全文获取类型
收费全文 | 39981篇 |
免费 | 2678篇 |
国内免费 | 5272篇 |
专业分类
47931篇 |
出版年
2024年 | 113篇 |
2023年 | 717篇 |
2022年 | 1040篇 |
2021年 | 1438篇 |
2020年 | 1320篇 |
2019年 | 1592篇 |
2018年 | 1281篇 |
2017年 | 1162篇 |
2016年 | 1228篇 |
2015年 | 1495篇 |
2014年 | 2052篇 |
2013年 | 2664篇 |
2012年 | 1806篇 |
2011年 | 1950篇 |
2010年 | 1659篇 |
2009年 | 1986篇 |
2008年 | 2110篇 |
2007年 | 2317篇 |
2006年 | 2281篇 |
2005年 | 2109篇 |
2004年 | 1942篇 |
2003年 | 1790篇 |
2002年 | 1654篇 |
2001年 | 1325篇 |
2000年 | 1093篇 |
1999年 | 1031篇 |
1998年 | 880篇 |
1997年 | 783篇 |
1996年 | 740篇 |
1995年 | 716篇 |
1994年 | 683篇 |
1993年 | 474篇 |
1992年 | 431篇 |
1991年 | 347篇 |
1990年 | 302篇 |
1989年 | 217篇 |
1988年 | 229篇 |
1987年 | 198篇 |
1986年 | 156篇 |
1985年 | 159篇 |
1984年 | 129篇 |
1983年 | 68篇 |
1982年 | 76篇 |
1981年 | 40篇 |
1980年 | 40篇 |
1979年 | 39篇 |
1978年 | 23篇 |
1977年 | 9篇 |
1976年 | 19篇 |
1950年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Transfer of a marine DNA virus fromEctocarpus toFeldmannia (Ectocarpales,Phaeophyceae): aberrant symptoms and restitution of the host 总被引:1,自引:0,他引:1
Summary The marine brown algaEctocarpus siliculosus is invaded by a polyhedric virus, whose genome consists of circular, double-stranded DNA. In laboratory experiments this virus can infect a different host species,Feldmannia simplex. InfectedFeldmannia plants show severe somatic malformations. However, no functional virus particles are formed. SuchFeldmannia plants recover to resume a normal, symptom-free appearance. This result raises the possibility of intergeneric gene transfer in the natural habitat. 相似文献
74.
75.
本文报道在我国广西隆林壮族中发现一个罕見的HbQ复合α,β地中海贫血家系。先证者女,18岁,贫血面容,肝脾肿大。化学结构分析确证本Hb变异体为HbQ Thailand[α74(EF3)Asp→His]。血红蛋白组成以及α和β珠蛋白基因分析结果表明,先证者的珠蛋白基因型为-α~Q/-α~T复合β°/β°(IVSI-1G→T/Codon17A→T);先证者父的基因型为-‘α~Q/-复合β~O/β~A(IVSI-1G→T/β~A);先证母的基因型为-α~T/αα复合β~O/β~A(Codon17A→T/β~A)。 相似文献
76.
The rise of supramolecular chemistry offers new tools to design therapeutics and delivery platforms for biomedical applications. This review aims to highlight the recent developments that harness host-guest interactions and self-assembly to design novel supramolecular Pt complexes as anticancer agents and drug delivery systems. These complexes range from small host-guest structures to large metallosupramolecules and nanoparticles. These supramolecular complexes integrate the biological properties of Pt compounds and novel supramolecular structures, which inspires new designs of anticancer approaches that overcome problems in conventional Pt drugs. Based on the differences in Pt cores and supramolecular structures, this review focuses on five different types of supramolecular Pt complexes, and they include host-guest complexes of the FDA-approved Pt(II) drugs, supramolecular complexes of nonclassical Pt(II) metallodrugs, supramolecular complexes of fatty acid-like Pt(IV) prodrugs, self-assembled nanotherapeutics of Pt(IV) prodrugs, and self-assembled Pt-based metallosupramolecules. 相似文献
77.
Bruno Moises de Matos Marco Augusto Stimamiglio Alejandro Correa Anny Waloski Robert 《World journal of stem cells》2023,15(5):453-465
Extracellular vesicles (EVs) are nanometric particles that enclose cell-derived bioactive molecules in a lipid bilayer and serve as intercellular communication tools. Accordingly, in various biological contexts, EVs are reported to engage in immune modulation, senescence, and cell proliferation and differentiation. Therefore, EVs could be key elements for potential off-the-shelf cell-free therapy. Little has been studied regarding EVs derived from human pluripotent stem cells (hPSC-EVs), even though hPSCs offer good opportunities for induction of tissue regeneration and unlimited proliferative ability. In this review article, we provide an overview of studies using hPSC-EVs, focusing on identifying the conditions in which the cells are cultivated for the isolation of EVs, how they are characterized, and applications already demonstrated. The topics reported in this article highlight the incipient status of the studies in the field and the significance of hPSC-EVs’ prospective applications as PSC-derived cell-free therapy products. 相似文献
78.
79.
Sonodynamic therapy, a promising new approach to cancer treatment, is based on synergistic cell killing by combination of certain drugs (sonosensitizers) and ultrasound. Although the mechanism of sonodynamic action is not understood, the role of free radicals produced from sonosensitizers by ultrasound is implicated. In this work, we studied formation of free radicals during the decomposition of several water-soluble azo compounds by 50 kHz ultrasound in aqueous solutions. Using the spin trap 3, 5-dibromo-4-nitrosobenzene sulfonate (DBNBS) tertiary carbon-centered radicals from 2, 2'-azobis (N,N'-dimethyl-eneisobutyramidine) dihydrochloride (VA-044), 2-(carbamoylazo)-isobutyronitrile (V-30), and 2, 2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and CH3 radicals from 1, 1'-azobis (N,N'-dimethylformamide) (ADMF) were detected in argonsaturated solutions and the corresponding oxygen-centered radicals (alkoxyl and peroxyl) from VA-044, V-30, and AAPH were identified using the spin trap 5, 5'-dimethyl-l-pyrroline-N-oxide (DMPO) in aerated sonicated solutions. No free radicals from 4, 4'-dihydroxyazobenzene-3, 3'-dicarboxylic acid, disodium salt (DHAB) could be found in either system. While VA-044 and AAPH could also be readily decomposed by heat (42.5°C and 80°C), V-30 decomposition only occurred in the ultrasound-exposed solutions. The most likely mechanism of decomposition of azo compounds by ultrasound is their thermolysis in the heated shell of the liquid surrounding ca vita ting bubbles driven by ultrasound and/or by pyrolysis inside these bubbles. Experiments using scavengers of ·OH and ·H, which are produced by sonolysis in aqueous solutions, demonstrated that these radicals are not involved in the ultrasound-mediated radical production from the azo compounds. Due to the known cytotoxic potential of free radicals produced from azo compounds, the use of these compounds as ultrasound sensitizers appears to be a promising approach for sonodynamic cell killing. 相似文献
80.