全文获取类型
收费全文 | 11398篇 |
免费 | 572篇 |
国内免费 | 52篇 |
专业分类
耳鼻咽喉 | 88篇 |
儿科学 | 207篇 |
妇产科学 | 190篇 |
基础医学 | 1871篇 |
口腔科学 | 228篇 |
临床医学 | 1031篇 |
内科学 | 2250篇 |
皮肤病学 | 237篇 |
神经病学 | 1356篇 |
特种医学 | 569篇 |
外科学 | 1918篇 |
综合类 | 50篇 |
一般理论 | 2篇 |
预防医学 | 354篇 |
眼科学 | 211篇 |
药学 | 732篇 |
中国医学 | 25篇 |
肿瘤学 | 703篇 |
出版年
2023年 | 71篇 |
2022年 | 97篇 |
2021年 | 223篇 |
2020年 | 131篇 |
2019年 | 183篇 |
2018年 | 206篇 |
2017年 | 188篇 |
2016年 | 233篇 |
2015年 | 289篇 |
2014年 | 366篇 |
2013年 | 470篇 |
2012年 | 718篇 |
2011年 | 743篇 |
2010年 | 441篇 |
2009年 | 438篇 |
2008年 | 688篇 |
2007年 | 716篇 |
2006年 | 669篇 |
2005年 | 668篇 |
2004年 | 623篇 |
2003年 | 595篇 |
2002年 | 568篇 |
2001年 | 97篇 |
2000年 | 77篇 |
1999年 | 80篇 |
1998年 | 125篇 |
1997年 | 105篇 |
1996年 | 76篇 |
1995年 | 77篇 |
1994年 | 75篇 |
1993年 | 62篇 |
1992年 | 44篇 |
1991年 | 32篇 |
1989年 | 33篇 |
1988年 | 29篇 |
1939年 | 28篇 |
1937年 | 33篇 |
1936年 | 34篇 |
1935年 | 34篇 |
1933年 | 47篇 |
1932年 | 75篇 |
1931年 | 35篇 |
1930年 | 45篇 |
1929年 | 35篇 |
1928年 | 61篇 |
1927年 | 57篇 |
1926年 | 38篇 |
1925年 | 33篇 |
1924年 | 43篇 |
1922年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
BACKGROUND: Several poxviruses can infect humans and cause diseases of varying severity. Besides the eradicated Variola virus that induced high mortality rates, numerous further human pathogenic orthopoxviruses are potentially fatal but generally cause less severe infections. While infection-related viremia was described for Variola virus and seems to be rare for Monkeypox virus, it is still debated for Vaccinia virus. So far, viremia in Cowpox virus-infected humans has not been reported. OBJECTIVES: To estimate the potential risk of Cowpox virus to disseminate and develop severe infections, two Cowpox virus patients were examined for viremia. STUDY DESIGN: Whole blood, serum and fluid from virus-induced lesions were analyzed by serology or quantitative real-time PCR. RESULTS: Real-time PCR and sequence analysis of the hemagglutinin gene confirmed Cowpox virus in the lesions of both patients. Serology performed on serum obtained at the same time as the lesion specimens demonstrated orthopoxvirus-specific IgG and IgM antibodies, indicating a recent orthopoxvirus infection. In addition, Cowpox virus DNA was detectable in whole blood, but not in serum, as late as week 4 post-infection. CONCLUSIONS: In contrast to observations following vaccination with Vaccinia virus, DNAemia in patients with localized symptoms of a Cowpox virus infection does not seem to be a rare event. However, its relevance for Cowpox virus pathogenicity has to be elucidated. 相似文献
42.
