全文获取类型
收费全文 | 3177篇 |
免费 | 46篇 |
国内免费 | 488篇 |
专业分类
化学 | 2297篇 |
晶体学 | 7篇 |
力学 | 122篇 |
综合类 | 4篇 |
数学 | 545篇 |
物理学 | 736篇 |
出版年
2024年 | 22篇 |
2023年 | 47篇 |
2022年 | 63篇 |
2021年 | 46篇 |
2020年 | 63篇 |
2019年 | 57篇 |
2018年 | 31篇 |
2017年 | 12篇 |
2016年 | 34篇 |
2015年 | 71篇 |
2014年 | 144篇 |
2013年 | 174篇 |
2012年 | 103篇 |
2011年 | 64篇 |
2010年 | 83篇 |
2009年 | 53篇 |
2008年 | 167篇 |
2007年 | 235篇 |
2006年 | 415篇 |
2005年 | 308篇 |
2004年 | 186篇 |
2003年 | 101篇 |
2002年 | 107篇 |
2001年 | 173篇 |
2000年 | 276篇 |
1999年 | 206篇 |
1998年 | 113篇 |
1997年 | 60篇 |
1996年 | 55篇 |
1995年 | 89篇 |
1994年 | 48篇 |
1993年 | 33篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1948年 | 3篇 |
排序方式: 共有3711条查询结果,搜索用时 15 毫秒
21.
Tatsien LI 《数学年刊B辑(英文版)》2007,28(3):265-282
In this paper, the authors consider the inverse piston problem for the system of one-dimensional isentropic flow and obtain that, under suitable conditions, the piston velocity can be uniquely determined by the initial state of the gas on the right side of the piston and the position of the forward shock. 相似文献
22.
ZHANG Lin-bo LIU Xiao-hua ** JIANG Yuan GUO Ping SHA Li-jin LI Yu . Institute of Mycology . College of Biotechnology Jilin Agricultural University Changchun P.R. China 《高等学校化学研究》2006,(2)
Introduction Parkinson′sdisease(PD),alsocalledshaking palsy,isaneurodegenerativedisorderandfrequently occursinthepeopleabovetheageof65[1].PDisa relativelycommonneurodegenerativedisorder,which hasclinicalsymptomsincludingbradykinesia,rest tremor,rigidity,… 相似文献
23.
Hong Ming ZHANG Xian Hong WANG Xiao Jiang ZHAO Ji LI Fo Song WANG 《中国化学快报》2006,17(4):437-440
A novel method for the preparation of oligothiophene molecular wires is described via a bi-directional solid-phase synthesis. Using an alternating sequence of bromination and Stille coupling reactions, oligomers were obtained up to the heptamer in excellent yield and purity. 相似文献
24.
In market, excess demands for many products can be met by reorder even during one period, and retailers usually adopt substitution strategy for more benefit. Under the retailer's substitution strategy and permission of reorder, we develop the profits maximization model for the two-substitutable-product inventory problem with stochastic demands and proportional costs and revenues. We show that the objective function is concave and submodular, and therefore the optimal policy exists. We present the optimal conditions for order quantity and provide some properties of the optimal order quantities. Comparing our model with Netessine and Rudi's, we prove that reorder and adoption of the substitution strategy can raise the general profits and adjust down the general stock level. 相似文献
25.
Acoustic vector sensor signal processing 总被引:2,自引:0,他引:2
SUN Guiqing LI Qihu ZHANG Bin 《声学学报:英文版》2006,25(1):1-15
Acoustic vector sensor simultaneously, colocately and directly measures orthogonal components of particle velocity as well as pressure at single point in acoustic field so that is possible to improve performance of traditional underwater acoustic measurement devices or detection systems and extends new ideas for solving practical underwater acoustic engineering problems. Although acoustic vector sensor history of appearing in underwater acoustic area is no long, but with huge and potential military demands, acoustic vector sensor has strong development trend in last decade, it is evolving into a one of important underwater acoustic technology. Under this background, we try to review recent progress in study on acoustic vector sensor signal processing, such as signal detection, DOA estimation, beamforming, and so on. 相似文献
26.
LIU Biao BAO Yong-li WEI Zhuang WU Yin MENG Xiang-ying LI Yu-xin YIN Wei-tian 《高等学校化学研究》2006,22(2):217-220
Introduction Activinisamemberofthetransforminggrowth factor(TGF)βsuperfamilyofextracellularsignaling proteins.Themembersofthisfamilyplayacriticalrole duringembryogenesisandinmaintainingtissuehomeo stasisinadultlife[1—3].DeregulatedTGFfamilysigna lingisi… 相似文献
27.
LI Ya-feng~ ** ZHANG Li-mei~ WU Lei-lei~ WANG Sheng-hai~ WANG Hai-lian~ SHANG Xuan-xuan~ . College of Chemistry Molecular Engineering . College of Mathematics Physics Qingdao University of Science & Technology Qingdao P. R. China 《高等学校化学研究》2006,(6)
IntroductionThe interest in polyoxometalates that are widelyused in medical chemistry, catalyst reactions, and ma-terial sciences stems from their complicated aggregatesformed by means of corner-, edge- and face-sha-ring[1—4]. The exploitation of new str… 相似文献
28.
The reference [4] proved the consistency of S1 and S2 among Lewis' five strict implication systems in the modal logic by using the method of the Boolean-valued model. But, in this method, the consistency of S3, S4 and S5 in Lewis' five strict implication systems is not decided. This paper makes use of the properties: (1) the equivalence of the modal systems S3 and P3, S4 and P4; (2) the modal systems P3 and P4 all contained the modal axiom T(□p → p); (3) the modal axiom T is correspondence to the reflexive property in VB. Hence, the paper proves: (a) ‖As31‖ = 1; (b) ‖AS41‖ = 1; (c) ‖AS5l‖ = 1 in the model (where B is a complete Boolean algebra, R is reflexive property in VB). Therefore, the paper finally proves that the Boolean-valued model VB of the ZFC axiom system in set theory is also a Boolean-valued model of Lewis' the strict implication system S3, S4 and S5. 相似文献
29.
A filled function with adjustable parameters is suggested in this paper for finding a global minimum point of a general class of nonlinear programming problems with a bounded and closed domain. This function has two adjustable parameters. We will discuss the properties of the proposed filled function. Conditions on this function and on the values of parameters are given so that the constructed function has the desired properties of traditional filled function. 相似文献
30.
Navier-Stokes方程带Backtracking技巧的两重网格算法 总被引:3,自引:1,他引:2
1 引 言考虑二维不可压 Navier-Stokes方程: 相似文献