全文获取类型
收费全文 | 19812篇 |
免费 | 2586篇 |
国内免费 | 2447篇 |
专业分类
化学 | 14678篇 |
晶体学 | 265篇 |
力学 | 957篇 |
综合类 | 235篇 |
数学 | 2383篇 |
物理学 | 6327篇 |
出版年
2024年 | 20篇 |
2023年 | 198篇 |
2022年 | 305篇 |
2021年 | 493篇 |
2020年 | 536篇 |
2019年 | 616篇 |
2018年 | 529篇 |
2017年 | 530篇 |
2016年 | 847篇 |
2015年 | 852篇 |
2014年 | 1098篇 |
2013年 | 1438篇 |
2012年 | 1560篇 |
2011年 | 1814篇 |
2010年 | 1337篇 |
2009年 | 1362篇 |
2008年 | 1568篇 |
2007年 | 1385篇 |
2006年 | 1330篇 |
2005年 | 1144篇 |
2004年 | 946篇 |
2003年 | 779篇 |
2002年 | 940篇 |
2001年 | 622篇 |
2000年 | 536篇 |
1999年 | 357篇 |
1998年 | 238篇 |
1997年 | 196篇 |
1996年 | 174篇 |
1995年 | 120篇 |
1994年 | 104篇 |
1993年 | 94篇 |
1992年 | 96篇 |
1991年 | 70篇 |
1990年 | 69篇 |
1989年 | 71篇 |
1988年 | 51篇 |
1987年 | 37篇 |
1986年 | 27篇 |
1985年 | 45篇 |
1984年 | 30篇 |
1983年 | 22篇 |
1982年 | 20篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1978年 | 28篇 |
1977年 | 22篇 |
1976年 | 16篇 |
1975年 | 12篇 |
1970年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
81.
Yong LU Hong WANG Ye LIU Ming Yuan HE 《中国化学快报》2006,17(10):1397-1400
Recently, miniature H2 generator to power fuel cells for portable/micro electronic devices and passenger propulsion has been the focus of intense research activities1-3. One of the strategies is to find simple CO-free H2 production with novel microreactor… 相似文献
82.
83.
84.
85.
TieYong YangGuangjun 《分析论及其应用》2004,20(1):58-68
In this paper, we construct some continuous but non-differentiable functions defined by quinary decimal, that are Kiesswetter-like functions. We discuss their properties, then investigate the Hausdorff dimensions of graphs of these functions and give a detailed proof. 相似文献
86.
Il Bong Jung Alan Lambert Jan Stochel 《Proceedings of the American Mathematical Society》2004,132(8):2291-2302
The concept of backward extension for subnormal weighted shifts is generalized to arbitrary subnormal operators. Several differences and similarities in these contexts are explored, with emphasis on the structure of the underlying measures.
87.
A novel measurement method of temperature based on the phenomena that the phase difference between principle polarization states in the optical retarder is function of temperature is described. The polarization state of optical beam is changed as it passes through the optical retarder, which depends on the temperature. The temperature of optical retarder is determined by comparison of the power difference between principal polarization states. We demonstrate successfully the temperature measurement by using a polarization maintaining fiber as the optical retarder. With a 100 mm length of the fiber optic retarder, the change rate of phase difference on temperature was 0.236 rad/°C and the measurement error was ±0.038°C over the temperature range of −2.6 – +3.4°C. With a 11.5 mm length of the fiber optic retarder, the change rate of phase difference on temperature was 0.021 rad/°C and the measurement error was ±0.79°C over the temperature range of −8.5 – +86.5°C. 相似文献
88.
A periodic one-dimensional four-state hopping model is proposed. In the model, the substeps betweenarbitrary adjacent states are unequal, and an explicit solution of the master equation is first obtained for the probabilitydistribution as a function of the time and position for any initial distribution with all the transients included. Next, thetransient behaviors in the initial period of time and the characteristic time to reach the steady state for the molecularmotor are discussed. Finally, we compare the steady state results to experiments and illustrate qualitatively the kineticbehaviors of a molecular motor under external load F. 相似文献
89.
A new chemiluminescence method for the determination of carbamazepine (CBZ) has been developed. The method is based on the chemiluminescence produced in the reaction of tris(2,2'-bipyridine)ruthenium(III) and CBZ in an acidic medium. The chemiluminescence intensity was enhanced by organic solvents in the reaction system. Under the optimum experimental conditions, the calibration curve was linear over the range 4.0 x 10(-3)-8.6 x 10(-7) mol/L for CBZ. The detection limit (S/N = 3) was 2.5 x 10(-7) mol/L and the relative standard deviation of six replicate measurements was 2.6% for 4.0 x 10(-4) mol/L of CBZ. The possible reaction mechanism were also discussed. The chemiluminescence method was successfully applied to assay the CBZ contents in pharmaceutical tablets. 相似文献
90.
This paper is to investigate the approximate confidence limits of the reliability performances (such as failure rate, reliability function and average life) for a cold standby series system. The Bayesian approximate upper confidence limit of failure rate is obtained firstly, and next Bayesian approximate lower confidence limits for reliability function and average life are presented. The expressions for calculating Bayesian lower confidence limits of the reliability function and average life are also obtained, and an illustrative example is examined numerically by means of the Monte-Carlo simulation. Finally, the accuracy of confidence limits is discussed. 相似文献