Taylor GP Bodéus M Courtois F Pauli G Del Mistro A Machuca A Padua E Andersson S Goubau P Chieco-Bianchi L Soriano V Coste J Ades AE Weber JN 《Journal of acquired immune deficiency syndromes (1999)》2005,38(1):104-109
BACKGROUND: Up to 20 million persons are infected with the human retroviruses human T-lymphotropic virus (HTLV)-I and HTLV-II globally. Most data on the seroprevalence of HTLV-I and HTLV-II in Europe are from studies of low-risk blood donors or high-risk injection drug users (IDUs). Little is known about the general population. METHODS: A prospective anonymous study of HTLV-I and HTLV-II seroprevalence among 234,078 pregnant women in Belgium, France, Germany, Italy, Portugal, Spain, and the United Kingdom was conducted. Maternal antibody status was determined by standard methods using sera obtained for routine antenatal infection screens or eluted from infant heel prick dried blood spots obtained for routine neonatal metabolic screens. RESULTS: Anti-HTLV-I/II antibodies were detected and confirmed in 96 pregnant women (4.4 per 10,000, 95% confidence interval [CI]: 3.5-5.2). Of these, 73 were anti-HTLV-I, 17 were anti-HTLV-II, and 6 were specifically anti-HTLV but untyped. The seroprevalence ranged from 0.7 per 10,000 in Germany to 11.5 per 10,000 in France. CONCLUSIONS: Pregnant women better reflect the general population than blood donors or IDUs. The seroprevalence of HTLV-I and HTLV-II in Western Europe is 6-fold higher among pregnant women (4.4 per 10,000) than among blood donors (0.07 per 10,000). These data provide a robust baseline against which changes in HTLV-I and HTLV-II seroprevalence in Europe can be measured. 相似文献
43.
The purpose of the present study was a direct comparison between simultaneous recordings of skin conductance and skin resistance. Sixty male students received a series of 30 white noise stimuli, while measures were taken continuously from four sites on the palmar surfaces of the fingers. Evaluations were made for response amplitudes, recovery, and for an approximate area measure. Magnitude of reactions and reliabilities were compared using ANOVA procedures. Behavioral concordances were estimated as correlations with the subjects' ratings of stimulus intensities. Conductance and resistance measures do not differ in amplitude, in area, or in strength of their reliabilities and behavioral concordances. No differences in any respect are found between sites. Skin conductance yields significantly (p < .01) shorter recovery times than skin resistance, which is discussed in terms of membrane permeability change. 相似文献
44.
Wahrmann M Exner M Haidbauer B Schillinger M Regele H Körmöczi G Böhmig GA 《Human immunology》2005,66(5):526-534
On waiting lists, transplant candidates are routinely screened for potentially harmful complement-fixing alloantibodies using complement-dependent cytotoxicity (CDC) panel-reactive antibody (PRA) testing. We have recently developed a novel cell-independent assay for assessment of complement-activating panel reactivity ([C4d]FlowPRA), which is based on selective flow-cytometric detection of alloantibody-triggered C4 complement split product deposition to human leukocyte antigen (HLA)-coated FlowPRA beads. Serum specimens selected from 120 transplant candidates were evaluated by [C4d]FlowPRA (HLA class I vs II) in comparison with FlowPRA IgG alloantibody screening (HLA class I vs II), a method detecting both complement- and noncomplement-activating alloantibodies, and with CDC-PRA on separated T (T-CDC) or B cells (B-CDC, evaluation on platelet-absorbed sera). For each assay, >/=10% PRA reactivity was considered positive. Comparing complement-dependent PRA assays with standard FlowPRA, the specificity calculated for [C4d]FlowPRA (HLA class I: 92%; class II: 100%) was found to be superior to that of CDC testing (T-CDC-PRA: 79%; B-CDC-PRA: 86%). Because noncomplement-activating alloreactivities were not detected for both techniques, low sensitivities were calculated ([C4d]FlowPRA HLA class I: 61%; class II: 31%; T-CDC-PRA: 70%; B-CDC-PRA: 55%). Compared with CDC-PRA, [C4d]FlowPRA gave a high specificity (HLA class I compared with T-CDC: 89%, HLA class II compared with B-CDC: 95%) but, at least in part because of false-positive CDC results, a modest sensitivity (66% and 38%, respectively). For both HLA classes, we found a highly significant association between absolute [C4d]FlowPRA and CDC-PRA levels (p < 0.0001). Our results suggest that detection of C4 split product deposition to FlowPRA beads may represent an attractive HLA-specific and time-effective alternative to CDC-PRA screening. 相似文献
45.
