首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   289486篇
  免费   21485篇
  国内免费   11102篇
电工技术   15393篇
技术理论   31篇
综合类   17432篇
化学工业   50189篇
金属工艺   16876篇
机械仪表   18433篇
建筑科学   22865篇
矿业工程   9527篇
能源动力   7956篇
轻工业   16663篇
水利工程   4779篇
石油天然气   20256篇
武器工业   2234篇
无线电   31475篇
一般工业技术   34402篇
冶金工业   15266篇
原子能技术   2857篇
自动化技术   35439篇
  2024年   1217篇
  2023年   4677篇
  2022年   7918篇
  2021年   11470篇
  2020年   8528篇
  2019年   7275篇
  2018年   8170篇
  2017年   9218篇
  2016年   8024篇
  2015年   11169篇
  2014年   13769篇
  2013年   16444篇
  2012年   17752篇
  2011年   19396篇
  2010年   16749篇
  2009年   15902篇
  2008年   15441篇
  2007年   15083篇
  2006年   15975篇
  2005年   14151篇
  2004年   9049篇
  2003年   7904篇
  2002年   7305篇
  2001年   6485篇
  2000年   7097篇
  1999年   8498篇
  1998年   6846篇
  1997年   5821篇
  1996年   5450篇
  1995年   4509篇
  1994年   3757篇
  1993年   2628篇
  1992年   2136篇
  1991年   1601篇
  1990年   1173篇
  1989年   933篇
  1988年   759篇
  1987年   523篇
  1986年   389篇
  1985年   265篇
  1984年   183篇
  1983年   120篇
  1982年   130篇
  1981年   86篇
  1980年   70篇
  1979年   24篇
  1978年   2篇
  1965年   2篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
根据人工智能技术课程的教学情况,从教学内容、教学方法、教学案例、考核方式、培养实践能力五个方面探讨教学改革.提出在不断更新教学内容和"课堂讲授-课下辅导"模式的基础上,加强网络资源的利用,增加贯穿整个教学过程的分组报告,设计出提高创新能力的教学案例,开展具有多元考核方式以及循序渐进的动态实验设置模式的实践教学改革,以有...  相似文献   
992.
Cysteine oxidation states of extracellular proteins participate in functional regulation and in disease pathophysiology. In the most common inherited dementia, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), mutations in NOTCH3 that alter extracellular cysteine number have implicated NOTCH3 cysteine states as potential triggers of cerebral vascular smooth muscle cytopathology. In this report, we describe a novel property of the second EGF-like domain of NOTCH3: its capacity to alter the cysteine redox state of the NOTCH3 ectodomain. Synthetic peptides corresponding to this sequence (NOTCH3 N-terminal fragment 2, NTF2) readily reduce NOTCH3 N-terminal ectodomain polypeptides in a dose- and time-dependent fashion. Furthermore, NTF2 preferentially reduces regional domains of NOTCH3 with the highest intensity against EGF-like domains 12–15. This process requires cysteine residues of NTF2 and is also capable of targeting selected extracellular proteins that include TSP2 and CTSH. CADASIL mutations in NOTCH3 increase susceptibility to NTF2-facilitated reduction and to trans-reduction by NOTCH3 produced in cells. Moreover, NTF2 forms complexes with the NOTCH3 ectodomain, and cleaved NOTCH3 co-localizes with the NOTCH3 ectodomain in cerebral arteries of CADASIL patients. The potential for NTF2 to reduce vascular proteins and the enhanced preference for it to trans-reduce mutant NOTCH3 implicate a role for protein trans-reduction in cerebrovascular pathological states such as CADASIL.  相似文献   
993.
994.
995.
