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   5373篇
  免费   441篇
  国内免费   158篇
耳鼻咽喉   105篇
儿科学   106篇
妇产科学   29篇
基础医学   669篇
口腔科学   154篇
临床医学   534篇
内科学   791篇
皮肤病学   57篇
神经病学   735篇
特种医学   169篇
外科学   479篇
综合类   473篇
预防医学   598篇
眼科学   114篇
药学   640篇
  1篇
中国医学   181篇
肿瘤学   137篇
  2024年   11篇
  2023年   147篇
  2022年   223篇
  2021年   305篇
  2020年   264篇
  2019年   299篇
  2018年   268篇
  2017年   219篇
  2016年   177篇
  2015年   170篇
  2014年   330篇
  2013年   375篇
  2012年   234篇
  2011年   282篇
  2010年   208篇
  2009年   234篇
  2008年   230篇
  2007年   236篇
  2006年   194篇
  2005年   167篇
  2004年   153篇
  2003年   158篇
  2002年   99篇
  2001年   87篇
  2000年   67篇
  1999年   70篇
  1998年   43篇
  1997年   45篇
  1996年   57篇
  1995年   50篇
  1994年   47篇
  1993年   42篇
  1992年   49篇
  1991年   45篇
  1990年   41篇
  1989年   47篇
  1988年   32篇
  1987年   22篇
  1986年   33篇
  1985年   31篇
  1984年   29篇
  1983年   21篇
  1982年   22篇
  1981年   30篇
  1980年   18篇
  1979年   17篇
  1977年   8篇
  1976年   6篇
  1974年   10篇
  1972年   6篇
排序方式: 共有5972条查询结果,搜索用时 15 毫秒
51.
 The purpose of this study was to investigate the time course of skeletal muscle adaptations resulting from high-intensity, upper and lower body dynamic resistance training (WT). A group of 17 men and 20 women were recruited for WT, and 6 men and 7 women served as a control group. The WT group performed six dynamic resistance exercises to fatigue using 8–12 repetition maximum (RM). The subjects trained 3 days a week for 12 weeks. One-RM knee extension (KE) and chest press (CP) exercises were measured at baseline and at weeks 2, 4, 6, 8, and 12 for the WT group. Muscle thickness (MTH) was measured by ultrasound at eight anatomical sites. One-RM CP and KE strength had increased significantly at week 4 for the female WT group. For the men in the WT group, 1 RM had increased significantly at week 2 for KE and at week 6 for CP. The mean relative increases in KE and CP strength were 19% and 19% for the men and 19% and 27% for the women, respectively, after 12 weeks of WT. Resistance training elicited a significant increase in MTH of the chest and triceps muscles at week 6 in both sexes. There were non-significant trends for increases in quadriceps MTH for the WT groups. The relative increases in upper and lower body MTH were 12%–21% and 7%–9% in the men and 10%–31% and 7%–8% in the women respectively, after 12 weeks of WT. These results would suggest that increases in MTH in the upper body are greater and occur earlier compared to the lower extremity, during the first 12 weeks of a total body WT programme. The time-course and proportions of the increase in strength and MTH were similar for both the men and the women. Accepted: 6 September 1999  相似文献   
52.
A simple device for fluid exchange is described, which allows the exchange of an unlimited number of solutions at low (10–1000 nl/min) constant perfusion rate. The applicability of the system has been tested in microperfusion experiments of rat distal tubules. At a luminal perfusion rate of 40 nl/min, the lag time was some 20 sec and 80 % fluid exchange time some 3 sec. Simple modification allows further reduction of the lag time. Under control conditions, the potential difference across the late distal tubule (PDte) approaches –19.4±2.5 mV (n = 27). Increase of luminal potassium concentration from 5.4 to 40 mmol/l hyperpolanzes PDte to –29.9±4.3 mV (n = 8). Amiloride (10 mol/l) leads to a reversible depolarization to –3.2±1.0 mV (n = 19), barium (1 mmol/l) to a reversible hyperpolarization to –25.8±2.6 mV (n = 19). As expected, PDte is largely created by amiloride sensitive sodium channels and is partially blunted by barium sensitive potassium channels.  相似文献   
53.
41名肢残者十六项人格特质测验   总被引:1,自引:1,他引:1  
张丹 《中国心理卫生杂志》1989,3(6):248-249,271
应用“卡特尔十六项人格特质测验问卷”,对41名肢残者和40名健全人进行对照研究。结果表明,肢残人较健全人在孤独性上具有明显的差异,偏于缄默,固执,关注外界信息,具有一定的防卫倾向。肢残人富于实验性,较健全人更自由、激进、好学,具有较强的独立工作能力,希望生活更充实多彩。在各项能力水平上,肢残上与健全人没有显著差别。不同性别肢残人人格特质在敏感性上差异明显,女性较理智和着重现实,而男性则偏于敏感,易感情用事。  相似文献   
54.
The umbilical vascular bed of the rat placenta was perfused in situ. Ouabain (10–4M) in the perfusion fluid had no effect on the unidirectional flux of Na+ from the maternal (electrically negative) to the foetal (electrically positive) side of the placenta, or on the transplacental potential difference. This was taken to indicate that there is no significant active transport of Na+ across the placenta of the rat.  相似文献   
55.
he present study examined strain differences in the light-dark preference among four strains of rats. The test was done in the home-cage situation under 12L:12D cycles. Data from four strains were compared: BN/Kyo, BDIX/Nem, Wistar/Nu, and F344/NSlc. These strains differed in the light-dark preference measured by the ratio of the time spent in the field area of the home cage during the light period. BN/Kyo and BDIX/Nem spent the most time (approx. 23%) in the field during the light period, while F344/NSlc spent the least time (approx. 5%). Wistar/Nu fell between the two (approx. 12%).This study was conducted as partial fulfillment for the master's degree, submitted to Nagoya University by the first author. It was presented at the 47th Annual Conference of the Japanese Society of Animal Psychology.  相似文献   
56.
