全文获取类型
收费全文 | 144344篇 |
免费 | 14679篇 |
国内免费 | 9031篇 |
专业分类
化学 | 49638篇 |
晶体学 | 2152篇 |
力学 | 10016篇 |
综合类 | 1719篇 |
数学 | 41073篇 |
物理学 | 63456篇 |
出版年
2023年 | 804篇 |
2022年 | 2689篇 |
2021年 | 2547篇 |
2020年 | 2167篇 |
2019年 | 2353篇 |
2018年 | 2157篇 |
2017年 | 2443篇 |
2016年 | 2612篇 |
2015年 | 2381篇 |
2014年 | 4038篇 |
2013年 | 6110篇 |
2012年 | 4330篇 |
2011年 | 5223篇 |
2010年 | 5551篇 |
2009年 | 10436篇 |
2008年 | 11690篇 |
2007年 | 10369篇 |
2006年 | 8935篇 |
2005年 | 6646篇 |
2004年 | 6359篇 |
2003年 | 6265篇 |
2002年 | 9159篇 |
2001年 | 5614篇 |
2000年 | 5091篇 |
1999年 | 4774篇 |
1998年 | 4064篇 |
1997年 | 3118篇 |
1996年 | 2794篇 |
1995年 | 3170篇 |
1994年 | 2925篇 |
1993年 | 2412篇 |
1992年 | 1864篇 |
1991年 | 1458篇 |
1990年 | 1182篇 |
1989年 | 991篇 |
1988年 | 1002篇 |
1987年 | 717篇 |
1986年 | 508篇 |
1985年 | 1385篇 |
1984年 | 934篇 |
1983年 | 695篇 |
1982年 | 973篇 |
1981年 | 1143篇 |
1980年 | 1027篇 |
1979年 | 921篇 |
1978年 | 824篇 |
1977年 | 707篇 |
1976年 | 674篇 |
1974年 | 430篇 |
1973年 | 560篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
Monomeric sarcosine oxidase (mSOx) fusion with the silaffin peptide, R5, designed previously for easy protein production in low resource areas, was used in a biosilification process to form an enzyme layer electrode biosensor. mSOx is a low activity enzyme (10–20 U/mg) requiring high amounts of enzyme to obtain an amperometric biosensor signal, in the clinically useful range <1 mM sarcosine, especially since the Km is >10 mM. An amperometric biosensor model was fitted to experimental data to investigate dynamic range. mSOx constructs were designed with 6H (6×histidine) and R5 (silaffin) peptide tags and compared with native mSOx. Glutaraldehyde (GA) cross‐linked proteins retained ~5 % activity for mSOx and mSOx‐6H and only 0.5 % for mSOx‐R5. In contrast R5 catalysed biosilification on (3‐mercaptopropyl) trimethoxysilane (MPTMS) and tetramethyl orthosilicate (TMOS) particles created a ‘self‐immobilisation’ matrix retaining 40 % and 76 % activity respectively. The TMOS matrix produced a thick layer (>500 μm) on a glassy carbon electrode with a mediated current due to sarcosine in the clinical range for sarcosinemia (0–1 mM). The mSOx‐R5 fusion protein was also used to catalyse biosilification in the presence of creatinase and creatininase, entrapping all three enzymes. A mediated GC enzyme linked current was obtained with dynamic range available for creatinine determination of 0.1–2 mM for an enzyme layer ~800 nm. 相似文献
22.
We generalize Nagel’s formula for the Szegö kernel and use it to compute the Szegö kernel on a class of non-compact CR manifolds whose tangent space decomposes into one complex direction and several totally real directions. We also discuss the control metric on these manifolds and relate it to the size of the Szegö kernel. 相似文献
23.
24.
25.
Bobby Wilson 《偏微分方程通讯》2015,40(8):1521-1542
This article explores the questions of long time orbital stability in high order Sobolev norms of plane wave solutions to the NLSE in the defocusing case. 相似文献
26.
Rong Yin Jihui Zhang Xudong Shang 《Mathematical Methods in the Applied Sciences》2020,43(15):8736-8752
This paper is dedicated to studying the following Schrödinger–Poisson system Under some different assumptions on functions V(x), K(x), a(x) and f(u), by using the variational approach, we establish the existence of positive ground state solutions. 相似文献
27.
Recent Progress in the $L_p$ Theory for Elliptic and Parabolic Equations with Discontinuous Coefficients
下载免费PDF全文
![点击此处可从《分析论及其应用》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hongjie Dong 《分析论及其应用》2020,36(2):161-199
In this paper, we review some results over the last 10-15 years on elliptic and parabolic equations with discontinuous coefficients. We begin with an approach given by N. V. Krylov to parabolic equations in the whole space with $\rm{VMO}_x$ coefficients. We then discuss some subsequent development including elliptic and parabolic equations with coefficients which are allowed to be merely measurable in one or two space directions, weighted $L_p$estimates with Muckenhoupt ($A_p$) weights, non-local elliptic and parabolic equations, as well as fully nonlinear elliptic and parabolic equations. 相似文献
28.
《Comptes Rendus Physique》2019,20(3):204-217
Disaster relief requires many resources. Depending on the circumstances of each event, it is important to rapidly choose the suitable means to respond to the emergency intervention. A brief review of the conditions and means demonstrated the usefulness of an autonomous stand-alone machine for these missions. If many techniques and technologies exist, their relevant combination to achieve such a system presents several challenges. This communication tries to outline the possible achievement of an autonomous vehicle under these particular circumstances. This paper focuses on the specific working conditions and welcomes future contributions from robotics and artificial intelligence.In the necessarily limited scope of this article, the authors focus on a particularly critical aspect: location. Indeed, this machine is intended to evolve in heterogeneous and dangerous environment and without any outside contacts that could last up to several days. This blackout, due to the propagation difficulties of electromagnetic waves in the ground, induces an independence of the localisation process and makes the use of any radio navigation support system (GNSS), most of the time, impossible. The knowledge of the position of the system, both for navigation of the autonomous system (Rover) and location of targets (victims buried under debris) must be able to be estimated without contributions from external systems. Inertial classical techniques, odometer, etc., have to be adapted to these conditions during a long period without external support. These techniques also have to take into account that energy optimisation requests the use of low-power processors. Consequently, only poor computing capacity is available on-board.The article starts with a presentation of the context of a post-disaster situation as well as the main missions of Search and Rescue (SaR). It is followed by the analysis of autonomous navigation located in a post-earthquake situation. We will then discuss means to determine the attitude of the autonomous system and its position. The interest of hybridisation with external systems – whenever possible –, will be evaluated with a view to correcting deviations suffered by the system during its mission. Finally, prospects and future work are presented. 相似文献
29.