳定性分析中。 相似文献
38.
39.
40.
Yaping KeLU 《材料科学技术学报》2002,18(6):492-496
In this paper,glass transition and thermal stability of the Zr-Al-Cu-Ni metallic glasses were investigated by using electrical resistance measurement(ERM),DSC and X-ray diffraction techniques.The experimental results show that the ERM is capable of detecting the glass transition of the amorphous alloys and can help to distinguish the crystallization products of the Zr-Al-Cu-Ni metallic glasses owing to the difference of the electrical resistivity between the precipitation phases. 相似文献