全文获取类型
收费全文 | 173495篇 |
免费 | 11161篇 |
国内免费 | 1218篇 |
专业分类
耳鼻咽喉 | 2586篇 |
儿科学 | 3568篇 |
妇产科学 | 4123篇 |
基础医学 | 25519篇 |
口腔科学 | 3736篇 |
临床医学 | 16346篇 |
内科学 | 33088篇 |
皮肤病学 | 4529篇 |
神经病学 | 13337篇 |
特种医学 | 8609篇 |
外科学 | 23235篇 |
综合类 | 2366篇 |
现状与发展 | 5篇 |
一般理论 | 107篇 |
预防医学 | 10696篇 |
眼科学 | 4677篇 |
药学 | 14204篇 |
中国医学 | 1606篇 |
肿瘤学 | 13537篇 |
出版年
2023年 | 1024篇 |
2022年 | 2784篇 |
2021年 | 4957篇 |
2020年 | 2562篇 |
2019年 | 3708篇 |
2018年 | 4577篇 |
2017年 | 3349篇 |
2016年 | 4331篇 |
2015年 | 5768篇 |
2014年 | 7122篇 |
2013年 | 8698篇 |
2012年 | 13103篇 |
2011年 | 12755篇 |
2010年 | 7483篇 |
2009年 | 6323篇 |
2008年 | 9656篇 |
2007年 | 9576篇 |
2006年 | 8849篇 |
2005年 | 8397篇 |
2004年 | 7533篇 |
2003年 | 6563篇 |
2002年 | 5799篇 |
2001年 | 4795篇 |
2000年 | 4440篇 |
1999年 | 3603篇 |
1998年 | 1440篇 |
1997年 | 1098篇 |
1996年 | 1066篇 |
1995年 | 976篇 |
1994年 | 868篇 |
1993年 | 727篇 |
1992年 | 1936篇 |
1991年 | 1942篇 |
1990年 | 1718篇 |
1989年 | 1543篇 |
1988年 | 1474篇 |
1987年 | 1368篇 |
1986年 | 1318篇 |
1985年 | 1168篇 |
1984年 | 829篇 |
1983年 | 746篇 |
1982年 | 513篇 |
1981年 | 487篇 |
1980年 | 431篇 |
1979年 | 716篇 |
1978年 | 580篇 |
1977年 | 511篇 |
1976年 | 442篇 |
1974年 | 485篇 |
1973年 | 453篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
S. H. Pross Y. Nakano S. McHugh R. Widen T. W. Klein H. Friedman 《Immunopharmacology and immunotoxicology》1992,14(3):675-687
Marijuana, and specifically its psychoactive component, THC, can up or down regulate lymphocyte proliferation in murine spleen cells depending in part on the method used to stimulate the cells. This study identifies a difference in THC induced disregulation using cells derived from two different secondary lymphoid organs, the spleen and the lymph node. It was found that THC treatment of mitogen (concanavalin A or phytohemagglutinin) stimulated cells derived from either organ resulted in suppression of the proliferative response. In contrast, spleen cells stimulated with anti-CD3 antibody and treated with low doses of THC displayed an enhanced proliferation whereas the response in lymph nodes did not change. The cell type involved with this THC immunoenhancement in spleen cells was found to be the Ly2 cell. Further differences in the THC modulation of Ly2 spleen cells as compared to lymph node cells were noted following stimulation with PHA. Proliferation of Ly2 cells of splenic origin was inhibited with low doses of THC whereas the Ly2 cells of lymph node origin were more resistant to this drug induced suppression. This study, therefore, demonstrates differences in the immunomodulatory capability of THC dependent upon the organ source of the lymphocytes. 相似文献
72.
A nephritic condition was developed by infecting Swiss Webster albino mice with the malarial parasite Plasmodium berghei NK 65. These animals were tested for urinary protein and the presence of circulating immune complexes using reagent strips and a polyethylene glycol (PEG) precipitation assay. The circulating immune complexes were isolated from the sera using both affinity chromatography and PEG precipitation and from the kidney by acid elution. The isolated complexes were dissociated into their individual components and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The components of the complexes were transferred to nitrocellulose sheets and probed for the presence of malarial antigens using a rabbit anti-P berghei antisera. The overall humoral response to the malarial parasite was evaluated using a radial immunodiffusion assay. The present study confirmed that the malarial-infected animals not only developed the nephritic condition (as evident by the high levels of proteinuria) but also, as indicated by the PEG assay, have the presence of high levels of circulating immune complexes in their serum. The apparent absence in the SDS gels of any abnormal protein bands followed by the inability of the Western blot to reveal any malarial antigens provides some of the strongest evidence to date that these malarial proteins are not directly involved in the circulating immune complexes believed to be responsible for producing this nephritic condition. 相似文献
73.
The standard semen analysis frequently fails to identify subfertile males even when findings are normal and conversely often fails to identify fertile males with subnormal semen analyses. This has created the need to produce other tests of sperm physiology that will better distinguish a fertile from a subfertile specimen. Understanding more about the nature of the sperm defect should lead to the establishment of more specific and effective therapies. Until that time, it would still be reasonable to try some of the available empirical therapies even though they may work merely by a placebo mechanism. 相似文献
74.
