全文获取类型
收费全文 | 37659篇 |
免费 | 4344篇 |
国内免费 | 2074篇 |
专业分类
电工技术 | 2506篇 |
技术理论 | 4篇 |
综合类 | 3201篇 |
化学工业 | 6088篇 |
金属工艺 | 2178篇 |
机械仪表 | 2513篇 |
建筑科学 | 2815篇 |
矿业工程 | 1364篇 |
能源动力 | 1171篇 |
轻工业 | 2918篇 |
水利工程 | 752篇 |
石油天然气 | 1642篇 |
武器工业 | 298篇 |
无线电 | 4374篇 |
一般工业技术 | 4558篇 |
冶金工业 | 1812篇 |
原子能技术 | 500篇 |
自动化技术 | 5383篇 |
出版年
2024年 | 422篇 |
2023年 | 677篇 |
2022年 | 1116篇 |
2021年 | 1545篇 |
2020年 | 1189篇 |
2019年 | 1061篇 |
2018年 | 1148篇 |
2017年 | 1256篇 |
2016年 | 1190篇 |
2015年 | 1581篇 |
2014年 | 1931篇 |
2013年 | 2389篇 |
2012年 | 2469篇 |
2011年 | 2487篇 |
2010年 | 2358篇 |
2009年 | 2150篇 |
2008年 | 2113篇 |
2007年 | 1949篇 |
2006年 | 1937篇 |
2005年 | 1675篇 |
2004年 | 1284篇 |
2003年 | 1510篇 |
2002年 | 2006篇 |
2001年 | 1754篇 |
2000年 | 1094篇 |
1999年 | 859篇 |
1998年 | 560篇 |
1997年 | 457篇 |
1996年 | 373篇 |
1995年 | 344篇 |
1994年 | 271篇 |
1993年 | 176篇 |
1992年 | 166篇 |
1991年 | 143篇 |
1990年 | 91篇 |
1989年 | 77篇 |
1988年 | 62篇 |
1987年 | 36篇 |
1986年 | 30篇 |
1985年 | 22篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 23篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Weikai Ding Yousef Sultan Shumei Li Wenjun Wen Bangjun Zhang Yiyi Feng Junguo Ma Xiaoyu Li 《International journal of molecular sciences》2022,23(11)
Previous studies have indicated that the harmful heavy metal lead (Pb) contamination in aquatic systems has caused intelligence development disorders and nervous system function abnormalities in juveniles due to the increased permeability of the blood–brain barrier. Ionic liquids (ILs) are considered “green” organic solvents that can replace traditional organic solvents. Studies have found the presence of ILs in soil and water due to chemical applications or unintentional leakage. Therefore, what would happen if Pb interacted with ILs in a body of water? Could ILs enable Pb to more easily cross the blood–brain barrier? Therefore, we examined the combined exposure of Pb and ILs in common carp at low concentration (18.3 mg L−1 of Pb(CH3COO)2•3 H2O and 11 mg L−1 of the IL 1-methyl-3-octylimidazolium chloride, 5% of their LC50) for 28 days in the present study. The result of a neurobehavioral assay showed that chronic exposure of lead at lower concentrations significantly altered fish movement and neurobehaviors, indicating that lead exposure caused neurotoxicity in the carp. Increases in the neurotransmitter dopamine levels and injuries in the fish brain accounted for neurobehavioral abnormalities induced by lead exposure. Moreover, we also found that lead could easily cross the blood–brain barrier and caused significant bioaccumulation in the brain. Particularly, our study indicated that the ionic liquid could not synergistically promote blood–brain barrier permeability and hence failed to increase the absorption of lead in the fish brain, suggesting that the combined exposure of lead and ILs was not a synergistic effect but antagonism to the neurotoxicity. The results of this study suggested that ILs could recede the Pb induced neurotoxicity in fish. 相似文献
92.
93.
Xiao Zhang Daoming Liu Dong Gao Weining Zhao Huaying Du Zeyu Qiu Jie Huang Peizheng Wen Yongsheng Wang Qi Li Wenhui Wang Haosen Xu Jun He Yuqiang Liu Jianmin Wan 《International journal of molecular sciences》2022,23(11)
Plants have evolved a sophisticated defense system that employs various hormone pathways to defend against attacks by insect pests. Cytokinin (CK) plays an important role in plant growth and stress tolerance, but the role of CKs in plant–insect interaction remains largely unclear. Here, we report that CKs act as a positive regulator in rice resistance against brown planthopper (BPH), a devastating insect pest of rice. We found that BPH feeding promotes CK biosynthesis and signaling in rice. Exogenous application of CKs significantly increased the rice resistance to BPH. Increasing endogenous CKs by knocking out cytokinin oxidase/dehydrogenase (OsCKXs) led to enhanced resistance to BPH. Moreover, the levels of the plant hormone jasmonic acid (JA) and the expression of JA-responsive genes were elevated by CK treatment and in OsCKXs knockout plants. Furthermore, JA-deficient mutant og1 was more susceptible to BPH, and CK-induced BPH resistance was suppressed in og1. These results indicate that CK-mediated BPH resistance is JA-dependent. Our findings provide the direct evidence for the novel role of CK in promoting insect resistance, and demonstrate that CK-induced insect resistance is JA-dependent. These results provide important guidance for effective pest management strategies in the future. 相似文献
94.
