全文获取类型
收费全文 | 28669篇 |
免费 | 1592篇 |
国内免费 | 260篇 |
专业分类
耳鼻咽喉 | 246篇 |
儿科学 | 550篇 |
妇产科学 | 591篇 |
基础医学 | 2954篇 |
口腔科学 | 698篇 |
临床医学 | 2050篇 |
内科学 | 8216篇 |
皮肤病学 | 361篇 |
神经病学 | 2516篇 |
特种医学 | 1086篇 |
外科学 | 5265篇 |
综合类 | 59篇 |
一般理论 | 5篇 |
预防医学 | 1121篇 |
眼科学 | 547篇 |
药学 | 1687篇 |
中国医学 | 57篇 |
肿瘤学 | 2512篇 |
出版年
2024年 | 32篇 |
2023年 | 296篇 |
2022年 | 610篇 |
2021年 | 1043篇 |
2020年 | 593篇 |
2019年 | 847篇 |
2018年 | 1010篇 |
2017年 | 735篇 |
2016年 | 896篇 |
2015年 | 915篇 |
2014年 | 1238篇 |
2013年 | 1525篇 |
2012年 | 2306篇 |
2011年 | 2202篇 |
2010年 | 1269篇 |
2009年 | 1217篇 |
2008年 | 1903篇 |
2007年 | 1843篇 |
2006年 | 1740篇 |
2005年 | 1719篇 |
2004年 | 1609篇 |
2003年 | 1386篇 |
2002年 | 1244篇 |
2001年 | 163篇 |
2000年 | 156篇 |
1999年 | 195篇 |
1998年 | 212篇 |
1997年 | 175篇 |
1996年 | 162篇 |
1995年 | 161篇 |
1994年 | 133篇 |
1993年 | 124篇 |
1992年 | 104篇 |
1991年 | 79篇 |
1990年 | 73篇 |
1989年 | 61篇 |
1988年 | 46篇 |
1987年 | 42篇 |
1986年 | 52篇 |
1985年 | 44篇 |
1984年 | 44篇 |
1983年 | 36篇 |
1982年 | 51篇 |
1981年 | 30篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1966年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Giovanni Scambia MD Elvira Foti MD Gabriella Ferrrandina MD Francesco P. Leone MD Angiolo Gadducci MD Pierluigi Benedetti-Panici MD Salvatore Mancuso MD 《American journal of obstetrics and gynecology》1996,175(6):1606-1610
OBJECTIVE: Our purpose was to investigate immunosuppressive acidic protein in the prognostic characterization of advanced ovarian cancer. STUDY DESIGN: Serum levels of immunosuppressive protein were prospectively measured in 80 patients with untreated ovarian carcinoma. To evaluate the prognostic significance of immunosuppressive acidic protein levels, cutoff points were studied every 50 μg/ml between 450 and 1350 μg/ml. RESULTS: Pretreatment immunosuppressive acidic protein levels were not significantly associated with stage, histotype, grade of differentiation, postoperative residual tumor, and response to chemotherapy. The most significant association with survival was observed at a cutoff value of 1100 μg/ml (p = 0.0089). In the univariate analysis for overall survival, International Federation of Gynecology and Obstetrics stage and immunosuppressive acidic protein status were found to have a role in predicting ovarian cancer prognosis. In the multivariate analysis only immunosuppressive acidic protein status was significantly associated with survival. A statistical correlation was found between serum levels and overall survival (p = 0.0104, χ2 6.56), including immunosuppressive acidic protein as a continuous variable. CONCLUSION: Our data suggest that immunosuppressive acidic protein assay is a potentially useful tool in the prognostic characterization of advanced ovarian cancer. (Am J Obstet Gynecol 1996;175:1606-10.) 相似文献
52.
Vittorio Petraccone Finizia Auriemma Francesco Dal Poggetto Claudio De Rosa Gaetano Guerra Paolo Corradini 《Macromolecular chemistry and physics.》1993,194(5):1335-1345
In this contribution, the X-ray diffraction (XRD) pattern of a highly oriented sample of syndiotactic polystyrene in the mesomorphic form, collected by an automatic diffractometer, is presented, thus providing quantitative and more complete information relative to the diffracted intensity. The structural changes induced by annealing procedures in mesomorphic samples are shown through the analysis of the XRD patterns: both unoriented and oriented mesomorphic samples are transformed gradually into α-form crystals. On the basis of these evidences and of preliminary comparisons between the calculated Fourier transform of simplified models and the experimental diffraction intensity, it is suggested that the local organization in triplets of trans-planar chains, typical of the different modifications of the α-form, would be largely present also in the disordered chain agglomerates of the mesomorphic form. 相似文献
53.
