全文获取类型
收费全文 | 48150篇 |
免费 | 2756篇 |
国内免费 | 152篇 |
专业分类
电工技术 | 701篇 |
综合类 | 63篇 |
化学工业 | 9578篇 |
金属工艺 | 2133篇 |
机械仪表 | 3236篇 |
建筑科学 | 1095篇 |
矿业工程 | 24篇 |
能源动力 | 2102篇 |
轻工业 | 3865篇 |
水利工程 | 269篇 |
石油天然气 | 86篇 |
武器工业 | 2篇 |
无线电 | 7791篇 |
一般工业技术 | 10577篇 |
冶金工业 | 3878篇 |
原子能技术 | 658篇 |
自动化技术 | 5000篇 |
出版年
2023年 | 537篇 |
2022年 | 327篇 |
2021年 | 1345篇 |
2020年 | 1069篇 |
2019年 | 1175篇 |
2018年 | 1429篇 |
2017年 | 1411篇 |
2016年 | 1750篇 |
2015年 | 1293篇 |
2014年 | 2088篇 |
2013年 | 3006篇 |
2012年 | 3265篇 |
2011年 | 3889篇 |
2010年 | 2814篇 |
2009年 | 2921篇 |
2008年 | 2811篇 |
2007年 | 2185篇 |
2006年 | 2031篇 |
2005年 | 1723篇 |
2004年 | 1571篇 |
2003年 | 1505篇 |
2002年 | 1302篇 |
2001年 | 1079篇 |
2000年 | 901篇 |
1999年 | 839篇 |
1998年 | 1489篇 |
1997年 | 936篇 |
1996年 | 751篇 |
1995年 | 555篇 |
1994年 | 459篇 |
1993年 | 405篇 |
1992年 | 282篇 |
1991年 | 271篇 |
1990年 | 257篇 |
1989年 | 241篇 |
1988年 | 203篇 |
1987年 | 167篇 |
1986年 | 119篇 |
1985年 | 115篇 |
1984年 | 91篇 |
1983年 | 61篇 |
1982年 | 38篇 |
1981年 | 39篇 |
1980年 | 30篇 |
1979年 | 30篇 |
1978年 | 30篇 |
1977年 | 38篇 |
1976年 | 61篇 |
1975年 | 19篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 167 毫秒
101.
Min-Kyung Kang Soo-Il Kim Su Yeon Oh Woojin Na Young-Hee Kang 《International journal of molecular sciences》2020,21(22)
Podocyte injury inevitably results in leakage of proteins from the glomerular filter and is vital in the pathogenesis of diabetic nephropathy (DN). The underlying mechanisms of podocyte injury facilitate finding of new therapeutic targets for DN treatment and prevention. Tangeretin is an O-polymethoxylated flavone present in citrus peels with anti-inflammatory and antioxidant properties. This study investigated the renoprotective effects of tangeretin on epithelial-to-mesenchymal transition-mediated podocyte injury and fibrosis through oxidative stress and hypoxia caused by hyperglycemia. Mouse podocytes were incubated in media containing 33 mM glucose in the absence and presence of 1–20 μM tangeretin for up to 6 days. The in vivo animal model employed db/db mice orally administrated with 10 mg/kg tangeretin for 8 weeks. Non-toxic tangeretin inhibited glucose-induced expression of the mesenchymal markers of N-cadherin and α-smooth muscle actin in podocytes. However, the reduced induction of the epithelial markers of E-cadherin and P-cadherin was restored by tangeretin in diabetic podocytes. Further, tangeretin enhanced the expression of the podocyte slit diaphragm proteins of nephrin and podocin down-regulated by glucose stimulation. The transmission electron microscopic images revealed that foot process effacement and loss of podocytes occurred in diabetic mouse glomeruli. However, oral administration of 10 mg/kg tangeretin reduced urine albumin excretion and improved foot process effacement of diabetic podocytes through inhibiting loss of slit junction and adherenes junction proteins. Glucose enhanced ROS production and HIF-1α induction in podocytes, leading to induction of oxidative stress and hypoxia. Similarly, in diabetic glomeruli reactive oxygen species (ROS) production and HIF-1α induction were observed. Furthermore, hypoxia-evoking cobalt chloride induced epithelial-to-mesenchymal transition (EMT) process and loss of slit diaphragm proteins and junction proteins in podocytes, which was inhibited by treating submicromolar tangeretin. Collectively, these results demonstrate that tangeretin inhibited podocyte injury and fibrosis through blocking podocyte EMT caused by glucose-induced oxidative stress and hypoxia. 相似文献
102.
103.
104.
105.
Identifying and Verifying Vulnerabilities through PLC Network Protocol and Memory Structure Analysis
Joo-Chan Lee Hyun-Pyo Choi Jang-Hoon Kim Jun-Won Kim Da-Un Jung Ji-Ho Shin Jung-Taek Seo 《计算机、材料和连续体(英文)》2020,65(1):53-67
Cyberattacks on the Industrial Control System (ICS) have recently been
increasing, made more intelligent by advancing technologies. As such, cybersecurity for
such systems is attracting attention. As a core element of control devices, the
Programmable Logic Controller (PLC) in an ICS carries out on-site control over the ICS. A
cyberattack on the PLC will cause damages on the overall ICS, with Stuxnet and Duqu as
the most representative cases. Thus, cybersecurity for PLCs is considered essential, and
many researchers carry out a variety of analyses on the vulnerabilities of PLCs as part of
preemptive efforts against attacks. In this study, a vulnerability analysis was conducted on
the XGB PLC. Security vulnerabilities were identified by analyzing the network protocols
and memory structure of PLCs and were utilized to launch replay attack, memory
modulation attack, and FTP/Web service account theft for the verification of the results.
