全文获取类型
收费全文 | 9736篇 |
免费 | 471篇 |
国内免费 | 46篇 |
专业分类
耳鼻咽喉 | 130篇 |
儿科学 | 232篇 |
妇产科学 | 161篇 |
基础医学 | 1249篇 |
口腔科学 | 591篇 |
临床医学 | 891篇 |
内科学 | 1837篇 |
皮肤病学 | 314篇 |
神经病学 | 732篇 |
特种医学 | 259篇 |
外科学 | 806篇 |
综合类 | 41篇 |
一般理论 | 6篇 |
预防医学 | 1178篇 |
眼科学 | 217篇 |
药学 | 641篇 |
中国医学 | 56篇 |
肿瘤学 | 912篇 |
出版年
2023年 | 68篇 |
2022年 | 108篇 |
2021年 | 233篇 |
2020年 | 154篇 |
2019年 | 207篇 |
2018年 | 229篇 |
2017年 | 170篇 |
2016年 | 253篇 |
2015年 | 278篇 |
2014年 | 354篇 |
2013年 | 481篇 |
2012年 | 727篇 |
2011年 | 884篇 |
2010年 | 462篇 |
2009年 | 383篇 |
2008年 | 598篇 |
2007年 | 708篇 |
2006年 | 646篇 |
2005年 | 600篇 |
2004年 | 530篇 |
2003年 | 459篇 |
2002年 | 422篇 |
2001年 | 116篇 |
2000年 | 97篇 |
1999年 | 115篇 |
1998年 | 75篇 |
1997年 | 63篇 |
1996年 | 52篇 |
1995年 | 42篇 |
1994年 | 48篇 |
1993年 | 44篇 |
1992年 | 50篇 |
1991年 | 65篇 |
1990年 | 71篇 |
1989年 | 52篇 |
1988年 | 37篇 |
1987年 | 53篇 |
1986年 | 48篇 |
1985年 | 39篇 |
1984年 | 31篇 |
1983年 | 32篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1979年 | 22篇 |
1977年 | 14篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1971年 | 10篇 |
1969年 | 8篇 |
1968年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
It is well known that lung cancer develops frequently in patients with idiopathic interstitial pneumonia (IIP) (9.8-22.8%). We investigated 4 patients who developed lung cancer among the 28 patients with IIP (14.3%) who were admitted to our hospital from June 1981 to March 1989. Many reports have pointed out the clinical features of lung cancer associated with IIP as male sex, old age, heavy smoking, and poor prognosis. Our 4 series were agreed with these clinical features. Lung cancer associated with IIP have been often reported to occur in the lower and peripheral regions of the lung, and honeycomb structures are frequently seen. But we found that lung cancer in IIP could actually occur in both the lower and upper regions of the lung and does not occur only in the honeycomb structures. There was no obvious dominance of any histological type among the tumors. If lung cancer is suspected in a patient with IIP, tumor markers are of some value for diagnosis, but are not sensitive enough to be used alone. 相似文献
32.
D. L. Tolbert M. Ewald J. Gutting M. C. La Regina 《The Journal of comparative neurology》1995,355(4):490-507
Temporal-spatial patterns of surviving Purkinje cells were studied quantitatively in a rat mutant (shaker) with differential hereditary cerebellar ataxia and Purkinje cell degeneration. Shaker rat mutants are characterized behaviorally as mild if they are ataxic or as strong if they have ataxia and tremor. Purkinje cells degenerate in both mild and strong shaker mutants, but the temporal and spatial patterns of cell death are strikingly different. In mild shaker mutants, Purkinje cell death is temporally restricted, with 31-46% of the Purkinje cells in lobules I-IX dying by 3 months of age. Very few Purkinje cells degenerate after this age. Purkinje cell death is spatially random. In lobules I-IX, every second, third, or fourth Purkinje cell degenerates. Purkinje cells in lobule X do not degenerate. In strong shaker mutants, Purkinje cell degeneration is temporally protracted and spatially restricted. By 3 months of age, most Purkinje cells in lobules I-VIa, -b, and -d, and -d have degenerated. Numerous Purkinje cells in the paravermis of lobules VIIb-VIII have also degenerated. Surviving Purkinje cells in the vermis and lateral hemisphere of lobules VIIb-VIII are aligned in parasagittally oriented stripes or transversely oriented bands. Purkinje cells continue to degenerate in localized areas of the posterior lobe such that, by 18 months of age, surviving Purkinje cells are limited primarily to lobules VIc, VIIa, IXd, and X. Quantitative analysis indicates that none of the Purkinje cells in these lobules degenerate. 相似文献
33.
