全文获取类型
收费全文 | 6916篇 |
免费 | 657篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 116篇 |
儿科学 | 176篇 |
妇产科学 | 145篇 |
基础医学 | 842篇 |
口腔科学 | 290篇 |
临床医学 | 791篇 |
内科学 | 1332篇 |
皮肤病学 | 218篇 |
神经病学 | 466篇 |
特种医学 | 191篇 |
外科学 | 1204篇 |
综合类 | 230篇 |
一般理论 | 8篇 |
预防医学 | 720篇 |
眼科学 | 63篇 |
药学 | 488篇 |
中国医学 | 6篇 |
肿瘤学 | 309篇 |
出版年
2021年 | 102篇 |
2020年 | 65篇 |
2019年 | 118篇 |
2018年 | 106篇 |
2017年 | 74篇 |
2016年 | 106篇 |
2015年 | 120篇 |
2014年 | 154篇 |
2013年 | 243篇 |
2012年 | 305篇 |
2011年 | 292篇 |
2010年 | 182篇 |
2009年 | 166篇 |
2008年 | 246篇 |
2007年 | 254篇 |
2006年 | 315篇 |
2005年 | 276篇 |
2004年 | 239篇 |
2003年 | 265篇 |
2002年 | 237篇 |
2001年 | 209篇 |
2000年 | 234篇 |
1999年 | 205篇 |
1998年 | 94篇 |
1997年 | 92篇 |
1996年 | 78篇 |
1995年 | 72篇 |
1994年 | 51篇 |
1993年 | 56篇 |
1992年 | 170篇 |
1991年 | 166篇 |
1990年 | 151篇 |
1989年 | 165篇 |
1988年 | 153篇 |
1987年 | 131篇 |
1986年 | 137篇 |
1985年 | 144篇 |
1984年 | 114篇 |
1983年 | 77篇 |
1982年 | 66篇 |
1981年 | 60篇 |
1979年 | 81篇 |
1978年 | 75篇 |
1977年 | 61篇 |
1976年 | 59篇 |
1974年 | 62篇 |
1973年 | 76篇 |
1971年 | 56篇 |
1970年 | 56篇 |
1969年 | 49篇 |
排序方式: 共有7595条查询结果,搜索用时 15 毫秒
41.
Previously published data have indicated that in the rat, unlike other species examined, the kidney is not supplied by sensory nerves containing substance P (SP). As part of a study of reflex control of renal function in the rat, we have now reassessed this situation. Many fine, varicose, SP-immunoreactive nerve fibers were found in the wall of the proximal ureter and the renal pelvis, and around the larger renal blood vessels. Sparser populations of similar nerves were also seen running close to proximal and distal tubules in the renal cortex. Occasional fibers were seen at the margins of the glomeruli. Our findings suggest that sensory nerves containing SP may carry sensory information of several types from the rat kidney. 相似文献
42.
A M Albisser W S Jackman R Ferguson A Bahoric Y Goriya 《Medical progress through technology》1978,5(4):187-193
This paper provides some details of a new insulin delivery system which includes a reservoir, a pump and a power pack. The reservoir holds 50 ml and is coupled to a precision peristaltic pump whose delivery can be set to any one of 128 different mean flow rates from 0 to 80 microliter/min (+/- 1.6% over 10 months) using the flow rate controller included in the battery power pack. The system weighs 525 g consuming 60 mW at the maximum pumping rate, proportionately less at lower rates. Ten pumps have undergone bench tests for 30 days. One has been subjected to an extended life test of 11 months while seven complete systems have been used on dogs to demonstrate their capability for precise longterm intravenous insulin therapy. With this system experimental diabetes has been reversed in 4 dogs for periods now extending beyond 6 months. This device now qualifies for long-term studies on hospitalized patients with diabetes mellitus. 相似文献
43.
