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   9180篇
  免费   656篇
  国内免费   11篇
耳鼻咽喉   46篇
儿科学   438篇
妇产科学   181篇
基础医学   1023篇
口腔科学   637篇
临床医学   825篇
内科学   1576篇
皮肤病学   113篇
神经病学   836篇
特种医学   469篇
外国民族医学   2篇
外科学   1514篇
综合类   108篇
一般理论   6篇
预防医学   720篇
眼科学   233篇
药学   549篇
中国医学   3篇
肿瘤学   568篇
  2021年   122篇
  2019年   106篇
  2018年   129篇
  2017年   106篇
  2016年   94篇
  2015年   110篇
  2014年   175篇
  2013年   254篇
  2012年   313篇
  2011年   378篇
  2010年   228篇
  2009年   213篇
  2008年   377篇
  2007年   371篇
  2006年   393篇
  2005年   378篇
  2004年   379篇
  2003年   302篇
  2002年   310篇
  2001年   271篇
  2000年   271篇
  1999年   225篇
  1998年   92篇
  1997年   96篇
  1996年   98篇
  1995年   94篇
  1994年   81篇
  1992年   215篇
  1991年   213篇
  1990年   212篇
  1989年   244篇
  1988年   213篇
  1987年   224篇
  1986年   196篇
  1985年   180篇
  1984年   174篇
  1983年   111篇
  1982年   76篇
  1981年   74篇
  1980年   80篇
  1979年   137篇
  1978年   113篇
  1977年   97篇
  1976年   114篇
  1975年   100篇
  1974年   109篇
  1973年   131篇
  1972年   103篇
  1971年   85篇
  1970年   79篇
排序方式: 共有9847条查询结果,搜索用时 15 毫秒
41.
Current status of magnetic resonance imaging of the wrist.   总被引:2,自引:0,他引:2  
Conventional imaging of the wrist has relied heavily on plain radiography, tomography, fluoroscopy and arthrography. More recently, computed tomography and magnetic resonance imaging (MRI) have been added to this armamentarium. In this article the authors review the normal anatomy of the wrist and demonstrate a variety of pathologic conditions that can be assessed with MRI, including avascular necrosis and tears of the intrinsic and the extrinsic ligaments and the triangular fibrocartilage. MRI of the wrist is still evolving rapidly, and its place in the work-up of wrist disorders is only now being defined.  相似文献   
42.
M C Chamberlain  V A Levin 《Cancer》1989,63(9):1681-1684
Tumors of the hypothalamus present with a variety of clinical syndromes. Such syndromes appear to be both age and histology dependent. The diencephalic syndrome, an entity classically seen in infancy, presents as failure to thrive. In essentially all cases the pathologic substrate is a tumor with a predominance of gliomas. The traditional approach to treatment of the diencephalic syndrome has been surgery both for decompression and pathologic diagnosis followed by irradiation. Because of the tumor location, surgery is often confined to biopsy rather than radical extirpation. Furthermore, in infancy focal brain irradiation is not without significant morbidity. Within this context, we would like to present a case discussion regarding a 27-month-old boy with a hypothalamic-midbrain protoplasmic glioma treated with primary chemotherapy after surgical biopsy and pathologic documentation. The schedule of drugs utilized was based on the hypothesis of biochemical modulation of nitrosourea chemotherapy. Successful response to therapy was documented by sequential computed tomography (CT) studies and serial neurologic examinations beginning at age 5 months and every 2 months thereafter. The response of a single patient with the diencephalic syndrome treated primarily with chemotherapy makes extrapolation premature. Rather, the authors suggest chemotherapy as an alternative to focal brain irradiation. Such therapy could be utilized either in the event of recurrent tumor or as late consolidation after primary treatment with chemotherapy. The latter approach would allow a patient to have radiation therapy deferred until a later age at which time morbidity attending brain irradiation may be minimized.  相似文献   
43.
Diagnosis and treatment of sacral and retrorectal tumors. I   总被引:1,自引:0,他引:1  
  相似文献   
44.
