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   202688篇
  免费   25830篇
  国内免费   6101篇
电工技术   9358篇
技术理论   9篇
综合类   8752篇
化学工业   43408篇
金属工艺   10366篇
机械仪表   10781篇
建筑科学   11476篇
矿业工程   3936篇
能源动力   4484篇
轻工业   16109篇
水利工程   3426篇
石油天然气   9577篇
武器工业   1052篇
无线电   24128篇
一般工业技术   37359篇
冶金工业   11862篇
原子能技术   4848篇
自动化技术   23688篇
  2024年   716篇
  2023年   2338篇
  2022年   4668篇
  2021年   6447篇
  2020年   5961篇
  2019年   6897篇
  2018年   7959篇
  2017年   8712篇
  2016年   8719篇
  2015年   9308篇
  2014年   10920篇
  2013年   13617篇
  2012年   12087篇
  2011年   12511篇
  2010年   11223篇
  2009年   10976篇
  2008年   10402篇
  2007年   9796篇
  2006年   8942篇
  2005年   7611篇
  2004年   6093篇
  2003年   5993篇
  2002年   6002篇
  2001年   5410篇
  2000年   4812篇
  1999年   3779篇
  1998年   2776篇
  1997年   2314篇
  1996年   2040篇
  1995年   1770篇
  1994年   1513篇
  1993年   1278篇
  1992年   1251篇
  1991年   1113篇
  1990年   1116篇
  1989年   1028篇
  1988年   909篇
  1987年   852篇
  1986年   780篇
  1985年   730篇
  1984年   718篇
  1981年   681篇
  1979年   744篇
  1978年   783篇
  1977年   747篇
  1976年   761篇
  1975年   718篇
  1974年   721篇
  1973年   729篇
  1972年   707篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Here, LiY(WO4)2 nanotubes are prepared via a feasible electrospinning technique. This new anode material shows excellent electrochemical properties. The capacity loss of LiY(WO4)2 nanotubes is as low as 6.9% after 156 cycles, while bulk LiY(WO4)2 presents the capacity loss higher than 55.0%. Even after 600 long-life cycles, the capacity loss of the nanotubes is only 9%. It can be seen that the hollow structure with a rough surface and a porous morphology contributes to the improvement of electrochemical performance. Furthermore, online X-ray diffraction (XRD) method is firstly applied to understand the lithium ions insertion/extraction mechanism of LiY(WO4)2 nanotubes. It can be concluded that it is an asymmetrical two-phase reaction. A phase transformation from LiY(WO4)2 to Li3Y(WO4)2 can be obviously seen from the in situ XRD during discharge process. While Li2Y(WO4)2 appears as an intermediate phase with a reverse charge reaction. In addition, in situ XRD also demonstrates that LiY(WO4)2 nanotubes have surprised electrochemical reversibility. All the above results indicate that LiY(WO4)2 nanotubes can be expected to be anode candidate for rechargeable lithium ion batteries (LIBs).  相似文献   
94.
95.
Morozov  Yu. D.  Pemov  I. F.  Matrosov  M. Yu.  Zin’ko  B. F. 《Metallurgist》2020,63(9-10):933-950
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of...  相似文献   
96.
Dong  Ziliang  Hao  Yu  Li  Quguang  Yang  Zhijuan  Zhu  Yujie  Liu  Zhuang  Feng  Liangzhu 《Nano Research》2020,13(11):3057-3067

Construction of multifunctional stimuli-responsive nanotherapeutics enabling improved intratumoral penetration of therapeutics and reversal of multiple-drug resistance (MDR) is potent to achieve effective cancer treatment. Herein, we report a general method to synthesize pH-dissociable calcium carbonate (CaCO3) hollow nanoparticles with amorphous CaCO3 as the template, gallic acid (GA) as the organic ligand, and ferrous ions as the metallic center via a one-pot coordination reaction. The obtained GA–Fe@CaCO3 exhibits high loading efficiencies to both oxidized cisplatin prodrug and doxorubicin, yielding drug loaded GA–Fe@CaCO3 nanotherapeutics featured in pH-responsive size shrinkage, drug release, and Fenton catalytic activity. Compared to nonresponsive GA–Fe@silica nanoparticles prepared with silica nanoparticles as the template, such GA–Fe@CaCO3 confers significantly improved intratumoral penetration capacity. Moreover, both types of drug-loaded GA–Fe@CaCO3 nanotherapeutics exhibit synergistic therapeutic efficacies to corresponding MDR cancer cells because of the GA–Fe mediated intracellular oxidative stress amplification that could reduce the efflux of engulfed drugs by impairing the mitochondrial-mediated production of adenosine triphosphate (ATP). As a result, it is found that the doxorubicin loaded GA–Fe@CaCO3 exhibits superior therapeutic effect towards doxorubicin-resistant 4T1 breast tumors via combined chemodynamic and chemo-therapies. This work highlights the preparation of pH-dissociable CaCO3-based nanotherapeutics to enable effective tumor penetration for enhanced treatment of drug-resistant tumors.

  相似文献   
97.
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research.  相似文献   
98.
99.
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients.  相似文献   
100.
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