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   76996篇
  免费   5708篇
  国内免费   636篇
耳鼻咽喉   1342篇
儿科学   1438篇
妇产科学   1335篇
基础医学   12127篇
口腔科学   1772篇
临床医学   7154篇
内科学   15077篇
皮肤病学   2520篇
神经病学   6419篇
特种医学   4235篇
外科学   9456篇
综合类   667篇
现状与发展   4篇
一般理论   23篇
预防医学   4514篇
眼科学   1878篇
药学   6628篇
中国医学   776篇
肿瘤学   5975篇
  2023年   507篇
  2022年   1451篇
  2021年   2371篇
  2020年   1299篇
  2019年   1848篇
  2018年   2157篇
  2017年   1705篇
  2016年   2494篇
  2015年   3162篇
  2014年   3646篇
  2013年   4297篇
  2012年   6209篇
  2011年   5885篇
  2010年   3571篇
  2009年   2904篇
  2008年   4194篇
  2007年   3983篇
  2006年   3540篇
  2005年   3409篇
  2004年   2888篇
  2003年   2520篇
  2002年   2291篇
  2001年   1468篇
  2000年   1420篇
  1999年   1189篇
  1998年   524篇
  1997年   467篇
  1996年   379篇
  1995年   355篇
  1994年   317篇
  1993年   328篇
  1992年   724篇
  1991年   781篇
  1990年   654篇
  1989年   701篇
  1988年   684篇
  1987年   659篇
  1986年   579篇
  1985年   566篇
  1984年   433篇
  1983年   365篇
  1982年   272篇
  1981年   249篇
  1980年   227篇
  1979年   360篇
  1978年   296篇
  1977年   210篇
  1974年   234篇
  1973年   247篇
  1972年   217篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
We studied 32 patients with winter seasonal affective disorder (SAD) in a counterbalanced crossover design comparing 1 h of morning light treatment (about 7000 lux) to 1 h of morning placebo treatment (deactivated negative ion generator). Both treatments significantly reduced depression ratings, but there was no difference between the antidepressant response to light and to placebo. Several possible explanations for this result were discussed including an inadequate 'dose' of light (e.g., ineffective duration or intensity), an unusual sample of patients, and a placebo mechanism.  相似文献   
93.
OBJECTIVE: Patients on L-thyroxine with a 'suppressed' TSH (< 0.05 mU/l) were compared to those in whom TSH was detectable but not elevated (0.05-4.0 mU/l), with regard to morbidity data. DESIGN: Biochemical data from Tayside Thyroid Register was matched to hospital admissions data obtained from Health Board Statistics. PATIENTS: The patients were identified from those registered on the computerized Tayside Register. MEASUREMENTS: Serum T4 and TSH assays, clinical assessment scores, and admission records with regard to ischaemic heart disease, overall fractures, fractured neck of femur and breast carcinoma. RESULTS: Over one year, 1180 patients on thyroxine replacement had clinical and biochemical assessment; 59% had a suppressed TSH and 38% 'normal' TSH. Patients with a suppressed TSH exhibited higher median serum thyroxine levels (146 nmol/l, range 77-252 vs 119 nmol/l, 58-224; P < 0.001). Patients under the age of 65 years on L-thyroxine had an increased risk of ischaemic heart disease compared to the general population (female 2.7 vs 0.7%, P < 0.001; male 6.4 vs 1.7%, P < 0.01), but the risk was no different between those with suppressed and normal TSH. There was no increase in risk for overall fracture, fractured neck of femur or breast carcinoma in those on thyroxine with suppressed or normal TSH. CONCLUSION: Patients under the age of 65 years on L-thyroxine had an increased risk of ischaemic heart disease. There was no excess of fractures in patients on L-thyroxine even if the TSH is suppressed.  相似文献   
94.
95.
To assess the effect of stimulus correlated motion on the appearance of functional magnetic resonance images, conventional visual and motor protocols were each performed by four normal volunteers and an image co-registration technique was used to retrospectively monitor subject motion. In three studies synthetic data sets were constructed from single baseline images using the positional information obtained from the co-registration procedure. Cumulative difference images were then created from both the synthetic and functional image sets. Stimulus correlated motion was detected in all eight studies and the synthetic cumulative difference images showed striking similarities to the equivalent functional images in each case.  相似文献   
96.

Background  

Many studies have found socioeconomic differentials in cancer survival. Previous studies have generally demonstrated poorer cancer survival with decreasing socioeconomic status but mostly used only ecological measures of status and analytical methods estimating simple survival. This study investigate socio-economic differentials in cancer survival using four indicators of socioeconomic status; three individual and one ecological. It uses a relative survival method which gives a measure of excess mortality due to cancer.  相似文献   
97.