Limb salvage was successful in 25 patients treated for severe grade III upper extremity injuries. In a retrospective review of 20 men and five women, follow-up time averaged 26 months. These high-energy injuries were characterized by massive soft-tissue injury, highly comminuted fractures, and significant neurovascular injury. Farm, industrial, and vehicular accidents accounted for 80% of the cases. Over 50% of the patients had concomitant systemic and/or other significant extremity injuries. Initial treatment consisted of irrigation and debridement and fracture stabilization using external and/or internal fixation. An average of four additional surgical procedures was required to provide soft-tissue coverage and maximum possible functional recovery. Forty-eight percent of the extremities underwent free vascularized or pedicular flaps for coverage or reconstruction. At final follow-up observation, 12% of the extremities rated excellent, 20% rated good, 52% fair, and 16% were poor. Experience gained in managing these severe upper extremity fractures supports the following observations. (a) Grade III open fractures of the upper extremities are frequently associated with significant neural, vascular, and musculotendon injuries. (b) External fixation plays an important role in the stabilization of grossly contaminated fractures. (c) Residual functional disability is common, and most patients do not return to their previous occupation. (d) Staged reconstruction directed toward maximum functional return may take several years.  相似文献   
45.
Background: Recent development of extracorporeal magnetic stimulation (ECMS) which uses current‐changing magnetic fields allows the induction of electrical stimulation in the desired deep tissue. Recent study showed the sacral nerve stimulation reduces corticoanal excitability that may play a functional role in anal continence mechanisms. Preliminary study shows that ECMS of sacral nerve can modify pelvic floor function and expel rectal balloon in patients with pelvic floor dyssynergia (PFD). Aims: To evaluate the effect of ECMS compared with biofeedback therapy (BF) in patients with PFD. Methods and Materials: Thirty‐eight patients who fulfilled Rome II criteria for PFD by colon transit time and anorectal function tests, were randomly treated with 8 sessions of ECMS (2/weeks; n = 19) at prone position or BF (2/weeks; n = 19) at sitting position. Stimulation parameters were set at 50–80% of maximum intensity, 10 and 50 Hz frequency, 3 s burst length with 3 and 6 s off using arm‐typed stimulator (BioCom‐1000, Mcube Co., Korea). Symptom scores for constipation with/without anorectal function test were repeatedly measured after each treatment. Response was defined as 50% or more decreased symptom score after treatment (partial response: 30–50%, poor: <30%). Results: Fifteen patients (age 49.1 ± 13.4 years, mean ± SD; 4 men) completed 8 session of BF and 14 patients (54.5 ± 17.6 years, 3 men) completed 8 session of ECMS. Four patients of BF group discontinued treatment due to unsatisfactory therapeutic effect (n = 1) and withdrew consent (n = 3) and 5 patients of ECMS group discontinued treatment because of same reasons (n = 1, 4). Total symptom scores were significantly decreased after treatment of 8 session in both treatment groups (13.4 ± 6.6 vs. 4.3 ± 4.0 for BF, p = 0.009; 14.9 ± 5.6 vs. 3.4 ± 4.0 for ECMS, p < 0.001). Bowel movements per week were also significantly increased after treatment in both groups (median 2 vs. 7 for BF, p = 0.035; median 2 vs. 7 for ECMS, p = 0.008). Thirteen out of 15 patients showed response in BF group and 12 out of 14 showed good response in ECMS group. No adverse effects in both groups. Conclusions: ECMS is as effective as BF for the treatment of PFD. Long‐term effect of ECMS for the patients with pelvic floor dyssynergia need to be evaluated in the near future.  相似文献   
46.
The proliferative potential of low-grade astrocytomas was estimated in 47 patients. Each patient received an intravenous infusion of bromodeoxyuridine (BUdR), 150 to 200 mg/sq m, at the time of craniotomy to label cells in deoxyribonucleic acid (DNA) synthesis; the percentage of S-phase cells, or BUdR labeling index (LI), of each tumor was determined immunohistochemically. In 29 patients (60%), the tumors had BUdR LI's of less than 1%, indicating a slow growth rate; only three (10%) of these patients died of recurrent tumor during a follow-up period of up to 3 1/2 years. In contrast, of the 18 patients (40%) whose tumors had BUdR LI's of 1% or more, 12 (67%) had a recurrence and nine died during the same follow-up period. These results show that the proliferative potential, as reflected by the BUdR LI, is an important prognostic factor that separates low-grade astrocytomas into two groups and provides a more scientific rationale for selecting treatment for individual patients.  相似文献   
47.
