全文获取类型
收费全文 | 19186篇 |
免费 | 1228篇 |
国内免费 | 85篇 |
专业分类
耳鼻咽喉 | 181篇 |
儿科学 | 610篇 |
妇产科学 | 417篇 |
基础医学 | 2564篇 |
口腔科学 | 380篇 |
临床医学 | 2223篇 |
内科学 | 4580篇 |
皮肤病学 | 533篇 |
神经病学 | 1929篇 |
特种医学 | 417篇 |
外科学 | 1481篇 |
综合类 | 104篇 |
一般理论 | 8篇 |
预防医学 | 1945篇 |
眼科学 | 316篇 |
药学 | 1295篇 |
中国医学 | 69篇 |
肿瘤学 | 1447篇 |
出版年
2023年 | 155篇 |
2022年 | 272篇 |
2021年 | 556篇 |
2020年 | 346篇 |
2019年 | 534篇 |
2018年 | 666篇 |
2017年 | 409篇 |
2016年 | 496篇 |
2015年 | 561篇 |
2014年 | 782篇 |
2013年 | 1011篇 |
2012年 | 1589篇 |
2011年 | 1601篇 |
2010年 | 834篇 |
2009年 | 792篇 |
2008年 | 1325篇 |
2007年 | 1296篇 |
2006年 | 1253篇 |
2005年 | 1242篇 |
2004年 | 1074篇 |
2003年 | 1037篇 |
2002年 | 951篇 |
2001年 | 104篇 |
2000年 | 89篇 |
1999年 | 147篇 |
1998年 | 165篇 |
1997年 | 149篇 |
1996年 | 141篇 |
1995年 | 111篇 |
1994年 | 80篇 |
1993年 | 93篇 |
1992年 | 66篇 |
1991年 | 43篇 |
1990年 | 45篇 |
1989年 | 49篇 |
1988年 | 32篇 |
1987年 | 23篇 |
1986年 | 40篇 |
1985年 | 39篇 |
1984年 | 33篇 |
1983年 | 32篇 |
1982年 | 32篇 |
1981年 | 35篇 |
1980年 | 36篇 |
1979年 | 18篇 |
1978年 | 16篇 |
1976年 | 14篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
101.
Maria Suárez-Cervera Teresa Castells Ana Vega-Maray Esther Civantos Victoria del Pozo Delia Fernández-González Stella Moreno-Grau Angel Moral Carmen López-Iglesias Carlos Lahoz Juan A Seoane-Camba 《Annals of allergy, asthma & immunology》2008,101(1):57-66
BACKGROUND: Cupressaceae is a family of plants resistant to airborne contamination, and its pollen is the main cause of winter allergic respiratory diseases, especially in North America, Japan, and Mediterranean countries. Recently, a major allergen from Cupressus arizonica pollen grains, Cup a 3, was cloned and expressed. OBJECTIVE: To study the effects of air pollution on the expression of Cup a 3, a thaumatinlike protein, in C. arizonica pollen grains using a combination of transmission electron microscopy and immunocytochemical techniques. METHODS: Observations were made in mature and hydrated C. arizonica pollen grains from various regions in Spain with different degrees of air pollution. Specimens were fixed using freezing protocols, and ultrathin sections were incubated with anti-rCup a 3 rabbit polyclonal antibodies. RESULTS: Labeling of Cup a 3 was detected in mature and hydrated C. arizonica pollen grains. It was more intense in pollen from polluted air regions, and abundant gold particles were observed as they were released through the pollen grain walls. Furthermore, gold particles remained abundant in the pollen cytoplasm. The labeling was noticeably lower in pollen grains from unpolluted air regions. CONCLUSIONS: Cup a 3 is present in the cytoplasm and walls of cypress pollen grains during the air dispersion and hydration stages. The abundance of Cup a 3 in pollen grains under polluted air conditions indicates that these cypresses intensify their activity as a defense from environmental pollution, thus strengthening their allergenicity. 相似文献
102.
