全文获取类型
收费全文 | 8634篇 |
免费 | 652篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 205篇 |
儿科学 | 280篇 |
妇产科学 | 239篇 |
基础医学 | 1098篇 |
口腔科学 | 215篇 |
临床医学 | 855篇 |
内科学 | 1724篇 |
皮肤病学 | 54篇 |
神经病学 | 908篇 |
特种医学 | 231篇 |
外国民族医学 | 2篇 |
外科学 | 1366篇 |
综合类 | 158篇 |
一般理论 | 6篇 |
预防医学 | 802篇 |
眼科学 | 138篇 |
药学 | 523篇 |
2篇 | |
中国医学 | 8篇 |
肿瘤学 | 484篇 |
出版年
2021年 | 110篇 |
2020年 | 76篇 |
2019年 | 122篇 |
2018年 | 120篇 |
2017年 | 89篇 |
2016年 | 96篇 |
2015年 | 146篇 |
2014年 | 178篇 |
2013年 | 240篇 |
2012年 | 364篇 |
2011年 | 422篇 |
2010年 | 250篇 |
2009年 | 221篇 |
2008年 | 363篇 |
2007年 | 384篇 |
2006年 | 330篇 |
2005年 | 358篇 |
2004年 | 336篇 |
2003年 | 329篇 |
2002年 | 333篇 |
2001年 | 285篇 |
2000年 | 276篇 |
1999年 | 232篇 |
1998年 | 86篇 |
1997年 | 82篇 |
1996年 | 71篇 |
1995年 | 85篇 |
1994年 | 68篇 |
1993年 | 77篇 |
1992年 | 209篇 |
1991年 | 211篇 |
1990年 | 203篇 |
1989年 | 182篇 |
1988年 | 169篇 |
1987年 | 174篇 |
1986年 | 178篇 |
1985年 | 163篇 |
1984年 | 124篇 |
1983年 | 107篇 |
1982年 | 74篇 |
1980年 | 69篇 |
1979年 | 129篇 |
1978年 | 97篇 |
1977年 | 68篇 |
1976年 | 78篇 |
1975年 | 82篇 |
1974年 | 79篇 |
1973年 | 76篇 |
1972年 | 90篇 |
1971年 | 75篇 |
排序方式: 共有9298条查询结果,搜索用时 0 毫秒
21.
Using the concepts of stigma, NIMBY and place, this paper examines the difficulties of finding a place for needle exchange programs (NEPs). Data were drawn from semi-structured interviews with NEP staff (Ontario, Canada) that focused on operational policies and routines. An iterative, inductive analytic process was used. NEPs, their staff and clients are not always welcome additions to organizations or communities because of concerns about the ‘dangerousness’ of clients and the potential contamination of communities and workplaces by stigmatized individuals and their artefacts (e.g. contaminated injection equipment). Public parks where a lot of drug ‘action’ takes place are good destinations for outreach workers but these places are contentious sites for NEP activities, particularly when residents do not perceive a need for the program and/or want to redefine their neighbourhoods. Issues of ‘place’ are further complicated when service delivery is mobile. Finding a place within organizations is difficult for NEPs because of concerns about the diversion of limited financial and spatial resources to ‘non-core’ activities and ‘undesirable’ clients. Workers respond to these challenges by contesting the social and spatial boundaries of who is an acceptable client or neighbour and refuting the perceived ‘differentness’ of injection drug users. Implementation of an unpopular service involves a delicate balancing act of interests, understanding of the dynamics of particular communities and a willingness to reinvent and redefine programs. The sociospatial stigmatization of injection drug use has had a negative impact on NEPs, and perhaps limits HIV prevention efforts. 相似文献
22.
Radiographic manifestations of bronchiolitis obliterans with organizing pneumonia vs usual interstitial pneumonia 总被引:1,自引:0,他引:1
P W Chandler M S Shin S E Friedman J L Myers A L Katzenstein 《AJR. American journal of roentgenology》1986,147(5):899-906
The radiographic findings in 24 cases of bronchiolitis obliterans with organizing pneumonia and 16 cases of usual interstitial pneumonia were reviewed and compared. Some cases of bronchiolitis obliterans with organizing pneumonia have been mistaken for usual interstitial pneumonia, although the two diseases have distinct pathologic findings. Clinically, the diseases often have different manifestations. Bronchiolitis obliterans with organizing pneumonia has a better prognosis and often responds well to steroids. This study shows that the radiologic findings of bronchiolitis obliterans include alveolar opacities without lung-volume loss. Patients with usual interstitial pneumonia, however, have bilateral diffuse interstitial opacities with occasional honeycomb changes, and there is loss of lung volume in most patients. These findings suggest that the chest radiograph can aid in distinguishing the two diseases. 相似文献
23.