Klaus Langes Hartmut Frenzel Rüdiger J. Seitz Georg Kluitmann 《Virchows Archiv : an international journal of pathology》1985,407(1):97-105
Summary Clinical and postmortem findings in a female infant, suffering from Leigh's disease and cardiomegaly are described. The cardiac enlargement was due to symmetrical thickening of both ventricular walls and the septum. On light microscopy a widespread fibre disarray with a slight predilection for the ventricular septum was observed. Ultrastructural changes included an extreme reduction in the number of myofibrils and an excess of mitochondria. Abnormalities of the mitochondrial structure with tubular and myelinic transformation of the cristae suggested that a mitochondriopathy is responsible for the cardiomegaly in Leigh's disease.Dedicated to Prof. Dr. Waldemar Hort on the occasion to his 60th birthday 相似文献
46.
Serotonin transporter binding in Tourette Syndrome 总被引:5,自引:0,他引:5
Müller-Vahl KR Meyer GJ Knapp WH Emrich HM Gielow P Brücke T Berding G 《Neuroscience letters》2005,385(2):120-125
Recent studies provided evidence for an involvement of the dopaminergic system in the pathophysiology of Tourette Syndrome (TS). However, little is known about possible impairment of other neurotransmitter systems. In obsessive-compulsive disorder (OCD), a common comorbidity in TS, it is suggested that the serotonergic system plays a major role in the pathogenesis. We, therefore, used [I-123]2[beta]-carbomethoxy-3[beta]-(4-iodophenyl)tropane ([123I]beta-CIT) and single photon emission computed tomography (SPECT) to investigate serotonin transporter (SERT) binding capacity in 12 patients with TS with various degrees of associated obsessive compulsive behaviour (OCB) and 16 age-matched healthy controls. Binding ratios in TS patients not receiving serotonin reuptake inhibitors (SSRI) (n=8) were significantly reduced compared to age-adjusted ratios from normal controls (2.8 versus 3.2, p=0.003). Treatment with SSRI resulted in a significant reduction of SERT availability. Performing linear regression analysis for this small group, SSRI-free patients indicated trends for a negative correlation between [123I]beta-CIT binding on SERT and OCB (r=-0.78, p=0.023) as well as complex motor tics (r=-0.68, p=0.064). In healthy controls, but not in the TS group, we found an age-related decline in SERT binding capacity (0.28% decrease per year, p=0.038). Our data are in agreement with previous results suggesting an impairment of the serotonergic system in TS. It can be speculated that the reduction in SERT binding capacity is associated with the degree of comorbid OCB. 相似文献
47.
The Bioperl toolkit: Perl modules for the life sciences 总被引:36,自引:4,他引:36
Stajich JE Block D Boulez K Brenner SE Chervitz SA Dagdigian C Fuellen G Gilbert JG Korf I Lapp H Lehväslaiho H Matsalla C Mungall CJ Osborne BI Pocock MR Schattner P Senger M Stein LD Stupka E Wilkinson MD Birney E 《Genome research》2002,12(10):1611-1618
The Bioperl project is an international open-source collaboration of biologists, bioinformaticians, and computer scientists that has evolved over the past 7 yr into the most comprehensive library of Perl modules available for managing and manipulating life-science information. Bioperl provides an easy-to-use, stable, and consistent programming interface for bioinformatics application programmers. The Bioperl modules have been successfully and repeatedly used to reduce otherwise complex tasks to only a few lines of code. The Bioperl object model has been proven to be flexible enough to support enterprise-level applications such as EnsEMBL, while maintaining an easy learning curve for novice Perl programmers. Bioperl is capable of executing analyses and processing results from programs such as BLAST, ClustalW, or the EMBOSS suite. Interoperation with modules written in Python and Java is supported through the evolving BioCORBA bridge. Bioperl provides access to data stores such as GenBank and SwissProt via a flexible series of sequence input/output modules, and to the emerging common sequence data storage format of the Open Bioinformatics Database Access project. This study describes the overall architecture of the toolkit, the problem domains that it addresses, and gives specific examples of how the toolkit can be used to solve common life-sciences problems. We conclude with a discussion of how the open-source nature of the project has contributed to the development effort. 相似文献
48.
