全文获取类型
收费全文 | 42626篇 |
免费 | 2553篇 |
国内免费 | 136篇 |
专业分类
耳鼻咽喉 | 661篇 |
儿科学 | 1122篇 |
妇产科学 | 763篇 |
基础医学 | 5878篇 |
口腔科学 | 2301篇 |
临床医学 | 3528篇 |
内科学 | 9001篇 |
皮肤病学 | 1350篇 |
神经病学 | 3843篇 |
特种医学 | 1271篇 |
外国民族医学 | 2篇 |
外科学 | 5776篇 |
综合类 | 271篇 |
一般理论 | 14篇 |
预防医学 | 3738篇 |
眼科学 | 707篇 |
药学 | 2911篇 |
中国医学 | 166篇 |
肿瘤学 | 2012篇 |
出版年
2023年 | 312篇 |
2022年 | 502篇 |
2021年 | 1031篇 |
2020年 | 668篇 |
2019年 | 848篇 |
2018年 | 1415篇 |
2017年 | 987篇 |
2016年 | 1138篇 |
2015年 | 1340篇 |
2014年 | 1451篇 |
2013年 | 1993篇 |
2012年 | 3174篇 |
2011年 | 3441篇 |
2010年 | 1713篇 |
2009年 | 1281篇 |
2008年 | 2511篇 |
2007年 | 2520篇 |
2006年 | 2260篇 |
2005年 | 2226篇 |
2004年 | 1949篇 |
2003年 | 1706篇 |
2002年 | 1611篇 |
2001年 | 917篇 |
2000年 | 844篇 |
1999年 | 800篇 |
1998年 | 234篇 |
1997年 | 175篇 |
1996年 | 150篇 |
1995年 | 155篇 |
1994年 | 164篇 |
1993年 | 127篇 |
1992年 | 352篇 |
1991年 | 395篇 |
1990年 | 306篇 |
1989年 | 319篇 |
1988年 | 267篇 |
1987年 | 268篇 |
1986年 | 260篇 |
1985年 | 249篇 |
1984年 | 176篇 |
1983年 | 168篇 |
1979年 | 162篇 |
1978年 | 117篇 |
1975年 | 125篇 |
1974年 | 141篇 |
1973年 | 119篇 |
1972年 | 132篇 |
1971年 | 115篇 |
1969年 | 108篇 |
1968年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
11.
12.
Human immunodeficiency virus infection in disadvantaged adolescents. Findings from the US Job Corps 总被引:3,自引:0,他引:3
OBJECTIVE--To describe the human immunodeficiency virus (HIV) epidemic among socially and educationally disadvantaged young persons in the United States. DESIGN.-We analyzed demographic and geographic findings from the screening of Job Corps students for antibody to HIV. SETTING--The Job Corps is a federal training program for disadvantaged, out-of-school youth. POPULATION SCREENED--Residential students aged 16 to 21 years who entered the Job Corps from October 1987 through February 1990. MAIN OUTCOME MEASURE--Rates of observed HIV infection in entering students, stratified by demographic and geographic features. RESULTS--Of 137,209 Job Corps students screened, 488 were HIV seropositive (3.6 per 1000), a seroprevalence rate higher than that among military applicants of the same age. Overall seroprevalence was slightly higher in male (3.7 per 1000) than in female (3.2 per 1000) Job Corps students, but among those students aged 16 and 17 years, seroprevalence was higher among females (2.3 per 1000) than among males (1.5 per 1000) (P less than .05). For students aged 16 to 21 years, seroprevalence increased with year of age: 1.8 per 1000 per year for males and 0.7 per 1000 per year for females. Among those aged 21 years, HIV prevalence was 8.9 per 1000. For black and Hispanic students from large Northeastern cities, seroprevalence increased by 4.3 per 1000 per year of age and reached 24.8 per 1000 (one of 40) in students aged 21 years. However, among students from rural areas and small towns, HIV seroprevalence was disproportionately high in the Southeast. Compared with recently described US patients with the acquired immunodeficiency syndrome, HIV-infected students who entered the Job Corps were much more likely to be female. CONCLUSIONS--These findings show that disadvantaged, out-of-school adolescents are at high risk for HIV infection. The screening results identified surprisingly high seroprevalence in the southeastern United States and demonstrated a marked shift in the HIV epidemic to young women. Controlling the HIV epidemic among teenagers must include interventions that will reach adolescents early and outside of the formal educational system. 相似文献
13.
