全文获取类型
收费全文 | 140429篇 |
免费 | 36135篇 |
国内免费 | 28995篇 |
专业分类
化学 | 63097篇 |
晶体学 | 1243篇 |
力学 | 6306篇 |
综合类 | 250篇 |
数学 | 11921篇 |
物理学 | 59603篇 |
综合类 | 63139篇 |
出版年
2024年 | 682篇 |
2023年 | 1397篇 |
2022年 | 1868篇 |
2021年 | 2018篇 |
2020年 | 2901篇 |
2019年 | 5795篇 |
2018年 | 5733篇 |
2017年 | 6586篇 |
2016年 | 7303篇 |
2015年 | 7429篇 |
2014年 | 7662篇 |
2013年 | 9152篇 |
2012年 | 9284篇 |
2011年 | 10643篇 |
2010年 | 13549篇 |
2009年 | 13150篇 |
2008年 | 6606篇 |
2007年 | 5974篇 |
2006年 | 5113篇 |
2005年 | 5382篇 |
2004年 | 6464篇 |
2003年 | 5266篇 |
2002年 | 5070篇 |
2001年 | 4669篇 |
2000年 | 3574篇 |
1999年 | 3946篇 |
1998年 | 3200篇 |
1997年 | 3064篇 |
1996年 | 3217篇 |
1995年 | 3530篇 |
1994年 | 3572篇 |
1993年 | 3657篇 |
1992年 | 3151篇 |
1991年 | 2810篇 |
1990年 | 2322篇 |
1989年 | 2334篇 |
1988年 | 2339篇 |
1987年 | 1436篇 |
1986年 | 1417篇 |
1985年 | 1021篇 |
1984年 | 1044篇 |
1982年 | 923篇 |
1981年 | 757篇 |
1980年 | 778篇 |
1979年 | 533篇 |
1978年 | 531篇 |
1977年 | 633篇 |
1976年 | 1041篇 |
1973年 | 437篇 |
1972年 | 532篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
2.
3.
随着城市化高速发展,老厂房再利用的问题日益急迫.上海是中国近代工业起源地,也是率先着手对彰显城市文脉的工业遗产进行调查和保护的历史文化名城.本文以上海典型案例入手,分析了具有代表性的老厂房改造的项目特点,并在此基础上,对常州大成三厂这一民国时期的纺织业遗留地块进行改造设计手法进行介绍,从设计理念、设计内容和节点设计3个方面,体现了文化传承和生态技术相融合理念. 相似文献
4.
5.
6.
Geochemistry of Clayey Aquitard Pore Water as Archive of Paleo-Environment,Western Bohai Bay 总被引:1,自引:0,他引:1
The record of paleo-environment in clayey aquitard pore water is much more effective relative to aquifer groundwater owing to the low permeability of clayey aquitard. Oxygen-18 (18O), deuterium (D), an... 相似文献
7.
Star copolymers have attracted significant interest due to their different characteristics compared with diblock copolymers, including higher critical micelle concentration, lower viscosity, unique spatial shape, or morphologies. Development of synthetic skills such as anionic polymerization and controlled radical polymerization have made it possible to make diverse architectures of polymers. Depending on the molecular architecture of the copolymer, numerous morphologies are possible, for instance, Archimedean tiling patterns and cylindrical microdomains at symmetric volume fraction for miktoarm star copolymers as well as asymmetric lamellar microdomains for star‐shaped copolymers, which have not been reported for linear block copolymers. In this review, we focus on morphologies and microphase separations of miktoarm (AmBn and ABC miktoarm) star copolymers and star‐shaped [(A‐b‐B)n] copolymers with nonlinear architecture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1–21 相似文献
8.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献
9.
In order to improve the efficiency of 3D near-surface velocity model building, we develop a layer-stripping method using seismic first-arrival times. The velocity model within a Common Mid-Point (CMP) ... 相似文献
10.
L油田B区块开展"二三结合"实验区,"二三结合"开发模式渗流特征对区块的合理高效开发具有重要意义。为了明确其渗流特征,利用油藏数值模拟软件Eclipse建立代表意义的油藏数值模型,研究区块"二三结合"开发模式下原射孔层和补孔层的渗流特征,分析了"二三结合"开发模式下,不同开发阶段综合含水率、采出程度、井底压力、地层压力及含水饱和度的变化特征。研究表明,"二三结合"开发模式先通过水驱开发挖潜原射孔层剩余油,提高厚油层顶部剩余油的采出程度,再通过聚合物驱进一步提高开发效果,通过水驱与聚驱的综合作用,最终得到较好的开发效果。 相似文献