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   9868篇
  免费   432篇
  国内免费   58篇
耳鼻咽喉   184篇
儿科学   78篇
妇产科学   110篇
基础医学   1158篇
口腔科学   192篇
临床医学   696篇
内科学   2546篇
皮肤病学   206篇
神经病学   565篇
特种医学   595篇
外科学   1679篇
综合类   44篇
预防医学   307篇
眼科学   82篇
药学   762篇
中国医学   43篇
肿瘤学   1111篇
  2023年   63篇
  2022年   156篇
  2021年   218篇
  2020年   98篇
  2019年   172篇
  2018年   190篇
  2017年   157篇
  2016年   211篇
  2015年   202篇
  2014年   264篇
  2013年   292篇
  2012年   490篇
  2011年   534篇
  2010年   303篇
  2009年   286篇
  2008年   475篇
  2007年   465篇
  2006年   509篇
  2005年   527篇
  2004年   521篇
  2003年   507篇
  2002年   473篇
  2001年   286篇
  2000年   301篇
  1999年   302篇
  1998年   128篇
  1997年   87篇
  1996年   96篇
  1995年   73篇
  1994年   74篇
  1993年   69篇
  1992年   196篇
  1991年   159篇
  1990年   151篇
  1989年   145篇
  1988年   129篇
  1987年   133篇
  1986年   130篇
  1985年   117篇
  1984年   84篇
  1983年   59篇
  1981年   31篇
  1980年   27篇
  1979年   53篇
  1977年   44篇
  1975年   26篇
  1974年   29篇
  1971年   37篇
  1969年   29篇
  1968年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
By bioassay-guided fractionation using mushroom tyrosinase (EC 1.14.18.1), 2-hydroxy-4-methoxybenzaldehyde was characterized as the principal tyrosinase inhibitor from three East African medicinal plants, the root of Mondia whitei (Hook) Skeels (Asclepiaceae), the root of Rhus vulgaris Meikle (Anacardiaceae), and the bark of Sclerocarya caffra Sond (Anacardiaceae). It inhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by mushroom tyrosinase with an ID50 of 4.3 micrograms/ml (0.03 mM). The inhibition kinetics analyzed by a Lineweaver-Burk plot found this simple benzaldehyde derivative to be a mixed type inhibitor for this oxidation and affects on the enzyme in several ways. Based on finding this potent tyrosinase inhibitor, various related analogues were also tested in order to gain new insights into their inhibitory functions on a molecular basis.  相似文献   
102.
To investigate the mechanism of synovial pannus formation in rheumatoid arthritis, immunohistochemical and immunoelectron microscopic studies with monoclonal antibodies against the adhesion molecules, CD54 (ICAM-1), CD 11a (LFA-1), CDw49a (VLA-1), CDw49b (VLA-2), CDw49c (VLA-3), Cdw49d (VLA-4) and CDw49e (VLA-5), were carried out to determine the pattern of distribution of these molecules at the rheumatoid synovial cartilage junction. Treatment with anti-ICAM-1 resulted in membrane staining of most of the macrophages and fibroblasts infiltrating the synovial tissue and bordering the pannus-cartilage junction, suggesting the possibility that ICAM-1 may function to facilitate the adhesion of synovial type A cells bearing ICAM-1 to type B cells of the pannus. ICAM-1-positive macrophages and fibroblasts were often found to be in contact with lymphoid cells, suggesting also that a cellular immune reaction occurs in the formation of the pannus. In addition, VLA-3, VLA-4 and, particularly, VLA-5 were the predominant1 integrins expressed by rheumatoid synovial pannus. Since these three integrins all function as fibronectin receptors, it is possible that the fibronectin-rich environment of the rheumatoid cartilage surface effectively traps pannus cells expressing high levels of these molecules. The VLA-5 molecule was found in a pericellular and interterritorial matrix distribution in the present study, strongly suggesting that a recepfor-ligand interaction between VLA-5 and cartilage matrix may occur at the early stage of pannus formation. Furthermore, an increase in1 integrin may be necessary for the growth of the pannus and also for the upregulation of the VLA molecules, leading secondarily to increased attachment.  相似文献   
103.