Rosangela Saga Kamikawa Marlene Fenyo Pereira Angela Fernandes Maria Inês Meurer 《Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics》2006,101(3):374-378
OBJECTIVE: To determine the location in soft tissues of the calcifications, similar to calcified carotid atheromas, that can be observed radiographically in the cervical region in panoramic radiographs. STUDY DESIGN: In each anatomic cadaver specimen preserved in formol, consisting of the head and neck, radiopaque spheres (made from gutta-percha) were positioned in anatomic structures of the cervical region that can be sites of calcification. For each anatomic structure marked in this way, panoramic radiography was performed, consisting of 17 radiographs. The images obtained were analyzed by 24 examiners who indicated which radiographs, in their opinion, presented the radiopaque reference projected in the region of bifurcation of the carotid artery. Analysis of 2 proportions from agreement and disagreement was used to determine radiopacities that could be confused in panoramic radiographs with calcified atheromas in the carotid artery. RESULTS: The results showed that 75% (18) of the examiners correctly indicated the reference in the bifurcation of the carotid artery and 79.2% (19) indicated a triticeous cartilage as calcified atheroma of the carotid artery. CONCLUSIONS: Calcified atheromas of the carotid artery are not the only features that can produce radiopaque images lateral to the panoramic radiograph; the presence of calcification in the triticeous cartilage also can induce an erroneous diagnosis of calcified carotid atheroma. 相似文献
14.
Several psychophysiological abnormalities associated with schizophrenia have been proposed as genetic trait markers of vulnerability to the disorder. Smooth pursuit eye tracking dysfunction and abnormal long latency event-related potentials are the most promising candidates. Both are independent of the effects of psychotropic medication or mental state at the time of testing, and twin studies demonstrate that each has a high level of heritability. Having recorded smooth pursuit eye tracking and event-related potentials in 20 high-density schizophrenic families, we find abnormalities in one or both measures in most of the families studied. The abnormalities, when present, occur in the family members with schizophrenia and other forms of functional psychosis, and they have a bimodal distribution with approximately half the nonschizophrenic relatives also showing eye tracking dysfunction and/or abnormal event-related potentials. Some of these relatives had psychiatric symptoms; others were normal. Our results suggest that psychophysiological examination can help to clarify the boundaries of schizophrenia spectrum disorder. By helping to decide the phenotypic status of nonschizophrenic family members, this should increase the power of DNA linkage studies. 相似文献
15.
16.
