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   50873篇
  免费   4567篇
  国内免费   1713篇
化学   35528篇
晶体学   444篇
力学   1604篇
综合类   67篇
数学   6501篇
物理学   13009篇
  2023年   645篇
  2022年   647篇
  2021年   1062篇
  2020年   1285篇
  2019年   1255篇
  2018年   1393篇
  2017年   1190篇
  2016年   2178篇
  2015年   1824篇
  2014年   2051篇
  2013年   3467篇
  2012年   4048篇
  2011年   4314篇
  2010年   2626篇
  2009年   2299篇
  2008年   3326篇
  2007年   3139篇
  2006年   2835篇
  2005年   2447篇
  2004年   1920篇
  2003年   1441篇
  2002年   1375篇
  2001年   1031篇
  2000年   865篇
  1999年   838篇
  1998年   590篇
  1997年   523篇
  1996年   660篇
  1995年   488篇
  1994年   433篇
  1993年   488篇
  1992年   393篇
  1991年   320篇
  1990年   281篇
  1989年   230篇
  1988年   218篇
  1987年   205篇
  1986年   193篇
  1985年   246篇
  1984年   207篇
  1983年   156篇
  1982年   142篇
  1981年   130篇
  1980年   106篇
  1979年   108篇
  1978年   97篇
  1977年   92篇
  1976年   101篇
  1975年   85篇
  1973年   101篇
排序方式: 共有10000条查询结果,搜索用时 37 毫秒
1.
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed.  相似文献   
2.
Tian  Xiu-Zhi  Yang  Rui  Ma  Jia-Jia  Ni  Yong-Hao  Deng  Hai-Bo  Dai  Lei  Tan  Jiao-Jun  Zhang  Mei-Yun  Jiang  Xue 《高分子科学》2022,40(7):789-798
Chinese Journal of Polymer Science - Antistatic and strength properties are of vital importance for polyurethane rubber used in moving parts of many industrial instruments. Herein, polyurethane was...  相似文献   
3.
Numerical Algorithms - In this work, we propose a fractional extension of the one-dimensional nonlinear vibration problem on an elastic string. The fractional problem is governed by a hyperbolic...  相似文献   
4.
Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of...  相似文献   
5.
6.
7.
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo.  相似文献   
8.
Sun  Qinqin  Wang  Xiuye  Yang  Guolai  Chen  Ye-Hwa  Ma  Fai 《Nonlinear dynamics》2022,109(3):1629-1650
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the...  相似文献   
9.
Gao  Zhigen  Guo  Jianhua  Ma  Yanyuan 《中国科学 数学(英文版)》2021,64(8):1905-1916
Science China Mathematics - Linear factor models are familiar tools used in many fields. Several pioneering literatures established foundational theoretical results of the quasi-maximum likelihood...  相似文献   
10.
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