全文获取类型
收费全文 | 7419篇 |
免费 | 399篇 |
国内免费 | 41篇 |
专业分类
耳鼻咽喉 | 58篇 |
儿科学 | 124篇 |
妇产科学 | 131篇 |
基础医学 | 1437篇 |
口腔科学 | 127篇 |
临床医学 | 544篇 |
内科学 | 1360篇 |
皮肤病学 | 167篇 |
神经病学 | 687篇 |
特种医学 | 359篇 |
外科学 | 895篇 |
综合类 | 24篇 |
一般理论 | 1篇 |
预防医学 | 524篇 |
眼科学 | 136篇 |
药学 | 901篇 |
中国医学 | 38篇 |
肿瘤学 | 346篇 |
出版年
2023年 | 81篇 |
2022年 | 133篇 |
2021年 | 251篇 |
2020年 | 190篇 |
2019年 | 229篇 |
2018年 | 366篇 |
2017年 | 252篇 |
2016年 | 269篇 |
2015年 | 301篇 |
2014年 | 393篇 |
2013年 | 529篇 |
2012年 | 742篇 |
2011年 | 782篇 |
2010年 | 433篇 |
2009年 | 242篇 |
2008年 | 276篇 |
2007年 | 269篇 |
2006年 | 260篇 |
2005年 | 173篇 |
2004年 | 160篇 |
2003年 | 127篇 |
2002年 | 110篇 |
2001年 | 82篇 |
2000年 | 72篇 |
1999年 | 58篇 |
1998年 | 57篇 |
1997年 | 61篇 |
1996年 | 43篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 22篇 |
1992年 | 33篇 |
1991年 | 30篇 |
1990年 | 32篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 30篇 |
1984年 | 33篇 |
1983年 | 21篇 |
1982年 | 33篇 |
1981年 | 21篇 |
1979年 | 23篇 |
1977年 | 26篇 |
1976年 | 24篇 |
1975年 | 27篇 |
1974年 | 22篇 |
1973年 | 24篇 |
1970年 | 21篇 |
排序方式: 共有7859条查询结果,搜索用时 0 毫秒
41.
New types of hydrophilic gels based on N-(2-hydroxypropyl)methacrylamide which contain oligopeptide sequences in the crosslinks were prepared. These gels are enzymatically degradable by chymotrypsin. The rate of their degradation may be varied within a broad range by changes in the length and detailestructure of the oligopeptide sequence in the crosslinks and by changing their network density. 相似文献
42.
Magdy S. Aly Paola Dal Cin Herman Van Den Berghe Wim Van De Voorde Hein Van Poppel Filip Ameye Luc Baert 《Genes, chromosomes & cancer》1994,9(4):227-233
We combined conventional cytogenetic analysis and fluorescence in situ hybridization of short-term cultures of 28 samples from benign prostatic hyperplasia. Lou of the Y chromosome was the most common chromosome change, followed by trisomy 7. Trisomy 7, however, may be unrelated to the origin of benign prostate hyperplasia, in which the only and not very specific change seems to be the loss of the Y chromosome. Genes Chrom Cancer 9:227-233 (1594). © 1994 Wiley-Liss, Inc. 相似文献
43.
Stem cells exhibit unique properties and hold high therapeutic promise, but factors influencing their differentiation after transplantation need to be recognized and defined for this promise to be fully met. Here, we demonstrate that endogenous colony-forming unit spleen (CFU-S) colonies are not generated in lethally irradiated mice transplanted with neural stem cells obtained from brain tissue of syngeneic donors. We investigated the proportion of transplanted neural stem cells that contributed to hematopoietic reconstitution and compared the distribution of transplanted cells in nonsplenectomized to that of splenectomized mice following sublethal whole-body irradiation. We also used clonogenic assays, colony assays, and histochemical analyses to explore conditions under which transplanted, beta-galactosidase-tagged neural stem cells underwent hematopoietic differentiation. Our results suggest that neural stem cells do undergo extramedullary hematopoiesis, even while no endogenous hematopoietic colonies develop in the spleen. Furthermore, we found that neural stem cells effectively colonized the bone marrow of splectomized recipients. We conclude that the hematopoietic differentiation of neural stem cells is highly dependent on the extramedullary environment. We also conclude that the bone marrow does not provide an environment supportive of hematopoietic differentiation by neural stem cells. 相似文献
44.
