全文获取类型
收费全文 | 289592篇 |
免费 | 21509篇 |
国内免费 | 11081篇 |
专业分类
电工技术 | 15411篇 |
技术理论 | 31篇 |
综合类 | 17443篇 |
化学工业 | 50225篇 |
金属工艺 | 16879篇 |
机械仪表 | 18433篇 |
建筑科学 | 22870篇 |
矿业工程 | 9524篇 |
能源动力 | 7965篇 |
轻工业 | 16672篇 |
水利工程 | 4783篇 |
石油天然气 | 20267篇 |
武器工业 | 2243篇 |
无线电 | 31473篇 |
一般工业技术 | 34387篇 |
冶金工业 | 15270篇 |
原子能技术 | 2857篇 |
自动化技术 | 35449篇 |
出版年
2024年 | 1220篇 |
2023年 | 4676篇 |
2022年 | 7924篇 |
2021年 | 11454篇 |
2020年 | 8535篇 |
2019年 | 7273篇 |
2018年 | 8169篇 |
2017年 | 9220篇 |
2016年 | 8027篇 |
2015年 | 11176篇 |
2014年 | 13777篇 |
2013年 | 16457篇 |
2012年 | 17755篇 |
2011年 | 19410篇 |
2010年 | 16758篇 |
2009年 | 15913篇 |
2008年 | 15447篇 |
2007年 | 15093篇 |
2006年 | 15980篇 |
2005年 | 14149篇 |
2004年 | 9047篇 |
2003年 | 7905篇 |
2002年 | 7309篇 |
2001年 | 6484篇 |
2000年 | 7105篇 |
1999年 | 8502篇 |
1998年 | 6849篇 |
1997年 | 5824篇 |
1996年 | 5452篇 |
1995年 | 4507篇 |
1994年 | 3757篇 |
1993年 | 2628篇 |
1992年 | 2138篇 |
1991年 | 1601篇 |
1990年 | 1173篇 |
1989年 | 934篇 |
1988年 | 759篇 |
1987年 | 523篇 |
1986年 | 389篇 |
1985年 | 265篇 |
1984年 | 183篇 |
1983年 | 120篇 |
1982年 | 130篇 |
1981年 | 86篇 |
1980年 | 70篇 |
1979年 | 25篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
881.
溅渣护炉技术在转炉上的应用 总被引:2,自引:0,他引:2
从1996年开始实施溅渣护炉试验研究,一年来的工业性试验与实验室研究表明:所用的溅渣护炉工艺参数基本可行,溅渣护炉条件下复吹比达50%,炉衬砖消耗下降0.7kg/t,喷补料消耗下降1.22kg/t。试验证明开发新型调渣剂是进一步提高溅渣护炉效果的重要措施。 相似文献
882.
883.
42 patients with chronic urinary retention caused by BPH were treated by means of Mesh-like tubular stent placing from August 1993 to August 1994. The mesh-like tubular stent was made of nickel titanium alloy in sizes of 2.0 x 1.5 cm, 2.5 x 1.5 cm, 3.0 x 1.5 cm respectively. Under direct vision the stent was placed with the deployment tool. The desirable position of the stent is 0.3-0.5 cm proximal to the internal urethral orifice, 0.5 cm distal to the verumontanum. In 38 patients followed up for 1-6 months, 34 were succesful with an effective rate of 80%. IPSS, PUFR, RUV after 1, 3, 6 months of placement were 8.5 +/- 4.4, 6.8 +/- 3.5, 7.1 +/- 5.2; 12.5 +/- 6.0 ml/s, 14.0 +/- 5.2 ml/s, 14.4 +/- 8.1 ml/s; 43 +/- 11.5 ml, 47.4 +/- 13.3 ml, 44.5 +/- 15.7 ml respectively. Four stents were taken away transurethrally in the unsuccessful cases. The results indicat that there are no serious complications except for shorttime hematuria, fever, and bladder irritation. The success depends chiefly upon exactly meassuring the length of prostatic urethra, selecting the rational size of the stent, and correctly placing the stent. 相似文献
884.
