全文获取类型
收费全文 | 61195篇 |
免费 | 3187篇 |
国内免费 | 205篇 |
学科分类
工业技术 | 64587篇 |
出版年
2023年 | 553篇 |
2022年 | 336篇 |
2021年 | 1399篇 |
2020年 | 1144篇 |
2019年 | 1186篇 |
2018年 | 1514篇 |
2017年 | 1540篇 |
2016年 | 1859篇 |
2015年 | 1504篇 |
2014年 | 2317篇 |
2013年 | 3918篇 |
2012年 | 3620篇 |
2011年 | 4465篇 |
2010年 | 3348篇 |
2009年 | 3554篇 |
2008年 | 3237篇 |
2007年 | 2722篇 |
2006年 | 2509篇 |
2005年 | 2174篇 |
2004年 | 2054篇 |
2003年 | 1892篇 |
2002年 | 1771篇 |
2001年 | 1361篇 |
2000年 | 1205篇 |
1999年 | 1163篇 |
1998年 | 2227篇 |
1997年 | 1448篇 |
1996年 | 1204篇 |
1995年 | 1010篇 |
1994年 | 765篇 |
1993年 | 704篇 |
1992年 | 518篇 |
1991年 | 513篇 |
1990年 | 440篇 |
1989年 | 433篇 |
1988年 | 338篇 |
1987年 | 292篇 |
1986年 | 270篇 |
1985年 | 250篇 |
1984年 | 215篇 |
1983年 | 156篇 |
1982年 | 152篇 |
1981年 | 141篇 |
1980年 | 134篇 |
1979年 | 110篇 |
1978年 | 97篇 |
1977年 | 128篇 |
1976年 | 166篇 |
1975年 | 80篇 |
1974年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
51.
Shaohui Li Jingwei Chen Jiaqing Xiong Xuefei Gong Jinghao Ciou Pooi See Lee 《纳微快报(英文)》2020,(3):55-68
Sodium-ion capacitors(SICs)have received increasing interest for grid stationary energy storage application due to their affordability,high power,and energy densities.The major challenge for SICs is to overcome the kinetics imbalance between faradaic anode and nonfaradaic cathode.To boost the Na+reaction kinetics,the present work demonstrated a high-rate MnS-based anode by embedding the MnS nanocrystals into the N,S-co-doped carbon matrix(MnS@NSC).Benefiting from the fast pseudocapacitive Na+storage behavior,the resulting composite exhibits extraordinary rate capability(205.6 mAh g−1 at 10 A g−1)and outstanding cycling stability without notable degradation after 2000 cycles.A prototype SIC was demonstrated using MnS@NSC anode and N-doped porous carbon(NC)cathode;the obtained hybrid SIC device can display a high energy density of 139.8 Wh kg−1 and high power density of 11,500 W kg−1,as well as excellent cyclability with 84.5%capacitance retention after 3000 cycles.The superior electrochemical performance is contributed to downsizing of MnS and encapsulation of conductive N,S-co-doped carbon matrix,which not only promote the Na+and electrons transport,but also buffer the volume variations and maintain the structure integrity during Na+insertion/extraction,enabling its comparable fast reaction kinetics and cyclability with NC cathode. 相似文献
52.
53.
Xiling Yao Seung Ki Moon Guijun Bi Jun Wei 《The International Journal of Advanced Manufacturing Technology》2018,99(9-12):2111-2119
Additive manufacturing (AM) technologies provide more freedom to functional part design in various industries. One of the unique capabilities of AM is that multi-material parts can be produced with material compositional and geometric complexity. Multi-material parts have the advantage of achieving multiple performance requirements. In the research, we propose a framework for designing multi-material parts using AM processes. The proposed framework is composed of four interacting modules, including design requirement identification, primary material selection, AM process selection, material composition, and part geometry determination. Rules and guidelines for AM are integrated into the proposed framework with AM processes’ capabilities and constraints compiled in databases. We also introduce databases to assist in decision-making and ensure manufacturability of the designed multi-material part in various product design phases. The proposed framework is applied to a case study involving a conceptual design of a multi-material battery pack cooling plate. 相似文献
54.
Nader Tehrani Dan Gallagher Monica Ponce de Leon Harry Lowd Richard Lee Lisa Huang Remon Alberts Janghwan Cheon Jumanah Jamal Aishah Al Sager 《世界建筑导报》2018,(2)
正Banq餐厅位是一家新型餐厅,位于便士储蓄银行(Penny Savings Bank)旧大楼以前用来经营银行业务的大厅内。餐厅分成两个部分,前面区域面向华盛顿大街,设计成酒吧,后面的大厅则作为用餐区。然而,这个空间在z轴上以天花板和地面之间的另一个分区为中心进行设计。如果由于餐厅空间活动的多变性而需要保持灵活性——包括两个座位、四个座位和六个座位,以及与聚会和其他活动有关的座位 相似文献
55.