Comparative study of two computerized semen motility analyzers   总被引:1,自引:0,他引:1  
Semen analysis is one of the primary tests carried out to investigate the infertile male. Subjective evaluation of semen is often prone to observer bias and error. To eliminate this, a number of computerized semen analyzers have recently been introduced into the market and we have evaluated two of the more popular models, the Cell Soft Semen Analyzer and the Hamilton Thorn Motility Analyzer (HTM 2000). The Cell Soft identifies sperm on the basis of user defined values for cell size and luminosity whereas the Hamilton Thorn identifies sperm by motility, and then applies the computer-calculated average size and luminosity of all moving objects to non moving sperm cells. Semen samples from 25 normal donors and 25 subfertile patients were analyzed using these two models of computerized semen analyzers, and also by an experienced technician using both the Makler chamber and the hemocytometer. The results obtained from the two automated analyzers were compared with those obtained by subjective evaluation. Variation in sperm count and motility were analyzed according to the sperm density. Four groups, less than 30 million/ml with debris, less than 30 million/ml, 30-50 million/ml, and greater than 50 million/ml were studied. The majority of patients fit into the first two groups. We observed that the HTM 2000 is superior to the Cell Soft in evaluating sperm count within the patient population group. For our donor population with an average sperm count of greater than 85 million/ml both systems provide extremely accurate counts.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
48.
Prior studies in our laboratory have shown that human thyroid neoplasms have a greater adenylate cyclase activity in response to thyroid stimulating hormone (TSH) than does the adjacent histologically normal thyroid tissue. However, there is little information relating activity of the TSH receptor-adenylate cyclase system to the type of thyroid neoplasm. Thyroid tissue from 67 patients was divided by clinical and histological criteria into 6 categories: normal (59), benign tumors (20), stage 1 carcinoma—intrathyroidal involvement only (25), stage 2 carcinomaregional lymph node involvement (6), stage 3 and 4 carcinoma—tissue invasion or distant metastasis (11), and medullary carcinoma (3). Adenylate cyclase activity in an 8,000 x g thyroid membrane preparation was determined in the basal state and when maximally stimulated with 300 mU/ml TSH. The cyclase responsiveness was the ratio of TSH stimulated adenylate cyclase activity compared to basal adenylate cyclase activity. The cyclase responsiveness by category is: normal, 2.8±0.2 (mean ± SEM); benign, 17.9±2.4; stage 1 carcinoma, 9.2±1.9; stage 2 carcinoma, 4.0±1.0; stage 3 and 4 carcinoma, 1.6±0.4; and medullary carcinoma, 1.05±0.04 (for the neoplasms,p <0.02 by ANOVA). Tumor stage was the only correlate with this trend as other prognostic risk factors (age, sex, a history of neck irradiation, or papillary versus follicular histology) showed no difference in cyclase responsiveness. These studies demonstrate a consistent inverse correlation between adenylate cyclase responsiveness and tumor stage or aggressiveness. Cyclase responsiveness appears to have clinical application for predicting which thyroid tumors will behave aggressively.
Resumen Estudios previos en nuestro laboratorio han demostrado que los neoplasmas tiroideos humanos poseen una mayor actividad de adenilato ciclasa en respuesta a la administración de hormona estimulante de la tiroides (TSH) que el tejido tiroideo histológicamente normal adyacente. Sin embargo, existe muy poca información sobre la relation de la actividad del sistema receptor de TSH-adenilato ciclasa y el tipo del neoplasma tiroideo. Tejido tiroideo proveniente de 67 pacientes fue dividido mediante criterios chlínicos e histológicos en 6 categorias: normal (59), tumores benignos (20), extensión intratiroidea solamente en estado 1 (25), carcinoma-extensión ganglionar regional en estado 2 (6), carcinoma-invasión tisular o metástasis distantes en estados 3 y 4 (11), y carcinoma medular (3). La actividad de la adenilato ciclasa en una preparación de membrana tiroidea de 8,000 × g fue determinada en el estado basai y en estado de maxima estimulación con 300 mU/ml TSH. El grado de respuesta de la ciclasa fue la tasa de actividad de la adenilato ciclasa estimulada por TSH comparada con la actividad basai de la adenilato ciclasa. El grado de respuesta por categorías fue: normal, 2.8±0.2; tumor benigno, 17.9±2.4; carcinoma estado 1, 9.2±1.9; carcinoma estado 2, 4.0±1.0; carcinoma estados 3 y 4, 1.6±0.4; y carcinoma medular, 1.05±0.04 (para los neoplasmas,p < 0.02 por ANOVA). El estado del tumor apareció como el único factor de correlatión con esta gradación, ya que otros factures de pronóstico (edad, sexo, historia de irradiación cervical, histología papilar versus folicular) no demostraron diferencia en cuanto al grado de respuesta de la ciclasa. Estos estudios demuestran una consistente relación inversa entre el grado de respuesta de la adenilato ciclasa y el estado o agresividad tumoral. El grado de respuesta de la ciclasa parece tener aplicación clínica para predecir qué tumores tiroideos se habrán de comportar en forma agresiva.

