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   379343篇
  免费   24922篇
  国内免费   2804篇
耳鼻咽喉   5197篇
儿科学   8276篇
妇产科学   10104篇
基础医学   53213篇
口腔科学   11788篇
临床医学   30204篇
内科学   78458篇
皮肤病学   8619篇
神经病学   27344篇
特种医学   13963篇
外国民族医学   82篇
外科学   60777篇
综合类   9963篇
现状与发展   1篇
一般理论   64篇
预防医学   17457篇
眼科学   9442篇
药学   31009篇
  1篇
中国医学   2192篇
肿瘤学   28915篇
  2021年   2619篇
  2019年   2734篇
  2018年   4533篇
  2017年   3450篇
  2016年   3542篇
  2015年   4058篇
  2014年   5717篇
  2013年   7403篇
  2012年   10075篇
  2011年   10272篇
  2010年   6222篇
  2009年   5884篇
  2008年   9501篇
  2007年   10334篇
  2006年   10267篇
  2005年   9312篇
  2004年   8833篇
  2003年   8563篇
  2002年   8216篇
  2001年   28311篇
  2000年   28826篇
  1999年   23692篇
  1998年   5168篇
  1997年   4256篇
  1996年   3829篇
  1995年   3482篇
  1994年   3106篇
  1993年   2847篇
  1992年   16062篇
  1991年   14828篇
  1990年   14172篇
  1989年   13982篇
  1988年   12603篇
  1987年   12077篇
  1986年   11126篇
  1985年   10336篇
  1984年   6923篇
  1983年   5615篇
  1982年   2722篇
  1979年   5489篇
  1978年   3356篇
  1977年   2977篇
  1975年   2647篇
  1974年   3076篇
  1973年   2873篇
  1972年   2836篇
  1971年   2778篇
  1970年   2518篇
  1969年   2553篇
  1968年   2253篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
102.
103.
104.
105.
Opportunistic infections in the oral cavity of the elderly may increase the incidence of systemic disease. The objective of this study was to investigate the differences in the oral bacterial flora between dependent elderly (inpatients) and independent elderly (community-dwelling residents). After multiple variables were taken into account, inpatients had significantly lower detection rates than community-dwelling residents for alpha-streptococci (p < 0.001) and Neisseria (p 0.004), and higher detection rates for Pseudomonas aeruginosa (p 0.024), methicillin-resistant Staphylococcus aureus (MRSA) (p 0.011) and Actinomyces spp. (p 0.005). Among inpatients, the requirement for a high degree of care was related negatively to detection of alpha-streptococci, but was related significantly to detection of P. aeruginosa (p 0.018) or MRSA (p 0.004). Tube-fed inpatients had a significantly lower detection rate for alpha-streptococci (p 0.041) and a higher detection rate for P. aeruginosa (p 0.004) than those who did not require tube feeding. Inpatients with a history of antibiotic use had a significantly lower detection rate for alpha-streptococci (p 0.049) and a higher detection rate for MRSA (p 0.007) than those without a history of antibiotic use. The detection rates for P. aeruginosa or MRSA in inpatients without alpha-streptococci were higher than in inpatients with alpha-streptococci after controlling for age and gender (P. aeruginosa, p 0.006; MRSA, p 0.001). Overall, detection of alpha-streptococci had an inverse correlation with the detection of P. aeruginosa and MRSA in the oral cavity and is likely to be an indicator of pathogenic bacterial infection.  相似文献   
106.
In order to assess the state and pathology of the woman's pelvis minor, a number of methods are commonly used among practitioners, encompassing clinical exploration, radiology, MRN, urodynamics, endoscopy and echography.

Echography has been poorly used in clinical pelvic exploration and its reliability is actually a matter of controversy 1. However, echographic surveys can provide us with valuable gynecological data on the state and pathologies of the soft pelvis, within the genital regions or even going beyond them, i.e. the rectal channel, bladder, urethra, anus, vascular plexuses, and all of their supporting tissues.

At our research unit, we have been employing Transvaginal Ultrasound echography (TVU) for a long time in conjunction with other pelvis-focused methods in order to study different kinds of pelvic alterations. TVU has proven to be friendly to use, fast, harmless and inexpensive, allowing serial explorations and producing high-quality dynamic images (loop-cinema, video-tape). Furthermore, this method is fairly aseptic in that the occurrence of faeces in the rectal ampolla is not a nuisance but a bonus in tracking the contours of the rectum walls and other topographical features which would be otherwise difficult to survey.

