全文获取类型
收费全文 | 587篇 |
免费 | 47篇 |
专业分类
634篇 |
出版年
2021年 | 6篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 18篇 |
2014年 | 16篇 |
2013年 | 20篇 |
2012年 | 37篇 |
2011年 | 23篇 |
2010年 | 26篇 |
2009年 | 15篇 |
2008年 | 29篇 |
2007年 | 32篇 |
2006年 | 31篇 |
2005年 | 19篇 |
2004年 | 28篇 |
2003年 | 24篇 |
2002年 | 26篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1986年 | 5篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1977年 | 8篇 |
1965年 | 5篇 |
1939年 | 3篇 |
1937年 | 4篇 |
1936年 | 4篇 |
1935年 | 8篇 |
1934年 | 3篇 |
1933年 | 3篇 |
1932年 | 5篇 |
1931年 | 6篇 |
1930年 | 7篇 |
1929年 | 11篇 |
1927年 | 3篇 |
1925年 | 3篇 |
1897年 | 3篇 |
1896年 | 3篇 |
1892年 | 3篇 |
排序方式: 共有634条查询结果,搜索用时 0 毫秒
501.
Curt Herbst 《Development genes and evolution》1901,13(3):436-447
Ohne ZusammenfassungDie in dieser Mittheilung niedergelegten Thatsachen wurden zu einem Vortrage verwendet, der am 13. August 1901 in der Sektion für Experimental-Zoologie des fünften internationalen Zoologenkongresses zu Berlin gehalten wurde. 相似文献
502.
Curt Floericke 《Journal of Ornithology》1897,45(4):480-498
Ohne Zusammenfassung 相似文献
503.
Curt Teichert 《Pal?ontologische Zeitschrift》1986,60(3-4):227-243
The evolutionary history of the ectocochlian cephalopods is punctuated by a number of severe crises during each of which this class came very close to extinction. The crisis events follow each other at intervals of from seven to almost 300 million years and, with one exception, were not synchronous for Nautiloidea and Ammonoidea. Only at the end of the Triassic period did both groups simultaneously face the danger of extinction. Generally, the survivors of crisis situations have simple shell forms and are strikingly similar to each other. To trace the details of cephalopod evolution, the family on the taxonomic level and the stratigraphic stage on the chronological level do not provide scales fine enough to reconstruct the true course of this process. The causes of crises and “mass extinctions” are not yet understood. Most authors have approached this problem in a simplistic manner, searching for a single cause for any, or all, events of this kind. It seems that we do not even have begun to understand what the problems are. 相似文献
504.
Stefan Jnsson Arne Schn Roland Isaksson Curt Pettersson Gran Pettersson 《Chirality》1992,4(8):505-508
505.
Janet Jansson Ben Willing Marianna Lucio Ages Fekete Johan Dicksved Jonas Halfvarson Curt Tysk Philippe Schmitt-Kopplin 《PloS one》2009,4(7)
The causes and etiology of Crohn''s disease (CD) are currently unknown although both host genetics and environmental factors play a role. Here we used non-targeted metabolic profiling to determine the contribution of metabolites produced by the gut microbiota towards disease status of the host. Ion Cyclotron Resonance Fourier Transform Mass Spectrometry (ICR-FT/MS) was used to discern the masses of thousands of metabolites in fecal samples collected from 17 identical twin pairs, including healthy individuals and those with CD. Pathways with differentiating metabolites included those involved in the metabolism and or synthesis of amino acids, fatty acids, bile acids and arachidonic acid. Several metabolites were positively or negatively correlated to the disease phenotype and to specific microbes previously characterized in the same samples. Our data reveal novel differentiating metabolites for CD that may provide diagnostic biomarkers and/or monitoring tools as well as insight into potential targets for disease therapy and prevention. 相似文献
506.
Background
Two treatments for smoking cessation—varenicline and bupropion—carry Boxed Warnings from the U.S. Food and Drug Administration (FDA) about suicidal/self-injurious behavior and depression. However, some epidemiological studies report an increased risk in smoking or smoking cessation independent of treatment, and differences between drugs are unknown.Methodology
From the FDA''s Adverse Event Reporting System (AERS) database from 1998 through September 2010 we selected domestic, serious case reports for varenicline (n = 9,575), bupropion for smoking cessation (n = 1,751), and nicotine replacement products (n = 1,917). A composite endpoint of suicidal/self-injurious behavior or depression was defined as a case with one or more Preferred Terms in Standardized MedDRA Query (SMQ) for those adverse effects. The main outcome measure was the ratio of reported suicide/self-injury or depression cases for each drug compared to all other serious events for that drug.Results
Overall we identified 3,249 reported cases of suicidal/self-injurious behavior or depression, 2,925 (90%) for varenicline, 229 (7%) for bupropion, and 95 (3%) for nicotine replacement. Compared to nicotine replacement, the disproportionality results (OR (95% CI)) were varenicline 8.4 (6.8–10.4), and bupropion 2.9 (2.3–3.7). The disproportionality persisted after excluding reports indicating concomitant therapy with any of 58 drugs with suicidal behavior warnings or precautions in the prescribing information. An additional antibiotic comparison group showed that adverse event reports of suicidal/self-injurious behavior or depression were otherwise rare in a healthy population receiving short-term drug treatment.Conclusions
Varenicline shows a substantial, statistically significant increased risk of reported depression and suicidal/self-injurious behavior. Bupropion for smoking cessation had smaller increased risks. The findings for varenicline, combined with other problems with its safety profile, render it unsuitable for first-line use in smoking cessation. 相似文献507.
