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   2819篇
  免费   111篇
  国内免费   21篇
化学   1879篇
晶体学   23篇
力学   58篇
数学   414篇
物理学   577篇
  2024年   10篇
  2023年   44篇
  2022年   60篇
  2021年   83篇
  2020年   83篇
  2019年   85篇
  2018年   82篇
  2017年   99篇
  2016年   103篇
  2015年   72篇
  2014年   176篇
  2013年   279篇
  2012年   205篇
  2011年   194篇
  2010年   165篇
  2009年   118篇
  2008年   175篇
  2007年   138篇
  2006年   105篇
  2005年   92篇
  2004年   87篇
  2003年   79篇
  2002年   78篇
  2001年   31篇
  2000年   20篇
  1999年   23篇
  1998年   11篇
  1997年   11篇
  1996年   11篇
  1995年   14篇
  1994年   11篇
  1993年   12篇
  1992年   15篇
  1991年   9篇
  1990年   8篇
  1989年   15篇
  1988年   12篇
  1987年   10篇
  1986年   8篇
  1985年   16篇
  1984年   18篇
  1983年   16篇
  1982年   21篇
  1981年   4篇
  1980年   12篇
  1979年   9篇
  1978年   7篇
  1977年   6篇
  1973年   2篇
  1971年   2篇
排序方式: 共有2951条查询结果,搜索用时 265 毫秒
81.
82.
Quantitation of drugs used for the treatment of chronic lymphocytic leukemia in various biological matrices during both pre-clinical and clinical developments is very important, often in routine therapeutic drug monitoring. The first developed methods for quantitation were traditionally done on LC in combination with either UV or fluorescence detection. However, the emergence of LC with mass spectrometry in tandem in early 1990s has revolutionized the quantitation as it has provided better sensitivity and selectivity within a shorter run time; therefore it has become the choice of method for the analysis of various drugs. In this article, an overview of various bioanalytical methods (HPLC or LC–MS/MS) for the quantification of drugs for the treatment of chronic lymphocytic leukemia, along with applicability of these methods, is given.  相似文献   
83.
Three new metal complexes [Cu(L)2] (1), [Co(L)2] (2) and [Zn(L)2] (3) have been prepared by the reaction of hydrated salts of metal (II) acetate with new Schiff base ligand HL, [2‐((4‐(dimethylamino)phenylimino)methyl)‐4,6‐di‐t‐butylphenol] and characterized by different physico‐chemical analyses such as elemental analysis, single XRD, 1H NMR, FTIR and UV–Vis spectroscopic techniques. Their biomolecular docking, antimicrobial and cytotoxicity studies have also been demonstrated. The proposed structure of Schiff base ligand HL and complex 2 are confirmed by Single crystal X‐ray crystallography study. This analysis revealed that metal (II) complexes remain in distorted tetrahedral coordination environments. The electronic properties such as HOMO and LUMO energies are carried out by gaseous phase DFT/B3LYP calculations using Gaussian 09 program. Complex 1 showed a good binding propensity to the DNA and HSA, during the assessment of docking studies. Schiff base ligand HL and its metal (II) complexes, 1–3 screened for their in vitro antimicrobial activities using the disc diffusion method against selected microbes. Complex 1 shows higher antimicrobial activity than complexes 2, 3 and Schiff base ligand HL. According to the results obtained from the cytotoxic studies, Schiff base ligand HL and its metal (II) complexes 1–3 have better cytotoxicity against MCF‐7 cell lines with potency higher than the currently used chemotherapeutic agent cyclophosphamide.  相似文献   
84.
85.
86.
Journal of Thermal Analysis and Calorimetry - In the present work, the rheological behaviour of three different categories of nanofluid samples, 25 nm CeO2/EG, 13 nm Al2O3/EG and...  相似文献   
87.
The design of porous materials for the recognition of multiple hydrocarbons is highly desirable for the energy-efficient separation and recognition of chemical feedstock. Herein, three new iso-structural porous discrete metal–organic cages of formula {[Pd3(NiPr)3PO]4(R-AN)6} (R-AN=anilate linkers) for the selective recognition of substituted aromatic hydrocarbons are reported. The tetrahedral cages 1 , 2 , and 3 containing anilate, chloranilate, and bromanilate linkers exhibited selective encapsulation of mesitylene, o-xylene, and p-xylene, respectively, over other analogous aromatic hydrocarbons. These selective encapsulations were driven by the variations in the portal diameters present at each of these cages and their interactions with the hydrocarbon guests. These observations are supported by mass spectrometry, NMR studies, and theoretical binding-energy calculations.  相似文献   
88.
In this paper, we study the approximation properties of bivariate summation‐integral–type operators with two parameters . The present work deals within the polynomial weight space. The rate of convergence is obtained while the function belonging to the set of all continuous and bounded function defined on ([0],)(×[0],) and function belonging to the polynomial weight space with two parameters, also convergence properties, are studied. To know the asymptotic behavior of the proposed bivariate operators, we prove the Voronovskaya type theorem and show the graphical representation for the convergence of the bivariate operators, which is illustrated by graphics using Mathematica. Also with the help of Mathematica, we discuss the comparison by means of the convergence of the proposed bivariate summation‐integral–type operators and Szász‐Mirakjan‐Kantorovich operators for function of two variables with two parameters to the function. In the same direction, we compute the absolute numerical error for the bivariate operators by using Mathematica and is illustrated by tables and also the comparison takes place of the proposed bivariate operators with the bivariate Szász‐Mirakjan operators in the sense of absolute error, which is represented by table. At last, we study the simultaneous approximation for the first‐order partial derivative of the function.  相似文献   
89.
This paper investigates the existence of positive solutions for a sixth-order differential system with three variable parameters. Using a fixed point theorem and an operator spectral theorem we give some new existence results.  相似文献   
90.
Research on Chemical Intermediates - Eight new series of novel phenothiazine-based chalcone derivatives with various N-substituted rhodanines (10a–g to 17a–g) were synthesized by...  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