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   21170篇
  免费   1885篇
  国内免费   91篇
耳鼻咽喉   213篇
儿科学   542篇
妇产科学   495篇
基础医学   3187篇
口腔科学   943篇
临床医学   1931篇
内科学   4846篇
皮肤病学   518篇
神经病学   2066篇
特种医学   721篇
外科学   2709篇
综合类   109篇
一般理论   10篇
预防医学   1595篇
眼科学   354篇
药学   1329篇
中国医学   52篇
肿瘤学   1526篇
  2023年   172篇
  2022年   338篇
  2021年   722篇
  2020年   473篇
  2019年   660篇
  2018年   754篇
  2017年   583篇
  2016年   632篇
  2015年   661篇
  2014年   877篇
  2013年   1028篇
  2012年   1528篇
  2011年   1429篇
  2010年   906篇
  2009年   788篇
  2008年   1189篇
  2007年   1219篇
  2006年   1118篇
  2005年   1072篇
  2004年   911篇
  2003年   837篇
  2002年   732篇
  2001年   412篇
  2000年   362篇
  1999年   398篇
  1998年   185篇
  1997年   176篇
  1996年   132篇
  1995年   130篇
  1994年   114篇
  1993年   105篇
  1992年   253篇
  1991年   219篇
  1990年   186篇
  1989年   204篇
  1988年   178篇
  1987年   153篇
  1986年   161篇
  1985年   159篇
  1984年   113篇
  1983年   92篇
  1982年   52篇
  1981年   56篇
  1979年   73篇
  1978年   59篇
  1976年   46篇
  1975年   50篇
  1974年   40篇
  1973年   55篇
  1972年   46篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
101.
High altitude residence is known to modify body biochemistry and hormone status. However, the effects of such a sojourn on these status observed at sea level both immediately and later after return are not as well established as are the effects of an intermittent acclimation. The aim of this study was therefore to investigate these changes. To achieve our objectives, nine subjects received intermittent acclimation at low pressure in a barometric chamber (8?h daily for 5 days, day 1 at 4500 m, day 5 at 8500 m) before an expedition to the Himalayas. Hormonal and biochemical changes were studied using samples of venous blood taken at sea level before and after acclimation, after return from the expedition and 1 and 2 months after descent. Concentrations of thyroid hormones, adrenaline, noradrenaline (NA), hormones of hydromineral metabolism (aldosterone, renin, arginine vasopressin, atrial natriuretic peptide) as well as prolactin, cortisol, insulin and endothelin 1 were measured. Biochemical measurements made were plasma osmolality, and concentrations of glucose, total cholesterol, total proteins, pre-albumin, transferrin, complement 3C, apolipoproteins A1 and B and serum iron. Acclimation induced no alteration in hormone (except for NA with increases of about 1.5, fold P<0.05) and biochemistry data. After the expedition, hormone responses were characterized by a higher total triidothyronine concentration (+18%, P<0.05) while other hormones did not vary. A linear relationship was found between thyroid-stimulating-hormone and body mass changes after the expedition (r=0.67, P<0.05). The observed increased concentrations of plasma proteins and total cholesterol (P<0.05) could be related to the restoration of lean body mass. At 1 and 2 months after return, no changes in hormones were observed but a significant decrease in transferrin concentration was noticed. The higher serum iron concentration reported after 1 month (P<0.05) could have been the result of a physiological haemolysis. It was concluded that both acclimation and the expedition in the Himalayas affected hormone status and body biochemistry status even though the observed changes were slight and rapidly reversed.  相似文献   
102.
In order to determine the seroprevalence of hepatitis E virus, 1,993 sera (453 from healthy pregnant women, 491 from Moroccan subjects, 492 from blood donors, 321 from children, and 236 from intravenous drug users) were studied. IgG was measured by enzyme immunoassay (EIA), and positive results were confirmed by Western blot. The EIA detected antibodies in 3.96 % of the subjects (5.6 % of the Moroccans and drug users and 1.8 % of the children). Fifty-four percent of these results were confirmed by Western blot, 11.4 % were found to be negative, and 34.2 % indeterminate. The overall prevalence after confirmation by Western blot decreased to 2.15 %. When studying the Western blot pattern of the positive samples, 95 % showed antibodies to SG-3, 65 % to 8–5, and only 9.3 % to CKS fusion protein. In the indeterminate Western blots, the results for these proteins were 96.3 %, 62.9 %, and 37 %, respectively. When the epidemiological data were analysed, no statistically significant differences between women and men or between different age groups were found.  相似文献   
103.
104.
105.
