全文获取类型
收费全文 | 1073343篇 |
免费 | 73151篇 |
国内免费 | 1361篇 |
专业分类
耳鼻咽喉 | 15015篇 |
儿科学 | 34606篇 |
妇产科学 | 28625篇 |
基础医学 | 153390篇 |
口腔科学 | 29553篇 |
临床医学 | 94905篇 |
内科学 | 203627篇 |
皮肤病学 | 24391篇 |
神经病学 | 81436篇 |
特种医学 | 42961篇 |
外国民族医学 | 201篇 |
外科学 | 163088篇 |
综合类 | 21702篇 |
现状与发展 | 1篇 |
一般理论 | 263篇 |
预防医学 | 74600篇 |
眼科学 | 24535篇 |
药学 | 86103篇 |
7篇 | |
中国医学 | 2805篇 |
肿瘤学 | 66041篇 |
出版年
2019年 | 7755篇 |
2018年 | 11293篇 |
2017年 | 8906篇 |
2016年 | 10095篇 |
2015年 | 11260篇 |
2014年 | 15268篇 |
2013年 | 22197篇 |
2012年 | 30543篇 |
2011年 | 32286篇 |
2010年 | 18949篇 |
2009年 | 17814篇 |
2008年 | 29944篇 |
2007年 | 32065篇 |
2006年 | 32698篇 |
2005年 | 31028篇 |
2004年 | 29722篇 |
2003年 | 28549篇 |
2002年 | 27524篇 |
2001年 | 60019篇 |
2000年 | 61475篇 |
1999年 | 50929篇 |
1998年 | 12443篇 |
1997年 | 10999篇 |
1996年 | 11014篇 |
1995年 | 10320篇 |
1994年 | 9341篇 |
1993年 | 8857篇 |
1992年 | 37788篇 |
1991年 | 36273篇 |
1990年 | 35744篇 |
1989年 | 34285篇 |
1988年 | 30865篇 |
1987年 | 29986篇 |
1986年 | 28215篇 |
1985年 | 26448篇 |
1984年 | 19185篇 |
1983年 | 16113篇 |
1982年 | 8822篇 |
1979年 | 17029篇 |
1978年 | 11404篇 |
1977年 | 10229篇 |
1976年 | 8837篇 |
1975年 | 10068篇 |
1974年 | 11651篇 |
1973年 | 11273篇 |
1972年 | 10754篇 |
1971年 | 10092篇 |
1970年 | 9252篇 |
1969年 | 8938篇 |
1968年 | 7917篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Design of Case-controls Studies with Unscreened Controls 总被引:2,自引:0,他引:2
Traditionally in genetic case‐control studies controls have been screened to exclude subjects with a personal history of illness. This control group has the advantage of optimal power to detect loci involved in illness, but requires more work and may incur substantial cost in recruitment. An alternative approach to screening is to use unscreened controls sampled from the general population. Such controls are generally plentiful and inexpensive, but in general there is a risk that some may have the same disease as the cases, which will reduce power to detect associations. We have quantified the extent of this power loss, and produced mathematical formulae for the number of unscreened controls necessary to achieve the same power as a fixed sample of screened controls. The effect of using unscreened controls will also depend on the ratio of the number of screened controls to cases specified in the original study design, and this is also investigated. We have also investigated the cost‐benefits of the screened and unscreened approaches, according to variation in the relative costs of sampling screened and unscreened controls, together with genotyping costs. We have, thus, identified the range of situations in which using unscreened controls is a cost‐effective alternative to the screened control method and could be considered when designing a study. In many of the typical, real‐world situations in complex genetics, the use of unscreened controls is potentially cost‐effective and can, in general, be considered for disorders with population prevalence Kp < 0.2. With the steady reduction in genotyping costs and the availability of common sets of “population controls” this design is likely to become increasingly cost effective. 相似文献
962.
Insect pest species can have devastating effects on crops. Control of these insect pests is usually achieved by using chemical insecticides. However, there has been much cause for concern with their overuse. Consequently, research has been carried out into alternative forms of control, in particular biological control methods. Recent laboratory studies have indicated that these natural forms of control can induce resistant strains of insect pest. In this paper we present a discrete-time host-pathogen model to describe the interaction between a host (insect species) that can develop a resistant strain and a pathogen (biological control) that can be externally applied to the system. For this model we use a single-state variable for the host population. We show that the proportion of resistance in the population impacts on the viability of the host population. Moreover, when the host population does persist, we explore the interaction between host susceptibility and host population levels. The different scenarios which arise are explained ecologically in terms of trade-offs in intrinsic growth rates, disease susceptibility and intraspecific host competition for the resistant subclass. 相似文献
963.