Diane J. Pincus MD Teresa R. Humeston BS Richard J. Martin MD 《The Journal of allergy and clinical immunology》1997,100(6):771-774
Background: Chronotherapy studies with inhaled corticosteroids have shown optimal therapeutic benefit when steroids are administered four times per day (QID) or once daily at 3 PM.Objective: This study evaluated whether more convenient once-daily dosage times (8 AM and 5:30 PM) produce improvement in asthma equivalent to QID.Methods: Efficacy outcome measures included FEV1, peak expiratory flow rates, bronchial responsiveness, use of β2-agonists, nocturnal awakenings, and responses to a quality of life questionnaire. Systemic effects were blood eosinophil count, cortisol level, 24-hour urinary cortisol, and evaluation for oral candidiasis and dysphonia.Results: Baseline measurements for all three treatment groups were similar. For morning peak expiratory flow rate, significant improvement was seen for the QID group (p = 0.001) and the 5:30 PM group (p = 0.003), but not the 8 AM group (p = 0.75). For evening peak expiratory flow rate, significant improvement was seen for the QID group (p = 0.005) and the 5:30 PM group (p = 0.01), but not for the 8 AM group (p = 0.47). There were significant improvements in all other outcome variables for each group except PC20. There was a significant improvement in PC20 only in the QID group. The systemic effects of the three regimens were comparable.Conclusion: Dosing of inhaled steroid at 5:30 PM had no increased systemic effects and produced efficacy similar to QID dosing. Dosing at 8 AM did not produce results consistently comparable to QID dosing. Optimal once-daily dosing of inhaled steroid is between 3 PM and 5:30 PM. 相似文献
103.
Giulia Kramar Teresa Aguado Jacques Louis Giuseppe Del Giudice Paul-Henri Lambert 《European journal of immunology》1993,23(10):2551-2556
BALB/c mice injected at birth with semi-allogeneic F1 spleen cells become tolerant to alloantigens as shown by their CTL unresponsiveness to the corresponding alloantigen and the persistence of donor F1 cells into the BALB/c host. Moreover, these mice develop a transient systemic lupus erythematosis-like autoimmune syndrome characterized by splenomegaly, glomerulonephritis, thrombocytopenia and abnormal serological findings, such as several autoantibodies and IgG1 hypergammaglobulinemia. Recent studies done in our laboratory have shown that donor F1 B cells persisting in the host are responsible for the production of autoantibodies and must be activated in vivo by the host CD4+ T lymphocytes in a MHC class II-restricted fashion. In the present work, we have focused our attention on the ability of splenic CD4+ T cells recovered at different periods from BALB/c mice injected at birth with (CBA/Ca × BALB. Ighb) Fl spleen cells to interact with and activate F1 semi-allogeneic spleen cells in vitro. We show that (i) only CD4+ T cells from 2- and 3-week-old tolerant BALB/c mice preferentially produce IL-4 and IL-5 in response to a F1 semi-allogeneic in vitro stimulation, (ii) CD4+ T cells purified from 3-week-old tolerant BALB/c mice are able to induce in vitro IgG and IgM production by F1 B cells. Taken together, these results strongly suggest that host CD4+ T cells, belonging to the TH2 subset progressively lose their reactivity towards the F1 semi-allogeneic persistent B cells, reaching a state of unresponsiveness that correlates with the disappearance of serum autoantibodies and autoimmune pathology. 相似文献
104.
Multilocus sequence typing of Swedish invasive group B streptococcus isolates indicates a neonatally associated genetic lineage and capsule switching 下载免费PDF全文
Luan SL Granlund M Sellin M Lagergård T Spratt BG Norgren M 《Journal of clinical microbiology》2005,43(8):3727-3733
Streptococcus agalactiae, also designated group B streptococcus (GBS), is an important pathogen in neonates, pregnant women, and nonpregnant adults with predisposing conditions. We used multilocus sequence typing (MLST) to characterize 158 GBS isolates that were associated with neonatal and adult invasive disease and that were collected in northern and western Sweden from 1988 to 1997. Five major genetic lineages (sequence type [ST] 19, ST-17, ST-1, ST-23, and ST-9 complexes) were identified among the isolates, including serotype Ia, Ib, and II to V isolates, indicating a highly clonal population structure among invasive GBS isolates. A number of STs were found to contain isolates of different serotypes, which indicates that capsule switching occurred rather frequently. Two distantly related genetic lineages were identified among isolates of serotype III, namely, clonal complex 19 (CC19), and CC17. CC19 was equally common among isolates from adult and neonatal disease (accounting for 10.3% of GBS isolates from adult disease and 18.7% from neonatal disease), whereas CC17 significantly appeared to be associated with neonatal invasive disease (isolated from 21.9% of neonatal isolates but only 2.6% of adult isolates). The distribution of the mobile elements GBSi1 and IS1548 reveals that they can act as genetic markers for lineages CC17 and CC19, respectively. 相似文献
105.
