全文获取类型
收费全文 | 107007篇 |
免费 | 6028篇 |
国内免费 | 648篇 |
专业分类
耳鼻咽喉 | 1041篇 |
儿科学 | 3482篇 |
妇产科学 | 2450篇 |
基础医学 | 15381篇 |
口腔科学 | 3927篇 |
临床医学 | 9702篇 |
内科学 | 24094篇 |
皮肤病学 | 2709篇 |
神经病学 | 10464篇 |
特种医学 | 2482篇 |
外国民族医学 | 1篇 |
外科学 | 9525篇 |
综合类 | 395篇 |
一般理论 | 48篇 |
预防医学 | 10711篇 |
眼科学 | 1716篇 |
药学 | 7493篇 |
中国医学 | 418篇 |
肿瘤学 | 7644篇 |
出版年
2024年 | 120篇 |
2023年 | 1028篇 |
2022年 | 2211篇 |
2021年 | 3653篇 |
2020年 | 2289篇 |
2019年 | 3073篇 |
2018年 | 3489篇 |
2017年 | 2661篇 |
2016年 | 3103篇 |
2015年 | 3427篇 |
2014年 | 4496篇 |
2013年 | 5877篇 |
2012年 | 8938篇 |
2011年 | 9289篇 |
2010年 | 5065篇 |
2009年 | 4263篇 |
2008年 | 7383篇 |
2007年 | 7378篇 |
2006年 | 6788篇 |
2005年 | 6332篇 |
2004年 | 5682篇 |
2003年 | 5060篇 |
2002年 | 4554篇 |
2001年 | 541篇 |
2000年 | 371篇 |
1999年 | 585篇 |
1998年 | 789篇 |
1997年 | 643篇 |
1996年 | 547篇 |
1995年 | 450篇 |
1994年 | 428篇 |
1993年 | 351篇 |
1992年 | 295篇 |
1991年 | 194篇 |
1990年 | 199篇 |
1989年 | 182篇 |
1988年 | 171篇 |
1987年 | 143篇 |
1986年 | 156篇 |
1985年 | 109篇 |
1984年 | 132篇 |
1983年 | 130篇 |
1982年 | 157篇 |
1981年 | 115篇 |
1980年 | 124篇 |
1979年 | 72篇 |
1978年 | 77篇 |
1977年 | 72篇 |
1976年 | 59篇 |
1974年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Maria Grazia Daidone Rosella Silvestrini Nadia Zaffaroni Egle Grignolio Fabio Landoni 《Investigational new drugs》1987,5(3):245-250
An in vitro assay, which evaluates drug effect on 3H-thymidine incorporation, was used to investigate the absolute and relative activities of cisplatin (DDP), carboplatin (CBDCA) and iproplatin (CHIP) on 317 specimens from untreated tumors, including breast and ovarian cancers and malignant melanomas. Similar activities were generally observed for DDP and CHIP, whereas CBDCA exhibited a lower, although not significantly different cytotoxicity on breast and ovarian cancers. The relative activities of Platinum analogues were analyzed on 239 two-way drug sensitivity comparisons. The overall agreement rates ranged from 80.2 to 83.9% for the different comparisons. High coresistance, from 61.1 to 93.8%, was observed for all the comparisons, regardless of the tumor type. Cosensitivity rates were poor for breast and ovarian cancers, from 0 to 37.5%, whereas for melanomas an association in sensitivity was observed in 80% of the cases. 相似文献
62.
63.
Paavo Riekkinen Jr. Jouni Sirvi Pekka Jkl Maria Mazurkiewicz Antti Valjakka Minna Riekkinen Paavo Riekkinen 《Brain research bulletin》1991,27(2):287-289
Quisqualic acid NBM lesions had no effect on water maze performance, but slightly impaired passive avoidance acquisition. GammavinylGABA treatment alone had no effect on the passive avoidance and water maze performance, but aggravated acquisition deficit in rats subjected to NBM lesioning. However, gammavinylGABA-treated NBM-lesioned rats reached control level of performance. 相似文献
64.
