全文获取类型
收费全文 | 5030篇 |
免费 | 270篇 |
国内免费 | 10篇 |
学科分类
医药卫生 | 5310篇 |
出版年
2023年 | 17篇 |
2022年 | 37篇 |
2021年 | 83篇 |
2020年 | 45篇 |
2019年 | 70篇 |
2018年 | 94篇 |
2017年 | 53篇 |
2016年 | 108篇 |
2015年 | 120篇 |
2014年 | 147篇 |
2013年 | 196篇 |
2012年 | 325篇 |
2011年 | 391篇 |
2010年 | 195篇 |
2009年 | 184篇 |
2008年 | 336篇 |
2007年 | 318篇 |
2006年 | 334篇 |
2005年 | 334篇 |
2004年 | 294篇 |
2003年 | 257篇 |
2002年 | 285篇 |
2001年 | 51篇 |
2000年 | 32篇 |
1999年 | 71篇 |
1998年 | 89篇 |
1997年 | 77篇 |
1996年 | 58篇 |
1995年 | 49篇 |
1994年 | 45篇 |
1993年 | 44篇 |
1992年 | 37篇 |
1991年 | 25篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 41篇 |
1987年 | 20篇 |
1986年 | 30篇 |
1985年 | 26篇 |
1984年 | 19篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1974年 | 16篇 |
1964年 | 13篇 |
1962年 | 13篇 |
排序方式: 共有5310条查询结果,搜索用时 828 毫秒
41.
42.
Summary Infection of Aedes albopictus cells with Semliki Forest virus (SFV) leads to polykaryocyte formation below pH 6.2. This syncytium formation is accompanied by a decrease of the cellular ATP level. Addition of inhibitors of oxidative phosphorylation leads to a rapid, total depletion of ATP in infected cells at pH 6 and results in an inhibition of polykaryocyte formation. However, when cells were exposed for only a few minutes to pH 6 in the presence of the inhibitors and then kept at pH 7.2, the ATP level partially recovered to values sufficient for syncytium formation. Similar results were obtained after ATP depletion induced by 2-deoxyglucose. Thus, it can be concluded that SFV-induced syncytium formation is an ATP-dependent event.With 6 Figures 相似文献
43.
Pooling of clinical specimens prior to testing for Chlamydia trachomatis by PCR is accurate and cost saving 下载免费PDF全文
Currie MJ McNiven M Yee T Schiemer U Bowden FJ 《Journal of clinical microbiology》2004,42(10):4866-4867
The accuracy and cost savings of pooling specimens prior to testing for Chlamydia trachomatis by PCR were evaluated with genital and urine specimens (n = 2,600). There was a 60% reduction in tests without significant loss of accuracy. The efficiency of pooling vaginal swabs is demonstrated for the first time. 相似文献
44.
Meng S Qiao M Foniok T Tuor UI 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2005,166(1):56-60
We hypothesized that the cerebral injury produced by hypoxia-ischemia (HI) in neonatal rats would differ in white compared with gray matter as detected histologically or with magnetic resonance (MR) imaging methods. Maps of T2 and the apparent diffusion coefficient (ADC) of water were acquired in 1-week-old rats at times prior to cerebral HI (right carotid artery occlusion plus 1.5 h of hypoxia), within the last 5–10 min of HI, and 1 h or 24 h after HI. Near the end of HI, ADC decreased and T2 increased in both cortical gray and subcortical white matter within the cingulum of the HI hemisphere. One hour after HI, ADC partially recovered, but T2 remained increased and then increased further by 24 h post-HI. In contrast to the similar MR responses in white and gray matter, histological evidence for irreversible cell damage occurred in white matter earlier than in gray matter within the HI hemisphere. At 1 h post-HI, rarefied or disrupted nerve fibers and an increase in TUNEL-positive cells were observed within white matter in the cingulum, whereas neurons within the cortical gray matter appeared normal. By 24 h post-HI, damage was apparent in both white and gray matter. Thus, MR imaging detected acute tissue edema following cerebral HI in both gray and white matter but did not distinguish between the early irreversible tissue injury detected histologically in white but not gray matter in this rather severe model of neonatal encephalopathy. 相似文献
45.