As a two-dimensional (2D) material,graphene shows excellent advantages in the field of gas sensors due to its inherent large specific surface area and unique el... 相似文献
95.
Shun Guo Rui-Tang Wu Yu-Lu Shi Yan-Pin Hou Wen Ma Guang-Lei Liu Hai-Xia Liu Xiao-Nong Cheng 《稀有金属(英文版)》2021,(3):600-606
The deformation behavior involved in Nb/NiTi composite for biomedical applications within a large macroscopic strain range was investigated by tensile loading-unloading test and in situ synchrotron X-ray diffraction(SXRD).Experimental results show that during loading,the Nb/NiTi composite experiences the elastic elongation of B2-NiTi austenitic,B19'-NiTi martensitic and β-Nb phases,B2→ B19' stress-induced martensitic(SIM) transformation and tensile plastic deformation of β-Nb phase.During unloading,the deformation behavior involved in Nb/NiTi composite includes the elastic recovery of B2-NiTi austenitic,B19'-NiTi martensitic and β-Nb phases,reverse phase transformation B19'→B2 and compressive deformation of p-Nb phase.The martensitic transformation in this composite is almost reversible and occurs in a localized manner.These results might contribute to a comprehensive understanding of the deformation mechanism involved in Nb/NiTi composite and shed some light on design and development of novel composites with a combination of good biocompatibility and excellent superelasticity for biomedical applications. 相似文献
96.
Rongrong Luo Lei Chen Xingxing Song Xin Zhang Wenhao Xu Dongyang Han Jianyu Zuo Wen Hu Yan Shi Yajie Cao Runwen Ma Chengcheng Liu Changlin Xu Zixin Li Xun Li 《International journal of molecular sciences》2022,23(15)
Gonadotropin-inhibitory hormone (GnIH) is a reproductive inhibitor and an endogenous orexigenic neuropeptide that may be involved in energy homeostasis and reproduction. However, whether GnIH is a molecular signal link of metabolism and the reproductive system, and thus, regulates reproductive activity as a function of the energy state, is still unknown. In the present study, we investigated the involvement of GnIH in glycolipid metabolism and reproduction in vivo, and in the coupling between these two processes in the testis level. Our results showed that chronic intraperitoneal injection of GnIH into male mice not only increased food intake and altered meal microstructure but also significantly elevated body mass due to the increased mass of liver and epididymal white adipose tissue (eWAT), despite the loss of testicular weight. Furthermore, chronic intraperitoneal administration of GnIH to male mice resulted in obesity-related glycolipid metabolic derangements, showing hyperlipidemia, hyperglycemia, glucose intolerance, and insulin resistance through changes in the expression of glucose and lipid metabolism-related genes in the pancreas and eWAT, respectively. Interestingly, the expression of GnIH and GPR147 was markedly increased in the testis of mice under conditions of energy imbalance, such as fasting, acute hypoglycemia, and hyperglycemia. In addition, chronic GnIH injection markedly inhibited glucose and lipid metabolism of mice testis while significantly decreasing testosterone synthesis and sperm quality, inducing hypogonadism. These observations indicated that orexigenic GnIH triggers hyperphagia-induced obesity-related metabolic derangements and hypogonadism in male mice, suggesting that GnIH is an emerging candidate for coupling metabolism and fertility by involvement in obesity and metabolic disorder-induced reproductive dysfunction of the testes. 相似文献
97.
98.
为了解决路侧停车位数目检测问题,本文采用基于图像识别的方法,将复杂的动态视频信息转化为简单的静态图像信息.首先,采用中值滤波、伽马变换和形态学处理等方法对感兴趣区域进行图像预处理;接着采用基于PPHT与直线聚类的方法检测停车位标记线;其次,采用二次方递减图像拼接的方法将该路段所有停车位拼接到一幅图像上,既防止了停车位数... 相似文献
99.
100.
Yayao LI Yue WANG Lei YIN Wen HUANG Wenbing PENG Yiyue ZHU Kun WANG Deren YANG Xiaodong PI 《中国科学:信息科学(英文版)》2021,(6):184-191
With advances in Si-based technology infrastructures and the rapid integration of Si-based op-toelectronics,Si-based optoelectronic synaptic devices have the po... 相似文献