全文获取类型
收费全文 | 21598篇 |
免费 | 2365篇 |
国内免费 | 1439篇 |
专业分类
电工技术 | 960篇 |
综合类 | 1370篇 |
化学工业 | 5888篇 |
金属工艺 | 1724篇 |
机械仪表 | 912篇 |
建筑科学 | 2199篇 |
矿业工程 | 418篇 |
能源动力 | 752篇 |
轻工业 | 1280篇 |
水利工程 | 345篇 |
石油天然气 | 440篇 |
武器工业 | 97篇 |
无线电 | 2351篇 |
一般工业技术 | 4324篇 |
冶金工业 | 805篇 |
原子能技术 | 1235篇 |
自动化技术 | 302篇 |
出版年
2024年 | 12篇 |
2023年 | 402篇 |
2022年 | 522篇 |
2021年 | 746篇 |
2020年 | 856篇 |
2019年 | 825篇 |
2018年 | 762篇 |
2017年 | 874篇 |
2016年 | 799篇 |
2015年 | 789篇 |
2014年 | 1190篇 |
2013年 | 1212篇 |
2012年 | 1558篇 |
2011年 | 1634篇 |
2010年 | 1107篇 |
2009年 | 1207篇 |
2008年 | 1054篇 |
2007年 | 1375篇 |
2006年 | 1282篇 |
2005年 | 1085篇 |
2004年 | 917篇 |
2003年 | 846篇 |
2002年 | 747篇 |
2001年 | 610篇 |
2000年 | 514篇 |
1999年 | 385篇 |
1998年 | 328篇 |
1997年 | 257篇 |
1996年 | 269篇 |
1995年 | 213篇 |
1994年 | 211篇 |
1993年 | 141篇 |
1992年 | 143篇 |
1991年 | 108篇 |
1990年 | 81篇 |
1989年 | 64篇 |
1988年 | 67篇 |
1987年 | 46篇 |
1986年 | 54篇 |
1985年 | 29篇 |
1984年 | 25篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Leucokinins (LKs) constitute a family of neuropeptides identified in numerous insects and many other invertebrates. LKs act on G-protein-coupled receptors that display only distant relations to other known receptors. In adult Drosophila, 26 neurons/neurosecretory cells of three main types express LK. The four brain interneurons are of two types, and these are implicated in several important functions in the fly’s behavior and physiology, including feeding, sleep–metabolism interactions, state-dependent memory formation, as well as modulation of gustatory sensitivity and nociception. The 22 neurosecretory cells (abdominal LK neurons, ABLKs) of the abdominal neuromeres co-express LK and a diuretic hormone (DH44), and together, these regulate water and ion homeostasis and associated stress as well as food intake. In Drosophila larvae, LK neurons modulate locomotion, escape responses and aspects of ecdysis behavior. A set of lateral neurosecretory cells, ALKs (anterior LK neurons), in the brain express LK in larvae, but inconsistently so in adults. These ALKs co-express three other neuropeptides and regulate water and ion homeostasis, feeding, and drinking, but the specific role of LK is not yet known. This review summarizes Drosophila data on embryonic lineages of LK neurons, functional roles of individual LK neuron types, interactions with other peptidergic systems, and orchestrating functions of LK. 相似文献
2.
Yunhai Zhang Yongsheng Liu Yejie Cao Liyang Cao Jing Wang Yu Pan Ning Wang 《Journal of the American Ceramic Society》2021,104(1):645-653
C/SiC composites prepared by chemical vapor infiltration technique (CVI) have been regarded as thermal structural materials widely. However, these composites still suffer from poor functional properties like low thermal conductivity, especially in thickness direction of the composites, limiting their large-scale applications. Herein, mesophase pitch based carbon fiber (MPCF) and continuous wave laser machining were utilized to construct highly effective heat conductive micro-pipelines within CVI C/SiC composite. The effect of initial density on the final density and thermal conductivity of the as-obtained MPCF-C/SiC composites were investigated. The results revealed that higher initial density would directly enhance the thermal conductivity and reduce the negative impact of the bottle-neck effect. At temperatures between 100°C and 500°C, MPCF-C/SiC composites preserved more than threefold of the thermal conductivity (340%) when compared to reference C/SiC composites. This work provides a highly effective route for enhancing the thermal conductivity of C/SiC, which would broaden their future applications. 相似文献
3.