Meixia Gao Anju Singh Kristin Macri Curt Reynolds Vandana Singhal Shyam Biswal Ernst W Spannhake 《Respiratory research》2011,12(1):1-15
Background
Proteomic studies of respiratory disorders have the potential to identify protein biomarkers for diagnosis and disease monitoring. Utilisation of sensitive quantitative proteomic methods creates opportunities to determine individual patient proteomes. The aim of the current study was to determine if quantitative proteomics of bronchial biopsies from asthmatics can distinguish relevant biological functions and whether inhaled glucocorticoid treatment affects these functions.Methods
Endobronchial biopsies were taken from untreated asthmatic patients (n = 12) and healthy controls (n = 3). Asthmatic patients were randomised to double blind treatment with either placebo or budesonide (800 μg daily for 3 months) and new biopsies were obtained. Proteins extracted from the biopsies were digested and analysed using isobaric tags for relative and absolute quantitation combined with a nanoLC-LTQ Orbitrap mass spectrometer. Spectra obtained were used to identify and quantify proteins. Pathways analysis was performed using Ingenuity Pathway Analysis to identify significant biological pathways in asthma and determine how the expression of these pathways was changed by treatment.Results
More than 1800 proteins were identified and quantified in the bronchial biopsies of subjects. The pathway analysis revealed acute phase response signalling, cell-to-cell signalling and tissue development associations with proteins expressed in asthmatics compared to controls. The functions and pathways associated with placebo and budesonide treatment showed distinct differences, including the decreased association with acute phase proteins as a result of budesonide treatment compared to placebo.Conclusions
Proteomic analysis of bronchial biopsy material can be used to identify and quantify proteins using highly sensitive technologies, without the need for pooling of samples from several patients. Distinct pathophysiological features of asthma can be identified using this approach and the expression of these features is changed by inhaled glucocorticoid treatment. Quantitative proteomics may be applied to identify mechanisms of disease that may assist in the accurate and timely diagnosis of asthma.Trial registration
ClinicalTrials.gov registration NCT01378039 相似文献508.
Pan C Fischer CR Hyatt D Bowen BP Hettich RL Banfield JF 《Molecular & cellular proteomics : MCP》2011,10(4):M110.006049
Stable isotope probing (SIP) has been used to track nutrient flows in microbial communities, but existing protein-based SIP methods capable of quantifying the degree of label incorporation into peptides and proteins have been demonstrated only by targeting usually less than 100 proteins per sample. Our method automatically (i) identifies the sequence of and (ii) quantifies the degree of heavy atom enrichment for thousands of proteins from microbial community proteome samples. These features make our method suitable for comparing isotopic differences between closely related protein sequences, and for detecting labeling patterns in low-abundance proteins or proteins derived from rare community members. The proteomic SIP method was validated using proteome samples of known stable isotope incorporation levels at 0.4%, ~50%, and ~98%. The method was then used to monitor incorporation of (15)N into established and regrowing microbial biofilms. The results indicate organism-specific migration patterns from established communities into regrowing communities and provide insights into metabolism during biofilm formation. The proteomic SIP method can be extended to many systems to track fluxes of (13)C or (15)N in microbial communities. 相似文献
509.
Frank S. Adams Francisco G. La Rosa Sanjay Kumar Judith Edwards-Prasad Susan Kentroti Antonia Vernadakis Curt R. Freed Kedar N. Prasad 《Neurochemical research》1996,21(5):619-627
Immortalized rat mesencephalic cells (1RB3AN27) produced dopamine (DA) at a level that was higher than produced by undifferentiated or differentiated murine neuroblastoma
cells (NBP2) in culture. Treatment of 1RB3AN27 and NBP2 cells with a cAMP stimulating agent increased tyrosine hydroxylase (TH) activity and the intensity of immunostaining for
the DA transporter protein (DAT). 1RB3AN27 cells were labelled with primary antibodies to neuron specific enolase (NSE) and nestin and exhibited very little or no labeling
with anti-glial fibrillary acidic protein (GFAP). 1RB3AN27 cells exhibited β- and α-adrenoreceptors, and prostaglandin E1 receptors, all of which were linked to adenylate cyclase (AC). Dopamine receptor (D1) and cholinergic muscarinic receptors linked to AC were not detectable. The levels of PKCα and PKCβ isoforms were higher
than those of PKCγ and PKCδ in 1RB3AN27 cells. The 1RB3AN27 cells were more effective in reducing the rate of methamphetamine-induced turning in rats with unilateral 6-OHDA lesion of
the nigrostriatal system than differentiated NBP2 cells. The grafted 1RB3AN27 were viable as determined by DiI labelling, but they did not divide and did not produce T-antigen protein; however, when
these grafted cells were cultured in vitro, they resumed production of T-antigen and proliferated after the primary glia cells
and neurons of host brain died due to maturation and subsequent degeneration. Examination of H&E stained sections of the grafted
sites revealed no evidence of infiltration of inflammatory cells in the grafted area suggesting that these cells were not
immunogenic. They also did not form tumors. 相似文献
510.
Shah C McAtee L Breitenbucher JG Rudolph D Li X Lovenberg TW Mazur C Wilson SJ Carruthers NI 《Bioorganic & medicinal chemistry letters》2002,12(22):3309-3312
High throughput screening, using the recombinant human H(3) receptor, was used to identify novel histamine H(3) receptor antagonists. Evaluation of the lead compounds ultimately afforded potent, selective, orally bioavailable compounds (e.g., 38) with favorable blood-brain barrier penetration. 相似文献