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   29534篇
  免费   2086篇
  国内免费   142篇
耳鼻咽喉   377篇
儿科学   817篇
妇产科学   532篇
基础医学   4030篇
口腔科学   891篇
临床医学   2824篇
内科学   5585篇
皮肤病学   401篇
神经病学   3265篇
特种医学   1011篇
外国民族医学   1篇
外科学   4057篇
综合类   359篇
一般理论   20篇
预防医学   2640篇
眼科学   825篇
药学   2293篇
中国医学   70篇
肿瘤学   1764篇
  2023年   208篇
  2022年   340篇
  2021年   727篇
  2020年   422篇
  2019年   587篇
  2018年   740篇
  2017年   541篇
  2016年   549篇
  2015年   607篇
  2014年   907篇
  2013年   1268篇
  2012年   1882篇
  2011年   1919篇
  2010年   1025篇
  2009年   873篇
  2008年   1661篇
  2007年   1768篇
  2006年   1704篇
  2005年   1764篇
  2004年   1656篇
  2003年   1557篇
  2002年   1525篇
  2001年   469篇
  2000年   427篇
  1999年   438篇
  1998年   361篇
  1997年   324篇
  1996年   265篇
  1995年   286篇
  1994年   200篇
  1993年   237篇
  1992年   288篇
  1991年   265篇
  1990年   256篇
  1989年   264篇
  1988年   214篇
  1987年   238篇
  1986年   215篇
  1985年   233篇
  1984年   198篇
  1983年   185篇
  1982年   205篇
  1981年   220篇
  1980年   203篇
  1979年   163篇
  1978年   144篇
  1977年   148篇
  1976年   132篇
  1974年   98篇
  1972年   96篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
This study used magnetic resonance imaging to examine pituitary gland volume (PGV) in teenage patients with a first presentation of borderline personality disorder (BPD). No difference in PGV was observed between healthy controls (n = 20) and the total BPD cohort (n = 20). However, within the BPD cohort, those exposed to childhood trauma (n = 9) tended to have smaller pituitaries (− 18%) than those with no history of childhood trauma (n = 10). These preliminary findings suggest that exposure to childhood trauma, rather than BPD, per se, might be associated with reduced PGV, possibly reflecting hypothalamic–pituitary–adrenal axis dysfunction.  相似文献   
103.
The validity of a simple clinical classification of acute ischaemic stroke   总被引:6,自引:0,他引:6  
The aim of the study reported here was to test the validity of a simple clinical classification of acute ischaemic stroke (Oxfordshire Community Stroke Project, OCSP) in predicting the site and size of cerebral infarction on computed tomography (CT). Consecutive patients admitted to hospital with acute ischaemic stroke were prospectively identified and classified into one of four clinical syndromes according to the OCSP classification, blind to the result of CT. The CT brain scans were classified blind to the clinical features into those demonstrating: small, medium or large cortical infarcts; small or large subcortical infarcts in the anterior circulation territory; and posterior cerebral circulation territory infarcts. A total of 108 patients were included. A recent infarct was seen. on the CT scan in 91 patients (84%), and the clinical classification correctly predicted the site and size of the cerebral infarct in 80 of these (88%; 95% confidence interval 77–92%). The positive predictive value was best for large cortical infarcts (0.94) and worst for small subcortical infarcts (0.63). The OCSP clinical classification is a reasonably valid way of predicting the site and size of cerebral infarction on CT and can, therefore, be used very early after stroke onset before the infarct appears on the scan.  相似文献   
104.