Gert Baumann Stephan B. Felix Claus D. Heidecke Gotthard Rieß Ursula Loher Liesel Ludwig Prof. Dr Hans Blömer 《Inflammation research》1984,15(3-4):216-228
Left ventricular infarction (AMI) was produced in experimental animals and the contractile response to -adrenergic and H2-histaminergic stimulation by isoproterenol and impromidine tested in the isolated perfused heart preparation. Adenylate cyclase activity as well as binding characteristics of [3H]-dihydroalprenolol ([3H]-DHA), [3H]-methyl-tiotidine ([3H]-TIOT) and [3H]-quinuclidinyl benzilate ([3H]-QNB) to cardiac
1-, H2- and cholinergic muscarinic receptors were determined in sarcolemmal membrane preparations of the right ventricle of the same hearts. In addition, an attempt was made to elucidate the therapeutic value of post-AMI treatment with impromidine in the presence and absence of-sympathomimetic, in contrast to administration of prenalterol and the conventional therapy with -sympathomimetic drugs, e.g. dobutamine. Three days post-AMI the dose-response curve for isoproterenol of right ventriculardP/dt
max was significantly depressed, while the inotropic effect of impromidine was not impaired. Stimulation of adenylate cyclase activity by isoproterenol was reduced by 80% whereas impromidine and NaF stimulation rates were unaltered. Receptor-binding studies indicated a 90% loss and 10-times lowered affinity (K
D) of the remaining -receptors while specific [3H]-TIOT- and [3H]-QNB-binding was unchanged.Administration of dobutamine increased mortality rates and extension of infarct size, led to a further decrease in contractile response to isoproterenol, induced complete insensitivity of adenylate cyclase to isoproterenol stimulation and caused pronounced additional reduction of number and affinity of [3H]-DHA-binding sites. In contrast, all above alterations were prevented by treatment with either prenalterol or combined administration of impromidine plus metoprolol. It is concluded, that these alterations in the non-ischemic, uninvolved myocardium post-AMI are the result of catecholamine-induced specific damage of sarcolemmal -receptors. Furthermore, treatment with H2-agonists in combination with -blocking agents may have beneficial effects, whereas conventional therapy with -sympathomimetic drugs tends to worsen the already depressed function of the -adrenergic stimulation mechanism.Supported by grants Ba 666/1 and Ba 666/2-2 from the Deutsche Forschungsgemeinschaft (DFG).Data presented in this paper are part of a doctoral thesis by Dr S.B. Felix. 相似文献
46.
Gastrointestinal mesenchymal tumors - immunophenotypic classification and survival analysis 总被引:8,自引:0,他引:8
Rudolph P Chiaravalli AM Pauser U Oschlies I Hillemanns M Gobbo M Marichal M Eusebi V Höfler H Capella C Klöppel G 《Virchows Archiv : an international journal of pathology》2002,441(3):238-248
The current definition of gastrointestinal tumors (GIST) as CD117-positive mesenchymal tumors of uncertain malignant potential fails to include a number of cases with similar histology. In an attempt to improve the classification of these neoplasms, we conducted an immunohistochemical analysis of 244 mesenchymal tumors with histological features of GIST. According to their immunophenotype, the tumors were classified as GISTs, which are characterized by CD117 (c-kit) expression; gastrointestinal CD117-negative CD34 positive stromal tumors (GINST); alpha-smooth muscle actin and/or desmin positive gastrointestinal leiomyogenic tumors (GILT); S-100 and glial fibrillary acidic protein positive gastrointestinal glial/schwannian tumors (GIGT); gastrointestinal neuronal/glial tumors (GINT), which are positive for S-100/glial fibrillary acidic protein plus neuronal/glial markers; and gastrointestinal fibrous tumors (GIFT), which are only vimentin positive. The most common type of tumors were GIST, followed in order of frequency by GINST, GILT, GIGT, GIFT, and GINT. GISTs did not show any preferential location, whereas GINSTs occurred almost exclusively in the stomach and duodenum, and GILTs preferentially in the large intestine. Over a median follow-up period of 71 months, malignant behavior, i.e., metastatic spread, was observed in all tumor types except GINTs. Malignancy was associated with distal gut location, high mitotic activity, large tumor size, and nuclear pleomorphism, though none of these criteria alone discriminated between benign and malignant. Kaplan-Meier analysis of disease-specific survival showed significant differences in the long-term outcome of the newly defined subgroups. We conclude that, despite strong morphological similarities, gastrointestinal mesenchymal tumors are heterogeneous in their immunophenotype and biology. 相似文献
47.
