全文获取类型
收费全文 | 13887篇 |
免费 | 772篇 |
国内免费 | 116篇 |
专业分类
耳鼻咽喉 | 153篇 |
儿科学 | 336篇 |
妇产科学 | 380篇 |
基础医学 | 1886篇 |
口腔科学 | 315篇 |
临床医学 | 1380篇 |
内科学 | 2868篇 |
皮肤病学 | 524篇 |
神经病学 | 844篇 |
特种医学 | 701篇 |
外科学 | 2220篇 |
综合类 | 162篇 |
现状与发展 | 1篇 |
一般理论 | 2篇 |
预防医学 | 590篇 |
眼科学 | 275篇 |
药学 | 1095篇 |
中国医学 | 150篇 |
肿瘤学 | 893篇 |
出版年
2023年 | 90篇 |
2022年 | 248篇 |
2021年 | 420篇 |
2020年 | 198篇 |
2019年 | 271篇 |
2018年 | 412篇 |
2017年 | 296篇 |
2016年 | 350篇 |
2015年 | 440篇 |
2014年 | 638篇 |
2013年 | 660篇 |
2012年 | 1040篇 |
2011年 | 1012篇 |
2010年 | 604篇 |
2009年 | 488篇 |
2008年 | 805篇 |
2007年 | 799篇 |
2006年 | 743篇 |
2005年 | 739篇 |
2004年 | 649篇 |
2003年 | 521篇 |
2002年 | 497篇 |
2001年 | 422篇 |
2000年 | 396篇 |
1999年 | 313篇 |
1998年 | 136篇 |
1997年 | 103篇 |
1996年 | 107篇 |
1995年 | 86篇 |
1994年 | 73篇 |
1993年 | 56篇 |
1992年 | 127篇 |
1991年 | 115篇 |
1990年 | 109篇 |
1989年 | 74篇 |
1988年 | 65篇 |
1987年 | 70篇 |
1986年 | 56篇 |
1985年 | 58篇 |
1984年 | 36篇 |
1983年 | 25篇 |
1980年 | 24篇 |
1979年 | 34篇 |
1977年 | 30篇 |
1976年 | 26篇 |
1975年 | 26篇 |
1974年 | 28篇 |
1973年 | 26篇 |
1972年 | 30篇 |
1970年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Alan J.A. McBride Gustavo M. Cerqueira Marc A. Suchard Angela N. Moreira Richard L. Zuerner Mitermayer G. Reis David A. Haake Albert I. Ko Odir A. Dellagostin 《Infection, genetics and evolution》2009,9(2):196-205
Recent serologic, immunoprotection, and pathogenesis studies identified the Lig proteins as key virulence determinants in interactions of leptospiral pathogens with the mammalian host. We examined the sequence variation and recombination patterns of ligA, ligB, and ligC among 10 pathogenic strains from five Leptospira species. All strains were found to have intact ligB genes and genetic drift accounting for most of the ligB genetic diversity observed. The ligA gene was found exclusively in L. interrogans and L. kirschneri strains, and was created from ligB by a two-step partial gene duplication process. The aminoterminal domain of LigB and the LigA paralog were essentially identical (98.5 ± 0.8% mean identity) in strains with both genes. Like ligB, ligC gene variation also followed phylogenetic patterns, suggesting an early gene duplication event. However, ligC is a pseudogene in several strains, suggesting that LigC is not essential for virulence. Two ligB genes and one ligC gene had mosaic compositions and evidence for recombination events between related Leptospira species was also found for some ligA genes. In conclusion, the results presented here indicate that Lig diversity has important ramifications for the selection of Lig polypeptides for use in diagnosis and as vaccine candidates. This sequence information will aid the identification of highly conserved regions within the Lig proteins and improve upon the performance characteristics of the Lig proteins in diagnostic assays and in subunit vaccine formulations with the potential to confer heterologous protection. 相似文献
53.