The swelling behaviour, the time-dependence of the uptake of Cu2+-ions, and the pH-dependence of the uptake of Cu2+-, Ni2+-, Cd2+-, Zn2+- and Mg2+-ions of crosslinked poly[1-(4,5-dicarboxy-1-imidiazolyl)ethylene] ( 1 ) and poly{1-[p-(4,5-dicarboxy-2-imidazolyl)phenyl]ethylene} ( 2 ) were investigated. Both resins have a high selectivity for heavy metal ions. For resins 1 the uptake of heavy metal ions in the presence of an excess of EDTA was studied. Furthermore the possibility to remove Hg2+-ions from aqueous alkalichloride solutions by resin 1 was investigated. 相似文献
49.
Poly[1-N-(4-isothiocyanatophenyl)carbamoyloxymethylethylene-co-1-hydroxymethylethylene]s ( 5a – c ) were obtained by reaction of poly(allyl alcohol) ( 2 ) with 4-isothiocyanatophenyl isocyanate ( 3 ). In some cases 1,4-phenylenediisocyanate ( 4 ) was used as crosslinking agent. These reactive carriers were found to be suitable to immobilize enzymes by covalent bonds. The binding abilities of these polymers 5a – e for butylamine, 3,4-dichloroaniline, peptone (from lactalbumin), and papain were investigated. The enzymatic activity, the pH-optimum, the apparent Michaelis-constant KM(app), and the activity dependance on temperature were determined for the immobilized papain. 相似文献
50.
Georg Manecke Hans-Peter Aurich Peter Gergs Hans Langisch 《Macromolecular chemistry and physics.》1974,175(6):1833-1845
Amphoteric ion exchangers with uniform structure were obtained by copolymerization of aziridinyl monomers followed by alkaline saponification of the ester groups of the polymers. The following compounds were copolymerized: Diethyl 2,4-di(1-aziridinyl)glutarate ( 1 ) with either diethyl (1-aziridinyl)succinate ( 4 ), diethyl (1-aziridinyl)fumarate ( 5 ) or dimethyl (1-aziridinylmethyl)succinate ( 6 ); diethyl ester of 3,3′-(1,4-phenylene) and 3,3′-(1,3-phenylene)di[3-(1-aziridinyl)propionic acid] ( 2a ) and ( 2b ), respectively, with either methyl (1-aziridinyl) acetate ( 7 ) or methyl (1-aziridinyl)propionate ( 8 ); dimethyl 3,6-di(1-aziridinyl)cyclohexane-1,2-dicarboxylate ( 3 ) with dimethyl 6-(1-aziridinyl)cyclo-2-hexene-1,2-dicarboxylate ( 9 ). Further the dioctylester of 3,3′-(1,4-phenylene)di[3-(1-aziridinyl)propionic acid] ( 10 ) was homopolymerized. The properties of the amphoteric resins were investigated. In particular the binding ability for Cu2⊕, Ni2⊕, Zn2⊕, and Mg2⊕ ions and the swelling ability were studied as function of the pH of the solution. The uptake of CU2+ ions was determined as a function of time. An average capacity for Cu2+ ions of 2,5 to 3,75 mmol/g of dry resin was found at pH 5,5–6. 相似文献