Gaetano Guerra Francesco Dal Poggetto Mauro Iuliano Carla Manfredi 《Macromolecular chemistry and physics.》1992,193(9):2413-2420
Infrared spectra of syndiotactic poly(p-methylstyrene) (s-PPMS) samples, exhibiting various crystalline forms and clathrate structures, are reported in this contribution. Bands due to the syndiotactic stereostructure, bands typical of the two different chain conformations observed in the crystalline structures and bands sensitive to intermolecular interactions typical of the different modes of packing of chains are pointed out. The observed similarities with the case of syndiotactic polystyrene are alos indicated. A complete assignment, via FTIR analysis, of the chain conformations, is presented for all the known crystalline forms and clathrates of s-PPMS. 相似文献
54.
J. Herreros E. Marti B. Ruiz-Montasell A. Casanova H. Niemann J. Blasi 《The European journal of neuroscience》1997,9(12):2677-2686
Clostridial neurotoxins (tetanus and botulinum toxins) are potent blockers of neurotransmitter release. These toxins act specifically on the nervous system by interacting with still non-identified protein receptors together with gangliosides. Whereas many biochemical data are available on their binding properties to neuronal membranes in vitro , there is poor morphological evidence of their binding to mammalian central nervous system. In the present study, the binding of tetanus and botulinum neurotoxin type A to rat brain sections is reported. Both toxins bound to nerve terminals with a broad distribution in brain. Tetanus toxin additionally bound to nerve fibres. The staining patterns were clearly shown to be due to the interaction of the heavy chains, which contain the binding moiety, with the tissue. In an attempt to investigate the nature of the acceptors present in the tissue, some sections were pre-incubated with periodic acid. This treatment resulted in the additional binding of botulinum neurotoxin type A to nerve fibres. Since the extended staining of nerve terminals was not modified by this pretreatment, it is suggested that protein receptors of clostridial neurotoxins are located at the nerve terminals, which may be common constituents of the synapses. 相似文献
55.
Francesco Castelli Bice Conti Davide Maccarrone Olga La Camera Ubaldo Conte 《Drug delivery》1997,4(4):273-279
A comparative study of indomethacin controlled release from poly(lactide-co-glycolide) (50:50, molecular weight 3000) (PLGA) microspheres loaded with two different amounts of drug (10.9 ± 1%, and 34.1 ± 1% w/w) and pure free indomethacin, considering the effects exerted by the drug on the thermotropic behavior of dipalmitoylphosphatidylcholine multilamellar vesicles, was carried out by differential scanning calorimetry (DSC). The release was monitored by comparing the effect exerted by the free indomethacin on lipid thermotropic behavior with that of the drug released by the microspheres and relating these effects to a lipid aqueous dispersion containing the molar ratio of drug able to cause it. By DSC measurements, the pure free indomethacin was found to be able to have a fluidifying effect on the model membrane, causing a shift toward lower values of the transitional temperature (Tm), characteristic of phospholipid liposomes, without variations in the enthalpic changes (ΔH). This shift was found to be modulated by the drug molar fraction with respect to the lipid concentration in the aqueous dispersion. Successively, calorimetric measurements were performed on suspensions of blank liposomes added to weighed amounts of unloaded and indometha-cin-loaded microspheres as well as free powdered indomethacin, and the Tm shifts of the lipid bilayer caused by the drug released from the polymeric system, as well as by the free drug, were compared with that caused by free drug increasing molar fractions dispersed directly on the membrane, employed as a calibration curve to obtain the fraction of drug released. This drug release model could be employed to determine the different kinetics involved in the drug transfer from the microspheres to a membrane. This in vitro study suggests that the kinetic process involved in drug release is influenced by the amount of drug loaded in the microspheres. This calorimetric study shows that the PLGA microspheres are a good delivery system able to sustain drug release. Moreover, the DSC technique applied to the drug interaction with biomembranes constitutes a good tool for determining the drug release representing an innovative alternative in vitro model. 相似文献
56.
