全文获取类型
收费全文 | 108015篇 |
免费 | 6064篇 |
国内免费 | 654篇 |
专业分类
耳鼻咽喉 | 1067篇 |
儿科学 | 3517篇 |
妇产科学 | 2470篇 |
基础医学 | 15506篇 |
口腔科学 | 3932篇 |
临床医学 | 9785篇 |
内科学 | 24284篇 |
皮肤病学 | 2731篇 |
神经病学 | 10541篇 |
特种医学 | 2515篇 |
外国民族医学 | 1篇 |
外科学 | 9693篇 |
综合类 | 395篇 |
一般理论 | 48篇 |
预防医学 | 10768篇 |
眼科学 | 1771篇 |
药学 | 7556篇 |
中国医学 | 417篇 |
肿瘤学 | 7736篇 |
出版年
2024年 | 122篇 |
2023年 | 1043篇 |
2022年 | 2228篇 |
2021年 | 3693篇 |
2020年 | 2309篇 |
2019年 | 3112篇 |
2018年 | 3529篇 |
2017年 | 2686篇 |
2016年 | 3127篇 |
2015年 | 3469篇 |
2014年 | 4544篇 |
2013年 | 5934篇 |
2012年 | 9016篇 |
2011年 | 9382篇 |
2010年 | 5116篇 |
2009年 | 4311篇 |
2008年 | 7442篇 |
2007年 | 7430篇 |
2006年 | 6846篇 |
2005年 | 6391篇 |
2004年 | 5734篇 |
2003年 | 5103篇 |
2002年 | 4594篇 |
2001年 | 543篇 |
2000年 | 382篇 |
1999年 | 591篇 |
1998年 | 794篇 |
1997年 | 646篇 |
1996年 | 548篇 |
1995年 | 451篇 |
1994年 | 430篇 |
1993年 | 356篇 |
1992年 | 289篇 |
1991年 | 190篇 |
1990年 | 195篇 |
1989年 | 180篇 |
1988年 | 174篇 |
1987年 | 141篇 |
1986年 | 158篇 |
1985年 | 110篇 |
1984年 | 132篇 |
1983年 | 128篇 |
1982年 | 157篇 |
1981年 | 117篇 |
1980年 | 123篇 |
1979年 | 73篇 |
1978年 | 80篇 |
1977年 | 72篇 |
1976年 | 59篇 |
1974年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Rosangela Saga Kamikawa Marlene Fenyo Pereira Angela Fernandes Maria Inês Meurer 《Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics》2006,101(3):374-378
OBJECTIVE: To determine the location in soft tissues of the calcifications, similar to calcified carotid atheromas, that can be observed radiographically in the cervical region in panoramic radiographs. STUDY DESIGN: In each anatomic cadaver specimen preserved in formol, consisting of the head and neck, radiopaque spheres (made from gutta-percha) were positioned in anatomic structures of the cervical region that can be sites of calcification. For each anatomic structure marked in this way, panoramic radiography was performed, consisting of 17 radiographs. The images obtained were analyzed by 24 examiners who indicated which radiographs, in their opinion, presented the radiopaque reference projected in the region of bifurcation of the carotid artery. Analysis of 2 proportions from agreement and disagreement was used to determine radiopacities that could be confused in panoramic radiographs with calcified atheromas in the carotid artery. RESULTS: The results showed that 75% (18) of the examiners correctly indicated the reference in the bifurcation of the carotid artery and 79.2% (19) indicated a triticeous cartilage as calcified atheroma of the carotid artery. CONCLUSIONS: Calcified atheromas of the carotid artery are not the only features that can produce radiopaque images lateral to the panoramic radiograph; the presence of calcification in the triticeous cartilage also can induce an erroneous diagnosis of calcified carotid atheroma. 相似文献
103.
Maria G. Genkova-Papazova Maria B. Lazarova-Bakarova 《European neuropsychopharmacology》1996,6(4):285-290
Deficit in active and inhibitory avoidance behaviour has been found in pentylenetetrazole (PTZ)-kindled rats. This supports the view that memory deficit is an integral part of epilepsy. In the present study we examined the effect of the nootropic drugs piracetam and fipexide on memory deficit induced by PTZ-kindling in shuttle-box- and step-down-trained rats. The retention in piracetam- and fipexide-treated animals was significantly improved compared to the kindled controls. The mechanisms of action of the two drugs are considered. The favourable effects of nootropic drugs in cases of amnesia provoked by PTZ-kindling might be of interest in clinical practice. 相似文献
104.
105.
Maria Pia Francescato P. Cok O. Radillo B. de Bernard 《Journal of human nutrition and dietetics》1988,1(5):321-327
A computer-assisted method for the registration of food intakes in real time according to a concise and simple procedure was subjected to a series of controls in order to assess precision. The method employs the 'portion' of a composite dish as unit of measure. The constancy of the portion was tested. The results show that the recipes of the diet of a subject may be stored and utilized in deferred time without loss of precision: data to be recorded in real time are then very limited. The length of period of analysis was also studied. The time of investigation should not be shorter than two weeks to obtain precise information on the feeding habits of an individual subject, whereas for a group of subjects the diary of a single day provides information of sufficient precision. 相似文献
106.
