全文获取类型
收费全文 | 43526篇 |
免费 | 2694篇 |
国内免费 | 1405篇 |
专业分类
化学 | 31009篇 |
晶体学 | 361篇 |
力学 | 1260篇 |
综合类 | 87篇 |
数学 | 6902篇 |
物理学 | 8006篇 |
出版年
2023年 | 328篇 |
2022年 | 353篇 |
2021年 | 709篇 |
2020年 | 933篇 |
2019年 | 918篇 |
2018年 | 647篇 |
2017年 | 614篇 |
2016年 | 1329篇 |
2015年 | 1173篇 |
2014年 | 1522篇 |
2013年 | 2319篇 |
2012年 | 2929篇 |
2011年 | 3269篇 |
2010年 | 1884篇 |
2009年 | 1725篇 |
2008年 | 2913篇 |
2007年 | 2628篇 |
2006年 | 2577篇 |
2005年 | 2449篇 |
2004年 | 2034篇 |
2003年 | 1707篇 |
2002年 | 1679篇 |
2001年 | 772篇 |
2000年 | 713篇 |
1999年 | 618篇 |
1998年 | 588篇 |
1997年 | 583篇 |
1996年 | 539篇 |
1995年 | 410篇 |
1994年 | 499篇 |
1993年 | 422篇 |
1992年 | 402篇 |
1991年 | 365篇 |
1990年 | 313篇 |
1989年 | 282篇 |
1988年 | 248篇 |
1987年 | 244篇 |
1986年 | 210篇 |
1985年 | 397篇 |
1984年 | 343篇 |
1983年 | 291篇 |
1982年 | 350篇 |
1981年 | 284篇 |
1980年 | 294篇 |
1979年 | 242篇 |
1978年 | 234篇 |
1977年 | 224篇 |
1976年 | 214篇 |
1975年 | 191篇 |
1974年 | 169篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
1.
Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function... 相似文献
2.
Zeng Qing-Wei Wen Zhuo-Yu Fu Jun-Feng Zhou Nan-Run 《International Journal of Theoretical Physics》2021,60(9):3306-3333
International Journal of Theoretical Physics - A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution... 相似文献
3.
4.
Donglei Wei Huili Li Chuanqing Yang Jianmin Fu Hou Chen Liangjiu Bai Wenxiang Wang Huawei Yang Lixia Yang Ying Liang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1588-1594
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst. 相似文献
5.
An electromechanical integrated electrostatic harmonic actuator is promising for the miniaturization of electromechanical devices. As the dimensions of the actuator decrease, the effects of the van der Waals force become obvious. In this study, by considering the nonlinearity of electrostatic and van der Waals forces, nonlinear vibration equations of the flexible ring of an electrostatic harmonic actuator are deduced. Using these equations, the nonlinear free vibration and nonlinear forced response of the actuator are investigated. The effects of the van der Waals force on the nonlinear vibration of the flexible ring are analyzed. Results show that these effects of the van der Waals force are relatively obvious under some conditions and should be considered. 相似文献
6.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
7.
Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis Extracts by LC‐MS/MS 下载免费PDF全文
8.
9.
10.
Xiaoxia Yang Hongyan Xie Zhiguang Xu Jiabing Feng Qiwei Fu Haidong Li Yongtang Jia 《Journal of polymer science. Part A, Polymer chemistry》2021,59(9):813-823
An efficient, atom-economic, oxygen-tolerant, and water-tolerant strategy has been established to synthesize cyano-rich polyesters. Four kinds of organic bases, 1,1,3,3-tetramethylguanidine (TMG), 4-dimethylaminopyridine, triethylamine, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were explored for accelerating Michael addition polymerization of malononitrile and 1,4-butandiol diacrylate. TMG can promote the polymerization efficiently under mild conditions to quantitatively afford polyester with high-molecular weight and moderate polydispersity. The comparison of the kinetic studies of TMG and TBD reveals that TMG shows better catalytic performance, while the catalysis of TBD brings about oligomers in spite of the higher efficiency at early age of the polymerization. Moreover, other diacrylate compounds could also be quantitatively polymerized to afford polyesters with high molecular weight. When dimethacrylate is chose as the monomer, the polymerization becomes sluggish. All the afforded polyesters display programmable thermal and mechanical properties that are closely related to their chemical structures. 相似文献