Marina Quartu Maria Pina Serra Annalisa Manca Paolo Follesa Rossano Ambu Marina Del Fiacco 《International journal of developmental neuroscience》2003,21(6):309-320
The immunohistochemical occurrence of the high affinity neurotrophin (NT) receptors trkA, trkB, and trkC is shown in the pre-term newborn, infant, and adult human post-mortem cerebellum. Immunoreactive neuronal perikarya and processes were observed in all specimens examined, where they appeared unevenly distributed in the cerebellar cortical layers and deep nuclei, and showed regional differences among cerebellar lobules and folia. The trk receptor-antibodies, tested by Western blot on human cerebellum homogenates, revealed multiple immunoreactive bands for trkA and single bands for trkB and trkC. The results obtained show the tissue localization of the trk receptor-like immunoreactivity in the human cerebellum from prenatal to adult age. The analysis for codistribution of the receptors with the relevant ligand and among the receptors in discrete cortical and deep nuclei tissue fields shows a wide variety of conditions, from a good similarity in terms of type and density of labeled structures, to a lack of correspondence, and suggests the possibility of colocalization of trk receptors with the relevant neurotrophin and among them in the cerebellar cortex. These results sustain the concept that the neurotrophin trophic system participates in the development, differentiation, and maintenance of the human cerebellar connectivity and support the possibility of a multifactorial trophic support for the neurotrophins through target-derived and local mechanisms. 相似文献
65.
Serafim N. Nanas John N. Nanas Christos E. Charitos Alexandros Gougoulakis Konstantinos Makaritsis John Chatzigeorgiou Kiriaki Moussoutzani Maria I. Anastasiou-Nana Spyridon D. Moulopoulos 《World journal of surgery》1997,21(3):318-322
p
< 0.001), the tension time index (712 ± 381 versus 1333 ± 694,
p
< 0.01), and the double product (5629 ± 2574 versus 7440 ± 3294,
p
< 0.01) were significantly lower during assistance with the PACD than with the CBP. It was concluded that PACD is at least
as effective as CBP for restoring hemodynamic status during acute experimental cardiogenic shock. Moreover, the PACD unloads
the left ventricle more effectively than CBP, making it suitable for left ventricular mechanical support in cases with reversible
myocardial damage. 相似文献
66.
Giorgio Nanni Federica Majorani Anna Maria Bassi Claudio Canepa Giuseppe Maloberti Anna Casu 《Experimental and toxicologic pathology》2002,54(1):43-50
The content of dolichol, an isoprenoid present in all biological membranes, was determined in isolated sinusoidal liver cells after treatment of rats for 2 and 4 months with a low dosage of the hepatotoxin thioacetamide. The significant decrease in dolichol observed in hepatocytes after 2 months might be explained by peroxidation of the isoprenoid. At the same time point, retinol was retained, and decreased only after 4 months of treatment. After 4 months of treatment therefore both lipids decreased. In a subfraction of hepatic stellate cells, Ito-1 cells, the main storage site of vitamin A, dolichol decreased significantly only after 4 months. A remarkable difference from hepatocytes is that in Ito-1 cells retinol content significantly decreased after 2 months of treatment. In another subfraction, Ito-2 cells, the content of the two isoprenoids decreased in parallel. This heterogeneous subfraction might represent those transitional hepatic stellate cells that, while losing retinol, are in the process of differentiating into myofibroblasts secreting extracellular matrix components. In Kupffer cells and sinusoidal endothelial cells, impairment of dolichol might be observed later, only after 4 months of treatment, while retinol decreases uniformly over time. Starting after two months of treatment, the decrease of dolichol and the increase of retinol in hepatocytes, at the same time as retinol decreases in hepatic stellate cells, might be taken as an early index of incipient liver injury due to thioacetamide. This hypothesis is discussed with regard to a role of dolichol in the modulation of membrane fluidity for intracellular and intercellular retinol transport. 相似文献
67.