Suppression of glycosaminoglycan synthesis by articular cartilage, but not of hyaluronic acid synthesis by synovium, after exposure to radiation 总被引:1,自引:0,他引:1
We recently found that injection of 2 mCi of yttrium 90 (90Y; approximately 23,000 rads) into normal canine knees stimulated glycosaminoglycan (GAG) synthesis by femoral condylar cartilage. The present investigation was conducted to determine whether radiation affects cartilage metabolism directly. Rates of GAG synthesis and degradation in normal canine articular cartilage were studied following irradiation. Cultured synovium from the same knees was treated similarly, to determine the effects of irradiation on hyaluronic acid synthesis. Twenty-four hours after exposure to 1,000 rads, 10,000 rads, or 50,000 rads, 35S-GAG synthesis by the cartilage was 93%, 69%, and 37%, respectively, of that in control, nonirradiated cartilage. The effect was not rapidly reversible: 120 hours after exposure to 50,000 rads, GAG synthesis remained at only 28% of the control level. Autoradiography showed marked suppression of 35S uptake by chondrocytes after irradiation. Cartilage GAG degradation was also increased following irradiation: 4 hours and 8 hours after exposure to 50,000 rads, the cartilage GAG concentration was only 66% and 54%, respectively, of that at time 0, while corresponding values for control, nonirradiated cartilage were 90% and 87%. In contrast to its effects on cartilage GAG metabolism, radiation at these levels had no effect on synovial hyaluronic acid synthesis. 相似文献
24.
Jocelyn M. Cottrell BS Marjolein C. H. van der Meulen PhD Joseph M. Lane MD Elizabeth R. Myers PhD 《HSS journal》2006,2(1):12-18
The clinical goal of spinal fusion is to reduce motion and the associated pain. Therefore, measuring motion under loading
is critical. The purpose of this study was to validate four-point bending as a means to mechanically evaluate simulated fusions
in dog and rabbit spines. We hypothesized that this method would be more sensitive than manual palpation and would be able
to distinguish unilateral vs bilateral fusion. Spines from four mixed breed dogs and four New Zealand white rabbits were used
to simulate posterolateral fusion with polymethyl methacrylate as the fusion mass. We performed manual palpation and nondestructive
mechanical testing in four-point bending in four planes of motion: flexion, extension, and right and left bending. This testing
protocol was used for each specimen in three fusion modes: intact, unilateral, and bilateral fusion. Under manual palpation,
all intact spines were rated as not fused, and all unilateral and bilateral simulated fusions were rated as fused. In four-point
bending, dog spines were significantly stiffer after unilateral fusion compared with intact in all directions. Additionally,
rabbit spines were stiffer in flexion and left bending after unilateral fusion. All specimens exhibited significant differences
between intact and bilateral fusion except the rabbit in extension. For unilateral vs bilateral fusion, significant differences
were present for right bending in the dog model and for flexion in the rabbit. Unilateral fusion can provide enough stability
to constitute a fused grade by manual palpation but may not provide structural stiffness comparable to bilateral fusion. 相似文献
25.
The purpose of this document is to provide an overview of the rising occurrences of adolescent violence in the American school systems and how various theories can be used to assist in understanding this phenomenon. The authors have become increasingly interested in this topic, after direct involvement in the summer of 2001. There were a number of students who were attending summer school as a result of consistent out-of-school suspensions for violent acts. The procedure to process through the system with these students was to suspend them, resulting in the student subsequently failing their present grade. The school was located in a community known for its high rate of violence and criminal activity. Various types of adolescent violence exist in our schools. Studies have reported that violent adolescents may come from familial environments that are full of social and interpersonal conflicts (Gray & Foshee, 1999). This paper discusses the development of a research plan to investigate the number and type of adolescent violent occurrences in a southern middle school setting. 相似文献
26.
27.
