全文获取类型
收费全文 | 19704篇 |
免费 | 1337篇 |
国内免费 | 135篇 |
专业分类
耳鼻咽喉 | 180篇 |
儿科学 | 499篇 |
妇产科学 | 394篇 |
基础医学 | 2199篇 |
口腔科学 | 349篇 |
临床医学 | 1652篇 |
内科学 | 4025篇 |
皮肤病学 | 240篇 |
神经病学 | 1040篇 |
特种医学 | 602篇 |
外科学 | 3482篇 |
综合类 | 967篇 |
一般理论 | 17篇 |
预防医学 | 1528篇 |
眼科学 | 511篇 |
药学 | 1949篇 |
2篇 | |
中国医学 | 293篇 |
肿瘤学 | 1247篇 |
出版年
2023年 | 175篇 |
2022年 | 542篇 |
2021年 | 690篇 |
2020年 | 451篇 |
2019年 | 540篇 |
2018年 | 653篇 |
2017年 | 474篇 |
2016年 | 382篇 |
2015年 | 573篇 |
2014年 | 741篇 |
2013年 | 943篇 |
2012年 | 1391篇 |
2011年 | 1379篇 |
2010年 | 827篇 |
2009年 | 652篇 |
2008年 | 1056篇 |
2007年 | 1043篇 |
2006年 | 974篇 |
2005年 | 909篇 |
2004年 | 800篇 |
2003年 | 729篇 |
2002年 | 615篇 |
2001年 | 561篇 |
2000年 | 503篇 |
1999年 | 407篇 |
1998年 | 164篇 |
1997年 | 129篇 |
1996年 | 122篇 |
1995年 | 127篇 |
1994年 | 67篇 |
1993年 | 91篇 |
1992年 | 206篇 |
1991年 | 187篇 |
1990年 | 166篇 |
1989年 | 178篇 |
1988年 | 140篇 |
1987年 | 157篇 |
1986年 | 133篇 |
1985年 | 136篇 |
1984年 | 113篇 |
1983年 | 90篇 |
1982年 | 64篇 |
1981年 | 63篇 |
1979年 | 97篇 |
1978年 | 67篇 |
1977年 | 69篇 |
1976年 | 53篇 |
1975年 | 63篇 |
1974年 | 51篇 |
1973年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
101.
Novel proteins with binding specificity for DNA CTG repeats and RNA CUG repeats: implications for myotonic dystrophy 总被引:7,自引:6,他引:7
While an unstable CTG triplet repeat expansion is responsible for myotonic
dystrophy, the mechanism whereby this genetic defect induces the disease
remains unknown. To detect proteins binding to CTG triplet repeats, we
performed bandshift analysis using as probes double- stranded DNA fragments
having CTG repeats [ds(CTG)6-10] and single- stranded oligonucleotides
having CTG repeats ss(CTG)8 or RNA CUG triplet repeats (CUG)8. The source
of protein was nuclear and cytoplasmic extracts of HeLa cells, fibroblasts
and myotubes. Proteins binding to the double-stranded DNA repeat
[ds(CTG)6-10], were inhibited by nonlabeled ds(CTG)6-10, but not by a
non-specific DNA fragment (USF/AD-ML). Another protein binding to ssCTG
probe and RNA CUG probe was inhibited by nonlabeled (CTG)8 and (CUG)8.
Nonlabeled oligos with different triplet repeat sequences, ss(CAG)8 or
ss(CGG)8, did not inhibit binding to the ss(CTG)8 probe. However, when
labeled as probes, the (CAG)8 and (CGG)8 bound to proteins distinct from
the CTG proteins and binding was inhibited by nonlabeled (CAG)8 or (CGG)8
respectively. The protein binding only to the RNA repeat (CUG)8 was
inhibited by nonlabeled (CUG)8 but not by nonlabeled single- or
double-stranded CTG repeats. Furthermore, the CUG-BP exhibited no binding
to an RNA oligonucleotide of triplet repeats of the same length but having
a different sequence, CGG. The CUG binding protein was localized to the
cytoplasm, whereas dsDNA binding proteins were localized to the nuclear
extract. Thus, several trinucleotide binding proteins exist and their
specificity is determined by the triplet sequence. The novel protein,
CUG-BP, is particularly interesting since it binds to triplet repeats known
to be present in myotonin protein kinase mRNA which is responsible for
myotonic dystrophy.
