全文获取类型
收费全文 | 13659篇 |
免费 | 815篇 |
国内免费 | 65篇 |
专业分类
耳鼻咽喉 | 286篇 |
儿科学 | 275篇 |
妇产科学 | 237篇 |
基础医学 | 1745篇 |
口腔科学 | 1141篇 |
临床医学 | 992篇 |
内科学 | 3226篇 |
皮肤病学 | 283篇 |
神经病学 | 1245篇 |
特种医学 | 251篇 |
外科学 | 1938篇 |
综合类 | 77篇 |
一般理论 | 2篇 |
预防医学 | 1109篇 |
眼科学 | 236篇 |
药学 | 888篇 |
中国医学 | 95篇 |
肿瘤学 | 513篇 |
出版年
2023年 | 124篇 |
2022年 | 209篇 |
2021年 | 581篇 |
2020年 | 322篇 |
2019年 | 516篇 |
2018年 | 565篇 |
2017年 | 375篇 |
2016年 | 458篇 |
2015年 | 483篇 |
2014年 | 696篇 |
2013年 | 752篇 |
2012年 | 1203篇 |
2011年 | 1247篇 |
2010年 | 657篇 |
2009年 | 504篇 |
2008年 | 835篇 |
2007年 | 795篇 |
2006年 | 713篇 |
2005年 | 616篇 |
2004年 | 556篇 |
2003年 | 435篇 |
2002年 | 387篇 |
2001年 | 203篇 |
2000年 | 195篇 |
1999年 | 166篇 |
1998年 | 58篇 |
1997年 | 55篇 |
1996年 | 29篇 |
1995年 | 46篇 |
1994年 | 22篇 |
1993年 | 31篇 |
1992年 | 74篇 |
1991年 | 80篇 |
1990年 | 64篇 |
1989年 | 69篇 |
1988年 | 51篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 34篇 |
1984年 | 17篇 |
1983年 | 21篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1975年 | 20篇 |
1974年 | 13篇 |
1973年 | 15篇 |
1971年 | 12篇 |
1970年 | 13篇 |
1969年 | 14篇 |
1968年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Andrade C Gangadhar BN Subbakrishna DK Channabasavanna SM Pradhan N 《Convulsive therapy》1988,4(4):297-305
In a double-blind prospective study, 29 endogenously depressed patients (RDC) were randomized into sinusoidal wave (SW) and brief-pulse (BP) electroconvulsive therapy (ECT) groups. Bilateral modified treatments were administered on alternate days, three per week, and the treatment variables of current dosage and seizure duration were monitored for each treatment. Significantly more patients responded to SW than to BP ECT, but a comparable number of treatments was required to produce this response in the two groups. There was no difference in clinical or treatment variables between the SW and the BP groups, nor between ECT responders and nonresponders, with the exception that the SW-treated patients received larger doses of current per treatment than did the BP patients. For endogenous depression treated with ECT, we conclude that cumulative seizure duration may not be a parameter of significance, that overall rate of recovery in ECT responders is independent of stimulus waveform, and that some depressives may respond to SW but not to BP ECT. We suggest that the antidepressant effect of the ECT seizure may be characterized by a therapeutic window in current requirements; alternatively, a putative response threshold (again in terms of current requirement) may exist, which is higher in some patients than in others. 相似文献
42.
Thirty-two endogenous depressed patients (RDC) were treated with electroconvulsive therapy. Four patients (12.5%) developed a transient manic reaction; in two cases, this reaction occurred in mid-depression. Mania is not a generally recognized side effect of ECT; we detail the clinical characteristics, but fail to define clinical predictors of vulnerability. 相似文献
43.
Meyer-Fernandes JR Saad-Nehme J Peres-Sampaio CE Belmont-Firpo R Bisaggio DF Do Couto LC Fonseca De Souza AL Lopes AH Souto-Padrón T 《Parasitology research》2004,93(1):41-50
In this work, we describe the ability of living epimastigotes of Trypanosoma cruzi to hydrolyze extracellular ATP. In these intact parasites, there was a low level of ATP hydrolysis in the absence of any divalent metal (2.42±0.31 nmol Pi/h×108 cells). ATP hydrolysis was stimulated by MgCl2, and the Mg-dependent ecto-ATPase activity was 27.15±2.91 nmol Pi/h×108 cells. The addition of MgCl2 to the extracellular medium increased the ecto-ATPase activity in a dose-dependent manner. This stimulatory activity was also observed when MgCl2 was replaced by MnCl2, but not by CaCl2 or SrCl2. The apparent Km for Mg-ATP2– was 0.61 mM, and free Mg2+ did not increase the ecto-ATPase activity. This ecto-ATPase activity was insensitive to the inhibitors of other ATPase and phosphatase activities. To confirm that this Mg-dependent ATPase was an ecto-ATPase, we used an impermeant inhibitor, DIDS (4, 4.diisothiocyanostylbene 2-2-disulfonic acid) as well as suramin, an antagonist of P2 purinoreceptors and inhibitor of some ecto-ATPases. These two reagents inhibited the Mg2+-dependent ATPase activity in a dose-dependent manner. A comparison among the Mg2+-ecto-ATPase activities of the three forms of T. cruzi showed that the noninfective epimastigotes were less efficient at hydrolyzing ATP than the infective trypomastigote and amastigote stages. 相似文献
44.
