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   8744篇
  免费   531篇
  国内免费   26篇
耳鼻咽喉   126篇
儿科学   276篇
妇产科学   263篇
基础医学   905篇
口腔科学   139篇
临床医学   786篇
内科学   2285篇
皮肤病学   82篇
神经病学   911篇
特种医学   338篇
外科学   941篇
综合类   93篇
一般理论   6篇
预防医学   988篇
眼科学   158篇
药学   570篇
中国医学   2篇
肿瘤学   432篇
  2024年   7篇
  2023年   35篇
  2022年   59篇
  2021年   178篇
  2020年   83篇
  2019年   169篇
  2018年   194篇
  2017年   163篇
  2016年   147篇
  2015年   172篇
  2014年   281篇
  2013年   391篇
  2012年   633篇
  2011年   695篇
  2010年   383篇
  2009年   376篇
  2008年   575篇
  2007年   691篇
  2006年   649篇
  2005年   616篇
  2004年   584篇
  2003年   540篇
  2002年   475篇
  2001年   106篇
  2000年   71篇
  1999年   81篇
  1998年   106篇
  1997年   80篇
  1996年   63篇
  1995年   71篇
  1994年   49篇
  1993年   50篇
  1992年   61篇
  1991年   38篇
  1990年   45篇
  1989年   67篇
  1988年   40篇
  1987年   28篇
  1986年   28篇
  1985年   19篇
  1984年   34篇
  1983年   21篇
  1982年   26篇
  1981年   25篇
  1980年   18篇
  1979年   11篇
  1978年   14篇
  1977年   11篇
  1976年   9篇
  1971年   6篇
排序方式: 共有9301条查询结果,搜索用时 328 毫秒
91.
In poor rural communities, access to basic health care is often severely limited by inadequate supply as well as financial barriers to seeking care. National policies may introduce social health insurance, but these are likely to begin with the salaried public and private sector workers while the informal sector population may be the last to be covered. Community initiatives to generate health care financing require a complex development process. This paper covers attempts to develop such schemes in rural populations in Guatemala and the Philippines through non-government organizations and notes the major factors which have contributed to unequal progress in the two schemes. The scheme of the Association por Salud de Barillas (ASSABA) in Guatemala was not sufficiently established as an administrative body at the conceptual stage and there was no clear national policy on health care financing. By the time the necessary action was taken, local conflicts hindered progress. In the Philippines, the ORT Health Plus Scheme (OHPS) was implemented during the period of legislation of a national health insurance act. The appraisal after three years of operation shows that OPHS has made health care affordable and accessible to the target population, composed mainly of low and often unstable income families in rural areas. The major success factors are probably the administrative structure provided by a cooperative and controls in the delivery system and in expenditures, through the salaried primary health care team, referral process and the capitation agreement for hospital-based services. The proliferation of such schemes could benefit from national guidelines, a formal accreditation process and an umbrella organization to provide assistance in design, training and information services, involving government, non-government and academic institutions as an integral part of the development process.  相似文献   
92.
93.
The suprathreshold tonotopic organization of rat and guineapig auditory cortex was investigated using intrinsic signaloptical imaging through a thinned skull. Optical imaging revealedthat suprathreshold pure sine wave tone stimulation (25–40dB) evoked activity over large cortical areas that were tonotopicallyorganized. Three-dimensional surface plots of the activatedareas revealed "patchy" auditory-evoked activity consistingof numerous local peaks and valleys building to a maximum. Subsequentdetailed electrophysiological mapping in the same subjects confirmedthe localization of auditory-evoked activity based on opticalimaging, including responses to a test frequency at corticalloci more than 2 octaves away from the threshold-defined isofrequencycontour. The success of this technique in visualizing auditorycortex functional organization at suprathreshold stimulus levelswill allow for future investigations of auditory cortex frequencyrepresentation. including representational plasticity inducedby a variety of experimental manipulations.  相似文献   
94.
Nonsteroidal antiandrogens (AA) cannot be topically used for androgenetic alopecia (AGA) because of systemic resorption. A new class of androgen receptor (AR) suppressors designed for safe topical treatment of AGA was synthesized from (3‐amino‐2‐hydroxy‐2‐methyl‐N‐(4‐nitro‐3‐trifluoromethyl)phenyl) propanamide (BP‐34), to contain perfluoroalkyl moieties. The trifluoromethyl derivative (fluridil) at 10 μM decreased expression of the AR in LNCaP human cells by 95%, its serum half‐life was 6 h; it decomposes hydrolytically to BP‐34 and trifluoroacetic acid. Acute intraperitoneal maximum tolerated dose (MTD) of fluridil in mice is 270–300 mg/kg/d and the subacute MTD is 450 mg/kg/d. The oral LD50 in mice was 2,872 mg/kg in males, 2,232 mg/kg in females, and >2,500 mg/kg in rats. Fluridil solution in isopropanol was not cutaneously absorbed in rabbits, did not sensitize or show any phototoxic or photoallergic effects on guinea pig skin, and demonstrated no skin irritation potential in rabbits and humans. Fluridil solid induced only slight and reversible eye irritancy in rabbits and displayed no cytotoxicity to rabbit corneal fibroblasts in vitro. Fluridil demonstrated no significant mutagenicity potential by Ames method. In a double‐blind study, 43 males with AGA, Norwood grade II to Va, used topical 2% fluridil in isopropanol or the vehicle daily for 12 months. Anagens (growing hairs) increased in the fluridil group from 76% to 89%. All hematological and biochemistry values remained within normal range, including testosterone, which varied but seasonally. No fluridil or its decomposition product (BP‐34) was detected in serum. No adverse side effects were reported. Drug Dev. Res. 59:292–306, 2003. © 2003 Wiley‐Liss, Inc.  相似文献   
95.
