全文获取类型
收费全文 | 26133篇 |
免费 | 1302篇 |
国内免费 | 102篇 |
专业分类
耳鼻咽喉 | 336篇 |
儿科学 | 594篇 |
妇产科学 | 508篇 |
基础医学 | 3501篇 |
口腔科学 | 2616篇 |
临床医学 | 1943篇 |
内科学 | 5495篇 |
皮肤病学 | 613篇 |
神经病学 | 1857篇 |
特种医学 | 531篇 |
外国民族医学 | 2篇 |
外科学 | 2693篇 |
综合类 | 161篇 |
一般理论 | 3篇 |
预防医学 | 3588篇 |
眼科学 | 353篇 |
药学 | 1713篇 |
中国医学 | 258篇 |
肿瘤学 | 772篇 |
出版年
2023年 | 252篇 |
2022年 | 603篇 |
2021年 | 976篇 |
2020年 | 696篇 |
2019年 | 804篇 |
2018年 | 988篇 |
2017年 | 698篇 |
2016年 | 758篇 |
2015年 | 855篇 |
2014年 | 1166篇 |
2013年 | 1390篇 |
2012年 | 2060篇 |
2011年 | 2275篇 |
2010年 | 1112篇 |
2009年 | 836篇 |
2008年 | 1550篇 |
2007年 | 1577篇 |
2006年 | 1263篇 |
2005年 | 1145篇 |
2004年 | 993篇 |
2003年 | 867篇 |
2002年 | 760篇 |
2001年 | 489篇 |
2000年 | 471篇 |
1999年 | 370篇 |
1998年 | 133篇 |
1997年 | 94篇 |
1996年 | 64篇 |
1995年 | 91篇 |
1994年 | 74篇 |
1993年 | 58篇 |
1992年 | 170篇 |
1991年 | 156篇 |
1990年 | 174篇 |
1989年 | 143篇 |
1988年 | 127篇 |
1987年 | 86篇 |
1986年 | 102篇 |
1985年 | 75篇 |
1984年 | 53篇 |
1983年 | 57篇 |
1979年 | 66篇 |
1974年 | 46篇 |
1973年 | 51篇 |
1971年 | 41篇 |
1970年 | 74篇 |
1969年 | 85篇 |
1968年 | 60篇 |
1967年 | 61篇 |
1966年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
We investigated the effect of arachidonic acid (AA) on the release of [3H]acetylcholine ([3H]ACh) from the rat hippocampus. AA (3-30 microM) increased the basal tritium outflow and the field-electrically evoked release of [3H]ACh from hippocampal slices in a concentration-dependent manner. AA (30 microM) produced a 69+/-7% facilitation of the evoked and a 36+/-3% facilitation of basal tritium outflow. The effect of AA (30 microM) on the evoked tritium release was prevented by bovine serum albumin (BSA, 1%), which quenches AA, and was unaffected by the cyclooxygenase inhibitor, indomethacin (100 microM), and the lipooxygenase inhibitor, nordihydroguaiaretic acid (50 microM). Phospholipase A2 (PLA2, 2 U/ml), an enzyme that releases AA from the sn-2 position of phospholipids, mimicked the facilitatory effect of AA on the evoked tritium release (86+/-14% facilitation), an effect prevented by BSA (1%). The PLA2 activator, melittin (1 microM), enhanced the evoked tritium release by 98+/-11%, an effect prevented by the PLA2 inhibitor, arachidonyl trifluromethylketone (AACOCF3, 20 microM), and by BSA (1%). AA (30 microM), but not arachidic acid (30 microM), also facilitated (72+/-9%) the veratridine (10 microM)-evoked [3H]ACh release from superfused hippocampal synaptosomes, whereas PLA2 (2 U/ml) and melittin (1 microM) caused a lower facilitation (46+/-1% and 38+/-5%, respectively). The present results show that both exogenously added and endogenously produced AA increase the evoked release of [3H]ACh from rat hippocampal nerve terminals. Since muscarinic activation triggers AA production and we now observed that AA enhances ACh release, it is proposed that AA may act as a facilitatory retrograde messenger in hippocampal cholinergic muscarinic transmission as it has been proposed to act in glutamatergic transmission. 相似文献
112.
