全文获取类型
收费全文 | 427507篇 |
免费 | 19960篇 |
国内免费 | 9350篇 |
专业分类
电工技术 | 15671篇 |
技术理论 | 13篇 |
综合类 | 11840篇 |
化学工业 | 65986篇 |
金属工艺 | 17867篇 |
机械仪表 | 18399篇 |
建筑科学 | 20390篇 |
矿业工程 | 5968篇 |
能源动力 | 12429篇 |
轻工业 | 40925篇 |
水利工程 | 5372篇 |
石油天然气 | 12530篇 |
武器工业 | 1408篇 |
无线电 | 54289篇 |
一般工业技术 | 66788篇 |
冶金工业 | 54963篇 |
原子能技术 | 5246篇 |
自动化技术 | 46733篇 |
出版年
2023年 | 3914篇 |
2022年 | 7336篇 |
2021年 | 10242篇 |
2020年 | 7706篇 |
2019年 | 6683篇 |
2018年 | 8219篇 |
2017年 | 8943篇 |
2016年 | 8508篇 |
2015年 | 9689篇 |
2014年 | 12979篇 |
2013年 | 23034篇 |
2012年 | 18828篇 |
2011年 | 22311篇 |
2010年 | 18307篇 |
2009年 | 18599篇 |
2008年 | 18635篇 |
2007年 | 17852篇 |
2006年 | 17408篇 |
2005年 | 15286篇 |
2004年 | 12391篇 |
2003年 | 11443篇 |
2002年 | 10506篇 |
2001年 | 10511篇 |
2000年 | 9763篇 |
1999年 | 10885篇 |
1998年 | 19710篇 |
1997年 | 14218篇 |
1996年 | 11246篇 |
1995年 | 8698篇 |
1994年 | 7472篇 |
1993年 | 6817篇 |
1992年 | 4999篇 |
1991年 | 4532篇 |
1990年 | 4092篇 |
1989年 | 3814篇 |
1988年 | 3623篇 |
1987年 | 2827篇 |
1986年 | 2688篇 |
1985年 | 3271篇 |
1984年 | 2901篇 |
1983年 | 2638篇 |
1982年 | 2426篇 |
1981年 | 2451篇 |
1980年 | 2256篇 |
1979年 | 2071篇 |
1978年 | 1902篇 |
1977年 | 2194篇 |
1976年 | 2745篇 |
1975年 | 1595篇 |
1973年 | 1564篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文
2.
Norfariza Jamaluddin David C. Stuckey Arbakariya B. Ariff 《Critical reviews in food science and nutrition》2018,58(14):2453-2465
ABSTRACTBacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted. 相似文献
3.
Networks and Spatial Economics - The relationship between shipping accessibility and maritime transport demand is studied based on the relationship between production and consumption and stochastic... 相似文献
4.
World Wide Web - The wide spread use of positioning and photographing devices gives rise to a deluge of traffic trajectory data (e.g., vehicle passage records and taxi trajectory data), with each... 相似文献
5.
6.
7.
8.
9.
A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI3. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling. 相似文献
10.
大型综合室内亲子乐园属于高大空间,设有游乐设施和游戏的特殊性使得对空间的舒适性要求一致,但是送风气流遇阻严重,室内存在较多气流死角,影响室内空气质量和儿童健康。因此其空调设计不仅需要考虑温度、风速的空间均匀度,还要考虑各点的空气龄和PMV-PPD指标。以天津某亲子乐园为研究对象,利用scSTREAM软件对适用于该房间的辐射供冷加新风、置换通风、混合通风三种空调方式的送风效果进行数值模拟分析,从流场的均匀性、人员的热舒适性等方面对模拟结果进行探讨,研究结果表明辐射供冷加新风方式的空间均匀性和PMV指标最佳,混合通风方式的空气龄最小。 相似文献