全文获取类型
收费全文 | 24231篇 |
免费 | 2485篇 |
国内免费 | 4485篇 |
专业分类
化学 | 16847篇 |
晶体学 | 479篇 |
力学 | 1123篇 |
综合类 | 651篇 |
数学 | 3223篇 |
物理学 | 8878篇 |
出版年
2023年 | 128篇 |
2022年 | 450篇 |
2021年 | 524篇 |
2020年 | 475篇 |
2019年 | 497篇 |
2018年 | 490篇 |
2017年 | 629篇 |
2016年 | 672篇 |
2015年 | 810篇 |
2014年 | 968篇 |
2013年 | 1592篇 |
2012年 | 1375篇 |
2011年 | 1535篇 |
2010年 | 1374篇 |
2009年 | 1377篇 |
2008年 | 1677篇 |
2007年 | 1592篇 |
2006年 | 1483篇 |
2005年 | 1371篇 |
2004年 | 1217篇 |
2003年 | 1013篇 |
2002年 | 1064篇 |
2001年 | 936篇 |
2000年 | 959篇 |
1999年 | 642篇 |
1998年 | 399篇 |
1997年 | 352篇 |
1996年 | 360篇 |
1995年 | 364篇 |
1994年 | 359篇 |
1993年 | 295篇 |
1992年 | 279篇 |
1991年 | 248篇 |
1990年 | 281篇 |
1989年 | 234篇 |
1988年 | 219篇 |
1987年 | 200篇 |
1986年 | 175篇 |
1985年 | 248篇 |
1984年 | 261篇 |
1983年 | 194篇 |
1982年 | 197篇 |
1981年 | 161篇 |
1980年 | 161篇 |
1979年 | 157篇 |
1978年 | 120篇 |
1977年 | 164篇 |
1976年 | 142篇 |
1975年 | 122篇 |
1973年 | 115篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
81.
We study the propagation of the light mesons σ,ω,ρ, and a0(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible
to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric
nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation
of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated.
Received: 16 October 2001 / Accepted: 10 January 2002 相似文献
82.
Summary We study the integration theory for general integral metrics when restricted to upper integrals q, finding improvements in the relation between the classes of the q-integrable and the ql-integrable functions. We give new results and notions which lead to the desirable characterizations of q-integrable functions as ql-integrable f with q(|f|) < ∞, and of ql-integrable functions via the integrability of their upper truncations, under natural conditions which are fulfilled in most
finitely additive integration theories. 相似文献
83.
This paper formulates a two-dimensional strip packing problem as a non-linear programming(NLP)problem and establishes the first-order optimality con-ditions for the NLP problem.A numerical algorithm for solving this NLP problemis given to find exact solutions to strip-packing problems involving up to 10 items.Approximate solutions can be found for big-sized problems by decomposing the setof items into small-sized blocks of which each block adopts the proposed numericalalgorithm.Numerical results show that the approximate solutions to big-sized prob-lems obtained by this method are superior to those by NFDH,FFDH and BFDHapproaches. 相似文献
84.
85.
86.
通过PCR扩增出猪传染性胃肠炎病毒(TGEV)聚合酶部分片段,反向插入逆转录病毒表达载体pLXSN中,用脂质体法将重组质粒plxas-pol转染PA317细胞,经抗生素G418筛选出稳定的产毒细胞克隆,分别扩大培养后,取其上清液感染小鼠成纤维细胞NIH3T3,细胞克隆产生的重组病毒效价达9.0×105CFU/mL。用高效价假病毒感染IBRS2细胞,再经抗生素G418筛选,提取细胞克隆总RNA,经RT-PCR证明plxas-pol整合入IBRS2细胞。以TGEV感染IBRS2细胞和具有抗性的IBRS2细胞所产生的细胞病变为指标,证明该反义RNA对病毒有明显抑制作用,抑制率约为80%。用2×103和4×102TCID50/mL剂量的TGEV感染时,引起细胞死亡的时间分别为21 h和27 h,与对照组相比,抗性细胞系可明显延迟因病毒感染引起细胞死亡的时间。 相似文献
87.
We present a scheme for perfectly teleporting an arbitrary and unknown N-particle GHZ-class state from a sender to a receiver. We just need one quantum channel composed of two or three particles in the maximally entangled state. The sender performs one Bell-state measurement on two of her particles and N - 1 Hadamard operations and N - 1 yon Neumann measurements on the rest N - 1 particles. The receiver adopts one corresponding unitary transformation on his particles shared with the sender. After that, the receiver can obtain the original N-particle GHZ-class state by introducing N - 1 ancillary particles and carrying out N - 1 controlled-NOT operations. We also generalize the scheme to the case of controlled teleportation. 相似文献
88.
Application of Electron-Shelving Detection via 423 nm Transition in Calcium-Beam Optical Frequency Standard
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A new scheme of small compact optical frequency standard based on thermal calcium beam with application of 423 nm shelving detection and sharp-angle velocity selection detection is proposed. Combining these presented techniques, we conclude that a small compact optical frequency standard based on thermal calcium beam will outperform the commercial caesium-beam microwave dock, like the 5071 Cs clock (from Hp to Agilent, now Symmetricom company), both in accuracy and stability. 相似文献
89.
90.
It is well known that potassium ion channels have higher permeability than K ions, and the permeable rate of a single K ion channel is about 108 ions per second. We develop a hierarchical model of potassium ion channel permeation involving ab initio quantum calculations and Brownian dynamics simulations, which can consistently explain a range of channel dynamics. The results show that the average velocity of K ions, the mean permeable time of K ions and the permeable rate of single channel are about 0.92nm/ns, 4.35ns and 2.30 ×10^8 ions/s, respectively. 相似文献