全文获取类型
收费全文 | 13402篇 |
免费 | 1185篇 |
国内免费 | 622篇 |
专业分类
耳鼻咽喉 | 63篇 |
儿科学 | 144篇 |
妇产科学 | 36篇 |
基础医学 | 650篇 |
口腔科学 | 45篇 |
临床医学 | 940篇 |
内科学 | 1811篇 |
皮肤病学 | 68篇 |
神经病学 | 367篇 |
特种医学 | 208篇 |
外科学 | 1280篇 |
综合类 | 2070篇 |
预防医学 | 532篇 |
眼科学 | 76篇 |
药学 | 5414篇 |
13篇 | |
中国医学 | 1335篇 |
肿瘤学 | 157篇 |
出版年
2024年 | 20篇 |
2023年 | 170篇 |
2022年 | 249篇 |
2021年 | 487篇 |
2020年 | 468篇 |
2019年 | 361篇 |
2018年 | 374篇 |
2017年 | 417篇 |
2016年 | 437篇 |
2015年 | 487篇 |
2014年 | 1065篇 |
2013年 | 1065篇 |
2012年 | 1153篇 |
2011年 | 1101篇 |
2010年 | 855篇 |
2009年 | 748篇 |
2008年 | 710篇 |
2007年 | 789篇 |
2006年 | 624篇 |
2005年 | 511篇 |
2004年 | 402篇 |
2003年 | 359篇 |
2002年 | 319篇 |
2001年 | 272篇 |
2000年 | 248篇 |
1999年 | 192篇 |
1998年 | 129篇 |
1997年 | 155篇 |
1996年 | 101篇 |
1995年 | 108篇 |
1994年 | 79篇 |
1993年 | 79篇 |
1992年 | 63篇 |
1991年 | 40篇 |
1990年 | 40篇 |
1989年 | 44篇 |
1988年 | 56篇 |
1987年 | 57篇 |
1986年 | 46篇 |
1985年 | 42篇 |
1984年 | 50篇 |
1983年 | 30篇 |
1982年 | 43篇 |
1981年 | 32篇 |
1980年 | 36篇 |
1979年 | 20篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
81.
Stolte M Meining A Koop H Seifert E 《Virchows Archiv : an international journal of pathology》1999,434(1):91-94
Long-term treatment with proton pump inhibitors in patients with Helicobacter pylori gastritis can lead to atrophic changes in the corpus mucosa. What is still unclear, however, is whether this atrophy can
regress in response to Helicobacter pylori eradication. We report on a male patient with Helicobacter pylori gastritis receiving long-term treatment (4 years) with omeprazole for gastro-oesophageal reflux disease, who developed autoaggressive
gastritis with progressive atrophy, hypochlorhydria, hypergastrinaemia and nodular ECL-cell hyperplasia. To determine whether
these changes might be induced to regress, Helicobacter pylori eradication therapy was administered. Ten months after Helicobacter pylori eradication autoaggressive lymphocytic infiltrates were no longer detectable, and the glands in the corpus mucosa had normalised
despite continued treatment with omeprazole – a finding that was confirmed at two further follow-up surveys performed at 6-month
intervals. This case report shows that atrophy of the corpus mucosa developing under long-term treatment with a proton pump
inhibitor can be cured by eradicating Helicobacter pylori.
Received: 21 April 1998 / Accepted: 10 August 1998 相似文献
82.
The effects of vasopressin on membrane potential and tension were studied in isolated segments of basilar arteries from the
University of Iowa colonies of normotensive inbred Kyoto-Wistar rats (WKY) and stroke-prone spontaneously hypertensive rats
(SP-SHR). In the presence of vasopressin (0.01–0.3 IU/ml), basilar arteries from WKY, but not from SP-SHR, developed rhythmic
contractions. These contractions were recorded in 13 of 14 WKY basilar arteries, were unaffected by pretreatment with 6-hydroxydopamine,
and were characterized by 20–100 dyne oscillations in tension, occurring 1–3 cycles/min, and superimposed on the vasopressin-induced
contraction (averaging 60 dynes at 0.01 IU/ml or 160 dynes at 0.3 IU/ml). However, resting membrane potentials were not different
in SP-SHR vs. WKY at 37°C, and both strains showed about the same (11 mV) depolarization by 0.1 IU/ml of vasopressin. The
rhythmic contractions were enhanced by K+-free solution, and abolished in the presence of high K+ solution (30 mM), suggesting that active Na+−K+ transport may be involved in modulating the rhythmic activity. These findings are consistent with the hypothesis that the
vasopressin-induced rhythmic contractions in WKY basilar arteries are at least partly dependent on a reduced activity of electrogenic
Na+−K+ active transport in WKY as compared to SP-SHR.