3-Monochloro-1,2-propanediol (MCPD) is a well-known by-product of acid-hydrolyzed soy sauce during its manufacturing process. MCPD has been reported genotoxic in vitro, and reproductive toxicity and carcinogenicity in rats. To evaluate the immunomodulatory effect of MCPD on murine splenocyte and macrophage in vitro, we investigated splenocyte blastogenesis by concanavalin A (Con A), anti-CD3, and lipopolyssacharide (LPS), the production of cytokines from splenocyte, and the activity of mouse peritoneal macrophages. There was a significant decrease in lymphocyte blastogenesis to Con A or anti-CD3 at subtoxic dose of MCPD. A significant decrease in splenocyte blastogenesis to LPS was also observed. The production level of interferon (IFN)-gamma on splenocyte culture with Con A was significantly reduced at the higher concentration than 1.0mM of MCPD. The levels of interleukin (IL)-4 and IL-10 were also decreased at high concentrations of MCPD. There was a significant decrease in production of nitric oxide (NO) by peritoneal macrophages treated with MCPD. MCPD also inhibits tumor necrosis factor (TNF)-alpha production of stimulated macrophages. These results indicate that MCPD might be able to reduce the functionality of lymphocytes and peritoneal macrophages in vitro.  相似文献   
98.
Effects of sodium salts of various monovalent inorganic anions on transdermal permeation of salicylic acid were investigated. In in-vitro experiment using a Franz-type diffusion cell and excised mouse skin, the permeation-enhancing activities of the sodium salts of inorganic anions were roughly proportional to lyotropic Hofmeister swelling abilities of the anions; F?<SO4 2?<Cl? <ClO4 ?<NO3 <SCN? <Br <I?, i.e. l, Br and SCN increased the flux of drugs through the mouse skin, while F?, SO4 2?, Cl?, ClO4 ? and NO3 ? decreased or did not affect the flux. In invivo experiment using the rabbit as the test animal, the plasma concentration of salicylic acid of the rabbit to which 10%-salicylic acid ointment containing 5%-Nal or NaBr was applied was significantly higher than that of the rabbit to which the ointment without the electrolytes was applied. The amounts of sterol leached out of stratum corneum sheet when the sheet was immersed in aqueous solutions of Nal, NaBr, or NaSCN were much more than that of stratum corneum immersed in aqueous solutions of the other inorganic anions. The FTIR/ATR spectroscopy showed that the peaks at 2853 cm?1 and 2924 cm?1 in the IR absorption spectrum of the stratum corneum sheet of the mouse were shifted to higher frequencies by the anions which enhanced the transdermal drug permeation, while not shifted by the anions which did not have any permeation-enhancing activities or have permeation-reducing activities. These results suggest that sodium salts of some anions such as iodide, bromide and thiocyanate enhance transdermal permeation of salicylic acid through swelling and perturbation of the skin structure by these anions.  相似文献   
99.
A 20-yr-old black male was admitted with a 5-month history of profound weight loss and diarrhea. Appetite and dietary intake had been remarkably well preserved up until the week before admission. The severity of his depletion was evidenced by a body weight of only 38% of standard, multiple electrolyte deficiencies, and reduced metabolic expenditure, protein turnover, protein synthesis, and pancreatic function. Immunological defects included diminished lymphocyte numbers, lymphocyte transformation, gamma-globulin concentration, and cell-mediated immunity. A diagnosis of alpha-heavy chain disease (alpha-HCD) was made on endoscopic duodenal biopsy and serology--lymphoma being excluded by scanning and laparotomy. Treatment consisted initially of intravenous nutrition (because of the extreme malnutrition, severe diarrhea, and malabsorption of fluid, electrolytes, carbohydrates, and fat) and oral tetracycline. Response was dramatic, with a doubling of body weight within 6 wk, and resolution of malabsorption. He was discharged on a normal diet and long-term oral tetracycline (250 mg/day), and at 1-yr follow-up, nutritional status and gut function were normal despite persistence of duodenal mucosal abnormalities and markers of alpha-HCD and bacterial overgrowth. These results suggest that the malabsorption initially identified in this patient was not due simply to the mucosal abnormalities that characterize alpha-HCD, but was more a consequence of the superimposition of nutrient maldigestion and absorption resulting from the extreme state of protein deficiency and its effects on gut and pancreatic function.  相似文献   
100.
In this retrospective study we aimed to identify from 50 outpatient (OP) mild hypertensives without clinical evidence of target organ damage (TOD), a group with unsustained hypertension in order to see whether they had less echocardiographic TOD than patients with sustained hypertension. Following OP assessment, patients were admitted to a hospital ward and BP was measured after 30 minutes' rest. In 21 patients (fallers) BP fell after admission and in 29 (non-fallers) BP either rose or remained the same (fallers = 164/102 OP v 152/93 mmHg hospital, non-fallers = 165/102 OP v 168/105 mmHg hospital, P less than 0.001 for SBP/DBP differences between the groups on hospitalisation). During the whole day after admission, ambulatory intra-arterial pressure (IABP) was consistently lower in the fallers (137/88 v 148/93 mmHg, P less than 0.04 for SBP, P = NS for DBP) and systolic variability was slightly but significantly higher (18 v 16 mmHg P = 0.05). Echocardiographically-assessed left ventricular mass index (LVMI) was significantly higher in the non-fallers (117 v 101 g/m2 P = 0.03) and correlated positively with mean systolic IABP in both groups although this only reached significance in the non-fallers (n = 25, r = 0.53 P less than 0.01 nonfallers v n = 18 r = 0.42 P = NS fallers). We believe the less sustained pressure of the fallers was responsible for their lower LVMIs and that an exaggerated defence reaction was operating when they were outpatients which relaxed following 30 minutes' rest in hospital. The study demonstrates the importance of sustained hypertension in the development of hypertensive cardiac TOD.  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