Summary: Purpose: A prospective series of 643 persons with epilepsy attending a reference neurologic center in Medellin, Colombia, was examined by computed tomography (CT scan) or serology or both with the enzyme-linked immunoelectrotransfer blot assay (EITB) to assess the prevalence of Taenia solium cysticercosis. Methods: All presenting patients were consecutively enrolled in the study. Five hundred forty-six persons underwent cerebral CT scans; 376 of them also had serum EITB performed. Results: Prevalence of neurocys@ercosis by CT scan was 13.92%. Overall prevalence of T. solium antibodies with EITB was 9.82%, but for those with late-onset epilepsy (onset after age 30 years), prevalence increased to 17.5% and 19% for those who originated from outside urban Medellin. Seroprevalence in individuals with mixed lesions (cysts and calcifications) was 88.2% and 64.10% in those with live cysts. Conversely, only 2.72% of persons with CT findings not related to neurocysticercosis had positive EITB tests. Conclusions: Our study shows that an important proportion of individuals with epilepsy have radiologic or serologic evidence of T. solium infection, suggesting that neurocysticercosis is an important etiology for epilepsy in Colombia.  相似文献   
106.
Krenn L  Jambrits M  Kopp B 《Planta medica》1988,54(3):227-232
For the first time the composition of the bufadienolide complex in URGINEA HESPERIA Webb & Berth. has been investigated. From an extract of lyophilized plants, thirteen bufadienolides were isolated. By means of FAB-MS, (1)H-NMR, and (13)C-NMR studies the compounds were structurally elucidated as scillarenin, scilliphaeosidin, scillarenin-3- O-alpha- L-rhamnoside, scilliphaeosidin-3- O-alpha- L-rhamnoside, gamabufotalin-3- O-alpha- L-rhamnoside, 11alpha-hydroxyscilliglaucosidin-3- O-alpha- L-rhamnoside, scillarenin-3- O-alpha- L-2',3'-diacetylrhamnosido-4'-beta- D-glucoside, scillarenin-3- O-alpha- L-rhamnosido-4'-beta- D-glucosido-3'-beta- D-glucoside, scillarenin-3- O-alpha- L-rhamnosido-4'-beta- D-glucosido-4'-beta- D-glucoside, scillarenin-3- O-alpha- L-2',3'-diacetylrhamnosido-4'-beta- D-glucosido-3'-beta- D-glucoside, scillarenin-3- O-alpha- L-2',3'-diacetylrhamnosido-4'-beta- D-glucosido-4'-beta- D-glucoside, scilliphaeosidin-3- O-alpha- L-rhamnosido-4'-beta- D-glucosido-3'-beta- D-glucoside, and scilliphaeosidin-3- O-alpha- L-rhamnosido-4'-beta- D-glucosido-4'-beta- D-glucoside.  相似文献   
107.
A comparative statistical analysis of "synaptic ribbons" evolution over a 24 hour period during two different photoluminous seasons (September, and winter) is carried out. Seventy male rats were used. Statistical analysis involved the Kolmogorov-Smirnov test, variance analysis, the Student t-test and Pearson's correlation test. The results show that "synaptic ribbons" evolve during the circadian phase and through two different seasons, with a clear and marked influence of point-time (p < 0.0001) and season (p < 0.0001).  相似文献   
108.
Blood rheological properties were studied in 21 patients suffering from essential hypertension (EHT), degree I-II according to WHO criteria. These patients were diagnosed "de novo". The whole blood filterability (WBF), blood viscosity (BV) at 230 s-1 and 23 s-1, red cell deformability (FI), erythrocyte aggregation in autologous (MEA) and normal plasma (MEAc), fibrinogen (Fbg) and hematocrit (Ht) have been evaluated. In the hypertensive patients we have found decreased WBF, greater BV and FI in comparison with the control group (p less than 0.001). Likewise, MEA and Fbg were increased, though the differences were less significant (p less than 0.01). The evaluation of Ht did not show any differences between the two groups. The results suggest that in the newly diagnosed EHT, clear hemorheological alterations occur, both in plasma and in the erythrocytes, which could play a role in the pathogenesis of the aforementioned disease.  相似文献   
109.
We report a free-floating left atrial thrombus detected by 2-dimensional echocardiography in a patient with hypertrophic cardiomyopathy. Two-dimensional echocardiography permitted definitive diagnosis, thereby indicating emergency cardiac surgery. To our knowledge, this is the first reported detection of a free-floating left atrial thrombus by 2-dimensional echocardiography in a patient with hypertrophic cardiomyopathy.  相似文献   
110.
In this article, the authors present an analysis of causes of death in Spain and Portugal in 1984 based on a calculation of the "years of potential life lost" (YPLL) between the first and the 70th birthdays, the latter age corresponding approximately to the average life expectancy in both countries. This analysis of the YPLL led to a substantially different ranking of the main causes of death, based on what might be termed "premature mortality" compared with that obtained from more conventional mortality indices. According to this criterion, which is especially appropriate for the planning and evaluation of health interventions, the main causes of premature death (1-69 years) in the two countries of the Iberian peninsula are malignant tumours and, particularly in Portugal, violent deaths (especially motor-vehicle accidents, but also suicides). This is in contrast to the predominance of cardiovascular diseases indicated by other weightings of age-specific mortality rates. Portugal shows significantly worse YPLL rates than Spain not only for general mortality (45% higher than in Spain), but also for several major groups of causes. In Spain only malignant neoplasms, diabetes and chronic rheumatic heart diseases show higher specific mortality rates than in Portugal, based on traditional mortality indicators.(ABSTRACT TRUNCATED AT 250 WORDS)  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