相似文献
102.
Khan Z Ferrari G Kasper M Tonge DA Steiner JP Hamilton GS Gordon-Weeks PR 《Neuroscience》2002,114(3):601-609
We used explant cultures of adult mouse dorsal root ganglia with spinal nerve attached growing in Matrigel to assess the effects of the non-immunosuppressive immunophilin ligand GPI-1046 [Snyder et al. (1998) TIPS 19, 21-26] on the growth rate of regenerating sensory axons and found a potent stimulation of axon growth. In these explant cultures, naked, unfasciculated axons emerge from the cut end of the spinal nerve and continue to grow in the Matrigel for up to eight days [Tonge et al. (1996) Neuroscience 73, 541-551]. Some axons are entirely smooth whilst others show prominent varicosities. Some of the former express the phosphorylated neurofilament epitope recognised by monoclonal antibody RT97, a marker for large calibre, myelinated axons, whilst the latter express calcitonin gene-related peptide, predominantly a marker for unmyelinated, and small diameter myelinated sensory axons. Many of the axons in these cultures also express the low-affinity neurotrophin receptor p75. GPI-1046 has been shown to have striking stimulatory effects on embryonic primary sensory axons growing in vitro and it was therefore of interest to see whether it could also enhance regenerating sensory axon growth from the adult ganglia in our cultures. GPI-1046 potently stimulated axon growth in our cultures in a dose-dependent manner. The stimulatory effect was not dependent on the class of sensory axon. These observations show that GPI-1046 is a potent stimulator of regenerating axons from adult, primary sensory neurones. The cellular site of action of GPI-1046 is unknown. To distinguish between a direct effect of the drug on neurones and an indirect effect we compared the effects of GPI-1046 on explant and dissociated cultures. In confirmation of previous results, we found that GPI-1046 potently stimulated axon outgrowth from explants of embryonic chick dorsal root ganglia. However, the drug was without effect on dissociated embryonic dorsal root ganglion neurones, suggesting that non-neuronal cells are important for axon growth stimulation. 相似文献
103.
In the course of our study on Hodgkin's disease (HD), ten cases of non-Hodgkin's lymphomas (NHL) containing Hodgkin and Reed-Sternberg-like (MRS) cells were encountered. Many of these cases had initially been diagnosed as HD, but on careful review of the histology, with the aid of immunophenotyping studies, they were reclassified as NHL. The presence of Epstein–Barr virus (EBV) in these HRS-like cells was investigated using a combination of EBER in situ hybridization (ISH) and immunostaining for the detection of EBV-encoded latent membrane protein (LMP). HRS-like cells in four cases (two lymphoplasmacytoid lymphomas, one Richter's transformation of lymphoplasmacytoid lymphoma, and one immunoblastic lymphoma of T-cell type) were found to be EBV-positive. In two of these cases, a second biopsy taken up to 10 years later also contained EBV in the HRS-like cells. In three of the four cases, HRS-like cells expressed the activation antigen CD30, but the expression of B- or T-cell antigens was variable. All cases of T-cell-rich B-cell lymphomas were negative for EBV. In conclusion, EBV may play a role in the development of HRS-like cells i some cases of NHL. The relationship of HRS-like cells to HRS cells of HD is discussed. 相似文献
104.