de Andrade AL Pimenta FC Laval CA de Andrade JG Guerra ML Brandileone MC 《Journal of clinical microbiology》2004,42(5):2345-2346
We present a case of invasive pneumococcal infection in a healthy 10-month-old infant from whom Streptococcus pneumoniae serotype 23F was isolated from the blood and serotype 23B was isolated from the cerebrospinal fluid. Both serotypes were penicillin nonsusceptible. Pulsed-field gel electrophoresis analysis demonstrated that the two serotypes had distinct DNA patterns, indicating that infection did not occur as a result of capsular transformation but as a result of a mixed infection with two distinct pneumococcal serotypes. 相似文献
45.
Michael A Tangrea Rodrigo F Chuaqui John W Gillespie Mamoun Ahram Gallya Gannot Benjamin S Wallis Carolyn J M Best W Marston Linehan Lance A Liotta Thomas J Pohida Robert F Bonner Michael R Emmert-Buck 《Diagnostic molecular pathology》2004,13(4):207-212
Tissue microdissection is an important method for the study of disease states. However, it is difficult to perform high-throughput molecular analysis with current techniques. We describe here a prototype version of a novel technique (expression microdissection) that allows for the procurement of desired cells via molecular targeting. Expression microdissection (xMD) offers significant advantages over available methods, including an increase in dissection speed of several orders of magnitude. xMD may become a valuable tool for investigators studying cancer or other disease states in patient specimens and animal models. 相似文献
46.
Performance characteristics of a rapid new immunochromatographic test for detection of antibodies to human immunodeficiency virus 总被引:1,自引:0,他引:1
Ribeiro-Rodrigues R Ferreira da Silva Pinto Neto L Cunha CB Cabral VP Dietze R 《Clinical and diagnostic laboratory immunology》2003,10(2):303-307
A new immunochromatographic rapid test (Rapid Check HIV 1 and 2; Núcleo de Doen?as Infecciosas) for the detection of antibodies to human immunodeficiency virus type 1 and type 2 in human samples (whole blood, serum, and plasma) was evaluated and compared to the commercially available Determine (Abbott Laboratories). When whole-blood samples were evaluated, the specificity and sensitivity of both tests were 100%. However, when plasma samples were used, sensitivity for the Rapid Check HIV 1&2 and the Determine tests were 100 and 98.58%, respectively. The observed specificity for plasma samples was 98.94% for the Rapid Check HIV 1&2 and 96.97% for the Determine test. The results presented here are encouraging and support the adoption of both tests as an alternative to enzyme-lined immunosorbent assay and/or Western blots in regions where laboratorial infrastructure is not available or for use in the management of occupational accidents for healthcare workers. 相似文献
47.
Responses to natural scenes in cat V1 总被引:3,自引:0,他引:3
Studies on processing in primary visual areas often use artificial stimuli such as bars or gratings. As a result, little is known about the properties of activity patterns for the natural stimuli processed by the visual system on a daily basis. Furthermore, in the cat, a well-studied model system for visual processing, most results are obtained from anesthetized subjects and little is known about neuronal activations in the alert animal. Addressing these issues, we measure local field potentials (lfp) and multiunit spikes in the primary visual cortex of awake cats. We compare changes in the lfp power spectra and multiunit firing rates for natural movies, movies with modified spatio-temporal correlations as well as gratings. The activity patterns elicited by drifting gratings are qualitatively and quantitatively different from those elicited by natural stimuli and this difference arises from both spatial as well as temporal properties of the stimuli. Furthermore, both local field potentials and multiunit firing rates are most sensitive to the second-order statistics of the stimuli and not to their higher-order properties. Finally, responses to natural movies show a large variability over time because of activity fluctuations induced by rapid stimulus motion. We show that these fluctuations are not dependent on the detailed spatial properties of the stimuli but depend on their temporal jitter. These fluctuations are important characteristics of visual activity under natural conditions and impose limitations on the readout of possible differences in mean activity levels. 相似文献
48.
