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   7613篇
  免费   475篇
  国内免费   8篇
电工技术   138篇
综合类   8篇
化学工业   1898篇
金属工艺   224篇
机械仪表   220篇
建筑科学   218篇
矿业工程   26篇
能源动力   263篇
轻工业   936篇
水利工程   48篇
石油天然气   46篇
武器工业   1篇
无线电   498篇
一般工业技术   2035篇
冶金工业   138篇
原子能技术   96篇
自动化技术   1303篇
  2024年   20篇
  2023年   77篇
  2022年   121篇
  2021年   246篇
  2020年   192篇
  2019年   211篇
  2018年   322篇
  2017年   303篇
  2016年   344篇
  2015年   253篇
  2014年   404篇
  2013年   770篇
  2012年   505篇
  2011年   630篇
  2010年   478篇
  2009年   379篇
  2008年   324篇
  2007年   304篇
  2006年   218篇
  2005年   138篇
  2004年   131篇
  2003年   123篇
  2002年   137篇
  2001年   79篇
  2000年   89篇
  1999年   70篇
  1998年   68篇
  1997年   56篇
  1996年   50篇
  1995年   53篇
  1994年   55篇
  1993年   57篇
  1992年   50篇
  1991年   35篇
  1990年   35篇
  1989年   33篇
  1988年   24篇
  1985年   50篇
  1984年   57篇
  1983年   48篇
  1982年   45篇
  1981年   66篇
  1980年   55篇
  1979年   48篇
  1978年   43篇
  1977年   37篇
  1976年   48篇
  1975年   34篇
  1974年   22篇
  1973年   35篇
排序方式: 共有8096条查询结果,搜索用时 31 毫秒
11.
12.
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   
13.
The relatively low capacitance of negative electrodes, as compared to the capacitance of advanced positive electrodes, poses a serious problem, since this limits the development of asymmetric supercapacitor (SC) devices with a large voltage window and enhanced power-energy characteristics. We fabricate negative SC electrodes with a high capacitance that match the capacitance of advanced positive electrodes at similar active mass loadings, as high as 37?mg?cm?2. Cyclic voltammetry, impedance spectroscopy, galvanostatic charge-discharge data and the power-energy characteristics of the asymmetric SC device exhibit good electrochemical performance for a voltage window of 1.6?V. Our approach involves the development and application of particle extraction through liquid-liquid interface (PELLI) methods, new extraction mechanisms and efficient extractors to synthesize α-FeOOH and β-FeOOH electrode materials. The use of PELLI allows agglomerate-free processing of powders, which facilitates their efficient mixing with multiwalled carbon nanotubes (MWCNT) and allows improved electrolyte access to the particle surface. Experiments to determine the properties of FeOOH-MWCNT composites provided insight into the influence of the electrode material and the structure of extractor molecules on the composite properties. The highest capacitance of 5.86?F?cm?2 for negative electrodes and low impedance were achieved using α-FeOOH-MWCNT composites and a 16-phosphonohexadecanoic acid (PHDA) extractor. This extractor allows adsorption on particles, not only at the liquid-liquid interface, but also in the bulk aqueous phase and can potentially be used as a capping agent for particle synthesis and as an extractor in the PELLI method.  相似文献   
14.
Bruton's tyrosine kinase (Btk) is an attractive target for the treatment of a wide array of B-cell malignancies and autoimmune diseases. Small-molecule covalent irreversible Btk inhibitors targeting Cys481 have been developed for the treatment of such diseases. In clinical trials, probe molecules are required in occupancy studies to measure the level of engagement of the protein by these covalent irreversible inhibitors. The result of this pharmacodynamic (PD) activity provides guidance for appropriate dosage selection to optimize inhibition of the drug target and correlation of target inhibition with disease treatment efficacy. This information is crucial for successful evaluation of drug candidates in clinical trials. Based on the pyridine carboxamide scaffold of a novel solvent-accessible pocket (SAP) series of covalent irreversible Btk inhibitors, we successfully developed a potent and selective affinity-based biotinylated probe 12 (2-[(4-{4-[5-(1-{5-[(3aS,4S,6aR)-2-oxo-hexahydro-1H-thieno[3,4-d]imidazol-4-yl]pentanamido}-3,6,9,12-tetraoxapentadecan-15-amido)pentanoyl]piperazine-1-carbonyl}phenyl)amino]-6-[1-(prop-2-enoyl)piperidin-4-yl]pyridine-3-carboxamide). Compound 12 has been used in Btk occupancy assays for preclinical studies to determine the therapeutic efficacy of Btk inhibition in two mouse lupus models driven by TLR7 activation and type I interferon.  相似文献   
15.
16.
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   
17.
The inter-comparative analysis of the deterministic safety potential of innovative molten salt systems with critical and sub-critical cores is presented for both fast and thermal neutron spectra. The analysis includes two aspects: the choice of an initial level of sub-criticality and the study of multiple unprotected transients which have been simulated on the basis of one-point kinetics and two-point thermo-hydraulic schemes considering realistic feedback effects. Our preliminary results show that even small levels of sub-criticality (2–3 dollars) of cores can improve their safety characteristics significantly.  相似文献   
18.
Identification of anthocyanins in the wine made of the Croatian autochthonous grape variety of Babić (Vitis vinifera L.) was carried out and their profile was determined by means of high-performance liquid chromatography with diode array and mass spectrometric detection. Dependence of anthocyanins content and profile on maceration treatment conditions was investigated. Statistically significant differences of anthocyanins concentration in wines Babić produced by various maceration treatments were confirmed by the use of multivariate analysis of variances. The investigation results indicated that the maceration temperature exerts higher influence on anthocyanins concentration than the duration of maceration. In addition, on the basis of anthocyanin composition and using different multivariate statistical analyses, differentiation of wines Babić according to maceration treatments was procured.  相似文献   
19.
This paper analyzes the performance of a switching architecture. The performance measures include the elapsed time of packet transfer and the waiting time to begin transfer. The architecture is partitioned depending on the type of network used and the expected traffic in the network. Every partition has a switch with a buffer that can absorb surges of bursty traffic within the network partition. The buffer size depends on the type of the network and incoming traffic. The partition size depends on the network bandwidth, network traffic, packet size and buffer size. Examples of different networks are used to show the applications of the model. The results show that the elapsed time of packet switch transfer depends exponentially on the number of partitions in the network.  相似文献   
20.
Summary Both preferential adsorption coefficient λ and intrinsic viscosity [η] for poly (di-o-alkylphenyl methacrylates) /Tetrahydrofuran (THF)/water have been determined. The results are discussed in relation to the steric effect of the ortho-substituent groups on the aromatic ring.  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