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   338059篇
  免费   2943篇
  国内免费   365篇
化学   161700篇
晶体学   4148篇
力学   17542篇
综合类   4篇
数学   50434篇
物理学   107539篇
  2021年   3523篇
  2020年   4039篇
  2019年   4772篇
  2018年   7079篇
  2017年   7222篇
  2016年   9449篇
  2015年   4811篇
  2014年   8112篇
  2013年   14870篇
  2012年   12695篇
  2011年   14217篇
  2010年   11618篇
  2009年   11534篇
  2008年   13541篇
  2007年   13130篇
  2006年   11712篇
  2005年   10400篇
  2004年   9889篇
  2003年   9050篇
  2002年   9166篇
  2001年   8500篇
  2000年   6902篇
  1999年   5077篇
  1998年   4729篇
  1997年   4511篇
  1996年   4266篇
  1995年   3682篇
  1994年   3797篇
  1993年   3772篇
  1992年   3801篇
  1991年   4057篇
  1990年   4098篇
  1989年   4028篇
  1988年   3808篇
  1987年   3860篇
  1986年   3536篇
  1985年   4182篇
  1984年   4364篇
  1983年   3700篇
  1982年   3924篇
  1981年   3622篇
  1980年   3323篇
  1979年   3788篇
  1978年   3889篇
  1977年   4060篇
  1976年   4124篇
  1975年   3823篇
  1974年   3705篇
  1973年   3887篇
  1972年   3284篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is...  相似文献   
52.
53.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  相似文献   
54.
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   
55.
56.
Physics of Particles and Nuclei Letters - When creating accelerators and storage-ring installations in a compact space, there is not always enough space for all the necessary magnet elements. In...  相似文献   
57.
Herein, we report the synthesis of specific silica-supported Co/Co3O4 core–shell based nanoparticles prepared by template synthesis of cobalt-pyromellitic acid on silica and subsequent pyrolysis. The optimal catalyst material allows for general and selective hydrogenation of pyridines, quinolines, and other heteroarenes including acridine, phenanthroline, naphthyridine, quinoxaline, imidazo[1,2-a]pyridine, and indole under comparably mild reaction conditions. In addition, recycling of these Co nanoparticles and their ability for dehydrogenation catalysis are showcased.  相似文献   
58.
Lanthanide dinitrogen complexes, Ln(N2) x (x = 1-8), were investigated by Density Functional Theory computations using the B3LYP exchange-correlation functional in conjunction with quasirelativistic pseudopotentials for Ln. After a recent study on the lanthanum complexes (A. Kovács, Structural Chemistry 2018 , 29, 1825), the present study aimed to probe the changes upon variously filled 4f subshells of Ln on the structures, stabilities, and bonding properties in related complexes of Nd, Ho, and Lu. The bonding properties were assessed on the basis of natural atomic charges, Ln valence orbital populations, and analysis of bonding molecular orbitals.  相似文献   
59.
Russian Physics Journal - A relationship between the structural-morphological and physical-mechanical properties of macro-porous calcium phosphate (CaP) coatings on the surface of titanium implants...  相似文献   
60.
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity).  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