Onelio Geatti Brahm Shapiro Pier Giuseppe Orsolon Gianni Proto Ugo Paolo Guerra Francesco Antonucci Daniele Gasparini 《European journal of nuclear medicine and molecular imaging》1994,21(1):17-22
Technetium-99m methoxyisobutylisonitrile (MIBI), like thallium-201, has recently been introduced as a myocardial perfusion agent and is now also showing very promising results in parathyroid scintigrapy. The results of 201Tl/99mTc-pertechnetate and 99mTc-MIBI/99mTc-pertechnetate subtraction scintigraphy, ultrasonography and computed tomography are presented in a series of 43 patients operated on for hyperparathyroidism. All four imaging modalities were confirmed to be reliable, scintigraphy being the most accurate. Sensitivities ranged from 81% to 95%, that of 99mTc-MIBI being the highest. Moreover this tracer, which has more favourable physical and also biochemical properties, yielded images of superior quality. This allowed localization of the lesion by visual inspection only in as many as 86% of the patients with positive 99mTc-MIBI/99mTc-pertechnetate subtraction scintigraphy. We believe that the higher sensitivity, superior image quality and lower cost of 99mTc-MIBI imaging will make 99mTc-MIBI the new radiopharmaceutical of choice for parathyroid scintigraphy (when one takes into account the stability of labelling with large activities it is possible to perform three or four cardiac studies together with one parathyroid scintigraphic examination using one lyophililzed vial). 相似文献
57.
Myocardial protection in adult cardiac surgery: current options and future challenges 总被引:3,自引:0,他引:3
Francesco Nicolini Cesare Beghi Claudio Muscari Andrea Agostinelli Alessandro Maria Budillon Igino Spaggiari Tiziano Gherli 《European journal of cardio-thoracic surgery》2003,24(6):986-993
Current techniques of myocardial protection are evolving with the use of less conventional modalities of cardioplegia and have reduced the morbidity and mortality of cardiac operations. Blood cardioplegic solutions appear superior to cold cardioplegia in terms of myocardial protection and adjuncts as glutamate/aspartate enhancement, antioxidant supplementation, nitric oxide donors and maintenance of calcium homeostasis seem effective. In the near future, further experimental and clinical investigations about pharmacological preconditioning, sodium–hydrogen exchangers inhibition and gene therapy need to be addressed to well define their potential role in the improvement of current techniques of myocardial protection that are suboptimal in high-risk clinical settings. 相似文献
58.
Francesco Franceschi Umile Giuseppe Longo Laura Ruzzini Paolo Simoni Bruno Beomonte Zobel Vincenzo Denaro 《Knee surgery, sports traumatology, arthroscopy》2007,15(3):266-268
Bilateral discoid medial menisci is an extremely rare condition of the knee and it can be associated to other pathological
findings, including anterior portion cyst formation. We report on the clinical features, radiographic findings, treatment
and results of one patient who presented a bilateral medial discoid meniscus combined with posterior portion cyst of the left
knee. To the best of the author’s knowledge, this is the first case of bilateral medial discoid meniscus associated with posterior
portion cyst formation. 相似文献
59.
Antonio Gigante Claudia Bevilacqua Massimo G. Bonetti Francesco Greco 《Acta orthopaedica》2003,74(4):431-436
We studied the relationship between Osgood-Schlatter disease and torsional abnormalities of the lower limb in 21 boys with this condition and 20 age- and sex-matched controls. 3 groups of knees (20 control knees, 21 symptomatic and 21 asymptomatic or less symptomatic knees) were subjected to clinical, radiographic and CT evaluation. We found no statistically significant differences between patients and controls, as regards femoral anteversion, patellar congruence angle, patellar tilt angle and anterior tibial tuberosity-trochlear groove distance, but the condylomalleolar angle and tibial torsion angle were greater in patients. We found no differences between symptomatic and asymptomatic or less symptomatic knees in any of the parameters. All the symptomatic knees were on the side preferentially involved in jumping and sprinting. This increase in external tibial torsion may play a role as a predisposing mechanical factor in the onset of Osgood-Schlatter disease in male athletes. 相似文献
60.
Francesco Botr 《Toxicology in vitro》2003,17(5-6):509-513
A particular field of analytical chemistry applied to forensic toxicology is represented by the anti-doping analysis, where biological samples (urine and in some instances blood) collected, either “in competition” or “out of competition”, from athletes ruled for national/international sport federations, are analyzed to detect the putative use of prohibited substances and methods. Together with the official anti-doping activity to test the athletes (i.e. who engages in competitive sport) for the non-physiological enhancement of sport performance, it is mandatory to activate a new strategy of doping control, that should necessarily comprise a deep and exhaustive toxicological evaluation of the entire spectrum of doping substances and methods. An outline of the present status and of the future trends of the antidoping research is here presented, showing that most of the new tasks could greatly benefit from an approach based on in vitro methods, ranging from specific toxicity studies to the possible detection of new forms of doping. 相似文献