首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   237074篇
  免费   15600篇
  国内免费   991篇
耳鼻咽喉   2571篇
儿科学   6043篇
妇产科学   4442篇
基础医学   29703篇
口腔科学   4383篇
临床医学   24484篇
内科学   49824篇
皮肤病学   3348篇
神经病学   23828篇
特种医学   10169篇
外国民族医学   13篇
外科学   37526篇
综合类   2631篇
现状与发展   1篇
一般理论   178篇
预防医学   16735篇
眼科学   5547篇
药学   15615篇
  1篇
中国医学   319篇
肿瘤学   16304篇
  2023年   1242篇
  2022年   1856篇
  2021年   5358篇
  2020年   3062篇
  2019年   5091篇
  2018年   6097篇
  2017年   4484篇
  2016年   4889篇
  2015年   5754篇
  2014年   8391篇
  2013年   11332篇
  2012年   17419篇
  2011年   18144篇
  2010年   10150篇
  2009年   9398篇
  2008年   16012篇
  2007年   16787篇
  2006年   16334篇
  2005年   16192篇
  2004年   15227篇
  2003年   13927篇
  2002年   13306篇
  2001年   2029篇
  2000年   1538篇
  1999年   2107篇
  1998年   2820篇
  1997年   2236篇
  1996年   1960篇
  1995年   1787篇
  1994年   1549篇
  1993年   1525篇
  1992年   1069篇
  1991年   991篇
  1990年   854篇
  1989年   793篇
  1988年   737篇
  1987年   664篇
  1986年   690篇
  1985年   725篇
  1984年   950篇
  1983年   824篇
  1982年   1057篇
  1981年   994篇
  1980年   852篇
  1979年   503篇
  1978年   535篇
  1977年   469篇
  1976年   435篇
  1975年   324篇
  1974年   329篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Background: Intervention trials with self-selected participants have shown that mailed stage-targeted print materials can increase participation in physical activity in the short term. We examined the effects of a mailed stage-targeted print intervention designed to promote physical activity, in a random sample of adults living in a regional city.Method: Participants (n = 462, 40–60 years of age) were randomly allocated to an intervention in - 227) or control group (n - 235). Measures included validated 2-week physical activity recall and stage of motivational readiness for physical activity. The intervention consisted of a single mailing of a letter and full-color stage-targeted booklets (specific to precontemplation, contemplation, preparation, and action/maintenance) 1 week postbaseline. Follow-up interviews were conducted at 2 and 6 months postbaseline.Results: After 2 months, participants in the intervention group were significantly More likely to meet the current American College of Sports Medicine/Centers for Disease Control and Prevention recommendation for sufficient physical activity than those in the control group (adjusted odds ratio [OR] - 2.40; 95% confidence interval [CI] = 1.44–3.99). After 6 months, intervention participants who reported receiving and reading the intervention materials were significantly more likely to be meeting the sufficient physical activity criterion compared with the control group (adjusted OR = 2.03; 95% Cl = 1.16–3.56).Conclusions: The stage-targeted print intervention was effective in promoting short-term increases in physical activity and was most effective for participants who recognized and used the materials. This low-cost, generalizable intervention has demonstrated potential as a practical population-based physical activity promotion strategy. Further research is required before widespread dissemination would be justified, as additional strategies may be required to ensure sustained change. This project was supported by a National Heart Foundation of Australia Research Project Grant. David Crawford was supported by a Nutrition Research fellowship from the National Heart Foundation.  相似文献   
993.
994.
Summary The BTA Test is an adjunctive test for the diagnosis and management of bladder cancer. For estimation of its potential in the management of patients with transitional-cell cancer (TCC) a review of published results was undertaken. Three prospective studies were analyzed, in which a total of 699 patients with a history of TCC were enrolled. The BTA Test was performed on voided urine and compared with either voided-urine or bladder-wash cytologic analysis in a blinded fashion. In all three studies the sensitivity of the BTA Test was more than double that of cytology, irrespective of whether the cytologic analysis was performed on voided or bladder-wash samples. The third study also included an additional 225 patients undergoing evaluation for hematuria, and TCC was found in 67 cases. The BTA Test detected 70% of these tumors, whereas cytology detected only 25%. The BTA Test is a simple, rapid test that can diagnose a substantial percentage of patients having new or recurrent bladder TCC. Its complete role in the management of such patients remains to be defined.  相似文献   
995.
