全文获取类型
收费全文 | 22339篇 |
免费 | 2198篇 |
国内免费 | 43篇 |
专业分类
耳鼻咽喉 | 371篇 |
儿科学 | 643篇 |
妇产科学 | 380篇 |
基础医学 | 3198篇 |
口腔科学 | 590篇 |
临床医学 | 2236篇 |
内科学 | 4076篇 |
皮肤病学 | 285篇 |
神经病学 | 1696篇 |
特种医学 | 752篇 |
外科学 | 3326篇 |
综合类 | 537篇 |
一般理论 | 26篇 |
预防医学 | 2431篇 |
眼科学 | 657篇 |
药学 | 1419篇 |
中国医学 | 19篇 |
肿瘤学 | 1938篇 |
出版年
2021年 | 295篇 |
2020年 | 171篇 |
2019年 | 259篇 |
2018年 | 340篇 |
2017年 | 260篇 |
2016年 | 301篇 |
2015年 | 331篇 |
2014年 | 469篇 |
2013年 | 705篇 |
2012年 | 1018篇 |
2011年 | 1001篇 |
2010年 | 548篇 |
2009年 | 491篇 |
2008年 | 885篇 |
2007年 | 997篇 |
2006年 | 955篇 |
2005年 | 977篇 |
2004年 | 873篇 |
2003年 | 879篇 |
2002年 | 795篇 |
2001年 | 758篇 |
2000年 | 765篇 |
1999年 | 671篇 |
1998年 | 278篇 |
1997年 | 256篇 |
1996年 | 251篇 |
1995年 | 225篇 |
1994年 | 230篇 |
1993年 | 216篇 |
1992年 | 583篇 |
1991年 | 518篇 |
1990年 | 485篇 |
1989年 | 512篇 |
1988年 | 441篇 |
1987年 | 428篇 |
1986年 | 403篇 |
1985年 | 390篇 |
1984年 | 321篇 |
1983年 | 260篇 |
1982年 | 201篇 |
1981年 | 212篇 |
1979年 | 292篇 |
1978年 | 262篇 |
1977年 | 178篇 |
1976年 | 167篇 |
1975年 | 189篇 |
1974年 | 253篇 |
1973年 | 195篇 |
1972年 | 203篇 |
1971年 | 169篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
We report on 4 children who experienced a syncopal episode while being treated with guanfacine without any other evident cause. Syncope appears to be an uncommon side effect of guanfacine and is probably due to drug-induced hypotension or bradycardia. 相似文献
12.
Palytoxin, a highly toxic natural product isolated from zoanthids of the genus Palythoa, is accumulated by a wide range of fishes and marine invertebrates used as food in the Indo-Pacific. It is responsible for many incidents of human morbidity and mortality. The toxin is a potent smooth muscle spasmogen. The cause of the contraction of smooth muscle is unclear, but recent work strongly suggests that it is primarily initiated by the release of neurotransmitters from the motor innervation of the smooth muscle. We show here that palytoxin caused the swelling of the muscle cells and some internal organelles of the anococcygeus muscle of the rat, but no substantial structural damage to the tissue. Axons and Schwann cells were also swollen but the most dramatic feature was the depletion of synaptic vesicles from putative release sites in the axons. Some axons were physically damaged following exposure to the toxin, but this was relatively uncommon (<10% of all axons studied). In the majority of axons there was no damage to nerve terminal membranes, but there was damage to mitochondria. The depletion of vesicles involved all types – clear, dense-cored, large and small. Our observations and pharmacological data gathered elsewhere, provide a neuropathological basis for the spasmogenic activity of palytoxin. 相似文献
13.
14.