The requirements, problems and progress of radioimmunotherapy in the management of certain malignancies are described. The future prospects using a two- or three-stage approach are promising. 相似文献
964.
Effects of halothane on spinal dorsal horn WDR(wide dynamic range) neuronal activity in cats 总被引:1,自引:0,他引:1
H Nagasaka S Nakamura T Genda T Miyazaki K Aikawa N Matsumoto I Matsumoto T Hori I Sato 《Masui. The Japanese journal of anesthesiology》1991,40(7):1096-1101
The effects of halothane (0.2%, 0.5%, and 1.0%) on the spinal dorsal horn wide dynamic range (WDR) neuronal activity was studied in either spinal cord intact or spinal transected cats. Extracellular activity was recorded in the dorsal horn from single WDR neurons responding to noxious and non-noxious stimuli applied to the cutaneous receptive fields on the left hind foot pads of intact or decerebrate, spinal cord transected (L 1-2) cats. When 10 micrograms of bradykinin was injected into the femoral artery ipsilateral to the recording site as the noxious test stimulus in the spinal cat, all of 7 WDR neurons gave excitatory responses which were not depressed by 0.2% and 0.5% halothane but were depressed significantly by 1.0%. On the other hand, when the injection of 10 micrograms of bradykinin into the femoral artery ipsilateral to the recording site was used in the intact cat, 7 of 14 WDR neurons (50%) gave excitatory responses, which were not depressed by 0.2% halothane but were significantly depressed by 0.5% and 1.0% halothane, and 7 of 14 WDR neurons (50%) gave inhibitory responses, which were significantly depressed by 0.2%, 0.5%, and 1.0% halothane. We have found that halothane reduces the excitation as well as the inhibition of dorsal horn WDR neuronal activity induced by bradykinin injection. 相似文献
965.
Sero- and subtypes of group B meningococci causing invasive infections in Finland in 1976-87 总被引:2,自引:0,他引:2
H K?yhty J Poolman H Abdillahi A Sivonen J Eskola E Tarkka H Peltola 《Scandinavian journal of infectious diseases》1989,21(5):527-535
Neisseria meningitidis group B (MenB) strains isolated from 1976 to 1987 in Finland in 339 patients with invasive infection were sero/subtyped by whole cell enzyme immunoassay using monoclonal antibodies to class 1 and 2/3 outer membrane proteins. 66.7% of the strains could be serotyped (class 2/3) and 70.2% subtyped (class 1). No single phenotype was clearly predominant. The most common serotypes were 4 (18.6%) and 14 (17.4%) and the most common subtypes P1.16 (20.1%) and P1.2 (12.1%). The Norwegian phenotype B:15:P1.16 was seen only rarely (a total of 18 strains). Strains from Northern Finland did not differ from those from Southern Finland: no single phenotype caused the slight increase seen in the incidence of MenB infections in the end of 1970s in the North. 相似文献
966.
The correlation between the treadmill exercise test results and the hemodynamic data of 152 patients with previous myocardial infarction were investigated. The patients were classified into 4 groups as follows: H1 left ventricular end-diastolic pressure (LVEDP) less than or equal to 12 mmHg and cardiac index (CI) greater than or equal to 3.0 L/min/m2; H2 LVEDP greater than 12 mmHg and CI greater than or equal to 3.0 L/min/m2; H3 LVEDP less than or equal to 12 mmHg and CI less than 3.0 L/min/m2; and H4 LVEDP greater than 12 mmHg and CI less than 3.0 L/min/m2. The duration of the exercise was significantly shortened for group H4 than group H1 (p less than 0.01). The maximal ST segment elevation (mSTe) was significantly increased for group H3 and group H4, versus group H1 (p less than 0.05). The number of ST segment elevations and mSTe/maximal heart rate were significantly increased for group H3 (p less than 0.05) and group H4 (p less than 0.01) versus group H1. The incidence of exercise-induced premature ventricular contractions (PVCs) was significantly increased in group H3 and group H4, versus group H1 (p less than 0.05). There were no significant differences in the maximal heart rate, double product, and ST segment depression among the 4 groups. Our data indicate that the groups with impaired left ventricular functions tend to decrease the duration of the exercise and to increase ST segment elevation and PVC frequencies during exercise. 相似文献
967.
968.
P Aggarwal S K Sharma A B Dey T K Chattopadhyay M Mathur 《Postgraduate medical journal》1989,65(770):929-931
A case of malignant fibrous histiocytoma of the mediastinum presenting with unusual features of fever and leucocytosis is reported. This is the youngest patient reported in the literature who had this tumour in the mediastinum. 相似文献
969.
S Watanabe K Nakano H Misumi M Yoshikai M Endo A Hashimoto H Koyanagi 《Nihon Geka Gakkai zasshi》1989,90(9):1513-1516
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
970.
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