全文获取类型
收费全文 | 50850篇 |
免费 | 3026篇 |
国内免费 | 246篇 |
专业分类
耳鼻咽喉 | 633篇 |
儿科学 | 1170篇 |
妇产科学 | 1218篇 |
基础医学 | 7055篇 |
口腔科学 | 1500篇 |
临床医学 | 5573篇 |
内科学 | 10971篇 |
皮肤病学 | 797篇 |
神经病学 | 5013篇 |
特种医学 | 1763篇 |
外科学 | 6307篇 |
综合类 | 325篇 |
一般理论 | 44篇 |
预防医学 | 3615篇 |
眼科学 | 805篇 |
药学 | 3442篇 |
1篇 | |
中国医学 | 59篇 |
肿瘤学 | 3831篇 |
出版年
2023年 | 321篇 |
2022年 | 631篇 |
2021年 | 1143篇 |
2020年 | 745篇 |
2019年 | 979篇 |
2018年 | 1194篇 |
2017年 | 1069篇 |
2016年 | 1256篇 |
2015年 | 1311篇 |
2014年 | 1739篇 |
2013年 | 2504篇 |
2012年 | 3791篇 |
2011年 | 3981篇 |
2010年 | 2365篇 |
2009年 | 2155篇 |
2008年 | 3288篇 |
2007年 | 3589篇 |
2006年 | 3203篇 |
2005年 | 3260篇 |
2004年 | 2998篇 |
2003年 | 2796篇 |
2002年 | 2565篇 |
2001年 | 426篇 |
2000年 | 348篇 |
1999年 | 479篇 |
1998年 | 561篇 |
1997年 | 459篇 |
1996年 | 409篇 |
1995年 | 346篇 |
1994年 | 304篇 |
1993年 | 309篇 |
1992年 | 235篇 |
1991年 | 228篇 |
1990年 | 211篇 |
1989年 | 220篇 |
1988年 | 195篇 |
1987年 | 172篇 |
1986年 | 178篇 |
1985年 | 210篇 |
1984年 | 181篇 |
1983年 | 167篇 |
1982年 | 192篇 |
1981年 | 159篇 |
1980年 | 139篇 |
1979年 | 112篇 |
1978年 | 122篇 |
1977年 | 131篇 |
1976年 | 94篇 |
1975年 | 107篇 |
1974年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
91.
Interactions of rutaecarpine alkaloids with specific binding sites for 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat liver 总被引:1,自引:0,他引:1
Gillner Mikael; Bergman Jan; Cambillau Christian; Gustafsson Jan-Ake 《Carcinogenesis》1989,10(4):651-654
Rutaecarpine alkaloids have the capacity to inhibit specific2,3,7,8-[1,6-3H]tetrachlorodibenzo-p-dioxin (TCDD) binding inrat liver cytosol, as analysed by electrofocusing in polyacrylamidegel. The IC50 value for binding of 7,8-dehydrorutaecarpine wasestimated to 7 nM indicating a high-affinity interaction, whereasrutaecarpine appeared less active (IC50 110 nM). These findingsare of interest in view of the fact that analogues to thesecompounds may be formed following UV-irradiation of tryptophanand that such photo-products have been suggested to constitute(the) endogenous ligand(s) for the TCDD receptor. As furthersupport of this notion, the rutaecarpine alkaloids investigatedcould be fitted into a rectangle of 6.8x13.7 A, a characteristiccommon for most high affinity ligands of the TCDD receptor hithertostudied. In view of their structural similarity to dehydrorutaecarpineand the agreement of their mol. wt with that of the photoproductwith the highest affinity for the TCDD receptor, we suggestdeaza-analogues of dehydrorutaecarpine to represent possiblecandidates for the endogenous TCDD receptor ligand. 相似文献
92.
Jan Frisell Gunnar Eklund Lars Hellström Ulla Glas Anders Somell 《Breast cancer research and treatment》1989,13(1):79-87
In screening programmes it is important to assess a preliminary effectiveness of the screening method as soon as possible in order to forecast survival figures. In March 1981 a controlled single-view mammographic screening trial for breast cancer was started in the south of Stockholm. The population invited for screening mammography consisted of 40,000 women aged 40–64 years, and 20,000 women served as a well-defined control group. The main aim of the trial was to determine whether repeated mammographic screening could reduce the mortality in the study population (SP) compared to the control population (CP).The cumulative number of advanced mammary carcinomas in the screening and the control populations from the first five years of screening have shown a tendency towards more favourable stages in the screened population aged 40–64 years. A breakdown by age suggests an effect in age group 50–59 years, but not yet in age groups 40–49 and 60–64 years.When comparing the rates of stage II+ cancer, an increased number is found in the study group. As the total rate of breast cancer is higher in SP than in CP, there ought to be a concealed group of stage II+ cancers in the CP which makes the comparison biased. A new approach has been designed, where an estimation of the hidden number of stage II+ cancers in CP is added to the clinically detected cases, and in this respect a comparison has shown a decrease in the cumulative number of advanced cancers in the SP in relation to the CP (p<0.05). According to this it could be important to add the estimated number of undetected, hidden cases in the control group in order to utilize the difference in detection rate in the screening- and control group respectively. 相似文献
93.
94.
Antilymphocyte serum was prepared in several species and its effect on the production of migration inhibitory factor (MIF) studied. Antilymphocyte sera in vitro in dilutions as high as 1/3200 inhibited the liberation of MIF by sensitized lymphocytes in the presence of antigen. In contrast antipolymorph and antiglobulin sera were inactive.
Antilymphocyte serum also blocked the formation of MIF when the lymphocytes were preincubated with ALS and then washed before the addition of antigen. The antilymphocyte serum and sera prepared against supernatants containing MIF did not block MIF activity by direct neutralization.