This research was supported by Grant Nos. HL14388 and HL16328 from the National Institutes of Health. Dr. Rusch is the recipient
of Postdoctoral Fellowship HL06907. 相似文献
83.
F. Jaisser J. D. Horisberger B. C. Rossier 《Pflügers Archiv : European journal of physiology》1993,425(5-6):446-452
The cortical collecting tubule (CCT) of the mammalian kidney reabsorbs sodium and potassium, processes that are mediated by Na/K-ATPase and H/K-ATPase. CCT is also an important site for proton secretion, which is driven, in part, by H/K-ATPase. Na/K-ATPase and H/K-ATPase are members of the ion-motive P-ATPase gene family. They are closely related plasma membrane proteins which consist of heterodimers. The urinary bladder of the toad Bufo marinus is the amphibian counterpart of mammalian CCT. We have previously characterized a ouabain-resistant Na/K-ATPase [see ref. 17], from TBM cells, a clonal cell line derived from the toad bladder, which expresses transepithelial sodium transport. In the present study, we report the primary sequence and functional expression of a novel subunit (
bladder=
bl) isolated from a toad bladder epithelial cell cDNA library. The deduced polypeptide is 299 amino acids in length and has a predicted molecular mass of 33 kDa. The
bl protein exhibits 35% amino acid identity to the previously characterized
1 of B. marinus Na/K-ATPase and 39% identity with
3 of B. marinus Na/K-ATPase. It shares 38% identity with the mammalian gastric H/K-ATPase and 52% with the mammalian
2 Na/K-ATPase. Northern blot analysis shows that a 1.4×103-base mRNA is expressed at a high level in bladder epithelial cells and eye and at a trace level in kidney; it is not detectable in significant amounts in the stomach, colon and small intestine. The
bl subunit can associate with the
1 subunit of B. marinus Na/K-ATPase to form a functional sodium pump in the Xenopus laevis oocyte. Our data indicate that, in addition to the known
1 and
3 isoforms, a third distinct isoform of the subunit is present in the bladder epithelium. This new isoform could be functionally associated with subunits of either Na/K- or H/K-ATPase. 相似文献
84.
The fourth-generation centrifugal blood pump 总被引:1,自引:0,他引:1
The NEDO Gyro permanently implantable (PI) centrifugal blood pump has been developed as a simple, durable, centrifugal blood
pump without a complex magnetic suspension system. In vitro studies were performed using a Gyro PI pump with the transparent
pump housing in a mock circuit. These studies revealed that the impeller transfers to a floating or a top contact condition,
which was dependent on the revolutions per minute (RPM). This pump can be easily converted from a left ventricular assist
device (LVAD) to a right ventricular assist device (RVAD) by simply adding a spacer between the pump and the actuator. In
order to optimize the impeller suspension for the LVAD and RVAD, spacers of the proper thickness are inserted between both
of the pumps and the actuators to regulate the magnetic force. Two Gyro PI pumps were implanted in a bovine model in a 3-month
biventricular assist device (BVAD) animal study. This experiment was electively terminated 90 days after implantation. All
of the parameters, including pump flow rate, power consumption, and plasma free hemoglobin, were in acceptable ranges. No
thrombus formation was observed in either pump. Antithrombogenesis and effectiveness were demonstrated in this animal study.
The NEDO Gyro PI pump is ready to move on to the 3-month preclinical system evaluation.
Received: February 28, 2002 / Accepted: May 30, 2002
Acknowledgment The New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade and Industry
of Japan financially supported this project.
