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   408534篇
  免费   5417篇
  国内免费   1447篇
化学   220838篇
晶体学   5856篇
力学   17353篇
综合类   12篇
数学   48580篇
物理学   122759篇
  2020年   2461篇
  2018年   3374篇
  2017年   3316篇
  2016年   5181篇
  2015年   4215篇
  2014年   5542篇
  2013年   17481篇
  2012年   13609篇
  2011年   16619篇
  2010年   10308篇
  2009年   10209篇
  2008年   14961篇
  2007年   15188篇
  2006年   14870篇
  2005年   16052篇
  2004年   14461篇
  2003年   12101篇
  2002年   10734篇
  2001年   12170篇
  2000年   9378篇
  1999年   7510篇
  1998年   6156篇
  1997年   5975篇
  1996年   5985篇
  1995年   5551篇
  1994年   5166篇
  1993年   4980篇
  1992年   5592篇
  1991年   5437篇
  1990年   5088篇
  1989年   4932篇
  1988年   5191篇
  1987年   4917篇
  1986年   4727篇
  1985年   6800篇
  1984年   6926篇
  1983年   5671篇
  1982年   6306篇
  1981年   6205篇
  1980年   5980篇
  1979年   6053篇
  1978年   6201篇
  1977年   6115篇
  1976年   6084篇
  1975年   5913篇
  1974年   5647篇
  1973年   5905篇
  1972年   3444篇
  1971年   2579篇
  1968年   2573篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
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   
92.
93.
The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments.  相似文献   
94.
95.
96.
97.
98.
99.
100.
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557  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