全文获取类型
收费全文 | 4532篇 |
免费 | 138篇 |
国内免费 | 16篇 |
专业分类
化学 | 2867篇 |
晶体学 | 13篇 |
力学 | 238篇 |
数学 | 797篇 |
物理学 | 771篇 |
出版年
2023年 | 40篇 |
2022年 | 136篇 |
2021年 | 132篇 |
2020年 | 109篇 |
2019年 | 97篇 |
2018年 | 82篇 |
2017年 | 91篇 |
2016年 | 186篇 |
2015年 | 143篇 |
2014年 | 139篇 |
2013年 | 245篇 |
2012年 | 258篇 |
2011年 | 286篇 |
2010年 | 171篇 |
2009年 | 149篇 |
2008年 | 279篇 |
2007年 | 268篇 |
2006年 | 221篇 |
2005年 | 236篇 |
2004年 | 162篇 |
2003年 | 156篇 |
2002年 | 112篇 |
2001年 | 49篇 |
2000年 | 47篇 |
1999年 | 44篇 |
1998年 | 32篇 |
1997年 | 31篇 |
1996年 | 52篇 |
1995年 | 44篇 |
1994年 | 37篇 |
1993年 | 34篇 |
1992年 | 26篇 |
1991年 | 27篇 |
1990年 | 28篇 |
1989年 | 29篇 |
1988年 | 30篇 |
1987年 | 39篇 |
1986年 | 23篇 |
1985年 | 39篇 |
1984年 | 38篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 19篇 |
1978年 | 16篇 |
1977年 | 28篇 |
1975年 | 14篇 |
1974年 | 13篇 |
1858年 | 11篇 |
排序方式: 共有4686条查询结果,搜索用时 15 毫秒
181.
Molecular Size and Electronic Structure Combined Effects on the Electrogenerated Chemiluminescence of Sulfurated Pyrene‐Cored Dendrimers 下载免费PDF全文
Dr. Giovanni Valenti Dr. Andrea Fiorani Dr. Simone Di Motta Dr. Giacomo Bergamini Prof. Marc Gingras Prof. Paola Ceroni Prof. Fabrizia Negri Prof. Francesco Paolucci Prof. Massimo Marcaccio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2936-2947
The electrochemistry, photophysics, and electrochemically generated chemiluminescence (ECL) of a family of polysulfurated dendrimers with a pyrene core have been thoroughly investigated and complemented by theoretical calculations. The redox and luminescence properties of dendrimers are dependent on the generation number. From low to higher generation it is both easier to reduce and oxidize them and the emission efficiency increases along the family, with respect to the polysulfurated pyrene core. The analysis of such data evidences that the formation of the singlet excited state by cation–anion annihilation is an energy‐deficient process and, thus, the ECL has been justified through the triplet–triplet annihilation pathway. The study of the dynamics of the ECL emission was achieved both experimentally and theoretically by molecular mechanics and quantum chemical calculations. It has allowed rationalization of a possible mechanism and the experimental dependence of the transient ECL on the dendrimer generation. The theoretically calculated Marcus electron‐transfer rate constant compares very well with that obtained by the finite element simulation of the whole ECL mechanism. This highlights the role played by the thioether dendrons in modulating the redox and photophysical properties, responsible for the occurrence and dynamics of the electron transfer involved in the ECL. Thus, the combination of experimental and computational results allows understanding of the dendrimer size dependence of the ECL transient signal as a result of factors affecting the annihilation electron transfer. 相似文献
182.
Structural Chemistry - The best complex between the marine diterpenoid sarcodictyin A and the protein tubulin is described here from MM-GBSA (molecular mechanics-generalized born surface area)... 相似文献
183.
<正>Water and related systems play a central role in science and technology. Although water has unusual and anomalous behaviors,if compared with normal liquids, it is of fundamental interest in many research fields going from chemical-physics to life sciences. The first and well known example of these anomalies is the density maximum, at 277 K, intuited by Galilei [1] in 1612and lately discovered in Florence [2]. 相似文献
184.