Enrique E Pineda F Malek T Bartra J Basagaña M Tella R Castelló JV Alonso R de Mateo JA Cerdá-Trias T San Miguel-Moncín Mdel M Monzón S García M Palacios R Cisteró-Bahíma A 《The Journal of allergy and clinical immunology》2005,116(5):1073-1079
BACKGROUND: Food allergy may be life-threatening, and patients affected need to receive accurate diagnoses and treatment. Hazelnut has often been implicated as responsible for allergic reactions, and trace quantities can induce systemic reactions. OBJECTIVE: The aim of this study was to evaluate the efficacy and tolerance of sublingual immunotherapy with a standardized hazelnut extract in patients allergic to hazelnut. METHODS: This was a randomized, double-blind, placebo-controlled study. Inclusion criteria were a history of hazelnut allergy and positive skin prick test and double-blind placebo-controlled food challenge results. Patients were then randomly assigned into 2 treatment groups (hazelnut immunotherapy or placebo). Efficacy was assessed by double-blind, placebo-controlled food challenge after 8 to 12 weeks of treatment. Blood samples were drawn for measurement of specific IgE, IgG(4), and serum cytokines before and after treatment. RESULTS: Twenty-three patients were enrolled and divided into 2 treatment groups. Twenty-two patients reached the planned maximum dose at 4 days. Systemic reactions were observed in only 0.2% of the total doses administered. Mean hazelnut quantity provoking objective symptoms increased from 2.29 g to 11.56 g (P = .02; active group) versus 3.49 g to 4.14 g (placebo; NS). Moreover, almost 50% of patients who underwent active treatment reached the highest dose (20 g), but only 9% in the placebo. Laboratory data showed an increase in IgG(4) and IL-10 levels after immunotherapy in only the active group. CONCLUSION: Our data confirm significant increases in tolerance to hazelnut after sublingual immunotherapy as assessed by double-blind, placebo-controlled food challenge, and good tolerance to this treatment. 相似文献
106.
Comparison of Broth Microdilution Method Using Haemophilus Test Medium and Agar Dilution Method for Susceptibility Testing of Eikenella corrodens 下载免费PDF全文
Luis Alcal Fernando García-Garrote Emilia Cercenado Teresa Pelez Gema Ramos Emilio Bouza 《Journal of clinical microbiology》1998,36(8):2386-2388
Susceptibility testing of Eikenella corrodens is usually performed by a Mueller-Hinton sheep blood agar dilution (AD) method. However, this method is impractical for testing only a few strains. We compared AD with the broth microdilution method using Haemophilus test medium (HTM) in order to determine the susceptibility of 36 clinical isolates of E. corrodens to eight antimicrobial agents. MICs obtained by the HTM method yielded 95.5 and 84% agreement (within 2 and 1 log2 dilutions, respectively) with those obtained by AD. The HTM method with incubation in CO2 for 48 h was highly reproducible and constitutes an easy alternative for antimicrobial susceptibility testing of E. corrodens. 相似文献
107.
Teresa Baran Andrzej Duda Stanistaw Penczek 《Macromolecular chemistry and physics.》1984,185(11):2337-2346
The anionic polymerization of exo-3,4,5-trithiatetracyclo[5.5.1.O2,6.O8,12]tridec-10-ene ( 1 ) in bulk and/or in aromatic solvents (benzene, toluene) was studied. The polymerization was initiated with sodium benzenethiolate (sodium cation complexed with dibenzo-18-crown-6). Polymers with high-molecular weights were obtained (M n ≈ 105, osmometrically). The polymerization was found to be living and reversible; the equilibrium monomer concentration increases with the temperature. The ceilling temperature was estimated as 167°C. The thermodynamic data of the polymerization in toluene was determined and compared with those of the polymerization of exo-3,4,5-trithiatricyclo[5.2.O2,6]decane. The standard enthalpy ΔH = ?(6,6 ± 0,6)kJ · mol 1 and entropy ΔS = ?(29,3 ± 2,1)J · mol 1 · K 1 of the polymerization of 1 were evaluated from the temperature dependence of the equilibrium monomer concentration, determined dilatometrically. 相似文献
108.
