全文获取类型
收费全文 | 8824篇 |
免费 | 577篇 |
国内免费 | 68篇 |
专业分类
耳鼻咽喉 | 39篇 |
儿科学 | 205篇 |
妇产科学 | 103篇 |
基础医学 | 942篇 |
口腔科学 | 149篇 |
临床医学 | 916篇 |
内科学 | 2199篇 |
皮肤病学 | 158篇 |
神经病学 | 484篇 |
特种医学 | 208篇 |
外国民族医学 | 2篇 |
外科学 | 1637篇 |
综合类 | 230篇 |
现状与发展 | 1篇 |
一般理论 | 5篇 |
预防医学 | 528篇 |
眼科学 | 226篇 |
药学 | 813篇 |
中国医学 | 155篇 |
肿瘤学 | 469篇 |
出版年
2024年 | 14篇 |
2023年 | 146篇 |
2022年 | 344篇 |
2021年 | 677篇 |
2020年 | 398篇 |
2019年 | 487篇 |
2018年 | 481篇 |
2017年 | 312篇 |
2016年 | 329篇 |
2015年 | 358篇 |
2014年 | 438篇 |
2013年 | 525篇 |
2012年 | 799篇 |
2011年 | 736篇 |
2010年 | 360篇 |
2009年 | 333篇 |
2008年 | 498篇 |
2007年 | 458篇 |
2006年 | 389篇 |
2005年 | 359篇 |
2004年 | 279篇 |
2003年 | 262篇 |
2002年 | 126篇 |
2001年 | 51篇 |
2000年 | 47篇 |
1999年 | 26篇 |
1998年 | 23篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 20篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 14篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1972年 | 7篇 |
1969年 | 9篇 |
1968年 | 5篇 |
1967年 | 4篇 |
排序方式: 共有9469条查询结果,搜索用时 31 毫秒
111.
John T. Heap Jan Theys Muhammad Ehsaan Aleksandra M Kubiak Ludwig Dubois Kim Paesmans Lieve Van Mellaert Richard Knox Sarah A. Kuehne Phillipe Lambin Nigel P. Minton 《Oncotarget》2014,5(7):1761-1769
Spores of some species of the strictly anaerobic bacteria Clostridium naturally target and partially lyse the hypoxic cores of tumors, which tend to be refractory to conventional therapies. The anti-tumor effect can be augmented by engineering strains to convert a non-toxic prodrug into a cytotoxic drug specifically at the tumor site by expressing a prodrug-converting enzyme (PCE). Safe doses of the favored prodrug CB1954 lead to peak concentrations of 6.3 μM in patient sera, but at these concentration(s) known nitroreductase (NTR) PCEs for this prodrug show low activity. Furthermore, efficacious and safe Clostridium strains that stably express a PCE have not been reported. Here we identify a novel nitroreductase from Neisseria meningitidis, NmeNTR, which is able to activate CB1954 at clinically-achievable serum concentrations. An NmeNTR expression cassette, which does not contain an antibiotic resistance marker, was stably localized to the chromosome of Clostridium sporogenes using a new integration method, and the strain was disabled for safety and containment by making it a uracil auxotroph. The efficacy of Clostridium-Directed Enzyme Prodrug Therapy (CDEPT) using this system was demonstrated in a mouse xenograft model of human colon carcinoma. Substantial tumor suppression was achieved, and several animals were cured. These encouraging data suggest that the novel enzyme and strain engineering approach represent a promising platform for the clinical development of CDEPT. 相似文献
112.
113.
Muhammad Arif 《Journal of medical systems》2012,36(3):1173-1181
In pattern classification problems, feature extraction is an important step. Quality of features in discriminating different
classes plays an important role in pattern classification problems. In real life, pattern classification may require high
dimensional feature space and it is impossible to visualize the feature space if the dimension of feature space is greater
than four. In this paper, we have proposed a Similarity-Dissimilarity plot which can project high dimensional space to a two
dimensional space while retaining important characteristics required to assess the discrimination quality of the features.
Similarity-dissimilarity plot can reveal information about the amount of overlap of features of different classes. Separable
data points of different classes will also be visible on the plot which can be classified correctly using appropriate classifier.
Hence, approximate classification accuracy can be predicted. Moreover, it is possible to know about whom class the misclassified
data points will be confused by the classifier. Outlier data points can also be located on the similarity-dissimilarity plot.
