全文获取类型
收费全文 | 33184篇 |
免费 | 2063篇 |
国内免费 | 1784篇 |
专业分类
化学 | 19060篇 |
晶体学 | 139篇 |
力学 | 1337篇 |
综合类 | 625篇 |
数学 | 6971篇 |
物理学 | 8899篇 |
出版年
2023年 | 213篇 |
2022年 | 368篇 |
2021年 | 1196篇 |
2020年 | 653篇 |
2019年 | 759篇 |
2018年 | 532篇 |
2017年 | 550篇 |
2016年 | 726篇 |
2015年 | 814篇 |
2014年 | 1058篇 |
2013年 | 1966篇 |
2012年 | 1273篇 |
2011年 | 1472篇 |
2010年 | 1360篇 |
2009年 | 1856篇 |
2008年 | 1902篇 |
2007年 | 2082篇 |
2006年 | 1562篇 |
2005年 | 962篇 |
2004年 | 923篇 |
2003年 | 1011篇 |
2002年 | 3475篇 |
2001年 | 927篇 |
2000年 | 647篇 |
1999年 | 533篇 |
1998年 | 518篇 |
1997年 | 387篇 |
1996年 | 465篇 |
1995年 | 408篇 |
1994年 | 433篇 |
1993年 | 466篇 |
1992年 | 465篇 |
1991年 | 327篇 |
1990年 | 248篇 |
1989年 | 205篇 |
1988年 | 235篇 |
1987年 | 190篇 |
1986年 | 206篇 |
1985年 | 318篇 |
1984年 | 236篇 |
1983年 | 145篇 |
1982年 | 293篇 |
1981年 | 469篇 |
1980年 | 427篇 |
1979年 | 466篇 |
1978年 | 374篇 |
1977年 | 281篇 |
1976年 | 237篇 |
1974年 | 74篇 |
1973年 | 149篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In this work we consider the problem of minimizing a continuously differentiable function over a feasible set defined by box
constraints. We present a decomposition method based on the solution of a sequence of subproblems. In particular, we state
conditions on the rule for selecting the subproblem variables sufficient to ensure the global convergence of the generated
sequence without convexity assumptions. The conditions require to select suitable variables (related to the violation of the
optimality conditions) to guarantee theoretical convergence properties, and leave the degree of freedom of selecting any other
group of variables to accelerate the convergence. 相似文献
992.
Venkatramani Lakshmibai Komaranapuram N. Raghavan Parameswaran Sankaran 《Central European Journal of Mathematics》2009,7(2):214-223
It is shown that the proof by Mehta and Parameswaran of Wahl’s conjecture for Grassmannians in positive odd characteristics
also works for symplectic and orthogonal Grassmannians.
相似文献
993.
In this paper, we get W
1,p
(R
n
)-boundedness for tangential maximal function and nontangential maximal function, which improves J.Kinnunen, P.Lindqvist and
Tananka’s results.
Supported by the key Academic Discipline of Zhejiang Province of China under Grant No.2005 and the Zhejiang Provincial Natural
Science Foundation of China. 相似文献
994.
Nasser Iranpoor Elham Etemadi-Davan 《Phosphorus, sulfur, and silicon and the related elements》2014,189(7-8):1165-1173
995.
Poly(D,L‐lactide‐co‐glycolide) 50:50 (PLGA)/graphene oxide (GO) nanocomposite films were prepared with various GO weight fractions. A significant enhancement of mechanical properties of the PLGA/GO nanocomposite films was obtained with GO weight fractions. The incorporation of only 5 wt% of GO resulted in an ~2.5‐fold and ~4.7‐fold increase in the tensile strength and Young's modulus of PLGA, respectively. The thermomechanical behaviors of composite films were investigated by dynamic mechanical analysis. Results indicated that the values of Tg and storage moduli of the PLGA/GO composites were higher than those of the pristine PLGA. The improvement in oxygen barrier properties of composites was presumably attributed to the filler effect of the randomly dispersed GO throughout the PLGA matrix. In this work, we also studied in vitro biodegradation behavior. PLGA/GO composite films were hydrolyzed at 37°C for periods up to 49 days. Because of the presence of GO nanosheets, degradation of composite films took place more slowly with increasing GO amounts. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
996.
Young Ki Lee Wonhee Hur Sung Won Lee Sung Woo Hong Sung Woo Kim Jung Eun Choi Seung Kew Yoon 《Experimental & molecular medicine》2014,46(2):e77
14-3-3ζ is related to many cancer survival cellular processes. In a previous study, we showed that silencing 14-3-3ζ decreases the resistance of hepatocellular carcinoma (HCC) to chemotherapy. In this study, we investigated whether silencing 14-3-3ζ affects the radioresistance of cancer stem-like cells (CSCs) in HCC. Knockdown of 14-3-3ζ decreased cell viability and the number of spheres by reducing radioresistance in CSCs after γ-irradiation (IR). Furthermore, the levels of pro-apoptotic proteins were upregulated in CSCs via silencing 14-3-3ζ after IR. These results suggest that 14-3-3ζ knockdown enhances radio-induced apoptosis by reducing radioresistance in liver CSCs. 相似文献
997.
998.
The preparation of the cerium and europium co-doped YAG materials as well as the study for their synthesis and emitting mechanism of the energy transfer between Ce3+ and Eu3+ were investigated in the present study. YAG:Ce3+, Eu3+ powders were synthesized using a high-energy ball milling method in different sintering temperature and atmosphere: air and H2/N2. The effects of the synthesis procedure on the crystallinity, morphology, structure, and luminescence spectra were examined by X-ray diffraction, field emission-scanning electron microscopy, and photoluminescence spectroscopy. The europium co-doped YAG:Ce3+ phosphors is improved the chromaticity coordinates. 相似文献
999.
对紫外荧光硫分析仪用石英燃烧管进行了结构改进,在原结构设计的基础上,增加了裂解氧预热管、挡板和氧气反吹口等。实验表明,相比于原结构设计的石英燃烧管进样量20μL和检出限0.2 mg/L,改进后的燃烧管进样量提高到了100μL,检出限达0.05 mg/L,线性范围为0.1~600 mg/L,相关系数大于0.999。采用改进后的燃烧管测定10.0 mg/L硫含量标准物质,其相对偏差为–1.5%~3.1%,测定结果的相对标准偏差为1.77%(n=10),两者均符合油品硫含量检测要求。改进后的燃烧管可替代市场上的其它国产石英燃烧管,进行油品中硫含量的测定。 相似文献
1000.