全文获取类型
收费全文 | 275410篇 |
免费 | 22391篇 |
国内免费 | 12393篇 |
专业分类
电工技术 | 16113篇 |
技术理论 | 20篇 |
综合类 | 17908篇 |
化学工业 | 45806篇 |
金属工艺 | 14235篇 |
机械仪表 | 16182篇 |
建筑科学 | 21845篇 |
矿业工程 | 6875篇 |
能源动力 | 7577篇 |
轻工业 | 21359篇 |
水利工程 | 5148篇 |
石油天然气 | 13850篇 |
武器工业 | 2076篇 |
无线电 | 33361篇 |
一般工业技术 | 33267篇 |
冶金工业 | 13354篇 |
原子能技术 | 2919篇 |
自动化技术 | 38299篇 |
出版年
2024年 | 1317篇 |
2023年 | 4452篇 |
2022年 | 8349篇 |
2021年 | 11169篇 |
2020年 | 8398篇 |
2019年 | 6858篇 |
2018年 | 7473篇 |
2017年 | 8618篇 |
2016年 | 7848篇 |
2015年 | 10542篇 |
2014年 | 13731篇 |
2013年 | 17145篇 |
2012年 | 17858篇 |
2011年 | 19931篇 |
2010年 | 17059篇 |
2009年 | 16432篇 |
2008年 | 15867篇 |
2007年 | 15069篇 |
2006年 | 14921篇 |
2005年 | 12794篇 |
2004年 | 8841篇 |
2003年 | 7635篇 |
2002年 | 7166篇 |
2001年 | 6352篇 |
2000年 | 5912篇 |
1999年 | 6455篇 |
1998年 | 5695篇 |
1997年 | 4685篇 |
1996年 | 4251篇 |
1995年 | 3510篇 |
1994年 | 2928篇 |
1993年 | 2313篇 |
1992年 | 1820篇 |
1991年 | 1352篇 |
1990年 | 1074篇 |
1989年 | 924篇 |
1988年 | 711篇 |
1987年 | 518篇 |
1986年 | 412篇 |
1985年 | 340篇 |
1984年 | 220篇 |
1983年 | 207篇 |
1982年 | 172篇 |
1981年 | 154篇 |
1980年 | 150篇 |
1979年 | 108篇 |
1978年 | 64篇 |
1977年 | 65篇 |
1976年 | 77篇 |
1973年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
A FISH technique for simultaneous detection of fluorescent R-band and in situ hybridization signals]
BACKGROUND: Because of serious adverse effects of centrally acting antitussive agents, is necessary to find new drugs with cough-suppressing activity. Medicinal herbs are a potential source of polysaccharides with high antitussive efficiency and on the other with minimal side effects. AIM: The study was to assess the antitussive action of mixture of a polysaccharides (RL) and polysaccharide-xylan (XY), both isolated from above-ground parts of Rudbeckie fulgida var. sullivantii. The observed activity was compared to those of narcotic and nonnarcotic antitussive substances used in clinical practice. METHODS: Cough was evoked by mechanical irritation of the airways in nonanaesthetized cats with chronic tracheal cannuly. The plant substances were administered perorally in the dose of 50 mg per kg body weight. RESULTS: Results indicate, that administration of RL induced a suppression of the followed cough parameters from both areas of airways (total fall in cough parameters by 46.6%). Administration of xylan induced the fall in the followed cough parameters with more significant influence on the laryngopharyngeal area of the airways (total fall in cough parameters 48.2%). CONCLUSION: Administration of RL and xylan did not achieve the effect of codeine, but had a more intensive antitussive effect than the peripherally acting droprozine and prenoxdiazine. (Fig. 3, Ref. 11.) 相似文献
972.
973.
974.
强激光热斑形成及其稳定性研究 总被引:2,自引:0,他引:2
在论述热点跟踪及其传热机理时将靶材的比热溶、热传导系、在激光的热藕合系数均考虑成温度和时间的函数,又考虑靶材在运动时将激光辐照物体时热点的建立及其稳定情况作一动态数值模拟,为热点跟踪作准备。 相似文献
975.
976.
丁苯嵌段共聚物与醋酸乙烯酯本体接枝物表征的研究 总被引:1,自引:0,他引:1
本文主要对接枝共聚物SBS-g-VAC的红外光谱(IR)、核磁共振潜(NMR)、透射电镜(TEM)、扫描电镜(SEM)的表征工作进行了讨论,表明了接枝物SBS-g-VAC的存在及其结构特征。 相似文献
977.
Li Qiu Tongwen Chen 《Automatic Control, IEEE Transactions on》1994,39(12):2506-2511
Treating causality constraints, this paper studies optimal synthesis of multirate sampled-data systems with an ℋ2 performance criteria. An explicit solution is obtained by input-output space extensions (lifting) and frequency-domain techniques 相似文献
978.
979.
In some multiple treatment arm clinical trials there is an order of preference for the treatments based on secondary considerations like toxicity or cost. In this paper, we consider the case where two or more treatments could have equal prior preference. This formulation includes the problem of comparing several equally preferred experimental treatments to one control, or the comparison of a combination with its components. Our decision procedures will guarantee a high selection probability for the correct treatment(s) when that selection is appropriate. We establish sample size requirements for our decision procedures which can be applied to clinical trials with normal, binomial, or right censored exponential endpoints. 相似文献
980.
P. Chen D. Cline W. Craddock F.J. Decker R. Iverson T. Katsouleas P. Kwok W. Leemans S. Masuda D.D. Meyerhofer K. Nakajima A. Ogata P. Raimondi A. Sessler D. Walz A. Weidemann 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1998,410(3):407-417
The proposed plasma lens experiment at the Final focus Test Beam (FFTB) facility of the Stanford Linear Accelerator Center has been approved by the adminstration. The experiment would allow the examination of plasma focusing devices for particle beams in the parameter regime of interest to future high-energy colliders. It is expected to lead to compact plasma lens designs capable of focusing the beam to unprecedented small spot sizes. 相似文献