A new dual-energy x-ray CT algorithm is presented which makes use of both pre- and post-reconstruction data in an iterative manner to achieve accurate beam hardening correction and decomposition into basis materials. The technique does not require a calibration phantom and also does not require accurate estimation of the effective energies of the polyenergetic x-ray beams. It does however, require a knowledge of the incident x-ray spectra. For the situation where the incident spectra are unknown, a method is given whereby sufficiently accurate approximations to the spectra can be determined from attenuation measurements. Decomposition into basis materials makes use of spatial and energy information and an 'a priori' knowledge of the composition and attenuating properties of various tissue types. Any total number of basis materials may be used within the limitation that a subset containing a maximum of three materials is used for any individual pixel. Results of a computer simulation show that the algorithm produces accurate measurements of the concentrations of both high and low atomic number materials such as bone mineral, collagen, fat and air. However the results of a phantom study show that the measurement of the concentrations of low atomic number basis materials may be subject to systematic errors arising from uncertainties in the published values of linear attenuation coefficients.  相似文献   
996.
Previous studies in the MPTP-lesioned primate model of Parkinson's disease have demonstrated that alpha(2) adrenergic receptor antagonists such as idazoxan, rauwolscine, and yohimbine can alleviate L-dopa-induced dyskinesia and, in the case of idazoxan, enhance the duration of anti-parkinsonian action of L-dopa. Here we describe a novel alpha(2) antagonist, fipamezole (JP-1730), which has high affinity at human alpha(2A) (K(i), 9.2 nM), alpha(2B) (17 nM), and alpha(2C) (55 nM) receptors. In functional assays, the potent antagonist properties of JP-1730 were demonstrated by its ability to reduce adrenaline-induced (35)S-GTPgammaS binding with K(B) values of 8.4 nM, 16 nM, 4.7 nM at human alpha(2A), alpha(2B), and alpha(2C) receptors, respectively. Assessment of the ability of JP-1730 to bind to a range of 30 other binding sites showed that JP-1730 also had moderate affinity at histamine H1 and H3 receptors and the serotonin (5-HT) transporter (IC(50) 100 nM to 1 microM). In the MPTP-lesioned marmoset, JP-1730 (10 mg/kg) significantly reduced L-dopa-induced dyskinesia without compromising the anti-parkinsonian action of L-dopa. The duration of action of the combination of L-dopa and JP-1730 (10 mg/kg) was 66% greater than that of L-dopa alone. These data suggest that JP-1730 is a potent alpha(2) adrenergic receptor antagonist with potential as an anti-dyskinetic agent in the treatment of Parkinson's disease.  相似文献   
997.
Discovery of a postlumbosacral discectomy fistula between the right iliac artery and vein was obscured by an associated severe stricture of the infrarenal inferior vena cava in a 49-year-old man. During venous stenting for treatment of peripheral edema, the fistula was suspected because of faint pulsatile right iliac vein flow and increased O2 saturation of the venous blood. The suspicion was confirmed on subsequent iliac arteriography. Surgical closure of the fistula with arterial interposition grafting was then performed. The patient improved substantially.  相似文献   
998.
The dissolution rates of sparingly soluble, fine particulate, suspended drugs have been studied using a Coulter Counter Model TAII. For two sieve fractions of oxazepam the dissolution rates were monitored in media with varying viscosities brought about by the addition of glycerol, while for griseofulvin the change in the medium's viscosity was induced by changing the temperature. By calculating the dissolution rate, and compensating for differences in particle surface area and media solubility, it was shown that the dissolution rate was diffusion controlled. After additional normalization for the diffusion coefficient, it was suggested that the so-called apparent diffusional distance decreased substantially with particle size. The effect of particle size was more limited above approx. 15 μm.  相似文献   
999.
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号