全文获取类型
收费全文 | 4789篇 |
免费 | 299篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 76篇 |
儿科学 | 118篇 |
妇产科学 | 109篇 |
基础医学 | 974篇 |
口腔科学 | 120篇 |
临床医学 | 389篇 |
内科学 | 735篇 |
皮肤病学 | 101篇 |
神经病学 | 483篇 |
特种医学 | 155篇 |
外科学 | 513篇 |
综合类 | 19篇 |
预防医学 | 399篇 |
眼科学 | 97篇 |
药学 | 576篇 |
中国医学 | 31篇 |
肿瘤学 | 208篇 |
出版年
2023年 | 47篇 |
2022年 | 53篇 |
2021年 | 97篇 |
2020年 | 70篇 |
2019年 | 135篇 |
2018年 | 239篇 |
2017年 | 199篇 |
2016年 | 233篇 |
2015年 | 198篇 |
2014年 | 250篇 |
2013年 | 460篇 |
2012年 | 551篇 |
2011年 | 589篇 |
2010年 | 351篇 |
2009年 | 155篇 |
2008年 | 107篇 |
2007年 | 102篇 |
2006年 | 82篇 |
2005年 | 49篇 |
2004年 | 28篇 |
2003年 | 29篇 |
2002年 | 20篇 |
2001年 | 43篇 |
2000年 | 46篇 |
1999年 | 48篇 |
1998年 | 31篇 |
1997年 | 33篇 |
1996年 | 30篇 |
1995年 | 35篇 |
1994年 | 30篇 |
1993年 | 19篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 26篇 |
1989年 | 21篇 |
1988年 | 29篇 |
1987年 | 17篇 |
1985年 | 22篇 |
1984年 | 33篇 |
1983年 | 28篇 |
1982年 | 33篇 |
1981年 | 28篇 |
1980年 | 24篇 |
1979年 | 25篇 |
1978年 | 25篇 |
1977年 | 18篇 |
1976年 | 24篇 |
1975年 | 21篇 |
1973年 | 16篇 |
1971年 | 17篇 |
排序方式: 共有5103条查询结果,搜索用时 11 毫秒
31.
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. |
32.
The event-related responses of 18 individuals were recorded while they were listening to 3 music clips of 6 s duration which were repeated 30 times each. The music clips differed in the level of their complex structure, induced mood, musical tempo and prominent frequency. They were taken from Mozart's sonata (K. 448), and Brahms' Hungarian dance (no. 5). The third clip was a simplified version of the theme taken from Haydn's symphony (no. 94) played by a computer synthesizer. Significant differences in induced event-related desynchronization between the 3 music clips were only observed in the lower-1 alpha band which is related to attentional processes. A similar pattern was observed for the coherence measures. While respondents listened to the Mozart clip, coherence in the lower alpha bands increased more, whereas in the gamma band a less pronounced increase was observed as compared with the Brahms and Haydn clips. The clustering of the three clips based on EEG measures distinguished between the Mozart clip on the one hand, and the Haydn and Brahms clips on the other, even though the Haydn and Brahms clips were at the opposite extremes with regard to the mood they induced in listeners, musical tempo, and complexity of structure. This would suggest that Mozart's music--with no regard to the level of induced mood, musical tempo and complexity--influences the level of arousal. It seems that modulations in the frequency domain of Mozart's sonata have the greatest influence on the reported neurophysiological activity. 相似文献
33.
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
34.
Dr. L. Kutinová Š. Němečková E. Hamšíková M. Press H. Závadová I. Hirsch V. Němeček V. Krchňák J. Smrt D. Slonim V. Vonka 《Archives of virology》1990,112(3-4):181-193
Summary Several vaccinia virus recombinants inducing the synthesis of the middle surface (M) protein of hepatitis B virus (HBV) were constructed. One of them, denoted vl37, was examined in some detail. The virus replicated nearly to the same extent in various cell lines, viz. human embryo diploid fibroblast LEP and MRC-5 cells, rabbit embryo fibroblast REF cells, TK– rat RAT-2 cells, and green monkey CV-1 cells. However, the production of M protein was found considerably lower in the human LEP and MRC-5 than in the other cells examined. In addition, the kinetics of M formation were different in these two cell systems, LEP cells lagging significantly behind CV-1 cells. The low-level production of M protein in LEP cells was not increased by repeated vl37 passages in LEP cells, nor by a passage in a laboratory worker accidentally infected with the vl37 virus, nor by shortening the leader sequence preceding the translation initiation codon. The greater part of the M antigen was found to be cell associated, more so in the cells of human than monkey origin. From the major HBV S antigen (HBsAg) isolated from the plasma of chronically infected subjects, the antigen released by cell destruction differed by binding to polymerized human albumin. This property was utilized in ELISA to detect anti-preS2 antibody. Rabbits inoculated intradermally with the vl37 virus developed antibodies reactive in this assay as well as with a synthetic peptide corresponding in the amino acids 14–34 of the NH2terminus of the HBsAg preS2 region. 相似文献
35.
Adult male and female Wistar rats maintained on ad lib diet were given a choice between tap water and a solution of glucose in the concentration of either 5 or 12%. Both sexes exhibited a marked preference for glucose solutions. With the 5% solution the volume intake was similar in both sexes and the total calorie intake was normal. With the 12% solution the volume intake was higher in females than in males, while in both sexes the total calorie intake was increased to a similar (maximum acceptable) level. Treatment with Protamine Zinc Insulin (PZI) in a daily dose of 40 U/kg b.w. markedly increased the intake of the 5% solution in both sexes, but significantly more in females than in males, thus revealing sex differences which were not manifest in untreated rats. PZI treatment had little effect on 12% glucose solution intake, presumably because with this solution the total calorie intake was increased to a maximum already in untreated rats. 相似文献
36.