Purpose

It is well established that hyperprolactinemia, most typically seen in prolactinoma patients, causes hypogonadism and impotence. There seem to be a good possibility that hyperprolactinemia causes impotence, at least partially via some intrinsic property of prolactin (PRL), rather than through its suppressive effects on the hypothalamic-pituitary-gonadal testosterone dynamics. In the present investigation, we used an in vitro canine model to attempt to clarify whether direct action of PRL on the corpus cavernosum penis may lead to erectile insufficiency. Growth hormone (GH) and placental lactogen (PL), both having close structural and functional homologies to PRL, were also studied.

Materials and Methods

Isometric tension measurement with cavernous strips was performed in the presence or absence of 10 sup -5 to 10 sup -9 M. PRL, GH, or PL in the perfusion medium. The tension change induced by the test substances was normalized relative to that induced by 120 mEq KCl.

Results

Both PRL and GH produced dose-related elevations (p less than 0.01) of the cavernous tension, whereas PL and thiol-cleaved PRL in comparable doses were without effect (p greater than 0.05). When the tension rise produced by 120 mEq KCl was taken as 100 percent, the maximum contractions produced by PRL and GH were 80 percent and 110 percent. The minimum effective concentration was 10 sup -8 to 10 sup -7 M. for both PRL and GH. Pretreatment with indomethacin (10 sup -5 M.), but not tetrodotoxin (10 sup -5 M.), partially suppressed (p less than 0.05) the effects of PRL.

