全文获取类型
收费全文 | 3753篇 |
免费 | 297篇 |
国内免费 | 67篇 |
专业分类
耳鼻咽喉 | 19篇 |
儿科学 | 137篇 |
妇产科学 | 99篇 |
基础医学 | 490篇 |
口腔科学 | 73篇 |
临床医学 | 487篇 |
内科学 | 562篇 |
皮肤病学 | 77篇 |
神经病学 | 372篇 |
特种医学 | 483篇 |
外国民族医学 | 1篇 |
外科学 | 262篇 |
综合类 | 95篇 |
预防医学 | 290篇 |
眼科学 | 90篇 |
药学 | 430篇 |
中国医学 | 4篇 |
肿瘤学 | 146篇 |
出版年
2021年 | 47篇 |
2018年 | 38篇 |
2017年 | 32篇 |
2016年 | 35篇 |
2015年 | 44篇 |
2014年 | 51篇 |
2013年 | 111篇 |
2012年 | 108篇 |
2011年 | 121篇 |
2010年 | 85篇 |
2009年 | 97篇 |
2008年 | 97篇 |
2007年 | 141篇 |
2006年 | 128篇 |
2005年 | 138篇 |
2004年 | 120篇 |
2003年 | 110篇 |
2002年 | 99篇 |
2001年 | 125篇 |
2000年 | 123篇 |
1999年 | 118篇 |
1998年 | 98篇 |
1997年 | 101篇 |
1996年 | 96篇 |
1995年 | 87篇 |
1994年 | 70篇 |
1993年 | 66篇 |
1992年 | 79篇 |
1991年 | 84篇 |
1990年 | 88篇 |
1989年 | 126篇 |
1988年 | 120篇 |
1987年 | 86篇 |
1986年 | 80篇 |
1985年 | 95篇 |
1984年 | 75篇 |
1983年 | 46篇 |
1982年 | 47篇 |
1981年 | 41篇 |
1980年 | 37篇 |
1979年 | 61篇 |
1978年 | 37篇 |
1977年 | 36篇 |
1976年 | 33篇 |
1975年 | 31篇 |
1974年 | 45篇 |
1972年 | 33篇 |
1970年 | 30篇 |
1968年 | 26篇 |
1966年 | 29篇 |
排序方式: 共有4117条查询结果,搜索用时 15 毫秒
41.
Comparison of isolates of Neisseria gonorrhoeae causing meningitis and report of gonococcal meningitis in a patient with C8 deficiency. 总被引:1,自引:0,他引:1 下载免费PDF全文
C Del Rio D S Stephens J S Knapp R J Rice W O Schalla 《Journal of clinical microbiology》1989,27(5):1045-1049
We studied a previously healthy 20-year-old woman who presented with gonococcal meningitis. The gonococcal isolate, HT-1, was prototrophic by auxotyping, was protein I serovar IB-1, and agglutinated with wheat germ lectin. This isolate differed from the proline-requiring, serovar IA-1 and IB-4, wheat germ-agglutination-negative gonococcal isolates recovered from three patients during a recent outbreak of gonococcal meningitis in Philadelphia. HT-1 was killed by normal pooled human sera (greater than or equal to 98% at 30 min) but not effectively killed by the convalescent-phase sera of the patient (greater than 30% survival at 30 min). Similar results were obtained when mucosal and cerebrospinal fluid isolates from a Philadelphia patient were exposed to these sera, but mucosal and blood isolates from another Philadelphia case showed increased resistance to killing by normal pooled human sera. Further characterization revealed multiple differences in outer membrane and cellular proteins and lipopolysaccharide between case isolates. Absence of the L8 lipopolysaccharide epitope was noted for all isolates. Sera of our patient were found to have low total hemolytic complement (CH100 = 21 U/ml; normal = 55 to 100 U/ml) due to deficiency of C8 (C8 less than 1,000 CH50 U/ml; normal = greater than or equal to 16,000 CH50 U/ml). This is the first reported case of gonococcal meningitis occurring in a patient with a terminal-complement deficiency. Gonococcal meningitis is a rare complication of gonococcal bacteremia. Both defects in host defenses (e.g., terminal-complement deficiency) and organisms with unusual virulence appear to contribute to the pathogenesis of this complication of gonococcal bacteremia. 相似文献
42.