The purpose of this experiment was to determine the temporal characteristics associated with the age-related development of volitional consumption of ethanol induced by the pharmacological inhibition of aldehyde dehydrogenase (AlDH). To induce preference for ethanol, the AlDH inhibitor, cyanamide, was administered to male Sprague-Dawley rats which were 30 days of age. Cyanamide (n = 8) was injected subcutaneously twice daily in a dose of 10 mg/kg over a period of 3 days while the control group (n = 6) received the saline vehicle solution according to the same schedule. Then at 50, 70, 90, and 110 days of age, both groups of rats were given a standard 11-day test of preference for water versus ethanol offered in concentrations ranging from 3% through 30%. The results showed that at 70 days of age the preference for ethanol increased above the level of the 50-day test in terms of absolute g/kg intakes and proportion of ethanol to water consumed over the lower range of 3% through 15% concentrations. During the tests at 90 and 110 days of age, the cyanamide-treated rats further increased their preference for ethanol significantly over the levels at the 70-day test in terms of both g/kg and proportional intakes. The pattern of drinking of ethanol offered in the higher concentrations of 25% and 30% was unrelated to the age of the rats and the overall intakes were significantly higher than those of the lower concentrations. These findings demonstrate that the enzymatic inhibition of AlDH systematically acts in a delayed fashion to shift the pattern of preference for ethanol which is contingent on the maturation of the animal. In this instance, the volitional intake of ethanol in the cyanamide-treated rats reached its maximal level by 90-110 days of age. It is proposed that an endocrine mechanism involved in gonadal maturation may function in the intense shift in alcohol drinking. 相似文献
28.
M L Brooks D P Mayer R T Sataloff D L Myers J R Spiegel S Ruiz 《Computerized medical imaging and graphics》1992,16(4):283-285
A patient with a surgically proven intracanalicular arachnoid cyst was studied using computed tomography, magnetic resonance imaging, and air CT cisternography. The lesion had a similar radiographic appearance to acoustic neuroma and therefore, although rare, must be considered in the differential diagnosis of intracanalicular mass lesions. We report a case in which examination was performed, in evaluating the lesion, utilizing high-resolution air CT cisternography and magnetic resonance imaging (MRI). 相似文献
29.
The impact of cancer on persons 65 years of age and older has been assessed by examining incidence rates and survival rates. For all cancers combined, the incidence rate shown in Table 4 for males 65 and older (2,468.2 per 100,000) is four times the age-adjusted rate for males 45 to 64 years of age (586.7). For elderly females, the incidence rate is twice that for females aged 45 to 64 (1,401.1 versus 609.7). Ratios of incidence rates for older versus younger males are about four to five for cancers of the stomach, colon, rectum, pancreas, and urinary bladder, and for leukemia; about three for cancers of the lung and kidney, and for non-Hodgkin's lymphomas; and 10 for cancer of the prostate. For females, the corresponding ratios are similar to those for males, although a little lower for cancers of the colon, rectum, and urinary bladder, and for leukemia, and a little higher for cancers of the stomach and pancreas. The ratios for breast, uterine cervix, uterine corpus, ovary, and lung are less than two. The relative survival rates for patients 65 and older are for many cancer sites only a few percentage points lower than rates for those 45 to 64 years of age (Table 5), suggesting that patients in this age group fare only a little worse than younger patients in escaping the effects of cancer once it has been diagnosed. Exceptions are cancer of the urinary bladder and non-Hodgkin's lymphomas for both men and women and cancers of the uterine cervix, uterine corpus, ovary, and kidney for women. For these sites, the survival rates for older patients are considerably lower than for their younger counterparts. For female breast cancer patients, there was no difference in the five-year relative survival rate for those 65 and older compared with those 45 to 64. 相似文献
30.
Transbronchial needle aspiration (TBNA) was performed as a diagnostic procedure in 91 consecutive patients ultimately proven to have bronchogenic carcinoma. Results of TBNA were compared, in the same patients, to the diagnostic yield of cytologic examination of sputum, endobronchial brushings and washings, and endobronchial/transbronchial biopsy. The diagnostic yield for sputum was 13 percent (10 of 75); brushings, 40 percent (34 of 84); washings, 29 percent (26 of 89); biopsy, 56 percent (42 of 75); and TBNA, 45 percent (41 of 91). Aspirates were positive in 35 percent of patients with adenocarcinoma, 41 percent with squamous cell carcinoma, 52 percent with large cell undifferentiated carcinoma, and 55 percent of patients with small cell carcinoma. Carinal aspirates were positive in 54 percent (6 of 11); paratracheal aspirates, 57 percent (13 of 23); parabronchial aspirates, 39 percent (11 of 28); endobronchial, 78 percent (7 of 9), and peripheral mass or solitary pulmonary nodule, 40 percent (17 of 42). The overall diagnostic yield for brushings, washings, and biopsy was 64 percent. The addition of TBNA increased the yield to 71 percent. Bronchogenic carcinoma was diagnosed solely by TBNA in six patients, all with extrabronchial or extratracheal lesions. We conclude that TBNA increases the diagnostic yield of bronchoscopy, particularly in patients with extratracheal and extrabronchial lesions. An equally important observation is that TBNA fails to contribute significantly to the diagnosis of cancer in patients with lesions readily accessible by conventional bronchoscopic techniques. Exceptions to this observation include occasional patients with necrotic endobronchial tumors, submucosal lesions, and rarely patients with peripheral lung nodules or masses. 相似文献