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   13589篇
  免费   641篇
  国内免费   105篇
耳鼻咽喉   113篇
儿科学   225篇
妇产科学   289篇
基础医学   1667篇
口腔科学   378篇
临床医学   820篇
内科学   3424篇
皮肤病学   207篇
神经病学   908篇
特种医学   481篇
外科学   2536篇
综合类   56篇
一般理论   1篇
预防医学   479篇
眼科学   327篇
药学   752篇
中国医学   21篇
肿瘤学   1651篇
  2023年   86篇
  2022年   172篇
  2021年   294篇
  2020年   165篇
  2019年   199篇
  2018年   299篇
  2017年   209篇
  2016年   255篇
  2015年   307篇
  2014年   358篇
  2013年   494篇
  2012年   799篇
  2011年   889篇
  2010年   476篇
  2009年   418篇
  2008年   831篇
  2007年   842篇
  2006年   791篇
  2005年   740篇
  2004年   705篇
  2003年   685篇
  2002年   649篇
  2001年   351篇
  2000年   310篇
  1999年   301篇
  1998年   188篇
  1997年   135篇
  1996年   143篇
  1995年   100篇
  1994年   114篇
  1993年   80篇
  1992年   193篇
  1991年   174篇
  1990年   202篇
  1989年   176篇
  1988年   143篇
  1987年   116篇
  1986年   116篇
  1985年   95篇
  1984年   90篇
  1983年   75篇
  1982年   47篇
  1981年   31篇
  1979年   67篇
  1978年   47篇
  1977年   42篇
  1976年   30篇
  1975年   30篇
  1971年   30篇
  1970年   32篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
We studied the brain uptake of amino acid in a patient with acute cerebral infarction with L-[2-(F-18)] fluorophenylalanine and positron emission tomography. The increased accumulation of the ligand was specifically found in the peri-infarct area where oxygen metabolism was still maintained but decreased later in the 72-day follow-up period. The kinetic analysis revealed that increased accumulation was not due to increased transport from the blood to the brain but to delayed washout from the brain to the blood. Although the mechanism is still unknown, abnormally high accumulation of L-[F-18]fluorophenylalanine may predict delayed neuronal changes after ischemic insults of the brain.  相似文献   
82.
Anatomy now has a step to transfer from qualitative science to quantitative science. The methods of anatomical investigation employ optical instruments. Anatomy initially described qualitative features of the structure of the body, but now it turns to transfer to new fields measuring the number, size, length, area and volume of not only, structure but also the histochemical components of the structure with quantitative analysis. In order to quantify histochemical reactions in various organs, light and electron microscopic radioautograms were prepared from the liver, pancreas, intestines and kidney which were labeled with 3H-thymidine, 3H-uridine, 3H-leucine, 3H-glucosamine and 3H-glycerol, fixed in glutaraldehyde and osmium tetroxide, embedded in Epoxy resin, sectioned either thick or thin, coated with either Konica NR-M2 or -H2 radioautographic emulsions, exposed, developed, stained for either light or electron microscopic radioautographs. The radioautographs were observed with Olympus Vanox AHB-LB or Nikon Optiphot-2 light microscopes or Hitachi H-700, JEOL JEM-4000EX electron microscopes at 200 and 400 kV. The radioautograms were analysed with various image and analysed such as PPA-250, MOP, Digigramer-G, IBAS-II, Quadra 900, Luzex 300 to count the number of silver grains and to measure the size and number of structures. Some electron microscopic radioautographs were analysed in analytical electron microscopes, combined with Hitachi H-700 Horiba EMAX-1800E, JEOL JEM-200CX Kevex 7000-77, and JEOL JEM-4000EX Tracor-Northern TN-5400 to quantify silver grain contents. The results demonstrated that correct data can be obtained by controlling both full-automatic and semi-automatic image analysers by operating them manually.  相似文献   
83.
BACKGROUND: Systematic population-based screening for gastric cancer is widely spread in Japan. However, the case-control study method has been the main method used to evaluate the effectiveness of the screen ing to reduce gastric cancer mortality in Japan. METHODS: This article presents a population-based cohort study. A questionnaire about lifestyles and dietary habits was distributed to 36,990 residents in a city of Japan. The response rate to the questionnaire was 92.0%. After ineligible responders had been excluded, 24,134 subjects were classified into screened and un screened groups according to their self-reports of participation in the screening the previous year. We followed them up for 40 months and linked resident death records in the city. We compared mortality from gastric cancer and all other causes between the groups by us ing the Cox proportional hazard model. RESULTS: The follow-up period was 78,156.6 person-years from September 1992 to December 1995. The multivariate relative risks for gastric cancer death of the screened group in comparison with the unscreened group were 0.72 (95% CI 0.31-1.66) among males and 1.46 (95% CI 0.43-4.90) among females. CONCLUSION: Although our data are preliminary, we were unable to demonstrate a large contribution of the present screening program to decreasing gastric cancer mortality. Further follow-up is needed to in crease the precision.  相似文献   
84.
