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   24941篇
  免费   1181篇
  国内免费   114篇
耳鼻咽喉   194篇
儿科学   426篇
妇产科学   434篇
基础医学   3197篇
口腔科学   588篇
临床医学   1503篇
内科学   6106篇
皮肤病学   338篇
神经病学   2205篇
特种医学   907篇
外科学   4108篇
综合类   113篇
一般理论   1篇
预防医学   683篇
眼科学   740篇
药学   1924篇
中国医学   84篇
肿瘤学   2685篇
  2023年   104篇
  2022年   186篇
  2021年   348篇
  2020年   277篇
  2019年   330篇
  2018年   397篇
  2017年   314篇
  2016年   419篇
  2015年   405篇
  2014年   542篇
  2013年   684篇
  2012年   1081篇
  2011年   1163篇
  2010年   676篇
  2009年   543篇
  2008年   1095篇
  2007年   1095篇
  2006年   1096篇
  2005年   1162篇
  2004年   1262篇
  2003年   1174篇
  2002年   1178篇
  2001年   938篇
  2000年   960篇
  1999年   883篇
  1998年   362篇
  1997年   276篇
  1996年   240篇
  1995年   212篇
  1994年   203篇
  1993年   189篇
  1992年   646篇
  1991年   551篇
  1990年   571篇
  1989年   547篇
  1988年   475篇
  1987年   415篇
  1986年   404篇
  1985年   384篇
  1984年   285篇
  1983年   225篇
  1982年   115篇
  1979年   193篇
  1978年   135篇
  1977年   139篇
  1974年   105篇
  1972年   110篇
  1971年   114篇
  1968年   111篇
  1967年   98篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
A case of cystadenocarcinoma of the liver is reported. The patient was a 73-year-old woman in whom a tumor was detected in the lateral segment of the liver during a health examination. Ultrasonograms and computed tomograms showed a multilocular cystic mass. Magnetic resonance imaging (MRI) showed a multilocular lowintensity mass, including a high-intensity portion and a portal branch compressed by the tumor. MRI with gadolinium showed an enhanced cyst wall. The cystic part of the tumor became smaller and the solid part became larger over a 1-month period, indicating that the tumor was malignant. Subsegmentectomy (S3) was performed and cystadenocarcinoma with cystadenoma was diagnosed by histopathological examination. Identification of changes in the appearance of a tumor should be helpful for the differential diagnosis of cystadenoma and cystadenocarcinoma.  相似文献   
12.
The aim of this study was to investigate retrospectively the efficacy of expandable metallic stents (EMSs) for severe respiratory distress in patients with central airway obstruction. Twenty patients with central airway obstructions were treated with an EMS. An intraluminal stricture was present in 15 and an extraluminal stricture in 5 patients. Of the 15 patients with intraluminal stenosis, 11 exhibited symptomatic improvement. All 11 patients had tumor infiltration occupying less than 50% of the endoluminal diameter. The other four patients with intraluminal stenosis had tumor infiltration occupying > 50% of the endoluminal diameter and demonstrated no improvement. All five patients with extraluminal stenosis were improved. EMS is useful for an extraluminal stricture in the central airway and the effect of EMS for intraluminal stenosis is related to the degree of infiltration and of tumor progression itself.   相似文献   
13.
The surgical treatment of 100 cases with congenital dilatation of bile duct with special reference to late complications was analyzed. There were no deaths nor occurrences of malignancy. Among 91 patients who had undergone the standard operation, namely total excision of the dilated extrahepatic bile duct and reconstruction after Roux-en-Y hepaticojejunostomy, there were one early complication (pancreatic juice leakage) and five late complications (four intrahepatic gallstones and one liver abscess). The cause of intrahepatic gallstone formation after a total excisional operation was attributed to the remaining intrahepatic bile duct dilatation and the stenosis located between the intrahepatic bile duct dilatation and the common hepatic duct. Accordingly, these results support the total excisional procedure for this condition; however, with regard to the cases associated with cystic dilatation of intrahepatic bile ducts, completely free bile drainage from the dilated intrahepatic biliary system should be performed at the radical operation.  相似文献   
14.