Correspondence to:S. Ichikawa 相似文献
85.
Braakman R. Sipkema P. Westerhof N. 《Pflügers Archiv : European journal of physiology》1986,407(4):432-439
It has been reported that sodiumnitroprusside (SNP) decreases mean systemic pressure and simultaneously increases pressure pulse amplification towards the iliac periphery (Kenner and van Zwieten 1982). This unexpected finding was suggested to be due to a decrease in iliac peripheral resistance but an increase in iliac differential resistance. In order to investigate this apparent contradiction, the iliac periphery was hemodynamically isolated from the rest of the circulation and perfused with the dog's own blood by means of a pump. Perfusion pressure (P) and flow (F), femoral venous pressure (Pv), systemic pressure (Ps) and cardiac output (CO) were measured. Steady state pressure-flow relations of the isolated bed were obtained during control and during various i.v. infusion rates of SNP and adenosine (ADS) and were found to be straight (meanr=0.99). Their slope (P/F) was defined as differential resistance (Rd). Peripheral resistance (Rp) of the iliac bed was defined as Rp=(P-Pv)/F, calculated at the flow value where perfusion pressure equalled the prevailing systemic pressure. Total peripheral resistance (TPR) was defined as TPR=Ps/CO. The changes of Rd, Rp, Ps, CO and TPR with respect to control show that during low SNP infusion rates Rd and Rp were both increased while TPR was decreased. During all infusion rates of SNP CO did not change while Ps decreased. During low infusion rates of adenosine CO increased while Ps, Rd and Rp did not change and TPR decreased. During high infusion rates of ADS CO decreased again, Rd, Rp and Ps decreased, and TPR remained constant but at a decreased level.It is concluded that: (1) the suggestion of Kenner and van Zwieten is not supported, since SNP (as well as ADS) affects iliac peripheral and iliac differential resistance in a similar way; (2) SNP (as well as ADS) affects iliac peripheral resistance and total peripheral resistance in a differentiated way, and even in an opposite way during low infusion rates of SNP; (3) it is this opposite effect that explains the paradoxical observations of Kenner and van Zwieten; (4) for comparable reductions of TPR, CO is better maintained during infusion of SNP, while Ps is better maintained during infusion of ADS. 相似文献
86.
介绍了临床应用的左心室辅助装置的类型和结构特点,分析了基于生理机制的血泵电机参数的血泵控制策略;提出基于多生理信号约束的控制策略控制血泵输出,易满足受体的需求。结合血泵系统现状,从血泵的结构、穿皮能量传递方式和控制策略等方面探讨今后的研究目标。 相似文献
87.
J. L. Borke A. Caride A. K. Verma J. T. Penniston R. Kumar 《Pflügers Archiv : European journal of physiology》1990,417(1):120-122
We used a monoclonal antibody (5F10) specific for the human erythrocyte plasma membrane Ca++-pump to demonstrate the presence and distribution of Ca++-pump epitopes in rat intestine. In paraffin embedded tissue sections, antibody 5F10 binds to epitopes in the basolateral membranes of absorptive cells in rat duodenum and portions of jejunum but not ileum. Western blot analysis of intestinal mucosal proteins with antibody 5F10 shows binding of antibody to major bands of Mr 135,000 and Mr 72,000, and to lesser bands of Mr 125,000 and Mr 27,000. This pattern was seen in mucosal homogenates of rat duodenal and jejunal cells and to a lesser extent in ileal cells. The Mr 135,000 band corresponds to the molecular weight of Ca++-pumps in other tissues. The other bands correspond in size to known proteolytic fragments of the Ca++-pump. Slot-blot analysis of nitrocellulose immobilized mucosal homogenates shows binding of 5F10 to be greatest in duodenum and least in ileum. Ca++- transport studies by the everted gut sac technique show a correlation between vitamin D induction of active Ca++-transport and the segmental distribution of Ca++-pump epitopes. 相似文献
88.