R J Ferguson A W Taylor P C?té J Charlebois Y Dinelle F Péronnet J De Champlain M G Bourassa 《The American journal of physiology》1982,243(5):H830-H836
Cardiovascular and skeletal muscle adaptations were studied before and after 6 mo of physical training in patients with coronary artery disease and exertional angina pectoris. Symptom-limited exercise capacity increased by 41% (470 +/- 30 to 665 +/- 35 kg.m.min-1; n = 29, P less than 0.001) with training as did skeletal muscle succinate dehydrogenase activity (1.75 +/- 0.24 to 3.31 +/- 0.24 IU; n = 23, P less than 0.001) and the areas of muscle fibers (type I from 43.6 +/- 3.3 to 54.4 +/- 3.3 micrometers 2 X 10(2); n = 21, P less than 0.05 and type II from 43.9 +/- 2.4 to 57.2 +/- 5.1 micrometers 2 X 10(2); P less than 0.01). At the same submaximal exercise intensity (mean 355 +/- 100 km.m.min-1), plasma catecholamines (1.31 +/- 0.14 to 1.07 +/- 0.09 ng.ml-1; n = 13, P less than 0.05), heart rate (115 +/- 3 to 97 +/- 3 beats/min; n = 29, P less than 0.001), and systolic blood pressure (171 +/- 4 to 143 +2- 4 mmHg; n = 29, P less than 0.001) were significantly reduced after training. Maximal coronary sinus blood flow (192 +/- 10 to 208 +/- 9 ml.min-1; n = 29, P less than 0.05) and left ventricular oxygen consumption (23.2 +/- 1.5 to 25.8 +/- 1.6 ml.min-1; n = 24, P less than 0.05) were increased by 8 and 11%, respectively, after training. The improvement in exercise capacity with training in patients with exercise is secondary to a reduction in myocardial oxygen requirements during subangina levels of exercise and partly to a small increase in maximal myocardial oxygen consumption. The skeletal muscle adaptations with training were not related to other indices of training such as the reduced exercise heart rate or increased symptom-limited exercise capacity. 相似文献
44.
J B Richardson A De Notariis C C Ferguson R C Boucher 《Laboratory investigation; a journal of technical methods and pathology》1981,44(2):144-150
The effects of a virus infection on the barrier function of tracheal epithelium were compared to the effects of a chemical agent (methacholine) which selectively increases membrane permeability, and both were compared to controls. The disruption of the airway epithelium induced by the virus infection caused an increased permeation of horseradish peroxidase (HRP) through this barrier. Methacholine enhanced HRP uptake from the airway lumen to the blood as compared to controls. Visualization of HRP in the tracheal epithelium by transmission electron microscopy correlated with the radioimmunoassay measurements in the blood. Serial anti-HRP antibody titers were measured by a competitive binding technique. The antigen permeation induced by methacholine was associated with an enhanced anti-HRP antibody production. The larger increase in antigen permeation seen with the viral infection was associated with depressed anti-HRP titers. It was concluded that viral disruption of the airway epithelial barrier may contribute to an increased uptake of orally inhaled antigens. The relationship, however, between the increased antigen penetration consequent to the viral infection and the development of allergy remains unclear. 相似文献
45.
A two-dimensional finite element model incorporating cancellous bone inhomogeneity is used to study femoral head stress alterations
caused by changes from the usual articular contact patterns. The contact stress distributions, calculated from an earlier
mathematical analysis by Greenwald and O'Connor (16), are found to influence not only the adjacent subchondral bone, but relatively
distant parts of the head as well. Both abnormally large joint incongruity and abnormally low cartilage compliance cause load
to shift away from the superior “weight-bearing” area, out toward the periphery of the contact region. As a consequence, transverse
compressive stresses, which are of appreciable magnitude but which do not contribute to weight bearing, are built up throughout
much of the superior and central portions of the femoral head. Most small changes in the overall cartilage thickness or in
its thickness distribution, when considered in isolation from hip compliance changes, have only minor effects on the internal
stress distribution. An important exception is cartilage thinning at the superior margin, which can result in abrupt longitudinal
compressive stress concentrations. It is suggested that such alterations of the normal patterns of stress transmission may
contribute to sclerosis or to the formation of osteophytes or cysts in the osteoarthritic hip.
This study was aided by grants from the Easter Seal Research Foundation (#N7739), the National Science Foundation (#ENG78-05451),
the Barra Foundation, Inc., and the Western Pennsylvania Chapter of the Arthritis Foundation. The authors wish to acknowledge
the excellent service provided by the University of Pittsburgh Computer Center. The assistance of Mr. Gary E. Graf and Mrs.