Bersinger NA; Brandenberger A; Berger E; Baumann CK; Birkhauser MH 《Human reproduction (Oxford, England)》1998,13(7):1962-1967
We have previously observed the repeated presence of low but detectable
amounts of the trophoblast marker pregnancy-specific beta1-glycoprotein
(SP1) in the serum of some women undergoing in-vitro fertilization (IVF)
treatment around the time of oocyte retrieval. The occurrence of these
signals seemed to be restricted to a defined group of patients which also
showed a lower pregnancy success rate in a preliminary study. To test our
hypothesis we have analysed 173 consecutive cycles leading to an embryo
transfer. Fifty-four cycles (31%) had a serum SP1 level of at least 0.1
ng/ml between days embryo transfer -5 and embryo transfer (group A). Five
pregnancies were obtained in this group (pregnancy rate = 9.3%), while in
group B, defined by the absence of detectable SP1 before embryo transfer
(119 cycles), 36 ongoing pregnancies were achieved (30.3%). Ten of the 41
pregnancies were achieved in 33 first-time non-pregnant patients undergoing
further attempts during the study period. Again the pregnancy rate was
higher in the first-time group B women (9/23 versus 1/10 for group A).
Patients tended to remain in their groups A or B, the latter being
associated with a better immediate as well as subsequent chance for
pregnancy. Group A cycles had a significantly lower endometrial thickness
two days before oocyte retrieval than group B (P = 0.0011). We postulate
that the presence of an unknown, maternal and progesterone- or follicle
stimulating hormone-independent factor in some patients could stimulate
tonic ectopic SP1 synthesis and at the same time negatively influence
endometrial development.
相似文献
105.
Development of a single-tube, cell lysis-based, genus-specific PCR method for rapid identification of mycobacteria: optimization of cell lysis, PCR primers and conditions, and restriction pattern analysis 下载免费PDF全文
A single-tube PCR method was developed for efficient identification of nontuberculous mycobacteria (NTM) and their environmental isolates in about 3 h without conventional DNA isolation. The following three steps were optimized or developed: (i). a simple, 6-min direct cell lysis protocol as a PCR prestep for generation of DNA-template, (ii). an improved Mycobacterium-specific PCR amplification protocol with a broader species specificity using newly designed primers targeting a 228-bp region of the 65-kDa heat shock protein (hsp) gene and optimal PCR amplification conditions, and (iii). a genus-specific restriction analysis of the PCR product for conclusive identification of the unknown NTM isolates. 相似文献
106.
Hantavirus Pulmonary Syndrome: Pathogenesis of an Emerging Infectious Disease 总被引:23,自引:1,他引:23 下载免费PDF全文
Sherif R. Zaki Patricia w. Greer Lisa M. Coffield Cynthia S. Goldsmith Kurt B. Nolte Kathy Foucar Richard M. Feddersen Ross E. Zumwalt Gayle L. Miller Ali S. Khan Pierre E. Rollin Thomas G. Ksiazek Stuart T. Nichol Brian W.J. Mahy Clarence J. Peters 《The American journal of pathology》1995,146(3):552-579
107.
Genotypic analysis of Mycobacterium tuberculosis in Bangladesh and prevalence of the Beijing strain 下载免费PDF全文
Banu S Gordon SV Palmer S Islam MR Ahmed S Alam KM Cole ST Brosch R 《Journal of clinical microbiology》2004,42(2):674-682
Genotypic analysis was performed on 48 Mycobacterium tuberculosis complex strains collected from a hospital in Dhaka city. Deletion analysis showed that the isolates were all M. tuberculosis; 13 of them were found to be of the "ancestral" type, while 35 were of the "modern" type, indicating that both endemic (ancestral type) and epidemic (modern type) strains cause tuberculosis in Bangladesh. Genotyping based on the spoligotype and variable-number tandem repeats (VNTR) of mycobacterial interspersed repetitive units (MIRU) was also done. A total of 34 strains (71%) were grouped by spoligotyping into nine different clusters; the largest comprised 15 isolates of the Beijing genotype, whereas the remaining eight clusters consisted of two to five isolates. MIRU-VNTR typing detected 32 different patterns among 44 tested strains, and the 15 Beijing strains were further discriminated by MIRU-VNTR typing (7 distinct patterns for the 15 isolates). These results indicate that MIRU-VNTR typing, along with spoligotyping and deletion analysis, can be used effectively for molecular epidemiological studies to determine ongoing transmission clusters; to our knowledge, this is the first report about the type of strains prevailing in Bangladesh. 相似文献
108.
