全文获取类型
收费全文 | 512368篇 |
免费 | 58296篇 |
国内免费 | 40943篇 |
专业分类
电工技术 | 46453篇 |
技术理论 | 4篇 |
综合类 | 54245篇 |
化学工业 | 63531篇 |
金属工艺 | 35631篇 |
机械仪表 | 35638篇 |
建筑科学 | 38571篇 |
矿业工程 | 21752篇 |
能源动力 | 13299篇 |
轻工业 | 57091篇 |
水利工程 | 17635篇 |
石油天然气 | 18706篇 |
武器工业 | 7542篇 |
无线电 | 53628篇 |
一般工业技术 | 44100篇 |
冶金工业 | 21875篇 |
原子能技术 | 8000篇 |
自动化技术 | 73906篇 |
出版年
2024年 | 3314篇 |
2023年 | 8537篇 |
2022年 | 19782篇 |
2021年 | 25193篇 |
2020年 | 18347篇 |
2019年 | 12958篇 |
2018年 | 13611篇 |
2017年 | 16021篇 |
2016年 | 14686篇 |
2015年 | 23076篇 |
2014年 | 28903篇 |
2013年 | 34015篇 |
2012年 | 42023篇 |
2011年 | 44181篇 |
2010年 | 41806篇 |
2009年 | 39810篇 |
2008年 | 41166篇 |
2007年 | 39787篇 |
2006年 | 34240篇 |
2005年 | 27800篇 |
2004年 | 20050篇 |
2003年 | 13631篇 |
2002年 | 12998篇 |
2001年 | 11661篇 |
2000年 | 9426篇 |
1999年 | 4115篇 |
1998年 | 1834篇 |
1997年 | 1491篇 |
1996年 | 1240篇 |
1995年 | 1076篇 |
1994年 | 870篇 |
1993年 | 719篇 |
1992年 | 531篇 |
1991年 | 456篇 |
1990年 | 382篇 |
1989年 | 328篇 |
1988年 | 230篇 |
1987年 | 164篇 |
1986年 | 156篇 |
1985年 | 103篇 |
1984年 | 77篇 |
1983年 | 72篇 |
1982年 | 61篇 |
1981年 | 112篇 |
1980年 | 145篇 |
1979年 | 76篇 |
1977年 | 40篇 |
1976年 | 83篇 |
1959年 | 87篇 |
1951年 | 85篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
51.
A pilot-scale fluidised pellet bed (FPB) bioreactor, which combines chemical coagulation, biological degradation, particle pelletisation and separation in one unit, was applied for onsite wastewater treatment and reuse. As a result of rational use of inorganic coagulant and organic polymer and moderate mechanical agitation, spherical particles were generated in the upflow column and a well-fluidised bed was formed. With a continuous supply of dissolved oxygen through a recycling loop, an aerobic condition was kept in the bottom section of the FPB column. Under such conditions the pellets in the FPB column showed the following characteristics: (1) compact structure and high density; (2) rich in microorganisms; and (3) high MLSS and MLVSS concentrations. Therefore, the FPB bioreactor achieved more than 90% removal of SS, COD, BOD and TP from raw domestic wastewater within a total hydraulic retention time (HRT) of only about 30 minutes. It also showed nitrification and denitrification ability and the TN removal could be about 50% as the recycling ratio was increased to 1:1. The treated water quality is generally competitive with the secondary effluent from a conventional activated sludge process. With these advantages the FPB bioreactor is recommendable as a compact system for onsite wastewater treatment and reuse. 相似文献
52.
Peng Dangcong Jin Qiting 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,58(1):89-93
The anaerobic digestion of alkaline black liquor from a cereal straw pulping mill was studied in batch (serum bottles) and continuous systems (up-flow anaerobic sludge blanket reactor—UASB). The batch digestion studies confirmed that lignin and related compounds (LRC) in the alkaline black liquor were the main inhibitory substances and could not be decomposed by anaerobic bacteria. At organic loading rates of 5–10 kg COD m?3 day?1, the UASB reactor achieved 50–60% COD removal efficiencies. Gas production was 2–3 dm3 per dm3 of alkaline black liquor. Two different sludge types were examined in the reactor: granular and cluster-like sludges. Sludge in a cluster, which involved many small granules and flocs, tended to form larger aggregates and possessed good settling ability. 相似文献
53.
