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   4129篇
  免费   361篇
  国内免费   29篇
耳鼻咽喉   76篇
儿科学   138篇
妇产科学   80篇
基础医学   489篇
口腔科学   45篇
临床医学   293篇
内科学   853篇
皮肤病学   292篇
神经病学   262篇
特种医学   183篇
外科学   604篇
综合类   220篇
一般理论   6篇
预防医学   209篇
眼科学   101篇
药学   167篇
中国医学   16篇
肿瘤学   485篇
  2024年   6篇
  2023年   49篇
  2022年   62篇
  2021年   126篇
  2020年   88篇
  2019年   104篇
  2018年   120篇
  2017年   86篇
  2016年   111篇
  2015年   111篇
  2014年   139篇
  2013年   167篇
  2012年   264篇
  2011年   277篇
  2010年   121篇
  2009年   139篇
  2008年   193篇
  2007年   235篇
  2006年   244篇
  2005年   222篇
  2004年   200篇
  2003年   202篇
  2002年   186篇
  2001年   101篇
  2000年   111篇
  1999年   108篇
  1998年   47篇
  1997年   45篇
  1996年   37篇
  1995年   31篇
  1994年   46篇
  1993年   46篇
  1992年   58篇
  1991年   47篇
  1990年   42篇
  1989年   43篇
  1988年   39篇
  1987年   55篇
  1986年   42篇
  1985年   36篇
  1984年   27篇
  1983年   13篇
  1982年   10篇
  1980年   8篇
  1979年   14篇
  1978年   10篇
  1975年   5篇
  1974年   7篇
  1973年   8篇
  1967年   6篇
排序方式: 共有4519条查询结果,搜索用时 281 毫秒
1.
2.
Mucosal trypsin, a protease-activated receptor (PAR) stimulant, may have an endogenous bronchoprotective role on airway smooth muscle. To test this possibility the effects of lumenal trypsin on airway tone in segments of pig bronchus were tested. Bronchial segments from pigs were mounted in an organ chamber containing Kreb's solution. Contractions were assessed from isovolumetric lumen pressure induced by acetylcholine (ACh) or carbachol added to the adventitia. Trypsin, added to the airway lumen (300 microg x mL(-1)), had no immediate effect on smooth muscle tone but suppressed ACh-induced contractions after 60 min, for at least 3 h. Synthetic activating peptides (AP) for PAR1, PAR2 or PAR3 were without effect, but PAR4 AP caused rapid, weak suppression of contractions. Lumenal thrombin was without effect and did not prevent the effects of trypsin. Effects of trypsin were reduced by N(omega)-nitro-L-arginine methyl ester but not indomethacin. Trypsin, thrombin and PAR4 AP released prostaglandin E2. Adventitially, trypsin, thrombin and PAR4 AP (but not PAR2 AP) relaxed carbachol-toned airways after <3 min. The findings of this study show that trypsin causes delayed and persistent bronchoprotection by interacting with airway cells accessible from the lumen. The signalling mechanism may involve nitric oxide synthase but not prostanoids or protease-activated receptors.  相似文献   
3.
Neurosonography by advanced transvaginal sonography has revealed normal and abnormal intracranial morphology. Transvaginal 3D sonography demonstrates bony structures, multiplanar analysis of inside detailed morphology, tomographic ultrasound imaging in any cutting sections, 3D sonoangiography and volume calculation of ventricles and/or intracranial lesions. Longitudinal assessment of normal and abnormal CNS development is easy by serial scanning. However, the transvaginal approach has several limitations due to its observation by use of a high-frequency transducer from the fetal parietal region. Evaluation of the brainstem and posterior fossa, which are located far from the parietal ultrasound windows of the anterior fontanelle or sagittal suture, is sometimes hard by transvaginal sonography. Visualization of bilateral temporal areas is getting difficult with advanced gestational weeks because of bilateral acoustic shadows due to ossification of parietal bones. Demonstration of frontal/occipital areas is sometimes impossible in late pregnancy due to scan-angle limitation of the transvaginal transducer. From our experiences, the main difference between transvaginal 3D ultrasound and MRI is demonstration of the whole gyral and sulcal formation and brainstem in the late second and third trimesters. Although MRI is a useful modality which can compensate for pitfalls of transvaginal 3D ultrasound, 3D ultrasound is sometimes superior to MRI in detecting cysts in cyst and intracranial calcification. Transvaginal 3D ultrasound is much superior to MRI in detecting bony structures and angioarchitectonics and in volumetric assessment. Regarding objective and accurate prenatal diagnosis, any less-invasive modalities can be used. After considering each advantage and disadvantage of transvaginal 3D ultrasound and MR imaging, it is suggested to use the different technologies according to what is to be detected and evaluated.  相似文献   
4.