Tanaka E del Pozo R Tanaka M Aoyama J Hanaoka K Nakajima A Inuzuka S Tanne K 《Journal of biomedical materials research. Part A》2003,67(3):761-765
This study evaluates the effect of strain rate on the biomechanical responses of bovine temporomandibular joint (TMJ) disk under compression. Ten specimens derived from the central region of bovine TMJ disks were used for compression tests. Each specimen was loaded upto 20% of strain with seven different strain rates: 1, 10, 20, 30, 40, 50, and 60%/s. Although the stress-strain curves presented similar patterns for all the specimens, the strain-rate effect was obvious. The linear modulus by regression fit for the linear part of the curve was significantly larger at 60%/s of strain rate than at the lower strain rates. The "supplemental stress" ratio (SSR) obviously increased with the augmentation of the strain rate. At strain rates of 30-60%/s, the SSR was significantly larger than those at strain rates below 20%/s. These findings indicate that although water easily can move through the TMJ disk at the lower strain rates, the higher strain rates make such movement difficult. It is concluded that the secondary changes of the TMJ disk may be dependent on the pattern and velocity of masticatory mandibular movements directly associated with the dynamic strain rate in the TMJ disk. 相似文献
49.
Rodrigo A. Cunha A. M. Sebastião 《Pflügers Archiv : European journal of physiology》1993,424(5-6):503-510
The independent release of adenosine and adenine nucleotides upon electrical stimulation was studied in the innervated sartorius muscle of the frog after blockade of the extracellular catabolism of adenosine monophosphate (AMP) through exo-AMP deaminase and ecto-5-nucleotidase. Nerve stimulation (30 min, 0.2Hz) induced the release of both adenosine (19±3 pmol) and adenine nucleotides (101±7 pmol). Experiments performed in the presence of tubocurarine (5 M) to prevent purine release due to nerve-evoked muscle twitching, or under direct stimulation of the muscle in low calcium solutions to prevent pre-synaptic release of purines, showed that there was an evoked release of adenosine and adenine nucleotides both from the nerve endings and from the twitching muscle fibres. Removal of ecto-5-nucleotidase inhibition shows that the catabolism of adenine nucleotides released during stimulation contributes in about 50% to the amount of endogenous extracellular adenosine. When only one of the enzymes catabolizing AMP (ecto-5-nucleotidase or exo-AMP deaminase) was inhibited, the evoked release of adenine nucleotides was undetectable, suggesting that each enzyme is able to catabolize all the AMP formed from adenine nucleotides released upon stimulation. It is concluded that the concentration of endogenous extracellular adenosine is under the control of the relative activities of exo-AMP deaminase and ecto-5-nucleotidase.Brief accounts of some of the results in this study have been published previously (refs. [6, 7]). 相似文献
50.
Elisa Moya-Sáez Rafael Navarro-González Santiago Cepeda Ángel Pérez-Núñez Rodrigo de Luis-García Santiago Aja-Fernández Carlos Alberola-López 《NMR in biomedicine》2022,35(9):e4754
Glioblastoma is an aggressive and fast-growing brain tumor with poor prognosis. Predicting the expected survival of patients with glioblastoma is a key task for efficient treatment and surgery planning. Survival predictions could be enhanced by means of a radiomic system. However, these systems demand high numbers of multicontrast images, the acquisitions of which are time consuming, giving rise to patient discomfort and low healthcare system efficiency. Synthetic MRI could favor deployment of radiomic systems in the clinic by allowing practitioners not only to reduce acquisition time, but also to retrospectively complete databases or to replace artifacted images. In this work we analyze the replacement of an actually acquired MR weighted image by a synthesized version to predict survival of glioblastoma patients with a radiomic system. Each synthesized version was realistically generated from two acquired images with a deep learning synthetic MRI approach based on a convolutional neural network. Specifically, two weighted images were considered for the replacement one at a time, a T2w and a FLAIR, which were synthesized from the pairs T1w and FLAIR, and T1w and T2w, respectively. Furthermore, a radiomic system for survival prediction, which can classify patients into two groups (survival >480 days and 480 days), was built. Results show that the radiomic system fed with the synthesized image achieves similar performance compared with using the acquired one, and better performance than a model that does not include this image. Hence, our results confirm that synthetic MRI does add to glioblastoma survival prediction within a radiomics-based approach. 相似文献