Based on the results, the attacks were proven to be able to cause the PLC to malfunction
and disable it, and the identified vulnerabilities were defined. 相似文献
106.
Wontae Lee Soyeong Yun Hao Li Jaeyoung Kim Hayeon Lee Kyeongkeun Kwon Jin Yong Lee Young‐Min Choi Won‐Sub Yoon 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(5)
The anionic redox chemistries of layered cathode materials have been in focus recently due to an intriguing phenomenon that cannot be described by the number of electrons of transition metal ions. However, even though several studies have investigated the anionic redox chemistry of layered materials in terms of the charge compensation, the relationship between the origin of the structural behavior and anionic redox chemistry in layered materials remains poorly understood. In addition, a simultaneous redox process of transition metal ions could occur through the d bands interaction. Here, it is demonstrated that the anionic redox chemistry is associated with the anisotropic structural behavior of the layered cathode materials albeit without providing additional capacities exceeding the theoretical values. These findings will provide a foundation of a new chapter in the understanding of the properties of materials. 相似文献
107.
Mani Balamurugan Hui‐Yun Jeong Venkata Surya Kumar Choutipalli Jung Sug Hong Hongmin Seo Natarajan Saravanan Jun Ho Jang Kang‐Gyu Lee Yoon Ho Lee Sang Won Im Venkatesan Subramanian Sun Hee Kim Ki Tae Nam 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions. 相似文献
108.
Jongmin Lee Hongji Yoon Kyoung Soon Choi Seungkyu Kim Sehun Seo Jaesun Song Byeong‐Uk Choi Jiseung Ryu Sangwoo Ryu Jihun Oh Cheolho Jeon Sanghan Lee 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(39)
To develop strategies for efficient photo‐electrochemical water‐splitting, it is important to understand the fundamental properties of oxide photoelectrodes by synthesizing and investigating their single‐crystal thin films. However, it is challenging to synthesize high‐quality single‐crystal thin films from copper‐based oxide photoelectrodes due to the occurrence of significant defects such as copper or oxygen vacancies and grains. Here, the CuBi2O4 (CBO) single‐crystal thin film photocathode is achieved using a NiO template layer grown on single‐crystal SrTiO3 (STO) (001) substrate via pulsed laser deposition. The NiO template layer plays a role as a buffer layer of large lattice mismatch between CBO and STO (001) substrate through domain‐matching epitaxy, and forms a type‐II band alignment with CBO, which prohibits the transfer of photogenerated electrons toward bottom electrode. The photocurrent densities of the CBO single‐crystal thin film photocathode demonstrate ?0.4 and ?0.7 mA cm?2 at even 0 VRHE with no severe dark current under illumination in a 0.1 m potassium phosphate buffer solution without and with H2O2 as an electron scavenger, respectively. The successful synthesis of high‐quality CBO single‐crystal thin film would be a cornerstone for the in‐depth understanding of the fundamental properties of CBO toward efficient photo‐electrochemical water‐splitting. 相似文献
109.
110.
Yong Joo Park Kwang Ho Lee Mi Seon Jeon Yong Hoon Lee Yoon Joo Ko Changhyun Pang Bonglee Kim Kyu Hyuck Chung Ki Hyun Kim 《International journal of molecular sciences》2020,21(23)
Rhubarb is a well-known herb worldwide and includes approximately 60 species of the Rheum genus. One of the representative plants is Rheum palmatum, which is prescribed as official rhubarb due to its pharmacological potential in the Korean and Chinese pharmacopoeia. In our bioactive screening, we found out that the EtOH extract of R. palmatum inhibited hepatic stellate cell (HSC) activation by transforming growth factor β1 (TGF-β1). Chemical investigation of the EtOH extract led to the isolation of chrysophanol 8-O-glucoside, which was determined by structural analysis using NMR spectroscopic techniques and electrospray ionization mass spectrometry (ESIMS). To elucidate the effects of chrysophanol 8-O-glucoside on HSC activation, activated LX-2 cells were treated for 48 h with chrysophanol 8-O-glucoside, and α-SMA and collagen, HSC activation markers, were measured by comparative quantitative real-time PCR (qPCR) and western blotting analysis. Chrysophanol 8-O-glucoside significantly inhibited the protein and mRNA expression of α-SMA and collagen compared with that in TGF-β1-treated LX-2 cells. Next, the expression of phosphorylated SMAD2 (p-SMAD2) and p-STAT3 was measured and the translocation of p-STAT3 to the nucleus was analyzed by western blotting analysis. The expression of p-SMAD2 and p-STAT3 showed that chrysophanol 8-O-glucoside strongly downregulated STAT3 phosphorylation by inhibiting the nuclear translocation of p-STAT3, which is an important mechanism in HSC activation. Moreover, chrysophanol 8-O-glucoside suppressed the expression of p-p38, not that of p-JNK or p-Erk, which can activate STAT3 phosphorylation and inhibit MMP2 expression, the downstream target of STAT3 signaling. These findings provided experimental evidence concerning the hepatoprotective effects of chrysophanol 8-O-glucoside against liver damage and revealed the molecular basis underlying its anti-fibrotic effects through the blocking of HSC activation. 相似文献