A total of 106 vascular reconstructions below the inguinal ligament including axillo-femoral and femoro-femoral bypasses were performed using 137 Dardik's human umbilical veins. The indication for surgery was limb salvage in 29%. The distal anastomosis was done with the popliteal artery above the knee in 53 cases, below the knee in 31, and with a tibial artery in 1. The axillo-femoral bypass was performed in 21 cases, and femoro-femoral bypass in 32. The accumulated graft patency rates of femoro-popliteal bypass at 1 yr./3 yrs./5 yrs. were 93%/75%/75%, those of femoro-femoral bypass were 85%/85%/85%, and those of axillo-femoral bypass were 54%/27%/27%. No special risk factor influencing patency rate was found from this study. In long term period, graft aneurysm was observed in 3 cases. It is concluded that the human umbilical vein is the graft material of choice for femoro-popliteal or femoro-femoral bypass when the saphenous vein is not available, and the careful follow-up is important because of the risk of graft aneurysm.  相似文献   
5.
6.
7.
Background and Objectives: The perception of pain is a personal experience influenced by many factors, including genetic, ethnic and cultural issues. Understanding these perceptions is especially important in dermatologic patients undergoing minor surgical operations and who often differ in their pain response to surgical treatments. Little is known about how these differences affect the perception of experimental pain. The purpose of this study was to determine experimental pain perception differences in three distinct East Asian ethnic populations.
Methods: Pain thresholds were examined with a psychophysical computerized quantitative thermal sensory testing device (TSA 2001) in healthy volunteers recruited from three different Asian ethnic groups. Using the methods of limits, experimental pain perception threshold was measured on the forehead and volar aspect of the forearm in 49 healthy subjects. The measurements were then repeated after skin barrier perturbation with adhesive tape stripping of the stratum corneum. All three ethnic groups were analyzed separately with respect to age, gender educational level and skin type.
Results: A total of 20 Chinese, 14 Malay and 15 Indian subjects completed the study. Thermal pain thresholds were similar in all three ethnic groups before and after tape strippings. No significant differences were noted between genders.
Conclusions: Using quantitative sensory thermal testing, we demonstrated that no significant differences in pain occur between different races and genders.  相似文献   
8.
9.
10.
D. Koh    C. L. Goh    H. T. W. Tan    S. K. Nge  W. K. Wong 《Contact dermatitis》1997,37(1):32-34
This study attempts to demonstrate the existence of allergic contact dermatitis from grass, and to develop a patch test series to screen patients with grass intolerance. 6 common grass species from lawns and military training areas were collected. Solvent extracts of polar. non-polar and volatile fractions were prepared and used for patch testing in 20 control subjects and 46 patients with a history of grass intolerance. The 20 control had negative responses to patch testing. 5 out of 46 patients had positive patch tests to Axonopus compressus (carpet grass). Ischaenmum muticum (sea-shore centipede grass). Imperata evlindrica (lalang). Panicum maximum (Guinea grass) and Pennisetum purpureum (elephant grass). Reactions to the non-polar fraction for all 5 species were noted. This study demonstrates the existence of allergic contact dermatitis from various common species of grass. In our series, this is seen in 11% of those with a history of grass intolerance.  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