Y Unlü S Kele? N Becit C U Ko?o?ullari H Ko?ak E Bakan 《European journal of vascular and endovascular surgery》2005,30(3):315-318
OBJECTIVE: Several studies have shown a relation between hyperhomocysteinaemia and vascular disease. To assess the risk of deep-vein thrombosis (DVT) associated with hyperhomocysteinaemia, we studied plasma homocysteine levels in patients with deep-vein thrombosis and in normal control subjects. MATERIALS AND METHODS: We measured plasma homocysteine levels in 48 patients with deep-vein thrombosis and in 33 healthy controls matched to the patients according to age and sex. Plasma homocysteine levels were measured with high performance liquid chromatography and fluorescence detection. Hyperhomocysteinaemia was defined as a plasma homocysteine level about 15 micromol/L in both groups. The diagnosis of all patients with deep-vein thrombosis (n=48) was verified by Doppler ultrasonography. RESULTS: Plasma homocysteine levels were found to be increased in the deep-vein thrombosis group compared the control group (p<0.001, t-test). The mean plasma homocysteine level in the patients was 17.1 SD 5.13 micromol/L (range 6.4-31.3), and that in the controls was 9.0 SD 1.27 micromol/L (range 6.0-11.5). The association between elevated homocysteine levels and venous thrombosis was stronger among men than among women. CONCLUSIONS: The increased plasma homocysteine levels we have observed may have a causative role in the development of deep-vein thrombosis. 相似文献
54.
Mahmut Koç Ömer Yoldaş Yusuf Alper Kılıç Erdal Göçmen Tamer Ertan Hayrettin Dizen Mesut Tez 《Langenbeck's archives of surgery / Deutsche Gesellschaft fur Chirurgie》2007,392(5):581-585
Background and aims The aim of this study is to evaluate the predictive accuracy of different scoring systems on surgery for perforated peptic
ulcer referred to an academic department of general surgery in a tertiary reference center.
Patients and methods Seventy-five consecutive patients (Male/female ratio = 64:11; mean age, 44 years; range, 16–85) with perforated peptic ulcer
disease were investigated. Disease severity scores and mortality predictions were calculated using the collected data during
admission. Discrimination and calibration characteristics of each system, namely, the acute physiology and chronic health
evaluation II and III, the simplified acute physiology score II, and the mortality probability models (MPM) II, were determined
by using the area under receiver operating characteristics curve and the Hosmer–Lemeshow goodness-of-fit test, respectively.
Results Among the 75 patients included, there were eight (10.6%) mortalities. All systems had a reliable power of discrimination and
calibration. Among the systems tested, MPM II was the best performing as far as discrimination and calibration characteristics
were considered. The parameters of MPM II system that were related to systemic perfusion of the patient were significantly
positive in patients who died compared to those who survived.
Conclusions MPM II that predicted mortality at admission is better than the other systems in predicting mortality. Results also indicate
the importance of maintenance of systemic perfusion of the patient at the early phases of peptic ulcer perforation. 相似文献
55.
56.
Kaan Kirali Nihan Kayalar Tuncer Ko?ak Cevat Yakut 《European journal of cardio-thoracic surgery》2005,27(5):923-924
Many approaches for minimally invasive coronary bypass surgery are available and to further decrease the invasiveness, coronary artery bypass grafting has been performed under high thoracic epidural anesthesia without endotracheal intubation in the last years. Less invasive approach to coronary artery bypass graft operations is possible through combination of the high thoracic epidural anesthesia and a reversed-J sternotomy, and coronary revascularization can be accomplished without any additional technical difficulties and with a good exposure of both the left anterior descending artery and the left internal thoracic artery. This technique is less traumatic for patients and provides practical better oxygenation and shorter hospital stay. 相似文献
57.
