全文获取类型
收费全文 | 11618篇 |
免费 | 670篇 |
国内免费 | 455篇 |
专业分类
化学 | 5293篇 |
晶体学 | 219篇 |
力学 | 866篇 |
综合类 | 23篇 |
数学 | 1301篇 |
物理学 | 5041篇 |
出版年
2023年 | 97篇 |
2022年 | 159篇 |
2021年 | 161篇 |
2020年 | 193篇 |
2019年 | 219篇 |
2018年 | 253篇 |
2017年 | 199篇 |
2016年 | 309篇 |
2015年 | 247篇 |
2014年 | 394篇 |
2013年 | 585篇 |
2012年 | 783篇 |
2011年 | 892篇 |
2010年 | 702篇 |
2009年 | 688篇 |
2008年 | 742篇 |
2007年 | 629篇 |
2006年 | 658篇 |
2005年 | 517篇 |
2004年 | 452篇 |
2003年 | 378篇 |
2002年 | 338篇 |
2001年 | 504篇 |
2000年 | 395篇 |
1999年 | 282篇 |
1998年 | 215篇 |
1997年 | 181篇 |
1996年 | 187篇 |
1995年 | 166篇 |
1994年 | 150篇 |
1993年 | 111篇 |
1992年 | 115篇 |
1991年 | 118篇 |
1990年 | 103篇 |
1989年 | 81篇 |
1988年 | 60篇 |
1987年 | 45篇 |
1986年 | 42篇 |
1985年 | 45篇 |
1984年 | 42篇 |
1983年 | 24篇 |
1982年 | 32篇 |
1981年 | 33篇 |
1980年 | 25篇 |
1979年 | 20篇 |
1978年 | 25篇 |
1977年 | 19篇 |
1976年 | 18篇 |
1975年 | 19篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Shi-Tao Han Hong-Ying Duan Lan-Yun Chen Dr. Tian-Guang Zhan Dr. Li-Juan Liu Li-Chun Kong Prof. Kang-Da Zhang 《化学:亚洲杂志》2021,16(23):3886-3889
A photo-switchable hetero-complementary quadruple H-bonding array, which consists of an azobenzene-derived ureidopyrimidinone (UPy) module ( Azo-UPy ) and a nonphotoactive diamidonaphthyridine (DAN) derivative ( Napy-1 ), is constructed based on a reversible photo-locking approach. Upon UV (390 nm)/Vis (460 nm) light irradiations, photo-switchable quadruple H-bonded dimerization between Azo-UPy and Napy-1 can be achieved with exhibiting 4.8×104-fold differences in binding strength (ON/OFF ratios). Furthermore, smart polymeric gels with unique photo-controlled macroscopic self-assembly behavior can be fabricated by introducing such quadruple H-bonding array as photo-regulable noncovalent interfacial connections. 相似文献
32.
Journal of Thermal Analysis and Calorimetry - In the present work, pyrolysis kinetic mechanism was studied for regenerated cellulosic fiber (RCF) and composite RCF containing silicon/nitrogen flame... 相似文献
33.
34.
35.
Shuzhong Zhan 《大学化学》2020,35(8):107-110
The structural discovery and understanding of atoms are a microcosm of the process of human cognition and a concrete practice of materialistic dialectics and methodology, which contains a wealth of dialectical thought. The "atomic structure" chapter (section) in inorganic chemistry course is a difficult part for the first-year undergraduates to understand. The introduction of philosophical idea into the teaching process of this chapter (section) will not only help them learn and master chemistry, but also help them establish a correct world view and methodology. 相似文献
36.
Changmao Wang Yaqin Wang Haitang Xie Cuijiao Zhan Xuejun He Ran Liu Rongfeng Hu Jie Shen Yuanwei Jia 《Biomedical chromatography : BMC》2022,36(3):e5287
In this work, we developed and validated a highly sensitive, rapid and stable LC–MS/MS method for the determination of ibuprofen in human plasma with ibuprofen-d3 as a stable isotopically labeled internal standard (SIL-IS). Human plasma samples were prepared by one-step protein precipitation. The chromatographic separation was achieved on a Poroshell 120 EC-C18 (2.1 × 50 mm, 2.7 μm). Aqueous solution (containing 0.05% acetic acid and 5 mm NH4Ac) and methanol were selected as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in negative ion mode. Multiple reaction monitoring mode was used for quantification using target fragment ions m/z 205.0 → 161.1 for ibuprofen and m/z 208.0 → 164.0 for SIL-IS, respectively. This method exhibited a linear range of 0.05–36 μg/ml for ibuprofen with correlation coefficient >0.99. Mean recoveries of ibuprofen in human plasma ranged from 78.4 to 80.9%. The RSD of intra- and inter-day precision were both < 5%. The accuracy was between 88.2 and 103.67%. The matrix effect was negligible in human plasma, including lipidemia and hemolytic plasma. A simple, efficient and accurate LC–MS/MS method was successfully established and applied to a pharmacokinetic study in healthy Chinese volunteers after a single oral administration of ibuprofen granules. 相似文献
37.
38.
Achieving tunable band gaps in a structure by external stimuli is of great importance in acoustic applications. This paper aims to investigate the tunability of band gaps in square-lattice-like elastic periodic structures that are usually not featured with notable band gaps.Endowed with chirality, the periodic structures here are able to undergo imperfection-insensitive large deformation under extension or compression. The influences of geometric parameters on band gaps are discussed via the nonlinear finite element method. It is shown that the band gaps in such structures with curved beams can be very rich and, more importantly, can be efficiently and robustly tuned by applying appropriate mechanical loadings without inducing buckling. As expected, geometry plays a more significant role than material nonlinearity does in the evolution of band gaps. The dynamic tunability of band gaps through mechanical loading is further studied. Results show that closing, opening, and shifting of band gaps can be realized by exerting real-time global extension or compression on the structure. The proposed periodic structure with well-designed chiral symmetry can be useful in the design of particular acoustic devices. 相似文献
39.
Journal of Nonlinear Science - We prove that if the local second-order structure function exponents in the inertial range remain positive uniformly in viscosity, then any spacetime $$L^2$$ weak... 相似文献
40.
Acta Mathematicae Applicatae Sinica, English Series - The paper studies an evolutionary p(x)-Laplacian equation with a convection term $$u_{t}=\operatorname{div}\left(\rho^{\alpha}|\nabla... 相似文献