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   8944篇
  免费   1648篇
  国内免费   931篇
化学   5956篇
晶体学   86篇
力学   730篇
综合类   65篇
数学   1128篇
物理学   3558篇
  2024年   38篇
  2023年   183篇
  2022年   307篇
  2021年   349篇
  2020年   348篇
  2019年   323篇
  2018年   294篇
  2017年   293篇
  2016年   432篇
  2015年   425篇
  2014年   465篇
  2013年   643篇
  2012年   755篇
  2011年   828篇
  2010年   553篇
  2009年   529篇
  2008年   612篇
  2007年   477篇
  2006年   517篇
  2005年   375篇
  2004年   314篇
  2003年   253篇
  2002年   234篇
  2001年   201篇
  2000年   190篇
  1999年   190篇
  1998年   182篇
  1997年   173篇
  1996年   169篇
  1995年   137篇
  1994年   124篇
  1993年   114篇
  1992年   93篇
  1991年   70篇
  1990年   75篇
  1989年   62篇
  1988年   44篇
  1987年   34篇
  1986年   34篇
  1985年   22篇
  1984年   18篇
  1983年   14篇
  1982年   15篇
  1981年   3篇
  1980年   7篇
  1979年   2篇
  1975年   1篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Sun  Xiaodong  Ding  Wen  Chen  Cheng  Yu  Tao  Chen  Qin  Yang  Ke 《Chromatographia》2021,84(5):499-505
Chromatographia - In this study, a poly(glycidyl methacrylate) nanoparticle (PGMA NP)-coated column system with two antibiotics as selector was constructed for enantioseparation. The PGMA NP...  相似文献   
52.
By solving the quantum Vlasov equation, the dynamically assisted pair production for scalar quantum electrodynamics (QED) is investigated. It is verified that this mechanism still holds true for boson pair production. Two combinations of two electric fields having different time scales under various time delays are considered; it is found that the oscillations of the momentum spectrum and the number density of created bosons decrease with increasing time delay, and the latter has a maximum value when the time delay equals zero. Furthermore, the differences in vacuum pair production between bosons and fermions are also studied, and they are helpful for distinguishing the created bosons from fermions.  相似文献   
53.
Benzo(a)pyrene is a chemical produced during the process of making fried, roasted, and smoked foods. It remains unclear whether benzo(a)pyrene affects the early development of human organs. In this study, we used the transgenic zebrafish line Tg(wt1b:GFP) as a model to assess benzo(a)pyrene-induced kidney malformation. By soaking zebrafish embryos in benzo(a)pyrene at various doses (2, 20, and 200 ppb), only a minor effect on the survival rate was detected (0 ppb: 97.8 ± 1.9 %; 2–200 ppb: 89.1 ± 5.8–91.5 ± 8.3 %). However, benzo(a)pyrene significantly affected the development of the kidney (malformation rates ranges from 50.0 ± 3.5 to 77.4 ± 5.3 %). Various abnormalities, such as unusual curving of pronephric tubes, swollen glomerulus, and incomplete development of pronephric ducts, were observed. This study provides a rapid and effective protocol for the evaluation of the notable effects of benzo(a)pyrene on embryonic kidney development.  相似文献   
54.
The spatial arrangement of chromosome within the nucleus is linked to genome function and gene expression regulation. Existing genome-wide mapping methods often rely on chemically crosslinking DNA with protein baits, which raises concerns of artifacts being introduced during cell fixation. By genetically targeting a photosensitizer protein to specific subnuclear locations, we achieved blue-light-activated labeling of local DNA with a bioorthogonal functional handle for affinity purification and sequence identification through next-generation sequencing. When applied to the nuclear lamina in human embryonic kidney 293T cells, it revealed lamina-associated domains (LADs) that cover 37.6 % of the genome. These LADs overlap with heterochromatin hallmarks and are depleted with CpG islands. This simple labeling method avoids the harsh treatment of chemical crosslinking and is generally applicable to the genome-wide high-resolution mapping of the spatial chromosome organization in living cells.  相似文献   
55.
Exosomes hold great potential in therapeutic development. However, native exosomes usually induce insufficient effects in vivo and simply act as drug delivery vehicles. Herein, we synthesize responsive exosome nano‐bioconjugates for cancer therapy. Azide‐modified exosomes derived from M1 macrophages are conjugated with dibenzocyclooctyne‐modified antibodies of CD47 and SIRPα (aCD47 and aSIRPα) through pH‐sensitive linkers. After systemic administration, the nano‐bioconjugates can actively target tumors through the specific recognition between aCD47 and CD47 on the tumor cell surface. In the acidic tumor microenvironment, the benzoic‐imine bonds of the nano‐bioconjugates are cleaved to release aSIRPα and aCD47 that can, respectively, block SIRPα on macrophages and CD47, leading to abolished “don't eat me” signaling and improved phagocytosis of macrophages. Meanwhile, the native M1 exosomes effectively reprogram the macrophages from pro‐tumoral M2 to anti‐tumoral M1.  相似文献   
56.
Zhao  X. H.  Yi  S. H.  Mi  Q.  Hu  Y. F.  Ding  H. L. 《Fluid Dynamics》2022,57(5):686-696
Fluid Dynamics - Both numerical methods and wind tunnel tests were used to reduce skin friction for a hypersonic body. A hypersonic cone was tested under three different free-stream flow...  相似文献   
57.
Liouville first passage percolation(LFPP) with the parameter ξ > 0 is the family of random distance functions ■ on the plane obtained by integrating ■along paths, where ■ is a smooth mollification of the planar Gaussian free field. Recent works have shown that for all ξ > 0, the LFPP metrics,appropriately re-scaled, admit non-trivial subsequential limiting metrics. In the case ξ < ξcrit≈ 0.41, it has been shown that the subsequential limit is unique and defines a metric on γ-Liouville q...  相似文献   
58.
Guanidinium (GA) cations are intentionally introduced in MAPbl3 perovskite by considering its potential capability of stabilizing the material through plenty of...  相似文献   
59.
低压供热技术具有安全系数高和节能降耗等优势,因而成为石化稠油长输管线、风力发电叶片冬季防覆冰和室内供暖等领域的研究热点之一。本文制备了一系列低压供热涂层材料,研究不同碳功能填料对涂层发热速率、发热功率及最高发热温度的影响规律,并揭示石墨烯和碳纤维对提升涂层材料热性能的协同作用。其中石墨烯纳米片的还原程度对材料热性能具有重要影响,降低其表面官能团密度对提升涂层供热特性具有促进作用,但是官能团密度过低会导致石墨烯纳米片的团聚现象,引起涂层发热不均匀。加入适量碳纤维可以提高石墨烯的均匀分散性,提升发热速率。优化石墨烯纳米片和碳纤维的比例后,采用24V电压驱动时,涂层材料的发热速率达到7.1℃·s-1,功率密度为800W·m-2,最高发热温度为124℃。  相似文献   
60.
Viral infections pose a persistent threat to human health. The relentless epidemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global health problem, with millions of infections and fatalities so far. Traditional approaches such as random screening and optimization of lead compounds by organic synthesis have become extremely resource- and time-consuming. Various modern innovative methods or integrated paradigms are now being applied to drug discovery for significant resistance in order to simplify the drug process. This review provides an overview of newly emerging antiviral strategies, including proteolysis targeting chimera (PROTAC), ribonuclease targeting chimera (RIBOTAC), targeted covalent inhibitors, topology-matching design and antiviral drug delivery system. This article is dedicated to Prof. Dr. Erik De Clercq, an internationally renowned expert in the antiviral drug research field, on the occasion of his 80th anniversary.  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