Chien-Huang Lin Feng-Nien Ko Hisahi Ishii Tsutomu Ishikawa Ih-Sheng Chen Che-Ming Teng H.-P. Kuo 《Naunyn-Schmiedeberg's archives of pharmacology》1997,355(2):210-216
We investigated the effects of a novel platelet-activating factor (PAF) receptor antagonist, CIS-19 [cis-2-(3, 4-dimethoxyphenyl)-6-isopropoxy-7-methoxy-1-(N-methylformamido)-1,
2, 3, 4-tetrahydronaphthalene], on PAF-, histamine-, substance P- and antigen-induced bronchoconstriction and microvascular
leakage, as well as PAF- and antigen-induced bronchial hyperreactivity to methacholine in urethane-anesthetized guinea-pigs.
Administration of CIS-19 (0.5–5 mg/kg, i.v.) inhibited the increase in lung resistance induced by PAF (30 ng/kg, i.v.) in
a dose-dependent manner, but failed to inhibit the increase induced by histamine (30 μg/kg, i.v.) or substance P (6.5 μg/kg,
i.v.). CIS-19 (5 mg/kg, i.v.) did not inhibit the increase in lung resistance induced by ovalbumin (2 mg/kg, i.v.) in actively
sensitized guinea-pigs. PAF (30 ng/kg, i.v.)-induced microvascular leakage, measured by the extravasation of Evans blue dye,
was dose-dependently inhibited by CIS-19 (0.5–5 mg/kg, i.v.) in the trachea, main bronchi and intrapulmonary airways, but
it did not affect histamine (30 μg/kg, i.v.)- or substance P (6.5 μg/kg, i.v.)-induced microvascular leakage at all airway
levels. CIS-19 (2.5 and 5 mg/kg) did not affect ovalbumin (2 mg/kg, i.v.)-induced microvascular leakage in all airway levels
in actively sensitized guinea-pigs. CIS-19 (2.5 and 5 mg/kg, i.v.) significantly inhibited PAF-induced enhancement of the
bronchial response to methacholine, but had no effect on ovalbumin (0.05 mg/kg, i.v.)-induced bronchial hyperreactivity in
actively sensitized guinea-pigs. It is concluded that CIS-19 is a potent PAF receptor antagonist which inhibits PAF- but not
antigen-induced bronchoconstriction, microvascular leakage and bronchial hyperreactivity. These results suggest that PAF plays
little or no role in early airway responses following antigen challenge.
Received: 29 April 1996 / Accepted: 10 October 1996 相似文献
58.
59.
Although plasma cells are terminally differentiated B cells, neoplastic plasma cells frequently express not only pre-B cell antigen, but also megakaryocytic, myelomonocytic, or erythroid markers. Since morphologic diagnosis of plasmacytoma is based on the recognition of neoplastic cells closely resembling normal plasma cells, unusual morphologic variants of neoplastic cells associated with these aberrant immunohistochemical features frequently cause diagnostic difficulty. The authors report a case of plasmacytoma with cleaved nuclei and myelomonocytic features occurring in the clavicle. The tumor was composed of immature plasma cells showing irregular, cleaved, and multilobated nuclei and abundant cytoplasm with prominent eosinophilic granules. A few tumor cells showing recognizable plasmacytic differentiation were admixed within the tumor. Immunohistochemically, the tumor cells expressed CD45RB, CD68, lysozyme, myeloperoxidase and kappa light chain with focal positivity for lambda chain. Ultrastructurally, the tumor cells contained numerous membrane bound electron dense lysosomal granules, some of them resembling Auer rods, as well as rough endoplasmic reticula arranged in lamellated stacks. Small biopsied nasal mucosal tissue in same patient revealed well differentiated plasmacytoma composed of tumor cells showing round, eccentric nuclei devoid of marked nuclear cleavage and cytoplasmic granularity. Immunohistochemically, these cells were kappa(+), lambda(-), myeloperoxidase(-), lysozyme(-) and CD68(-). 相似文献
60.