全文获取类型
收费全文 | 19691篇 |
免费 | 3291篇 |
国内免费 | 2302篇 |
专业分类
化学 | 13673篇 |
晶体学 | 177篇 |
力学 | 1130篇 |
综合类 | 118篇 |
数学 | 2727篇 |
物理学 | 7459篇 |
出版年
2024年 | 86篇 |
2023年 | 428篇 |
2022年 | 644篇 |
2021年 | 709篇 |
2020年 | 849篇 |
2019年 | 772篇 |
2018年 | 695篇 |
2017年 | 660篇 |
2016年 | 984篇 |
2015年 | 959篇 |
2014年 | 1093篇 |
2013年 | 1469篇 |
2012年 | 1683篇 |
2011年 | 1754篇 |
2010年 | 1228篇 |
2009年 | 1099篇 |
2008年 | 1248篇 |
2007年 | 1102篇 |
2006年 | 977篇 |
2005年 | 882篇 |
2004年 | 703篇 |
2003年 | 613篇 |
2002年 | 684篇 |
2001年 | 545篇 |
2000年 | 439篇 |
1999年 | 429篇 |
1998年 | 343篇 |
1997年 | 312篇 |
1996年 | 331篇 |
1995年 | 292篇 |
1994年 | 232篇 |
1993年 | 165篇 |
1992年 | 166篇 |
1991年 | 158篇 |
1990年 | 124篇 |
1989年 | 94篇 |
1988年 | 54篇 |
1987年 | 56篇 |
1986年 | 72篇 |
1985年 | 47篇 |
1984年 | 32篇 |
1983年 | 27篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1965年 | 1篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Lin-Feng You Tao Wei Qian-Wang Zheng Jun-Fang Lin Li-Qiong Guo Bing-Hua Jiang Jia-Jun Huang 《Applied biochemistry and biotechnology》2018,186(4):949-959
Taxoid 10β-O-acetyl transferase (DBAT) is a key enzyme in the biosynthesis of the famous anticancer drug paclitaxel, which catalyses the formation of baccatin III from 10-deacetylbaccatin III (10-DAB). However, the activity essential residues of the enzyme are still unknown, and the acylation mechanism from its natural substrate 10-deacetylbaccatin III and acetyl CoA to baccatin III remains unclear. In this study, the homology modelling, molecular docking, site-directed mutagenesis, and kinetic parameter determination of the enzyme were carried out. The results showed that the enzyme mutant DBATH162A resulted in complete loss of enzymatic activity, suggesting that the residue histidine at 162 was essential to DBAT activity. Residues D166 and R363 which were located in the pocket of the enzyme by homology modelling and molecular docking were also important for DBAT activity through the site-directed mutations. Furthermore, four amino acid residues including S31 and D34 from motif SXXD, D372 and G376 from motif DFGWG also played important roles on acylation. This was the first report of the elucidation of the activity essential residues of DBAT, making it possible for the further structural-based re-design of the enzyme for efficient biotransformation of baccatin III and paclitaxel. 相似文献
962.
963.
Xiang-Qian Luo Qi-Zhou Chen Shuo-Hong Guo 《Zeitschrift fur Physik C Particles and Fields》1990,47(4):635-639
The physical vacuum state and general expression for the Hamiltonian ofd+1 dimensional lattice gauge theory are given by incorporating the exact ground state of pure gauge theory and the variational fermion vacuum state. The applications toSU(2) andSU(3) gauge theories in 2+1 and 3+1 dimensions are demonstrated and the fermion condensates \(\left\langle {\bar \psi \psi } \right\rangle \) as functions of 1/g 2 are calculated. 相似文献
964.
966.
We report the preparation of Pt–CeO2 nanoparticles on the multi-walled carbon nanotubes (MWNTs) by a reverse micellar method. Transmission electron microscopy
(TEM) analysis indicated that well-dispersed small Pt–CeO2 nanoparticles were formed on the MWCNTs. X-ray diffraction (XRD) analysis confirmed the formation of the Pt–CeO2 nanoparticles on the MWNTs. Cyclic voltammetry (CV) results demonstrated that the Pt–CeO2/MWNT exhibited a higher methanol oxidation than did the Pt/MWNT catalyst. The CO stripping test showed that CeO2 can make CO stripped at a lower potential, which is helpful for CO and methanol electro-oxidation. 相似文献
967.
The Ginzburg-Landau-type complex equations are simplified mathematical models for various pattern formation systems in mechanics,
physics, and chemistry. In this paper, the derivative complex Ginzburg-Landau (DCGL) equation in an unbounded domain Ω ⊂ ℝ2 is studied. We extend the Gagliardo-Nirenberg inequality to the weighted Sobolev spaces introduced by S. V. Zelik. Applied
this Gagliardo-Nirenberg inequality of the weighted Sobolev spaces and based on the technique for the semi-linear system of
parabolic equations which has been developed by M. A. Efendiev and S. V. Zelik, the global attractor
in the corresponding phase space is constructed, the upper bound of its Kolmogorov’s ɛ-entropy is obtained, and the spatial chaos of the attractor
for DCGL equation in ℝ2 is detailed studied.
相似文献
968.
969.
利用分解技巧及一元的结论,讨论单纯型上Meyer-Knig-Zeller算子逼近的收敛阶,得到逼近的正定理. 相似文献
970.
This paper develops a QKD (quantum key distribution)-based queueing
model to investigate the data delay on QKD link and network,
especially that based on trusted relays. It shows the mean
packet delay performance of the QKD system. Furthermore, it proposes a
key buffering policy which could effectively improve the delay
performance in practice. The results will be helpful for quality of
service in practical QKD systems. 相似文献