Antibody content against rabbit red blood cells (anti-RaRBC) in murine sera of different strains (Swiss, CBA, C57BL/6, AKR, BALB/c) and activity of complement alternative pathway (AP) were investigated. In contrast to the CBA and C57BL/6, random-bred Swiss strain and inbred BALB/c and AKR strains are good producers of these natural antibodies. There is no correlation between AP activity and anti-RaRBC content. Isolated human anti-RaRBC antibodies, IgM and IgG classes, lead to the enhancement of APhu and APmo activity, contrary to the murine anti-RaRBC which belong solely to IgM class, and do not express this capability. 相似文献
45.
Swirski FK Gajewska BU Robbins CS D'Sa A Johnson JR Pouladi MA Inman MD Stämpfli MR 《European journal of immunology》2004,34(9):2375-2386
We previously showed that granulocyte-macrophage colony-stimulating factor (GM-CSF) breaks tolerance induction. The objective of this study was to determine whether GM-CSF breaks established inhalation tolerance. To induce tolerance, BALB/c mice were exposed to aerosolized ovalbumin (OVA) for 10 consecutive days. A control group was exposed to saline. Subsequently, tolerant and control animals were exposed to OVA in a GM-CSF-enriched airway microenvironment. Tolerant animals, unlike control animals, did not develop airway and peripheral blood eosinophilia, had diminished levels of OVA-specific IgE, and reduced airway hyper-responsiveness. While tolerant animals did not express IL-4, IL-5 and IL-13, levels of the regulatory cytokines IL-10, IFN-gamma and transfoming growth factor (TGF)-beta were similar between tolerant and non-tolerant animals. Lung CD4+ T cells were activated according to CD69, CD25 and T1/ST2 expression, but systemic responses characterized by splenocyte proliferation and Th2 effector function were dramatically reduced. Concurrent expression of GM-CSF and decorin, a natural inhibitor of TGF-beta, reversed eosinophilic unresponsiveness. Our study suggests that the breakdown of tolerance and, by extension, the emergence of eosinophilic inflammation, requires two signals: one that triggers sensitization and one that interferes with negative regulation. Moreover, our study shows that dysregulated expression of an extracellular matrix protein may break established tolerance and lead to eosinophilic airway inflammation. 相似文献
46.
Hník P. Holas M. Krekule I. Kříž N. Mejsnar J. Smieško V. Ujec E. Vyskočil F. 《Pflügers Archiv : European journal of physiology》1976,362(1):85-94
Using liquid ion-exchanger semimicroelectrodes with a side pore, we measured changes of extracellular potassium concentration (Ke
+) in adult rabbit and cat gastrocnemius muscles and in venous effluent blood flowing from the cat gastrocnemius muscle during various bouts of activity induced by sciatic nerve stimulation.
相似文献
1. | Isometric tetanic contractions (at 50 Hz) of various durations caused transient accumulation of Ke + which was non-linearly related to the duration of muscle activity. The peak values of Ke + in response to muscle stimulation were analogous in rabbits and cats, attaining values, e.g. after a 20-s isometric tetanus, between 8–9 mEq/lK+ in both species. |
2. | Potassium concentration in venous effluent blood (K ven + ) was transiently increased after isometric tetani. Since blood flow was measured at the same time, it was possible to calculate the amount of K+ lost by the muscle after tetani of various durations. A 32 g gastrocnemius muscle of the cat, for example, loses 9.36±1.52 EqK+ after a 20-s isometric tetanus, which corresponds roughly to 0.5% of the total muscle potassium content. The loss of K+ in this muscle was 29.3 pEq K+/impulse/100 g fresh muscle tissue. |
3. | There was no evident difference between the amount of K+ released during isometric tetani, or tetanic contractions performed under isotonic conditions. Single twitches evoked by indirect stimulation at 1 Hz for several minutes also induced a small rise in K ven + . |
4. | If the loss of K+ from the muscle into the blood stream is transiently prevented by arterio-venous occlusion installed immediately before a 10-s isometric tetanus, most K+ is released subsequently when blood flow is renewed, if the occlusion lasts for 20–25 s. It is not until blood flow is occluded for 40–60 s that most K+ is apparently resorbed and only a minor portion is released and is to be found in the venous blood. |
5. | The transient accumulation of muscle extracellular potassium may locally affect nerve endings, skeletal and smooth muscle cells. |
47.