Chia‐Che Chang Sin‐Ren Li Hung‐Lung Chou Yi‐Cheng Lee Shivaraj Patil Ying‐Sheng Lin Chun‐Chih Chang Yuan Jay Chang Di‐Yan Wang 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(49)
The generation of ammonia, hydrogen production, and nitrogen purification are considered as energy intensive processes accompanied with large amounts of CO2 emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth‐abundant iron pyrite (FeS2) nanocrystals grown on carbon fiber paper (FeS2/CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS2/CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH3 yield rate of ≈0.096 µg min?1 at ?0.6 V versus RHE electrode in 0.25 m LiClO4. During the electrochemical catalytic reaction, the crystal structure of FeS2/CFP remains in the cubic pyrite phase, as analyzed by in situ X‐ray diffraction measurements. With near‐infrared laser irradiation (808 nm), the NH3 yield rate of the FeS2/CFP catalyst can be slightly improved to 0.1 µg min?1 with high FE of 14.57%. Furthermore, density functional theory calculations demonstrate that the N2 molecule has strong chemical adsorption energy on the iron atom of FeS2. Overall, iron pyrite‐based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications. 相似文献
56.
Ruxiu Liu Chia‐Heng Chu Ningquan Wang Tevhide Ozkaya‐Ahmadov Ozgun Civelekoglu Dohwan Lee A K M Arifuzzman A. Fatih Sarioglu 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(51)
Immunophenotyping is widely used to characterize cell populations in basic research and to diagnose diseases from surface biomarkers in the clinic. This process usually requires complex instruments such as flow cytometers or fluorescence microscopes, which are typically housed in centralized laboratories. Microfluidics are combined with an integrated electrical sensor network to create an antibody microarray for label‐free cell immunophenotyping against multiple antigens. The device works by fractionating the sample via capturing target subpopulations in an array of microfluidic chambers functionalized against different antigens and by electrically quantifying the cell capture statistics through a network of code‐multiplexed electrical sensors. Through a combinatorial arrangement of antibody sequences along different microfluidic paths, the device can measure the prevalence of different cell subpopulations in a sample from computational analysis of the electrical output signal. The device performance is characterized by analyzing heterogeneous samples of mixed tumor cell populations and then the technique is applied to determine leukocyte subpopulations in blood samples and the results are validated against complete blood cell count and flow cytometry results. Label‐free immunophenotyping of cell populations against multiple targets on a disposable electronic chip presents opportunities in global health and telemedicine applications for cell‐based diagnostics and health monitoring. 相似文献
57.
Michael E. Sierszen Lee S. Schoen Jessica M. Kosiara Joel C. Hoffman Matthew J. Cooper Donald G. Uzarski 《Journal of Great Lakes research》2019,45(1):129-137
Hydrologic linkages among coastal wetland and nearshore areas allow coastal fish to move among the habitats, which has led to a variety of habitat use patterns. We determined nutritional support of coastal fishes from 12 wetland-nearshore habitat pairs using stable isotope analyses, which revealed differences among species and systems in multi-habitat use. Substantial (proportions?>?0.30) nutrition often came from the habitat other than that in which fish were captured. Nearshore subsidies to coastal wetlands indicate wetlands are not exclusively exporters of energy and materials; rather, there is reciprocity in the mutual energetic support of nearshore and wetland food webs. Coastal wetland hydrogeomorphology influenced the amount of multi-habitat use by coastal fishes. Fishes from systems with relatively open interfaces between wetland and nearshore habitats exhibited less nutritional reliance on the habitat in which they were captured, and higher use of resources from the adjacent habitat. Comparisons of stable isotope analyses of nutrition with otolith analyses of occupancy indicated nutritional sources often corresponded with habitat occupancy; however, disparities among place of capture, otolith analyses, and nutritional analyses indicated differences in the types of support those analyses inform. Disparities between occupancy information and nutritional information can stem from movements for support functions other than foraging. Together, occupancy information from otolith microchemistry and nutritional information from stable isotope analyses provide complementary measures of the use of multiple habitats by mobile consumers. This work underscores the importance of protecting or restoring a diversity of coastal habitats and the hydrologic linkages among them. 相似文献
58.
Ibupoto Fahim Ahmed Lim Janggyun Kim Seongkyun Kim Bum Joon Baik Seunghyun Kim Moon Ki 《Journal of Mechanical Science and Technology》2019,33(12):5809-5815
Journal of Mechanical Science and Technology - Presently, countries are trying to increase their energy efficiency. Therefore, the operating temperatures of very high temperature reactor (VHTR) and... 相似文献
59.
60.
This paper proposes the Internet connectivity of RF-powered devices in the backscatter system. The RF-powered devices do not use a battery and charge energy by harvesting from ambient RF signals of TV, a cellular phone and Wi-Fi devices. The Internet connectivity of the RF-powered devices in the backscatter system is very useful in Internet of things technology because the RF-powered devices which are called to a tag have a small size by the harvesting from ambient RF signals without a battery. This paper proposes a method improving the communication performance of the Wi-Fi backscatter system by applying the cooperative communication scheme.
相似文献