全文获取类型
收费全文 | 177150篇 |
免费 | 9176篇 |
国内免费 | 316篇 |
专业分类
耳鼻咽喉 | 2621篇 |
儿科学 | 5526篇 |
妇产科学 | 3840篇 |
基础医学 | 26810篇 |
口腔科学 | 5281篇 |
临床医学 | 15477篇 |
内科学 | 33452篇 |
皮肤病学 | 4791篇 |
神经病学 | 18026篇 |
特种医学 | 7986篇 |
外科学 | 27138篇 |
综合类 | 809篇 |
一般理论 | 46篇 |
预防医学 | 9273篇 |
眼科学 | 3751篇 |
药学 | 11746篇 |
中国医学 | 287篇 |
肿瘤学 | 9782篇 |
出版年
2023年 | 1056篇 |
2022年 | 1001篇 |
2021年 | 2185篇 |
2020年 | 1813篇 |
2019年 | 2312篇 |
2018年 | 4055篇 |
2017年 | 3407篇 |
2016年 | 4269篇 |
2015年 | 4056篇 |
2014年 | 4586篇 |
2013年 | 7358篇 |
2012年 | 10123篇 |
2011年 | 11051篇 |
2010年 | 6281篇 |
2009年 | 4588篇 |
2008年 | 10705篇 |
2007年 | 11175篇 |
2006年 | 10695篇 |
2005年 | 10576篇 |
2004年 | 9904篇 |
2003年 | 9685篇 |
2002年 | 9419篇 |
2001年 | 5657篇 |
2000年 | 6989篇 |
1999年 | 4065篇 |
1998年 | 1794篇 |
1997年 | 1447篇 |
1996年 | 1135篇 |
1995年 | 959篇 |
1994年 | 911篇 |
1993年 | 867篇 |
1992年 | 877篇 |
1991年 | 756篇 |
1990年 | 732篇 |
1989年 | 729篇 |
1988年 | 621篇 |
1987年 | 707篇 |
1986年 | 592篇 |
1985年 | 782篇 |
1984年 | 747篇 |
1983年 | 627篇 |
1982年 | 653篇 |
1981年 | 616篇 |
1980年 | 551篇 |
1979年 | 552篇 |
1978年 | 507篇 |
1977年 | 522篇 |
1976年 | 423篇 |
1975年 | 455篇 |
1974年 | 437篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
O M Ariyürek F Balkanci Ü Aydingöz M Önerci 《Surgical and radiologic anatomy : SRA》1996,18(2):137-139
Summary Anatomic variations are important in preendoscopic CT evaluation of the paranasal sinuses. In this study, we investigated whether the superior turbinate could become pneumatised like the middle turbinate, pneumatisation of which is well-known. Images of 52 patients who underwent CT examination prior to endoscopic sinus surgery and who had normally aerated posterior ethmoidal cells and an unobscured nasal cavity were retrospectively evaluated. The patients were 12–68 years old (median age, 35 years); 28 were women and 24 were men. Pneumatisation of the superior turbinates was graded in two groups as minimal or marked. Pneumatisation was evident in 25 patients (48%). 13 unilateral (25%), 8 bilateral (15%) pneumatisations were detected in the group graded as minimal, whereas 1 unilateral and 3 bilateral pneumatisations were present in the markedly (8%) pneumatised group of patients. Superior turbinates were seemingly aerated through the posterior ethmoid cells. The superior turbinates can be pneumatised as the middle turbinate is a not frequent anatomic variation that should be taken into account in preendoscopic CT evaluation of the paranasal sinuses.
La pneumatisation du cornet nasal supérieur : une variation anatomique courante ?
Résumé Les variations anatomiques sont importantes à connaitre dans le cadre du bilan tomodensitométrique précédant une chirurgie endoscopique des sinus paranasaux. Dans cette étude, nous avons recherché si le cornet nasal supérieur pouvait être pneumatisé comme l'est le cornet nasal moyen, entité anatomique bien connue. Les images de 52 patients ayant eu une tomodensitométrie avant chirurgie endoscopique et montrant des cellules ethmoïdales postérieures normalement pneumatisées et une cavité nasale nonopaque, ont été évaluées rétrospectivement. Les patients, 28 femmes et 24 hommes, étaient âgés de 12 à 68 ans (moyenne : 35 ans). La pneumatisation du cornet nasal supérieur a été classée en deux groupes; minime et prononçée. Cette pneumatisation était patente chez 25 patients (48 %). Treize pneumatisations unilatérales (25 %) et 8 pneumatisations bilatérales (15 %) furent retrouvées dans le groupe présentant une pneumatisation minime alors que 1 pneumatisation unilatérale et 3 bilatérales (8 %) étaient présentes dans le groupe dont la pneumatisation était plus marquée. Les cornets nasaux supérieurs semblaient être aérés par les cellules ethmoïdales postérieures. Les cornets nasaux supérieurs peuvent être pneumatisés, comme le sont les cornets nasaux moyens, avec une fréquence non-exceptionnelle. Cette variation anatomique mérite d'être prise en considération dans le bilan tomodensitométrique précédant toute chirurgie endoscopique des sinus paranasaux.相似文献
992.
