全文获取类型
收费全文 | 36036篇 |
免费 | 2439篇 |
国内免费 | 123篇 |
专业分类
耳鼻咽喉 | 390篇 |
儿科学 | 1033篇 |
妇产科学 | 716篇 |
基础医学 | 4614篇 |
口腔科学 | 566篇 |
临床医学 | 4153篇 |
内科学 | 7064篇 |
皮肤病学 | 680篇 |
神经病学 | 3095篇 |
特种医学 | 1216篇 |
外科学 | 5346篇 |
综合类 | 415篇 |
一般理论 | 48篇 |
预防医学 | 3647篇 |
眼科学 | 769篇 |
药学 | 2547篇 |
中国医学 | 66篇 |
肿瘤学 | 2233篇 |
出版年
2023年 | 256篇 |
2022年 | 464篇 |
2021年 | 1066篇 |
2020年 | 650篇 |
2019年 | 889篇 |
2018年 | 1029篇 |
2017年 | 765篇 |
2016年 | 853篇 |
2015年 | 993篇 |
2014年 | 1292篇 |
2013年 | 1706篇 |
2012年 | 2696篇 |
2011年 | 2742篇 |
2010年 | 1526篇 |
2009年 | 1433篇 |
2008年 | 2289篇 |
2007年 | 2517篇 |
2006年 | 2281篇 |
2005年 | 2222篇 |
2004年 | 2146篇 |
2003年 | 1955篇 |
2002年 | 1694篇 |
2001年 | 365篇 |
2000年 | 307篇 |
1999年 | 365篇 |
1998年 | 355篇 |
1997年 | 237篇 |
1996年 | 210篇 |
1995年 | 168篇 |
1994年 | 182篇 |
1993年 | 162篇 |
1992年 | 169篇 |
1991年 | 173篇 |
1990年 | 139篇 |
1989年 | 153篇 |
1988年 | 129篇 |
1987年 | 137篇 |
1986年 | 141篇 |
1985年 | 137篇 |
1984年 | 126篇 |
1983年 | 112篇 |
1982年 | 106篇 |
1981年 | 127篇 |
1980年 | 90篇 |
1979年 | 89篇 |
1978年 | 83篇 |
1977年 | 72篇 |
1976年 | 59篇 |
1975年 | 49篇 |
1974年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Background
Persisting neck pain is common in society. It has been reported that the prevalence of neck pain in office workers is much higher than in the general population. The costs to the worker, employer and society associated with work-related neck pain are known to be considerable and are escalating. The factors that place office workers at greater risk of developing neck pain are not understood. The aim of this study is to investigate the incidence and risk factors of work-related neck pain in Australian office workers. 相似文献82.
In vivo MRI of cancer cell fate at the single-cell level in a mouse model of breast cancer metastasis to the brain. 总被引:7,自引:0,他引:7
Chris Heyn John A Ronald Soha S Ramadan Jonatan A Snir Andrea M Barry Lisa T MacKenzie David J Mikulis Diane Palmieri Julie L Bronder Patricia S Steeg Toshiyuki Yoneda Ian C MacDonald Ann F Chambers Brian K Rutt Paula J Foster 《Magnetic resonance in medicine》2006,56(5):1001-1010
Metastasis (the spread of cancer from a primary tumor to secondary organs) is responsible for most cancer deaths. The ability to follow the fate of a population of tumor cells over time in an experimental animal would provide a powerful new way to monitor the metastatic process. Here we describe a magnetic resonance imaging (MRI) technique that permits the tracking of breast cancer cells in a mouse model of brain metastasis at the single-cell level. Cancer cells that were injected into the left ventricle of the mouse heart and then delivered to the brain were detectable on MR images. This allowed the visualization of the initial delivery and distribution of cells, as well as the growth of tumors from a subset of these cells within the whole intact brain volume. The ability to follow the metastatic process from the single-cell stage through metastatic growth, and to quantify and monitor the presence of solitary undivided cells will facilitate progress in understanding the mechanisms of brain metastasis and tumor dormancy, and the development of therapeutics to treat this disease. 相似文献
83.
