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   33353篇
  免费   2829篇
  国内免费   1039篇
电工技术   1648篇
技术理论   1篇
综合类   1567篇
化学工业   6182篇
金属工艺   1758篇
机械仪表   1736篇
建筑科学   2334篇
矿业工程   813篇
能源动力   1039篇
轻工业   2916篇
水利工程   531篇
石油天然气   1316篇
武器工业   208篇
无线电   3382篇
一般工业技术   5054篇
冶金工业   1427篇
原子能技术   447篇
自动化技术   4862篇
  2024年   154篇
  2023年   582篇
  2022年   929篇
  2021年   1385篇
  2020年   1112篇
  2019年   928篇
  2018年   1082篇
  2017年   1264篇
  2016年   1153篇
  2015年   1324篇
  2014年   1650篇
  2013年   2306篇
  2012年   2094篇
  2011年   2361篇
  2010年   1946篇
  2009年   1773篇
  2008年   1629篇
  2007年   1510篇
  2006年   1399篇
  2005年   1381篇
  2004年   869篇
  2003年   788篇
  2002年   733篇
  2001年   608篇
  2000年   625篇
  1999年   702篇
  1998年   684篇
  1997年   547篇
  1996年   580篇
  1995年   471篇
  1994年   404篇
  1993年   322篇
  1992年   254篇
  1991年   211篇
  1990年   161篇
  1989年   142篇
  1988年   126篇
  1987年   83篇
  1986年   69篇
  1985年   85篇
  1984年   94篇
  1983年   68篇
  1982年   60篇
  1981年   81篇
  1980年   67篇
  1979年   60篇
  1978年   47篇
  1977年   39篇
  1976年   56篇
  1973年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
The fission yeast Schizosaccharomyces pombe is an important model organism for the study of fundamental questions in eukaryotic cell and molecular biology. A plethora of cellular processes are membrane associated and/or dependent on the proper functioning of cellular membranes. Phospholipids are not only the basic building blocks of cellular membranes; they also serve as precursors to numerous signaling molecules. In this review, we describe the biosynthetic pathways leading to major S. pombe phospholipids, how these pathways are regulated, and what is known about degradation and turnover of fission yeast phospholipids. This review also addresses the synthesis, regulation and the role of water-soluble phospholipid precursors. The last chapter of the review is devoted to the use of S. pombe for the biotechnological production of value-added lipid molecules.  相似文献   
43.
Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications.  相似文献   
44.
JOM - The Isa/Ausmelt smelting technology with a top submerged lance (TSL) has been extensively used in copper smelting processes. However, the TSL is extremely vulnerable to damage and failure...  相似文献   
45.
46.
The paper analyses the corrosion behaviour of naturally and artificially aged AA2024 alloy in NaCl solution and in the presence of an environment-friendly corrosion inhibitor, CeCl3. On the basis of the values of polarisation resistance and corrosion current density, the corrosion resistance of the protective inhibitor film is established as well as the general corrosion resistance of this aluminium alloy. Resistance to pit formation is determined based on the difference in pitting and corrosion potentials while resistance to pit growth is determined based on the amount of charge consumed during pit growth. A scanning electron microscope is used to examine the morphology of the pits formed during the pitting corrosion testing, as well as to determine the cerium content on intermetallic particles and the matrix AA2024 alloy. The corrosion behaviour of AA2024 alloy is investigated after different test periods in NaCl solution and in the same solution with the CeCl3 inhibitor. The corrosion resistance of both tempers of AA2024 alloy is more than one order of magnitude higher in the presence of CeCl3. An explanation of the observed differences in the corrosion behaviour of the naturally and artificially aged AA2024 alloy is proposed. Different corrosion behaviour of the alloy after different test periods is also explained.  相似文献   
47.
炼油达标污水回用处理试验研究   总被引:1,自引:0,他引:1  
采用曝气生物滤池、多介质过滤、超滤、反渗透工艺,对炼油达标外排污水进行回用处理中试试验。结果表明,曝气生物滤池对油、COD和浊度去除效果良好,超滤、反渗透膜化学清洗周期达到 2个月以上,脱盐率稳定在98%以上,产水品质达到回用要求。  相似文献   
48.
管道风险管理方法研究   总被引:6,自引:0,他引:6  
按照管道风险管理的流程分别对管道风险评价、风险控制和决策支持、效能测试和响应进行了论述。针对目前国内管道行业的情况,提出了进行管道风险评价的有效方法及维护措施。着重介绍了国外管道风险可接受标准的情况,作为国内制定管道风险评价标准的参考。  相似文献   
49.
通过对解决GSM移动通信网络热点区域话务拥塞问题的研究,提出了利用可控功分器实现智能动态网络资源的分配,解决不同种类的话务拥塞问题,并着重讨论了该系统目前的成功运用及前景。  相似文献   
50.
The recent advancement in high- performance semiconductor packages has been driven by the need for higher pin count and superior heat dissipation. A one-piece cavity lid flip chip ball grid array (BGA) package with high pin count and targeted reliability has emerged as a popular choice. The flip chip technology can accommodate an I/O count of more than five hundreds500, and the die junction temperature can be reduced to a minimum level by a metal heat spreader attachment. None the less, greater expectations on these high-performance packages arose such as better substrate real estate utilization for multiple chips, ease in handling for thinner core substrates, and improved board- level solder joint reliability. A new design of the flip chip BGA package has been looked into for meeting such requirements. By encapsulating the flip chip with molding compound leaving the die top exposed, a planar top surface can be formed. A, and a flat lid can then be mounted on the planar mold/die top surface. In this manner the direct interaction of the metal lid with the substrate can be removed. The new package is thus less rigid under thermal loading and solder joint reliability enhancement is expected. This paper discusses the process development of the new package and its advantages for improved solder joint fatigue life, and being a multichip package and thin core substrate options. Finite-element simulations have been employed for the study of its structural integrity, thermal, and electrical performances. Detailed package and board-level reliability test results will also be reported  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