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   34914篇
  免费   1654篇
  国内免费   217篇
耳鼻咽喉   301篇
儿科学   614篇
妇产科学   458篇
基础医学   4548篇
口腔科学   772篇
临床医学   2236篇
内科学   8980篇
皮肤病学   692篇
神经病学   2943篇
特种医学   1272篇
外科学   5642篇
综合类   133篇
一般理论   5篇
预防医学   859篇
眼科学   1139篇
药学   2509篇
中国医学   93篇
肿瘤学   3589篇
  2023年   157篇
  2022年   321篇
  2021年   675篇
  2020年   417篇
  2019年   479篇
  2018年   616篇
  2017年   485篇
  2016年   650篇
  2015年   698篇
  2014年   889篇
  2013年   1105篇
  2012年   1845篇
  2011年   1965篇
  2010年   1141篇
  2009年   953篇
  2008年   1724篇
  2007年   1895篇
  2006年   1758篇
  2005年   1941篇
  2004年   1997篇
  2003年   1786篇
  2002年   1860篇
  2001年   982篇
  2000年   960篇
  1999年   959篇
  1998年   533篇
  1997年   391篇
  1996年   375篇
  1995年   329篇
  1994年   298篇
  1993年   288篇
  1992年   632篇
  1991年   537篇
  1990年   553篇
  1989年   547篇
  1988年   469篇
  1987年   389篇
  1986年   391篇
  1985年   388篇
  1984年   283篇
  1983年   215篇
  1982年   124篇
  1981年   108篇
  1979年   193篇
  1978年   154篇
  1977年   139篇
  1974年   98篇
  1971年   100篇
  1968年   99篇
  1967年   96篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
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   
22.
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   
23.
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   
24.
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   
25.
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   
26.
Invasive aspergillosis (IA) is a severe complication of liver transplantation. Risk factors for IA after deceased donor liver transplantation (DDLT) have been presented in several reports, but are not well established for living donor liver transplant recipients. Here, a retrospective case-control study was performed. Five cases with IA were investigated after living donor liver transplantation (LDLT) between January 1999 and December 2002 at Kyoto University Hospital. For comparison, living donor liver transplant recipients without IA were taken as controls. These patients had undergone LDLT 1 month before or after each IA case and had the same survival times as the latter. We evaluated the clinical and laboratory findings for both groups up until their demise. Patients with IA after LDLT had a very poor prognosis. By univariate analysis, risk factors for IA were preoperative intensive care unit stay (P = 0.02) and preoperative steroid administration (P = 0.02). Preoperative steroid administration for fulminant hepatitis possibly predisposed to the development of IA after LDLT.  相似文献   
27.
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   
28.
Deceased donor factors associated with poor graft outcome are well known, but how often these factors lead to livers left untransplanted is poorly defined. A nested, case-control study was conducted using the United Network for Organ Sharing (UNOS) database from 1987 to 2005. Only those donating >/=1 solid organ were included. Primary outcome was livers not transplanted (LNT, cases) versus transplanted (LT, controls). Primary variables for multivariate analysis were donor age and obesity. Covariates included donation after cardiac death (DCD), cerebral vascular accident death, viral serologies, cancer, ALT and bilirubin. There were 23 373 (26%) LNT's from 91 362 donors who donated at least one organ. Percent LNT fell over time (1987-1990: 48%; 1991-1995: 29%; 1996-2000: 21%; 2000-2005: 16%; p < 0.01). Increased age (odds ratio: 4.2, 95% confidence interval 3.6-4.9, p < 0.01) and obesity (2.1, 1.9-2.3, p < 0.01) were significantly associated with LNT across all time periods. Other significant factors included DCD and elevated ALT. For 2001-2005, population attributable risk indicate that age >40, abnormal ALT and obesity account for 32.6%, 25.3% and 9.2% of untransplanted livers, respectively. Use of expanded criteria livers has pushed LNT lower in spite of an aging and heavier donor population. Nevertheless, age and obesity still account for a significant portion of untransplanted livers.  相似文献   
29.
Background: We evaluated the endoscopic microvascular architecture of the gastric mucosa in portal hypertension patients using the prototype of narrow band imaging (NBI). Material and Methods: The study included 103 Helicobacter pylori‐negative patients with chronic liver disease (22 without portal hypertension (group 1), 81 with portal hypertension (group 2)). Results: (i) Abnormality of collecting venules, reddening mucosa, red spots, a mosaic‐like pattern, and gastric antral vascular ectasia (GAVE) were observed on the gastric mucosa, and an obscure change in collecting venules (73% vs 14%; P < 0.001), reddening mucosa (49% vs 5%; P < 0.001), red spots (36% vs 5%; P < 0.01) and a mosaic‐like pattern (40% vs 5%; P < 0.01) were more frequently observed in group 2 than in group 1. (ii) On magnifying endoscopy with NBI, the mucosa with an obscure change in collecting venules was demonstrated as dilation of the capillaries surrounding the gastric pits in various degrees, and reddening mucosa was observed as extended and swollen gastric pits and various degrees of dilated and convoluted capillaries surrounding the gastric pits. Red spots were demonstrated as extended and swollen gastric pits, dilated and convoluted capillaries surrounding the gastric pits, and intramucosal hemorrhage around these capillaries. GAVE was recognized as partial and marked dilatation of the capillaries surrounding the gastric pits. Conclusion: Abnormality of collecting venules, swelling of gastric pits, dilatation of capillaries surrounding the gastric pits, intramucosal hemorrhage around capillaries, and partial and marked dilatation of the capillaries were observed on the gastric mucosa in portal hypertension patients.  相似文献   
30.
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