Use of the inferior epigastric artery as a free graft for myocardial revascularization 总被引:3,自引:0,他引:3
H B Barner K S Naunheim A C Fiore V W Fischer H H Harris 《The Annals of thoracic surgery》1991,52(3):429-36; discussion 436-7
From March 1990 through January 1991, 47 patients undergoing myocardial revascularization had one (37) or both (10) inferior epigastric arteries (IEA) used as a conduit for bypass with 62 distal anastomoses. The internal thoracic artery (ITA) was used bilaterally in 41 patients and unilaterally in 6 with 100 distal anastomoses. Five patients had a single saphenous vein graft. In total, 167 anastomoses (3.55 per patient) were performed. Single IEA grafts were harvested through a paramedian incision and bilateral grafts, a midline incision. Harvest time was 36.5 minutes for IEA grafts and 29.6 minutes for ITA grafts (p less than 0.0001). Graft length was 11.9 cm for IEA grafts and 16.5 cm for ITA grafts (p less than 0.0001). Distal graft diameter was 2.0 mm for IEA grafts and 2.1 mm for ITA grafts (p less than 0.01). Graft flow was 49.7 mL/min for IEA grafts and 48.7 mL/min for ITA grafts. Microscopic assessment of segments of both the IEA and ITA from 14 patients revealed similar internal elastic laminae and an equal number of fenestrations. Combined intimal and medial thickness was comparable in both conduits. Medial elastic tissue was more prominent in ITA grafts and lacking in eight of the 14 IEA grafts. Gross plaque formation was noted in the proximal 1 to 3 cm of 50% of IEA grafts, but the lumen was not compromised and microscopic thickening was minimal. An unexpected finding was medial calcifications (M?nckeberg's disease) in two of the 14 IEAs without associated atherosclerosis. There was one hospital death, one abdominal wound infection, and one instance of fat necrosis superficial to the sternum.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
15.
Gordon J. Harris Ph.D. Instructor Jonathan M. Links Ph.D. Associate Professor Godfrey D. Pearlson M.B. B.S. Director Edwaldo E. Camargo M.D. Associate Professor 《Psychiatry research》1991,40(3):167-180
We developed a semiautomatic method termed “cortical circumferential profiling” for objective analysis of cerebral cortex function in emission tomographic neuroimaging studies. This method treats cortex as a continuous ring near the outer brain edge. A computer algorithm samples the cortex at 60 contiguous, equiangular locations, using 1-cm2 samples. These values are plotted as a function of cortical angle to produce the cortical circumferential profile. This method was used in a study of regional cerebral perfusion in 15 patients with Alzheimer's disease and 8 elderly control subjects using N-isopropyl [I-123]-iodoamphetamine. Cortical circumferential profiling decreases variability, examines the entire cortex within slices at preselected levels above the orbital-meatal line, and facilitates intrasubject and intersubject comparisons. 相似文献
16.
The 5-year results of a randomized trial of adjuvant radiation therapy after chemotherapy in breast cancer patients treated with mastectomy 总被引:4,自引:0,他引:4
K L Griem I C Henderson R Gelman D Ascoli B Silver A Recht R L Goodman S Hellman J R Harris 《Journal of clinical oncology》1987,5(10):1546-1555
The use of adjuvant radiation therapy in breast cancer patients treated with mastectomy and adjuvant chemotherapy has been controversial. In order to assess the necessity and effectiveness of adjuvant radiation therapy in this setting, we reviewed the results in 510 patients with T1-T3 tumors and pathologically positive nodes or tumors larger than 5 cm and negative nodes who were treated with adjuvant chemotherapy. Patients with four or more positive nodes or at least one positive apical node were randomized to receive either five or ten cycles of cyclophosphamide/Adriamycin (Adria Laboratories, Columbus, OH) (CA) and patients with one to three positive nodes or operable tumors larger than 5 cm and pathologically negative nodes were randomized to receive eight cycles of either cyclophosphamide, methotrexate, and 5-fluorouracil (5-FU) (CMF) or methotrexate and 5-FU (MF) chemotherapy. Two hundred six of these patients were subsequently rerandomized to receive either no further treatment or adjuvant radiotherapy. Thirty-five patients withdrew after randomization, including 34 who declined to receive radiotherapy. Radiation therapy consisted of 4,500 cGy in 5 weeks to the chest wall and appropriate draining lymph nodes. Median follow-up from chemotherapy randomization is 45 months for patients in the CA arm and 53 months for those in the CMF/MF arm. The crude rate of local failure (chest wall or draining lymph node areas) as first site of failure for patients randomized to receive chemotherapy only was 14%; for those randomized to receive both chemotherapy and radiotherapy it was 5% (P = .03). For patients in the CMF/MF arm, the rate of local failure as the first site of failure was nearly the same for patients randomized to chemotherapy only as for those randomized to adjuvant radiotherapy as well (5% v 2%). For patients in the CA arm, the crude rate of local failure was 20% for patients randomized to receive chemotherapy only, and 6% for those randomized to both types of adjuvant treatment (P = .03). Among the 43 patients treated with CA who actually received radiotherapy, there was only one local failure, compared with 12 local failures among the 59 patients (20%) who actually did not receive radiotherapy (P = .007). No significant difference was seen in disease-free survival or overall survival in either the CA or the CMF/MF arm between patients randomized to receive radiation therapy and those randomized to no further treatment.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
17.