Wagner Jurgen; Madry Henning; Reszka Regina 《Nephrology, dialysis, transplantation》1995,10(10):1801-1807
Renal gene transfer techniques are being developed as a novelexperimental approach to understand the pathogenesis of renaldisease and to potentially develop new therapeutic tools. Wereview the currently available technology to introduce foreigngenetic material into renal tissue, i.e., retroviral, adenoviral,and liposomal transfer systems with their respective advantagesand caveats. Today, the transfer efficiency of these methodsappears to be sufficiently high to study the effects of transducedgenes on renal function and morphology in rat kidney. This willallow (i) the elucidation of the function of genes on the courseof renal disease in experimental animal models and (ii) themodulation of local expression of endogenous genes which presumptivelycontribute to renal pathology in these models. One strategyto accomplish this aim is the use of recombinant DNA technologyto design antisense DNA constructs or oligonucleotides, whichinterfere with the renal expression of target genes. We willalso discuss some of the shortcomings of the currently usedtechniques with respect to potential therapeutic use of genetransfer systems and gene modulation. 相似文献
34.
Quantitation of protein adducts as a marker of genotoxic exposure: immunologic detection of benzo(a)pyrene -- globin adducts in mice 总被引:1,自引:0,他引:1
Immunologic methods have been developed for the determinationof benzo(a)pyrene (BP)-protein adducts and validated in animalstreated with (3H)BP. A previously developed antibody, 8E11,which recongnizes 7ß, 8-dihydroxy-9, 10-epoxy-7, 8,9, 10tetrahydrobenzo(a)pyrene (BPDE-I)-modified DNA or proteinas well as BPDE-I- tetraols, was used. The sensitivity of theassay was increased by enzymatic digestion of the modified proteinwith insoluble protease into peptides and amino acids beforeanalysis. In a competitive enzymelinked immunosorbent assay(ELISA) with digested BPDE-I-modified bovine serum albumin,50% inhibition occured at 400 fmol of adduct compared to 1450fmol for the nondigested albumin. Analysis of globin (Gb) isolatedfrom animals treated in vivo with 0.33 mg (3H)BP indicatedthat the ELISA could detect 90100% of the adducts determinedby radioactivity. Levels of adducts in lung and liver DNA andserum albumin were correlated with the levels of Gb adducts.Of the total radioactivity associated with hemoglobin, only10% was from Gb while {small tilde}80% was from the heme fractionand the remainder from free BP metabolites. Significant cross-reactivityof antibody 8E11 was found with several BP-diols and phenols,suggesting that the immunoassay will not only be specific forBPDE-I adducts but will also detect adducts of other BP metabolitesas well as other aromatic hydrocarbon diol epoxides. An immunoaffinitycolumn of antibody 8E11 coupled to Sepharose 4B was used toisolate modified peptides from the digested Gb. About 65% ofthe applied radioactivity was retained on the column. Between1 and 2 mg of non-modified digested Gb could be added to thesample without interfering with binding of adducts. Proteindigestion and immunoaffinity chromatography should be usefulfor the measurement of protein adducts in biomonitoring studies. 相似文献
35.
Mechanisms of cell adhesion and extracellular matrix formation are primary processes in the interaction with the material surface of an implant which are controlled by integrin receptors. The aim of our study was to find out whether beta1- and beta3-integrins of osteoblastic cells sense the surface topography of titanium, and if structural alterations of integrin adhesions were involved in the organization of fibronectin. Pure titanium surfaces were modified by polishing (P), machining (NT), blasting with glass spheres (GB), and blasting with corundum particles (CB) resulting in increasing roughness. Confocal microscopic investigations revealed fibrillar adhesions of beta1- and alpha5-integrins on P, NT, and GB, but on CB with its sharp edges these integrin subunits did not form fibrillar adhesions. beta3 generally appeared in focal adhesions. We observed aligned fibrillar structures of fibronectin on NT not only on the basal site but interestingly, also on the apical cell surface. In contrast, on CB, fibronectin appeared apically clustered. We suggest that this alignment of fibronectin fibrils depends on the directed actin cytoskeleton and in particular, on the capability of the beta1-integrins to form fibrillar adhesions, which is affected by the surface roughness of titanium. 相似文献
36.
Comparison of Track XI fluorometric immunoassay with Bio-EnzaBead enzyme-linked immunosorbent assay for detection of serum antibody to mouse hepatitis virus. 下载免费PDF全文
M C La Regina J Lonigro L Woods W C Hall R E Doyle 《Journal of clinical microbiology》1988,26(3):573-575
The Track XI system (Microbiological Associates, Bethesda, Md.) was compared with the Bio-EnzaBead assay (Organon Teknika, Durham, N.C.) for the detection of antibody to mouse hepatitis virus (MHV). Strain A/J mice were inoculated intranasally with MHV type 3. Sera were collected at 1, 2, 4, and 9 weeks postinoculation and tested. Individual serum samples were retested twice by each method. The results suggested that the Track XI system was more sensitive and reliable than the Bio-EnzaBead assay in detecting antibody to MHV type 3 in individual serum samples from A/J mice. 相似文献
37.
