全文获取类型
收费全文 | 1945篇 |
免费 | 161篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 30篇 |
2020年 | 20篇 |
2019年 | 28篇 |
2018年 | 45篇 |
2017年 | 31篇 |
2016年 | 53篇 |
2015年 | 80篇 |
2014年 | 83篇 |
2013年 | 135篇 |
2012年 | 146篇 |
2011年 | 140篇 |
2010年 | 104篇 |
2009年 | 94篇 |
2008年 | 144篇 |
2007年 | 128篇 |
2006年 | 120篇 |
2005年 | 113篇 |
2004年 | 117篇 |
2003年 | 98篇 |
2002年 | 82篇 |
2001年 | 12篇 |
2000年 | 18篇 |
1999年 | 23篇 |
1998年 | 25篇 |
1997年 | 19篇 |
1996年 | 10篇 |
1995年 | 13篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1973年 | 5篇 |
1969年 | 4篇 |
排序方式: 共有2106条查询结果,搜索用时 656 毫秒
991.
Pasticci MB Floridi P Schiaroli E Stagni GM De Socio GV Longari F Baldelli F 《The new microbiologica》2012,35(2):233-237
Here we report on two consecutive cases of tuberculosis in immunocompetent HIV-negative patients with lingual lesions. In both patients diagnosis was delayed. Disease progressed involving the lungs, lymph nodes and also the brain. Both patients are disease-free at 30 and 22 month follow-up respectively. Isolated Mycobacterium tuberculosis from these patients was multi-susceptible. Tuberculosis lesions of the oral cavity and brain are infrequently diagnosed in immunocompetent subjects from Western countries. Clinicians must take into greater consideration tuberculosis as a possible diagnosis when diagnosing chronic and/or recurrent lingual lesions even in the absence of pulmonary lesions. 相似文献
992.
An in vitro evaluation of the effect of probiotics and prebiotics on the metabolic profile of human microbiota 总被引:1,自引:0,他引:1
In the current study, batch culture fermentations on fecal samples of 3 healthy individuals were performed to assess the effect of the addition of prebiotics (FOS), probiotics (Bifidobacterium longum Bar33 and Lactobacillus helveticus Bar13) and synbiotics (B. longum Bar33 + L. helveticus Bar13 + FOS) on the fecal metabolic profiles. A total of 84 different metabolites belonging to the families of sulfur compounds, nitrogen compounds, aldehydes, ketones, esters, alcohols, phenols, organic acids, and hydrocarbons were detected by GC-MS/SPME analysis. The highest number of metabolites varied in concentration in the models with added FOS and synbiotics, where several metabolic signatures were found in common. The increase of butyrate represented the greatest variation registered after the addition of FOS alone. Following the B. longum Bar33 addition, 2-methyl butyrate underwent the most evident variation. In the batch fermentation with added L. helveticus Bar13, the decrease of pyridine and butandiene was observed together with the increase of 2-methyl-5-ethyl-pyrazine, 2-butanone and butyrate. The modification of the fecal metabolic profiles induced by the simultaneous addition of B. longum Bar33 and L. helveticus Bar13 was very similar to that observed after the supplementation with L. helveticus Bar13, regarding mainly the decrease of pyridine and the increase of butyrate. 相似文献
993.
M. TaccariF. Comitini C. CasucciM. Ciani 《International biodeterioration & biodegradation》2011,65(1):60-64
A laboratory procedure using a simple respirometric technique was evaluated to determine the microbial toxicity in soil of three toxicant compounds: two pesticides, chlorpyrifos and glyphosate; and diesel oil. The microbial toxicity was tested using the specific oxygen uptake rate (SOUR) method, evaluating the soil samples for both the reduction in maximum SOUR (SOURmax) and the cumulative oxygen demands after 20 h (OD20). Consumption rate curves were produced for the lowest concentrations assessed: diesel (2460 ppm), chlorpyrifos (62.5 ppm), and glyphosate (250 ppm) (limiting amounts considered as local soil contamination). In comparison with the control, these showed drastic reductions in SOURmax, demonstrating the high sensitivity of this SOUR method. The SOURmax provides a better indication of the microbial toxicity of these contaminants compared to the OD20 because of the different effects of these toxic compounds on microbial communities in the soil. Increasing concentrations of these toxic compounds resulted in different responses, evaluated as percentage inhibition by these different xenobiotic compounds. For these reasons, the microbial toxicity of xenobiotic compounds can be better recognized with SOURmax as compared to other respirometric methodologies. 相似文献
994.
A. Camperio Ciani 《Human Evolution》1989,4(1):9-32
A hypothesis is presented which may explain within a single framework both the large behavioural differences and the large
differences in head morphology between the great apes and humans. All these differences can be parsimoniously explained by
a shift of few regulatory genes controlling the onset of the division of late migrating neurons in the human cortex. This
simple shift resulted in the following effects: 1) the neurocranium responded to brain enlargement by increasing mineral deposition
on its external surface, increasing its overall size and mass. 2) This increase in the braincase was largely achieved by developmental
reabsoption of the face bones. 3) The relative shift in growth between these two skull components also induced a rearrangement
at the basicranium level. This brought about the facial orthognatism of modernHomo and, as a mechanical by-product, the descent of the larynx into the throat. Brain enlargement led to a large increase in
cognitive capacity, and as a developmental byproduct, produced a mechanical organ preadapted for speech, as well as bringing
about the reduction of canines and the origin of the chin. In this study, the phylogenetic basis, the selective pressures,
and the behavioural consequences of this process during hominization are examined. Cognitiveversus communicative aspects of human language are distinguished and discussed. Cognitive capacities were the first to be selected
due to the survival advantage of mapping huge territories during the expansion of the Plio-Pleistocene savanna ecotone. The
present hypothesis is then compared with current theories leading to the conclusion that it is a more parsimonious explanation.