M. Eto    K. Watanabe  K. Ishii 《Clinical genetics》1986,30(5):422-427
We have examined the apo E phenotype frequencies in the Japanese population (n = 576, 16-78 years of age). Apo E phenotypes were determined by the rapid flat gel isoelectric focusing method that we previously reported. The apo E phenotype frequencies in the Japanese were 0.3% for E2/2, 6.1% for E3/2, 71.9% for E3/3, 0.7% for E4/2, 19.3% for E4/3 and 1.7% for E4/4. The apo E allele frequencies were 0.037, 0.846 and 0.117 for the epsilon 2, epsilon 3 and epsilon 4 alleles, respectively. These frequencies were compared with those in the Caucasian populations (n = 3033) reported by Sing & Davignon (1985). There was a significant difference in the apo E phenotype frequencies between the Japanese and Caucasian populations. In addition, a significantly lower frequency of the epsilon 2 and epsilon 4 alleles and a significantly higher frequency of the epsilon 3 allele were found in the Japanese than those reported for the Caucasian populations. It is concluded that there is a racial difference in the apo E allele frequencies between the Japanese and Caucasian populations.  相似文献   
57.
Summary Active ion transport in the colon is generating a transmucosal electrical potential difference (PD) of about 40 mV. Cathartic agents inhibit electrolyte and water net-absorption or cause net-secretion which should be reflected in a change of PD.In 83 normal subjects the effect of an isotonic eletrolyte solution (control) and different cathartic agents on rectal PD was tested: Laxatives (bisacodyl, rhein), bile acids (cholic and deoxycholic acid), fatty acids (oleic and ricinoleic acid) and cardiac glycosides (meproscillarin, digitoxin, digoxin). Bisacodyl, deoxycholic acid in high concentration, meproscillarin and digitoxin significantly decreased PD, while the other substances did not.Cathartics act on different transport mechanisms which together with different absorption characteristics of the proximal and distal colon may explain the difference in effecting the PD. Rectal PD measurement provides an easy and convenient tool to document effects of cathartic agents on electrolyte transport, otherwise difficult to obtain, and is applicable for clinical use.To Prof. Dr. H.P. Wolff on the occasion of his 65th birthday  相似文献   
58.
The lengths of the index finger (2D) and ring finger (4D) are sexually dimorphic in humans, and men have a smaller 2D:4D ratio compared to women. Prenatal androgens appear to be important in the development of the 2D:4D sex difference, since it has been reported in children as young as 2 years old, and since humans exposed to supernormal prenatal androgen levels display a smaller 2D:4D ratio. We tested whether another mammalian species in which the process of peripheral sexual differentiation is androgen‐dependent might also show a sex difference in digit ratios. The 2D:4D ratio of adult outbred mice was calculated for both the left and right rear paws. A sex difference was observed in the right rear paw: female mice had a larger 2D:4D ratio than did males. We also found this difference in prepubescent weanling mice. This sex difference is in the same direction as that observed in humans, and suggests that sexual dimorphism in digit length ratios is a feature common to many, if not all, mammals. The mouse may therefore be a useful animal model for studying the factors that influence finger length patterns, which have recently been correlated with several specific behaviors and disease predispositions in humans. Anat Rec 267:231–234, 2002. © 2002 Wiley‐Liss, Inc.  相似文献   
59.
目的 研究球形实体肿瘤中生理参数对药物输运的影响,以及探讨有较好效果的药物注射方式。方法 设肿瘤中毛细血管网成球对称分布,肿瘤中的毛细血管表面积和肿瘤体积之比为半径的函数。肿瘤间质为多孔介质,化学药物透过毛细血管壁进入肿瘤间质,在肿瘤间质中输运满足扩散方程。肿瘤外正常组织富含血管和淋巴,药物能被淋巴管吸收,药物输运采用改进的药代动力学模型。用肿瘤中各部位药物浓度维持在最小药物浓度MEC水平以上的时间曲线面积(AUC)来衡量药物的效果。结果 增大肿瘤间质中毛细血管对药物的通透性P,提高药物在肿瘤间质的扩散系数D,AUC的值均增大。在给出的六种给药方式中,分时段连续滴注和等时间间隔一次性注射的给药方式,它们的AUC值最大。结论 增大肿瘤间质中毛细血管对药物的通透性,提高药物在肿瘤间质的扩散系数,以及采用分时段连续滴注和等时间间隔一次性注射的给药方式,有利于肿瘤的治疗。  相似文献   
60.
Supernatants from Concanavalin A-stimulated murine spleen cells were subjected to hydrophobic interaction chromatography on phenyl-Sepharose. Macrophage cytotoxicity factor (MCF), macrophage migration inhibitory factor (MIF), T-helper cell-replacing factor (TRF) and colony-stimulating factor (CSF) were bound at high ionic strength and were released stepwise at low ionic strength. CSF thus could be separated from MCF, MIF and TRF and the bulk of other proteins. Chromatography of pools containing MCF, MIF and TRF on Sephadex did not lead to a separation of the three activities which were all found in a molecular weight range of 25.000-55.000. Isoelectric focusing of these pools in pH range from 4 to 9 gave two peaks for MCF at pH 8.2 and 7.2, whereas MIF activity focused from pH 4.5 to 5.5. TRF activity was found in a single sharp peak at pH 5.3. The results demonstrate that the four biological activities can be distinguished on a chemical basis and are accessible for purification and chemical characterization.  相似文献   
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