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   1803525篇
  免费   116613篇
  国内免费   3359篇
耳鼻咽喉   25800篇
儿科学   55014篇
妇产科学   49507篇
基础医学   270221篇
口腔科学   50835篇
临床医学   156144篇
内科学   343672篇
皮肤病学   40668篇
神经病学   135220篇
特种医学   71028篇
外国民族医学   483篇
外科学   277216篇
综合类   37502篇
现状与发展   8篇
一般理论   536篇
预防医学   126857篇
眼科学   42002篇
药学   137153篇
  5篇
中国医学   3987篇
肿瘤学   99639篇
  2018年   16683篇
  2016年   14763篇
  2015年   16491篇
  2014年   22784篇
  2013年   34410篇
  2012年   46578篇
  2011年   50268篇
  2010年   29494篇
  2009年   27863篇
  2008年   47393篇
  2007年   52135篇
  2006年   52187篇
  2005年   50469篇
  2004年   49180篇
  2003年   47577篇
  2002年   46685篇
  2001年   82371篇
  2000年   84541篇
  1999年   71169篇
  1998年   19208篇
  1997年   17159篇
  1996年   16657篇
  1995年   15702篇
  1994年   14574篇
  1992年   55106篇
  1991年   55259篇
  1990年   54632篇
  1989年   53488篇
  1988年   49591篇
  1987年   49081篇
  1986年   46626篇
  1985年   44454篇
  1984年   33081篇
  1983年   28088篇
  1982年   16302篇
  1981年   14888篇
  1979年   31880篇
  1978年   22784篇
  1977年   19381篇
  1976年   18310篇
  1975年   21191篇
  1974年   24769篇
  1973年   24003篇
  1972年   22815篇
  1971年   21463篇
  1970年   20289篇
  1969年   19370篇
  1968年   18174篇
  1967年   16289篇
  1966年   14895篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Uveal melanoma radiation. 125I brachytherapy versus helium ion irradiation   总被引:4,自引:0,他引:4  
The optimum radiation therapy for uveal melanoma is uncertain. Both helium ion irradiation and 125I brachytherapy have been used to treat this neoplasm. This investigation analyzed the control and complication rates of uveal melanomas treated with helium ions of 125I plaques. In both a retrospective and a prospective dynamically balanced study, the control rates appeared to be similar. There were more posterior segment complications after 125I plaques and more anterior segment complications, including neovascular glaucoma, after helium ion irradiation. The follow-up period is too short to draw definitive conclusions on the radiation complications. Overall, approximately 89% of eyes were retained and less than 4% of treated eyes were removed because of failure to control the tumor.  相似文献   
992.
Effects of vasodilator drugs on venous tone in conscious rats   总被引:1,自引:0,他引:1  
The dose-response effects of vasodilator drugs, nitroglycerin, sodium nitroprusside and hydralazine, on mean arterial pressure (MAP) and mean circulatory filling pressure (MCFP), an index of body venous tone, were investigated in conscious, unrestrained, intact rats as well as in rats treated with the ganglionic blocker, hexamethonium. The effects of these drugs were compared with those of the vehicle, normal saline, in control rats. In intact rats, i.v. infusion of nitroglycerin did not alter MAP while i.v. infusions of nitroprusside or hydralazine caused dose-dependent decreases in MAP. After ganglionic blockade, all three drugs decreased MAP. In intact rats, nitroglycerin and sodium nitroprusside did not affect MCFP but hydralazine increased MCFP. After treatment with hexamethonium, all three drugs decreased MCFP. The decreases in MCFP caused by nitroglycerin and nitroprusside, but not that by hydralazine, were significantly greater than the corresponding changes in control rats. Thus, in intact rats, the direct venodilator actions of nitroprusside and nitroglycerin were masked by endogenous sympathetic tone. When sympathetic nerve activity was attenuated, both nitroprusside and nitroglycerin have venodilator effects. Hydralazine, on the other hand, had insignificant venodilator effect both in the presence and absence of sympathetic reflexes.  相似文献   
993.
A case of a young Japanese woman with long-standing ulcerative colitis complicated by preinfarction angina due to Takayasu's aortitis is presented. Successful emergency aorto-coronary bypass operation was performed. Whether the association of these two diseases can be explained by a common mechanism is discussed.  相似文献   
994.
