全文获取类型
收费全文 | 4529篇 |
免费 | 287篇 |
国内免费 | 177篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 66篇 |
妇产科学 | 23篇 |
基础医学 | 487篇 |
口腔科学 | 77篇 |
临床医学 | 209篇 |
内科学 | 635篇 |
皮肤病学 | 62篇 |
神经病学 | 192篇 |
特种医学 | 35篇 |
外科学 | 143篇 |
综合类 | 546篇 |
预防医学 | 666篇 |
眼科学 | 28篇 |
药学 | 1411篇 |
1篇 | |
中国医学 | 313篇 |
肿瘤学 | 88篇 |
出版年
2024年 | 10篇 |
2023年 | 65篇 |
2022年 | 158篇 |
2021年 | 163篇 |
2020年 | 113篇 |
2019年 | 107篇 |
2018年 | 95篇 |
2017年 | 125篇 |
2016年 | 135篇 |
2015年 | 158篇 |
2014年 | 226篇 |
2013年 | 337篇 |
2012年 | 217篇 |
2011年 | 275篇 |
2010年 | 216篇 |
2009年 | 206篇 |
2008年 | 219篇 |
2007年 | 241篇 |
2006年 | 205篇 |
2005年 | 209篇 |
2004年 | 157篇 |
2003年 | 145篇 |
2002年 | 123篇 |
2001年 | 91篇 |
2000年 | 98篇 |
1999年 | 80篇 |
1998年 | 79篇 |
1997年 | 69篇 |
1996年 | 61篇 |
1995年 | 59篇 |
1994年 | 62篇 |
1993年 | 52篇 |
1992年 | 47篇 |
1991年 | 52篇 |
1990年 | 42篇 |
1989年 | 30篇 |
1988年 | 30篇 |
1987年 | 29篇 |
1986年 | 23篇 |
1985年 | 28篇 |
1984年 | 28篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
排序方式: 共有4993条查询结果,搜索用时 0 毫秒
11.
用双向电泳分析淡色库蚊卵、二令幼虫、四令幼虫、蛹和成虫蛋白质组成.电泳完毕后,用考马斯亮兰G-250染色,结果以成蚊蛋白质多肽点为最多(116点),其次依次为蛹(101点)、卵(70点)、四令幼虫(53点)、二令幼虫(18点)。它们在不同分子量和不同PH 范围内的分布也不同,但总的来看,在幼体阶段(卵、二、四令幼虫及蛹)多偏低分子量和低PI 值的点,发育至成虫阶段,分布走向全面。 相似文献
12.
13.
FIONA TOMLEY 《Parasite immunology》1994,16(8):407-413
Total polypeptides from unsporulated and sporulated oocysts, sporozoites and the first two generations of merozoites of Eimeria tenella were fractionated by electrophoresis through polyacrylamide gels. The parasites are complex and the arrays of polypeptides differ for each of the developmental stages indicating that there is stagespecific control of gene expression. In particular, first generation merozoites display a markedly different polypeptide profile to that of either sporozoites or second generation merozoites. Changes in antigenicity during sporulation and the antigenic relationships between the three asexual zoite stages were examined by probing electroblotted polypeptides with a panel of antisera raised in rabbits to purified preparations of each stage. Antigenic cross-reactivity is well maintained throughout sporulation even though the sizes of antibody-reactive polypeptides change. In contrast there is a marked lack of cross-reactive epitopes between sporozoites, first and second generation merozoites. 相似文献
14.
Naoki Sugawara Koji Arizono Toshiichi Kitajima Hideaki Inoue Yu-Rong Lai 《Archives of toxicology》1997,71(5):336-339
A new mutant, the Eisai hyperbilirubinemic (EHB) rat, shows no inherent expression of the canalicular isoform of the multidrug
resistance protein (cMrp) in the liver. It has defective biliary secretion of organic anions such as bilirubin glucuronides,
bromosulfophthalein (BSP), cysteinyl leukotrienes, glutathione (GSH) and bile acid sulfate and glucuronides. When rats were
injected intravenously with CdCl2, biliary excretion of Cd over 30 min was 0.28% and 0.004% of the total dose in Sprague-Dawley (SD) and EHB rats, respectively.