PURPOSE: Psychogenic lower urinary tract dysfunction (PLUTD) is composed of two syndromes; psychogenic frequency-urgency syndrome (PFUS) and psychogenic urinary retention (PUR). We evaluated the patho-physiology of PFUS and PUR, and explored the different pathogenesis in these syndromes. MATERIAL AND METHODS: Forty five patients with PLUTD, consisting of 23 patients with PFUS and 22 patients with PUR were investigated by using the psychological tests: CMI (Cornell Medical Index) and TEG (Todai's Egogram), a quantitative perspiration test in 45 females (23 patients with PFUS and 22 patients with PUR), and simultaneous measurements of voiding cysto-urethrography and urodynamic studies using the Life-Tech 6 channel polygraph in 35 patients (17 patients with PFUS and 18 patients with PUR). RESULTS: The prevalence in ages revealed two peaks, 20 years and 50 to 60 years. Over 25% of them had pyuria more than 10/hpf of WBC. Peak flow rate measured by uroflowmetry showed normal range in PFUS group and decreased in PUR group. The functional vesical volume was less than 100 ml in most patients with PFUS. Residual urine in PUR group was significantly greater. Capacity of the PFUS group were able to hold over 400 ml of contrast instilled through the urethral catheter, despite increased desire to void. Over 15% of the study group with PFUS showed uninhibited systolic contraction of detrusor (> 15 cm H2O) during filling phase. The measurement value of urodynamic parameters demonstrated that a periodic follow-up survey of the upper urinary tract should be performed because of the low compliance bladder in the patients with PLUTD. During voiding phase, the women with PFUS had a tendency to be divided into two groups, hypercontractile or acontractile detrusor. The voiding cysto-urethrography (VCUG) showed a tendency of bladder neck opening on patients with PFUS during filling phase. Most of PLUTD cases demonstrated a round to triangle shape on vesical configuration, which led to a spastic condition of detrusor muscle. We attempted to measure the quantitative perspiration using 3 kinds of loading tests; respiratory, arithmetic and psychological load. In the psychological loading test, we asked 98 questions about their daily lives including occupation, living condition, family relationship and sexual activities. Arithmetic loading test consisted of counting in reverse, subtraction and multiplication. The quantitative perspiration rate resulted in a "positive" in many patients with PFUS. Respiration loading test was performed to measure the respiration volume during 3 large inhales. Most patients with PUR tested within the normal range for respiration except for those patients with decreased or no perspiration during the psychiatric loading test. These results may reflect the psychological elements including suppression and subconscious defense mechanism. Neurosis which was diagnosed as having type III to type IV of the Cornell Medical Index was demonstrated in less than under 40% of patients with PFUS and more than 55% patients with PUR. There was no significant trend or difference between PFUS and PUR detected from Todai's Egogram. CONCLUSIONS: Due to the reflection of many psychological responses, it is necessary to investigate from various examinations including psychological, autonomical and classical urological studies for accurate diagnosis of PLUTD.  相似文献   
85.
86.
We studied clinical aspects of the "third rhythm," which was first described by Niedermeyer as alpha-like activity of the temporal lobe. By scalp EEG, temporal alpha-like activity was recorded in 15 (0.30%) of 4929 patients over 20 years of age. The temporal alpha-like activity was observed in 5 patients who had clinical and brain imaging findings indicating the presence of a cerebrovascular disorder. The alpha-like rhythm of these patients was left-sided, and wicket spikes appeared in the same region as the alpha-like rhythms in 4 of the 5 patients. In 8 of the 15, the temporal alpha-like rhythm was recorded over the defective bone or replacement bone after intracranial surgery. The alpha-like rhythm of these patients was similar to breach rhythm in the temporal region. The remaining 2 patients had not undergone intracranial surgery nor did they show symptoms of cerebrovascular disorders. The temporal alpha-like rhythms in one of these 2 might be a physiological third rhythm detected by scalp EEG through congenital bone thinning. Our observation supports the existence of intrinsic activity of the temporal lobe (the third rhythm). The third rhythm can be recorded by routine scalp EEG in some clinical conditions, and it is important to recognize this rhythm when one encounters temporal rhythmic activity independent of alpha rhythm of the occipital lobe.  相似文献   
87.
88.
Two cases of intracranial adenoid cystic carcinoma mimicking meningioma are reported. In one, MRI showed not only a homogeneously enhancing extra-axial tumour attached to the dura mater of the posterior cranial fossa, but also surrounding dural enhancement, the dural tail sign. In the second, CT demonstrated a well-demarcated enhancing extra-axial tumour, indistinguishable from a sphenoid ridge meningioma extending into the orbit. The neuroradiological features of intracranial adenoid cystic carcinoma may thus closely resemble those of meningioma.  相似文献   
89.
Summary Currently there are no limitations on age of employment on private forestries in Japan. Hence, it was hypothesized that in these kind of enterprises, elderly chain saw operators, or those with long-term exposure, might be at higher risk of developing hand-arm vibration syndrome (HAVS). We consequently investigated the prevalence of HAVS in 447 chain saw workers on private forestries in Gifu Prefecture, Japan, with particular reference to age and exposure period. Of this population, 43 (9.6%) had signs and symptoms of vibration-induced white finger (VWF), and among these workers the severity of finger blanching was significantly correlated (P < 0.01) with the exposure period. Classification of all subjects by exposure period showed that workers with 30 years' exposure had higher prevalences of VWF (20.9%) and numbness of the hands (25.4%) compared to other groups. Significant differences (P < 0.01) were found between the functional capacities of workers with VWF and those of control subjects. We concluded that (a) the elderly chain saw operators and those with longer exposure should be moved to other jobs with a lower or no risk of exposure to vibration, and (b) the results of screening tests, even without cold water immersion (which we did not employ, in order to protect workers' hands), could be helpful for the identification of workers with VWF.  相似文献   
90.
A new modified rotation radiation method called "three-dimensional moving field radiation therapy" is described. The new method uses rotation in many planes while maintaining the the same isocenter to achieve a good spatial dose distribution. This delivers a high dose to tumors and spares the surrounding normal structures. This easy method can be carried out using the equipment for conventional rotation radiation therapy. The new method was superior to the one plane rotation radiation therapy using a physical phantom with film, a chemical phantom using the iodine-starch reaction, and a new biological model using tumor cells. Treatment of six brain tumors irradiated with total air doses of 50-60 Gy caused no hair loss or radiation necrosis.  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