Long-term results of pectoralis major muscle transposition for infected sternotomy wounds. 总被引:1,自引:0,他引:1 下载免费PDF全文
During an 11.5-year period, 100 consecutive patients (79 male, 21 female) underwent repair of an infected sternotomy wound. Sixty-five patients had failed attempts at wound closure by other physicians. Median age was 61.5 years (range, 5 to 85 years). Reconstruction included muscle in 79 patients, omentum in 4, and both in 15. A total of 175 muscles were transposed, including 169 pectoralis major, 3 rectus abdominis, 2 external oblique, and 1 latissimus dorsi. Median number of operations was four (range, 1 to 11). Mechanical ventilation was required in 30 patients. Two perioperative deaths occurred, one related to sepsis. Median follow-up was 4.2 years (range, 1.3 to 13.5 years). Twenty-six patients had recurrent infection. Median time from our closure to recurrence was 5.5 months (range, 0.3 to 27.6 months). Cause of recurrence was inadequate removal of cartilage in 16 patients, bone in 6, and retained foreign body in 4. Eighteen patients had the wound reopened with further resection; 10 had another muscle or omentum transposition. There were 30 late deaths, only one related to recurrent infection. At the time of death or last follow-up, 92 patients had a healed chest wall. Transposition of the pectoralis major muscle remains an excellent method of management for infected sternotomy wounds. Failure is directly related to persistent infection of cartilage, bone, or retained foreign bodies. 相似文献
18.
19.
Leonard A. Jason PhD Steven B. Pokorny PhD Monica Adams MPH Annie Topliff MA Courtney Harris BA Yvonne Hunt PhD 《The American journal on addictions / American Academy of Psychiatrists in Alcoholism and Addictions》2009,18(5):367-374
This study evaluated the effects of tobacco Purchase, Use and Possession (PUP) laws on student perceptions of adolescent tobacco use within towns and schools. Twenty‐four towns were randomly assigned into two conditions, the experimental condition (E PUP) involved efforts to increase both PUP law enforcement and reduce minors' access to commercial sources of tobacco, whereas the control condition (C) focused only on efforts to reduce minors' access to commercial sources of tobacco. A hierarchical linear modeling analytical approach was selected due to the multilevel data and nested design. The present study found that over time, youth in the experimental PUP condition observed less youth tobacco usage at school and in their town, and perceived lower rates of tobacco among their peers at school and among friends than youth in the control condition. The findings suggest that PUP law enforcement might be used to strengthen community norms against youth tobacco use. 相似文献
20.
U. Logonder Z. Jenko-Pranikar T. Scott-Davey J. Punger
ar I. Kriaj J.B. Harris 《Experimental neurology》2009,219(2):591-594
A mutant form of ammodytoxin A, a neurotoxic phospholipase A2 from the venom of the long nosed viper Vipera ammodytes ammodytes, was prepared by site-directed mutagenesis, conjugated to a nanogold particle and inoculated into the antero-lateral aspect of one hind limb of female mice. Eight hours later the mice were killed, the soleus muscles of both ipsi- and contra-lateral hind limbs were removed, exposed to a silver enhancing medium and then prepared for transmission electron microscopy. Silver-enhanced particles were subsequently found concentrated in the peri-synaptic area, particularly within the synaptic gutter and the deep synaptic folds, and in many cases had been taken up into the cytoplasm of the terminal boutons of the motor axon. The results suggest that the presynaptic neurotoxicity of snake venom phospholipases A2 involves several components of the neuromuscular apparatus, including intracellular organelles of the motor nerve terminal. 相似文献