用Nardini-Brebbia边界元法计算了动载荷下的应力强度因子,与解析解及有限元解相比较,效果较好。最后对计算结果进行了分析讨论。 相似文献
885.
本文对宽带综合通信网交换系统几个主要方面技术的发展趋向作了概括介绍,内容包括:电子交换的分布结构、ATM交换的开始应用,个人通信的无线进网,宽带交换引用光子技术和多媒体交换结构分析。 相似文献
886.
GH Fan J Zhao YL Wu LG Lou Z Zhang Q Jing L Ma G Pei 《Canadian Metallurgical Quarterly》1998,53(4):684-690
The effects of N-methyl-D-aspartate (NMDA) on opioid receptor-mediated G protein activation were explored in neuroblastoma X glioma hybrid (NG108-15) cells. Treatment of the cells with NMDA resulted in a remarkable attenuation of [35S]guanosine-5'-O-(3-thio)triphosphate binding stimulated by [D-Pen2,D-Pen5]-enkephalin (DPDPE), a delta-opioid receptor agonist. The effects of NMDA were dose and time dependent with an IC50 value of 5 nM and could be blocked by NMDA receptor antagonists. After NMDA treatment, the DPDPE dose-response curve shifted to the right (EC50 value increased approximately 7-fold, from 6 to 40 nM), and the maximal response induced by DPDPE was reduced by approximately 60%. The effects of NMDA were reversible, and the DPDPE response could recover within 60 min. The functional responses of delta-, mu-, and kappa-opioid receptors in primarily cultured neurons also were attenuated significantly by NMDA treatment. The inhibitory effects of NMDA on opioid receptor-mediated G protein activation could be blocked by coadministration of the protein kinase C (PKC) inhibitors or by elimination of the extracellular Ca2+. Correspondingly, NMDA treatment of NG108 cells significantly elevated cellular PKC activity and stimulated Gialpha2 phosphorylation. Transient transfection into NG108-15 cells of the wild-type Gialpha2 and a mutated Gialpha2 (Ser144Ala) resulted in a 2-fold increase in DPDPE-stimulated G protein activation. The DPDPE responses were greatly inhibited by NMDA treatment in the wild-type Gialpha2-transfected cells but much less affected in the mutant Gialpha2-transfected cells. In summary, NMDA attenuates opioid receptor/G protein coupling, and this process requires activation of PKC. 相似文献
887.
888.
Y Zhang HP Hetherington EM Stokely GF Mason DB Twieg 《Canadian Metallurgical Quarterly》1998,39(6):999-1004
OBJECTIVE: To report our experience with erosion of permanent suture or mesh material after abdominal sacrocolpopexy. METHODS: A retrospective chart review was performed to identify patients who underwent sacrocolpopexy by the same surgeon over 8 years. Demographic data, operative notes, hospital records, and office charts were reviewed after sacrocolpopexy. Patients with erosion of either suture or mesh were treated initially with conservative therapy followed by surgical intervention as required. RESULTS: Fifty-seven patients underwent sacrocolpopexy using synthetic mesh during the study period. The mean (range) postoperative follow-up was 19.9 (1.3-50) months. Seven patients (12%) had erosions after abdominal sacrocolpopexy with two suture erosions and five mesh erosions. Patients with suture erosion were asymptomatic compared with patients with mesh erosion, who presented with vaginal bleeding or discharge. The mean (+/-standard deviation) time to erosion was 14.0+/-7.7 (range 4-24) months. Both patients with suture erosion were treated conservatively with estrogen cream. All five patients with mesh erosion required transvaginal removal of the mesh. CONCLUSION: Mesh erosion can follow abdominal sacrocolpopexy over a long time, and usually presents as vaginal bleeding or discharge. Although patients with suture erosion can be managed successfully with conservative treatment, patients with mesh erosion require surgical intervention. Transvaginal removal of the mesh with vaginal advancement appears to be an effective treatment in patients failing conservative management. 相似文献
889.
890.
讨论了底排弹射程标准化方法所满足的要求,分析了现行底排弹射程标准化方法存在的问题,对底排减阻模型进行了改进,并对试验数据进行了分析处理。 相似文献