Limited data are available concerning resting metabolic expenditure (RME) in cancer patients and the effect of RME by varying glucose intake. This study describes the measurements on 21 patients with colorectal cancer while fasting and with incremental levels of standard TPN-glucose system by central vein. Following an overnight fast, the measured mean +/- SEM percent difference from the predicted RME for the male group was 4.13 +/- 1.67% and the female group, 2.09 +/- 2.09%. The overall mean percent difference of 2.95 +/- 1.45 suggests that colorectal cancer does not cause an increase in energy expenditure. Hepatic metastases in 11 of the patients did not influence RME. The data from the 21 patients indicate a statistically significant increase in RME with TPN compared to postabsorptive states in females of 37%, in males 21.88%, and combined of 29.88%. Progressively greater increases in RME were seen when calories provided incrementally exceeded the basal RME. Carbohydrate loading in excess of the patient's calorie need, as indicated by the respiratory quotient (RQ) greater than 1.0, results in fat synthesis and other energy-costing processes. The basal RME demonstrates that these cancer patients are not hypercatabolic, but do respond to high-level force-feeding with markedly increased metabolic expenditures.  相似文献   
105.
Summary It was previously shown that 11 months after ovariectomy the volume fraction of trabecular bone in the spine and 11th rib medullary canal of Beagle dogs (6 control, 9 ovariectomized) was significantly reduced. In this paper it is shown that these changes are accompanied by increased marrow fat volume in the 11th rib (59.0±9.5% vs. 44.3 ±10.0%). Conversely, the volume fraction of functional (hematopoietic) cells in the marrow was reduced by ovariectomy. Additionally, variations in marrow fat volume were tested for correlation with 22 other variables pertinent to bone physiology. Marrow fat volume was significantly positively correlated with serum osteocalcin, rib trabecular bone porosity, rib cross-sectional area, and gains in body weight. It was negatively correlated with serum estrogen concentrations and the extent of rib trabecular surfaces labeled with tetracycline.  相似文献   
106.
107.
Tuberculosis and HIV infection in sub-Saharan Africa.   总被引:23,自引:0,他引:23  
K M De Cock  B Soro  I M Coulibaly  S B Lucas 《JAMA》1992,268(12):1581-1587
  相似文献   
108.
109.
Lateral skull base surgery has remained the surgical frontier of new developments in the treatment of lesions heretofore difficult to access. Examination of surgical results stimulates technical innovation and provides an intervention risk-benefit ratio assessment for particular lesions useful in management planning. With this in mind, we report the updated collective experience with lateral skull base surgery at the Otology Group over the past 20 years. Two hundred ninety-eight patients underwent surgical intervention for lateral skull base lesions. In 81 patients these lesions were malignant; in 217, benign. Of the benign lesions, 165 were glomus tumors: 139 glomus jugulare, 19 glomus vagale, and 7 glomus tympanicum. The remainder comprised 21 menigniomas, 14 neuromas, two neurofibromas, and a small group of much rarer entities. The philosophy of surgical approach, results, and follow-up are discussed.  相似文献   
110.
This paper describes a method for using teratogenic deformities in fish as the basis for evaluating impacts of selenium contamination. Teratogenic deformities are reliable bioindicators of selenium toxicosis in fish. They are produced in response to dietary exposure of parent fish and subsequent deposition of selenium in eggs. There is a close parallel between selenium concentrations in eggs, incidence of teratogenic deformities in larvae, and magnitude of reproductive failure. Using these relationships, an index was developed for teratogenic-based assessment of impacts to fish populations. The index is composed of three ratings that signify increasing levels of terata-induced population mortality: 1, negligible impact (<5% population mortality); 2, slight to moderate impact (5–20% population mortality); 3, major impact (>20% population mortality). Each rating is based on the anticipated population-level impact of the corresponding degree of mortality. Teratogenic-based impact assessment provides a conclusive cause–effect linkage between the contaminant and the fish. It is particularly useful for verifying selenium-induced impacts on reproductive success because poor reproduction can be caused by many things—i.e., fluctuating water levels, nest predation, food shortages, poor recruitment, etc. The index given here should be a useful tool for evaluating the effect of selenium on fish populations. Moreover, application of this technique may save considerable time and money by identifying the most efficient use of manpower and funds early in the assessment process.  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