To enhance the red emission efficiency of Eu3+ complexes, [Eu/Tbx(BPA)3phen] (BPA?=?bisphenol A, phen?=?1,10-phenanthroline) is designed and synthesized. The complexes are characterized fully and their luminescence properties are evaluated. Co-fluorescence is detected in the Eu/Tbx(BPA)3phen complexes, and the existence of Tb3+ enhances the luminescence intensity of the central Eu3+ because of the intramolecular energy transfer from the 5D4 level of Tb3+ to the 5D0 level of Eu3+. The luminescence intensity of europium ions at 615?nm is the highest for Eu/Tb1(BPA)3phen. To improve the thermal stabilities and mechanical properties of pure complexes, Eu/Tb1(BPA)3phen/PAN (PAN?=?polyacrylonitrile) is used to fabricate fibres by electrospinning. Compared with Eu/Tb1(BPA)3phen (τ?=?1.1087?ms), the fibres have a longer fluorescence lifetime of 1.533?ms. The fibres also retain a high quantum yield of 47.16%. Thus, the flexible luminescent fibres have potential applications in many fields.  相似文献   
996.
纳米银抗菌材料研发现状   总被引:40,自引:0,他引:40  
介绍了纳米银抗菌材料的研究与开发现状 ,并叙述了纳米银的制备及其应用  相似文献   
997.
Droplet‐based microfluidics enable the production of emulsions and microparticles with spherical shapes, but the high‐throughput fabrication of nonspherical emulsions and microparticles still remains challenging because interfacial tension plays a dominant role during preparation. Herein, ionic liquids (ILs) containing salts, which possess sufficient osmotic pressure to realize water transport and phase separation, are introduced as inner cores of oil‐in‐oil‐in‐water double emulsions and it is shown that nonspherical emulsions can be constructed by osmosis‐driven arrested coalescence of inner cores. Subsequently, ultraviolet polymerization of the nonspherical emulsions leads to nonspherical microparticles. By tailoring the number, composition, and size of inner cores as well as coalescence time, a variety of nonspherical shapes such as dumbbell, rod, spindle, snowman, tumbler, three‐pointed star, triangle, and scalene triangle are created. Importantly, benefitting from excellent solvency of ILs, this system can serve as a general platform to produce nonspherical microparticles made from different materials. Moreover, by controlling the osmotic pressure, programmed coalescence of inner cores in double emulsions is realizable, which indicates the potential to build microreactors. Thus, a simple and high‐throughput strategy to create nonspherical microparticles with arrested coalescence shapes is developed for the first time and can be further used to construct novel materials and microreactors.  相似文献   
998.
制造企业基于Internet的设备远程诊断与维护系统研究   总被引:8,自引:0,他引:8  
介绍了一个用于汽车发动机自动生产线的远程监控与诊断系统的结构与功能,对系统实现的有关关键技术进行了探讨,并给出了运行实例。  相似文献   
999.
Nano-hydroxyapatite/chitosan/carboxymethyl cellulose (n-HA/CS/CMC) composites with weight ratios of 70/10/20, 70/15/15 and 70/20/10 were prepared through a co-solution method. The properties of the composites were characterized by means of burn-out test, IR, XRD, TEM and universal material testing machine. The degradation and bioactivity were also investigated by in vitro test in a simulated body fluid (SBF) for 8 weeks. The results showed that n-HA particles were dispersed uniformly in organic phase, and strong chemical interactions formed among the three phases. Moreover, the composites were similar to natural bone in morphology and size. In addition, the compressive strength was improved compared with n-HA/CS composite. The biodegradation rate was controllable by altering weight ratio of the CS/CMC. Meanwhile, the composites could induce apatite particles to deposit in SBF. All the above results indicate that the novel composites of n-HA/CS/CMC have a promising prospect used for bone repair materials in view of the good mechanical property, adjustable biodegradation rate and bioactivity in SBF. Additionally, the study would provide a good guide to exploit clinical application of natural cellulose.  相似文献   
1000.
Rapid, chip-scale, and cost-effective single particle detection of biological agents is of great importance to human health and national security. We report real-time, high-throughput detection and sizing of individual, low-index polystyrene nanoparticles and H1N1 virus. Our widefield, common path interferometer detects nanoparticles and viruses over a very large sensing area, orders of magnitude larger than competing techniques. We demonstrate nanoparticle detection and sizing down to 70 nm in diameter. We clearly size discriminate nanoparticles with diameters of 70, 100, 150, and 200 nm. We also demonstrate detection and size characterization of hundreds of individual H1N1 viruses in a single experiment.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号