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   1898篇
  免费   226篇
  国内免费   85篇
电工技术   115篇
综合类   248篇
化学工业   147篇
金属工艺   93篇
机械仪表   218篇
建筑科学   95篇
矿业工程   81篇
能源动力   58篇
轻工业   216篇
水利工程   84篇
石油天然气   28篇
武器工业   69篇
无线电   237篇
一般工业技术   121篇
冶金工业   67篇
原子能技术   12篇
自动化技术   320篇
  2024年   2篇
  2023年   20篇
  2022年   49篇
  2021年   51篇
  2020年   50篇
  2019年   46篇
  2018年   38篇
  2017年   43篇
  2016年   54篇
  2015年   79篇
  2014年   77篇
  2013年   112篇
  2012年   181篇
  2011年   182篇
  2010年   134篇
  2009年   153篇
  2008年   174篇
  2007年   185篇
  2006年   184篇
  2005年   120篇
  2004年   84篇
  2003年   45篇
  2002年   35篇
  2001年   40篇
  2000年   40篇
  1999年   12篇
  1998年   3篇
  1997年   5篇
  1996年   2篇
  1995年   1篇
  1994年   3篇
  1991年   1篇
  1987年   1篇
  1982年   2篇
  1980年   1篇
排序方式: 共有2209条查询结果,搜索用时 15 毫秒
1.
Preoperative chemoradiation therapy (CRT) is becoming the standard treatment for patients with locally advanced rectal cancer. However, individual differences in response to treatment range from a complete response to complete resistance. Predicting the tumor response to radiotherapy may improve the efficacy of radiotherapy. This review mainly summarizes recent studies about the molecular biomarkers that can predict the response to radiotherapy in rectal cancer. These studies have indicated that the molecular markers involved in the response to radiotherapy mainly include genes related to radiosensitivity, cancer stem cell-related markers, non-coding RNAs (ncRNAs), single-nucleotide polymorphisms (SNPs) and gene methylation, and other factors including carcinoembryonic antigen (CEA) level, anemia, lymphocytes, and signaling pathways. Many of these identified markers are mainly associated with DNA repair, apoptosis, and cell cycle, but some involve unknown cell mechanisms. We speculate that predictors of radiotherapy response may involve combinations of multiple molecular biomarkers that may be useful for the development of individualized therapy for rectal cancer patients.  相似文献   
2.
用同向啮合双螺杆挤出机对废旧轮胎全胎胶粉进行剪切脱硫,制备高性能环保再生橡胶,考察挤出工艺、补强树脂和软化剂的种类与用量对再生橡胶性能的影响。结果表明:挤出最佳工艺参数为机筒第1—13区温度为140/140/70/190/130/120/110/110/100/110/100/90/80℃,螺杆转速为140 r·min~(-1);与添加植物系软化剂的再生橡胶相比,添加矿物系软化剂固体无味油的再生橡胶物理性能更好;添加4份古马隆树脂作为补强剂,10份固体无味油作为软化剂,制备的再生橡胶物理性能最好。  相似文献   
3.
There are two major challenges faced by modern society: energy security, and lowering carbon dioxide gas emissions. Thermo-active diaphragm walls have a large potential to remedy one of these problems, since they are a renewable energy technology that uses underground infrastructure as a heat exchange medium. However, extensive research is required to determine the effects of cyclic heating and cooling on their geotechnical and structural performance. In this paper, a series of detailed finite element analyses are carried out to capture the fully coupled thermo-hydro-mechanical response of the ground and diaphragm wall. It is demonstrated that the thermal operation of the diaphragm wall causes changes in soil temperature, thermal expansion/shrinkage of pore water, and total stress applied on the diaphragm wall. These, in turn, cause displacements of the diaphragm wall and variations of the bending moments. However, these effects on the performance of diaphragm wall are not significant. The thermally induced bending strain is mainly governed by the temperature differential and uneven thermal expansion/shrinkage across the wall.  相似文献   
4.