Diana W. Montgomery are also appreciated. 相似文献
46.
Both papain-solubilized and detergent-solubilized human histocompatibility antigens have been treated with NTCB (2-nitro-5-thiocyanatobenzoic acid) which cleaves these molecules at cysteine residues. A study of the fragment produced has made it possible to deduce the size and location of the two disulfide loops in these molecules. The sizes of the two loops in HLA-B7 and in the mixture HLA-B7 + 12 are about 5100 and 6600 daltons, a size similar to that of the disulfide loops found in immunoglobulins. The disulfide loops in HLA-A2 may be smaller in size. The two loops are located in middle regions of these molecules; neither the N-terminal nor the C-terminal regions contain disulfide loops. 相似文献
47.
Previously, we demonstrated that positively charged polylysine, our model for biological polyamines, activates the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin and shifts the myosin conformation from the folded 10S to linear 6S form. These effects of polylysine were reversed by the oppositely charged heparin (Szymanski et al. (1993) Am J Physiol 265, C379). In the present report, we provide further information on polylysine binding to smooth muscle myosin, and test the hypothesis that polylysine binding to unphosphorylated myosin involves filament formation. To relate the effects of polylysine on contractility in smooth muscle to physiologically relevant material, we investigated the ability of naturally occurring positively charged polyamines, histones, cadaverine, putrescine and spermidine to activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. Our data show that polylysine binding to individual unphosphorylated myosin molecules stimulates formation of myosin filaments. Polylysine also interacts with myosin filaments, causing enhancement of their size and the numbers, and this could be reversed by heparin. Polylysine binding to myosin filaments made them more resistant to disassembly by high salt concentrations (KCl) or ATP. Naturally occurring polyamines in millimolar concentrations activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. We suggest that the electrostatic interactions between naturally occurring positively charged polyamines and unphosphorylated smooth muscle myosin may play a role in stabilization of thick filament structurein situ. 相似文献
48.
High prevalence of Helicobacter pylori in saliva demonstrated by a novel PCR assay. 总被引:12,自引:1,他引:12 下载免费PDF全文
C Li P R Musich T Ha D A Ferguson Jr N R Patel D S Chi E Thomas 《Journal of clinical pathology》1995,48(7):662-666
AIMS--To investigate the prevalence of Helicobacter pylori in the saliva of patients infected with this bacterium. METHODS--A novel polymerase chain reaction (PCR) assay was developed to detect H pylori in saliva and gastric biopsy specimens from patients undergoing endoscopy. RESULTS--Our PCR assay amplified a 417 base pair fragment of DNA from all 21 DNAs derived from H pylori clinical isolates but did not amplify DNA from 23 non-H pylori strains. Sixty three frozen gastric biopsy and 56 saliva specimens were tested. H pylori specific DNA was detected by PCR in all 39 culture positive biopsy specimens and was also identified from another seven biopsy specimens which were negative by culture but positive by histology. H pylori specific DNA was identified by PCR in saliva specimens from 30 (75%) of 40 patients with H pylori infection demonstrated by culture or histological examination, or both, and in three patients without H pylori infection in the stomach. CONCLUSION--The results indicate that the oral cavity harbours H pylori and may be the source of infection and transmission. 相似文献
49.
50.
Human chorionic gonadotrophin (hCG) is a placental protein whose ectopic secretion by nontrophoblast tumors has been claimed to be of clinical relevance. Serum levels of hCG were measured in 570 patients with breast disease. A double-antibody radioimmunoassay (RIA) using antisera to hCG-beta was employed. Approximately 14% of patients with breast cancer were found to have elevated serum hCG levels. Such raised titers were not stage- or tumor-type-related, but occurred only in postmenopausal subjects. Further study showed that those patients with elevated hCG levels also had raised levels of human luteinizing hormone (hLH). Assay cross-reactivity was shown to account for the "spurious" hCG elevations. An immunocytochemical study also failed to find hCG an ectopic breast tumor constituent and/or product. It is concluded that hCG is not produced by breast tumors and has no clinical utility. 相似文献