全文获取类型
收费全文 | 5526篇 |
免费 | 339篇 |
出版年
2023年 | 13篇 |
2022年 | 38篇 |
2021年 | 107篇 |
2020年 | 70篇 |
2019年 | 81篇 |
2018年 | 122篇 |
2017年 | 106篇 |
2016年 | 169篇 |
2015年 | 261篇 |
2014年 | 267篇 |
2013年 | 429篇 |
2012年 | 489篇 |
2011年 | 423篇 |
2010年 | 244篇 |
2009年 | 252篇 |
2008年 | 312篇 |
2007年 | 321篇 |
2006年 | 277篇 |
2005年 | 272篇 |
2004年 | 271篇 |
2003年 | 264篇 |
2002年 | 227篇 |
2001年 | 46篇 |
2000年 | 41篇 |
1999年 | 49篇 |
1998年 | 55篇 |
1997年 | 36篇 |
1996年 | 49篇 |
1995年 | 33篇 |
1994年 | 51篇 |
1993年 | 21篇 |
1992年 | 38篇 |
1991年 | 32篇 |
1990年 | 26篇 |
1989年 | 24篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 34篇 |
1983年 | 19篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1975年 | 16篇 |
1973年 | 15篇 |
排序方式: 共有5865条查询结果,搜索用时 15 毫秒
131.
Beatris Mastelic Nathalie Garçon Giuseppe Del Giudice Hana Golding Marion Gruber Pieter Neels Bernard Fritzell 《Biologicals》2013,41(6):458-468
Vaccination represents one of the greatest public health triumphs; in part due to the effect of adjuvants that have been included in vaccine preparations to boost the immune responses through different mechanisms. Although a variety of novel adjuvants have been under development, only a limited number have been approved by regulatory authorities for human vaccines. This report reflects the conclusions of a group of scientists from academia, regulatory agencies and industry who attended a conference on the current state of the art in the adjuvant field. Held at the U.S. Pharmacopeial Convention (USP) in Rockville, Maryland, USA, from 18 to 19 April 2013 and organized by the International Association for Biologicals (IABS), the conference focused particularly on the future development of effective adjuvants and adjuvanted vaccines and on overcoming major hurdles, such as safety and immunogenicity assessment, as well as regulatory scrutiny. More information on the conference output can be found on the IABS website, http://www.iabs.org/. 相似文献
132.
Massimiliano Ditroilo Giuseppe De Vito Eamonn Delahunt 《Journal of electromyography and kinesiology》2013,23(5):1111-1118
The Nordic Hamstring Exercise (NHE) has been introduced as a training tool to improve the efficiency of eccentric hamstring muscle contraction. The aim of this study was to perform a biomechanical analysis of the NHE. Eighteen participants (20.4 ± 1.9 years) performed two sets of five repetitions each of the NHE and maximal eccentric voluntary contraction (MEVC) of the knee flexors on an isokinetic dynamometer whilst knee angular displacement and electrical activity (EMG) of biceps femoris were measured. EMG was on average higher during the NHE (134.3% of the MEVC). During the forward fall of the NHE, the angle at which a sharp increase in downward velocity occurred varied between 47.9 and 80.5 deg, while the peak knee angular velocity (pVelocity) varied between 47.7 and 132.8 deg s?1. A significant negative correlation was found between pVelocity and peak EMG (r = ?0.62, p < 0.01) and EMG at 45 deg (r = ?0.75, p < 0.01) expressed as a percentage of peak MEVC EMG. Some of the variables analyzed exhibited good to excellent levels of intra- and inter-session reliability. This type of analysis could be used to indirectly monitor the level of eccentric strength of the hamstring muscles while performing the NHE and potentially any training- or injury-related changes. 相似文献
133.
Giuliana Catara Immacolata Fiume Filippo Iuliano Giovanna Maria Giuseppe Ruggiero 《Biocatalysis and Biotransformation》2013,31(5):358-370
A new serine-carboxyl proteinase, called kumamolisin-ac, was purified from the thermoacidophilic bacterium Alicyclobacillus acidocaldarius. The enzyme is a monomeric protein of 45?kDa, active over a wide temperature range (5.0–70°C) and extremely acidic pHs (1.0–4.0), showing maximal proteolytic activity at pH?2.0 and 60°C. Interestingly, kumamolisin-ac displayed a significant proteolytic activity even at 5°C, thus suggesting a sort of cold-adaptation for this enzyme. The protease was remarkably stable at high temperatures (t1/2 at 80°C, 10?h, pH?2.0) and over a broad range of pH (2.0–7.0). Substrate analysis indicated that kumamolisin-ac was active on a variety of macromolecular substrates, such as haemoglobin, hide powder azure, and azocoll. In particular, a high specific activity was detected towards collagen. The corresponding gene was cloned, expressed and the recombinant protease, was found to be homologous to proteases of the ‘S53’ family. From the high identity with kumamolisin and kumamolisin-As, known as collagenolytic proteases, kumamolisin-ac can be considered as the third collagenolytic affiliate within the ‘S53’ family. Cleavage specificity investigation of kumamolisin-ac revealed a unique primary cleavage site in bovine insulin B-chain, whereas a broad specificity was detected using bovine α-globin as substrate. Thus, kumamolisin-ac could represent an attractive candidate for industrial-scale biopeptide production under thermoacidophilic conditions. 相似文献
134.