研究了温度及气体压力对漂移室(工作于正比区)气体放大倍数的影响,温度和气体压力的变化范围分别是5 ̄40℃及90 ̄105kPa。用实验数据拟合得到了函数关系并测量了几种饱和度下函数中的参数值。 相似文献
54.
岩石样品中铷的中子活化分析 总被引:1,自引:0,他引:1
研究了苦味酸溶液的pH变化对用18-C-6(18C6)的硝基苯溶液定量萃取Rb的影响及18C6浓度变化对定量萃取Rb的影响,确定了定量反萃Rb的实验条件。作出了磷酸锆无机离子交换柱上的Rb-Cs分离曲线。测定了岩石样品的微量Rb和痕量^84Rb。 相似文献
55.
Exhaustive characterizations of antisera to the structurally related peptides pancreatic polypeptide (PP), neuropeptide Y (NPY), and peptide YY (PYY) enabled us to establish the developmental pattern of these peptides in rat and mouse pancreas. PYY was the earliest detectable peptide and was present in all early appearing endocrine cell types. NPY appeared later and occurred exclusively in a subpopulation of insulin cells, whereas PP cells arose latest. At the earliest stage studied, all endocrine cells stored PYY. Most of these cells also contained glucagon. Subsequently, the endocrine cells comprised glucagon+PYY cells and glucagon+PYY+insulin cells. Later, cells storing either only insulin or insulin+PYY appeared. Quantitations of the relative numbers of these cell populations during development were consistent with a precursor role of triple-positive (insulin+glucagon+PYY) cells. Moreover, bromodeoxyuridine (BrdU) injections at E15.5 showed that a large percentage of triple-positive cells were in S-phase and therefore were actively dividing, whereas almost no pure insulin cells or insulin+PYY cells synthesized DNA at this time. These results suggest that PYY-positive endocrine cells may represent precursors for mature islet cells. 相似文献
56.
57.
李莹 《电脑与微电子技术》2012,(12):73-76
通过编写程序输出数学曲线,具有一定的趣味性,可以开阔编程视野。只要具有初级程序设计能力,再结合有关数学知识就能实现。程序设计的思想是利用数学公式求得多个位置值,用Tab函数定位,用Print语句在这些位置上分别输出符号“”,从而得到由多个“”组成的数学曲线,例如三角函数曲线、抛物线曲线、半圆曲线及概率曲线等。 相似文献
58.
59.
The digital content market is undergoing an evolution in networking and digitalization technologies, offering diverse information and services. Due to the characteristics of these emerging technologies, the digital content market is growing rapidly and traditional content providers face service transformation decisions. While a majority of the previous technology adoption studies have focused on the viewpoints of users and customers, cost reduction, or electronic channel related technologies, in this research we analyze the emerging technology adoption decisions of competing firms for providing new content services from a strategic perspective. Utilizing game theoretical models, we examine the effects of market environments (technology cost, channel cannibalization, brand power, brand extension, information asymmetry and market uncertainty) on firms’ adoption decisions. This research contributes a number of unique and interesting implications for the issues of emerging technology adoption for new content service provision. 相似文献
60.
Xiao-Zheng Jin Guang-Hong Yang Wei-Wei Che 《International Journal of Control, Automation and Systems》2012,10(6):1102-1110
This paper utilizes the adaptive technique to design a class of active synchronizing masterslave large scale systems against imperfect actuators and networked interconnections with bias faults and signal attenuations, respectively. Without the requirement of knowledge of eventual faulty factors of bias-actuators on systems, and attenuation factors of connected networks, an adaptive mechanism is designed to estimate each unknown faulty factor on-line for constructing a class of distributed adaptive controllers. Then based on the adaptive adjustment parameters and Lyapunov stability theory, Lyapunov functions are addressed to prove that the proposed adaptive master-slave large-scale system can be guaranteed to be asymptotic synchronization with the improper actuator and faulty transmitted signals. Finally, a multiple vehicle large-scale system is used to verify the efficiency of the method. 相似文献