全文获取类型
收费全文 | 33033篇 |
免费 | 1269篇 |
国内免费 | 248篇 |
专业分类
化学 | 23157篇 |
晶体学 | 275篇 |
力学 | 679篇 |
综合类 | 1篇 |
数学 | 5750篇 |
物理学 | 4688篇 |
出版年
2023年 | 161篇 |
2022年 | 159篇 |
2021年 | 364篇 |
2020年 | 610篇 |
2019年 | 599篇 |
2018年 | 418篇 |
2017年 | 386篇 |
2016年 | 942篇 |
2015年 | 826篇 |
2014年 | 1004篇 |
2013年 | 1702篇 |
2012年 | 2180篇 |
2011年 | 2462篇 |
2010年 | 1297篇 |
2009年 | 1125篇 |
2008年 | 2219篇 |
2007年 | 2028篇 |
2006年 | 2066篇 |
2005年 | 1899篇 |
2004年 | 1633篇 |
2003年 | 1324篇 |
2002年 | 1111篇 |
2001年 | 317篇 |
2000年 | 321篇 |
1999年 | 262篇 |
1998年 | 238篇 |
1997年 | 360篇 |
1996年 | 384篇 |
1995年 | 286篇 |
1994年 | 354篇 |
1993年 | 322篇 |
1992年 | 288篇 |
1991年 | 267篇 |
1990年 | 237篇 |
1989年 | 204篇 |
1988年 | 204篇 |
1987年 | 218篇 |
1986年 | 172篇 |
1985年 | 371篇 |
1984年 | 327篇 |
1983年 | 274篇 |
1982年 | 337篇 |
1981年 | 276篇 |
1980年 | 286篇 |
1979年 | 239篇 |
1978年 | 226篇 |
1977年 | 217篇 |
1976年 | 207篇 |
1975年 | 186篇 |
1974年 | 160篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
Journal of Global Optimization - 相似文献
2.
We discuss the length of the longest directed cycle in the sparse random digraph , constant. We show that for large there exists a function such that a.s. The function where is a polynomial in . We are only able to explicitly give the values , although we could in principle compute any . 相似文献
3.
Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function... 相似文献
4.
Computational Optimization and Applications - It has been shown that a global minimizer of a smooth determinant of a matrix function corresponds to the largest cycle of a graph. When it exists,... 相似文献
5.
Poulou Maria Eleni Filippakis Michael E. 《Journal of Dynamics and Differential Equations》2022,34(2):945-960
Journal of Dynamics and Differential Equations - In this paper we study the local and global well posedness of a fractional dissipative Klein–Gordon–Schrödinger type system in... 相似文献
6.
7.
Veenu Bala Yashpal S. Chhonker Richard L. Sleightholm Ayrianne J. Crawford Michael A. Hollingsworth Daryl J. Murry 《Biomedical chromatography : BMC》2020,34(8):e4859
A rapid, selective, and sensitive liquid chromatography coupled with tandem mass spectrometry (MS/MS) method was developed and validated for the quantitation of the novel CDK5 inhibitor ‘20–223' in mouse plasma. Separation of analytes was achieved by a reverse-phase ACE Excel C18 column (1.7 μm, 100 × 2.1 mm) with gradient elution using 0.1% formic acid (FA) in methanol and 0.1% FA as the mobile phase. Analytes were monitored by MS/MS with an electrospray ionization source in the positive multiple reaction monitoring mode. The MS/MS response was linear over the concentration range 0.2–500 ng/mL for 20–223. The within- and between-batch precision were within the acceptable limits as per Food and Drug Administration guidelines. The validated method was successfully applied to plasma protein binding and in vitro metabolism studies. Compound 20–223 was highly bound to mouse plasma proteins (>98% bound). Utilizing mouse S9 fractions, in vitro intrinsic clearance (CLint) was 24.68 ± 0.99 μL/min/mg protein. A total of 12 phase I and II metabolites were identified with hydroxylation found to be the major metabolic pathway. The validate method required a low sample volume, was linear from 0.2 to 500 ng/mL, and had acceptable accuracy and precision. 相似文献
8.
Bijit Mukherjee K. R. Shamasundar Satrajit Adhikari Michael Baer 《International journal of quantum chemistry》2019,119(16):e25949
In the present article are analyzed the non-adiabatic coupling terms (NACT) for two molecular systems, namely H3+ and H3. In contrast to previous occasions in which the NACTs are studied along (closed) circular contours usually surrounding conical intersections (ci), in the present article are studied distribution of the NACTs in (planar) configuration spaces (CS). The motivation for this study has to do with a novel idea being mentioned earlier (Molec. Phys., 116, 2435 [2018]; ArXiv:1801.00103) that NACTs are like a Glue (eventually) associated with the ability of creating molecules and/or protecting them from breaking up. It was found that the distributions of the NACTs due to the two molecules are similar as long as the attention is given to regions close to their equilateral cis, but then they behave significantly different in other regions. In case of H3+, the NACTs are distributed rather uniformly whereas, in case of H3 they become spiky the closer they approach the diatom axis. The main conclusion of this study is that the glue which has its origin in the NACTs is most likely to be effective in case of H3+ that explains the creation and later survival of this molecule. 相似文献
9.
Huixin Wang Dr. Michael G. Leeming Dr. Junming Ho Dr. William A. Donald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):823-834
Predicting the fragmentation patterns of proteins would be beneficial for the reliable identification of intact proteins by mass spectrometry. However, the ability to accurately make such predictions remains elusive. An approach to predict the specific cleavage sites in whole proteins resulting from collision-induced dissociation by use of an improved electrostatic model for calculating the proton configurations of highly-charged protein ions is reported. Using ubiquitin, cytochrome c, lysozyme and β-lactoglobulin as prototypical proteins, this approach can be used to predict the fragmentation patterns of intact proteins. For sufficiently highly charged proteins, specific cleavages occur near the first low-basicity amino acid residues that are protonated with increasing charge state. Hybrid QM/QM′ (QM=quantum mechanics) and molecular dynamics (MD) simulations and energy-resolved collision-induced dissociation measurements indicated that the barrier to the specific dissociation of the protonated amide backbone bond is significantly lower than competitive charge remote fragmentation. Unlike highly charged peptides, the protons at low-basicity sites in highly charged protein ions can be confined to a limited sequence of low-basicity amino acid residues by electrostatic repulsion, which results in highly specific fragmentation near the site of protonation. This research suggests that the optimal charge states to form specific sequence ions of intact proteins in higher abundances than the use of less specific ion dissociation methods can be predicted a priori. 相似文献
10.
Christopher Lombardi Dr. Richard P. Rucker Dr. Robert D. J. Froese Dr. Sepideh Sharif Prof. Pier Alexandre Champagne Prof. Michael G. Organ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(62):14223-14229
The relative rates of arylation of primary alkylamines with different Pd-NHC catalysts have been measured, as have the relative rates of arylation of the secondary aniline product in an attempt to understand the key ligand design features necessary to have high selectivity for the monoarylated amine product. As the substituents on the N-aryl ring of the NHC increase in size, selectivity for monoarylation increases and this is further enhanced by chlorinating the back of the NHC ring. Computations have been performed on the catalytic cycle of this transformation in order to understand the selectivity obtained with the different catalysts. 相似文献