Angela Maria Amorini Giuseppe Lazzarino Fabio Galvano Giovanna Fazzina Barbara Tavazzi Giacomo Galvano 《Free radical research》2013,47(4):453-460
The cyanidin-3- O - g -glucopyranoside (C-3-G) antioxidant capacity towards reactive oxygen species (ROS)-mediated damages was assessed in tissue and cells submitted to increased oxidative stress. In the isolated ischemic and reperfused rat heart, 10 or 30 w M C-3-G protected from both lipid peroxidation (66.7 and 94% inhibition of malondialdehyde (MDA) generation in 10 and 30 w M C-3-G-reperfused hearts, respectively, in comparison with control reperfused hearts) and energy metabolism impairment (higher ATP concentration in 10 and 30 w M C-3-G-reperfused hearts than in control reperfused hearts). These effects were associated to C-3-G permeation within myocardial cells, as indicated by results obtained in the isolated rat heart perfused for 30 min in the recirculating Langendorff mode under normoxia with 10 and 30 w M C-3-G. Protective effects were exerted, in a dose-dependent manner, by C-3-G also in 2 mM hydrogen peroxide-treated human erythrocytes. With respect to MDA formation, an apparent IC 50 of 5.12 w M was calculated for C-3-G (the polyphenol resveratrol used for comparison showed an apparent IC 50 of 38.43 w M). The general indications are that C-3-G (largely diffused in dietary plants and fruits, such as pigmented oranges very common in the Mediterranean diet) represents a powerful natural antioxidant with beneficial effects in case of increased oxidative stress, and at pharmacological concentrations it is able to decrease tissue damages occurring in myocardial ischemia and reperfusion. 相似文献
135.
Giuseppe Zodda 《Plant biosystems》2013,147(3-4):390-398
136.
Abstract A strong K+-dependent, fusicoccin-sensitive increase in acidic extrusion paralleled by a corresponding increase in net K+ uptake and hyperpolarization of transmembrane electrical potential was observed in the root segments of wheat seedlings cultured in diluite CaSO4+0.27 mM Methyl-acethydroxamoilacetate. Moreover, K+-induced depolarization was also increased up to three times. 相似文献
137.
138.
Donato Chiatante Gabriella S. Scippa Lucia Maiuro Elisabetta Onelli Giuseppe Patrignani 《Plant biosystems》2013,147(1):35-47
ABSTRACT To understand the mechanisms which enable the nucleus to function under low water potential, the morphology and biochemistry of potato cell nuclei were studied. Conformational modifications were observed in the chromatin of nuclei of cells growing under low water potential. These modifications include a higher number of heterochromatic centres, enlargement of the nuclear diameter, and a different accessibility of DNA to the action of restriction enzymes. Biochemical analyses showed that these chromatin modifications may coincide with quantitative and qualitative variations of several nuclear proteins, some of which may belong to the dehydrin family. We especially focussed our attention on a 45-kDa protein that is heat-stable and is recognised by an antibody raised against the conserved domain of dehydrins. The survival of potato cells in an environment where water availability is low may depend on several simultaneous events regarding the nucleus. The accumulation in the nucleus of specific proteins such as dehydrins could be required to stabilise the chromatin by means of their molecule-salvation action. Further studies are in progress to check whether or not variations in chromatin organisation may be one of the numerous traits that a cell must acquire to become water-stress resistant. 相似文献
139.
Dott. Flavio Giuseppe Elisei 《Plant biosystems》2013,147(3):674-692
Abstract A survey of all the 154 scientific publications of Emilio Battaglia (1917–2011) is presented, grouped in three main research interests – plant embryology, cytogenetics in plants and cytological terminology – plus other less relevant contributions. Battaglia's past and present role in these disciplines is briefly discussed, in the light of current research on these topics, partly reviewed also in other contributions of the present Plant Biosystems issue. 相似文献
140.
Giuseppe Giaccone Blasco Scammacca Francesco Cinelli Gianfranco Sartoni Giovanni Furnari 《Plant biosystems》2013,147(4):211-229
Abstract Preliminary studies on the marine phythobenthic communities in the Straits of Sicily and adjacent islands. — The results of algological researches carried out by the Gruppo di Algologia of the S.B.I. in the Straits of Sicily and adjacent islands are reported. 288 species have been collected, 275 of which have been identified: 160 were Rhodophyta, 62 Phaeophyta, 32 Chlorophyta, 16 Cyanophyta and 2 Angiospermae. The vegetational research leads to the following conclusions: 1 - the harbour areas (Pantelleria, Malta: loc. 1 and 11) show a nitrophile vegetation, particulary near La Valletta where an almost pure population of Pterocladia pinnata is found; 2 - there are important biogeographical differences between Pelagie islands (Lampedusa, Linosa) and Pantelleria. In fact the former ones have an algal flora composed mostly of eastern mediterranean species, whilst the latter shows strong affinities with the north-african basin, as is demonstrated by the rich well developed belt of Cystoseira sedoides; 3 - several species of atlantic origin, such as Callophyllis laciniata, Peyssonnelia coriacea, P. inamoena and Castagnea chordariaeformis, have been found on the banks (loc. 3, 6, 7). 相似文献