Dual mechanisms of regulation of type I iodothyronine 5''-deiodinase in the rat kidney, liver, and thyroid gland. Implications for the treatment of hyperthyroidism with radiographic contrast agents. 下载免费PDF全文
D L St Germain 《The Journal of clinical investigation》1988,81(5):1476-1484
Alterations in thyroid hormone status and the administration of radiographic contrast agents can markedly influence iodothyronine metabolism and, in particular, the activity of type I 5'-deiodinase (5'DI). In the present studies, the mechanisms responsible for these effects have been reassessed. As previously reported, the addition of iopanoic acid (IOP) to broken cell preparations resulted in a competitive pattern of 5'DI inhibition. However, the in vivo administration to rats of IOP or 3,3',5'-triiodothyronine (rT3) resulted in a noncompetitive pattern of inhibition of 5'DI in the liver, kidney, and thyroid gland, whereby marked decreases in maximal enzyme velocity (V max) were noted, with no change in the value of the Michaelis-Menten constant. In rats rendered hyperthyroid by the injection of 3,5,3'-triiodothyronine (T3), 5'DI activity was significantly increased in the liver and the kidney. The administration of IOP to these thyrotoxic animals resulted in a rapid loss of enzyme activity characterized by an approximate 80% decrease in 5'DI V max values in both tissues. Furthermore, this inhibitory effect persisted for longer than 60 h after a single IOP injection. IOP administration also decreased 5'DI V max levels in the thyroid gland by 52%. In other experiments, treatment of intact Reuber FAO hepatoma cells with IOP or rT3 induced a rapid decrease in 5'DI V max levels. In cells treated with cycloheximide, these agents enhanced the rate of disappearance of enzyme activity by greater than 12-fold, indicating a predominant effect on accelerating the rate of enzyme inactivation and/or degradation. These studies demonstrate that iodothyronines and other iodinated compounds have complex regulatory effects on 5'DI that entail alterations in the rates of both enzyme activation and inactivation. The previously accepted concept that rT3 and IOP impair thyroxine (T4) to T3 conversion in vivo by acting as competitive inhibitors is an oversimplification. Rather, the clinically beneficial effects of administering these agents to patients with hyperthyroidism may result primarily from the rapid and prolonged inactivation of 5'DI which occurs in the thyroid gland and peripheral tissues. 相似文献
17.
Almir Moojen Nácul Andrea Prestes Nácul Antônio Greca de Born 《Aesthetic plastic surgery》1998,22(6):444-450
This research presents reports of cases where a biocompatible and alloplastic biomaterial—Bioplastique—was used, associated
with conventional plastic surgery or as a complement to it, with the aim of achieving a better final aesthetic result. Four
cases are presented where Bioplastique was used in association with rhytidoplasty, rhinoplasty, and other surgical techniques.
This material has shown itself to be appropriate to complement surgery; achieving a final result which would not be possible
without any resort to a complement or any other hard procedure by the surgeon and is not more traumatic for the patient. 相似文献
18.
H. Schooltink St. Rose-John 《Bundesgesundheitsblatt, Gesundheitsforschung, Gesundheitsschutz》2003,46(3):188-196
Cytokines are extracellular mediators which co-ordinate the immune system and which are essential for several differentiation processes e.g.hematopoiesis.Cytokines bind to specific receptors on the surface of target cells thereby initiating an intracellular signalling cascade leading to cytokine- and cell-specific reactions.The cytokine network is characterised by diverse regulation mechanisms and by the close interaction of different cytokine systems.Interaction and regulation takes place at the level of cytokines, its receptors and at the level of intracellular signal transduction molecules.The resulting network allows the co-ordinated response of different cell types and tissues to environmental changes.A detailed knowledge of this “language of the immunsystem” may reveal many new therapeutical strategies for the treatment of inflammation, autoimmune disease or neoplasia. 相似文献
19.
20.
Decreased blood perfusion in canine tibial diaphysis after filling with acrylic bone cement compared with inert bone wax 总被引:1,自引:0,他引:1
Sixteen dogs had one tibia filled with acrylic PMMA bone cement and the opposite, control tibia filled with inert bone wax. After 1, 4, and 12 weeks, the blood perfusion in diaphyses was measured with Sc-46 labeled microspheres. The blood flow rates increased from 1 to 4 weeks and dropped to about the 1-week level after 12 weeks on both sides, with the acrylic side lower than the control side. On both sides, Disulphine Blue staining of the bones showed severe endosteal avascularity after 1 and 4 weeks and massive periosteal apposition after 4 and 12 weeks. The initial increase in blood flow is considered due to periosteal apposition, and the differences in blood flow rates are attributed to avascularity caused by the polymerization heat and toxicity of the acrylic cement. 相似文献