全文获取类型
收费全文 | 14485篇 |
免费 | 1128篇 |
国内免费 | 604篇 |
专业分类
电工技术 | 853篇 |
综合类 | 754篇 |
化学工业 | 2499篇 |
金属工艺 | 816篇 |
机械仪表 | 910篇 |
建筑科学 | 955篇 |
矿业工程 | 366篇 |
能源动力 | 439篇 |
轻工业 | 811篇 |
水利工程 | 199篇 |
石油天然气 | 960篇 |
武器工业 | 88篇 |
无线电 | 1989篇 |
一般工业技术 | 1898篇 |
冶金工业 | 698篇 |
原子能技术 | 117篇 |
自动化技术 | 1865篇 |
出版年
2024年 | 52篇 |
2023年 | 247篇 |
2022年 | 422篇 |
2021年 | 597篇 |
2020年 | 389篇 |
2019年 | 331篇 |
2018年 | 393篇 |
2017年 | 434篇 |
2016年 | 405篇 |
2015年 | 564篇 |
2014年 | 753篇 |
2013年 | 901篇 |
2012年 | 876篇 |
2011年 | 1019篇 |
2010年 | 842篇 |
2009年 | 814篇 |
2008年 | 844篇 |
2007年 | 753篇 |
2006年 | 802篇 |
2005年 | 705篇 |
2004年 | 461篇 |
2003年 | 394篇 |
2002年 | 321篇 |
2001年 | 297篇 |
2000年 | 302篇 |
1999年 | 433篇 |
1998年 | 375篇 |
1997年 | 288篇 |
1996年 | 280篇 |
1995年 | 196篇 |
1994年 | 185篇 |
1993年 | 120篇 |
1992年 | 107篇 |
1991年 | 70篇 |
1990年 | 60篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 9篇 |
1986年 | 23篇 |
1985年 | 6篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
无机磷与钼酸能形成磷钼酸络合物,该络合物能被还原剂α-1,2,4-氨基萘酚磺酸钠还原成钼蓝,用分光光度计确定蔗糖发酵前后无机磷的含量,观察发酵过程中无机磷的消耗。发现高浓度的磷酸盐会对微生物合成具有抑制和阻遏作用,无机磷含量的减少使葡萄糖磷酸化减慢,进而也影响糖酵解速度。研究表明在pH为6、温度为37℃、无机磷浓度为5g/L左右,发酵最佳。 相似文献
52.
53.
54.
55.
<正>都江堰虹口距成都市约80km,因避暑及漂流而成为成都的旅游胜地,生态旅游中心选址于虹口风景区深溪沟。项目分两期,一期为深溪沟接待点,由香溪行馆(别墅区)和香溪堂(服务配套建筑,190m~2)组成,二期为虹口旅游服务中心及酒店。香溪堂作为接待、休闲之用,规模很小,功能简单,但业主极为重视,把它作为二期启动前的形象展示,希望设计理念先进,独具个性。业主于2007年10月正式委托我们设计一期工程,原计划2008年6月动工。5月12日突如其来的汶川大地 相似文献
56.
In project management, a project can be represented as a network in two ways; namely, activity-on-arc (AoA) and activity-on-node (AoN). Two recent papers have shown that ant colony optimization (ACO) could find critical path(s) in projects represented as AoA networks. This paper points out that the number and placement of logical dummy activities associated with AoA-based networks can pose serious problems. To get around the problems, an ACO technique based on AoN networks is then proposed. For comparison, the two existing AoA-based ACO algorithms were reproduced and modified into AoN-based algorithms. Moreover, the proposed ACO algorithm was applied to AoA networks as well. All six algorithms were tested with several benchmark problems. The test results strongly indicate that AoN-based ACO algorithms are more effective and efficient in finding critical paths than AoA-based algorithms. 相似文献
57.
Flexible and Highly Sensitive Strain Sensors Fabricated by Pencil Drawn for Wearable Monitor 下载免费PDF全文
Xinqin Liao Qingliang Liao Xiaoqin Yan Qijie Liang Haonan Si Minghua Li Hualin Wu Shiyao Cao Yue Zhang 《Advanced functional materials》2015,25(16):2395-2401
Functional electrical devices have promising potentials in structural health monitoring system, human‐friendly wearable interactive system, smart robotics, and even future multifunctional intelligent room. Here, a low‐cost fabrication strategy to efficiently construct highly sensitive graphite‐based strain sensors by pencil‐trace drawn on flexible printing papers is reported. The strain sensors can be operated at only two batteries voltage of 3 V, and can be applied to variously monitoring microstructural changes and human motions with fast response/relaxation times of 110 ms, a high gauge factor (GF) of 536.6, and high stability >10 000 bending–unbending cycles. Through investigation of service behaviors of the sensors, it is found that the microcracks occur on the surface of the pencil‐trace and have a major influence on the functions of the strain sensors. These performances of the strain sensor attain and even surpass the properties of recent strain sensing devices with subtle design of materials and device architectures. The pen‐on‐paper (PoP) approach may further develop portable, environmentally friendly, and economical lab‐on‐paper applications and offer a valuable method to fabricate other multifunctional devices. 相似文献
58.
相控阵机载雷达杂波抑制的时—空二维自适应滤波 总被引:22,自引:15,他引:22
本文提出了一种机载预警侧面相控阵雷达抑制地杂波的时-空二维自适应方法,该方法先对各列子阵的数据作多通道的多卜勒滤波,然后分别对相同多卜勒滤波器输出的数据作Capon自适应处理。理论分析和计算机模拟结果表明,本文方法的杂波抑制性能在天线阵元存在一定的随机幅度和相位误差情况下损失不大,对阵元失效也不敏感。 相似文献
59.
60.
Qiaomu Wang Kaifei Tang Qiaobo Liao Yang Xu Haocheng Xu Yandong Wang Peng Wang Zhen Meng Kai Xi 《Advanced functional materials》2023,33(6):2211356
Covalent organic frameworks (COFs) with various topologies are typically synthesized by selecting and designing connecting units with rich shapes. However, this process is time-consuming and labour-intensive. Besides, the tight stacking of COFs layers greatly restrict their structural advantages. It is crucial to effectively exploit the high porosity and active sites of COFs by topological design. Herein, for the first time, inducing in situ topological changes in sub-chemometric COFs by adding graphene oxide (GO) without replacing the monomer, is proposed. Surprisingly, GO can slow down the intermolecular stacking and induce rearrangement of COFs nanosheets. The channels of D- [4+3] COFs are significantly altered while the stacking of periodically expanded framework is weakened. This not only maximizes the exposure of pore area and polar groups, but also shortens the channels and increases the redox activity, which enables high loading while enhancing host-guest interactions. This topological transformation to exhibit the structural features of COFs for efficient application is an innovative molecular design strategy. 相似文献