A. Sunami Z. Fan F. Nakamura M. Naka T. Tanaka T. Sawanobori M. Hiraoka 《Pflügers Archiv : European journal of physiology》1991,419(3-4):415-417
We investigated the effects of the purified catalytic subunit (C subunit) of the cAMP-dependent protein kinase (A-kinase) on the cardiac Na+ channel currents. Single Na+ channel currents in guinea-pig ventricular myocytes were recorded using the patch clamp technique of the inside-out configuration. Application of C subunit decreased the peak average current and slowed the current decay, effects which were caused by decrease in the open probability of Na+ channels and increase in the first latency, whereas the unitary current amplitude and mean open times were not affected. We conclude that the cardiac Na+ channel is directly modulated by phosphorylation process through A-kinase. 相似文献
38.
The renal pelvis of the rat is characterized by extensions called specialized fornices that penetrate into the outer zone of the outer medulla (a type II as classified by Pfeiffer, 1968, 1970). The renal pelvic epithelium, therefore, covers areas of the kidney from the inner medulla, the inner and outer stripe of the outer medulla, and the cortex. The renal pelves of seven rats were studied by transmission and scanning electron microscopy. The transitional epithelium on the nonparenchymal surface of the pelvis was three to four cell layers thick (zone 0–1). This epithelium became thinner where it covered the renal cortex (zone 1–2) or the outer medulla. Although the apical cells of the epithelium retained the asymmetric luminal unit-membrane plaques, the number of cytoplasmic fusiform vesicles decreased as one studied the epithelium progressing over the zones from cortex toward papilla. Scanning electron microscopy demonstrated a small number of surface cells of a different morphology that were characterized by apical microvilli. The number of these microvillous lining cells increased as the epithelium covering the outer (zone 2–3) and inner (zone 3–4) stripe regions of the outer medulla was viewed, until the inner medulla was entirely covered by this cell type. In a reciprocal manner, the cells with the asymmetric apical plaques decreased in numbers and in their morphologic specialization in each successive region. The epithelium surrounding the inner medulla (zone 6–7) was completely devoid of this transitional cell type. Judging from the morphologic characteristics of the epithelia, one could surmise that little exchange of urea, water, and salts would occur with the extrarenal connective tissue or the cortical parenchyma. Recycling of urea might become more important physiologically with the outer stripe parenchyma, and even more so with the increased surfaces of the inner stripe parenchyma that lined the secondary pyramid, as well as with the epithelium lining the inner medulla. 相似文献
39.
Teles SA Martins RM Gomes SA Gaspar AM Araujo NM Souza KP Carneiro MA Yoshida CF 《Journal of medical virology》2002,68(1):41-49
A serological and molecular study of hepatitis B virus (HBV) infection was carried out in dialysis units in Central Brazil. Between 1995 and 1999, serum samples from all HBsAg-positive hemodialysis patients (n = 43) were tested for HBeAg/anti-HBe and subtyping by monoclonal ELISA. HBV DNA was detected by PCR and positive samples were genotyped by restriction fragment polymorphism pattern (RFLP) methodology. TheHBsAg prevalence declined in this population during the survey period (12-5.8%). HBeAg and anti-HBe were detected in 23 (53.5%) and 18 (41.9%) sera, respectively. Thirty-six samples could be HBsAg subtyped: 21 were subtype ayw(3), 14 belonged to adw(2) and one was identified as adw(4). HBV DNA was present in 30 serum samples. Of these, 20 (66.7%) were genotype D, 9 (30%) genotype A, and 1 (3.3%) genotype F. In addition, the RFLP pattern could be determined in samples from 18/20 genotype D patients: D3 (10 strains), D7 (7 strains) and D4 (1 strain); from 8/9 genotype A patients: A1 (6 strains) and A3 (2 strains); and from the patient infected with genotype F: F1. Patterns D3 and D7 were associated closely with HBV infection in the two largest hemodialysis units studied. These findings confirm the value of the RFLP method as an effective molecular epidemiological tool for elucidating HBV transmission in hemodialysis units. 相似文献
40.
Regina Raz Kam Cheung Leona Ling David E. Levy 《Somatic Cell and Molecular Genetics》1995,21(2):139-145
The species specificity of interferons (IFNs) depends on restricted recognition of these ligands by multisubunit cell surface receptors. Expression of the human receptor subunit IFNAR in mouse cells conferred sensitivity only to one subtype of human IFN, IFN-B. Other genes on human chromosome 21 were required for responses to other subtypes of type I IFN. In contrast, IFNAR expression in hamster cells did not confer sensitivity to any human IFN tested, including IFN-B. Using human-hamster somatic cell hybrids, we mapped theIfnabr gene, encoding a ligand-binding subunit of the IFN-/ (type I) receptor, to human chromosome 21.Ifnabr colocalized withIfnar to the distal region of q22.1. The presence of a chromosomal fragment encoding IFNABR and IFNAR was also not sufficient to confer sensitivity to human IFN. In contrast, hybrids carrying in addition the region 21q22.2 showed a full response to human IFN-B, suggesting that a gene located in this region encodes a third factor required for type I IFN receptor activity. 相似文献