Résumé Les études antérieures provenant de nos laboratoires ont démontré une augmentation de l'activité enzymatique de l'adénylate-cyclase en réponse à la thyroïd stimulating hormone (TSH) dans le tissu thyroïdien humain tumoral, par rapport au tissu thyroïdien adjacent normal. Cependant il existe peu de données concernant l'activité du système récepteur TSH/adénylatecyclase par rapport au type de tumeur de la thyroïde. Les tissus thyroïdiens provenant de 67 patients différents ont été repartis en 6 groupes selon des critères cliniques et histologiques: normal (59), tumeur bénigne (20), cancer stade 1 (intrathyroïdien uniquement) (25), cancer stade 2 (envahissement ganglionnaire régional) (6), cancer stade 3 et 4 (envahissement tissulaire avoisinant ou métastases à distance (11), et cancer médullaire (3). A partir d'une préparation de membrane thyroïdienne centrifugée à 8,000 × g, l'activité de l'adénylate-cyclase a été déterminée en l'état basai et après stimulation maximale par 300 mU/ml de TSH. La réponse enzymatique a été mesurée comme étant le rapport de l'activité stimulée par la TSH/activité basale. Les résultats selon les 6 groupes étaient (moyen±ET): tissu normal, 2.8±0.2; tumeur bénigne, 17.9±2.4; cancer stade 1, 9.2±1.9; cancer stade 2, 4.0±1.0; cancers stade 3 et 4, 1.6±0.4; et cancer médullaire, 1.05±0.04 (p < 0.02 par l'analyse de variance pour les néoplasies). Le stade tumoral était la seule variable corrélée avec l'activité enzymatique. L'activité enzymatique n'était pas corrélée avec l'âge, le sexe, les antécédents d'irradiation cervicale antérieure ou l'histologie (papillaire vs. folliculaire). Ces études montrent un rapport inversement proportionnel entre l'activité d'adénylate-cyclase et le degré d'agressivité tumorale ou le stade. La réponse d l'adénylate-cyclase paraît avoir une application clinique: prévoir quelles tumeurs thyroïdiennes auront une évolution agressive.


Presented at the International Association of Endocrine Surgeons in Sydney, Australia, September, 1987.

Supported in part by the Medical Research Service of the Veterans Administration.  相似文献   
49.
We were able to produce two highly reproducible experimental models (in the rabbit) that demonstrated a high degree of reflex bladder contractile activity. In one model, a somatovesical reflex was induced by touching or pinching the perineal area. This reflex may be organized through a neurogenic reflex at the spinal level. In another model, rhythmic bladder contractions were produced by distal urethral constriction in the absence of bladder distension. These rhythmic contractions were thought to be due to a supraspinal reflex. In both types of contractile reflexes, intravenous administration of hexamethonium inhibited the reflex contractile activity virtually completely, intravenous atropine inhibited over 90% of the induced contractile activity, thus suggesting that these contractions were mediated reflexly through cholinergic stimulation. These two models of reflex bladder contractions should be useful for the study of hyperreflexic bladders.  相似文献   
50.
Multivariate flow cytometric analysis and sorting of mouse bone marrow cells viably stained with Hoechst 33342 (HO) was utilized to obtain a subpopulation enriched at least 30- to 60-fold for clonogenic megakaryocyte precursors (CFU-Meg). HO fluorescence intensity, forward light scatter, and perpendicular light scatter were measured on each HO-stained bone marrow cell as it passed through a dual beam flow cytometer. Cells were sorted on the basis of their light scattering and HO fluorescence intensity properties. The sorting region which included cells with high forward light scatter, low perpendicular light scatter, and low (0.1-0.65 times the modal channel) HO fluorescence intensity contained approximately 0.6% CFU-Meg. Of all CFU-Meg, 75% were contained in the light scatter gate, and 56% of all CFU-Meg were in the low HO-sorting region. This technique offers a simple, one-step procedure to obtain preparations enriched in murine clonogenic megakaryocyte precursors.  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