全文获取类型
收费全文 | 46369篇 |
免费 | 4022篇 |
国内免费 | 1842篇 |
专业分类
电工技术 | 1017篇 |
综合类 | 2444篇 |
化学工业 | 18202篇 |
金属工艺 | 1387篇 |
机械仪表 | 1730篇 |
建筑科学 | 1898篇 |
矿业工程 | 571篇 |
能源动力 | 3534篇 |
轻工业 | 7774篇 |
水利工程 | 320篇 |
石油天然气 | 2213篇 |
武器工业 | 225篇 |
无线电 | 2136篇 |
一般工业技术 | 5685篇 |
冶金工业 | 1194篇 |
原子能技术 | 744篇 |
自动化技术 | 1159篇 |
出版年
2024年 | 208篇 |
2023年 | 853篇 |
2022年 | 1390篇 |
2021年 | 1874篇 |
2020年 | 1804篇 |
2019年 | 1787篇 |
2018年 | 1477篇 |
2017年 | 1683篇 |
2016年 | 1695篇 |
2015年 | 1611篇 |
2014年 | 2558篇 |
2013年 | 2868篇 |
2012年 | 3334篇 |
2011年 | 3316篇 |
2010年 | 2449篇 |
2009年 | 2411篇 |
2008年 | 2080篇 |
2007年 | 2726篇 |
2006年 | 2342篇 |
2005年 | 2112篇 |
2004年 | 1753篇 |
2003年 | 1609篇 |
2002年 | 1293篇 |
2001年 | 1147篇 |
2000年 | 1029篇 |
1999年 | 911篇 |
1998年 | 740篇 |
1997年 | 622篇 |
1996年 | 469篇 |
1995年 | 408篇 |
1994年 | 324篇 |
1993年 | 308篇 |
1992年 | 251篇 |
1991年 | 158篇 |
1990年 | 119篇 |
1989年 | 76篇 |
1988年 | 80篇 |
1987年 | 50篇 |
1986年 | 44篇 |
1985年 | 53篇 |
1984年 | 49篇 |
1983年 | 33篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1959年 | 3篇 |
1951年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
31.
采用Nova-Pak C18不锈钢色谱柱进行反相液相色谱分析,以甲醇:水=65:35(V/V)为注动相,以邻苯二甲醇二乙酯为内标物,用内标法测定田草灵除草剂中苄嘧黄隆和异丙甲草胺的含量,结果表明,各有效成分与内标物色谱峰分离完全,杂质无干扰,测定结果,苄嘧黄隆和异丙甲草胺的变异系数分别为0.74%和1.07%,回收率分别为99.4% ̄100.8%和99.1% ̄101.3%。 相似文献
32.
本文由无限稀释活度系数求取混合物MH-81状态方程的二元相互作用参数,预测了二元混合物的汽液平衡,获得了较满意的结果。 相似文献
33.
This paper presents a mathematical model based on the reaction rate expressions to describe the displacement of methane conversion in the steam reforming. The effect of several parameters including weight hourly space velocity (WHSV), load-to-surface ratio, reaction pressure, hydrogen partial pressure in permeate side and reaction temperature were investigated. Simulation and experimental results showed that a conversion higher than 80% could be achieved in a palladium membrane reactor at reaction temperature of 500 °C relative to 850 °C in a conventional fixed bed reactor (FBR). Besides, the yield of CO (<2%) in membrane reactor was much lower than that (>50%) in the FBR, which indicated the significant depression of CO production in use of membrane reactor. 相似文献
34.
