全文获取类型
收费全文 | 62783篇 |
免费 | 14245篇 |
国内免费 | 6681篇 |
专业分类
化学 | 61501篇 |
晶体学 | 781篇 |
力学 | 2104篇 |
综合类 | 409篇 |
数学 | 5412篇 |
物理学 | 13502篇 |
出版年
2024年 | 74篇 |
2023年 | 617篇 |
2022年 | 1186篇 |
2021年 | 1319篇 |
2020年 | 2386篇 |
2019年 | 3800篇 |
2018年 | 2063篇 |
2017年 | 1754篇 |
2016年 | 4588篇 |
2015年 | 4861篇 |
2014年 | 5053篇 |
2013年 | 6083篇 |
2012年 | 5407篇 |
2011年 | 4665篇 |
2010年 | 4760篇 |
2009年 | 4631篇 |
2008年 | 4211篇 |
2007年 | 3407篇 |
2006年 | 3033篇 |
2005年 | 2952篇 |
2004年 | 2563篇 |
2003年 | 2314篇 |
2002年 | 3240篇 |
2001年 | 2437篇 |
2000年 | 2045篇 |
1999年 | 1038篇 |
1998年 | 528篇 |
1997年 | 384篇 |
1996年 | 376篇 |
1995年 | 293篇 |
1994年 | 265篇 |
1993年 | 255篇 |
1992年 | 183篇 |
1991年 | 200篇 |
1990年 | 137篇 |
1989年 | 120篇 |
1988年 | 105篇 |
1987年 | 65篇 |
1986年 | 66篇 |
1985年 | 69篇 |
1984年 | 42篇 |
1983年 | 33篇 |
1982年 | 27篇 |
1981年 | 13篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1959年 | 4篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
2.
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients... 相似文献
3.
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
4.
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
5.
Jiang Rui-Yang Xin Jia-Wei Cao Cong 《International Journal of Theoretical Physics》2021,60(8):2836-2855
International Journal of Theoretical Physics - Quantum logic gates are the foundation of circuit-based quantum computation and quantum simulation. Multi-qubit quantum controlled gates are of vital... 相似文献
6.
Hongjin Wang Tengfei Long Hao Zhang Meng Li Qi Sun Xin Zhai Lixin Sun 《Biomedical chromatography : BMC》2022,36(4):e5301
3,4-Difluorobenzyl(1-ethyl-5-(4-((4-hydroxypiperidin-1-yl)-methyl)thiazol-2-yl)-1H-indol-3-yl)carbamate (NAI59), a small molecule with outstanding therapeutic effectiveness to anti-pulmonary fibrosis, was developed as an autotaxin inhibitor candidate compound. To evaluate the pharmacokinetics and plasma protein binding of NAI59, a UPLC–MS/MS method was developed to quantify NAI59 in plasma and phosphate-buffered saline. The calibration curve linearity ranged from 9.95 to 1990.00 ng/mL in plasma. The accuracy was −6.8 to 5.9%, and the intra- and inter-day precision was within 15%. The matrix effect and recovery, as well as dilution integrity, were within the criteria. The chromatographic and mass spectrometric conditions were also feasible to determine phosphate-buffered saline samples, and it has been proved that this method exhibits good precision and accuracy in the range of 9.95–497.50 ng/mL in phosphate-buffered saline. This study is the first to determine the pharmacokinetics, absolute bioavailability, and plasma protein binding of NAI59 in rats using this established method. Therefore, the pharmacokinetic profiles of NAI59 showed a dose-dependent relationship after oral administration, and the absolute bioavailability in rats was 6.3%. In addition, the results of protein binding showed that the combining capacity of NAI59 with plasma protein attained 90% and increased with the increase in drug concentration. 相似文献
7.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
8.
Nonlinear Dynamics - The nonlinear modes of a non-conservative nonlinear system are sometimes referred to as damped nonlinear normal modes (dNNMs). Because of the non-conservative... 相似文献
9.
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke... 相似文献
10.