Yu. B. Lishmanov B. Yu. Kondrat’ev L. N. Maslov N. V. Naryzhnaya 《Bulletin of experimental biology and medicine》1997,123(2):130-132
Acute cold exposure (−20°C, 4 h) induces a transient decrease in the ventricular fibrillation threshold without morphological
and radionuclide signs of irreversible damage to cardiomyocytes. The agonist of μ-receptors DAGO, which reduces adrenoreactivity
of the myocardium, prevents the decrease in the ventricular fibrillation threshold induced by acute cold exposure.
Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 123, No. 2, pp. 154–157, February, 1997 相似文献
48.
Der p-Phenylendiamin(PPD)-Oxydasetest als eine Laboratoriumsmethode zur Diagnostik der Hyperthyreose
Zusammenfassung Bei 31 unbehandelten Hyperthyreosekranken wurde die p-Phenylendiamin(PPD)-Oxydaseaktivität und die Kupferkonzentration im Serum und gleichzeitig der Grundumsatz bestimmt. Der Grundumsatz lag bei allen Patienten über der Normgrenze. Die PPD-Oxydaseaktivität und der Serumkupferspiegel sind signifikant erhöht gefunden worden. Demzufolge scheint die PPD-Oxydasebestimmung im Serum ein guter Hinweis für die Diagnose unbehandelter Hyperthyreosen zu sein.Weiterhin wurden dieselben Untersuchungen bei Hyperthyreosekranken vor und während der Therapie mit einzelnen Thyreostatica der Thiouracilgruppe durchgeführt. Dabei konnte eine Verminderung von PPD-Oxydaseaktivität und Kupfergehalt im Serum, parallel zur Grundumsatzverminderung, beobachtet werden, sofern die Thyreostatica in genügenden Dosen angewandt wurden. Die Bestimmung der PPD-Oxydaseaktivität erscheint daher auch zur Beurteilung des Therapieeffekts und zur Ermittlung der therapeutischen Dosis von Wert zu sein. 相似文献
49.
The UL41 gene of the HSZP strain of herpes simplex virus type 1 (HSV-1) defective with respect to the early shutoff of host
protein synthesis was sequenced and compared with the corresponding HSV-1 strain KOS and 17 gene sequences. In comparison
with strain 17, nine mutations (base changes) were HSZP specific, five KOS specific and four were common for both strains.
Nine mutations caused codon changes. Three of these mapped to the nonconserved regions and the others to the conserved regions
of the functional map of UL4l gene. One KOS specific mutation mapped to the region responsible for the binding of the virion
host shutoff (vhs) protein to the alpha-transinducing factor (VP16). The possible relationship between mutations and host
shutoff function is discussed. The nucleotide sequence data of the UL41 gene of HSZP and KOS have been submitted to the Genbank
nucleotide database and have been assigned the accesion numbers Z72337 and Z72338.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
50.
The predominant cells of female prostatic glands lining their lumen were found to be tall cylindrical secretory cells with short stubby microvilli, protuberances of the apical cytoplasm, and with bleb formation. Abundant secretory vacuoles and granules, rough endoplasmic reticulum, developed Golgi complexes and numerous mitochondria are characteristic of their active secretory configuration with apocrine (apical blebs) and merocrine (secretory vacuoles and granules) type of secretion. Basal (reserve) cells were seen to be located between the secretory (luminal) cells and the basement membrane. Their ground cytoplasm is dense with rough endoplasmic reticulum and mitochondria. Their nuclei, unlike those of secretory cells, possess more peripheral condensed chromatin, denser dispersed chromatin and sporadic nucleoli. Besides the two basic types of mature prostatic cells intermediary cells were also seen, located between the basal and secretory cells or in their close vicinity. Their cytoplasm exhibits numerous profiles of rough endoplasmic reticulum and free ribosomes. Secretory vacuoles and granules were mostly practically absent (type 1 intermediary cells) so that they resembled basal (reserve) cells. In some of them, however, as in secretory cells, such secretory elements do gradually appear (type 2 intermediary cells). The finding of intermediary cells in the lining of prostatic glands supports the role of basal (reserve) cells in the renewal of cells in glands of the female prostate. The first ultrastructural analysis of the normal female prostate performed by transmission electron microscopy showed that, as in the postpubertal male, the prostatic glands in the adult female display mature secretory and basal cells. The results of the presented study further corroborate the contemporary concept of the female prostate as a functional genitourinary organ. 相似文献