全文获取类型
收费全文 | 36400篇 |
免费 | 4361篇 |
国内免费 | 2569篇 |
学科分类
工业技术 | 43330篇 |
出版年
2024年 | 132篇 |
2023年 | 736篇 |
2022年 | 1541篇 |
2021年 | 2020篇 |
2020年 | 1410篇 |
2019年 | 1071篇 |
2018年 | 1182篇 |
2017年 | 1218篇 |
2016年 | 1149篇 |
2015年 | 1727篇 |
2014年 | 2130篇 |
2013年 | 2501篇 |
2012年 | 3223篇 |
2011年 | 3136篇 |
2010年 | 2937篇 |
2009年 | 2763篇 |
2008年 | 2800篇 |
2007年 | 2723篇 |
2006年 | 2217篇 |
2005年 | 1748篇 |
2004年 | 1217篇 |
2003年 | 838篇 |
2002年 | 762篇 |
2001年 | 716篇 |
2000年 | 542篇 |
1999年 | 268篇 |
1998年 | 130篇 |
1997年 | 111篇 |
1996年 | 78篇 |
1995年 | 54篇 |
1994年 | 54篇 |
1993年 | 36篇 |
1992年 | 24篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1959年 | 7篇 |
1958年 | 1篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
1.
摘 要:核心网业务模型的建立是5G网络容量规划和网络建设的基础,通过现有方法得到的理论业务模型是静态不可变的且与实际网络存在偏离。为了克服现有5G核心网业务模型与现网模型适配性较差以及规划设备无法满足用户实际业务需求的问题,提出了一种长短期记忆(long short-term memory,LSTM)网络与卷积LSTM (convolution LSTM,ConvLSTM)网络双通道融合的 5G 核心网业务模型预测方法。该方法基于人工智能(artificial intelligence,AI)技术以实现高质量的核心网业务模型的智能预测,形成数据反馈闭环,实现网络自优化调整,助力网络智能化建设。 相似文献
3.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献
4.
5.
6.
Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films are attracting famous applications in antistatic coating, energy storage and conversion, printed electronics, and biomedical fields due to their conductivity, optical transparency and flexibility. However, PEDOT:PSS has poor dispersion stability during long-term storage and transport. Moreover, the dried PEDOT:PSS films are insoluble in any solvent and cannot be redispersed again. In comparison to bake drying, here, a feasible strategy to achieve mechanically redispersed PEDOT:PSS with the help of freeze-drying process was reported. The redispersed PEDOT:PSS can recover not only the initial characters such as pH, chemical composition, viscosity, and particle size under similar solid contents, but also conductivity and surface morphology of treated films. In addition, the treated film exhibits self-healing properties similar to pristine film in terms of mechanical and electrical properties. This technology enables reuse and overcomes the technical problems of PEDOT:PSS dispersion, realizing real-time processing to meet variable applications. 相似文献
7.
飞机从一个航段飞向下一个航段时,需要对下个航段是否激活进行判断.提出了一种新的飞行计划航段自动激活方法,通过获取飞机当前位置及其磁差,并结合临近的3个航路点对应位置的磁差经纬度,分别计算3个航路点与飞机位置对应的磁航向角,通过磁航向角之间做差进行比较,进而判断是否被激活.算法推导完成后,通过基于模型的系统工程工具SCADE SUITE进行了建模,并结合杰普逊航图进行了实际数据采样与仿真.仿真结果表明:该航段自动激活方法能够有效稳定地激活下一航段,比传统方法计算简便,方法实用有效.已在实际飞行中成功应用,达到了预期效果. 相似文献
8.
To advance organ-on-a-chip development and other areas befitting from physiologically-relevant biomembranes,a microfluidic platform is presented for synthesis of biomembranes during gelation and investigation into their role as extracellular matrix supports.In this work,high-throughput studies of collagen,chitosan,and collagen-chitosan hybrid biomembranes were carried out to characterize and compare key properties as a function of the applied hydrodynamic conditions during gelation.Specifically,depending on the biopolymer material used,varying flow conditions during biomembrane gelation caused width,uniformity,and swelling ratio to be differently affected and controllable.Finally,cell viability studies of seeded fibroblasts were conducted,thus showing the potential for biological applications. 相似文献
9.
Tao TIAN Chao-lan ZHANG Feng ZHU Shan-xin YUAN Ying GUO Sheng-guo XUE 《中国有色金属学会会刊》2021,31(5):1484-1495
A column experiment was conducted to investigate the effect of phosphogypsum (PG) on the saline- alkalinity, and aggregate stability of bauxite residue. Results showed that: with increasing leaching time, the concentrations of saline-alkali ions decreased while the concentration increased in bauxite residue leachate; compared with CK (control group) treatment, pH, electric conductivity (EC), exchangeable sodium percentage (ESP), sodium absorption ratio (SAR), and exchangeable Na+ content of bauxite residue were reduced following PG treatment; average particle sizes in aggregates following CK and PG treatments were determined to be 155 and 193 nm, respectively. SR-μCT test results also confirmed that bauxite residue following PG treatment acquired larger aggregates and larger pore diameter. These results indicate that the PG treatment could significantly modulate the saline-alkalinity, and simultaneously enhance aggregate stability of bauxite residue, which provides a facile approach to reclaim bauxite residue disposal areas. 相似文献
10.
Water Resources Management - Urban river not only has the important function in urban hydrological environment, but also is an area for entertainment. Water quality assessment is the core technique... 相似文献