Six SD rats and five EHB rats were fed a diet containing Cd. Bile Cd was detected at the level of 2 ng/20 min in SD rats,
but not in EHB rats. There was no significant difference of hepatic Cd concentration between SD and EHB rats. Furthermore,
there were no significant differences of renal and intestinal Cd, and hepatic and renal metallothionein (MT) concentrations
between the SD and EHB groups. Biliary excretion of reduced-GSH for 20 min was 1.3 ± 0.3 mg and 3.6 ± 0.9 μg in SD and EHB
rats, respectively. Our results suggest that hepatobiliary excretion of exogenous Cd is mediated mainly via carrier transport,
including a cMrp or GSH carrier, but that the lack of the transport pathway does not contribute to abnormal accumulation of
Cd in the liver.
Received: 12 August 1996 / Accepted 7 November 1996 相似文献
15.
Kathleen M. Giacomini 《Journal of pharmacokinetics and pharmacodynamics》1997,25(6):731-741
Many clinically used drugs and their metabolites as well as a variety of environmental toxins are organic cations at physiologic pH. Secretion in the renal proximal tubule constitutes a major pathway in the elimination of organic cations. In this report, the results of studies recently performed in this laboratory are presented. First, the molecular cloning of a novel splice variant of organic cation transporter from rat kidney (rOCTIA) is described. The functional characteristics of the transporter are discussed along with the implications of RNA splicing in enhancing transporter diversity. Second, the molecular cloning of the first human organic cation transporter (hOCTI) is described. Distinct interspecies differences in the tissue distribution and function of this transporter is presented. These studies have paved the way for elucidating molecular structure function relationships of organic cation transporters and for determining their physiologic role in drug absorption and elimination. The cloned transporters can be used in mammalian expression systems for screening candidate compounds identified during drug discovery and development and in the in vivo prediction of the pharmacokinetics of therapeutic agents. 相似文献
16.
研究了苏乐康、绿茶提取物对~(60)钴γ射线和雌性激素联合诱发叙利亚金黄地鼠胚胎细胞恶性转化的抑制能力,并用脉冲辐解技术,对其抑制机制进行初步探讨。实验结果表明,苏乐康、绿茶提取物对γ射线和雌性激素联合诱发的金黄地鼠胚胎细胞恶性转化的抑制率分别为70.15%(P<0.05)和81.59%(P<0.05),它们的这种抑制能力与其清除超氧阴离子的能力有关, 相似文献
17.
Proximal tubular cells were loaded for 10 s with [3H]para-aminohippurate ([3H]PAH) by microperfusing the peritubular capillaries with Ringer solution containing 0.05 mmol/l PAH. Immediately thereafter
[3H]PAH influx from cells into a column of equilibrium solution injected into the oil-filled tubular lumen was measured by re-aspirating
the fluid after 1–10 s of contact time. The rise of luminal PAH concentration within 2 s of contact time was almost linear,
reaching a luminal / capillary concentation ratio of 1.6 after 2 s and of 3.2 after 5 s. The 2-s PAH concentration ratio was
not changed when different manoeuvres were applied to depolarize proximal tubular cells. Also, the 2-s PAH concentration ratio
was not influenced by varying the luminal pH from 6.0 to 8.0 or the luminal Cl–concentration from zero to 134 mmol/l or when either 5 mmol/l urate or 25 mmol/l lactate was in the luminal perfusate. A decrease
in the 2-s PAH concentration ratio, i.e. trans-inhibition, was observed when 25 or 50 mmol/l HCO3
–(–50%) was in the luminal perfusate. Trans-inhibition was also seen with 5 mmol/l of the following substituted benzoates:
2-hydroxy-benzoate (–58%), 2-methoxy-benzoate (–46%), 2-hydroxy-benzoate-acetyl ester (–36%), 2-hydroxy-3,5-dinitro-benzoate
(–48%), 3,5-dichloro-benzoate (–49%), and 2,3,5-trichloro-benzoate (–45%). No effect was seen with benzoate, 3-hydroxy-benzoate,
2-chloro-benzoate, 2-nitro-benzoate, 2,5-dinitro-benzoate, 3-sulfamoyl-benzoate and 4-sulfamoyl-benzoate. However, analogues
of the latter two compounds possessing two additional side groups, such as furosemide and piretanide, or a hydrophobic moiety,
