全文获取类型
收费全文 | 11690篇 |
免费 | 855篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 124篇 |
儿科学 | 314篇 |
妇产科学 | 189篇 |
基础医学 | 1312篇 |
口腔科学 | 312篇 |
临床医学 | 1212篇 |
内科学 | 2111篇 |
皮肤病学 | 119篇 |
神经病学 | 936篇 |
特种医学 | 809篇 |
外科学 | 2051篇 |
综合类 | 168篇 |
一般理论 | 5篇 |
预防医学 | 1066篇 |
眼科学 | 170篇 |
药学 | 933篇 |
1篇 | |
中国医学 | 6篇 |
肿瘤学 | 736篇 |
出版年
2022年 | 137篇 |
2021年 | 266篇 |
2020年 | 165篇 |
2019年 | 245篇 |
2018年 | 303篇 |
2017年 | 244篇 |
2016年 | 247篇 |
2015年 | 296篇 |
2014年 | 431篇 |
2013年 | 553篇 |
2012年 | 843篇 |
2011年 | 760篇 |
2010年 | 449篇 |
2009年 | 391篇 |
2008年 | 592篇 |
2007年 | 648篇 |
2006年 | 574篇 |
2005年 | 601篇 |
2004年 | 536篇 |
2003年 | 520篇 |
2002年 | 435篇 |
2001年 | 145篇 |
2000年 | 125篇 |
1999年 | 168篇 |
1998年 | 165篇 |
1997年 | 147篇 |
1996年 | 144篇 |
1995年 | 120篇 |
1994年 | 91篇 |
1993年 | 111篇 |
1992年 | 88篇 |
1991年 | 89篇 |
1990年 | 104篇 |
1989年 | 125篇 |
1988年 | 109篇 |
1987年 | 109篇 |
1986年 | 117篇 |
1985年 | 123篇 |
1984年 | 116篇 |
1983年 | 93篇 |
1982年 | 74篇 |
1981年 | 89篇 |
1980年 | 80篇 |
1979年 | 58篇 |
1978年 | 81篇 |
1977年 | 74篇 |
1976年 | 79篇 |
1975年 | 58篇 |
1974年 | 56篇 |
1973年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Ross BD; Jacobson S; Villamil F; Korula J; Kreis R; Ernst T; Shonk T; Moats RA 《Radiology》1994,193(2):457
42.
43.
Pippa Storey Fred J Frigo R Scott Hinks Bryan J Mock Bruce D Collick Nicole Baker Jonathan Marmurek Simon J Graham 《Magnetic resonance in medicine》2007,57(3):614-619
Partial k-space sampling is frequently used in single-shot diffusion-weighted echo-planar imaging (DW-EPI) to reduce the TE and thereby improve the SNR. However, it increases the sensitivity of the technique to bulk rotational motion, which introduces a phase gradient across the tissue that shifts the echo in k-space. If the echo is displaced into the high spatial frequencies, conventional homodyne reconstruction fails, causing intensity oscillations across the image. Zero-padding, on the other hand, compromises the image resolution and may cause truncation artifacts. We present an adaptive version of the homodyne algorithm that detects the location of the echo in k-space and adjusts the center and width of the homodyne filters accordingly. The adaptive algorithm produces artifact-free images when the echo is shifted into the high positive k-space range, and reduces to the standard homodyne algorithm in the absence of bulk motion. 相似文献
44.
Characterization of RAFTK, a novel focal adhesion kinase, and its integrin-dependent phosphorylation and activation in megakaryocytes 总被引:19,自引:3,他引:16
We have recently isolated a cDNA encoding a novel human intracellular tyrosine kinase, termed RAFTK (for a related adhesion focal tyrosine kinase). The RAFTK cDNA, which encodes a polypeptide of 1,009 amino acids, shares 65% homology to the focal adhesion kinase (FAK), including several consensus motifs. In this report, we describe the biochemical characterization and functional analysis of the RAFTK protein. Coexpression of RAFTK and FAK proteins in megakaryocytic cells and blood platelets was observed. Using a specific antibody to RAFTK and the monoclonal antibody 2A7 to FAK, FAK and RAFTK could be distinguished antigenically. RAFTK had intrinsic tyrosine kinase and autokinase activities. It was phosphorylated on tyrosine in growing cultures of COS cells transfected with the pCDNAIII/flag-RAFTK expression vector containing the RAFTK cDNA ligated with the 8 amino acid flag peptide sequence. Similar to FAK, dephosphorylation of RAFTK was observed when adherent transfected COS cells were detached. Phosphorylation was regained upon replating of these cells on the fibronectincoated dishes. Analysis of tyrosine-phosphorylated RAFTK from adherent transfected COS cells showed that the Src homology 2 (SH2) domains of the Src and Fyn protein kinases as well as the Grb2 adaptor protein were able to specifically associate with RAFTK. Tyrosine phosphorylation of endogenous RAFTK was observed upon fibronectin-induced activation of human megakaryocytic cells. Furthermore, colocalization of RAFTK protein with vinculin, a focal adhesion protein, was observed by confocal microscopy in focal adhesion- like structures in adherent CMK cells and in transfected pCDNAIII/flag- RAFTK COS cells upon fibronectin activation. These data suggest that RAFTK is a novel member of the FAK family, that it localizes to focal adhesion-like structures in CMK megakaryocytic cells, that it participates in integrinmediated signaling pathways in megakaryocytes, and that it is able to associate with the tyrosine kinases Src and Fyn as well as the adaptor protein Grb2 via SH2-phosphotyrosine interactions. 相似文献
45.
