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   1443991篇
  免费   27212篇
  国内免费   6975篇
电工技术   33832篇
综合类   6458篇
化学工业   253456篇
金属工艺   63681篇
机械仪表   41192篇
建筑科学   42318篇
矿业工程   11428篇
能源动力   49768篇
轻工业   106814篇
水利工程   14592篇
石油天然气   36759篇
武器工业   153篇
无线电   194512篇
一般工业技术   275030篇
冶金工业   147464篇
原子能技术   34034篇
自动化技术   166687篇
  2021年   14513篇
  2020年   11789篇
  2019年   14555篇
  2018年   15535篇
  2017年   14870篇
  2016年   21099篇
  2015年   17306篇
  2014年   28620篇
  2013年   87656篇
  2012年   34665篇
  2011年   46914篇
  2010年   42224篇
  2009年   50825篇
  2008年   43957篇
  2007年   41150篇
  2006年   44111篇
  2005年   38914篇
  2004年   41004篇
  2003年   40209篇
  2002年   37963篇
  2001年   34156篇
  2000年   32205篇
  1999年   31347篇
  1998年   36993篇
  1997年   33709篇
  1996年   30680篇
  1995年   28995篇
  1994年   27263篇
  1993年   27161篇
  1992年   25365篇
  1991年   22427篇
  1990年   22961篇
  1989年   21870篇
  1988年   20327篇
  1987年   18727篇
  1986年   18152篇
  1985年   21527篇
  1984年   21860篇
  1983年   19816篇
  1982年   18880篇
  1981年   18934篇
  1980年   17637篇
  1979年   18193篇
  1978年   17454篇
  1977年   17118篇
  1976年   17825篇
  1975年   15756篇
  1974年   15312篇
  1973年   15403篇
  1972年   12938篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
91.
Theoretical Foundations of Chemical Engineering - Using gas–liquid chromatography, the activity coefficients upon the infinite dilution of the components of the reaction mixture for obtaining...  相似文献   
92.
Bone formation starts near the end of the embryonic stage of development and continues throughout life during bone modeling and growth, remodeling, and when needed, regeneration. Bone-forming cells, traditionally termed osteoblasts, produce, assemble, and control the mineralization of the type I collagen-enriched bone matrix while participating in the regulation of other cell processes, such as osteoclastogenesis, and metabolic activities, such as phosphate homeostasis. Osteoblasts are generated by different cohorts of skeletal stem cells that arise from different embryonic specifications, which operate in the pre-natal and/or adult skeleton under the control of multiple regulators. In this review, we briefly define the cellular identity and function of osteoblasts and discuss the main populations of osteoprogenitor cells identified to date. We also provide examples of long-known and recently recognized regulatory pathways and mechanisms involved in the specification of the osteogenic lineage, as assessed by studies on mice models and human genetic skeletal diseases.  相似文献   
93.
Protection of Metals and Physical Chemistry of Surfaces - Three nonionic surfactants molecules (NS) derived from a fused pyridine characterized by IR and 1HNMR spectra were synthesized and examined...  相似文献   
94.
Fluorescent fusion proteins are powerful tools for studying biological processes in living cells, but universal application is limited due to the voluminous size of those tags, which might have an impact on the folding, localization or even the biological function of the target protein. The designed biocatalyst trypsiligase enables site-directed linkage of small-sized fluorescence dyes on the N terminus of integral target proteins located in the outer membrane of living cells through a stable native peptide bond. The function of the approach was tested by using the examples of covalent derivatization of the transmembrane proteins CD147 as well as the EGF receptor, both presented on human HeLa cells. Specific trypsiligase recognition of the site of linkage was mediated by the dipeptide sequence Arg-His added to the proteins’ native N termini, pointing outside the cell membrane. The labeling procedure takes only about 5 minutes, as demonstrated for couplings of the fluorescence dye tetramethyl rhodamine and the affinity label biotin as well.  相似文献   
95.
Abnormal levels of glutathione, a cellular antioxidant, can lead to a variety of diseases. We have constructed a near-infrared ratiometric fluorescent probe to detect glutathione concentrations in biological samples. The probe consists of a coumarin donor, which is connected through a disulfide-tethered linker to a rhodamine acceptor. Under the excitation of the coumarin donor at 405 nm, the probe shows weak visible fluorescence of the coumarin donor at 470 nm and strong near-infrared fluorescence of the rhodamine acceptor at 652 nm due to efficient Forster resonance energy transfer (FRET) from the donor to the acceptor. Glutathione breaks the disulfide bond through reduction, which results in a dramatic increase in coumarin fluorescence and a corresponding decrease in rhodamine fluorescence. The probe possesses excellent cell permeability, biocompatibility, and good ratiometric fluorescence responses to glutathione and cysteine with a self-calibration capability. The probe was utilized to ratiometrically visualize glutathione concentration alterations in HeLa cells and Drosophila melanogaster larvae.  相似文献   
96.
Individually, photoredox catalysis (PC) and photodynamic therapy (PDT) are well-established concepts that have experienced a remarkable resurgence in recent years, leading to significant progress in organic synthesis for PC and clinical approval of anticancer drugs for PDT. But, very recently, new photoredox catalyst systems based on Ir(III) and Ru(II) complexes have garnered significant interest because they can simultaneously be used as PDT agents apart from their demonstrated PC activity. This highlight discusses the unique PC behavior of emerging Ir(III)- and Ru(II)-based systems while also examining their potential PDT activity in cancer treatment.  相似文献   
97.
In recent decades, dysregulation of proteases and atypical proteolysis have become increasingly recognized as important hallmarks of cancer, driving community-wide efforts to explore the proteolytic landscape of oncologic disease. With more than 100 proteases currently associated with different aspects of cancer development and progression, there is a clear impetus to harness their potential in the context of oncology. Advances in the protease field have yielded technologies enabling sensitive protease detection in various settings, paving the way towards diagnostic profiling of disease-related protease activity patterns. Methods including activity-based probes and substrates, antibodies, and various nanosystems that generate reporter signals, i.e., for PET or MRI, after interaction with the target protease have shown potential for clinical translation. Nevertheless, these technologies are costly, not easily multiplexed, and require advanced imaging technologies. While the current clinical applications of protease-responsive technologies in oncologic settings are still limited, emerging technologies and protease sensors are poised to enable comprehensive exploration of the tumor proteolytic landscape as a diagnostic and therapeutic frontier. This review aims to give an overview of the most relevant classes of proteases as indicators for tumor diagnosis, current approaches to detect and monitor their activity in vivo, and associated therapeutic applications.  相似文献   
98.
Silicon - Lodging resistance in upland rice requires adequate knowledge of the mechanical basis of culm morphological traits (CMTs) with potential for improved structural integrity under...  相似文献   
99.
介绍了水泥厂增湿管道的几种典型结构,并分析了各种结构的优缺点,在最后给出了设计时选用的原则和建议。  相似文献   
100.
Combustion, Explosion, and Shock Waves - A VISAR multipoint laser interferometer is used to study a detonation wave structure in mixtures of tetranitromethane with methanol and nitrobenzene. A poor...  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