One hundred fifty-three inpatients with alcohol dependence syndrome were treated with the structured BDIM (Before-Discharge Intervention Method). 82 patients of them have participated to self-help group meetings or kept having therapy as our outpatients or inpatients during the study period. We chose the families of the 82 patients as our study subject Out of the study subjects who took part in BDIM, 64 families (117 persons) answered our questionnaire. Among them 63 families (101 persons) gave their described answers of impressions and opinions about BDIM, which were summarized as follows. (1) Through BDIM the family members gained second thought on their alcoholic family member (IP: identified patient) and they could tell their new view to IP. BDIM enabled them to tell IP their sincere feeling and hope for recovery of IP. BDIM empowered both IP and IP's family members. (2) The family members became to know IP's orientation on his or her disease. They came to know IP's denial and understand him or her as he or she was. (3) The family members felt emotional ties among themselves and IP through BDIM. When the family members of a dysfunctional family took part together in BDIM, they could know the feelings, thoughts, experiences and hopes one another. The family members had a precious experience of mutual understanding among themselves and IP to hope for recovery together. (4) The family members appreciated BDIM as a effective therapy. In BDIM many of them regarded highly of giving their letters to IP as a useful method to convey their feeling and thoughts calmly to IP. (5) On the other hand some family members pointed out the difficulty for themselves to write on BDIM. For family members who are not good at writing a letter or tend only to blame IP through their letters, writing and giving letters to IP is not appropriate as a therapy. If family members feel strong anxiety or fear, it is safe not to practice BDIM.  相似文献   
15.
The effect of ascorbate on the release of acetylcholine from the longitudinal muscle-myenteric plexus preparation of the guinea-pig isolated ileum has been investigated using a bioassay and an isotopic technique. Ascorbate at 5 mM increased the spontaneous output of acetylcholine and enhanced DMPP-induced output of acetylcholine, while iso-ascorbate, 5 mM, did not. Ascorbate did not influence either the spontaneous or the DMPP-induced release of acetylcholine from synaptosomes of the ileal myenteric plexus. These results suggest that ascorbate promotes acetylcholine release from intramural cholinergic nerves.  相似文献   
16.
A 67-year-old woman, who presented polyneuropathy, pleural effusion, ascites and sclerosing changes in the ribs, was admitted to our hospital on June 17, 1987. On admission, cerebrospinal examination showed a marked protein-cell dissociation and a delay in nerve conduction velocity. Bence-Jones protein was detected in urine, and the immunohistochemical study of biopsied bone marrow of the rib revealed lambda-chain positive plasmacytoma. Serum immunoelectrophoresis, however, showed no monoclonal gamma-globulinemia. From the findings described above, she was diagnosed as having Crow-Fukase syndrome associated with lambda-type light chain disease. Even with a therapy by prednisolone, platelet counts progressively declined to 10,000/ml3. Bone marrow aspiration showed normal number of megakaryocytes. Since platelet-associated IgG was increased to 452 ng/1.0 x 10(8) plt, a diagnosis of autoimmune thrombocytopenia was considered. Melphalan and cyclophosphamide to plasmacytoma resulted in a marked improvement of platelets. In addition, the level of platelet-associated IgG returned to normal range. Polyneuropathy, however, didn't respond to those therapies. It was suggested that both Crow-Fukase syndrome and thrombocytopenia were closely concerned with plasmacytoma but developed in a different manner.  相似文献   
17.
A brief historical review of the role of female medical students and female physicians in American medicine is presented. The 1985-1986 Council on Resident Education in Obstetrics and Gynecology Residency Data Bank was analyzed for gender distribution. Questionnaire studies were undertaken to study the possible effect of the increasing number of female residents in an obstetrics and gynecology residency program. Queries were sent to current and former residents, the attending staff, and the nursing and anesthesiology staffs. In order to evaluate the national scene, letters were mailed to directors of programs with 20 or more residents. The overall results indicated female residents have a positive effect on residency training.  相似文献   
18.
