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   60964篇
  免费   3175篇
  国内免费   851篇
化学   37121篇
晶体学   369篇
力学   1380篇
综合类   48篇
数学   11287篇
物理学   14785篇
  2023年   514篇
  2022年   610篇
  2021年   800篇
  2020年   1049篇
  2019年   992篇
  2018年   1347篇
  2017年   1249篇
  2016年   2290篇
  2015年   1955篇
  2014年   2026篇
  2013年   4217篇
  2012年   3883篇
  2011年   3748篇
  2010年   2526篇
  2009年   2161篇
  2008年   3129篇
  2007年   2745篇
  2006年   2515篇
  2005年   2433篇
  2004年   2124篇
  2003年   1768篇
  2002年   1610篇
  2001年   1252篇
  2000年   1176篇
  1999年   893篇
  1998年   737篇
  1997年   676篇
  1996年   808篇
  1995年   604篇
  1994年   672篇
  1993年   598篇
  1992年   590篇
  1991年   506篇
  1990年   554篇
  1989年   455篇
  1988年   467篇
  1987年   413篇
  1986年   417篇
  1985年   569篇
  1984年   518篇
  1983年   417篇
  1982年   403篇
  1981年   417篇
  1980年   367篇
  1979年   351篇
  1978年   365篇
  1977年   357篇
  1976年   369篇
  1974年   345篇
  1973年   339篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
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   
3.
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,...  相似文献   
4.
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within...  相似文献   
5.
Set-Valued and Variational Analysis - In a Hilbert framework ℌ, we study the convergence properties of a Newton-like inertial dynamical system governed by a general maximally monotone...  相似文献   
6.
7.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications.  相似文献   
8.
Central European Journal of Operations Research - Digital competences are among the most important competences in modern society, with the education system playing a key role in the acquisition of...  相似文献   
9.
Du  Zhong  Xu  Tao  Ren  Shuai 《Nonlinear dynamics》2021,104(1):683-689
Nonlinear Dynamics - In this paper, we investigate the interactions of the vector breathers for the coupled Hirota system with $$4\times 4$$ Lax pair. Firstly, we give the first-order breather...  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