全文获取类型
收费全文 | 778篇 |
免费 | 44篇 |
国内免费 | 2篇 |
专业分类
824篇 |
出版年
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 17篇 |
2015年 | 26篇 |
2014年 | 25篇 |
2013年 | 56篇 |
2012年 | 59篇 |
2011年 | 63篇 |
2010年 | 38篇 |
2009年 | 32篇 |
2008年 | 41篇 |
2007年 | 40篇 |
2006年 | 32篇 |
2005年 | 30篇 |
2004年 | 29篇 |
2003年 | 43篇 |
2002年 | 32篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1970年 | 3篇 |
1968年 | 4篇 |
1957年 | 3篇 |
1956年 | 3篇 |
排序方式: 共有824条查询结果,搜索用时 15 毫秒
1.
Edmond A. Goidl Christiane Samarut Ansbert Schneider-Gadicke Neal L. Hochwald G.Jeanette Thorbecke Gregory W. Siskind 《Cellular immunology》1984,85(1):25-33
Using hapten-reversible inhibition of plaque formation as an assay for auto-anti-idiotype antibody (anti-Id) and as a means for following idiotype (Id) expression, we have obtained evidence that following immunization with trinitrophenyl (TNP) conjugates (a) there are differences in Id expression in the anti-TNP antibody response to different TNP conjugates although there is some overlap; (b) different strains, although showing some differences in Id expression, tend to produce cross-reactive Ids, thus no obvious allotype linked inheritance of Id expression is observed in this heterogeneous immune response; (c) the auto-anti-Id produced following immunization with TNP-Brucella abortus or TNP-Ficoll tends to be of the IgG2a and IgG2b isotypes. 相似文献
2.
3.
4.
George T. Fantry Qiao-Xi Zheng Peter E. Darwin rew H. Rosenstein Stephen P. James 《Helicobacter》1996,1(2):98-106
Background Helicobacter pylori infection has been implicated strongly in the pathogenesis of gastritis, peptic ulcer disease, gastric adenocarcinoma, and gastric lymphoma, but the reasons for these widely different clinical outcomes are unknown. The aim of this study was to determine whether these differences could be due in part to mixed infection in the same individual, with bacteria having differences in pathogenic factors associated with ulcers.
Materials and Methods. The cagA gene of H. pylori was used to test for mixed infection because it is present in only some strains, and its presence has been associated with ulcers. Polymerase chain reaction (PCR) assays for the cagA gene were applied to H. pylori culture isolates and endoscopic gastric aspirates. Individual bacterial clones were tested for genetic similarity by random primer amplification and restriction endonuclease digestion of urease gene PCR products.
Results. The majority of H. pylori -positive patients had strongly cagA -positive culture isolates and endoscopic samples (62.5% and 69.6%, respectively). However, many of these patients had evidence of mixed infection with cagA negative and cagA positive strais in cultures isolates and endoscopic samples (25% and 17.4%, respectively). Mixed infection was found to be due to genetically unrelated strains in two patients in whom genetic analysis was performed.
Conclusion. Mixed infection with differences in substrain pathogenic factors might occur in H. pylori infection and might contribute to differences in clinical outcome. 相似文献
Materials and Methods. The cagA gene of H. pylori was used to test for mixed infection because it is present in only some strains, and its presence has been associated with ulcers. Polymerase chain reaction (PCR) assays for the cagA gene were applied to H. pylori culture isolates and endoscopic gastric aspirates. Individual bacterial clones were tested for genetic similarity by random primer amplification and restriction endonuclease digestion of urease gene PCR products.
Results. The majority of H. pylori -positive patients had strongly cagA -positive culture isolates and endoscopic samples (62.5% and 69.6%, respectively). However, many of these patients had evidence of mixed infection with cagA negative and cagA positive strais in cultures isolates and endoscopic samples (25% and 17.4%, respectively). Mixed infection was found to be due to genetically unrelated strains in two patients in whom genetic analysis was performed.
Conclusion. Mixed infection with differences in substrain pathogenic factors might occur in H. pylori infection and might contribute to differences in clinical outcome. 相似文献
5.
Darwin D. Smith Scott J. Norton 《Biochemical and biophysical research communications》1980,94(4):1458-1462
Sinefungin and A9145C, antifungal antibiotic analogs of S-adeno-sylmethionine isolated from , have been found to be very effective inhibitors of cyclopropane fatty acid synthase from . Both compounds exhibit linear competitive inhibition with a Ki for Sinefungin of 220 nM and a Ki for A9145C of 11 nM. 相似文献
6.
In Smittia and other chironomid embryos, both anterior and posterior egg halves can give rise to either anterior or posterior segments. Upon various types of experimental interference, eggs may develop one of four basic body patterns: normal embryos, double cephalons, double abdomens, or inverted embryos. From a previous model of anteroposterior determination, we derive four sets of predictions for the results of combined ultraviolet irradiation and centrifugation experiments. While most of the actual results are in agreement with the predictions, some are not. Most of the discrepancies are resolved in a modified version of the model. According to the new model, anterior and posterior egg halves contain both anterior and posterior cytoplasmic determinants. These are thought to be mutually repressive, and to control an overall determination for either anterior or posterior development. Centrifugation and ultraviolet irradiation appear to affect the relative strength of anterior determinants in one or both of the egg halves, thus modifying the probabilities for the four basic body patterns to develop. Different frequencies of these patterns, which have been obtained after similar experimental treatment of different chironomid species, can be ascribed to species-specific variation in the ultraviolet sensitivity of anterior and posterior determinants. 相似文献
7.
