全文获取类型
收费全文 | 83826篇 |
免费 | 10597篇 |
国内免费 | 6479篇 |
专业分类
电工技术 | 7704篇 |
技术理论 | 1篇 |
综合类 | 7924篇 |
化学工业 | 11377篇 |
金属工艺 | 5495篇 |
机械仪表 | 5580篇 |
建筑科学 | 6451篇 |
矿业工程 | 3248篇 |
能源动力 | 2415篇 |
轻工业 | 7981篇 |
水利工程 | 2550篇 |
石油天然气 | 3701篇 |
武器工业 | 1215篇 |
无线电 | 9857篇 |
一般工业技术 | 8259篇 |
冶金工业 | 3378篇 |
原子能技术 | 1175篇 |
自动化技术 | 12591篇 |
出版年
2024年 | 634篇 |
2023年 | 1924篇 |
2022年 | 4100篇 |
2021年 | 5420篇 |
2020年 | 3824篇 |
2019年 | 2715篇 |
2018年 | 2856篇 |
2017年 | 3122篇 |
2016年 | 2802篇 |
2015年 | 4101篇 |
2014年 | 4912篇 |
2013年 | 5729篇 |
2012年 | 6831篇 |
2011年 | 7036篇 |
2010年 | 6317篇 |
2009年 | 6000篇 |
2008年 | 6065篇 |
2007年 | 5544篇 |
2006年 | 4712篇 |
2005年 | 3986篇 |
2004年 | 2722篇 |
2003年 | 1904篇 |
2002年 | 1720篇 |
2001年 | 1490篇 |
2000年 | 1272篇 |
1999年 | 821篇 |
1998年 | 439篇 |
1997年 | 379篇 |
1996年 | 332篇 |
1995年 | 261篇 |
1994年 | 226篇 |
1993年 | 134篇 |
1992年 | 119篇 |
1991年 | 85篇 |
1990年 | 65篇 |
1989年 | 60篇 |
1988年 | 37篇 |
1987年 | 30篇 |
1986年 | 38篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 22篇 |
1979年 | 18篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1959年 | 31篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
针对碳酸盐岩气藏部分气井生产效能低的状况,决定在长庆气田下古生界尝试开展加砂压裂重复改造试验,以期提高低产、低效气井的产量,延长气田稳产期。通过潜心研究、精细设计及现场质检监控,优选了4口老井进行加砂压裂重复改造现场试验。从试验结果来看,虽然只有1口井取得明显的改造效果,但4口井加砂压裂施工都是成功的,说明对碳酸盐岩气藏实施加砂压裂是可以实现的,但在选井思路和压裂工艺方面还有待探索和研究。 相似文献
102.
103.
毛家河水电站库区岩溶发育特征及邻谷渗漏分析 总被引:1,自引:0,他引:1
毛家河水电站位于碳酸盐岩地区,库首距左岸邻谷可渡河14—23km、距右岸邻谷北盘江干流14.8km,水库两岸大型落水洞、溶洞及地下岩溶管道相对较为发育。为初步判断水库存在邻谷渗漏的可能性,对水库两岸可溶岩地层岩溶发育形态、特征及规律进行了勘察,并根据现场地质调查资料对3条可疑渗漏带进行了分析论证。 相似文献
104.
Transglutaminase (TGase) was separated from the culture broth of an isolated strain of Streptoverticillium mobaraense. The crude enzyme was prepared by centrifugation, ultrafiltration, precipitation by alcohol, centrifugation and freeze‐drying. The yield after these processes was 65–70%. Then the enzyme was purified to homogeneity by chromatography on CM‐cellulose and Sephadex G‐75 on which the yields were about 70% and 80%, respectively; the purified folds reached 2.5–4.7 and 1.08–2.06, respectively. The molecular weight of this TGase was 39,500–40,100 Da by gel filtration chromatography. Optimum enzyme activity was observed in the pH range of 5.0–7.0, and it was maintained stable at 20–40C. The optimal temperature and pH was 52C and 6.0, respectively. At 1 mM and 5 mM metal ion or inhibitors concentration, TGase activity was strongly inhibited by Zn2+ and NEM, and not affected obviously by Ba2+, Ca2+, Co2+, Cu2+, Fe2+, Fe3+, Mg2+, Mn2+, Na+ as well as PMSF and EDTA. The effects of these additions on this TGase were compared with those of other microbial TGases. 相似文献
105.
106.
Y. L. Hao R. Yang M. Niinomi D. Kuroda Y. L. Zhou K. Fukunaga A. Suzuki 《Metallurgical and Materials Transactions A》2003,34(4):1007-1012
Alloys for implant devices require improved strength but a reduced Young’s modulus, in order to become mechanically more compatible
with adjacent bone tissues. In this study, a new metastable β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (wt pct), was subjected to aging treatment to produce different microstructures,
and the resulting mechanical properties, including the Young’s modulus, were measured. The Young’s modulus of this alloy is
found to be sensitive to microstructures generated by various heat treatments. For microstructures varying from (α + β) to (α + β + ω) and (β + ω), the Young’s modulus increases with an accompanying increase in tensile strength and hardness, but decreases in ductility.
The (β + ω) microstructure has a low strength, high modulus, and poor ductility and cannot be used for biomedical applications. For
an (α + β) microstructure, the volume fraction of the phases is shown to be the main factor that determines the mechanical properties. 相似文献
107.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献
108.
Hao Chen 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(5):1854-1856
We prove a result which reduces the computation of the linear complexity of a sequence over GF(pm) (p is an odd prime) with period 2n (n is a positive integer such that there exists an element bisinGF(pm), bn=-1) to the computation of the linear complexities of two sequences with period n. By combining with some known algorithms such as the Berlekamp-Massey algorithm and the Games-Chan algorithm we can determine the linear complexity of any sequence over GF(pm) with period 2tn (such that 2 t|pm-1 and gcd(n,pm-1)=1) more efficiently 相似文献
109.
田长乐 《粉末冶金材料科学与工程》2003,8(4):363-366
从毛坯厚度差、装舟方式、冷却速度、舟皿涂料等方面分析了YG8和J12硬质合金长条薄片的弯曲变形原因,提出了几种抑制弯曲变形的措施。 相似文献
110.