全文获取类型
收费全文 | 1511879篇 |
免费 | 111165篇 |
国内免费 | 2359篇 |
专业分类
耳鼻咽喉 | 21956篇 |
儿科学 | 52340篇 |
妇产科学 | 43329篇 |
基础医学 | 217510篇 |
口腔科学 | 39845篇 |
临床医学 | 130679篇 |
内科学 | 300723篇 |
皮肤病学 | 32982篇 |
神经病学 | 116840篇 |
特种医学 | 60173篇 |
外国民族医学 | 693篇 |
外科学 | 232963篇 |
综合类 | 33181篇 |
现状与发展 | 2篇 |
一般理论 | 515篇 |
预防医学 | 111893篇 |
眼科学 | 33854篇 |
药学 | 111455篇 |
2篇 | |
中国医学 | 3061篇 |
肿瘤学 | 81407篇 |
出版年
2018年 | 15961篇 |
2017年 | 12027篇 |
2016年 | 13306篇 |
2015年 | 15136篇 |
2014年 | 20763篇 |
2013年 | 31970篇 |
2012年 | 43127篇 |
2011年 | 45539篇 |
2010年 | 27705篇 |
2009年 | 26207篇 |
2008年 | 43506篇 |
2007年 | 46746篇 |
2006年 | 46886篇 |
2005年 | 45534篇 |
2004年 | 44420篇 |
2003年 | 42935篇 |
2002年 | 41872篇 |
2001年 | 73728篇 |
2000年 | 76470篇 |
1999年 | 64848篇 |
1998年 | 17458篇 |
1997年 | 15909篇 |
1996年 | 16176篇 |
1995年 | 15393篇 |
1994年 | 14510篇 |
1993年 | 13474篇 |
1992年 | 50745篇 |
1991年 | 49862篇 |
1990年 | 48426篇 |
1989年 | 46254篇 |
1988年 | 42478篇 |
1987年 | 41614篇 |
1986年 | 38829篇 |
1985年 | 37313篇 |
1984年 | 27846篇 |
1983年 | 23490篇 |
1982年 | 13659篇 |
1981年 | 12330篇 |
1979年 | 24893篇 |
1978年 | 17408篇 |
1977年 | 14722篇 |
1976年 | 13711篇 |
1975年 | 14941篇 |
1974年 | 17436篇 |
1973年 | 16893篇 |
1972年 | 15547篇 |
1971年 | 14184篇 |
1970年 | 13433篇 |
1969年 | 12223篇 |
1968年 | 11241篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
Previous pharmacological studies with the pituitary gland have suggested that acetylcholine (ACh) might be involved in the regulation of intermediate lobe (IL) function. Whether ACh is endogenous to the IL cells or provided from an extrinsic source is unclear. The present experiments tested the possibility that the endocrine cells of the IL may be a source of ACh by measuring certain cholinergic markers in a primary culture of dissociated porcine cells. The endogenous ACh content was readily measurable in both the freshly dissociated IL cells and in 2- or 4-day primary cultures. Choline acetyltransferase activity was also measurable in the freshly dissociated and cultured IL cells and was reduced by 53% in the presence of a specific inhibitor, napthylvinylpyridine (50 μM). IL cells incubated in the presence of [14C]choline (1 μM) were able to synthesize [14C]ACh and the accumulation of the new ACh was inhibited by hemicholinium-3 (30 μM), a competitive inhibitor of high affinity choline uptake at cholinergic nerve terminals. In conclusion, these results demonstrate that the endocrine cells of the IL are capable of synthesizing and storing ACh. 相似文献
992.
Common migraine and cervicogenic headache have many traits in common, so many that they may be mixed up. Both are unilateral headaches with a female preponderance. However, as for a number of variables, they differ. This first and foremost has to do with factors concerning the neck. In cervicogenic headache, the following symptoms and signs are present: a reduced range of motion in the neck; mechanical precipitation of attack, either by neck movements or by external pressure over the greater occipital nerve of the C2 root; ipsilateral shoulder/arm pain; unilaterality without side-shift. Similar findings are usually not made in common migraine. Typical migraine symptoms, such as nausea, vomiting, photophobia, and phonophobia also occur in cervicogenic headache, but less frequently and to a lesser degree. Operative procedures directed to occipital/nuchal structures may afford decisive differentiation between the two disorders. In our estimation, cervicogenic headache and common migraine are two distinct disorders, with their own clinical patterns, pathogenesis, treatment - and, in all probability, also prognosis. 相似文献
993.
995.
T P Werblin 《Refractive & corneal surgery》1989,5(3):167-176
In summary, the greatest challenge for lamellar refractive surgery is in the treatment of myopia. There are and always will be patients who are satisfied with a partial correction of myopia. Many of these patients can be served quite adequately by currently available refractive techniques, but a technique in which level of accuracy is adequate for the treatment of myopia in general is not yet available. Lamellar refractive surgery--where have we been and where are we going? We have seen the evolution of the epikeratoplasty procedure for almost a decade and continue to see procedural changes which may increase the accuracy and stability of the procedure, such as alternative modalities for tissue preservation and alternative methods for surgical attachment. It remains potentially useful in several areas of refractive surgery, but its inaccuracy in the treatment of myopia remains a significant problem. Will the epithelial healing problems and postoperative care be too cumbersome for the general ophthalmologist? Will the excimer laser fill the needs of myopic refractive surgery? Personally, I do not feel that any biological lens, be it a cornea which has had incisions as with radial keratotomy, or a cornea which is remolded in one way or another as with the excimer laser, will produce predictable refractive results to the extent that is required to satisfy the general needs of the myopic population. Hydrogel keratophakia is in its infancy, but it holds the potential of being a far more accurate procedure because of the ability to interchange lenses to further refine the refractive result. Refractive surgery will in the next decade achieve a level of sophistication far greater than what we have seen to date. Lans could not have dreamed of the remarkable evolution in refractive surgical innovation in the past century. It is hoped that we will not have to wait that long to create a readily available solution to the problem of refractive surgery for myopia. 相似文献
996.