such as probenecid, were inhibitory (by –62, –41 and –49% respectively). Phenoxyacetate had no effect; however, it inhibited
if in addition it had three chloro groups, as in 2,4,5-trichlorophenoxyacetate (–71%) or a hydrophobic carbamoyl side group,
as in mersalylic acid (salyrgan, –75%). Benzene-sulfonate trans-inhibited (–33%), as did phenolsulfonphthalein (phenol red,
–39%) and sulfofluorescein (–55%). However, the trans-inhibitory effect of the corresponding carboxy-compounds was absent
(phenolphthalein) or weaker (fluorescein, –42%). The trans-inhibitory effect of the uricosurics ethacrynic acid (–53%), tienilic
acid (–55%) indacrinone (–72%) and benzbromarone (–42%) could be attributed to two chloro or bromo side groups on the benzene
ring. Other trans-inhibiting uricosuric substances were indomethacin (–42%), sulfinpyrazone (–38%), losartan (–80%) its metabolite
EXP 3174 (–55%), and AA 193 (–65%). These organic acids, with pKa values between 2.8 and 4.9, possess chloro and sulfin groups, as well as heterocyclic 5-ring and hydrophobic ring or chain
areas. No significant effect was seen with 5 mmol/l PAH, 2-oxo-glutarate, DIDS, cGMP, prostaglandin E2, cortisol, benzylamiloride, pyrazinoic acid and 25 mmol/l lactate. Our data indicate that in situ the secretory luminal PAH
transport proceeds in a non-rheogenic fashion, per exclusionem by anion exchange. The observed trans-inhibition of PAH secretion seems to correlate with the affinity for the luminal PAH
transporter and, for uricosuric substances, with their uricosuric potency.
Received: 15 October 1996 / Received after revision: 17 December 1996 / Accepted: 18 December 1996 相似文献
18.
John R. Glowa 《Drug development research》1990,20(4):411-428
Volatile organic solvents exhibit a range of behavioral effects from the insidiously toxic to the beneficial. Solvents impair performance in a concentration-dependent manner that depends on the unique physicochemical properties of each solvent. The toxic effects of solvents range greatly but, at sufficient concentrations, or after prolonged exposure, neurotoxic effects are often seen. Many solvents are both self-administered and exhibit noxious properties. Solvents may produce some of their primary behavioral effects by altering γ-amino-butyric acid (GABA) function. Further studies related to mechanism may lead to a better understanding of means to protect individuals from the effects of solvent exposure, as well as further our knowledge of solvent abuse. Solvents activate the stress axis and, as such, their neuroendocrine effects deserve further characterization, because chronic exposure may result in altered neuronal activity similar to that associated with chronic stress. Methods have been developed to assess for risk of the effects of exposure to solvents, detailing the lowest levels of solvent expected to produce behavioral impairment. Results from these procedures should be applied to the different end points described. 相似文献
19.
可同化有机碳(AOC)是一项新的水质检测指标,通过它可以评估供水系统的水中是否有足够的营养物质可使微生物再生长。由于目前尚无可行的化学方法检测 AOC,因此主要是用各种生物方法加以检测。本文介绍用荧光假单胞菌 P—17菌株和螺菌属 NOX 菌株作为测试菌,通过定量观察其在水样中的生长,如从接种到生长至最大数量,以考察其利用水中营养物质的情况,进而推算出水中 AOC 的浓度。 相似文献
20.
Terry M. Maloney Philip L. Paine Jose Russo 《Breast cancer research and treatment》1989,14(3):337-348
Summary The protein populations of epithelial cells cultured from two neoplastic and five non-neoplastic human breast tissues were resolved and displayed by two-dimensional polyacrylamide gel electrophoresis and silverstaining. With a computer-based image analysis system, we identified eight polypeptides which are present in both of the neoplastic cell lines, but absent from all five of the cultures of non-neoplastic breast cells. The eight polypeptides are not unique to cells cultured from neoplastic breast, because they are also found in cells cultured from non-breast tissues, both neoplastic and non-neoplastic. Two of the eight polypeptides ( Mr 25,000/pI 4.4 and Mr 31,000/pI 5.5) are present in the patterns of whole tissue samples from infiltrating ductal carcinomas and absent in most normal breast tissue. 相似文献