Molecular cloning, genomic structure and localization in a blood stage antigen of Plasmodium falciparum characterized by a serine stretch 总被引:16,自引:0,他引:16
Two short DNA segments were isolated by screening of a lambda gt11 library from Plasmodium falciparum schizont cDNA with an antiserum against the 140 kDa protein, which confers protective immunity to monkeys. The segments were used to identify a genomic fragment which carries the entire coding sequence for a protein of 113 kDa characterized by a stretch of serine residues (SERP I). We present the complete nucleotide and deduced amino acid sequence as well as the structure of the SERP I gene. The gene consists of four exons interrupted by three short introns located at the amino-terminal half. Exon 1 and the first part of exon 2 code for hydrophobic amino acids of a putative signal sequence. Exon 2 contains two repetitive segments, the first encoding six glycine rich octapeptides and a second region coding for 37 consecutive serine residues. Southern blot analysis demonstrated the conservation of the SERP I gene in four different parasite strains. SERP I could be localized in the parasitophorous vacuole and in the surrounding membranes. We discuss the relationship of this protein to the recently described P126 polypeptide and the possible role of this antigen as a vaccine candidate. 相似文献
43.
Analysis of T cell activation with a non-mitogenic anti CD3 antibody and the phorbol ester TPA. 总被引:2,自引:0,他引:2 下载免费PDF全文
We used a non mitogenic anti CD3 antibody, termed VIT3, to study the signals required for the activation of normal resting T lymphocytes. Besides being not mitogenic, this antibody completely inhibits mitogen induced proliferative responses. In the presence of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), however, VIT3 induces DNA replication and cell proliferation comparable to PHA responses. In addition, T cells cultured with VIT3 plus TPA but not with VIT3 or TPA alone express high levels of interleukin 2 (IL-2) receptors and transferrin receptors. This co-stimulation appears to be accessory cell independent. Purified T cells respond equally well to VIT3 plus TPA as do unseparated mononuclear cells and addition of non-T cells has no enhancing effect. We conclude that the IgM antibody VIT3, although non-mitogenic by itself, still delivers a first and for the activation essential signal. In resting T cells this signal does not induce demonstrable anti-Tac antibody binding nor does it lead to a fully developed proliferative response in the presence of recombinant IL-2. Together with a second signal provided by TPA it serves, however, as a potent inducer of T cell growth. 相似文献
44.
Immunosuppressive effects of (2R,5R)-6-heptyne-2,5-diamine an inhibitor of polyamine synthesis: I. Effects on mitogen-induced immunoglobulin production in human cultured lymphocytes. 下载免费PDF全文
J L Pasquali P S Mamont A Weryha A M Knapp A Blervaque M Siat 《Clinical and experimental immunology》1988,72(1):141-144
The consequences of specific inhibition of polyamine biosynthesis by (2R,5R)-6-heptyne-2,5-diamine (MAP) a potent inhibitor of L-ornithine decarboxylase (ODC), on immunoglobulin (Ig) production were studied in cultured human peripheral blood lymphocytes stimulated with pokeweed mitogen (PWM). MAP inhibits the usual PWM-induced increase of polyamine (putrescine, spermidine and spermine) concentrations and reduces concomitantly cell replication. In parallel with these biochemical effects, IgG and IgM production are diminished, a 95% decrease being observed at 100 microM MAP concentration. That the suppressive effects of the ODC inhibitor result from polyamine deficiency, and not from unrelated pharmacological effects, is demonstrated by the restoration of normal Ig production when 10 microM putrescine or spermidine are added to the culture medium. These findings established that the cellular immunological response can be affected by specific inhibition of polyamine biosynthesis and deserve further consideration both under in vitro and in vivo conditions. 相似文献
45.
46.
A new distribution record is established for the tick Ornithodoros kelleyi Cooley & Kohls for Kentucky. Collections of this tick were associated with bat roosting sites in attics of houses. Scanning electron microscopy was used as an aid in distinguishing various taxonomic characteristics and morphological structures of O. kelleyi. 相似文献
47.
Risk of localized and widespread endometrial cancer in relation to recent and discontinued use of conjugated estrogens 总被引:13,自引:0,他引:13
S Shapiro J P Kelly L Rosenberg D W Kaufman S P Helmrich N B Rosenshein J L Lewis R C Knapp P D Stolley D Schottenfeld 《The New England journal of medicine》1985,313(16):969-972
In a case-control study of the risk of adenocarcinoma of the endometrium in relation to conjugated-estrogen use, we found that 31 per cent of 425 women with endometrial cancer and 15 per cent of 792 controls reported having used conjugated estrogens; the rate-ratio estimate was 3.5 with a 95 per cent confidence interval of 2.6 to 4.7. For use that lasted at least one year, the rate-ratio estimate for Stage I or II cancer was 5.2 (95 per cent confidence interval, 3.7 to 7.2), and for Stages III and IV combined it was 3.1 (1.5 to 6.4). Among women who had used estrogen for at least one year and then discontinued it, the risk of endometrial cancer remained significantly elevated even after estrogen-free intervals of over 10 years. The findings suggest that long-term use of conjugated estrogen increases the risk of both localized and widespread endometrial cancer. The data also suggest that women who have taken conjugated estrogen for one or more years remain at increased risk for at least 10 years after they discontinue use. Such women should be considered for long-term gynecologic surveillance. 相似文献
48.