We analyzed the effect of the PAF receptor antagonist (+)-cis-3,5-dimethyl-2-(3-pyridyl) thiazolidin-4-one hydrochloride (SM-12502) on the release of leukotriene B4 and IL-8 from human leukocytes. Peripheral blood from healthy donors was separated in two different fractions: polymorphonuclear leukocytes (PMN) and a lymphocyte, monocyte and basophil granulocyte cell fraction (LMB). After incubation of the cell population with different concentrations of SM-12502 the cells were subsequently stimulated with either the Ca ionophore A23187, the bacterial derived peptide fMLP, or with an activator of heterotrimetric G-proteins, the sodium fluoride (NaF, in the presence of Al3+). The PAF receptor antagonist led to a concentration and time dependent inhibition of LTB4 formation and IL-8 release from PMN and LMB. Our data clearly indicate an inhibitory effect of the PAF receptor antagonist SM-12502 on the formation of mediators of the lipoxygenase pathway and on the release of IL-8. 相似文献
993.
Detection of DNA damage after hyperbaric oxygen (HBO) therapy 总被引:4,自引:0,他引:4
Hyperbaric oxygen HBO therapy is successfully used for the treatmentof a variety of conditions. However, exposure to high concentrationsof oxygen is known to induce damage to cells, possibly due toan increased oxygen radical production. As reactive oxygen speciesalso cause DNA damage, we investigated the DNA-damaging effectof HBO with the alkaline version of the single cell gel testcomet assay. Oxidative DNA base modifications were determinedby converting oxidized DNA bases to strand breaks using bacterialformamidopyrimidine-DNA glycosylase FPG, a DNA repair enzyme,which specifically nicks DNA at sites of 8-oxo-guanines andformamidopyrimidines. HBO treatment under therapeutic conditionsclearly and reproducibly induced DNA damage in leukocytes ofall test subjects investigated. Increased DNA damage was foundimmediately at the end of the treatment, while 24 h later, noeffect was found. Using FPG protein we detected significantoxidative base damage after HBO treatment DNA damage was detectedonly after the first treatment and not after further treatmentsunder the same conditions, indicating an increase in antioxidantdefences. DNA damage did not occur when the HBO treatment wasstarted with a reduced treatment time which was then increasedstepwise.
3To whom correspondence should be addressed 相似文献
994.
Ohne Zusammenfassung 相似文献
995.
996.
Summary Lung function was studied double blind and randomized in 5 patients with mild asthma bronchiale and 10 normal adults before and 30, 60 and 90 minutes after one drop of 0.5% Timolol, 0.6% Metipranolol or 0.9% NaCl in each eye.In the asthmatics bronchoconstriction was seen after both -receptor blocking agents, more pronounced after Timolol than after Metripranolol. There was a decrease in the forced expiratory volume in one second (FEV1.0) of 32, respectively 18%. No changes were observed in the normal subjects.In a separate studie no significant changes were seen in the mean values of 10 other asthmatic subjects after 1% Pindolol, 3% Pilocarpin or 0.9% NaCl.However, in two patients FEV1.0 was reduced by 15% and 20% of the control values after applying Pindolol.In summary, not only -receptorblocking agents without ISA produce a bronchoconstriction in asthmatic subjects, but also -blocker with ISA in individual cases.
Abkürzungen FEV1.0 Ein-Sekunden-Wert - ISA intrinsische sympathikotone Aktivität - MEV maximaler exspiratorischer Fluß - Rtos oszillatorische Resistance Ein Teil der Daten wurde der Dissertationsschrift von Frau Janette Gehre entnommen. 相似文献
Abkürzungen FEV1.0 Ein-Sekunden-Wert - ISA intrinsische sympathikotone Aktivität - MEV maximaler exspiratorischer Fluß - Rtos oszillatorische Resistance Ein Teil der Daten wurde der Dissertationsschrift von Frau Janette Gehre entnommen. 相似文献
997.
