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   23497篇
  免费   898篇
  国内免费   131篇
化学   15419篇
晶体学   240篇
力学   703篇
数学   2286篇
物理学   5878篇
  2023年   131篇
  2022年   104篇
  2021年   514篇
  2020年   445篇
  2019年   448篇
  2018年   398篇
  2017年   373篇
  2016年   708篇
  2015年   609篇
  2014年   853篇
  2013年   1484篇
  2012年   1772篇
  2011年   1997篇
  2010年   1270篇
  2009年   1096篇
  2008年   1673篇
  2007年   1461篇
  2006年   1498篇
  2005年   1263篇
  2004年   1105篇
  2003年   910篇
  2002年   735篇
  2001年   495篇
  2000年   407篇
  1999年   256篇
  1998年   159篇
  1997年   172篇
  1996年   234篇
  1995年   181篇
  1994年   193篇
  1993年   198篇
  1992年   151篇
  1991年   119篇
  1990年   115篇
  1989年   98篇
  1988年   64篇
  1987年   72篇
  1986年   49篇
  1985年   77篇
  1984年   56篇
  1983年   47篇
  1982年   69篇
  1981年   64篇
  1979年   50篇
  1978年   49篇
  1977年   37篇
  1976年   42篇
  1975年   40篇
  1974年   38篇
  1973年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Monolayers of periodic porous Co3O4 inverse opal (IO) thin films for gas‐sensor applications were prepared by transferring cobalt‐solution‐dipped polystyrene (PS) monolayers onto sensor substrates and subsequent removal of the PS template by heat treatment. Monolayer Co3O4 IO thin films having periodic pores (d≈500 nm) showed a high response of 112.9 to 5 ppm C2H5OH at 200 °C with low cross‐responses to other interfering gases. Moreover, the selective detection of xylene and methyl benzenes (xylene+toluene) could be achieved simply by tuning the sensor temperature to 250 and 275 °C, respectively, so that multiple gases can be detected with a single chemiresistor. Unprecedentedly high ethanol response and temperature‐modulated control of selectivity with respect to ethanol, xylene, and methyl benzenes were attributed to the highly chemiresistive IO nanoarchitecture and to the tuned catalytic promotion of different gas‐sensing reactions, respectively. These well‐ordered porous nanostructures could have potential in the field of high‐performance gas sensors based on p‐type oxide semiconductors.  相似文献   
43.
44.
The properties of eumelanin‐like particles (EMPs) and pheomelanin‐like particles (PMPs) in regulating the process of amyloid formation of amyloid‐beta 42 (Aβ42) were examined. EMPs and PMPs are effective both in interfering with amyloid aggregation of Aβ42 and in remodeling matured Αβ42 fibers. The results suggest that some (but not all) molecular species consisting of melanin‐like particles (MPs) are responsible for their inhibiting property toward amyloid formation, and the influence is likely manifested by long‐range interactions. Incubating preformed Aβ42 fibers with catechols or MPs leads to the formation of mesh‐like, interconnected Aβ42 fibers encapsulated with melanin‐like material. MPs are kinetically more effective than catechol monomers in this process, and a detailed investigation reveals that 4,5‐dihydroxyindole, a major intermediate in the formation of melanin‐like species, and its derivatives are mainly responsible for remodeling amyloid fibers.  相似文献   
45.
Multimodal approaches combined with various nanomaterials and advanced techniques have been developed for synergistic cancer treatment. Among various therapies, conventional chemotherapy (CHT) is a direct cancer treatment that can produce unintended side effects due to nonspecific action on both the tumor and normal cells; patient-friendly photothermal therapy (PTT) may be able to treat embedded tumors in vital regions with minimal invasion but does not guarantee complete removal of cancers. However, the combination of CHT-PTT may provide a promising tool for direct cancer treatment with minimal side effects. In this regard, nanostructured materials, such as gold nanorods with tuned size and surface characteristics, are key components designed to enhance the heating capacity and active or passive delivery of drugs to the tumor site. In this review, the pioneering work synergizing CHT and PTT is summarized, and the current state-of-the-art in the development of inorganic and organic nanocomposites for combinational therapy is described.  相似文献   
46.
47.
48.
In this paper, we evaluated the particle dispersion degree of alumina slurry containing a dispersant by solvent nuclear magnetic resonance (NMR) relaxation and compared it with conventional dispersion evaluation methods such as viscosity, particle size, and sedimentation height measurements. The dispersion of slurry was evaluated via numerical analysis of the transverse relaxation time (T2). The effect of the changes in different parameters of the experiment in terms of milling time, solid loading, and dispersant amount was investigated by NMR relaxation as well as conventional methods. The results of NMR relaxation measurements revealed that T2 correlates well with other dispersion evaluation methods; thus, it is an efficient technique to evaluate the dispersion of alumina slurry, specifically, when studying the effect of the change in milling time and dispersion amount.  相似文献   
49.
Journal of Solution Chemistry - A polemic is given regarding the apparent molal volumes reported in the recent paper by Mohammadi and coworkers. The authors’ calculated apparent molal volumes...  相似文献   
50.
Through accumulation, mercury contamination in aquatic systems still poses serious health risks despite the strict regulations on drinking water and industrial discharge. One effective strategy against this is adsorptive removal, in which a suitably functionalized porous material is added to water treatment protocols. Thiol (SH) group-grafted structures perform commendably; however, insufficient attention is paid to the cost, scalability, and reusability or how the arrangement of sulfur atoms could affect the HgII binding strength. We used an inexpensive and scalable porous covalent organic polymer (COP-130) to systematically introduce thiol functional groups with precise chain lengths and sulfur content. Thiol-functionalized COP-130 demonstrates enhanced wettability and excellent HgII uptake of up to 936 mg g−1, with fast kinetics and exceptionally high selectivity. These Hg adsorbents are easily regenerated with HCl and can be used at least six times without loss of capacity even after treatment with strong acid, a rare performance in the domain of Hg-removal research.  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