全文获取类型
收费全文 | 11434篇 |
免费 | 574篇 |
国内免费 | 52篇 |
专业分类
耳鼻咽喉 | 95篇 |
儿科学 | 208篇 |
妇产科学 | 190篇 |
基础医学 | 1874篇 |
口腔科学 | 228篇 |
临床医学 | 1033篇 |
内科学 | 2259篇 |
皮肤病学 | 237篇 |
神经病学 | 1356篇 |
特种医学 | 570篇 |
外科学 | 1932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 | 704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 | 744篇 |
2010年 | 441篇 |
2009年 | 440篇 |
2008年 | 688篇 |
2007年 | 716篇 |
2006年 | 671篇 |
2005年 | 668篇 |
2004年 | 625篇 |
2003年 | 597篇 |
2002年 | 571篇 |
2001年 | 102篇 |
2000年 | 85篇 |
1999年 | 91篇 |
1998年 | 126篇 |
1997年 | 105篇 |
1996年 | 76篇 |
1995年 | 78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
81.
Pussinen PJ Laatikainen T Alfthan G Asikainen S Jousilahti P 《Clinical and diagnostic laboratory immunology》2003,10(5):897-902
This study aimed to clarify how concentrations of vitamin C in plasma relate to the serology of periodontitis. The random sample used comprised 431 men, 194 from Finland and 237 from Russia. The plasma vitamin C concentration was determined by o-phtaldialdehyde-fluorometry, and serum immunoglobulin G antibodies to Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were determined by a multiserotype enzyme-linked immunosorbent assay (ELISA). The mean plasma vitamin C concentration was higher (P < 0.001) in Finnish subjects (mean +/- standard deviation, 4.5 +/- 2.8 mg/liter) than in Russian subjects (1.4 +/- 1.8 mg/liter). Mean antibody levels to both A. actinomycetemcomitans (4.7 +/- 3.6 versus 5.2 +/- 3.1 ELISA units [P = 0.05]) and P. gingivalis (5.7 +/- 2.5 versus 7.6 +/- 2.9 ELISA units [P < 0.001]) were lower in Finnish men than in Russian men. In the combined Finnish and Russian population, the antibody levels to P. gingivalis were negatively correlated with vitamin C concentrations (r = -0.22; P < 0.001); this association remained statistically significant (P = 0.010) in a linear regression model after adjustment for confounding factors. The proportion of P. gingivalis-seropositive subjects decreased with increasing vitamin C concentrations (P for trend, <0.01), but no trend was seen among A. actinomycetemcomitans-seropositive subjects. In conclusion, P. gingivalis infection is associated with low concentrations of vitamin C in plasma, which may increase colonization of P. gingivalis or disturb the healing of the infected periodontium. 相似文献
82.
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
83.
Summary Two groups of Biomphalaria glabrata snails primarily infected with Angiostrongylus cantonensis were secondarily exposed to infection with Schistosoma mansoni. To investigate any antagonistic effect of a first infection on a superimposed one and to compare to singly and non-infected snails, a series of experiments was undertaken in which snails were individually exposed, variously, to 1,000 and 2,000 first-stage larvae of A. cantonensis and then to 5 and 10 miracidia of S. mansoni 1 day and 3 weeks later.Snails became infected with S. mansoni in both groups of snails with double infections and shed cercariae after the same incubation period as in the singly infected groups. The number of snails shedding cercariae simultaneously was similar in single and double infection groups during the first two weeks of shedding, after which this number decreased somewhat in doubly infected groups. Snails with double infection showed higher cumulative mortality rates than in snail groups with single infection with either A. cantonensis or S. mansoni. Therefore, initial infection of B. glabrata with A. cantonensis produced no inhibitory or retarding effect on subsequent infection of snails with S. mansoni.
Zusammenfassung Zwei Gruppen der Süßwasserschnecke Biomphalaria glabrata, die zuvor mit 1000 bzw. 2000 ersten Larven von Angiostrongylus cantonensis pro Schnecke infiziert worden waren, wurden zur Feststellung eines eventuellen antagonistischen Effekts zwischen beiden Parasiten, einen Tag und drei Wochen später mit 5 bzw. 10 Miracidien von Schistosoma mansoni infiziert. Nicht infizierte und mit jeweils nur einer der beiden Parasitenarten infizierte Schnecken dienten als Kontrolle.In beiden doppelt infizierten Gruppen ging die S. mansoni-Infektion sehr gut an, und die Ausscheidung von Cercarien begann nach der gleichen Entwicklungszeit wie bei den nur mit S. mansoni infizierten Kontrollgruppen. Die Anzahl Cercarien ausscheidender Schnecken war in den beiden ersten Wochen bei den jeweils einzeln und doppelt infizierten Gruppen sehr ähnlich, während sie sich in der Folgezeit in den doppelt infizierten Gruppen rasch verminderte. In Gruppen mit Doppelinfektion zeigte sich eine höhere Mortalität als bei den jeweils nur mit A. cantonensis oder S. mansoni infizierten Schnecken. Eine Beeinflussung der Entwicklung von S. mansoni durch die vorausgegangene Nematodeninfektion konnte nicht nachgewiesen werden.相似文献
84.
