全文获取类型
收费全文 | 104610篇 |
免费 | 10889篇 |
国内免费 | 6808篇 |
专业分类
电工技术 | 7378篇 |
技术理论 | 4篇 |
综合类 | 9068篇 |
化学工业 | 15243篇 |
金属工艺 | 6479篇 |
机械仪表 | 7073篇 |
建筑科学 | 7943篇 |
矿业工程 | 3410篇 |
能源动力 | 2911篇 |
轻工业 | 9476篇 |
水利工程 | 2689篇 |
石油天然气 | 4236篇 |
武器工业 | 1223篇 |
无线电 | 12782篇 |
一般工业技术 | 11437篇 |
冶金工业 | 4282篇 |
原子能技术 | 1462篇 |
自动化技术 | 15211篇 |
出版年
2024年 | 538篇 |
2023年 | 1607篇 |
2022年 | 3489篇 |
2021年 | 4613篇 |
2020年 | 3298篇 |
2019年 | 2613篇 |
2018年 | 2856篇 |
2017年 | 3210篇 |
2016年 | 3120篇 |
2015年 | 4544篇 |
2014年 | 5586篇 |
2013年 | 6646篇 |
2012年 | 7726篇 |
2011年 | 8259篇 |
2010年 | 7671篇 |
2009年 | 7050篇 |
2008年 | 7318篇 |
2007年 | 6744篇 |
2006年 | 6382篇 |
2005年 | 5301篇 |
2004年 | 3975篇 |
2003年 | 3192篇 |
2002年 | 3347篇 |
2001年 | 2910篇 |
2000年 | 2326篇 |
1999年 | 1634篇 |
1998年 | 1147篇 |
1997年 | 946篇 |
1996年 | 863篇 |
1995年 | 740篇 |
1994年 | 617篇 |
1993年 | 476篇 |
1992年 | 355篇 |
1991年 | 278篇 |
1990年 | 209篇 |
1989年 | 167篇 |
1988年 | 136篇 |
1987年 | 91篇 |
1986年 | 74篇 |
1985年 | 49篇 |
1984年 | 33篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 37篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1959年 | 12篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
31.
广东省大型工程建设中天然放射性核素引起的环境问题 总被引:2,自引:0,他引:2
本文介绍了广东省境内几个大型基本建设工程项目中天然放射性核素引起的环境问题及有关治理对策,并就今后类似建设项目的辐射环境保护工作提出了建议。 相似文献
32.
Min-Seok Park Vladislav P. Vislovskiy Jong-San Chang Yong-Gun Shul Jin S. Yoo Sang-Eon Park 《Catalysis Today》2003,87(1-4):205-212
Alumina-supported vanadium oxide, VOx/Al2O3, and binary vanadium–antimony oxides, VSbOx/Al2O3, have been tested in the ethylbenzene dehydrogenation with carbon dioxide and characterized by SBET, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction and CO2 pulse methods. VSbOx/Al2O3 exhibited enhanced catalytic activity and especially on-stream stability compared to VOx/Al2O3 catalyst. Incorporation of antimony into VOx/Al2O3 increased dispersion of active VOx species, enhanced redox properties of the systems and formed a new mixed vanadium–antimony oxide phase in the most catalytically efficient V0.43Sb0.57Ox/Al2O3 system. 相似文献
33.
34.
A tennis novice watching a match for the first time might be surprised that the crowd erupts with cheers when a player wins one point, then barely applauds when he wins the next. The crowd is not necessarily fickle; some points are genuinely more important than others because a tennis match is hierarchically structured. One match consists of several sets. One set consists of several games. One game consists of several points. The match-winning point is the most important one. How can we make that importance visible? Our goal is to let a fan, a player, or a coach examine tennis data visually, extract the interesting parts, and jump from one item to another quickly and easily. The visualization tool should help parse the elements of a match. We developed an interactive system called TennisViewer to visualize the dynamic, tree-structured data representing a tennis match. It provides an interface for users to quickly explore tennis match information. The visualization tool reveals the overall structure of the match as well as the fine details in a single screen. It uses a 2D display of translucent layers, a design that contains elements of Tree-Maps and of the Visual Scheduler system, which was designed to help faculty and students identify mutually available (transparent) time slots when arranging group meetings. TennisViewer provides MagicLens filters to explore specialized views of the information and a time-varying display to animate all or part of a match 相似文献
35.