The possibility of a direct projection from the perirhinal cortex (PER) to areas CA1 and subiculum (SUB) in the hippocampus has been suggested on the basis of tracer studies, but this projection has not unequivocally been supported by physiological studies. The demonstration of such a functional pathway might be important to understand the functioning of the hippocampal memory system. Here we present physiological and further anatomical evidence for such a connection between PER and the hippocampus. Electrical stimulation of PER in vivo evoked field potentials (EFPs) at the border area of CA1/SUB, consisting of a short latency and a longer latency component. Current source density analysis revealed that the sink of the short latency component was situated in the molecular layer of area CA1/SUB, while the longer latency component had its sink in the outer molecular layer of the dentate gyrus (DG). Anterograde tracer injections in PER showed labelled fibres in the border area of CA1/SUB, but anatomical evidence for a projection of PER to DG was not found. When synaptic transmission in the entorhinal cortex was partly blocked, the amplitude of the longer latency component of the recorded EFPs in the hippocampus was decreased while the short latency component was not affected, which suggests that the indirect pathway originating in PER is mediated through a synaptic relay in the entorhinal cortex. From the present results we conclude that information originating in PER reaches area CA1/SUB by parallel, direct and indirect, routes. The existence of this parallel organization appears to form an essential feature for the proper function of the medial temporal lobe memory system. 相似文献
113.
Ferreira EL Alexsandro da Silva E Pereiro B Roque Devesa A Zungri Telo E 《Actas urologicas espa?olas》1999,23(10):895-897
While prevalence of uterine leiomyoma is high, its presentation affecting the urinary tract is uncommon. We contribute the cases of two adult women with symptoms of nephritic colic and urinary retention. Etiology was acute obstruction of the urinary tract due to previously asymptomatic urine myomas. Management in both patients was surgery, using hysterectomy to resolve the urinary obstruction. A brief review of the literature is included. 相似文献
114.
Two alkamides, deca-2E,4E-dienoic acid isobutylamide (1) and octa-2E,4E-dienoic acid isobutylamide (2), were isolated from the roots of Cissampelos glaberrima (Menispermaceae). Their structures were established by spectral and physical methods. Traces of two new alkamides, decen-2-oic acid isobutylamide (3) and decanoic acid isobutylamide (4), were identified by mass spectrometry. 相似文献
115.
The mammary gland is a hormone-target organ derived from epidermis and develops as a result of reciprocal mesenchymal-epithelial interactions. The induction of mammary differentiation from indifferent epidermal cells by mammary mesenchyme implies induction of the complement of hormone receptors characteristic of normal mammary epithelium in cells of the epidermis. Considering the facts that mammary epithelial differentiation is induced by mammary mesenchyme and that certain aspects of hormone response (androgen-induced mammary regression) are inextricably linked to mesenchymal-epithelial interactions, it is evident that the biology of the mammary gland arises from and is maintained via cell-cell interactions. As a corollary, perturbation of stromal-epithelial interactions in adulthood may play a role in mammary carcinogenesis and in turn may provide opportunities for differentiation therapy. 相似文献
116.
Prof. Dr. J. Simões da Fonseca M. Teresa Gil M. Luisa Figueira J. Guerreiro Barata Fernando Pego M. Fernanda Pacheco 《European archives of psychiatry and clinical neuroscience》1978,225(1):31-53
Summary The authors studied the behavior of normal subjects and paranoid schizophrenic patients in a simple problem-solving situation. The schizophrenics were divided into two sample groups, one of individuals under treatment and the other of individuals not under treatment.The learning process involved in this problem-solving situation is very similar to an instrumental conditioning, and can be understood by means of the following assumptions: (1) the subjects use decision functions in reacting to the stimuli, although they may be not fully aware of this; (2) learning is the result of successive transformations of these decisions in the course of time; (3) the changes have specific probabilities and are related to (a) those responses which are made to the latest stimuli, and (b) a differential probability for decision functions which were effective, or only interrupted painful reinforcement, or were completely ineffective.In schizophrenics further factors of importance were (1) an inertia factor and (2) the rigidly continued use of unsuccessful or only partially successful decision criteria.The authors used a systems theory based on Galois field theory and a calculus of operators specifying three groups of subjects. A computer program based on these hypotheses was tested in a simulation experiment.The statistical evaluation of the results showed a congruence between the theoretical approach and the experimental data.This work was carried out with financial support from the Institute de Alta Cultura, Lisbon, between 1970 and 1974 相似文献
117.