Stéphane Genet Raymond T. Kado 《Pflügers Archiv : European journal of physiology》1997,434(5):559-567
The contribution of the Na/K ATPase (pump) current to the polarization of the Purkinje cell has been studied using slices
of the rat cerebellum by blocking the pump with dihydro-ouabain (DHO) while recording the membrane potential with microelectrodes
in the somata. From our recordings, it appeared that blocking the pump depolarized the Purkinje cells more rapidly than might
be expected from shifts in Na+ and K+ concentrations, suggesting the removal of a hyperpolarizing current. Application of DHO, in the presence of tetrodotoxin (TTX),
led to calcium spike firing and plateau-like discharges suggesting activation of voltage-dependent calcium channels in the
dendrites. Adding 2 mM Co2+ to the medium did not prevent the depolarizations. Removing calcium from the bathing medium containing 2 mM Co2+ blocked the spiking activity but DHO application still produced a depolarization. Experiments to measure the current inhibited
by DHO indicated that the Na/K pump supplies a constant current of 240 pA. Substitution of the sodium with choline produced
a hyperpolarization, during which DHO had no effect on the membrane potential. Substitution of the sodium with lithium produced
only a slowly developing depolarization. It is concluded that in the cerebellar Purkinje cell, a continuous sodium ion influx
activates the pumps which produce a current that directly contributes to the membrane polarization. Possible pathways for
this sodium influx are discussed.
Received: 3 April 1997 / Received after revision and accepted: 12 May 1997 相似文献
89.
Summary The effect of different potassium concentrations on the membrane potential and membrane resistance of rat diaphragm muscle fibres was measured by means of a double sucrose gap method and a microelectrode technique. Concentration measurements showed that the muscle fibres gained sodium and lost potassium in the equilibration period.In the absence of external chloride changing the external potassium concentration from 2.8 mM to potassium-free caused a depolarization of the membrane of about 30 mV and a small increase in membrane resistance.This K-dependent potential change (K-response) was reduced by ouabain, K-strophanthin, 2,4-dinitrophenol and cyanide, indicating that an energy requiring process is involved. The temperature dependence of the K-response found is consistent with this assumption. Variation in potassium permeability in the absence and presence of external potassium could account for only 13% of the K-response.The K-response amplitude appeared to depend on the external potassium and the internal sodium concentration. Hyperpolarization of the membrane could not only be produced after readmission of potassium but also after addition of thallium, the latter being more potent. Raising the external chloride concentration resulted in a decrease of the K-response and membrane resistance. The current, generating the Kresponse was shown to be hardly influenced by conditional polarization of the membrane.It is concluded from these results that the Kresponse is mainly due to the operation of an electrogenic sodium pump. 相似文献
90.
P. M. T. Deen Søren Nielsen René J. M. Bindels Carel H. van Os 《Pflügers Archiv : European journal of physiology》1997,433(6):780-787
Aquaporin-1 is present in the apical and basolateral membranes in proximal tubules and descending limbs of Henlé’s loop.
In order to be able to study the routing of Aquaporin-1 and the regulation of Aquaporin-1-mediated transcellular water flow,
we stably transfected LLC-PK1 and MDCK-HRS cell lines with an Aquaporin-1 expression construct. LLC-PK1 clone 7 and MDCK clone K integrated two and one copies, respectively, which was reflected in the amount of Aquaporin-1 mRNA expressed in both clones. The Aquaporin-1 protein levels, however, were similar. In both clones, immuno-electronmicroscopy
showed extensive labelling of Aquaporin-1 on the basolateral plasma membrane, endosomal vesicles and the apical plasma membrane,
including the microvilli. To measure transcellular water permeation, a simple method was applied using phenol-red as a cell-impermeant
marker of concentration. In contrast to the native cell lines, both clones revealed a high transcellular osmotic water permeability,
which could not be influenced by forskolin add/3-isobutyl-1-methylxanthine (IBMX) or the phorbol ester 12-O-tetradecanoyl 13-acetate (TPA). After glutaraldehyde fixation, it was inhibitable by HgCl2. These results indicate that targeting of Aquaporin-1 to the apical and basolateral plasma membrane is independent of cell
type and show for the first time that water flow through a cultured epithelium can be blocked by mercurial compounds.
Received: 9 October 1996 / Received after revision: 3 January 1997 / Accepted: 8 January 1997 相似文献