Gastrointestinal dysfunction among intensive care unit patients 总被引:3,自引:0,他引:3
This study used the Acute Physiological and Chronic Health Evaluation (APACHE II) system to select two groups of ICU patients with comparable risk of hospital death to evaluate the importance of GI dysfunction, defined as failure to tolerate enteral nutrition (EN), as a prognostic factor. In our ICU, patients who have not undergone recent bowel surgery are treated by EN. Those patients who cannot tolerate EN are treated by total parenteral nutrition (TPN). One hundred and eleven patients who tolerated EN (functioning gut) and 97 TPN patients who failed to tolerate EN (GI dysfunction) were studied. The mean APACHE II scores of the two groups were 17.7 +/- 6.5 (SD) and 17.7 +/- 5.1, respectively. The observed mortality of patients with GI dysfunction (51%) was significantly higher (p less than .0005) than that of patients with a functioning gut (25%). This was associated with significantly poorer APACHE II mean BP, oxygenation, and creatinine scores among the GI dysfunction patients. Our results suggest that shock, ischemia, and hypoxemia, in addition to causing impairment of renal function, may bring about changes in the GI tract, evident clinically only as a failure to tolerate EN, which have an adverse effect on the prognosis of ICU patients so affected. 相似文献
75.
Mark Hereld Rick L Stevens Hyong C Lee Wim van Drongelen 《Journal of clinical neurophysiology》2007,24(2):189-196
SUMMARY: Large simulations have become increasingly complex in many fields, tending to incorporate scale-dependent modeling and algorithms and wide-ranging physical influences. This scale of simulation sophistication has not yet been matched in neuroscience. The authors describe a framework aimed at enabling natural interaction with complex simulations: their configuration, initial conditions, monitoring, and analysis. The architecture is built on three cornerstone components: active probes, adaptive data capture, and visual interface. The resulting synthesis will enable interactive exploration of live simulations running on supercomputing platforms. 相似文献
76.
Jong-Moon Lee Kun-Woo Park Woo-Keun Seo Moon Ho Park Changsu Han Inho Jo Sangmee Ahn Jo 《Movement disorders》2007,22(16):2446-2449
There have been a few studies and inconsistent results regarding the coincidence of Parkinson's disease (PD) and atherosclerotic diseases, such as cerebrovascular disease. Carotid intima-media thickness (IMT) is a known marker for subclinical atherosclerosis. The aim of this study was to investigate the carotid IMT between PD patients and controls. We studied 43 patients with PD and 86 matched controls. The carotid IMT in PD patients was significantly smaller than in controls (0.796 +/- 0.179 mm vs. 0.913 +/- 0.237 mm, P < 0.05). In multivariate analysis, the carotid IMT was inversely associated with the duration of levodopa medication and the severity of PD. These results suggest that PD patients have a lower risk of atherosclerosis. 相似文献
77.
78.
Luis Hernandez-Garcia Gregory R Lee Alberto L Vazquez Chun-Yu Yip Douglas C Noll 《Magnetic resonance in medicine》2005,54(4):955-964
A new approach to modeling the signal observed in arterial spin labeling (ASL) experiments during changing perfusion conditions is presented in this article. The new model uses numerical methods to extend first-order kinetic principles to include the changes in arrival time of the arterial tag that occur during neuronal activation. Estimation of the perfusion function from the ASL signal using this model is also demonstrated. The estimation algorithm uses a roughness penalty as well as prior information. The approach is demonstrated in numerical simulations and human experiments. The approach presented here is particularly suitable for fast ASL acquisition schemes, such as turbo continuous ASL (Turbo-CASL), which allows subtraction pairs to be acquired in less than 3 s but is sensitive to arrival time changes. This modeling approach can also be extended to other acquisition schemes. 相似文献
79.
As an ongoing effort to elucidate the mechanisms involved in the calcium-dependent fertility regulation process, the viscoelastic properties of the mucus obtained from lamb cervix and human semen, as well as their water and total protein contents after exposure to EDTA, a chelating agent, or Nonoxynol-9 (N-9), a spermicidal agent, were examined. The viscosity was measured using a Cone Plate Digital Viscometer, while the water and total protein contents were determined by the lyophilization process and the Lowry method, respectively. The significant changes in the rheological properties of mucus, such as its viscosity and the water content, upon exposure to EDTA were demonstrated. The viscosity of cervical mucus and human semen were significantly increased by EDTA treatment (as compared to the controls): lamb cervical mucus (2.9 ± 0.3 vs. 2.2 ± 0.3 cps) and human semen (5.0 ± 0.3 vs. 4.3 ± 0.3 cps), respectively. The hydration rate was decreased by EDTA treatment as compared with the control (93.6 ± 0.7 vs. 96.8 ± 0.8%). Among tested samples, the reduction in the percentage of sperm penetration through the cervical mucus was the highest in the mucus containing EDTA, which had the lowest water content (93.6 ± 0.7%), indicating that there is a positive relationship between the hydration rate of the cervical mucus and its ability to permit the penetration of spermatozoa. This result indicates that spermicidal activity exerted by high concentrations of EDTA is in part due to its effect on the rheological properties of cervical mucus or semen. 相似文献
80.
Radiographic manifestations of bronchiolitis obliterans with organizing pneumonia vs usual interstitial pneumonia 总被引:1,自引:0,他引:1
P W Chandler M S Shin S E Friedman J L Myers A L Katzenstein 《AJR. American journal of roentgenology》1986,147(5):899-906
The radiographic findings in 24 cases of bronchiolitis obliterans with organizing pneumonia and 16 cases of usual interstitial pneumonia were reviewed and compared. Some cases of bronchiolitis obliterans with organizing pneumonia have been mistaken for usual interstitial pneumonia, although the two diseases have distinct pathologic findings. Clinically, the diseases often have different manifestations. Bronchiolitis obliterans with organizing pneumonia has a better prognosis and often responds well to steroids. This study shows that the radiologic findings of bronchiolitis obliterans include alveolar opacities without lung-volume loss. Patients with usual interstitial pneumonia, however, have bilateral diffuse interstitial opacities with occasional honeycomb changes, and there is loss of lung volume in most patients. These findings suggest that the chest radiograph can aid in distinguishing the two diseases. 相似文献