Nancy Auestad Rose A. Korsak Jack W. Morrow John Edmond 《Journal of neurochemistry》1991,56(4):1376-1386
The oxidation of the fatty acids octanoate and palmitate to CO2 and the ketone bodies acetoacetate and D-(-)-3-hydroxybutyrate was examined in astrocytes that were prepared from cortex of 2-day-old rat brain and grown in primary culture to confluence. Accumulation of acetoacetate (by mass) in the culture medium of astrocytes incubated with octanoate (0.3-0.5 mM) was 50-90 nmol C2 units h-1 mg of protein-1. A similar rate was obtained using radiolabeled tracer methodology with [1-14C]octanoate as labeled substrate. The results from the radiolabeled tracer studies using [1-14C]- and [7-14C]octanoate and [1-14C]-, [13-14C]-, and [15-14C]palmitate indicated that a substantial proportion of the omega-terminal four-carbon unit of these fatty acids bypassed the beta-ketothiolase step of the beta-oxidation pathway and the 3-hydroxy-3-methylglutaryl (HMG)-CoA cycle of the classic ketogenic pathway. The [14C]acetoacetate formed from the 1-14C-labeled fatty acids, obligated to pass through the acetyl-CoA pool, contained 50% of the label at carbon 3 and 50% at carbon 1. By contrast, the [14C]acetoacetate formed from (omega-1)-labeled fatty acids contained 90% of the label at carbon 3 and 10% at carbon 1, whereas that formed from the (omega-3)-labeled fatty acid contained 20% of the label at carbon 3 and 80% at carbon 1. These results indicate that acetoacetate is primarily formed either by the action of 3-oxo-acid-CoA transferase (EC 2.8.3.5) or acetoacetyl-CoA deacylase (EC 3.1.2.11) or both on acetoacetyl-CoA and not by the action of the mitochondrial HMG-CoA cycle involving HMG-CoA lyase (EC 4.1.3.4), which was readily detected, and HMG-CoA synthase (EC 4.1.3.5), which was barely measurable. 相似文献
8.
Edmond M. Linossi Jeffrey J. Babon Douglas J. Hilton Sandra E. Nicholson 《Cytokine & growth factor reviews》2013,24(3):241-248
The discovery of the Suppressor of Cytokine Signaling (SOCS) family of proteins has resulted in a significant body of research dedicated to dissecting their biological functions and the molecular mechanisms by which they achieve potent and specific inhibition of cytokine and growth factor signaling. The Australian contribution to this field has been substantial, with the initial discovery of SOCS1 by Hilton, Starr and colleagues (discovered concurrently by two other groups) and the following work, providing a new perspective on the regulation of JAK/STAT signaling. In this review, we reflect on the critical discoveries that have lead to our current understanding of how SOCS proteins function and discuss what we see as important questions for future research. 相似文献
9.
Marie-Paule?VassonEmail author Marie-Chantal?Farges Nicolas?Goncalves-Mendes Jérémie?Talvas Josep?Ribalta Brigitte?Winklhofer-Roob Edmond?Rock Adrien?Rossary 《Immunity & ageing : I & A》2013,10(1):38
Background
As the European population is getting older, there is growing need in scientific data on how to achieve healthy and successful aging. A decline in immune function with age is unanimously supported by many epidemiological and clinical observations, with a decrease in T-cell mediated function encompassing a large part of this alteration. In the EU-funded VITAGE project, the effects of aging on biomarkers of immune status are being studied in three European countries. According to strict inclusion/exclusion criteria, a cohort of 300 healthy male non-smoking 20–75 years old volunteers were enrolled in France (n?=?99), Spain (n?=?100) and Austria (n?=?101). In each country, the volunteers were classified as a function of age (one age group per decade). Biomarkers of immune status were determined including delayed-type hypersensitivity tests, measurement of lymphocyte surface markers, and serum determinations of interleukin-2, complement fractions and immunoglobulins.Results
There were moderate differences in the biomarkers of immune status of the VITAGE study volunteers among the three European centres. The percentage of Natural Killer (NK) cells was 156% and 142% higher in Spain as compared to France and Austria, respectively (p?<?0.0001), and this increase was observed at any age group above 30 years. Comparison between age-groups showed that in Spain, but not in France or Austria, older individuals had significantly a lower B lymphocyte distribution and conversely, a higher NK cell distribution. Moreover, the CD4/CD8 ratio was positively correlated with age in Austrian subjects (p?<?0.0001).Conclusion
Our results provide evidence of an increased NK cell distribution in the elderly, especially in the Spanish population. NK cell status may predict morbidity and mortality in the elderly, emphasizing the importance of innate as well as adaptive immunity in ensuring healthy longevity and cancer resistance, possibly in link with the Mediterranean diet.10.