为了解决醇胺法燃烧后捕集二氧化碳再生能耗过高的问题,研究了一种向胺溶液中添加金属离子以降低其CO2解吸能耗的方法,称之为金属离子络合物热缓冲自热利用技术。以广泛商业化应用的单乙醇胺(MEA)溶液为研究载体,并在MEA溶液中分别添加金属离子铜或镍, 通过建立含有金属离子的MEA捕集CO2体系的化学反应模型,解释金属离子热缓冲剂效应的内在机理。机理显示在MEA-金属离子-CO2-H2O体系中,金属-MEA络合物作为一种有效的反应热缓冲剂,将有机胺吸收CO2过程中释放的反应热(放热反应)存储于金属络合物的解离键能中(吸热反应),在CO2高温解吸中通过其络合放热反应将储存的能量释放出来用于CO2解吸,形成自热再生低能耗CO2捕集技术,从而降低了MEA再生的能耗。本文进行了综合的实验测定来评价金属离子对MEA溶液捕集CO2过程的性能提升影响,包括CO2反应热、解吸速率、吸收-解吸循环负载、汽液平衡溶解度等。实验结果表明铜离子或镍离子作为添加剂,能增加MEA的CO2平衡循环负载14%~20%或7%~10%,同时能够降低MEA的CO2反应热值6.6%~24%或6.0%~20%。 相似文献
4.
5.
Sergey Tkachev Miguel Monteiro João Santos Ernesto Placidi Mohamed Ben Hassine Pedro Marques Paulo Ferreira Pedro Alpuim Andrea Capasso 《Advanced functional materials》2021,31(33):2103287
Graphene-based materials have attracted significant attention in many technological fields, but scaling up graphene-based technologies still faces substantial challenges. High-throughput top-down methods generally require hazardous, toxic, and high-boiling-point solvents. Here, an efficient and inexpensive strategy is proposed to produce graphene dispersions by liquid-phase exfoliation (LPE) through a combination of shear-mixing (SM) and tip sonication (TS) techniques, yielding highly concentrated graphene inks compatible with spray coating. The quality of graphene flakes (e.g., lateral size and thickness) and their concentration in the dispersions are compared using different spectroscopic and microscopy techniques. Several approaches (individual SM and TS, and their combination) are tested in three solvents (N-methyl-2-pyrrolidone, dimethylformamide, and cyrene). Interestingly, the combination of SM and TS in cyrene yields high-quality graphene dispersions, overcoming the environmental issues linked to the other two solvents. Starting from the cyrene dispersion, a graphene-based ink is prepared to spray-coat flexible electrodes and assemble a touch screen prototype. The electrodes feature a low sheet resistance (290 Ω □−1) and high optical transmittance (78%), which provide the prototype with a high signal-to-noise ratio (14 dB) and multi-touch functionality (up to four simultaneous touches). These results illustrate a potential pathway toward the integration of LPE-graphene in commercial flexible electronics. 相似文献
6.
The damage induced in 3C-SiC epilayers on a silicon wafer by 2.3-MeV Si ion irradiation for fluences of 1014, 1015, and 1016 cm−2, was studied by conventional and high-resolution transmission electron microscopy (TEM/HRTEM). The evolution of extended defects and lattice disorder is followed in both the 3C-SiC film and Si substrate as a function of ion fluence, with reference to previous FTIR spectroscopy data. The likelihood of athermal unfaulting of native stacking faults by point defect migration to the native stacking faults is discussed in relation to damage recovery. Threshold energy densities and irradiation doses for dislocation loop formation and amorphous phase transformation are deduced from the damage depth profile by nuclear collisions. The role of electronic excitations on the damage recovery at high fluence is also addressed for both SiC and Si. 相似文献
7.
8.
9.
10.
Wei Zhang Chang Ma Ling-Zhi Huang Wen-Yan Guo Dan-Dan Li Jing Bian Ming-Guo Ma 《大分子材料与工程》2021,306(12):2100549
Conductive hydrogels have received widespread attention in the applications of biosensors, human–machine interface, and health recording electrodes. Herein, the conductive hydrogels integrated with antifreezing, water retention, reusable, and sensing performances are fabricated by introducing polyvinyl alcohol, cellulose nanofibril, MXene nanosheets, and glycerol. The as-prepared hydrogels present prominent electrical conductivity (2.58 mS cm−1) and flexibility even at −18 °C. In addition, the hydrogels have favorable water retention performance and can reuse after heating and cooling. When used as sensors, the hydrogels illustrate high sensitivity (gauge factor of 2.30), fast response time (0.165 s), wide working strain range (559%), favorable linearity (R2 = 0.999), and wide operating temperature range (−18 to 60 °C). The hydrogels can detect not only large strains of 10–200%, but also small strains of 1–5%, making them promising candidates for wearable sensors to monitor large and subtle movements. 相似文献