A national household probability sample of 4,023 adolescents aged 12 to 17 years was surveyed by telephone via structured clinical interview to determine the impact of familial substance use, sexual and physical assault, witnessed violence, depression and posttraumatic stress disorder (PTSD) on risk of smoking. Results indicated that familial substance use increased risk of smoking only for boys and sexual assault or depression increased risk of smoking only for girls. Age, Caucasian ethnicity, and experiencing physical assault or witnessing violence elevated risk of current cigarette use for both genders. By contrast, PTSD per se was not associated with increased risk of smoking, after the effects of other variables were controlled.  相似文献   
96.
To update its cancer statistics, the newly established Middle East Cancer Society examined the cancer frequency patterns in Egypt and the Gaza Strip. The results revealed differing overall patterns. For men the highest frequencies were found for lymphoma, bladder cancer and cancers of the oral cavity and pharynx in Egypt, and for lung cancer, leukaemia and lymphoma in Gaza. For women, breast cancer had the highest frequency in both areas, followed by cancers of the oral cavity and pharynx in Egypt, and leukaemia and lymphoma in Gaza. The distribution of cancer occurrence by organ system also varied. In the light of the different ethnicities, lifestyles, socioeconomic levels and carcinogenic exposure among the countries of the Middle East, this kind of comparison can provide the background for more sophisticated approaches for discerning risk factors in cancer. We believe that further cooperation among participating countries will overcome the present limitations in data collection, registration and access.  相似文献   
97.
98.
A novel serum 21 kDa haptoglobin-related protein (Hpr) was investigated in patients with malignant lymphoma, to evaluate its correlation with clinical and histologic features at presentation and its possible role as a tumor marker for patient outcome. One hundred fifty eight serum samples were taken from 88 patients with non-Hodgkin’s lymphoma (n=58) and Hodgkin’s disease (n=30) at presentation and in the course of follow-up. Sera from 61 healthy volunteers served as normal controls. Serum Hpr levels in the lymphoma patients (median 430xl03 u/ml, range 0-4000xl03) were significantly higher than in the control group (median 68xl03 u/ml, range 0-180xl03) (p=0.0001). Higher median Hpr values were detected in patients with advanced disease (p=0.013), “B” symptoms (p=0.029) and in males (p=0.053). There was also a significant correlation between Hpr and erythrocyte sedimentation rate (p=0.028). Serial determinations showed a significant decrease of the initial Hpr values obtained after treatment in 41 patients, 38 of whom achieved complete remission. In the follow-up period additional Hpr measurements were taken from 17 patients. Three of them eventually relapsed, and showed increased Hpr levels at the time of relapse. Hpr levels remained low in 11 of 14 patients who maintained complete remission, and increased in three. In conclusion, serum Hpr is a new serum tumor marker of potential use in the clinical setting of lymphoma. This work is dedicated to the memory of Dr. Arie H. Bartal, a dedicated oncologist and friend. This work was supported by Chemotech Thechnologies Ltd., by grant no. 3676 from the Chief Scientist’s Office of the Ministry of Health, Israel, and by the Fund for Promotion of Research in the Technion.  相似文献   
99.
100.
OBJECTIVES: Diffusion tensor imaging (DTI), a technique capable of examining water diffusion in different tissues and the organisation of white matter tracts, was used to investigate the neuropathology of the corpus callosum in vivo in patients with schizophrenia. METHODS: Diffusion tensor imaging was performed in 20 schizophrenic patients and 25 healthy controls. Two complementary measures, mean diffusivity and fractional anisotropy, which are considered to be sensitive indices of axonal integrity, were obtained from regions of interest in the genu (anterior) and splenium (posterior) of the corpus callosum. RESULTS: Mean diffusivity was significantly increased and fractional anisotropy significantly reduced in the splenium but not the genu of the corpus callosum in the schizophrenic group compared with controls. There were no significant sex differences in the DTI measures for either the schizophrenic or control group. Clinical variables such as age, duration of illness, dose of antipsychotic medication, and schizophrenic symptoms did not predict the DTI changes in the schizophrenic patients. CONCLUSIONS: The presence of DTI changes in the splenium but not the genu of the corpus callosum suggests that there may be a focal disruption of commisural connectivity in schizophrenia. However, these findings do not exclude the possibility of abnormalities in other areas of the corpus callosum or other regions of white matter and further research using different methods of analysis may enable us to clarify this. Diffusion tensor imaging is a valuable tool in investigating the structure of white matter in schizophrenia.  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