A complete pelvic floor TVU may add no longer than 5-8 minutes to a routine gynecological examination, can be implemented by the general gynecologist and generates data that can be further studied by the appropriate specialist for a more insightful evaluation 2.  相似文献   
107.
Radiological lymphography presents drawbacks among which the risk of aggravation of the edema is most prominent. The authors report their experience with isotopic lymphography which best reproduces the physiological conditions of lymphatic drainage; it provides informations on the dermal or canalicular drainage route, the possible peripheral stasis or lymph leakage.  相似文献   
108.
In order to study the biological activity of endogenous digitalis-like substance (DLS) and Na-K-ATPase inhibitor (ATPI), human urine was partially purified and administered to rats, and its effects on the urinary volume, urinary Na excretion and blood pressure (BP) were determined. In addition, the effect on myocardial Na-K-ATPase activity was also measured. After the extraction of 40L of urine with a reversed phase cartridge column (S-fraction), 20 ml of chloroform was added and extraction was repeated. The chloroform layer was applied to an open silica gel column, and at a fraction with ethylacetate: methanol (60: 40, T-1 fraction), DLS and ATPI were eluted at the highest concentration. The water layer was treated with charcoal (D-1 fraction). The acute administration of K-1, T-1 fraction to rats in vivo caused significant rises in urinary volume, urinary Na excretion and BP. In chronic administration of K-1 fraction, urinary Na excretion was significantly elevated and myocardial Na-K-ATPase activity was also significantly suppressed. These results suggest that DLS and ATPI cause increase in the urinary volume and urinary Na excretion and also possess a hypertensive action; and moreover, these substance may affect the heart like cardiotonic steroids and regulate BP by increasing cardiac contractility.  相似文献   
109.
We reported on the unusually high isotope effect of non-aromatizing androgen 19-hydroxylase in sheep and dog adrenals and the validity of the [3H] water method using [19-3H3] androgen. We have extended the study to examine whether this 19-hydroxylation is catalyzed by a cytochrome P-450 dependent enzyme. Sheep adrenal homogenate (1.65 mg prot.) was incubated in the presence of NADPH (5.6mM) with [19-3H3, 4-14C]-androstenedione (A) (3.2 microM, 8.24 x 10(4) dpm 3H/micrograms, 3H/14C = 17.2) in a total of 1.2 ml PO4 buffer under air at pH 7.4 for 2, 5 and 10 min. [19-3H2, 4-14C]-19-hydroxy-A (19-OHA) with added carrier was purified through extraction, TLC, acetylation to form 19-AcOA, and further TLC to give 19-hydroxylase activity as assessed by the product isolation method. Simultaneously, the [3H] water was measured by distillation, and with correction by the apparent kinetic isotope effect (KH/KT = 11.8), used for assessment of 19-hydroxylase activity. The effects on the hydroxylation by cofactor (NADPH, NADH), incubation atmosphere (N2, CO/O2), cytochrome P-450 inhibitors (metyrapone, clotrimazole) and heating were measured by both methods. Compared to the complete system (89.6pmol/min/mg as 100%), carbon monoxide suppressed 15.8, 59.3 and 86.4% of the 19-hydroxylation when a CO/O2 ratio of 0.1, 1 and 9 was used, respectively. Replacement to nitrogen atmosphere decreased the activity by 93.8%. Replacement of NADPH with NADH (7.5mM) caused more than a 92.1% decrease in activity. Metyrapone at 50 and 200 microM and and clotrimazole at 2.5 and 10 microM suppressed the activity by 82.8, 90.4, 85.4 and 94.9%, respectively. A larger scale sheep adrenal incubation of A (250 microM) under 18O2 atmosphere and isolation of 19-AcOA were carried out in a similar manner. The gas chromatography-mass spectrometry analysis of the purified product showed 48.5% of the product to be 18O-labeled as [M+ + 2], m/e 346. Thus, the non-aromatizing androgen 19-hydroxylase requires NADPH and molecular oxygen. It is strongly inhibited by carbon monoxide and cytochrome P-450 inhibitors. These results indicate that the enzyme system responsible for non-aromatizing androgen 19-hydroxylase in adrenal is a cytochrome P-450 dependent monooxygenase.  相似文献   
110.
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