Tetanus toxin fragment C expressed in live Salmonella vaccines enhances antibody responses to its fusion partner Schistosoma haematobium glutathione S-transferase 总被引:3,自引:0,他引:3 下载免费PDF全文
Lee JJ Sinha KA Harrison JA de Hormaeche RD Riveau G Pierce RJ Capron A Wilson RA Khan CM 《Infection and immunity》2000,68(5):2503-2512
Tetanus toxoid has been used widely as an adjuvant. The atoxic fragment C from tetanus toxin (TetC) is potently immunogenic when expressed in Salmonella vaccine strains and has been used as a fusion partner for antigens (Ag). However, there has been no formal comparison of the immunomodulatory impact of TetC on its fusion partners. In this study, we have addressed this important issue. The protective 28-kDa glutathione S-transferase (GST) from Schistosoma haematobium (Sh28GST) was expressed either as a fusion to TetC or as the full-length Sh28GST alone in a nonvirulent aroA-attenuated strain of Salmonella enterica serovar Typhimurium. The Sh28GST proteins were soluble and stably expressed in Salmonella, as evaluated by Western blotting with TetC and/or Sh28GST antisera. Mice were immunized orally with a single dose of the live recombinant Salmonella. The constructs were stable in mice but, dramatically, only the strain expressing the TetC-Sh28GST fusion elicited significant antibody (Ab) responses directed against Sh28GST as determined by enzyme-linked immunosorbent assay. An analysis of the isotype profiles showed that these mice also produced anti-Sh28GST immunoglobulin A and GST-neutralizing assays revealed high levels of neutralizing Abs in sera. These are important correlates of protection in schistosomiasis. In addition, stimulation of spleen cells from immunized mice with Sh28GST Ag showed that both strains, expressing Sh28GST alone or the TetC-Sh28GST fusion, were able to stimulate the secretion of Th1-related cytokines (gamma interferon and interleukin 2) to comparable levels. Thus, TetC has modulated the immune responses generated against its fusion partner, Sh28GST, by markedly enhancing the Ab responses elicited. These results have important implications in the rational development of live vaccines. 相似文献
109.
110.
Z U Khan M D Richardson D W Warnock 《International archives of allergy and applied immunology》1984,73(3):205-211
A range of 6 somatic and culture filtrate antigens of Aspergillus fumigatus were evaluated in a rapid ELISA procedure for anti-A. fumigatus IgG where the component incubation times had been reduced to 10 min. Sera from patients with allergic aspergillosis, patients with suspected allergic aspergillosis, and asthmatic patients with or without A. fumigatus precipitins were tested. For all antigens, levels of anti-A. fumigatus IgG were higher in patients with allergic aspergillosis than in the other 3 groups. Low levels of specific IgG were, however, detected in asthmatic patients who had no precipitins against A. fumigatus. None of the antigen preparations enabled all patients with proven or suspected allergic aspergillosis to be separated from the other 2 groups of asthmatic patients. Positive-negative discrimination in ELISA was achieved by the inclusion of 10 pools of precipitin test-negative sera from the 50 asthmatics without A. fumigatus precipitins. The number of sera that were classed as positive in ELISA ranged from 9 to 15 in the allergic aspergillosis group, depending on the antigen used; in the suspected aspergillosis group, the number of positive reactions ranged from 1 to 8, while in the asthmatics with precipitins, the number ranged from 0 to 2. 相似文献