It integrates data from a wide array of fields of human biology, pathology and clinical medicine, all assessed from evolutionary
and ecological perspectives. 相似文献
995.
Dina Manetti Lorenzo Di Cesare Mannelli Silvia Dei Luca Guandalini Elisabetta Martini Martina Banchelli Carla Ghelardini 《Bioorganic & medicinal chemistry letters》2009,19(8):2224-2229
This paper documents a serious problem met during the testing of Gi protein-activating properties of a new series of synthetic compounds by measuring the induced binding of [35S]GTPγS to different subtypes of Gi protein. The problem arose from the strong affinity between [35S]GTPγS and the tested compounds, that are characterized by several (2–4) positive charges and high lipophilicity. Apparently, such affinity yields insoluble, labelled complexes that, also in the absence of Gi protein, are retained on the filters and give rise to false positive results. 相似文献
996.
Calcareous nannofossil changes during the late Callovian–early Oxfordian cooling phase 总被引:2,自引:2,他引:0
Fabrizio Tremolada Elisabetta Erba Bas van de Schootbrugge Emanuela Mattioli 《Marine Micropaleontology》2006,59(3-4):197-209
Calcareous nannofossil quantitative and biostratigraphic analyses integrated with carbon and oxygen stable isotopes were carried out on the core ANDRA (Agence Nationale pour la gestion des Déchets Radio-Actifs—FRANCE) HTM 102 across the Callovian/Oxfordian boundary drilled at Cirfontaines-en-Ornois, Départment de Haute-Marne, eastern France. Calcareous nannofossil assemblages at the Callovian–Oxfordian transition are dominated by the genus Watznaueria. An increase in abundance of Biscutum spp. and A-group, which consists of Axopodorhabdus spp. (A. atavus, A. rahla, and A. cylindratus), Podorhabdus grassei, Octopodorhabdus decussatus, Hexapodorhabdus cuvillieri (family Axopodorhabdaceae), and Triscutum spp., correlates with a significant positive excursion in δ18O suggesting that these groups were probably adapted to cooler surface waters. A positive increase in δ13C values is coupled with high abundances of eutrophic taxa such as Zeughrabdotus erectus, Biscutum spp., and small-sized Watznaueria britannica, and a decrease in abundance of the big and oligotrophic taxa Schizosphaerella punctulata and Watznaueria manivitae. Climate cooling across the Callovian/Oxfordian boundary probably triggered a breakdown in stratification of surface waters leading to more intense nutrient recycling and higher primary productivity that favoured the shift in abundance of small-sized eutrophic taxa in the East Paris Basin. 相似文献
997.
Massimilano Scolz Per O. Widlund Silvano Piazza Debora Rosa Bublik Simone Reber Leticia Y. Peche Yari Ciani Nina Hubner Mayumi Isokane Martin Monte Jan Ellenberg Anthony A. Hyman Claudio Schneider Alexander W. Bird 《PloS one》2012,7(12)
The regulation of cell migration is a highly complex process that is often compromised when cancer cells become metastatic. The microtubule cytoskeleton is necessary for cell migration, but how microtubules and microtubule-associated proteins regulate multiple pathways promoting cell migration remains unclear. Microtubule plus-end binding proteins (+TIPs) are emerging as important players in many cellular functions, including cell migration. Here we identify a +TIP, GTSE1, that promotes cell migration. GTSE1 accumulates at growing microtubule plus ends through interaction with the EB1+TIP. The EB1-dependent +TIP activity of GTSE1 is required for cell migration, as well as for microtubule-dependent disassembly of focal adhesions. GTSE1 protein levels determine the migratory capacity of both nontransformed and breast cancer cell lines. In breast cancers, increased GTSE1 expression correlates with invasive potential, tumor stage, and time to distant metastasis, suggesting that misregulation of GTSE1 expression could be associated with increased invasive potential. 相似文献
998.
Marina Cinco Elena Banfi Elisabetta Ruaro Diana Crevatin Daniele Crotti 《FEMS microbiology letters》1984,21(3):347-351
Abstract 14 strains of Campylobacter isolated from humans and birds were tested for adhesion on intestine cell line. All the strains showed quick adhesion which was inhibited by l -fucose (6-deoxy- l -galactopyranose), among the sugars and lectins used in the adhesion inhibition assay. Inhibition was a function of l -fucose concentration and was not complete, suggesting that beside l -fucose other receptors—or nonspecific interactions—may cooperate in the cell binding by Campylobacter . 相似文献
999.
1000.
Giuseppe Minelli Franco Ciani Antonio Contestabile 《Histochemistry and cell biology》1971,28(2):160-169
Summary The occurrence and localization of Succinicodehydrogenase, Lacticodehydrogenase, Monoaminoxidase and Acetylcholinesterase have been studied in cultures in vitro of spinal cord, dorsal root ganglia, cerebellum and optic tectum of chicken embryos. Explantations have been made before the morphological and functional differentiation of the neurons of the centres considered took place. All the neurons differentiated in vitro show a high concentration of SDH and LDH, whereas the activity of these two enzymes results to be much lower in the other cultures' elements (glial cells, fibroblasts). Research-works on the AChE and MAO distribution and concentration within the neurons differentiated in vitro show that there differentiate in culture neurons which have morphological and cytochemical characters similar to those of the corresponding neurons in vivo. An important exception is the AChE occurrence in the Purkinje neurons differentiated in vitro; the possible reasons for this behaviour are examined in the text. The data mentioned in the paper allow the conclusion that the various types of neuroblasts explanted in vitro are not only able to reach the morphological differentiation, but also to acquire specific biochemical characters, directly related to the neuron functionality. 相似文献