Conclusion

These results suggest that PRL and GH directly and specifically produced contraction of the corpus cavernosum penis, resulting in erectile insufficiency, and that the effect of PRL is partially mediated by prostaglandin.  相似文献   
104.
Two children with intractable fecal incontinence after correction of high anorectal malformations were successfully managed by the daily administration of a glycerin enema into the cecum via an appendicocecostomy or tubularized cecostomy, according to the method of Malone's antegrade continence enema (ACE). Fluoroscopic defecography performed during this procedure in each patient disclosed that the glycerin enema promptly evoked cecal peristalsis, which was transmitted to the distal colon and rectum, and squeezed out almost all the fecal matter, evacuating it from the anus. However, two enemas within a short interval were required to achieve a complete washout of feces. Although this report describes only two patients, our experience confirmed that the ACE was very effective and that adding the word continence to antegrade enema was justifiable. Moreover, fluoroscopic defecography was proven to play a significant role in determining the appropriate regimens of this technique to achieve complete washout of the feces.  相似文献   
105.
A multiclinic double-blind controlled study was performed on the effects of MAP in both inpatients and outpatients with AMT as control drug.
  • 1 Subjects consisted of 41 male and 45 female patients suffering from various types of depression. MAP was assigned to 42 cases and AMT to 44 cases. Of these patients, 14 MAP cases and 10 AMT cases were subsequently dropped for a variety of reasons to obtain 28 MAP cases and 34 AMT cases as evaluable.
  • 2 The global improvement ratings were compared and found not significantly different for any week between the two treatments.
  • 3 The global improvement ratings by the characteristic features of patients did not show any significant difference in any items studied between the two treatments.
  • 4 The symptomatic improvement ratings (on the Hamilton R.S. for assessment by the physician) indicated that AMT was more effective on “anxiety (psychic).”
  • 5 The symptomatic improvement ratings (on the Beck self-assessment scale by the patient) indicated that MAP was more effective on “work” and AMT on “pathos”, “feeling of satisfaction”, “withdrawal” and “loss of libido.”
  • 6 During the treatment period, 74.3 percent of the MAP group and 76.9 percent of the AMT group of patients showed some side effects or accompanying symptoms, with no significant difference recognized between the two treatments. Itemwise, however, the incidence of tremor was significantly lower (p-=0.06) in the MAP group. Moreover, the MAP group tended to be less liable to such anti-cholinergic side effects as dry mouth, constipation, trouble of accommodation, urinary disturbance and palpitation.
  • 7 On the basis of the above findings, it is concluded that MAP is as effective against depression as AMT and less liable to the anticholinergic side effects. It is, therefore, a very useful antidepressant.
  相似文献   
106.
T Koyama  N Nakamura  T Wada  J Arita  M Matoba  M Kubo 《Brain and nerve》1991,43(12):1163-1168
A rare case of cranial fasciitis in a 1-year-old boy arising in the temporoparietal bone has been described. In 1990, Lauer and Endinger first reported cranial fasciitis, which is a benign subcutaneous tumor of the head developing from the deep fascia or the cranial periosteum and showing a pathological finding characterized by proliferation of fibroblasts. They described this tumor as "cranial fasciitis of childhood" in view of a high incident in infants and child. Cranial fasciitis grows rapidly in the scalp without pain, but its mean size is 2.5-3cm. Cranial fasciitis is closely related a clinical course and pathological findings to nodular fasciitis, which is also a benign proliferative fibroblast tumor developing from the subcutaneous muscular layers of the trunk and extremities (especially, the forearms), which was reported by Konwaler in 1955. However, cranial fasciitis differs from nodular fasciitis in that it is associated with the skull bone and, in many cases, the tumor destroys the inner and outer table of the skull and adheres to the dura mater. Cranial fasciitis should be considered to be a variant of nodular fasciitis. Neurosurgeons should be aware of this entity in the differential diagnosis of a firm lesion of the scalp in children. A brief review of the literature disclosed only 17 cases in the world. This case report is the first one of cranial fasciitis in Japan.  相似文献   
107.
During the past 8 yr, 37 patients with a noncorrectable type of biliary atresia have undergone hepatic portoenterostomy or portocholecystostomy at the Kobe Children's Hospital. The hepatic portal dissections employed in this series were classified as "supraportal" (9 procedures), "portal" (25 procedures), and "infra-portal" (3 procedures) based on the level at which the fibrous mass at the porta hepatis was transsected as determined by the operative record and the pathologic findings. Successful biliary drainage was achieved in 19 out of 25 patients (76%) with a "portal" type of dissection, while 1 out of 9 with "supra-portal" and none out of 3 with "infra-portal" type dissections were successful in this respect. Of the 19 patients who achieved significant biliary flow, 8 have lived for 2--7 yr without jaundice and 3 others are jaundice-free for shorter intervals.  相似文献   
108.
A 16-year-old female presented with a rare case of subepicranial varix in the left temporal area manifesting as a soft mass in the left temporal area when she laid down in the left lateral position. Bulging of the mass was observed when intracranial venous pressure was raised by the Valsalva maneuver, the left lateral position, or the prone position. Bone window computed tomography (CT) revealed a tiny hole, 1 mm in diameter, in the outer bone table. Three-dimensional CT (3D-CT) angiography clearly visualized a mass with a diameter of approximately 10 mm connected to the diploic vein. The mass was totally resected by operation. Venous bleeding was observed from the tiny hole. Histological examination revealed a venous lesion mimicking sinus pericranii and containing endothelial cells. No communication with the intracranial venous sinuses was identified, so the diagnosis was subepicranial varix. Radiological examination by direct injection of contrast medium is usually performed to identify subepicranial varix, but 3D-CT angiography is a non-invasive preoperative examination that can visualize this small venous lesion. Adjustment of the CT acquisition conditions may allow 3D-CT angiography to identify sinus pericranii in the future.  相似文献   
109.
Six cochlear implant recipients with hearing aids in the opposite ear were studied to survey binaural advantage. They were examined in separate tests by using a hearing aid alone, cochlear implant alone, and by using both devices (bimodal condition). Test items used were the Japanese monosyllable word list 67--S and Japanese HINT. Statistically significantly results were obtained in the bimodal condition, three out of six subjects were successful in the monosyllable word test and all successful in the Japanese HINT. We conclude that all subjects enjoyed binaural advantage in speech perception in bimodal condition with no conflict at the recognition level; even when different sounds from cochlear implant and contralateral hearing aid were received. The plasticity of the brain is thought to be of importance in the bimodal condition.  相似文献   
110.
We report a case of primary central nervous system (CNS) malignant lymphoma of the central nervous system originating from the cerebellum and growing along the lower cranial nerves. A 67-year-old woman presented with hoarseness, vertigo, nausea, and vomiting. Gd-DTPA enhanced MRI showed a homogeneous enhanced mass lesion extending from the cerebellum to the medulla oblongata around the jugular foramen on the right side. Although pre- and intra-operative diagnosis had been schwannoma, histopathological examination revealed a B-cell, diffuse malignant lymphoma. The growth pattern of malignant lymphoma in the present case, which extended extra-axially, is considered to be rare. We discuss here the growth patterns and difficulties of diagnosis of primary CNS malignant lymphoma in this area.  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