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   3851篇
  免费   112篇
  国内免费   6篇
化学   2228篇
晶体学   97篇
力学   123篇
数学   435篇
物理学   1086篇
  2021年   30篇
  2020年   58篇
  2019年   40篇
  2018年   28篇
  2017年   30篇
  2016年   77篇
  2015年   71篇
  2014年   75篇
  2013年   132篇
  2012年   140篇
  2011年   193篇
  2010年   116篇
  2009年   115篇
  2008年   147篇
  2007年   134篇
  2006年   145篇
  2005年   121篇
  2004年   120篇
  2003年   107篇
  2002年   96篇
  2001年   74篇
  2000年   93篇
  1999年   57篇
  1998年   49篇
  1997年   50篇
  1996年   61篇
  1995年   54篇
  1994年   48篇
  1993年   57篇
  1992年   53篇
  1991年   48篇
  1990年   48篇
  1989年   55篇
  1988年   55篇
  1987年   55篇
  1986年   48篇
  1985年   42篇
  1984年   31篇
  1983年   46篇
  1982年   35篇
  1981年   58篇
  1980年   41篇
  1979年   55篇
  1978年   59篇
  1977年   43篇
  1976年   45篇
  1975年   30篇
  1974年   33篇
  1973年   37篇
  1957年   28篇
排序方式: 共有3969条查询结果,搜索用时 15 毫秒
161.
By means of wet oxygen exposure the stability of RTO anodes has been observed. The deactivation is due to ruthenium loss via unstable higher surface oxides in a long time regime. As follows after uneffective subsurface annealing procedure the catalytic durability is reduced drastically by erosion stimulated increasing ruthenium loss of inhomogeneous active layer surfaces.  相似文献   
162.
Journal of Chemical Crystallography - A new Group 2 bimetallic nitride fluoride phase of approximate composition SrCaNF has been prepared and characterized via high resolution single crystal X-ray...  相似文献   
163.
Combined photoemission core level and satellite structure investigations of pyrolytic titanium-rich TixRu1−x-oxide layers (0.90 ≦ x ≦ 0.97) and RuO2 layers on titanium are used to gain structural and compositional information about these electro-catalytically active surfaces. By means of this method deviations from stoichiometry, the formation of carbon interstitials and the growth of anatase by ruthenium loss could be pointed out.  相似文献   
164.
165.
166.
The etch pattern of (001) and (110) LEC-GaP doped with sulphur (NDNA in the range from 3–7 × 1017 cm−3) do not only show dislocation etch pits but fine pits, so-called “saucer pits” (S-pits). The distribution of S-pits, their etching behaviour and transmission electron microscope observations of etched samples indicated a clear correlation between S-pits and microdefects (fauted-, prismatic dislocation loops and precipitates).  相似文献   
167.
Vapour phase epitaxial layers of InP were deposited onto (111)A-, (111)B-, (001)-, and (110)-oriented GaAs substrates in the InP/PCl3/H2 system using a close-space technique. It is shown that the dependence of the layer quality on the substrate orientation is due to differences in the initial growth stages. Results on the growth rates and the electrical properties of the layers are reported.  相似文献   
168.
The potential of first-void (FV) urine as a non-invasive liquid biopsy for detection of human papillomavirus (HPV) DNA and other biomarkers has been increasingly recognized over the past decade. In this study, we investigated whether the volume of this initial urine stream has an impact on the analytical performance of biomarkers. In parallel, we evaluated different DNA extraction protocols and introduced an internal control in the urine preservative. Twenty-five women, diagnosed with high-risk HPV, provided three home-collected FV urine samples using three FV urine collection devices (Colli-Pee) with collector tubes that differ in volume (4, 10, 20 mL). Each collector tube was prefilled with Urine Conservation Medium spiked with phocine herpesvirus 1 (PhHV-1) DNA as internal control. Five different DNA extraction protocols were compared, followed by PCR for GAPDH and PhHV-1 (qPCR), HPV DNA, and HBB (HPV-Risk Assay), and ACTB (methylation-specific qPCR). Results showed limited effects of collection volume on human and HPV DNA endpoints. In contrast, significant variations in yield for human endpoints were observed for different DNA extraction methods (p < 0.05). Additionally, the potential of PhHV-1 as internal control to monitor FV urine collection, storage, and processing was demonstrated.  相似文献   
169.
170.
The theoretical concept of the computer program is based on the compartment theory for the 3-pool model using single pulse administration of the tracer. The code estimates the model parameters by means of the non-linear method of least squares fit under steady state conditions. Furthermore the parameters of the protein metabolism are calculated. The program works interactively and allows reading and modifying the experimental 15N tracer data via terminal and controlling the program.  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