84.
85.
86.
Jansen Jacob G.; van Teijlingen Corrie M. M.; MOHN Georges R.; van Zeeland Albert A.; Vrieling Harry 《Mutagenesis》1994,9(5):417-421
Spectra of N-ethyl-N-nitrosourea (ENU)-induced mutations differwidely among various in vitro and in vivo mutational systems.To investigate possible reasons for these differences, a mutationalsystem is needed in which the same target gene is used for comparisonin the same type of cells in vitro and in vivo. In the presentstudy, this was achieved by analysing at the molecular level35 hprt mutant rat fibroblast clones obtained from cell populationsexposed in vitro to ENU and comparing the mutational spectrumwith the previously determined spectrum of ENU-induced hprtmutants in the same target cells exposed in vivo. Twenty-eightmutants contained a single base pair alteration in the hprtcoding sequence. Most of these changes were found at AT basepairs (19/28), the AT to TA transversion being the most frequentkind of mutation (12/19), which is probably caused by O2-ethylthymine.Transversions at AT base pairs showed all mutated T's to belocated in the nontranscribed strand of the hprt gene, suggestinga strand specific fixation of mutations induced by O2-ethylthymine,which appears to be a general feature of ENU- and ENNG-inducedhprt mutations in mammalian cells. GC to AT transitions, probablycaused by O6-ethylguanine, were detected at a lower frequency(7/28). This in vitro mutational spectrum was very similar tothat of the same target cells exposed in vivo to ENU. A comparisonof the mutational spectra in AGT-proficient and AGT-deficientrodent cells exposed to ethylating agents showed that in contrastto the situation in AGT-proficient rat fibroblasts, GC to ATbase pair changes (and not AT to TA) are the predominant mutationsin AGT-deficient hamster cells.
4To whom correspondence should be addressed 相似文献
87.
Benjamin Volovitz Jacob Amir Hagit Malik Maya Lerman Itzhak Varsano 《The Journal of asthma》1994,31(1):27-34
Administration of theophylline to asthmatic children is frequently associated with an adverse influence on their behavior. The efficacy and behavioral effects of the administration of high-dose theophylline (T) and ketotifen (K) in various combinations were evaluated prospectively in a double-blind, placebo controlled study in 55 children with moderately severe perennial asthma. During a baseline period of 2 weeks, theophylline (serum level of 10-20 μg/ml) was administered to all the children. After this period the patients were randomly allocated into four comparable groups. The children were treated during a 12-week period with: T + K-Placebo (T group); T + K (T + K group); half-dose T + K (T/ 2 + K group); or placebo of both T and K (P group). During the 12-week treatment period, as compared to the baseline period, only the three groups of children who received active therapy (T + P, T + K, T/2 + K) showed a similar reduction in the number of days with asthmatic symptomatology, improvement of the total asthmatic symptoms score, and increased PEFR. The behavioral activity of the children (assessed by the Conner's rating scale) improved significantly only in the groups receiving placebo or T/2 + K. The results of this study suggest that a combination therapy of half the recommended therapeutic dose of theophylline with ketotifen can be clinically as effective as therapy with a full dose of theophylline, but with significantly less adverse behavioral effects. 相似文献
88.
A device called the Dex Frame has recently been marketed as an aid for children with specific learning difficulties. Using a test of reading speed and a test of reading accuracy we have attempted to evaluate the device. Two groups of children with learning difficulties were used, one having sole use of the device and being allowed to carry it with them and a second group who only used the device when attending for remedial tuition and assessment. The results show that no significant improvement occurred in reading performance of the groups with learning difficulties using the Dex Frame as compared with a control group. The teachers of the groups did, however, feel that on an individual basis some children (< 10%) expressed that they felt more comfortable using the device. 相似文献
89.
90.