全文获取类型
收费全文 | 6177篇 |
免费 | 535篇 |
国内免费 | 296篇 |
专业分类
电工技术 | 305篇 |
综合类 | 447篇 |
化学工业 | 1174篇 |
金属工艺 | 428篇 |
机械仪表 | 392篇 |
建筑科学 | 464篇 |
矿业工程 | 151篇 |
能源动力 | 88篇 |
轻工业 | 603篇 |
水利工程 | 117篇 |
石油天然气 | 317篇 |
武器工业 | 65篇 |
无线电 | 610篇 |
一般工业技术 | 630篇 |
冶金工业 | 297篇 |
原子能技术 | 135篇 |
自动化技术 | 785篇 |
出版年
2024年 | 17篇 |
2023年 | 86篇 |
2022年 | 209篇 |
2021年 | 282篇 |
2020年 | 223篇 |
2019年 | 165篇 |
2018年 | 181篇 |
2017年 | 193篇 |
2016年 | 179篇 |
2015年 | 270篇 |
2014年 | 339篇 |
2013年 | 435篇 |
2012年 | 512篇 |
2011年 | 477篇 |
2010年 | 441篇 |
2009年 | 398篇 |
2008年 | 363篇 |
2007年 | 335篇 |
2006年 | 336篇 |
2005年 | 274篇 |
2004年 | 193篇 |
2003年 | 141篇 |
2002年 | 118篇 |
2001年 | 141篇 |
2000年 | 113篇 |
1999年 | 111篇 |
1998年 | 89篇 |
1997年 | 74篇 |
1996年 | 66篇 |
1995年 | 48篇 |
1994年 | 49篇 |
1993年 | 37篇 |
1992年 | 24篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1980年 | 6篇 |
1978年 | 1篇 |
1976年 | 4篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7008条查询结果,搜索用时 31 毫秒
1.
Xiao-Mei Sha Li-Jun Zhang Wen-Mei Chen Guang-Yao Wang Jin-Lin Li Zi-Zi Hu Zong-Cai Tu 《International Journal of Food Science & Technology》2022,57(3):1573-1586
Thermal action in extraction process had effects on characteristic tryptic peptides identification and gelling properties of porcine gelatin. SDS-PAGE, HPLC-LTQ/Orbitrap high-resolution mass spectrometry, texture analyser and rheometer were used to evaluate collagen depolymerisation degree, characteristic tryptic peptides and gelling properties of gelatins prepared in various thermal actions. Results showed that with increasing temperature and time, depolymerisation degree enlarged, while gel strength, gelling and melting temperature decreased. Mass spectra showed that 47 and 49 common characteristic tryptic peptides were identified in gelatins extracted at 50 °C and 100 °C with various times, respectively. Moreover, 34 common characteristic tryptic peptides were identified in all gelatin samples. Further comparison between this work and our previous investigations yielded 20 common characteristic tryptic peptides, which stably exist in various thermal actions. These common characteristic tryptic peptides may be very helpful for the accurate authentication of porcine gelatin. 相似文献
3.
The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system. 相似文献
4.
In this paper, we consider the problem of designing optimal asynchronous wake-up schedules to facilitate distributed power management and neighbor discovery in multihop wireless networks. We first formulate it as a block design problem and derive the fundamental trade-offs between wake-up latency and the average duty cycle of a node. After the theoretical foundation is laid, we then devise a neighbor discovery and schedule bookkeeping protocol that can operate on the optimal wake-up schedule derived. To demonstrate the usefulness of asynchronous wake-up, we investigate the efficiency of neighbor discovery and the application of on-demand power management, which overlays a desirable communication schedule over the wake-up schedule mandated by the asynchronous wake-up mechanism. Simulation studies demonstrate that the proposed asynchronous wake-up protocol has short discovery time which scales with the density of the network; it can accommodate various traffic characteristics and loads to achieve an energy savings that can be as high as 70 percent, while the packet delivery ratio is comparable to that without power management. 相似文献
5.
地理信息系统的应用越来越广泛,特别是基于网络的GIS的发展使地理空间信息通过网络被多用户所共享,因此必须考虑地理数据访问的安全性。文章以MapInfoSpatailWare空间数据引擎为研究对象,给出了基于此模式的数据访问安全性解决方案。 相似文献
6.
Fastmet工艺评述 总被引:5,自引:0,他引:5
介绍了Fastmet工艺及发展状况,并对工艺特点和指标进行了分析。使用冷固结含碳球团和转底炉使该工艺可直接采用粉矿和提高生产效率,但因硫含量高、铁品位低而产品质量较差。不过投资和生产成本与传统工艺比较却占有较大优势。 相似文献
7.
A high‐melt‐strength polypropylene (HMSPP) was prepared using a twin‐screw reactive extruder from a commercial isotactic polypropylene through two stages, first, maleic anhydride is grafted to polypropylene to obtain a maleic anhydride‐grafted polypropylene (PP‐g‐MA), and then the grafted polymer is reacted with epoxy to extend the branched chain. Fourier transformed infrared spectroscopy indicated that maleic anhydride was grafted on polypropylene and reacted with epoxy. Melt flow rate and sag resistance test showed that the melt strength of the HMSPP improved considerably. Differential scanning calorimetry test showed that the long chain branches (LCBs) act as a nucleating agent in the crystallization of the HMSPP, which leads to a high crystallization temperature and crystallinity. Furthermore, the LCB efficiency of the HMSPP can also be calculated by analyzing its rheological property. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
8.
CHING-HUA Su YI-GAO Sha S. L Lehoczky F. R Szofran D. C Gillies S. D Cobb R. N Scripa 《Journal of Materials Science》1997,32(14):3765-3768
A series of Hg0.84Zn0.16 Te crystal ingots have been grown from pseudobinary melts by the Bridgmam–Stockbarger type directional solidification using
a Marshall Space Flight Center/Space Science Laboratory heat-pipe furnace and the ground control experiment laboratory furnace
of the crystal growth furnace which was flown on the first United States Microgravity Mission. A number of translation rates
and a series of hot- and cold-zone temperatures were employed to assess the influence of growth parameters on the crystal
properties for the purpose of optimizing the in-flight growth conditions.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
9.
WANG Si-Xue WANG Yu-Gang XUE Jian-Ming LIU Feng DU Guang-hua LU Gang YAN Sha ZHAO Wei-Jiang 《核技术(英文版)》2002,13(1):31-36
1 INTRODUCTIONThe new aPplications of low energy heavy ion beam in irradi4ted botanical materialswere studied in recellt yeaxs. The beaminduced mutation effect on crop seeds has causedthe attention of physicist and biologists.[1l:] FOr examPle, 1ow energy ions can induceremarkable mutation to rice seeds.[3] There are many special phenomena when heavyions bombard botanic sW1e due to its special structure. Some studies showed that tllepenetration depths of some ions were far larger than t… 相似文献
10.
Sha Lu Yong Hu O'Hara M. Bogy D.B. Singh Bhatia C. Yiao-Tee Hsia 《IEEE transactions on magnetics》1996,32(1):103-109
Three sub-25 nm fly height sliders are presented for near contact recording. The designs are geared towards the goal of achieving 10 Gb/in 2 areal density. The optimization procedure presented shows promise for facilitating achievement of this goal. The dynamic simulations show the stability of these designs when disturbed from their steady state conditions 相似文献