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   335780篇
  免费   5054篇
  国内免费   1004篇
电工技术   5644篇
综合类   792篇
化学工业   52530篇
金属工艺   12616篇
机械仪表   9638篇
建筑科学   8081篇
矿业工程   2231篇
能源动力   7545篇
轻工业   29532篇
水利工程   3824篇
石油天然气   7174篇
武器工业   20篇
无线电   33687篇
一般工业技术   61763篇
冶金工业   70140篇
原子能技术   7775篇
自动化技术   28846篇
  2021年   2662篇
  2019年   2315篇
  2018年   4478篇
  2017年   4620篇
  2016年   5307篇
  2015年   3526篇
  2014年   5107篇
  2013年   13123篇
  2012年   9479篇
  2011年   12326篇
  2010年   8765篇
  2009年   9941篇
  2008年   10026篇
  2007年   9863篇
  2006年   8736篇
  2005年   10785篇
  2004年   9510篇
  2003年   8743篇
  2002年   7659篇
  2001年   7359篇
  2000年   6596篇
  1999年   6884篇
  1998年   20209篇
  1997年   14378篇
  1996年   10794篇
  1995年   7810篇
  1994年   6894篇
  1993年   6808篇
  1992年   4718篇
  1991年   4728篇
  1990年   4571篇
  1989年   4559篇
  1988年   4509篇
  1987年   3808篇
  1986年   3790篇
  1985年   4323篇
  1984年   4042篇
  1983年   3711篇
  1982年   3561篇
  1981年   3756篇
  1980年   3618篇
  1979年   3423篇
  1978年   3547篇
  1977年   4480篇
  1976年   6232篇
  1975年   3245篇
  1974年   3048篇
  1973年   3076篇
  1972年   2690篇
  1971年   2515篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
Microbial fuel cell (MFC) is a promising technology for simultaneous wastewater treatment and energy harvesting. The properties of the anode material play a critical role in the performance of the MFC. In this study, graphene oxide was prepared by a modified hummer's method. A thin layer of graphene oxide was incorporated on the carbon brush using an electrophoretic technique. The deoxygenated graphene oxide formed on the surface of the carbon brush (RGO-CB) was investigated as a bio-anode in MFC operated with real wastewater. The performance of the MFC using the RGO-CB was compared with that using plain carbon brush anode (PCB). Results showed that electrophoretic deposition of graphene oxide on the surface of carbon brush significantly enhanced the performance of the MFC, where the power density increased more than 10 times (from 33 mWm?2 to 381 mWm?2). Although the COD removal was nearly similar for the two MFCs, i.e., with PCB and RGO-CB; the columbic efficiency significantly increased in the case of RGO-CB anode. The improved performance in the case of the modified electrode was related to the role of the graphene in improving the electron transfer from the microorganism to the anode surface, as confirmed from the electrochemical impedance spectroscopy measurements.  相似文献   
75.
Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision.  相似文献   
76.
Wireless Personal Communications - In this article compact multiple input multiple output (MIMO) antenna with triple notch at the ultra-wideband application having two identical monopole antennas...  相似文献   
77.
Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis...  相似文献   
78.
N. Boukortt  S. Patan&#;  G. Crupi 《SILICON》2020,12(7):1585-1591
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra  相似文献   
79.
The enhancement of the thermal conductivity, keeping the electrical insulation, of epoxy thermosets through the addition of pristine and oxidized carbon nanotubes (CNTs) and microplatelets of boron nitride (BN) was studied. Two different epoxy resins were selected: a cycloaliphatic (ECC) epoxy resin and a glycidylic (DGEBA) epoxy resin. The characteristics of the composites prepared were evaluated and compared in terms of thermal, thermomechanical, rheological and electrical properties. Two different dispersion methods were used in the addition of pristine and oxidized CNTs depending on the type of epoxy resin used. Slight changes in the kinetics of the curing reaction were observed in the presence of the fillers. The addition of pristine CNTs led to a greater enhancement of the mechanical properties of the ECC composite whereas the oxidized CNTs presented a greater effect in the DGEBA matrix. The addition of CNTs alone led to a marked decrease of the electrical resistivity of the composites. Nevertheless, in the presence of BN, which is an electrically insulating material, it was possible to increase the proportion of pristine CNTs to 0.25 wt% in the formulation without deterioration of the electrical resistivity. A small but significant synergic effect was determined when both fillers were added together. Improvements of about 750% and 400% in thermal conductivity were obtained in comparison to the neat epoxy matrix for the ECC and DGEBA composites, respectively. © 2019 Society of Chemical Industry  相似文献   
80.
Context: The administration of pharmabiotics is a promising alternative to antimicrobial drugs for the treatment and/or prevention of female urogenital infections.

Objective: To design pharmabiotic formulations including bioactive ingredients of microbial origin combined with non-microbial substances and then to evaluate the stability of the combinations during freeze-drying and storage.

Materials and methods: Different formulations including Lactobacillus gasseri CRL 1263, Lactobacillus salivarius CRL 1328, salivaricin CRL 1328 (a bacteriocin) and non-microbial compounds (lactose, inulin and ascorbic acid) were assayed, and the ingredients were freeze-dried together or separately. The formulations were stored in gelatin capsules at 4?°C for 360?d.

Results: The viability of lactobacilli was affected to different extents depending on the strains and on the formulations assayed. L. salivarius and ascorbic acid were successfully combined only after the freeze-drying process. Salivaricin activity was not detected in formulations containing L. gasseri. However, when combined with ascorbic acid, lactose, inulin or L. salivarius, the bacteriocin maintained its activity for 360?d. The selected microorganisms proved to be compatible for their inclusion in multi-strain formulations together with lactose, inulin and ascorbic acid. Salivaricin could be included only in a L. salivarius CRL 1328 single-strain formulation together with non-microbial substances.

Conclusions: This study provides new insights into the design of urogenital pharmabiotics combining beneficial lactobacilli, salivaricin CRL 1328 and compounds with different functionalities.  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