Prostate development and disease are androgen dependent. However, the nature of hormonal effects on the prostate of healthy young men is not clear. We, therefore, measured prostate size in males chronically exposed to high doses of androgens (AS; habitual anabolic steroid abusers; n = 15) or estrogens (E; male to female transsexuals; n = 11) and compared the results with those in age-matched healthy eugonadal men without known prostate disorders. Prostate size was measured by planimetric ultrasound as cross-sectional areas and maximal dimensions in three orthogonal dimensions with a 7.5-megahertz B-mode sector scanner biplane in a transrectal transducer at 2.5 mm steps from the base to the apex of prostate. Total prostate volume (TPV) was reconstructed from planimetric sections, central prostate volume (CPV) was calculated by the ellipsoidal formula from the appropriate three maximum dimensions, and peripheral prostate volume was determined by the difference between TPV and CPV. Compared with age-matched controls, TPV was normal (-2%) in AS (P = 0.752) and reduced by 31% in E (P = 0.002), whereas CPV was increased by 20% in AS (P = 0.002) and reduced by 46% in E (P = 0.002), and the ratio of CPV/peripheral prostate volume was increased by 77% in AS (P < 0.001) and decreased by 33% in E (P = 0.047). Blood sex hormone-binding globulin was elevated by nearly 500% in E (P < 0.001), but was reduced by 47% in AS (P = 0.003). Prostate-specific antigen was normal (-6%) in AS (P = 0.799) and decreased by 86% in E (P = 0.002). Prostatic acid phosphatase was increased by 26% in AS (P = 0.007), but was unchanged (-28%) in E (P = 0.106). Total and free testosterone levels were reduced to castrate levels in E, whereas LH, FSH, and total testosterone levels were significantly reduced in AS. We conclude that in the human prostate of young men, CPV is more hormonally sensitive than TPV, and during high dose treatment, CPV is preferentially increased by chronic androgen treatment and decreased by chronic estrogen treatment. The reduction of TPV by estrogens was less than expected if solely attributable to inhibition of endogenous gonadotropin and testosterone secretion, suggesting that estrogens also have a positive effect on the normal human prostate. The reversibility and long term significance of androgen-induced stimulation of CPV and, in particular, its relationship to the onset and severity of benign prostatic hyperplasia remain to be clarified. 相似文献
36.
本文给出从指称语义自动生成解释器后端的一种技术.解释器被表示成PASCAL_like形式. 相似文献
37.
38.
文中简要地介绍了一个具有分散采集信号,集中报警的安全报警器的设计,作者利用单片机的优点和功能,成功地设计了复盖地域大,既简单又灵活的报警器。 相似文献
39.
Jin Hai-sheng Zhang Shu-nong Institute of Environmental Water Science Hohai University Nanjing P.R.China 《水动力学研究与进展(B辑)》1992,(2)
Density stratified flow with both the vertical temperature gradient and the verti-cal salinity gradient is simulated numerically, in which turbulent terms are calculated by a sim-plified turbulence stress/flux algebraic model. The feature of stratification and turbulence is de-scribed correctly by the model. The computational results agree well with the experimental data.However, the k-e turbulence model is not so successful. 相似文献
40.
对WQ-10型煤气平焰烧嘴进行半工业性试验,得到了该烧嘴较长时间运行下的一些性能。结果表明,该烧嘴平火焰稳定,炉顶温度分布均匀,燃烧烟气中CO、NO含量达到了YB/T062-94标准的要求。 相似文献