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
85.
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
86.
Tamotsu Yoshimura Winfried Storck Georg Manecke 《Macromolecular chemistry and physics.》1977,178(1):75-96
It was found that the reaction of 1,2-dicyano-1,2-ethenedithiolate, resp. of bis(1,2-dicyano-1,2-ethenedithiolato)cuprate(2-), with Cu2+ does not lead to copper bis(1,2-dicyano-1,2-ethenedithiolato)cuprate(2-) dihydrate ( 1a ) as described in the literature but to a reaction product which has a complex structure containing mainly Cu+. This compound as well as complexes with the same ligand, but with Cu+, Cu2+ or Cu3+ as the central atom, were synthesized and tested with and without added cuprous chloride as catalysts for the oxidative polymerization of 2,6-dimethylphenol. Included in this investigation were some copper complexes with the isomeric ligand 2,2-dicyano-1,1-ethenedithiolate. 相似文献
87.
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
88.
Summary Slices of the rabbit hippocampus were labelled with 3H-noradrenaline, superfused continuously with a modified Krebs-Henseleit medium containing the uptake inhibitor cocaine and stimulated electrically (2 ms, 3 Hz, 24 mA, 5 V/cm). Phorbol 12,13-dibutyrate (PDB), a potent activator of protein kinase C (PKC), strongly enhanced the electrically-evoked overflow of tritium. In contrast, polymyxin B, a relatively selective inhibitor of PKC, diminished the evoked tritium overflow in a time-and concentration-dependent manner. The enhancement of the evoked overflow of tritium caused by PDB was strongly reduced in the presence of polymyxin B (100 mol/l). These results suggest 1. that PKC may be involved in the physiological mechanism of action-potential-induced noradrenaline release from noradrenergic nerve terminals and 2. that the PDB-induced enhancement of noradrenaline release may be due to a direct activation of PKC.Abbreviations PKC
protein kinase C
- PDB
phorbol 12,13-dibutyrate
- TPA
12-O-tetradecanoyl 13-acetate 相似文献
89.
Hans-Martin Becker MD Jairo Ramirez MD Vincent Echave MD Georg Heberer MD 《Annals of vascular surgery》1986,1(2):196-200
From July 1979 to December 1985 we observed 51 patients with traumatic lesions of the descending thoracic aorta. Twenty-nine had acute ruptures, mostly accompanied by multiple injuries, and 27 had to be operated upon immediately. Twenty-two patients (19 males, 3 females) had chronic traumatic aneurysms of the descending thoracic aorta (more than six weeks after trauma). Mean age at the time of trauma was 24 years. Mean age at time of surgery was 36.5 years. Twelve patients were symptomatic. All were treated surgically. At surgery, complete aortic disruption was found in 15 patients and partial rupture in seven. We did not use aortic shunting of any kind, only aortic cross-clamping. Hypertension was controlled by intravenous drug infusion. The ruptured aortic segment was replaced in all cases by prosthetic Dacron graft. There were no operative deaths. One patient (age 77) died 11 weeks after surgery from multiple organ failure. One case of postoperative paraplegia was observed. This patient recovered almost completely from his neurological deficit. 相似文献
90.
Kerstin Kempf Martin Rhling Winfried Banzer Klaus Michael Braumann Martin Halle David McCarthy Hans Georg Predel Isabelle Schenkenberger Susanne Tan Hermann Toplak Aloys Berg Stephan Martin 《Nutrients》2021,13(5)
Lifestyle interventions, including meal replacement, are effective in the prevention and treatment of type-2-diabetes and obesity. Since insulin is the key weight regulator, we hypothesised that the addition of meal replacement to a lifestyle intervention reduces insulin levels more effectively than lifestyle intervention alone. In the international multicentre randomised controlled ACOORH (Almased Concept against Overweight and Obesity and Related Health Risk) trial, overweight or obese persons who meet the criteria for metabolic syndrome (n = 463) were randomised into two groups. Both groups received nutritional advice focusing on carbohydrate restriction and the use of telemonitoring devices. The intervention group substituted all three main meals per day in week 1, two meals per day in weeks 2–4, and one meal per day in weeks 5–26 with a protein-rich, low-glycaemic meal replacement. Data were collected at baseline and after 1, 3, 6 and 12 months. All datasets providing insulin data (n = 446) were included in this predefined subanalysis. Significantly higher reductions in insulin (−3.3 ± 8.7 µU/mL vs. −1.6 ± 9.8 µU/mL), weight (−6.1 ± 5.2 kg vs. −3.2 ± 4.6 kg), and inflammation markers were observed in the intervention group. Insulin reduction correlated with weight reduction and the highest amount of weight loss (−7.6 ± 4.9 kg) was observed in those participants with an insulin decrease > 2 µU/mL. These results underline the potential for meal replacement-based lifestyle interventions in diabetes prevention, and measurement of insulin levels may serve as an indicator for adherence to carbohydrate restriction. 相似文献