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   242456篇
  免费   3672篇
  国内免费   658篇
化学   132868篇
晶体学   3878篇
力学   9144篇
综合类   16篇
数学   26755篇
物理学   74125篇
  2020年   2266篇
  2019年   2351篇
  2018年   2848篇
  2017年   2957篇
  2016年   4697篇
  2015年   3127篇
  2014年   4623篇
  2013年   11261篇
  2012年   8525篇
  2011年   10161篇
  2010年   7193篇
  2009年   6894篇
  2008年   9128篇
  2007年   8931篇
  2006年   8462篇
  2005年   7620篇
  2004年   6902篇
  2003年   6162篇
  2002年   5822篇
  2001年   6900篇
  2000年   5293篇
  1999年   3987篇
  1998年   3192篇
  1997年   3089篇
  1996年   3104篇
  1995年   2871篇
  1994年   2773篇
  1993年   2653篇
  1992年   3328篇
  1991年   3081篇
  1990年   3026篇
  1989年   3042篇
  1988年   3030篇
  1987年   3052篇
  1986年   2881篇
  1985年   3751篇
  1984年   3739篇
  1983年   2954篇
  1982年   3087篇
  1981年   3164篇
  1980年   2891篇
  1979年   3222篇
  1978年   3184篇
  1977年   3318篇
  1976年   3155篇
  1975年   2854篇
  1974年   2816篇
  1973年   2725篇
  1972年   1846篇
  1968年   1891篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
Set-Valued and Variational Analysis - R. Tyrell Rockafellar and his collaborators introduced, in a series of works, new regression modeling methods based on the notion of superquantile (or...  相似文献   
13.
Russian Physics Journal - The process of radiative decay of a Higgs boson into a fermion-antifermion pair $$ H\Rightarrow \overline{ff}\upgamma . $$ is investigated within the framework of the...  相似文献   
14.
Differential Equations - Galathea traps for confining plasma in a magnetic field created by current-carrying conductors immersed in the plasma volume constitute a promising class of objects for...  相似文献   
15.
Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown...  相似文献   
16.
17.
18.
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.  相似文献   
19.
20.
Riociguat is novel antihypertensive drug for treatment of pulmonary hypertension. As such, it is still being tested in many clinical and pharmacokinetic trials. Existing methods that determine serum riociguat and desmethylriociguat (DMR) are based solely on liquid chromatography with mass spectrometry. Therefore, we present a novel capillary electrophoresis with mass spectrometry method (CE-MS) for their determination in human serum as alternative method for ongoing trials. Complete resolution of both analytes was achieved by means of pH optimization of ammonium formate background electrolytes that are fully compatible with ESI/MS detection. Simple liquid-liquid extraction was used as sample pretreatment. The calibration dependence of the method was linear (in the range of 10–1000 ng/mL), with adequate accuracy (90.1–114.9%) and precision (13.4%). LOD and LOQ were arbitrarily set at 10 ng/mL for both analytes. Clinical applicability was validated using serum samples from patients treated with riociguat in pharmacokinetic study and the results corresponded with reference HPLC-MS/MS values. Capillary electrophoresis proved to be sensitive and selective tool for the analysis of riociguat and DMR.  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