利用微生物吸附法回收铂族金属(PGMs)有较大的应用前景,然而利用基因工程手段改造微生物胞外金属结合基团,进而提升微生物的吸附量与特异性仍是一项挑战。本研究利用微生物表面展示技术,在大肠杆菌(Escherichia coli,简写为E. coli)BL21菌株外膜上展示了不同长度的金属结合肽(EC10、EC20、EC30),并解析了其对钯(Pd(II))的吸附行为。结果表明,在E.coli BL21表面展示不同长度金属结合肽均能增强其对Pd(II)的吸附量。其中,表面展示了EC20的菌株(简写为E. coli EC20)吸附量最高,为144.25 mg/g,是未进行表面展示菌株的1.14倍;E. coli BL21和E. coli EC20均能够从含多种金属离子的工业废水中选择性吸附Pd(II)和Pt(IV),两株菌对Pd(II)吸附率分别为96.2%和99.0%。以上研究表明利用表面展示技术增加微生物外膜金属结合基团是一种有效提升微生物吸附能力的手段。  相似文献   
5.
Spinal muscular atrophy (SMA) is an autosomal recessive hereditary neuromuscular disease. Exon 7 and 8 of survival of motor neuron 1 (SMN1) gene or only exon 7 homology deletion leads to the failure to produce a full-length SMN gene. The copy number of SMN2 gene with high homology of SMN1 affects the degree of disease and was the target gene for targeting therapy, in which splicing silencer in intron 7 was the key to suppress the inclusion of exon 7. In this study, we projected to use CRISPR/Case 9 for the targeted editing of intronic-splicing silencer (ISS) sequence to promote the inclusion of SMN2 exon 7 and increase the production of SMN2 full-length (FL) gene expression. It happens that there was a protospacer adjacent motif (PAM) at one end of the ISS sequence according to the design of sgRNA. The recombinant vector of sgRNA HSMN2 CRISPR/Case 9 was constructed and transfected into HEK293 cells. Sequencing results showed that the ISS sequence could be edited accurately and targeting in the predicted direction, in which deleting small fragments, inserting small amounts and mutation. Quantitative analysis of RT-PCR products by restriction enzyme of DdeI digestion showed that the FL of SMN2 increased by 8% (P < 0.05). In the primary cultured chondrocytes of SMA mice, in which sgRNA HSMN2 CRISPR/Case9 recombinant vector transfection could increase the SMN2 FL gene by 23% (P < 0.05) and significantly improve SMN protein levels (P < 0.05). CRISPR/Case 9 is an effective tool for gene editing and therapy of hereditary diseases, but it is rarely reported in the treatment of SMA diseases. This study shows that CRISPR/Case 9 was first used for the precision target of ISS sequence editing, which can effectively promote the production of SMN2 FL gene expressions, in which there was an important clinical reference value.  相似文献   
6.
The rights and interests value of mineral resources includes the prospecting rights value and the mining rights value. The mining rights value is made up of the mineral resources value and the compensation value based on the in puts of capitals and labors indifferent exploration stage, the prospecting rights value should be equal to exploration differential rent of resources. According to the stage characteristic of mineral resources exploration and development, the initial evaluating methods and models are used to evaluate the prospecting rights and mining rights value.  相似文献   
7.
基于模糊小波神经网络的永磁直线同步电机故障诊断   总被引:1,自引:0,他引:1  
在分析永磁直线同步电机故障的基础上,采用小波基函数作为模糊隶属函数,将模糊控制与神经网络相结合,建立模糊小波神经网络模型,实现对永磁直线同步电机的故障诊断。针对BP算法的不足,使用混合学习算法训练网络,优化了网络参数。仿真结果表明该方法是很有效的。  相似文献   
8.
从零件加工、系统工况等方面分析了发生液压滑阀卡死现象的原因,针对不同成因,提出了行之有效的解决方案。  相似文献   
9.
面对新技术与新经济,土木专业作为传统工科专业有升级转型为新工科的必要性与迫切性。为助推新型土木工程专业个性化人才培养,河海大学土木与交通学院基于推进学科交融、跨界整合能力培养的发展主旨进行了独特的专业学生组织交流平台建设,在人的全面发展、现代认知学习、建构主义、生涯发展等理论的基础上,以国际竞赛、国际年会、讲堂制度和三高体系为载体,构建了ASCE国际学生组织河海大学分会,以激发学生主体作用,推进新工科建设。  相似文献   
10.
随着“西部大开发”等国家战略的实施以及这些地区城市建设的发展,许多公路、铁路等交通都需要源于或穿越这些岩溶洞穴地区,随即面临因岩溶洞穴的塌陷所导致的路基失稳与破坏问题。本文依托昌金高速某段的岩溶塌陷进行了数值模拟,并结合塌陷段模拟分析所得的岩土体参数对邻近未塌陷段的二个处治方案进行了处治工程效果的数值模拟分析,为方案比选提供依据,对岩溶洞穴地区道路建设具有一定的指导与借鉴意义。  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