In 1986 and 1987, four patients with tibial malunion involving both angular and torsional misalignment underwent surgical correction by a single-cut technique based on a mathematical model of long bone deformity. The technique involved a single surgical cut, followed by rotation of the two fragments along the osteotomy plane. The orientation of the osteotomy is based on a computer-assisted design. The deformity is measured on radiographs, computed tomography, and clinical exam and is then plotted on graphs to find the osteotomy orientation. The deformity involved varus and extension in four cases, internal rotation in 2, and external rotation in two. The deformities ranged from 9 to 26 degrees. The cutting angle of the osteotomy ranged from 50 to 66 degrees as measured from the transverse plane. Actual lengthening of 1 cm and functional lengthening over 1.5 cm was obtained without the use of bone graft. As no wedge of bone was removed, all corrected bones were easily suited to rigid internal fixation across the cut surface. In all cases, the desired correction was obtained within measurable error, and union was obtained with minimal immobilization. There were no soft tissue or joint contractures, and no neurovascular complications. In one patient, who had had four prior surgical procedures on the involved limb, an infection developed 6 weeks postoperatively that required debridement and delayed primary closure. As the technique involves only one cut, no wedge of bone is removed, no shortening occurs, and the osteotomy is highly suitable for rigid internal fixation. The described technique is the first to integrate in a precise way the correction of torsion with the correction of angular deformity.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
997.
Angiolymphoid hyperplasia with eosinophilia of the orbit associated with obstructive airway disease 总被引:2,自引:0,他引:2
Two patients with angiolymphoid hyperplasia with eosinophilia isolated to the orbit had eyelid swelling, a superior orbital mass, and histories of intermittent obstructive airway disease. One patient later developed a transient peripheral blood eosinophilia as high as 36%. One lesion recurred 38 months postoperatively and responded to systemic corticosteroid therapy. 相似文献
998.
Repeated administration of the antimanic drug lithium (4 mEq/kg/day for 2, 4 or 6 days, i.p.) to rats produced a progressive decline and eventual depletion of dynorphin-A (1-8) (DYN) concentration whereas Met5-enkephalin (ENK) was only marginally decreased in the neurointermediate lobe of the pituitary (NIL). Administration of a neuroleptic haloperidol neither affected ENK and DYN levels nor influenced lithium-induced changes. The study reveals that lithium produces a preferential perturbation in the dynorphin system relative to the enkephalin system. These results taken together with other evidence, indicate that dynorphin is possibly coreleased with vasopressin following lithium administration and provide a pharmacological support to the previously described colocalization and corelease of these endogenous peptides in the NIL. 相似文献
999.
L L Polla S L Jacques R J Margolis M R Prince R R Anderson J A Parrish O T Tan 《Annales de dermatologie et de vénéréologie》1987,114(4):497-505
Since 1962, lasers have been used in dermatology and have become the first choice in the treatment of superficial, vascular ectasia. Lasers are unique sources of light; they are coherent, monochromatic, collimated and intense. By careful selection of wavelength, pulse duration, and intensity, it is often possible to selectively confine a laser effect to a specific histologic structure in tissue, depending upon the tissue properties. The ideal treatment of Port Wine Stains (PWS) should irreversibly damage the ectatic vessels but minimize heating of the epidermis and superficial dermis. A theory, called selective photothermolysis, predicts the optimal combination of laser parameters of achieving this ideal treatment of PWS to be a wavelength of 577 nm, a pulse duration of 0.35-10 msec, and an energy per surface area of about 7-8 J/cm2. Laser wavelength: The wavelength of 577 nm is preferred because it: maximizes the selective absorption by hemoglobin, minimizes absorption by epidermal melanin, provides sufficient depth of penetration in the blood to coagulate 0.1 mm vessels allows penetration of light into dermis up to 1 mm. Laser pulse duration: A pulse-width in the range of 0.35-10 msec allows the temperature elevation to be uniform inside the vessel and to be confined to the vessel area. Shorter pulses superheat the red blood cells causing explosive boiling and hemorrhage. Longer pulses allow heat to diffuse away from vessels, requiring greater energies per pulse to achieve vessel damage. An increased energy per pulse increases the risk of excessive damage to surrounding tissue.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
1000.
J P Murphy A V Adyanthaya P R Adams J D McArthur W E Walker 《The Annals of thoracic surgery》1987,43(3):323-325
Pulmonary artery aneurysms are rare lesions for which operative management is not frequently undertaken. When operation is indicated, central lesions involving the pulmonary trunk, right main pulmonary artery, or left main pulmonary artery are repaired using cardiopulmonary bypass. Peripheral aneurysms in segmental intrapulmonary arteries have been managed most frequently by lobectomy, but occasionally by aneurysmectomy and pulmonary arterial repair. We used cardiopulmonary bypass for peripheral pulmonary aneurysmectomy in a patient with limited respiratory reserve because he had undergone prior contralateral bilobectomy; this allowed controlled resection while preserving a maximal amount of pulmonary parenchyma. 相似文献