Tyrer P Thompson S Schmidt U Jones V Knapp M Davidson K Catalan J Airlie J Baxter S Byford S Byrne G Cameron S Caplan R Cooper S Ferguson B Freeman C Frost S Godley J Greenshields J Henderson J Holden N Keech P Kim L Logan K Manley C MacLeod A Murphy R Patience L Ramsay L De Munroz S Scott J Seivewright H Sivakumar K Tata P Thornton S Ukoumunne OC Wessely S 《Psychological medicine》2003,33(6):969-976
BACKGROUND: We carried out a large randomized trial of a brief form of cognitive therapy, manual-assisted cognitive behaviour therapy (MACT) versus treatment as usual (TAU) for deliberate self-harm. METHOD: Patients presenting with recurrent deliberate self-harm in five centres were randomized to either MACT or (TAU) and followed up over 1 year. MACT patients received a booklet based on cognitive behaviour therapy (CBT) principles and were offered up to five plus two booster sessions of CBT from a therapist in the first 3 months of the study. Ratings of parasuicide risk, anxiety, depression, social functioning and global function, positive and negative thinking, and quality of life were measured at baseline and after 6 and 12 months. RESULTS: Four hundred and eighty patients were randomized. Sixty per cent of the MACT group had both the booklet and CBT sessions. There were seven suicides, five in the TAU group. The main outcome measure, the proportion of those repeating deliberate self-harm in the 12 months of the study, showed no significant difference between those treated with MACT (39%) and treatment as usual (46%) (OR 0.78, 95% CI 0.53 to 1.14, P=0.20). CONCLUSION: Brief cognitive behaviour therapy is of limited efficacy in reducing self-harm repetition, but the findings taken in conjunctin with the economic evaluation (Byford et al. 2003) indicate superiority of MACT over TAU in terms of cost and effectiveness combined. 相似文献
49.
Neurofibromatosis 2 (NF2) is an inherited cancer syndrome resulting from
mutations in the NF2 tumor suppressor gene. Analysis of NF2 mutations has
revealed some general genotype-phenotype correlations. Severe disease has
been associated with mutations that produce a premature termination while
more mild disease has been associated with missense mutations. Here, we
provide experimental proof for these genotype-phenotype correlations by
demonstrating that nonsense mutations fail to produce stable merlin protein
while missense mutations result in the generation of merlin proteins
defective in negative growth regulation. This inability to suppress cell
growth may result from defects in the function of merlin at several levels,
including failure to form an intramolecular complex. Based on these
findings, we propose a model for merlin growth suppression that provides a
framework for analyzing NF2 patient mutations and merlin function.
相似文献
50.
JS Pooni Dr DWL Hukins PF Harris RC Hilton KE Davies 《Surgical and radiologic anatomy : SRA》1986,8(3):175-182
Posterior and anterior heights, cross-sectional area and shape were measured for all the intervertebral discs in four spines from elderly human cadavers. Disc height was a minimum at the T4-5 level; thoracic discs were less wedge-shaped than those in the cervical and lumbar regions. Cross-sectional area increased from the cranial to caudal extremity; at the L5-S1 level the nucleus pulposus occupied a high proportion of this area. Cervical discs tended to have an elliptical cross-sectional shape, thoracic discs were more circular and lumbar discs tended to have an elliptical cross-section which was flattened or re-entrant posteriorly. This shape distribution was quantified by defining a shape index which had a maximum value of 1 for a circular cross-section. Orientations of the reinforcing fibres in the outer lamellae of the anterior annulus fibrosus were measured from 27 discs by X-ray diffraction. For these measurements, C3-4, T7-8 and L2-3 were chosen as representative of cervical, thoracic and lumbar discs. The fibre tilt, with respect to the axis of the spine, was significantly less in the cervical discs (at 65 degrees) than in the thoracic and lumbar discs (about 70 degrees). These findings are interpreted in relation to differing functional requirements and possible mechanisms of failure in the cervical, thoracic and lumbar regions of the spine in the light of current knowledge on the biomechanics of the intervertebral disc. 相似文献