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   50875篇
  免费   15667篇
  国内免费   465篇
电工技术   1300篇
综合类   457篇
化学工业   18809篇
金属工艺   1019篇
机械仪表   1475篇
建筑科学   2374篇
矿业工程   261篇
能源动力   1337篇
轻工业   8080篇
水利工程   494篇
石油天然气   352篇
武器工业   65篇
无线电   9312篇
一般工业技术   13383篇
冶金工业   1777篇
原子能技术   173篇
自动化技术   6339篇
  2024年   20篇
  2023年   198篇
  2022年   266篇
  2021年   667篇
  2020年   1761篇
  2019年   3443篇
  2018年   3442篇
  2017年   3769篇
  2016年   4290篇
  2015年   4359篇
  2014年   4457篇
  2013年   5818篇
  2012年   3544篇
  2011年   3291篇
  2010年   3371篇
  2009年   3290篇
  2008年   2783篇
  2007年   2572篇
  2006年   2341篇
  2005年   1990篇
  2004年   1822篇
  2003年   1784篇
  2002年   1694篇
  2001年   1442篇
  2000年   1346篇
  1999年   375篇
  1998年   560篇
  1997年   388篇
  1996年   275篇
  1995年   237篇
  1994年   204篇
  1993年   191篇
  1992年   103篇
  1991年   140篇
  1990年   102篇
  1989年   87篇
  1988年   70篇
  1987年   70篇
  1986年   59篇
  1985年   50篇
  1984年   51篇
  1983年   29篇
  1982年   30篇
  1981年   37篇
  1980年   29篇
  1979年   21篇
  1978年   23篇
  1977年   22篇
  1976年   23篇
  1973年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Multimedia Tools and Applications - Individual tooth segmentation and identification from cone-beam computed tomography images are preoperative prerequisites for orthodontic treatments. Instance...  相似文献   
2.
3.

Hydrological drought is assessed through river flow, which depends on river runoff and water withdrawal. This study proposed a framework to project future hydrological droughts considering agricultural water withdrawal (AWW) for shared socioeconomic pathway (SSP) scenarios. The relationship between AWW and potential evapotranspiration (PET) was determined using a deep belief network (DBN) model and then applied to estimate future AWW using projections of the twelve global climate models (GCMs). 12 GCMs were bias-corrected using the quantile mapping method, climate variables were generated, and river flow was estimated using the soil and water assessment tool (SWAT) model. The standardized runoff index (SRI) was used to project the changes in hydrological drought characteristics. The results revealed a higher occurrence of severe droughts in the future. Droughts would be more frequent in the near future (2021–2060) than in the far future (2061–2100) and more severe when AWW is considered. Droughts would also be more severe for SSP5-8.5 than for SSP2-4.5. The study revealed that the increased PET due to rising temperatures is the primary cause of the increased drought frequency and severity. The AWW will accelerate the drought severities in the future in the Yeongsan River basin.

  相似文献   
4.
5.
Helicobacter pylori infection is the etiology of several gastric-related diseases including gastric cancer. Cytotoxin associated gene A (CagA), vacuolating cytotoxin A (VacA) and α-subunit of urease (UreA) are three major virulence factors of H. pylori, and each of them has a distinct entry pathway and pathogenic mechanism during bacterial infection. H. pylori can shed outer membrane vesicles (OMVs). Therefore, it would be interesting to explore the production kinetics of H. pylori OMVs and its connection with the entry of key virulence factors into host cells. Here, we isolated OMVs from H. pylori 26,695 strain and characterized their properties and interaction kinetics with human gastric adenocarcinoma (AGS) cells. We found that the generation of OMVs and the presence of CagA, VacA and UreA in OMVs were a lasting event throughout different phases of bacterial growth. H. pylori OMVs entered AGS cells mainly through macropinocytosis/phagocytosis. Furthermore, CagA, VacA and UreA could enter AGS cells via OMVs and the treatment with H. pylori OMVs would cause cell death. Comparison of H. pylori 26,695 and clinical strains suggested that the production and characteristics of OMVs are not only limited to laboratory strains commonly in use, but a general phenomenon to most H. pylori strains.  相似文献   
6.
Several immune checkpoint molecules and immune targets in leukemic cells have been investigated. Recent studies have suggested the potential clinical benefits of immuno-oncology (IO) therapy against acute myeloid leukemia (AML), especially targeting CD33, CD123, and CLL-1, as well as immune checkpoint inhibitors (e.g., anti-PD (programmed cell death)-1 and anti-CTLA4 (cytotoxic T-lymphocyte-associated protein 4) antibodies) with or without conventional chemotherapy. Early-phase clinical trials of chimeric antigen receptor (CAR)-T or natural killer (NK) cells for relapsed/refractory AML showed complete remission (CR) or marked reduction of marrow blasts in a few enrolled patients. Bi-/tri-specific antibodies (e.g., bispecific T-cell engager (BiTE) and dual-affinity retargeting (DART)) exhibited 11–67% CR rates with 13–78% risk of cytokine-releasing syndrome (CRS). Conventional chemotherapy in combination with anti-PD-1/anti-CTLA4 antibody for relapsed/refractory AML showed 10–36% CR rates with 7–24 month-long median survival. The current advantages of IO therapy in the field of AML are summarized herein. However, although cancer vaccination should be included in the concept of IO therapy, it is not mentioned in this review because of the paucity of relevant evidence.  相似文献   
7.
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production.  相似文献   
8.
9.
艾俊哲  谢郢  周可心  池伸 《广东化工》2022,49(3):186-188
胶体电泳速度测定实验是大学物理化学实验中一个重要的综合性教学实验.本文针对该实验中存在半透膜制作不稳定、渗析时间过长、电泳现象不明显、胶体/辅助液界面不清晰等问题.从胶体浓度、电极电压、半透膜、稳定剂四个方面进行了改进.结果表明,胶体界面移动距离,胶体/辅助液界面的清晰程度都有很大的改善,大大提高了实验的体验感.  相似文献   
10.
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