V.V. Zyryanov N.F. Uvarov V.A. Sadykov Y.V. Frolova G.M. Alikina A.I. Lukashevich M.I. Ivanovskaya J.M. Criado S. Neophytides 《Catalysis Today》2005,104(2-4):114-119
Nanopowders of LaGaO3- and LaMnO3-based complex perovskites (P) and ceria-based fluorites (F) were prepared by mechanosynthesis. Compatible nanocomposites F + P and P + P with mixed ion and electron conducting (MIEC) properties were prepared and sintered at moderate temperatures up to dense ceramics. The obtained materials were studied by means of XRD, SEM, TEM, electrical conductivity measurements, temperature programmed (TP) reduction/oxidation and preliminary estimations of permeability were obtained. A new strategy based on the advantages of the mechanochemical ceramic approach is proposed to design multilayer ceramic membranes for CMR. Casting technology and one-step sintering were used for the production of thin film membranes with MIEC properties on porous substrates. The coarse fraction of as-milled powders from agglomerates with density 70% was used for the porous substrate, and fine fractions of aggregates with sizes <1 μm were used in preparation of composites for thin dense films. Ceria-based composites prepared by the Pechini route and/or mechanochemical method are proposed as materials for protecting thin films. 相似文献
35.
Changes in the liquid hold-up, ?, and the diameter of d, of a foam that are induced by perforated plates (PPs) and the contribution of PPs to foam-breaking were studied. A foaming system containing a dilute detergent solution in a column with mechanical agitation fitted with a rotating-disk foam-breaker (MFRD) was used. After the foam passed through the PPs, ? and d decreased and increased, respectively. The use of PPs to achieve a maximum reduction in ? and a maximum increase in d is confirmed. It is also demonstrated that use of PPs contributes not only to improving the foam-breaking performance of the MFRD, but also to power savings. 相似文献
36.
钯-银合金膜分离氢气的研究 总被引:1,自引:0,他引:1
采用厚为50μm的Pd/Ag(23)合金膜进行了氢气渗透系数的测定和H_2/N_2混和气分离的研究,得出温度、压力、膜厚、进料气流量、膜的预处理和再活化及膜表面中毒等因素对氢气渗透的影响。分离H_2/N_2混和气可获得高纯氢气。 相似文献
37.
Efficient and selective oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones catalyzed by potassium permanganate supported on Kieselguhr reagent under solvent free conditions are reported. 相似文献
38.
邵林 《安徽冶金科技职业学院学报》2017,27(1)
为了能够准确地测量污水旋流池的液面高度,设计了基于超声传感技术的污水旋流池液面测量方法,通过长时间的运行,测量数据完全满足污水旋流池的生产工艺要求。 相似文献
39.
Poly (vinyl butyral) (PVB) hollow fiber membranes were fabricated via thermally induced phase separation (TIPS). The effects of coagulation bath temperature (CBT) on the structure and performance of membranes were investigated in detail. The morphologies of the membranes were studied by scanning electron microscopy (SEM), the performances of water permeability, rejection, breaking strength and elongation were measured, respectively. The results indicate that all the membranes have the asymmetric morphology and the thickness of the skin layer decreases and the pore size of the outer layer increases with the increase of CBT. The permeability of membranes prepared at air gap 1.0 cm and take-up speed 0.253 m/s increases from 1.047×10-7 to 5.909×10-7 m3/(m2·s-kPa) with the CBT increasing from 20 ℃ to 40℃, and sharply increases to 35.226×10 7 m3/(m2.s.kPa)once the CBT arrives at 50 ℃. While the carbonic ink rejections have no significant decrease, totally exceed 98%, but that of acid-maleic acid copolymer greatly decreases with the increase of CBT. Both the breaking strength and elongation decrease with the increase of CBT. 相似文献
40.
采用高效液相色谱技术,开展了Fenton试剂对2-(4-氯苯氨基)甲基苯酚(CMP)的氧化降解动力学的研究。考察了初始双氧水摩尔浓度、亚铁离子摩尔浓度和温度等因素对CMP降解速率的影响,结果表明,当双氧水摩尔浓度、亚铁离子摩尔浓度增大和温度升高时,CMP的氧化速率明显加快。在30~45℃的温度范围内,其氧化降解符合假一级反应动力学模型,反应的表观活化能Ea为102.90kJ/mol。 相似文献