相似文献95.
Ruth Tachezy Eva Hamsikova Jaroslav Valvoda Marc Van Ranst Jan Betka Robert D. Burk Vladimir Vonka 《Journal of medical virology》1994,42(1):52-59
Recurrent respiratory papillomatosis (RRP) is the most common benign tumour of the larynx, affecting both children and adults. We present a series of 25 patients, including 10 cases of juvenile multiple, 8 cases of adult solitary, and 7 cases of adult multiple RRP. Biopsy tissue from each patient was screened by Southern blot hybridization and polymerase chain reaction for the presence of human papillomavirus (HPV) DNA. Sera from patients and age- and sex-matched controls were tested for the presence of HPV-specific antibodies using a synthetic pep-tide derived from the minor capsid protein (L2) of HPV 6/11. By Southern blot hybridization and/or polymerase chain reaction, biopsies from all patients were positive for HPV 6/11 DNA. There was no difference in antibody response between cases and controls. Female cases and controls had significantly higher antibody titers than male subjects. A correlation was observed between the HPV-specific antibody level and the number of surgery-necessitating recurrences. © 1994 Wiiey-Liss, Inc. 相似文献
96.
Smits PH Bakker R Jong E Mulder JW Meenhorst PL Kleter B van Doorn LJ Quint WG 《Journal of clinical microbiology》2005,43(12):5936-5939
Infection with human immunodeficiency virus (HIV) and the resulting immunosuppression are associated with an increased risk for human papillomavirus (HPV) persistence and related malignancies. In the present study we investigated the prevalence of HPV in urine samples from 104 HIV-infected men with low CD4+ cell counts (<100 per mm(3)) and 115 urine samples from HIV-negative men. A high prevalence of HPV DNA (39.4%) was found in the HIV patients. Most of the HPV types were high risk (81.4%), with HPV 52 as the most prevalent type (12.5%), followed by HPV 18 (6.7%), HPV 35 (5.8%), and HPV 70 (4.8%). Multiple HPV genotypes were observed in 17 (41%) of the 41 HPV- and HIV-positive men. In contrast, only 11 (9.6%) HPV DNA-positive cases were observed among the 115 HIV-uninfected men, and 3 (27.3%) contained multiple genotypes. Quantitative analyses indicated that the HPV viral load, as measured in urine samples, is significantly higher in HIV-positive men compared to HIV-negative men. In the present study we show that urine samples are useful for detecting HPV DNA, there is a high prevalence of HPV in HIV-positive men, and the HPV viral load is substantially higher in HIV-positive than in HIV-negative men. More studies are needed to evaluate the risk and natural development of HPV-related malignancies in HIV-positive men. 相似文献
97.
Zbigniew Jedliski Marek Kowalczuk Piotr Kurcok Lilianna Brzoskowska Jan Franek 《Macromolecular chemistry and physics.》1987,188(7):1575-1582
The block polymerization of 4-methyl-2-oxetanone (β-butyrolactone) with 2-oxetanone (β-propiolactone) proceeds fast with a yield of more than 90%, in the presence of potassium solutions in THF containing 18-crown-6. Poly(4-methyl-2-oxetanone-block-2-oxetanone) polymers having the expected molecular weight and composition are formed by this way. Their glass transition and melting temperatures as well as their melting enthalpies, determined by DSC, show a strict correlation with block polymer composition. 相似文献
98.
Schouls LM Reulen S Duim B Wagenaar JA Willems RJ Dingle KE Colles FM Van Embden JD 《Journal of clinical microbiology》2003,41(1):15-26
Three molecular typing methods were used to study the relationships among 184 Campylobacter strains isolated from humans, cattle, and chickens. All strains were genotyped by amplified fragment length polymorphism (AFLP) analysis, multilocus sequence typing (MLST), and sequence analysis of a genomic region with short tandem repeats designated clustered regularly interspaced short palindromic repeats (CRISPRs). MLST and AFLP analysis yielded more than 100 different profiles and patterns, respectively. These multiple-locus typing methods resulted in similar genetic clustering, indicating that both are useful in disclosing genetic relationships between Campylobacter jejuni isolates. Group separation analysis of the AFLP analysis and MLST data revealed an unexpected association between cattle and human strains, suggesting a common source of infection. Analysis of the polymorphic CRISPR region carrying short repeats allowed about two-thirds of the typeable strains to be distinguished, similar to AFLP analysis and MLST. The three methods proved to be equally powerful in identifying strains from outbreaks of human campylobacteriosis. Analysis of the MLST data showed that intra- and interspecies recombination occurs frequently and that the role of recombination in sequence variation is 50 times greater than that of mutation. Examination of strains cultured from cecum swabs revealed that individual chickens harbored multiple Campylobacter strain types and that some genotypes were found in more than one chicken. We conclude that typing of Campylobacter strains is useful for identification of outbreaks but is probably not useful for source tracing and global epidemiology because of carriage of strains of multiple types and an extremely high diversity of strains in animals. 相似文献
99.
M B Connolly J E Jan R M Couch L T Wong J E Dimmick J M Rigg 《American journal of medical genetics》1991,40(4):421-424
Alstr?m disease is a rare disorder; less than 20 cases have been reported. An 11-year-old girl is described with this condition. She has pigmentary retinopathy, sensory neural deafness, obesity, Type II diabetes mellitus, hyperlipidemia, and acanthosis nigricans. However, in addition she developed hepatic dysfunction, pathologically similar to chronic active hepatitis. This may be a further, previously undescribed systemic manifestation of Alstr?m disease. 相似文献