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   47887篇
  免费   4483篇
  国内免费   80篇
耳鼻咽喉   613篇
儿科学   1332篇
妇产科学   1326篇
基础医学   6895篇
口腔科学   1274篇
临床医学   5894篇
内科学   8395篇
皮肤病学   613篇
神经病学   3801篇
特种医学   2348篇
外国民族医学   1篇
外科学   6207篇
综合类   866篇
一般理论   23篇
预防医学   5259篇
眼科学   1092篇
药学   3554篇
  2篇
中国医学   56篇
肿瘤学   2899篇
  2021年   657篇
  2019年   643篇
  2018年   757篇
  2017年   625篇
  2016年   611篇
  2015年   714篇
  2014年   951篇
  2013年   1479篇
  2012年   2141篇
  2011年   2223篇
  2010年   1213篇
  2009年   1003篇
  2008年   1867篇
  2007年   2036篇
  2006年   2019篇
  2005年   2020篇
  2004年   1837篇
  2003年   1675篇
  2002年   1708篇
  2001年   1605篇
  2000年   1712篇
  1999年   1458篇
  1998年   710篇
  1997年   557篇
  1996年   571篇
  1995年   559篇
  1994年   479篇
  1993年   496篇
  1992年   1263篇
  1991年   1168篇
  1990年   1157篇
  1989年   1102篇
  1988年   1007篇
  1987年   1023篇
  1986年   931篇
  1985年   932篇
  1984年   731篇
  1983年   638篇
  1982年   460篇
  1981年   408篇
  1980年   425篇
  1979年   661篇
  1978年   535篇
  1977年   427篇
  1976年   418篇
  1975年   384篇
  1974年   451篇
  1973年   438篇
  1972年   450篇
  1971年   423篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We present a case in which an open fracture of the ulna penetrated the skull and caused a comminuted, depressed skull fracture with a large intraparenchymal hematoma containing bone fragments.  相似文献   
82.
The specialty of pain medicine, as noted by Lippe,“… justifies itself as a unique medical specialty by virtue of a distinct body of knowledge and a well-defined scope of practice. In common with other medical specialties, it is founded on an infrastructure of scientific research, education, and clinical practice [1].“ The traditional methods of education for healthcare providers, such as medical schools, nursing schools, physical therapy schools, and clinical psychology programs, do not prepare their students adequately for the delivery of evaluation and treatment services to patients experiencing pain. Also apparent, as evidenced by the dearth of medical literature, is that the traditional methods of educating pain specialists do not adequately prepare students for an effective approach to the realities of healthcare economics in their respective fields.The result of a lack of significant education in the economics of pain medicine can be financially devastating to a new practitioner who is practicing “good” medicine yet not meeting the financial obligations incipient in the operation of a multidisciplinary pain center or even a solo practice. One important concept in the study of healthcare economics is the issue of cost-effectiveness [2].  相似文献   
83.
Clinicians and researchers alike have questioned and studied the origin of schizophrenia for decades. Since the early 1900s, a genetic hypothesis has been suggested. This article reviews studies on a possible genetic cause of schizophrenia by use of various methods of comparison: twins, adoption, family history, family studies, and studies of biologic markers. Most researchers conclude that schizophrenia is likely caused by a genetic predisposition coupled with environmental influences.  相似文献   
84.
85.
The effects of bilateral nucleus accumbens microinjections ofd-ala-met-enkephalinamide (DALA) were assessed in behavioral activation and lateral hypothalamic self-stimulation (LHSS) rate-frequency curve-shift paradigms in normal and accumbens 6-OHDA (4.0 µg) treated rats. Microinjections of DALA (2.5 µg/µl) in the behavioral activation paradigm had little effect on normal activity; however, DALA administered to 6-OHDA treated rats produced a significant overall increase in locomotion. The 6-OHDA DALA-induced locomotion effect peaked at 2 weeks after 6-OHDA treatment and then returned to baseline levels by week 5 posttreatment. Using LHSS, DALA tested over a range of doses (2.5, 5, 10, 20 µg/µl) displayed a weak biphasic reward effect only at the highest dose, which was characterized by an initial suppression followed by an elevation. DALA significantly depressed initial operant motor/performance in LHSS in a dose dependent fashion. Micro-injections of the normally ineffective low dose of DALA (2.5 µg/µl) following accumbens 6-OHDA treatment produced a significant LHSS reward decrease 2 weeks posttreatment, while LHSS motor/performance was relatively unaffected. Results are discussed in terms of opiate-dopamine and limbic-motor interactions.  相似文献   
86.