Maria Drangova Yudong Zhu Norbert J. Pelc 《Journal of magnetic resonance imaging : JMRI》1997,7(4):664-668
The reproducibility of myocardial motion trajectories calculated from cine phase-contrast (PC) velocity data is reduced by artifacts due to the inconsistent motion of intracardiac blood. Spatial presaturation reduces these artifacts but requires a longer sequence TR, with a potentially negative effect on trajectory accuracy and reproducibility. We investigated the effect of spatial presaturation on trajectory reproducibility. A midventricular transaxial slice was imaged in five normal volunteers. The same slice was imaged three times each with sequences using spatial presaturation or not. Because the most serious artifacts originate in the heart chambers and propagate in the phase-encoded direction, myocardial regions that were in line with the heart chambers (in the phase-encode direction) had the highest artifact level in the scans without spatial presaturation. The reproducibility of trajectories for regions placed in these areas (the anterior wall, septum and posterior wall in the transaxial scans with phase encoding in the anterior-posterior direction) improved by a factor of two when presaturation was used (P < .001). In areas that were not in line with the heart chambers (eg, the anterior aspect of the lateral wall in the transaxial scans), the effect of presaturation was not significant. These results correlate well with the measured reduction in artifact level. The reproducibility of myocardial motion trajectories over large areas of the heart is improved to approximately 1 mm when presaturation is used. Therefore, use of presaturation is recommended for myocardial motion studies using cine PC velocity data. 相似文献
68.
Maria Råstam Christopher Gillberg Jan Wahlström† 《Journal of child psychology and psychiatry, and allied disciplines》1991,32(4):695-701
Forty-seven cases with anorexia nervosa (including a total population group) and 47 sex-, age-, and school-matched comparison cases were subjected to chromosome analyses in a blind fashion. No major abnormalities were found in any of the cases. Sex chromatin was analysed in buccal smears from the girls. No differences between the anorexia nervosa and the comparison cases were found. It seems that chromosomal/sex chromatin analyses in anorexia nervosa are not warranted. 相似文献
69.
We tested the ability of normal subjects to make changes in the conjugacy of their saccades. Subjects dichoptically viewed a grid the size of which was 10% larger in one eye. The grids were centred onto a flat screen at 57 cm or 1 m from the subject. Horizontal saccades immediately became larger in the eye viewing the larger grid. For some subjects this disconjugacy persisted even under subsequent monocular viewing. Such persistent changes occurred mainly in the field where the required disconjugacy was divergent for centrifugal saccades, convergent for centripetal saccades. Vertical saccades also developed compensatory disconjugacy; its amplitude was smaller but less variable. To explain these results we propose a fast associative learning mechanism that pairs peripheral disparity with saccades and is capable of producing saccade disconjugacy even in the absence of disparity. For horizontal saccades a secondary conditioning of monocular depth cues by the disparity would also be involved. 相似文献
70.
BACKGROUND: When and whether early enteral nutrition (EN) benefits critically ill patients is debatable. This prospective clinical audit aimed to evaluate the feasibility of an early EN protocol and to identify factors that may hinder EN delivery in critically ill patients. METHODS: Thirty-six medical patients with severe respiratory failure under invasive ventilation and scheduled to receive early EN, with a length of ICU stay >72 hours, were included. As asserted by the Society of Critical Care Medicine, 8% of patients were priority 1, 72% priority 2, and 20% priority 3 for intensive therapeutic and vital support interventions. RESULTS: Overall, because of gastrointestinal complications, only 39% of the prescribed EN was administered; only 8 (22%) patients did tolerate EN within the first 48 hours after admission and did achieve their minimum nutritional requirements. The most frequent complication (78%) was high volume of gastric residuals followed by abdominal distention (61%), both associated with hemodynamic instability (HI). Gastrointestinal dysfunction was associated with high Acute Physiologic and Chronic Health Evaluation II score (p = .01), total calorie intake (p = .02), total carbohydrate intake (p = .02), HI (p = .03), malnutrition (p = .04), volume of IV saline (p = .04), and concurrent vasoactive drug administration (p = .05). CONCLUSIONS: This audit in extremely severe intensive care patients identified several factors that impair gastrointestinal function and preclude EN at any stage, namely early EN. Nutrition management must take into account concurrent therapies, given their potential interference with nutrition and organ function. 相似文献