Various examples of synthetic data are used to highlight important characteristics of the proposed plot. Some real life examples
from biomedical data are also used for the analysis. The proposed plot is independent of number of dimensions of the feature
space. 相似文献
114.
Ran Chen Meihua Zhu Kacie Amacher Xia Wu David J. Sahn Muhammad Ashraf 《Ultrasound in medicine & biology》2017,43(10):2247-2255
The aim of this study was to evaluate the accuracy and feasibility of real-time 3-D echocardiography (3-DE) in assessing right ventricular (RV) systolic function. A latex balloon was inserted into the right ventricle of 20 freshly harvested pig hearts which were then passively driven by a pulsatile pump apparatus. The RV global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS) and RV ejection fraction (RVEF), derived from 3-DE, as well as the RVEF obtained from 2-D echocardiography (2-DE) were quantified at different stroke volumes (30–70 mL) and compared with sonomicrometry data. In all comparisons, 3-D GLS, GCS, GAS, 2-D RVEF and 3-D RVEF exhibited strong correlations with sonomicrometry data (r = 0.89, 0.79, 0.74, 0.80, and 0.93, respectively; all p values < 0.001). Bland–Altman analyses revealed slight overestimations of echo-derived GLS, GCS, 2-DE RVEF and 3-DE RVEF compared with sonomicrometry values (bias = 1.55, 2.72, 3.59 and 2.21, respectively). Furthermore, there is better agreement among GLS, 3-D RVEF and the sonomicrometry values than between GCS and 2-D RVEF. Real-time 3-DE is more feasible and accurate for assessing RV function than 2-DE. GLS is a potential alternative parameter for quantifying RV systolic function. 相似文献
115.
116.
117.
Levetiracetam (LEV) is an approved drug for the treatment of some epileptic disorders. With few and controversial reports addressing its possible pharmacodynamic interactions, the current study aimed at studying the effect of LEV on isolated rat duodenal strips to enlighten its possible intestinal adverse effects using the isolated smooth muscle strips of rat duodenum. LEV showed a dose‐dependent inhibition in KCl (80 mm )‐induced contractions in normal Tyrode's solution. Moreover, preincubation with LEV (3 mm ) in K+‐rich/Ca2+‐free medium led to a significant decrease in the maximum contractions (Emax) coupled to a right shift of the cumulative CaCl2 concentration curves implying a possible Ca2+ channel blocking potential. In addition, LEV exhibited a typical noncompetitive inhibition in the cumulative carbachol concentration curves evidenced as a decrease in Emax without the alteration of EC50, thus eliminating any possible role of the muscarinic receptors in the relaxant effect. To rule out other possible relaxant mechanisms, tests were conveyed in Tyrode's solution containing either 100 μm l ‐NAME or 10 μm glimepiride to test the possible relaxant roles exhibited by nitric oxide (NO) and KATP channel opening, respectively. None of the tested pathways was involved in LEV‐mediated relaxation. Taken altogether, the results of the current study entail that LEV might exert a relaxant effect on intestinal smooth muscles through blocking L‐type voltage‐operated calcium channels, but not involving either NO release or KATP channel opening. 相似文献
118.
119.
120.
Faqir Muhammad Tuyen Duong Thanh Nguyen Ahmad Raza Bushra Akhtar 《Drug and chemical toxicology》2017,40(4):489-497
Nanotechnology has gained significant penetration to different fields of medicine including drug delivery, disease interrogation, targeting and bio-imaging. In recent years, efforts have been put forth to assess the use of this technology in biodetoxification. In this review, we will discuss the current status of nanostructured biomaterials/nanoparticle (NP)-based technologies as a candidate biodetoxifying agent. Patient hospitalization due to illicit drug consumption, suicidal attempts and accidental toxin exposure are major challenges in the medical field. Overdoses of drugs/toxic chemicals or exposure to bacterial toxins or poisons are conventionally treated by voiding the stomach, administering activated charcoal or by using specific antidotes, if the toxin is known. Because of the limitations of these methods for safe and effective detoxification, advancements in nanotechnology may offer novel ways in intoxication support by using nanostructured biomaterials, such as liposomes, micellar nanocarriers, liquid crystalline nanoassemblies and ligand-based NPs. 相似文献