Nicoletta Desideri Isabella Sestili Maria Luisa Stein Stefano Manarini Giuseppe Dell'Elba Chiara Cerletti 《Archiv der Pharmazie》1997,330(4):100-106
6-[(4-Quinolinyl)oxy]hexanoic acids and the corresponding esters were designed and synthesized as inhibitors of the production of arachidonic acid metabolites. The inhibitory activities were assayed in vitro by evaluation of serum leukotriene B4 and thromboxane B2 production. While all 6-[(4-quinolinyl)oxy]hexanoic acids and their esters proved to be inactive, the N-alkyl-4-quinolones, obtained as by-products in their synthesis, were found to be a new class of leukotriene biosynthesis inhibitors. 相似文献
107.
108.
Mark L. Laudenslager Maria L. Boccia Christy L. Berger Mary M. Gennaro-Ruggles Britta McFerran Martin L. Reite 《Developmental psychobiology》1995,28(4):199-211
Many behavioral, immunological, and physiological consequences of brief maternal separation in bonnet (Macaca radiata) and pigtail monkeys (Macaca nemistrina) have been documented. However, the impact of social separation on plasma cortisol and growth hormone is unknown for these particular species. In the present study, the behavioral and endocrinological consequences of a 2-week maternal separation in socially housed infant bonnet and pigtail monkeys were followed. In seven pairs (separated and matched control) of bonnet and six pairs of pigtail infants, plasma was obtained under baseline, separated, and reunion conditions twice weekly for the duration of the study. Blood samples were obtained from both infants of the pair in approximately 10 min. Plasma total cortisol, free cortisol, and growth hormone were measured in these samples. Focal animal behavioral observations were made on all subjects twice daily throughout the study period. In both species, total cortisol and free cortisol rose immediately following maternal separation in comparison to the matched nonseparated controls and returned to basal levels (e.g., that of matched non-separted controls) following reunion with the mother. In contrast, plasma growth hormone rose only in the pigtail infants over a time course that peaked around the time of reunion. Multiple regression techniques indicated for the first week of separation, in the separated but not control subjects, that mean plasma free and total cortisol was positively related to distress behaviors (vocalization and postural slouch) observed during this week and negatively related to social behaviors (play and proximity to others) noted during the same period. In contrast, plasma growth hormone was related to both species and sex of the subjects but unrelated to behavioral variables. © 1995 John Wiley & Sons, Inc. 相似文献
109.
Basilio Pispisa Mariano Venanzi Antonio Palleschi Maria D'Alagni 《Macromolecular chemistry and physics.》1995,196(9):2809-2825
The photophysics of protoporphyrin-naphthyl (P-N) pairs covalently and randomly bound to the ε-amino groups of the side-chains of poly(L -lysine) (PL) were investigated by steady-state and time-resolved fluorescence measurements. The results indicate that quenching of excited naphthalene (λex = 280 nm) chiefly occurs by interconversion to the triplet state when the polymeric matrix is in random coil (pH ≈ 7) and by intramolecular electron transfer from ground-state porphyrin, P → 1N*, when the polypeptide is in α-helical conformation (pH ≈ 11), the specific rate constant of the electron transfer being 3,1 · 107 s?1 (25°C). PNPL exhibits very little exciplex fluorescence, whatever the pH, suggesting both a reduced internal Brownian motion of the chromophores, owing to the amide bond in the substituted side-chains, and a relatively large average interprobe separation distance. This agrees with polarized fluorescence data and with the results of a conformational statistics analysis on the fully ordered PNPL, indicating that the average interchromophoric distance for which the electron transfer has the highest probability to occur is around 12 Å. The computational results allowed us to reproduce the experimental fluorescence decay curves and estimate the parameters governing the electron transfer process. Implications of these findings on the relaxation time of the heli-xcoil transition in PNPL are briefly discussed. 相似文献
110.
Dario Roccatello Marco Formica Guido Cavalli Maria C. Amprimo Maria G. Pignatelli Paolo Costa Ruggero de Paulis Giacomo Quattrocchio rea Molino Gianbeppe Giordano 《Artificial organs》1990,14(1):69-72
Neutrophil oxidative metabolism, C3d and beta 2 microglobulin levels, were assessed in nine consecutive patients undergoing cardiopulmonary bypass surgery with polypropylene hollow fiber oxygenators for open cardiac operations. Generation of oxygen free radicals by neutrophils was measured as luminol-enhanced chemiluminescence after stimulation with opsonized Zymosan and phorbol myristate acetate. A significant increase in light emission was detected by using both of the chemiluminescence stimulators. Moreover, a remarkable and significant increase in C3d levels was found already at 10 min. Conversely minimal changes in levels of beta 2 microglobulin were detected during cardiopulmonary bypass surgery. These data suggest that the impact of the patient blood with the foreign surface of cardiopulmonary bypass results in activation of phagocyte cells with increased potential in oxygen consumption. These effects could be partially complement-mediated. 相似文献