全文获取类型
收费全文 | 79711篇 |
免费 | 11684篇 |
国内免费 | 9186篇 |
专业分类
化学 | 55730篇 |
晶体学 | 887篇 |
力学 | 5007篇 |
综合类 | 719篇 |
数学 | 9740篇 |
物理学 | 28498篇 |
出版年
2024年 | 155篇 |
2023年 | 1514篇 |
2022年 | 1645篇 |
2021年 | 2493篇 |
2020年 | 2908篇 |
2019年 | 2839篇 |
2018年 | 2504篇 |
2017年 | 2291篇 |
2016年 | 3392篇 |
2015年 | 3531篇 |
2014年 | 4231篇 |
2013年 | 5713篇 |
2012年 | 6840篇 |
2011年 | 7149篇 |
2010年 | 4971篇 |
2009年 | 4856篇 |
2008年 | 5147篇 |
2007年 | 4659篇 |
2006年 | 4355篇 |
2005年 | 3750篇 |
2004年 | 3028篇 |
2003年 | 2341篇 |
2002年 | 2130篇 |
2001年 | 1913篇 |
2000年 | 1725篇 |
1999年 | 1811篇 |
1998年 | 1511篇 |
1997年 | 1286篇 |
1996年 | 1333篇 |
1995年 | 1168篇 |
1994年 | 1095篇 |
1993年 | 932篇 |
1992年 | 815篇 |
1991年 | 717篇 |
1990年 | 609篇 |
1989年 | 506篇 |
1988年 | 398篇 |
1987年 | 361篇 |
1986年 | 320篇 |
1985年 | 321篇 |
1984年 | 218篇 |
1983年 | 188篇 |
1982年 | 150篇 |
1981年 | 117篇 |
1980年 | 87篇 |
1978年 | 57篇 |
1977年 | 53篇 |
1976年 | 53篇 |
1975年 | 59篇 |
1973年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
科学评价大学生科研创新能力对我国科研水平的提高具有重要意义.采用机器学习模型来预测大学生科研能力可以起到良好的效果,提出一种GAXGBoost模型来实现对大学生的科研能力预测.此模型是以Xgboost算法为基础,然后充分利用遗传算法的全局搜索能力自动搜索Xgboost最优超参数,避免了人为经验调参不准确的缺陷,最后采用精英选择策略以此确保每一轮都是最佳的进化结果.通过分析表明,所采用的GAXGBoost模型在大学生科研能力预测的结果中具有很高的精度,将此模型与Logistic Regression、Random Forest、SVM等模型进行对比,GAXGBoost模型的预测精度最高. 相似文献
22.
Journal of Visualization - Forecast calibration methods based on historical similar atmospheric state are effective means weather forecast accuracy. Conventional approaches search similar forecasts... 相似文献
23.
24.
Meihua Shen Dr. Xinpeng Zhao Dr. Lu Han Nanxi Jin Prof. Song Liu Prof. Tao Jia Prof. Zhijun Chen Prof. Xiuhua Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202104137
Solar-driven interfacial vaporization by localizing solar-thermal energy conversion to the air−water interface has attracted tremendous attention. In the process of converting solar energy into heat energy, photothermal materials play an essential role. Herein, a flexible solar-thermal material di-cyan substituted 5,12-dibutylquinacridone (DCN−4CQA)@Paper was developed by coating photothermal quinacridone derivatives on the cellulose paper. The DCN−4CQA@Paper combines desired chemical and physical properties, broadband light-absorbing, and shape-conforming abilities that render efficient photothermic vaporization. Notably, synergetic coupling of solar-steam and solar-electricity technologies by integrating DCN−4CQA@Paper and the thermoelectric devices is realized without trade-offs, highlighting the practical consideration toward more impactful solar heat exploitation. Such solar distillation and low-grade heat-to-electricity generation functions can provide potential opportunities for fresh water and electricity supply in off-grid or remote areas. 相似文献
25.
Yi-Tong Xu Tian-Yang Zhang Zheng Li Xiang-Nan Liu Yuan-Cheng Zhu Wei-Wei Zhao Hong-Yuan Chen Jing-Juan Xu 《Electroanalysis》2022,34(6):947-955
Photoelectrochemical (PEC) cytosensors, a combination of the PEC process and the living-cell assay, have emerged as a powerful tool in the analytical and biological science. This mini review provides a brief introduction of this arena and summaries the key steps about the development of PEC cytosensors with representative examples, followed by future prospects based on our own opinions. 相似文献
26.
27.
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the... 相似文献
28.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献29.
Mathematical Programming - Convergence analysis of accelerated first-order methods for convex optimization problems are developed from the point of view of ordinary differential equation solvers. A... 相似文献
30.
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