M. Cikrt J. Hurych D. Kuklová J. Havrdová P. Lepší J. Kopecký B. Milek A. Nauš 《International archives of occupational and environmental health》1985,55(3):241-246
Summary In a 61-year-old woman, who had been exposed for 20 years to cadmium in the production of Ni-Cd batteries, nephrectomy of the contracted kidney was performed. The removed kidney was examined histologically and the cadmium concentration was determined in the cortex (44.97 g g–1) and in the medulla (7.71 g g–1). The homogenates of the renal cortex and medulla were subjected to gel filtration on Sephadex G-75. In the cortex, as well as the medulla, cadmium was predominantly found in the low-molecular (metallothionein) fraction, but in the cortex, Cd content in this fraction was six times higher than in the medulla. The determination of SH groups and proteins in high- and low-molecular fractions indicates an induction of the metallothionein formation primarily in the renal cortex. 相似文献
37.
Summary The aim of this electron microscopy study was to further investigate the effects of cis-dichlorodiammineplatinum (cis-DDP) on the cerebellum of the immature rat. Ten-day-old animals were treated with cis-DDP subcutaneously and killed after 1, 7, 15 or 21 days. On postinjection day 1, cis-DDP effects were evident mainly in the external granular layer, with nuclear damage in many dividing cells, while their cytoplasm appeared to be less affected. Some binucleate cells were also present. On the contrary, in postmitotic or more differentiated cells, only cytoplasmic alterations were found. At later stages (postinjection day 7), the frequency of damaged cells in the external granular layer decreased, but there was a cellular deficit in the internal granular layer. Many postmitotic neurons underwent coagulative necrosis. Finally (postinjection days 15 and 21), the cellular deficit was partly compensated for by reactive structures, e.g., glial cell fibers, which underwent hypertrophy after initial edema. Moreover, packing densities of Bergmann astrocytes and oligodendrocytes were higher.This study is a part of the scientific exchange program Proliferation and differentiation of normal and tumor cells between the Italian National Research Council and the Czechoslovak Academy of Sciences 相似文献
38.
The assumption that drugs used as unconditioned stimuli in conditioned taste aversion (CTA) studies act centrally was tested by comparing the effects of systemic and intracerebral injections of harmaline hydrochloride (H) in 340 rats. Intraperitoneal injection of 5–20 mg/kg but not of 2.5 mg/kg H administered 5 min after 15-min saccharin (0.1%) drinking decreased saccharin-water preference in a two-choice retention test, performed 48 h later, from 55% to 20%. Since CTA was not diminished when H (10 mg/kg) was injected into rats anesthetised immediately after saccharin drinking by pentobarbital (40 mg/kg), H (1.7–50 g) was administered intracerebrally to anesthetised rats fixed in the stereotaxic apparatus. Injection of 3–6 g H into the inferior olive elicited CTA comparable to that of systemic injection of 10 mg/kg H. Injections of 6 and 50 g H into cerebellum and bulbar reticular formation elicited weaker CTA while neocortical, hypothalamic and mesencephalic applications were ineffective. CTA could also be elicited when 50 g but not 6 g H was injected into the inferior olive 1 or 2 h after saccharin drinking. This delay-dependent effect and failure of non-contingent H administration to change saccharin preference indicates that the H-induced CTA is not contaminated by a non-specific increase in neophobia. It is concluded that H probably elicits CTA by activation of caudal bulbar structures, including the nucleus of the solitary tract, area postrema and lateral reticular formation. 相似文献
39.
Ladislav Novotný Hassan Farghali Miloš Ryba Ivo Janků Jiří Beránek 《Cancer chemotherapy and pharmacology》1984,13(3):195-199
Summary Both transport and biotransformation processes for a series of pyrimidine nucleobases, ribonucleosides, 2-deoxyribonucleosides, and acetyl and 5-substituted derivatives of the cancerostatic agent araC were studied in the isolated everted rat jejunum with a continuous perfusion technique. Metabolic alterations during penetration were assessed by HPLC. 5-Halogeno and 5-deoxy derivatives of cytosine nucleosides exhibited higher transport rates and higher stability towards the deamination reaction than did unsubstituted derivatives. Octanol-buffer partition coefficients were estimated for the study compounds, and fragmental constants for the sugar moieties of nucleosides were assessed. With the present study compounds there was no correlation between lipophilicity and transport rate, as previously reported, but there was a correlation between lipophilicity and metabolic alteration of araC derivatives (r=0.99, n=5). 相似文献
40.
The effect of 2,3-dimercaptopropane sodium sulfonate on mercury retention in rats in relation to age
The effectiveness of DMPS (sodium 2,3-dimercaptopropane-1-sulfonate) in reducing inorganic mercury retention was studied in 2-, 6-, and 28-week-old albino rats. 203Hg was administered IP. The chelating agent DMPS was administered by IP injection at a dose of 250 mol/kg body weight three times, 1 day after 203Hg administration and at 24 h intervals thereafter. The whole body retention determined 1, 2, 3, and 6 days after 203Hg administration showed that DMPS decreased the body retention of mercury in all age groups, being about twice as effective in adult compared to suckling rats. The reduced effectiveness was due to the reduced efficacy of DMPS in reducing kidney retention in young animals. In other organs the effectiveness of DMPS was not age dependent. These and previous results obtained with different chelating agents and other metals indicate that age might be an important factor in chelation therapy in general. 相似文献