118.
Seminomas are germ cell tumors that are rarely associated with hypercalcemia. In this report, four cases of seminoma with concomitant hypercalcemia are presented and another three from the literature are reviewed. All seven patients exhibited hypercalcemia with a normal serum concentration of inorganic phosphorus and no evidence of skeletal metastases. The peripheral venous level of parathyroid hormone (PTH) was normal in four of the five patients in whom it was measured. The serum concentration of calcitriol was elevated in the two patients in whom it was measured. After systemic chemotherapy, the serum "corrected" total calcium concentration returned to normal and remained normal; the decrease in the levels temporally paralleled the decrease in tumor volume. Both patients with elevated calcitriol levels remained eucalcemic after treatment of the malignancy, suggesting that the increased serum calcitriol level was linked to the development of hypercalcemia as this humoral agent was inappropriately elevated by patients with this syndrome. In contrast to many forms of malignancy, the development of hypercalcemia did not adversely affect the prognosis of the patients with seminoma, since all seven patients entered complete remission. Hypercalcemia appears to be heretofore unrecognized paraneoplastic syndrome associated with seminoma. 相似文献
119.
D. Kabelitz M. L. da Silva Lobo K. Pechhold 《Journal of molecular medicine (Berlin, Germany)》1991,69(13):623-628
Summary The clinical success of organ transplantation depends to a large degree on the immunological acceptance of the grafted organ. This paper summarizes from an immunological point of view the recent progress that has been made to improve graft acceptance, and discusses some future aspects in the field. Over the last few years, major emphasis has been put on the development of new immunosuppressive drugs, including FK 506, rapamycin, and Deoxyspergualin. Together with monoclonal antibodies against defined T-cell surface antigens, there are now new and effective means available to prevent or treat rejection episodes. Progress has also been made in the field of HLA typing, where the introduction of molecular biology-based methods significantly increased the accuracy of HLA class II typing. The ultimate goal of transplantation immunology is the induction of (donor-) specific tolerance. While some protocols are effective in inducing peripheral tolerance in experimental animals, these regimens are at present not yet applicable in the clinical situation. To overcome the shortage of donor organs, alternative strategies are currently being considered. Among these, xenotransplantation may eventually prove successful, despite the massive immunological problems such as, e.g., the presence of preformed xenoreactive antibodies.Abbreviations CTL
cytolytic T lymphocyte
- HLA
human leukocyte antigen
- MHC
major histocompatibility complex
- PCR
polymerase chain reaction
- mAB
monoclonal antibody
- RFLP
restriction fragment length polymorphism
- TCR
T-cell receptor
Preprint of a lecture to be read at the 22nd Congress of the Gesellschaft für Nephrologie, Heidelberg, September 15–18, 1991 (Editor: Prof. Dr. E. Ritz, Heidelberg) 相似文献
120.
Rapid maxillary expansion in the primary and mixed dentitions: a cephalometric evaluation 总被引:9,自引:3,他引:6
O G da Silva Filho M C Boas L Capelozza Filho 《American journal of orthodontics and dentofacial orthopedics》1991,100(2):171-179
The present study evaluated the skeletal alterations induced by rapid maxillary expansion procedures in 30 patients in the primary and mixed dentitions. The results were obtained with the use of lateral cephalometrics before and immediately after the active phase of expansion. The time span between these two cephalometric films ranged from 14 to 21 days; therefore the "growth factor" was not considered. Based on the differences in the cephalometric measurements studied on the first and second tracings, it seems that anterior displacement of the maxilla with significant changes in the SNA angle should not be expected, although point B was repositioned more posteriorly (SNB) because of the mandibular downward and backward rotation, with subsequent increase of the inclination of the mandibular plane. The alterations in the A-P position of the mandible was reflected in the increase of ANB and NAP angles. The maxilla always dislocates downward, displaying a downward and backward rotation in the palatine plane, significantly altering the following measurements: N-ANS, PNS-PNS', A-A', SN.PP. The anchoring molars also follow the downward maxillary displacement (M-M') and, as a direct consequence of the vertical displacement of the maxilla and upper molars (N-ANS, A-A', ANS-Me, N-Me, PNS-PNS'), the facial heights increase. 相似文献