全文获取类型
收费全文 | 16296篇 |
免费 | 1465篇 |
国内免费 | 691篇 |
专业分类
电工技术 | 992篇 |
技术理论 | 3篇 |
综合类 | 929篇 |
化学工业 | 2877篇 |
金属工艺 | 1014篇 |
机械仪表 | 1003篇 |
建筑科学 | 1183篇 |
矿业工程 | 566篇 |
能源动力 | 479篇 |
轻工业 | 938篇 |
水利工程 | 251篇 |
石油天然气 | 1320篇 |
武器工业 | 110篇 |
无线电 | 1789篇 |
一般工业技术 | 2110篇 |
冶金工业 | 861篇 |
原子能技术 | 175篇 |
自动化技术 | 1852篇 |
出版年
2024年 | 59篇 |
2023年 | 326篇 |
2022年 | 471篇 |
2021年 | 732篇 |
2020年 | 574篇 |
2019年 | 495篇 |
2018年 | 549篇 |
2017年 | 550篇 |
2016年 | 477篇 |
2015年 | 668篇 |
2014年 | 821篇 |
2013年 | 926篇 |
2012年 | 1016篇 |
2011年 | 1119篇 |
2010年 | 931篇 |
2009年 | 914篇 |
2008年 | 931篇 |
2007年 | 808篇 |
2006年 | 830篇 |
2005年 | 706篇 |
2004年 | 570篇 |
2003年 | 486篇 |
2002年 | 457篇 |
2001年 | 384篇 |
2000年 | 358篇 |
1999年 | 424篇 |
1998年 | 317篇 |
1997年 | 302篇 |
1996年 | 263篇 |
1995年 | 239篇 |
1994年 | 194篇 |
1993年 | 138篇 |
1992年 | 107篇 |
1991年 | 71篇 |
1990年 | 70篇 |
1989年 | 47篇 |
1988年 | 29篇 |
1987年 | 26篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1970年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
The synthesis of rare-earth perovskite-type composition thin films of LaNiO3 by means of the inorganic-sol-gel (ISG) method was studied. The structural stability under high temperature in reducing atmospheres and the oxygen-sensitivity mechanism of the LaNiO3 thin films were examined. It is shown that under the experimental conditions, LaNiO3 decomposes and the valance states of nickel are +2 and +3. 相似文献
73.
74.
75.
This paper is concerned with the inversion of confluent Vandermonde matrices. A novel and simple recursive algorithm for inverting confluent Vandermonde matrices is presented. The algorithm is suitable for classroom use in both numerical as well as symbolic computation. Examples are included to illustrate the proposed algorithm. 相似文献
76.
77.
78.
聚焦光束稳态热晕补偿实验 总被引:3,自引:1,他引:2
进行了聚焦光束稳态热晕效应及自适应光学补偿的室内模拟实验观测,获得了在不同热畸变参数情况下,自适应光学系统开闭环时光束远场Strehl比和信标光波前方差的测量结果。测量结果表明自适应光学对聚焦光束整束热晕的补偿效果是显著的。在热畸变参数Nd大于170时,校正剩余波前大差呈非线性增长。在热畸变参数N_d与光束菲涅耳数N_f的比值大于1时,校正后的远场光斑峰值强度随入射功率的增加开始呈下降趋势。 相似文献
79.
Hyperdynamic circulation of cirrhotic rats: role of substance P and its relationship to nitric oxide
CJ Chu FY Lee SS Wang FY Chang YT Tsai HC Lin MC Hou SL Wu CC Tai SD Lee 《Canadian Metallurgical Quarterly》1997,32(8):841-846
BACKGROUND: It has been suggested that excessive formation of nitric oxide (NO) is responsible for the hyperdynamic circulation observed in portal hypertension. Substance P is a neuropeptide partly cleared by the liver and causes vasodilatation through the activation of the endothelial NO pathway. However, there are no previously published data concerning the plasma level of substance P in cirrhotic rats and its relationship to NO. METHODS: Plasma concentrations of substance P and nitrate/nitrite (an index of NO production) were determined in control rats and cirrhotic rats with or without ascites using an enzyme-linked immununosorbent assay and a colorimetric assay, respectively. In addition, systemic and portal hemodynamics were evaluated by a thermodilution technique and catheterization. RESULTS: Cirrhotic rats with and without ascites had a lower systemic vascular resistance (2.6 +/- 0.2 and 3.9 +/- 0.4 mmHg ml(-1) x min x 100 g body weight, respectively) and higher portal pressure (14.6 +/- 0.6 and 11.3 +/- 1.8 mmHg) than control rats (6.5 +/- 0.3 mmHg x ml(-1) x min x 100 g BW and 6.8 +/- 0.2 mmHg, respectively, P < 0.05), and cirrhotic rats with ascites had the lowest systemic vascular resistance. Plasma levels of nitrate/nitrite progressively increased in relation to the severity of liver dysfunction (control rats, 2.7 +/- 0.5 nmol/ml; cirrhotic rats without ascites, 5.6 +/- 1.3 nmol/ml; cirrhotic rats with ascites, 8.3 +/- 2.2 nmol/ml; P < 0.05). Cirrhotic rats with ascites displayed higher plasma values of substance P (57.7 +/- 5.9 pg/ml) than cirrhotic rats without ascites (37.9 +/- 3.1 pg/ml, P < 0.05) and control rats (30.1 +/- 1.0 pg/ml, P < 0.05). There was no significant difference in plasma substance P values between control rats and cirrhotic rats without ascites (P > 0.05). No correlation was found between plasma levels of substance P and nitrate/nitrite (r = 0.318, P > 0.05). CONCLUSIONS: Excessive formation of NO may be responsible, at least partly, for the hemodynamic derangements in cirrhosis. Although substance P may not participate in the initiation of a hyperdynamic circulation in cirrhosis, it may contribute to the maintenance of the hyperdynamic circulation observed in cirrhotic rats with ascites. 相似文献
80.
GaAs半导体中三光子吸收的非线性光电导测量 总被引:2,自引:0,他引:2
采用非线性光电导技术测量2.06μm激光激发的GaAs本征半导体三光子吸收,观察到三光子和单光子吸收的混合光电导,测得了三光子吸收系数.测量结果与理论计算符合较好. 相似文献