Pyroglutamyl, proline-rich oligopeptides, classically referred to as bradykinin-potentiating peptides (BPPs) are found in Bothrops jararaca venom, and are naturally occurring inhibitors of the somatic angiotensin-converting enzyme (ACE). The chemical and pharmacological properties of these peptides were essential for the development of captopril, the first active site directed inhibitor of ACE, currently used to treat human hypertension. ACE is a complex ectoenzyme of the vascular endothelium, possessing two catalytic sites, performing diverse specific roles. Recent advances concerning novel features of BPPs revealed that they might still contribute to a better understanding of the cardiovascular physiology and pathology. The molecular biology of the BPPs revealed that they are part of two distinct C-type natriuretic peptide precursors found in the venom gland and the brain of B. jararaca, each containing seven BPPs. In situ hybridization studies detected the presence of the corresponding mRNA precursor in snake brain regions correlated with neuroendocrine functions, such as the ventro-medial hypothalamus, the paraventricular nuclei, the paraventricular organ, and the subcommissural organ. In this article we discuss the large variety of homologous BPPs in B. jararaca venom and brain, its significance, and whether the BPPs could represent novel endogenous neuropeptides.  相似文献   
19.
The effects of methyl 2,6-dimethyl-4-(2-nitrophenyl)-5-(2-oxo-1,3,2-dioxaphosphorinan-2- yl)-1,4- dihydropyridine 3-carboxylate (DHP-218), a new dihydropyridine calcium antagonist, on vascular smooth muscles, cardiac muscles and [3H]-nitrendipine binding to the cardiac muscle and brain membranes were investigated in vitro. Vascular smooth muscles: Calcium-induced contraction of the rat aorta in high K+ solution was inhibited by DHP-218 with the pA2 value of 9.11. The IC50 value for the inhibitory effects of this compound in high K+-induced and phenylephrine-induced contraction was 6.3 nmol/l and 66 nmol/l, respectively. Vasodilatory effects of this drug on various blood vessels of rabbits contracted by high K+ appeared to a similar extent. The onset of the vasodilatory effect was very slow and the recovery rate of vasodilatory response after washout with the bathing solution containing high K+ or phenylephrine was also very slow. Cardiac muscles: Negative chronotropic and inotropic actions were observed at concentrations more than 30 and 100 nmol/l, respectively. Duration of the plateau phase of normal action potential was shortened and the amplitude and duration of slow action potential were reduced at concentrations more than 1 mumol/l. Very high vasculoselectivity was observed. Displacement of [3H]-nitrendipine binding: The pattern of displacement of [3H]-nitrendipine binding by DHP-218 was very similar to that of other 1,4-dihydropyridines but this compound was about 70 times less potent than nifedipine in [3H]-nitrendipine displacement capacity. These results indicate that DHP-218 has specific vasodilatory action due to calcium antagonism, but association and dissociation rates with tissue and receptors were different from those of nifedipine.  相似文献   
20.
OBJECTIVES: Bronchiolitis obliterans (BO) is the main cause of late mortality among long-term survivors of lung transplantation. Chemokine-chemokine receptor (CCR) interaction and subsequent recruitment of infiltrating cells to the graft are early events in the development of chronic rejection of transplanted lungs. The present study investigated whether blockade of chemokine receptors CCR1 and CCR5 with Met-regulated-on-activation, normal T cells expressed and secreted (RANTES), an amino-terminal modified derivative of RANTES/CCL5, affects the development of BO in murine model and we sought to determine the expression of RANTES/CCL5 and their relationship with extracellular signal-regulated kinase (ERK). Materials and Methods: BALB/c mouse tracheas were heterotopically transplanted into C57Black6 recipients and treated for 21 days with either Met-RANTES at 20 microg/day or vehicle. Animals were killed at 21 days after transplantation for histologic examination of ERK expression. RESULTS: RANTES/CCL5 was highly expressed in allografts compare to isografts. Met-RANTES treatment ameliorated fibrous airway obliteration in a mouse model of BO and decreased ERK expression. CONCLUSION: Blockade of chemokine receptors by Met-RANTES ameliorated airway obliteration and decreased ERK expression. These findings suggest that chemokine receptors CCR1 and CCR5 play significant roles in the development of chronic rejection and ERK may be a new molecular target for chronic rejection.  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