87.
As opposed to the virtually constant load exerted by water on the cilia of ciliated protozoa, the hydrodynamic load on respiratory cilia can undergo broad variations because of changes in the rheologic properties of mucus. When water-rowing ciliated cells are exposed to increased viscosity (1 to 50 cP), their beat frequency decreases exponentially. According to Newton's fluid dynamic theory, this outcome is expected for an engine that generates constant force. However, the findings reported here indicate that when mucus-propelling respiratory ciliated cells are exposed to high viscous loads, ranging from 12 to 150 cP, the frequency of ciliary beat decreases only slightly, whereas the beat amplitude remains virtually constant. These observations suggest that ciliated cells of the respiratory tract have a functional reserve that allows them to autoregulate their mechanical output in response to the changes in viscosity to which they are normally exposed in the airway.  相似文献   
88.
The relationship between dietary fat intake and fasting plasma lipid levels was assessed in 35 female and 19 male adolescents recruited from two local education authority schools in Norwich, UK. Dietary intakes were assessed using a 7-day weighed dietary record method, coupled with the collection of duplicate diets. Fat and energy intakes calculated using food composition tables were compared with values obtained by direct analysis of duplicate diets. Fasting plasma lipid levels (total, HDL and LDL cholesterol and triglycerides) were measured and compared with total dietary lipids and fatty acid intakes. The average proportion of energy consumed as fat was higher than is currently considered desirable but lower than previous studies have reported for adults. Mean serum total cholesterol values were 4.2 (SEM 0.1) mmol for females and 4.5 (SEM 0.2) mmol for males; this difference was not statistically significant. In male subjects the dietary fatty acid profiles were significantly correlated with several parameters of plasma lipid status which are thought to be risk factors for coronary heart disease, and in particular with the ratio of total:HDL cholesterol.  相似文献   
89.
Hemiarthroplasty of the elbow with an endoprosthesis has been reported very infrequently; only about 20 cases have been reported previously in the literature. This case merits reporting because of the youth of the patient (age 19), the uniqueness of the prosthetic component, and the long-term follow-up observation. The patient had posttraumatic bony ankylosis of the elbow with a painful supracondylar pseudoarthrosis and loss of bone from the proximal metaphysis. A custom humeral endoprosthesis was inserted, and anatomic reconstitution of the sigmoid notch of the ulna was provided. Reasonably good, painless, stable motion was achieved, which has not deteriorated in the subsequent 21 years of observation. The clinical significance of this case is that in a nonweight-bearing hinged joint, endoprosthesis arthroplasty can be an excellent option when given the proper indications and carried out with meticulous planning.  相似文献   
90.
Placental transfer of vitamin E was investigated from 19 to 35 weeks of gestation by analysis of fetal and maternal blood samples for total tocopherol, total lipids, and fetal red blood cell antioxidant reserves. Fifty-two fetal blood samples were obtained under ultrasonographic guide by percutaneous umbilical blood sampling. Thirteen were from fetuses with gestational age less than or equal to 22 weeks (x serum vitamin E = 0.4 +/- 0.14 mg/dl), 12 were from fetuses at 23-27 weeks gestation (x serum vitamin E = 0.4 +/- 0.21 mg/dl), and 27 were from fetuses with gestational age 28-38 weeks (x serum level = 0.37 +/- 0.18). Total lipid levels ranged from 140 to 216 mg/dl. Maternal plasma vitamin E concentrations correlated significantly with concurrent values in the fetus. There were no significant differences in serum vitamin E levels or vitamin E to total lipid ratio in samples from early, mid, or late gestation in either the mother or fetus. Red blood cell antioxidant reserve on samples from 18 fetuses were grossly abnormal by three different functional assays. On the basis of these data, placental transfer of vitamin E appears to be relatively constant through advancing gestation. Red blood cell antioxidant reserve is uniformly low.  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