Ursula R. Kees Jette Ford Pamela R. Ranford Susanne E. Peroni Jaclyn A. Biegel Annette H. Parmiter Lavinia A. Hallam Michael L. N. Willoughby Dominic Spagnolo 《Genes, chromosomes & cancer》1994,9(2):129-135
We have established two cell lines, PER-452 and PER-453, from an 8-month-old girl with an extensive pineoblastoma. Characterization of these lines revealed that the proto-oncogenes MYC and MYCN were not amplified, but both cell lines showed MYCN expression comparable to a cell line with 200-fold MYCN amplification. Both cell lines contained an i( 17q). These results support the concept that pineoblastomas belong to a larger group of primitive neuroectodermal tumors of the central nervous system. These two cell lines provide a unique opportunity to investigate the molecular genetic mechanisms underlying these neoplasms further. Genes Chrom Cancer 9:129-135 (1994).© 1994 Wiley-Liss, Inc. 相似文献
48.
Heinritz W Kotzot D Heinze S Kujat A Kleemann WJ Froster UG 《American journal of medical genetics. Part A》2005,(2):198-201
We report on an adult male with Klinefelter phenotype and an isodicentric Y chromosome (47,XX,+idic(Y)(q12)), a combination which has to the best of our knowledge not been reported before. The patient was hospitalized in forensic psychiatry because of repeated delinquency, aggressive, aberrant and inappropriate behavior, and borderline intelligence. Molecular cytogenetic studies (FISH) showed that the SRY gene was present on both ends of the idicY, while there was only one signal for the Yq subtelomere probe. Molecular investigations by multiplex PCR, using STS markers covering the short and long arm of the Y chromosome did not indicate a deletion of Y chromosomal material. Molecular investigations of STR markers located on Xp22.3 and Xq28 indicated paternal origin of the additional X chromosome and an error in paternal meiosis I. Results of FISH analysis and molecular investigations are compatible with a phenotype as described for individuals with a 48,XXYY karyotype and support the findings that isodicentric Y chromosomes are frequently accompanied by other sex chromosomal abnormalities. 相似文献
49.
50.
Dieter Böning Ulrich Tibes Ursula Schweigart 《European journal of applied physiology》1976,35(4):243-249
Summary Red cell concentrations of hemoglobin (MCHC), H+, Na+, K+, Mg++, Cl– were measured in femoral venous blood of six untrained (UT), six endurance trained (TR) and three semitrained (ST) subjects during graded increasing work (4, 8, 12, 18 and 24 mkp/s, 10–15 min on each step) on a bicycle ergometer. Before exercise no significant differences were detected for the measured variables when comparing UT and TR. During exercise MCHC, [Na+], [K+] and [Mg++] remained constant indicating lack of water shift into the erythrocytes in spite of a marked acidosis (lowest pHBlood value 7.225). This lack resulted from an elevated extracellular osmolality. [H+]Ery and [Cl–]Ery maximally increased by 2.0×10–8 eq/kg H2O and 10 meq/l, respectively. The change was markedly greater in UT than in TR at equal load. However, if [H+]Ery and [Cl–]Ery were related to pH of whole blood, differences between groups almost disappeared and the ions were distributed as predictable from in vitro experiments (Fitzsimmons and Sendroy, 1961). Behaviour of H+ and Cl– may be of importance for oxygen dissociation under in vivo conditions.Supported by Bundesinstitut für Sportwissenschaften, Köln 相似文献