St. Jude Medical valve replacement was performed in 1,039 patients; 320 had aortic (AVR), 543 mitral (MVR), and 176 had double valve replacement (DVR). There were 44(4.2%) early deaths. Follow-up extended in 995 patients from 10 to 130 months, with a cumulative period of 2,730 patients-years. The overall survival rates of AVR, MVR, and DVR patients at 10 years were 60.5%, 89.6%, 90.3% respectively. The linearized incidences of valve thrombosis, thromboembolism, anticoagulation-related hemorrhage, prosthetic valve endocarditis, and significant hemolysis were as follows: 0.11%/pt-yr, 1.33%/pt-yr, 0.04%/pt-yr, 0.18%/pt-yr, and 0.11%/pt-yr, respectively. There were no structural failure after 10 years follow-up. Reoperation (explant and re-replacement or suture repair) was required in 10 patients. Seven of them had periprosthetic leakage, 2 had valve thrombosis, and one underwent reoperation because of a technical error. Actuarially over 98% of patients were free of valve-related mortality at 10 years. St. Jude Medical valve is an excellent alternative for use in the surgical treatment of valvular heart disease.  相似文献   
995.
The first phase of data bank of hazard (DBH) of polymers has been developed and put into operation on the basis of CM-computers. DBH is a factographical computer-based system of data collection, storage and processing aimed at complex assessment of material and substance hazard. Systems approach to the analysis of material's characteristics serves as a methodological basis. DBH data base includes a set of input and output documents according to 5 types of biological hazards involving sanitary and chemical surveillance, fire hazard and thermodestruction, the data on material's microbiologic resistance, their electrifying and toxicohygienic characteristics. DUAMC-3 operational system, DUAMC. DBH software are included into the system of data banks of materials' technological properties.  相似文献   
996.
997.
A sample of 110 consecutive first admission young schizophrenic patients treated between 1964 and 1967 was rediagnosed in 1981. Among 92 survivors, 27 could be labelled as paraphrenics. From information available at inception 97 variables were coded covering such areas as personality, previous disturbances, age and type of onset, and symptoms around admission. Sixty-three out of 97 variables were hypothesized to differentiate, at admission, future paraphrenics from the rest of the sample. Paraphrenics were found to have had less contact disturbance, better self-esteem, less neurotic symptoms in adolescence and childhood, and less complaints of unhappiness when growing up. They had more regressive and paranoid symptoms at admission, were older at onset of the disease, which was more acute, more often connected with precipitating events, and confusion. Certain non-regressive symptoms such as brooding, anhedonia and concentration difficulties were less common. A discriminant analysis yielded a proportion of correct predictions = 0.64 (p less than 0.05). The results are in accordance with the theory of more favourable energetic and organizational capacity in paranoid schizophrenics as compared with non-paranoids.  相似文献   
998.
Stretch-shortening cycle (SSC), which is a normal contraction behavior of muscle, was used as a model to investigate muscular fatigue. Nine male volunteers were subjected to 100 repeated and exhaustive SSC contractions of the forearm extensors using a special sledge apparatus incorporating a force plate system. The fatigue contractions were performed on submaximal levels but the before-after comparison also included maximal drop-jump condition on the sledge as well as falls on to the floor. The results indicated that in the 100 submaximal SSCs the fatigue was characterized by increases in the contact times for both the eccentric and concentric phases of SSC, but the influence was more pronounced on the concentric part. The force-time curves during contact on the platform were influenced by fatigue so that the initial force peak became higher and the subsequent initial drop of force more pronounced. During submaximal and maximal drops, the angular velocities changed in the two phases of SSC. With progressing fatigue, the eccentric maximal angular velocity increased and the corresponding concentric velocities decreased. These changes were accompanied by slight changes in the elbow joint mechanism with respect to the contact, release, and maximal flexion angles. The results suggest that repeated SSC induces fatigue and the fatigue effects on the mechanical behavior of the muscle are very much similar to those induced by either isometric or concentric fatigue contractions. However, the transfer of the energy between eccentric and concentric phases was drastically reduced and this implies that SSCs can be used effectively to examine the fatiguability of the system regulating muscle stiffness during exercise.  相似文献   
999.
In the cat synapses between vesicle containing profiles were observed in ventral and dorsolateral pontine nuclei. The presynaptic elements consisted of two types of axon terminals: axon terminals characterized by a population of small (38-40 nm) round synaptic vesicles (SSV) and axon terminals containing pleomorphic synaptic vesicles (PSV). The postsynaptic pale elements (PP) had pleomorphic vesicles and some features attributed to dendrites. In the dorsolateral pontine nucleus most of PP profiles took part in serial synapses, usually as an intermediate component, they were rarely observed in triads. On the basis of their electron microscopical appearance and synaptic relations they might be considered to represent a dendritic part of putative interneurons.  相似文献   
1000.
In the upper limb, diffuse cavernous haemangiomas occur infrequently but their treatment is often unsatisfactory and the result of surgical excision disappointing. Four cases of these diffuse haemangiomas are described and their management discussed.  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