全文获取类型
收费全文 | 9399篇 |
免费 | 857篇 |
国内免费 | 870篇 |
专业分类
化学 | 1335篇 |
晶体学 | 37篇 |
力学 | 694篇 |
综合类 | 204篇 |
数学 | 7142篇 |
物理学 | 1714篇 |
出版年
2024年 | 10篇 |
2023年 | 58篇 |
2022年 | 96篇 |
2021年 | 113篇 |
2020年 | 168篇 |
2019年 | 196篇 |
2018年 | 201篇 |
2017年 | 291篇 |
2016年 | 325篇 |
2015年 | 226篇 |
2014年 | 407篇 |
2013年 | 798篇 |
2012年 | 492篇 |
2011年 | 539篇 |
2010年 | 503篇 |
2009年 | 687篇 |
2008年 | 653篇 |
2007年 | 672篇 |
2006年 | 551篇 |
2005年 | 491篇 |
2004年 | 467篇 |
2003年 | 457篇 |
2002年 | 367篇 |
2001年 | 273篇 |
2000年 | 272篇 |
1999年 | 256篇 |
1998年 | 238篇 |
1997年 | 220篇 |
1996年 | 176篇 |
1995年 | 123篇 |
1994年 | 125篇 |
1993年 | 92篇 |
1992年 | 81篇 |
1991年 | 68篇 |
1990年 | 59篇 |
1989年 | 43篇 |
1988年 | 31篇 |
1987年 | 31篇 |
1986年 | 18篇 |
1985年 | 40篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 31篇 |
1981年 | 34篇 |
1980年 | 21篇 |
1979年 | 20篇 |
1978年 | 23篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Jean MAWHIN 《数学年刊B辑(英文版)》2017,38(2):563-578
The existence of a zero for a holomorphic functions on a ball or on a rectangle under some sign conditions on the boundary generalizing Bolzano's ones for real functions on an interval is deduced in a very simple way from Cauchy's theorem for holomorphic functions.A more complicated proof,using Cauchy's argument principle,provides uniqueness of the zero,when the sign conditions on the boundary are strict.Applications are given to corresponding Brouwer fixed point theorems for holomorphic functions.Extensions to holomorphic mappings from Cn to Cn are obtained using Brouwer degree. 相似文献
63.
利用Banach空间中的锥理论和不动点定理讨论了非线性算子方程变号解的存在性,给出了E_u_0空间下非线性算子方程变号解至少有一个变号解、一个正解和一个负解的条件,并讨论了仅通过一个上解条件得出非线性算子方程变号解的存在性定理. 相似文献
64.
65.
基于W Leontief提出的动态投入产出模型,讨论了考虑随机因素的离散时间下的最优策略设计问题.利用博弈论的思想,把动态投入产出系统抽象为离散时间的博弈模型,运用鞍点均衡策略设计出求解该投入产出问题的新方法,为宏观经济决策提供依据. 相似文献
66.
许兴业 《高校应用数学学报(A辑)》2017,32(4)
研究一类奇异非线性多重调和方程?~mu=f(|x|,u,|▽u|)u~(-β),给出了方程存在正的径向对称整体解的充分必要条件和解的性质. 相似文献
67.
About the compatibility between ansatzes and constraints for a local formulation of orbital‐free density functional theory 下载免费PDF全文
Functional properties that are exact for the Hohenberg–Kohn functional may turn into mutually exclusive constraints at a given level of ansatz. This is exemplarily shown for the local density approximation. Nevertheless, it is possible to reach exactly the Kohn–Sham data from an orbital‐free density functional framework based on simple one‐point functionals by starting from the Levy–Perdew–Sahni formulation. The energy value is obtained from the density‐potential pair, and therefore does not refer to the functional dependence of the potential expression. Consequently, the potential expression can be obtained from any suitable model and is not required to follow proper scaling behavior. 相似文献
68.
Song and Mason equation of state (EOS) with a simple modification has been extended to modelling PVT properties of ionic liquids (ILs). The considered ILs are [C1mim][MeSO4], [C1mim][CH3OC2H5SO4], [C1mim][(CH3)2PO4], [C2mim][MeSO4], [C2mim][BF4], [C2mim][SCN], [C2eim][NTf2], [C4mim][C(CN)3], [C4mim][CF3SO3], [C4mim][SCN], [C5mim][NTf2], [C8mim][NTf2], [(C6H13)3P(C14H29)][Cl], [(C6H13)3P(C14H29)][NTf2], [(C6H13)3P(C14H29)][Ac], [C3mpyr][NTf2], [C4mpyr][NTf2] and [Py][C2H5OC2H4SO4]. Three temperature-dependent parameters in the proposed EOS have been scaled as functions of reduced temperature with the use of the law of corresponding states. It is shown that the knowledge of just critical temperature and critical density is sufficient to predict the PVT properties of these ILs. The overall average absolute deviation of calculated densities from literature values for 1347 data points of 18 ILs was found to be 0.58%. The predicted density of ILs from proposed EOS has been compared with those obtained by other literature work. Moreover, we indicate that the Zeno line regularity can well be predicted by proposed model for ILs. 相似文献
69.
《Electrophoresis》2017,38(3-4):460-468
Ultrasound‐assisted extraction (UAE), cloud point extraction (CPE), and ultrasound back‐extraction (UABE) techniques have been coupled for lixiviation, preconcentration, and cleanup of polybrominated diphenyl ethers (PBDEs) from milk samples for determination by gas chromatography‐electron capture detection (GC‐ECD). Physicochemical parameters that affect the efficiency of the extraction system were investigated using a design of experiments based on multivariate statistical tools, and considering the sample matrix along the development. The coupling of the leaching step, UAE, enhanced ca. 3.5 times the extraction efficiency of the former sample preparation methodology (CPE‐UABE) leading to cleaner sample extracts suitable for GC analysis. Under optimum conditions, the proposed methodology exhibits successful performance in terms of linearity and precision, with recoveries in the range of 68–70% and LODs within the range 0.05–0.5 ng/g dry weight (d.w.). The proposed sample preparation methodology coupled three green analytical techniques. It expands the application frontiers of CPE for the analysis of biological samples by GC. The optimized methodology was used for determination of PBDEs in powder milk samples, from both commercial and human sources. 相似文献
70.
Jian Dong Yun Wang Xu Tang Wenli Zhang 《Journal of Dispersion Science and Technology》2017,38(10):1388-1395
The cloud points (CPs) of the copolymers 17R4 and L64 were first measured, and then the effects of salts ((NH4)3C6H5O7, K3C6H5O7) on 17R4 and L64 were researched. After finishing the work described above, the temperature (278.15, 283.15, and 288.15) K of aqueous two-phase systems was determined, which consist of 17R4-(NH4)3C6H5O7, 17R4-K3C6H5O7, L64-(NH4)3C6H5O7, and L64-K3C6H5O7. Finally, the liquid–liquid equilibrium (LLE) data of binodal curve and the tie line for 17R4-(NH4)3C6H5O7 aqueous two- phase systems (ATPSs) 17R4-K3C6H5O7 ATPSs, L64-(NH4)3C6H5O7 ATPSs, and L64-K3C6H5O7 ATPSs were obtained. Nonlinear fitting of the empirical equation was used for making the diagram. The results showed that the change in the size of the two-phase areas increases with the increase of temperature. The capacity of the salts to induce phase segregation follows the Hofmeister series, that is, K3C6H5O7?>?(NH4)3C6H5O7. In addition, the findings also showed that the phase separation ability of 17R4 is better than that of L64. 相似文献