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   251725篇
  免费   3230篇
  国内免费   989篇
化学   136794篇
晶体学   3773篇
力学   10368篇
综合类   5篇
数学   28260篇
物理学   76744篇
  2021年   1949篇
  2020年   2117篇
  2019年   2449篇
  2018年   2909篇
  2017年   2751篇
  2016年   4399篇
  2015年   2997篇
  2014年   4438篇
  2013年   12169篇
  2012年   8834篇
  2011年   10696篇
  2010年   7090篇
  2009年   6885篇
  2008年   9437篇
  2007年   9520篇
  2006年   8650篇
  2005年   8107篇
  2004年   7161篇
  2003年   6376篇
  2002年   6271篇
  2001年   7271篇
  2000年   5406篇
  1999年   4275篇
  1998年   3583篇
  1997年   3627篇
  1996年   3331篇
  1995年   3160篇
  1994年   2982篇
  1993年   3013篇
  1992年   3326篇
  1991年   3357篇
  1990年   3170篇
  1989年   3131篇
  1988年   3187篇
  1987年   3059篇
  1986年   2949篇
  1985年   4013篇
  1984年   4178篇
  1983年   3416篇
  1982年   3774篇
  1981年   3661篇
  1980年   3534篇
  1979年   3568篇
  1978年   3793篇
  1977年   3618篇
  1976年   3824篇
  1975年   3399篇
  1974年   3528篇
  1973年   3829篇
  1972年   2338篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
71.
Prostate cancer is a highly prevalent disease and ranks second among malignant neoplasms that affect men around the world, behind lung cancer alone. Trace elements are very important and are involved in many cellular processes. The X-ray microfluorescence technique is an advanced tool of high spatial resolution, sensitivity, multielemental analysis, and nondestructiveness for trace element study. This study aimed to investigate the elemental distribution in spheroids obtained through the following human prostate cell lines using synchrotron X-ray microfluorescence: tumor cell line androgen independent (DU145), tumor cell line androgen dependent (LNCaP), and normal cell line (RWPE-1). The measurements were performed with a standard geometry of 45° of incidence, excited by a white beam using a pixel of 25 μm and an acquisition time of 300 ms/pixel at the X-ray fluorescence beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). The synchrotron X-ray microfluorescence results showed differences between groups in all elements analyzed and suggested that further studies should be performed to understand the relationship of these trace elements with the progression and development of the disease.  相似文献   
72.
73.
Optics and Spectroscopy - 10.1134/S0030400X17050095  相似文献   
74.
75.
In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of the one dimensional free particle propagator has been evaluated explicitly. With this propagator in hand, it has been shown that, even in free particle case, normal generalized uncertainty principle and doubly special relativity show very much different result.  相似文献   
76.
77.
78.
79.
Acetyl‐l ‐carnitine (ALCAR) is a potential biomarker for the modulation of brain neurotransmitter activity, but is also present in cerebrospinal fluid (CSF). Recent studies have utilized hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC‐MS/MS) based assays to detect and quantify ALCAR within biofluids such as urine, plasma and serum, using various sample pretreatment procedures. In order to address the need to quantify ALCAR in CSF on a high‐throughput scale, a new and simple HILIC‐MS/MS assay has been successfully developed and validated. For rapid analysis, CSF sample pretreatment was performed via ‘dilute and shoot’ directly onto an advanced HILIC column prior to MS/MS detection. This newly developed HILIC‐MS/MS assay shows good recoveries of ALCAR without the need for chemical derivatization and multistep sample extraction procedures. The employment of this assay is suitable for the high‐throughput bioanalysis and quantification of ALCAR within the CSF of various animal models and human clinical studies. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
80.
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