全文获取类型
收费全文 | 613633篇 |
免费 | 7042篇 |
国内免费 | 2503篇 |
专业分类
电工技术 | 11098篇 |
综合类 | 800篇 |
化学工业 | 89980篇 |
金属工艺 | 24711篇 |
机械仪表 | 19340篇 |
建筑科学 | 13502篇 |
矿业工程 | 3344篇 |
能源动力 | 16616篇 |
轻工业 | 45781篇 |
水利工程 | 6556篇 |
石油天然气 | 12160篇 |
武器工业 | 56篇 |
无线电 | 73703篇 |
一般工业技术 | 123900篇 |
冶金工业 | 115702篇 |
原子能技术 | 14390篇 |
自动化技术 | 51539篇 |
出版年
2021年 | 5352篇 |
2020年 | 4069篇 |
2019年 | 5215篇 |
2018年 | 8874篇 |
2017年 | 8914篇 |
2016年 | 9526篇 |
2015年 | 6117篇 |
2014年 | 10170篇 |
2013年 | 28783篇 |
2012年 | 16313篇 |
2011年 | 22121篇 |
2010年 | 17533篇 |
2009年 | 20094篇 |
2008年 | 20522篇 |
2007年 | 20357篇 |
2006年 | 18048篇 |
2005年 | 16359篇 |
2004年 | 15844篇 |
2003年 | 15586篇 |
2002年 | 14869篇 |
2001年 | 14777篇 |
2000年 | 13900篇 |
1999年 | 14622篇 |
1998年 | 37020篇 |
1997年 | 25810篇 |
1996年 | 19812篇 |
1995年 | 14940篇 |
1994年 | 13076篇 |
1993年 | 13198篇 |
1992年 | 9452篇 |
1991年 | 8936篇 |
1990年 | 8799篇 |
1989年 | 8504篇 |
1988年 | 7990篇 |
1987年 | 7065篇 |
1986年 | 7013篇 |
1985年 | 7791篇 |
1984年 | 7138篇 |
1983年 | 6530篇 |
1982年 | 6058篇 |
1981年 | 6157篇 |
1980年 | 5898篇 |
1979年 | 5588篇 |
1978年 | 5591篇 |
1977年 | 6325篇 |
1976年 | 8298篇 |
1975年 | 4749篇 |
1974年 | 4565篇 |
1973年 | 4671篇 |
1972年 | 3920篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
71.
Carroll R.D. Merritt S.W. Branciforte E.J. Tanski W.J. Cullen D.E. Sacks R.N. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1994,41(3):416-418
Heterostructure Acoustic Charge Transport (HACT) devices have been fabricated with a new nondestructive sense (NDS) electrode structure that provides for the recovery of base-band signals without the use of an integrating capacitor. This electrode structure provides an output signal comprising an RF carrier at the SAW frequency, amplitude modulated by the sampled input signal which has been delayed by a period proportional to the output electrodes distance from the input diode. The output of the NDS electrode structure is subsequently demodulated to provide the base-band signal 相似文献
72.
MB Heyman JM LaBerge KA Somberg P Rosenthal C Mudge EJ Ring JD Snyder 《Canadian Metallurgical Quarterly》1997,131(6):914-919
The transjugular intrahepatic portosystemic shunt procedure is an accepted treatment for adults with complications of portal hypertension. We performed a retrospective review of all pediatric TIPS placements performed at the University of California, San Francisco between 1990 and 1996. Twelve procedures were attempted in nine children, with a mean age (+/- SD) of 9.4 +/- 3.9 years (range, 5 to 15 years) and a mean weight of 31 +/- 18 kg (range, 16 to 70 kg). The indications for TIPS placement were portal hypertension complicated by chronic variceal hemorrhage not controlled with sclerotherapy (n = 7) and hypersplenism with thrombocytopenia (n = 2). TIPS placement was successfully completed initially in seven of nine (78%) patients. Unfavorable vascular anatomy was the cause of failure in two cases. The seven patients who underwent successful TIPS placement were followed up for an average of 136 days (range, 1 to 800 days); two still have patent shunts, three underwent liver transplantation, one had a splenorenal shunt after stenosis, and one died of underlying liver disease. Variceal bleeding was controlled in four of five patients who successfully underwent TIPS placement. Shunt occlusion occurred in four patients; patency was restored by transjugular shunt revision in three, and a splenorenal shunt was performed in one. 相似文献
73.
Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal 相似文献
74.
75.
76.
77.
A case of endometrioid carcinoma arising from endometriosis of the sigmoid colon is reported. The patient had been treated with unopposed continuous estrogen injection for twenty years after bilateral salpingo-oophorectomy because of severe endometriosis. The pathology, pertinent literature and implications of the present case are discussed. 相似文献
78.
Serum vanadium, aluminum, silicon and beta 2-microglobulin levels as well as the red cell count, hemoglobin and systolic blood pressure were simultaneously measured in 80 chronic hemodialysis patients. The serum vanadium level was positively correlated with the serum levels of aluminum, silicon and beta 2-microglobulin as well as the systolic blood pressure, and was inversely correlated with the red cell count and hemoglobin. The mean serum vanadium level was 18.4 +/- 7.6 ng/ml before hemodialysis and decreased to 13.0 +/- 5.30 ng/ml at the completion of dialysis. The dialysate vanadium level increased from 0.4 +/- 0.2 (inflow) to 1.0 +/- 0.4 ng/ml (outflow). It was concluded that vanadium was transferred from blood to dialysate when purified water was used in the preparation of the dialysate. 相似文献
79.
PURPOSE: To assess the role postoperative mydriatics play after extracapsular cataract extraction (ECCE) and posterior chamber intraocular lens (IOL) implantation in causing iris modifications and in controlling inflammation. SETTING: Outpatients Department, Ninewells Hospital, Dundee, Scotland. METHODS: The prospective study comprised 136 patients who had standardized ECCE. Half the patients used a mydriatic for 2 weeks postoperatively. Anterior chamber activity, pain, and eye redness were evaluated at 2 weeks postoperatively; pupil shape, peripheral anterior synechias, IOL position, and iris adhesions, at 6 weeks. RESULTS: Iris-lens adhesions were significantly more common in the group using a mydriatic. There was no difference between the two groups in postoperative inflammation. CONCLUSION: Mydriatics should not be used routinely after ECCE with posterior chamber IOL implantation. 相似文献
80.
S. R. Meschyan 《Soil Mechanics and Foundation Engineering》1996,33(1):16-20
A comparison is made between different alternate schemes for determination of the strength of soils possessing rheological
properties on the basis of our own experimental data. An original method is proposed for determination of the ultimate long-term
strength from tests on the conditionally instantaneous failure of soil after preliminary deformation in a creep regime, as
well as from tests in a controlled-deformation regime.
Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 14–18, January–February, 1996. 相似文献