全文获取类型
收费全文 | 481037篇 |
免费 | 7101篇 |
国内免费 | 2440篇 |
专业分类
电工技术 | 9794篇 |
技术理论 | 5篇 |
综合类 | 1492篇 |
化学工业 | 73764篇 |
金属工艺 | 19476篇 |
机械仪表 | 14970篇 |
建筑科学 | 11963篇 |
矿业工程 | 2621篇 |
能源动力 | 11302篇 |
轻工业 | 43620篇 |
水利工程 | 5058篇 |
石油天然气 | 9099篇 |
武器工业 | 311篇 |
无线电 | 56975篇 |
一般工业技术 | 91061篇 |
冶金工业 | 87707篇 |
原子能技术 | 9863篇 |
自动化技术 | 41497篇 |
出版年
2021年 | 4222篇 |
2019年 | 3846篇 |
2018年 | 6318篇 |
2017年 | 6356篇 |
2016年 | 6819篇 |
2015年 | 4845篇 |
2014年 | 8004篇 |
2013年 | 21112篇 |
2012年 | 13194篇 |
2011年 | 17642篇 |
2010年 | 14108篇 |
2009年 | 15396篇 |
2008年 | 16716篇 |
2007年 | 16831篇 |
2006年 | 15035篇 |
2005年 | 13349篇 |
2004年 | 12397篇 |
2003年 | 11882篇 |
2002年 | 11549篇 |
2001年 | 11649篇 |
2000年 | 11043篇 |
1999年 | 11119篇 |
1998年 | 25136篇 |
1997年 | 18348篇 |
1996年 | 14304篇 |
1995年 | 10993篇 |
1994年 | 9896篇 |
1993年 | 9730篇 |
1992年 | 7744篇 |
1991年 | 7212篇 |
1990年 | 7162篇 |
1989年 | 6852篇 |
1988年 | 6529篇 |
1987年 | 5707篇 |
1986年 | 5604篇 |
1985年 | 6500篇 |
1984年 | 6140篇 |
1983年 | 5638篇 |
1982年 | 5130篇 |
1981年 | 5424篇 |
1980年 | 5042篇 |
1979年 | 5066篇 |
1978年 | 4842篇 |
1977年 | 5385篇 |
1976年 | 6799篇 |
1975年 | 4391篇 |
1974年 | 4239篇 |
1973年 | 4290篇 |
1972年 | 3541篇 |
1971年 | 3270篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
L Peperzak 《Water science and technology》2005,51(5):31-36
In temperate seas such as the North Sea harmful (toxic) algal blooms will probably increase as a result of climate change. This conclusion was reached after investigating the projected effect of climate change for the year 2100 in Dutch coastal waters (4 degrees C temperature rise and increased water column stratification) on the growth rates of six harmful and two non-harmful phytoplankton species. Micro algae form the basis of the marine food chain. However, toxin-producing species may seriously disrupt the food web and lead to fish kills and human intoxication. Two species with estimated doubled growth rates in 2100, F. japonica and C. antiqua, entered Europe via ship's ballast water or shellfish imports. This stresses the need to legally regulate such invasion routes in order to prevent the import of novel species. Future toxic phytoplankton blooms may further devaluate ecosystem deliverables such as fish production or recreational use. This devaluation can be estimated by monetary value assessments that are needed in cost-benefit analyses for policy guidance. The lack of understanding of future climate, ecosystem functioning and its response to climate change calls for a scientific effort to improve our knowledge on present day coastal ecosystem functioning and its resilience. 相似文献
102.
103.
I. Revilla & M. L. González-San José 《International Journal of Food Science & Technology》2003,38(1):29-36
Summary The effect of the addition of four commercial pectolytic preparations on the visual characteristics (colour and turbidity) of red wines has been evaluated. The effect of both clarifying and colour extracting enzymes and the effect of different doses used, were evaluated and compared. All the red wines treated enzymatically, independent of the type of enzyme and dose, present chromatic characteristics which can be considered better than those of the control wines. Also, those wines treated with enzymes had greater stability during 2 years storage in bottles, in particular the turbidity was better than untreated wines. 相似文献
104.
This paper deals with accurate recipe implementation for abnormal condition management in a batch process using a case‐based reasoning (CBR) approach. A set of new problems can be solved by reusing proven process solutions. The proposed system integrates quantitative and qualitative parameters for adaptation of cases. A novel methodology to generate accurate recipes and to adapt to the processes is introduced during normal and abnormal conditions. In particular, the differences between current conditions and the references (recipes) should be managed to prevent any hazardous conditions arising. The processes are evaluated using their similarity to the past cases. This intelligent approach distinguishes plausible cases, generates accurate recipes, and adapts to new situations. The aim is to use the offline historical process data and safety related information in order to propose changes and adjustments in the processes. 相似文献
105.
The miscibility and phase behavior of ternary blends containing dimethylpolycarbonate (DMPC), tetramethylpolycarbonate (TMPC) and poly[styrene‐co‐(methyl methacrylate)] copolymer (SMMA) have been explored. Ternary blends containing polystyrene (PS) instead of SMMA were also examined. Blends of DMPC with SMMA copolymers (or PS) did not form miscible blends regardless of methyl methacrylate (MMA) content in copolymers. However, DMPC blends with SMMA (or PS) blends become miscible by adding TMPC. The miscible region of ternary blends is compared with the previously determined miscibility region of binary blends having the same chemical components and compositions. The region where the ternary blends are miscible is much narrower than that of binary blends. Based on lattice fluid theory, the observed phase behavior of ternary blends was analyzed. Even though the term representing the Gibbs free energy change of mixing for certain ternary blends had a negative value, blends were immiscible. It was revealed that a negative value of the Gibbs free energy change of mixing was not a sufficient condition for miscible ternary blends because of the asymmetry in the binary interactions involved in ternary blends. Copyright © 2004 Society of Chemical Industry 相似文献
106.
107.
108.
109.
110.