Nunes S Sá-Leão R Carriço J Alves CR Mato R Avô AB Saldanha J Almeida JS Sanches IS de Lencastre H 《Journal of clinical microbiology》2005,43(3):1285-1293
Of the nasopharyngeal cultures recovered from 942 day care center (DCC) attendees in Lisbon, Portugal, 591 (62%) yielded Streptococcus pneumoniae during a surveillance performed in February and March of 1999. Forty percent of the isolates were resistant to one or more antimicrobial agents. In particular, 2% were penicillin resistant and 20% had intermediate penicillin resistance. Multidrug resistance to macrolides, lincosamides, and tetracycline was the most frequent antibiotype (17% of all isolates). Serotyping and molecular typing by pulsed-field gel electrophoresis were performed for 202 out of 237 drug-resistant pneumococci (DRPn). The most frequent serotypes were 6B (26%), 14 (22%), 19F (16%), 23F (10%), and nontypeable (12%). The majority (67%) of the DRPn strains were representatives of nine international clones included in the Pneumococcal Molecular Epidemiology Network; eight of them had been detected in previous studies. Fourteen novel clones were identified, corresponding to 26% of the DRPn strains. The remaining 7% of the strains were local clones detected in our previous studies. Comparison with studies conducted since 1996 in Portuguese DCCs identified several trends: (i) the rate of DRPn frequency has fluctuated between 40 and 50%; (ii) the serotypes most frequently recovered have remained the same; (iii) nontypeable strains appear to be increasing in frequency; and (iv) a clone of serotype 33F emerged in 1999. Together, our observations highlight that the nasopharynxes of children in DCCs are a melting pot of successful DRPn clones that are important to study and monitor if we aim to gain a better understanding on the epidemiology of this pathogen. 相似文献
109.
Xiaoyan Sun Gregory M Cole Teresa Chu Weiming Xia Douglas Galasko Haruyasu Yamaguchi Kentaro Tanemura Sally A Frautschy Akihiko Takashima 《Neurobiology of aging》2002,23(2):195-203
Intracellular Abeta was examined in both a neuronal cell line (B103) expressing human APP with Swedish mutation and a non-neuronal cell line (Chinese hamster ovary, CHO) expressing wild human APP. Exposure of the APP695sw-transfected B103 cells to okadaic acid for 3 h, Abeta immunostaining was enhanced, as demonstrated by two independent anti-Abeta antibodies. The confocal microscopic study revealed that the immunoreactivity of Abeta was mainly colocalized with a Golgi marker and partially with an ER marker. Quantitative analyses, using Abeta sandwich ELISA, showed significantly increased intracellular Abeta. False positive detection of Abeta by antibody cross-reaction with APP was ruled out by extracting the fraction with formic acid and making it alkaline before subjecting it to ELISA. This procedure resulted in a fraction that contained little APP. Using CHO cells, OA treatment was also shown to be effective in increasing Abeta, as demonstrated by Western blot. The increased full-length APP and decreased APPC99 were also observed. This is the first study to demonstrate that OA treatment significantly increases intracellular Abeta. 相似文献
110.
Teresa Cabrera Maria Angustias Fernandez Angels Sierra Antonio Garrido Alfonso Herruzo Agustin Escobedo Angels Fabra Federico Garrido 《Human immunology》1996,50(2):127-134
We studied 105 tumor samples obtained from patients diagnosed as having breast carcinomas for HLA class I and II (DR) antigen expression, using a panel of mAbs defining HLA-monomorphic, locus-specific and allele-specific determinants. Peripheral blood lymphocytes from patients were also typed for HLA alleles. The results indicated total HLA class I losses in 55 patients (52.3%), HLA-A locus losses in four patients (3.8%), HLA-B locus losses in eight patients (7.6%), and A, B, locus losses in 10 patients (9.5%). The remaining 28 patients whose tissues reacted positively with monomorphic- and locus-specific mAbs were tested for HLA allelic losses using several anti-HLA mAbs defining A2, A3, A9, B8, B12, etc. Of these 28 patients, 16 (57%) showed one or more losses of HLA reactivity. These results indicated that in 88.5% of patients we detected a particular HLA-altered tumor phenotype. The downregulation of HLA class I antigens in breast carcinomas may thus be more frequent than previously reported, and patients without HLA class I downregulation may be the exception rather than the rule. It cannot be ruled out that HLA alterations are present in some of the 12 patients with an apparently normal HLA phenotype, as some HLA alleles could not be studied because of the lack of appropriate mAbs. These HLA alterations could represent an important step associated with tumor invasion, conferring to the tumor cells the ability to escape from T-lymphocyte recognition. 相似文献