Physico-chemical characterisation of rinderpest virus 总被引:1,自引:0,他引:1
Rinderpest virus grown in Vero cells was purified by equilibrium sedimentation in potassium tartrate gradients. The characteristics of the virus and its RNA dependend on the passage history of the virus. Undiluted passage virus had a density ofc 1.21 g/ml in potassium tartrate and contained RNA sedimenting atc. 20S and 5S. Virus obtained by dilute passage had a density ofc. 1.24 g/ml and contained 50S in addition to 20S and 5S RNA. Both diluted passage and undiluted passage viruses contained polypeptides with molecular weights of 98, 79, 75, 66, 48, 43 and 37×103. Trace amounts of polypeptides with molecular weights of 29 and 20×103 were also detected. The molecular weights of the major polypeptides are similar to those of the polypeptides present in measles and canine distemper viruses. 相似文献
46.
Lillington DM Kingston JE Coen PG Price E Hungerford J Domizio P Young BD Onadim Z 《Genes, chromosomes & cancer》2003,36(2):121-128
Forty-nine primary retinoblastoma (Rb) tumors were analyzed by the use of comparative genomic hybridization (CGH), and clinical/histological correlations were performed. Adverse histological factors were present in 13 patients. Chromosomal imbalance was a frequent phenomenon, seen in 96% of the tumors. Gain of 6p represented the most frequent event (69% of the tumors), whereas +1q was observed in 57%, confirming that these abnormalities are key secondary events in retinoblastoma tumor progression. Loss of 13q and 16 was significantly associated with tumors displaying adverse histo-prognostic factors, whereas -16q was significantly associated with tumors without adverse features. In three patients who developed an extra-ocular relapse, the tumors showed -13q and 2/3 had -5q, suggesting that these abnormalities may be associated with metastasis. Children >or= 36 months of age at enucleation tended to have more CGH abnormalities per tumor than children < 12 months (median numbers 11 vs. 3). In addition, +1q, +13q, -16, and -16q were more frequent in children with an older age at enucleation. Identical CGH changes were found in both tumors from one patient with bilateral tumors, suggesting a common origin. It is possible that tumors displaying loss of 13q and 5q indicate those patients who may suffer an adverse outcome and who would require alternative or more intensive therapy. CGH analysis on larger cohorts and in prospective clinical trials will be invaluable in determining whether a genetic classification of retinoblastoma represents a reliable measure of prognosis. 相似文献
47.
L Corey W E Stamm P M Feorino J A Bryan S Weseley M B Gregg K Solangi 《The New England journal of medicine》1975,293(25):1273-1278
Eleven of 40 patients in a hemodialysis unit had clinical or biochemical evidence of hepatitis during a five-week period. The clinical disease was mild, being limited solely to dialysis patients. Epidemiologic investigation indicated that the incubation period was between 17 and 35 days and that 10 of 11 patients had been exposed to a single venous-pressure monitor before onset. Dried blood and evidence of blood reflux up the venous-pressure gauge suggested that cross-contamination of the blood of successive patients probably resulted in transmission of disease. No association with the hepatitis B surface antigen or anti-hepatitis B antibody was demonstrated, but 10 of the 11 patients with elevated transaminase levels had evidence of recent exposure, to Epstein-Barr virus as manifested either by Ox-cell hemolysin titers or rises in titers to viral capsid antigen. 相似文献
48.
Savoie FH Wilkinson MM Bryan A Barrett GR Shelton WR Manning JO 《Journal of Athletic Training》1992,27(3):268-269
Ligamentous injuries of the ankle are usually benign and may be managed satisfactorily by nonoperative measures. This is not true, however, of the Maisonneuve variant. In this paper we present a case report of a high school athlete who sustained a Maisonneuve fracture dislocation of the ankle. The diagnosis was missed initially, because of an incomplete examination. The subsequent physical and radiographic examination revealed the proper diagnosis. Guidelines for the evaluation and appropriate treatment are discussed. 相似文献
49.
Polyclonal antiserum to an Escherichia coli-produced beta-galactosidase/E4 fusion protein of human papillomavirus type 6b (antiserum 256), and affinity purified HPV 11 anti-E4 antibodies were tested for reactivity in Western blots with bacterially expressed trpE/E4 fusion proteins of HPV types 6b, 11, 16, and 18. To further characterize the affinity purified anti-E4 antibodies, a dot-immunobinding assay was performed using overlapping synthetic HPV 11 E1E4 peptides as antigens. Protein extracts of condylomata acuminatum from 18 patients containing HPV type 6 or 11 DNA sequences were tested in Western blots using antiserum 256 or affinity purified HPV 11 anti-E4 antibodies. In the Western blots of the trpE proteins, antiserum 256 identified the HPV types 6b and 11 fusion proteins; the affinity purified HPV 11 anti-E4 antibodies identified only the HPV 11 fusion protein. In the dot-immunobinding assay, three HPV 11 peptides were recognized, each containing a shared 8 amino acid sequence that differs significantly from the corresponding sequences of HPV types 6b, 16, or 18. In the Western blots of protein extracts from 18 condylomata acuminatum samples shown to contain HPV types 6 or 11 DNA, putative E4 gene products were identified in six samples by antiserum 256. The affinity purified HPV 11 anti-E4 antibodies identified putative E4 gene products in one of these same six lesions, which was shown to contain HPV 11 sequences by the Southern blot method. All six samples containing E4 gene products were from women. Three of these women were pregnant, one had serum antibodies to the human immunodeficiency virus, and one was a renal transplant recipient receiving glucocorticoids.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
50.