The central role of interleukin-1 (IL-1) in several disease processes, including fever and inflammation, makes the characterization of ligand-receptor interaction of prime importance.The role of arginine (Arg) side chains of hr-IL-1 in receptor recognition was studied by the modification of Arg residues with the specific reagent 1,2-cyclohexanedione. It was found that chemical modification of Arg residues decreased the binding potential of IL-1 to type I receptor dramatically (by 230-fold) while the affinity to type II receptor was reduced only moderately (by 10-fold), with an insignificant reduction of the dissociation rate.These studies suggest that intact Arg side chains of IL-1 may be necessary for high affinity binding to type I IL-1 receptor, but have less importance for the interaction of IL-1 with type II IL-1 receptor.This observation may be useful in the study of type II IL-1 receptor-mediated biological responses and design of receptor-subtype specific ligands as well. 相似文献
998.
N. Drakoulis I. Cascorbi J. Brockmöller C. R. Gross I. Roots 《Journal of molecular medicine (Berlin, Germany)》1994,72(3):240-248
Genetic differences in the metabolism of carcinogens may codetermine individual predisposition to cancer. Cytochrome P-4501A1 (CYP1A1) metabolically activates precarcinogens in cigarette smoke, such as benzo(a)pyrene, which is also an inducer of CYP1A1. Two point mutations have been reported, m1 in the 3-flanking region (6235T to C), and m2 within exon 7 (4889A to G), the latter leading to an isoleucine to valine exchange. In the Japanese population ml and m2 are correlated with lung cancer, suggesting an increased susceptibility to cigarette smoking related lung cancer. We studied 142 lung cancer and 171 reference patients in an ethnically homogeneous German group for m1 and m2 mutations by restriction fragment length polymorphism and allele-specific polymerase chain reaction, respectively. No statistically significant difference was found in the distribution of m1 alleles between lung cancer and controls; the frequency was 8.5% and 7.3% of the alleles, respectively (odds ratio = 1.17). A trend to an overrepresentation of ml alleles was observed among 52 squamous cell carcinoma patients (odds ratio = 1.65). In contrast, the frequency of m2 alleles in lung cancer patients was twofold higher (6.7%) than in the reference group (3.2%; odds ratio = 2.16; 95% confidence limits 0.96–5.11, P = 0.033); the odds ratio of m2 alleles in squamous cell carcinoma was 2.51 (95% confidence limits 0.85–7.05, P = 0.05). There was a close genetic linkage of m2 to m1 (10 of 11 reference patients), but a significantly higher number of cancer patients showed no linkage compared to the controls (odds ratio = 8.89, 95% confidence limits 0.83–433, P = 0.04). Thus no association was found between presence of ml alleles and lung cancer, but, in contrast, m2 alleles proved as a hereditary risk factor, especially if not linked with m1 alleles.Abbreviations Ah
aryl hydrocarbon
- CYP1A1
cytochrome P4501A1
-
CYP1A1
CYP1A1 gene
- PCR
polymerase chain reaction
- PY
pack years
- RFLP
restriction fragment length polymorphism
Correspondence to: N. Drakoulis 相似文献
999.
The male genital system ofCephalobaena tetrapoda comprises the unpaired testis and seminal vesicle and the paired connecting tubes, ejaculatory bulbs, vasa deferentia, and dilators. These lead into the genital atrium, which can be everted to form the copulatory organ. An ultrastructural analysis of each of these compounds is presented, including spermiogenesis, which was traced in some important stages. The diverging nomenclature of the complicated male genital system was unified and partly changed: where the vas deferens and dilator merge, the former loses its epithelial lining; the cuticular tube is called the cirrus. Anteriorly, the dilator also gives rise to a cuticular, semilunar tube. The cirrus and semilunar tube run parallel and reach the genital atrium, which can be evaginated to form the copulatory organ. Apparently, the male genital system represents an original type from which the complicated porocephalic systems may be derived. 相似文献
1000.
S. Cheng P. V. Komi H. Kyröläinen D. H. Kim K. Häkkinen 《European journal of applied physiology》1989,59(1-2):128-130
Summary Vibrational wave propagation was tested in vivo on the tibial bone of both legs of 56 female volunteers. The impact was produced
by a hammer with a force strain gauge and the response was monitored by two accelerometers. The peak amplitude of the accelerations,
the velocity of the acceleration wave propagation and damping were analysed for comparison among the different age groups.
The results showed significant negative correlations between age and the peak amplitude of acceleration, and the velocity
of acceleration wave propagation (p<0.01). The damping time of the acceleration wave also had a negative correlation with age. These findings suggested that
age differences were related to the differences in the mechanical properties of bone. With reduction of bone mineral density,
the velocity of the vibrational wave propagation would decrease, with simultaneous increase in impedance. In addition, wave
absorption would be accelerated. It is suggested that this method could be used as an indicator of bone density. The method
could also be developed to provide an index to monitor the progress of osteoporosis.
Visiting research assistant from the Department of Sport Medicine, Chengdu College of Physical Education, Chengdu, People's
Republic of China
Visiting research assistant from Seoul National University, Seoul, South Korea 相似文献