Synthesis and Biological Evaluation of RGD Peptidomimetic–Paclitaxel Conjugates Bearing Lysosomally Cleavable Linkers 下载免费PDF全文
Alberto Dal Corso Dr. Michele Caruso Dr. Laura Belvisi Dr. Daniela Arosio Prof. Dr. Umberto Piarulli Dr. Clara Albanese Dr. Fabio Gasparri Dr. Aurelio Marsiglio Dr. Francesco Sola Dr. Sonia Troiani Dr. Barbara Valsasina Dr. Luca Pignataro Dr. Daniele Donati Prof. Dr. Cesare Gennari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6921-6929
Two small‐molecule–drug conjugates (SMDCs, 6 and 7 ) featuring lysosomally cleavable linkers (namely the Val–Ala and Phe–Lys peptide sequences) were synthesized by conjugation of the αvβ3‐integrin ligand cyclo[DKP–RGD]‐CH2NH2 ( 2 ) to the anticancer drug paclitaxel (PTX). A third cyclo[DKP–RGD]–PTX conjugate with a nonpeptide “uncleavable” linker ( 8 ) was also synthesized to be tested as a negative control. These three SMDCs were able to inhibit biotinylated vitronectin binding to the purified αVβ3‐integrin receptor at nanomolar concentrations and showed good stability at pH 7.4 and pH 5.5. Cleavage of the two peptide linkers was observed in the presence of lysosomal enzymes, whereas conjugate 8 , which possesses a nonpeptide “uncleavable” linker, remained intact under these conditions. The antiproliferative activities of the conjugates were evaluated against two isogenic cell lines expressing the integrin receptor at different levels: the acute lymphoblastic leukemia cell line CCRF‐CEM (αVβ3?) and its subclone CCRF‐CEM αVβ3 (αVβ3+). Fairly effective integrin targeting was displayed by the cyclo[DKP–RGD]–Val–Ala–PTX conjugate ( 6 ), which was found to differentially inhibit proliferation in antigen‐positive CCRF‐CEM αVβ3 versus antigen‐negative isogenic CCRF‐CEM cells. The total lack of activity displayed by the “uncleavable” cyclo[DKP–RGD]–PTX conjugate ( 8 ) clearly demonstrates the importance of the peptide linker for achieving the selective release of the cytotoxic payload. 相似文献
185.
The paper presents an interphase cohesive zone model (CZM) incorporating stress multi-axiality devised to capture, by simplified micro-modeling, the influence of the in-plane strain and stress state in the mechanical response of the CZM. Moreover, the model is able to account for the Poisson-related effect in the interphase, which can play an important role in the modeling of heterogeneous masonry elements. From the constitutive point of view, the proposed formulation couples damage and friction by addressing a smooth transition from a quasi-brittle response to a residual frictional behavior described by a Coulomb law with unilateral contact. As in-plane stresses are accounted for, damage activation and evolution are governed by a Drucker–Prager law with linear softening. A predictor-corrector procedure based on a backward Euler scheme is detailed for integrating the nonlinear evolutive problem together with the related tangent operator which consistently linearizes the algorithmic strategy. This framework is embedded into a kinematically-enriched finite element interphase formulation incorporating stress multi-axiality. The modeling features of the resulting numerical tool are tested both at the local level, for the typical interphase point, and in meso-structural tests consisting of brick-mortar triplets, investigating the capability of the proposed model and numerical procedure to simulate the brick-mortar decohesion mechanism during confined slip tests. 相似文献
186.
187.
188.
Claudia Curcio Silvia Brugiapaglia Sara Bulfamante Laura Follia Paola Cappello Francesco Novelli 《Molecules (Basel, Switzerland)》2021,26(6)
Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal forms of human cancer, characterized by unrestrained progression, invasiveness and treatment resistance. To date, there are limited curative options, with surgical resection as the only effective strategy, hence the urgent need to discover novel therapies. A platform of onco-immunology targets is represented by molecules that play a role in the reprogrammed cellular metabolism as one hallmark of cancer. Due to the hypoxic tumor microenvironment (TME), PDA cells display an altered glucose metabolism—resulting in its increased uptake—and a higher glycolytic rate, which leads to lactate accumulation and them acting as fuel for cancer cells. The consequent acidification of the TME results in immunosuppression, which impairs the antitumor immunity. This review analyzes the genetic background and the emerging glycolytic enzymes that are involved in tumor progression, development and metastasis, and how this represents feasible therapeutic targets to counteract PDA. In particular, as the overexpressed or mutated glycolytic enzymes stimulate both humoral and cellular immune responses, we will discuss their possible exploitation as immunological targets in anti-PDA therapeutic strategies. 相似文献
189.
190.
Junxiong Wu Prof. Francesco Ciucci Prof. Jang-Kyo Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6296-6319
The rapid development of electrochemical energy storage systems requires new electrode materials with high performance. As a two-dimensional material, molybdenum disulfide (MoS2) has attracted increasing interest in energy storage applications due to its layered structure, tunable physical and chemical properties, and high capacity. In this review, the atomic structures and properties of different phases of MoS2 are first introduced. Then, typical synthetic methods for MoS2 and MoS2-based composites are presented. Furthermore, the recent progress in the design of diverse MoS2-based micro/nanostructures for rechargeable batteries, including lithium-ion, lithium-sulfur, sodium-ion, potassium-ion, and multivalent-ion batteries, is overviewed. Additionally, the roles of advanced in situ/operando techniques and theoretical calculations in elucidating fundamental insights into the structural and electrochemical processes taking place in these materials during battery operation are illustrated. Finally, a perspective is given on how the properties of MoS2-based electrode materials are further improved and how they can find widespread application in the next-generation electrochemical energy-storage systems. 相似文献