全文获取类型
收费全文 | 119121篇 |
免费 | 6037篇 |
国内免费 | 167篇 |
专业分类
耳鼻咽喉 | 1824篇 |
儿科学 | 5269篇 |
妇产科学 | 4095篇 |
基础医学 | 16316篇 |
口腔科学 | 2944篇 |
临床医学 | 8551篇 |
内科学 | 22681篇 |
皮肤病学 | 3432篇 |
神经病学 | 9144篇 |
特种医学 | 5148篇 |
外国民族医学 | 32篇 |
外科学 | 19648篇 |
综合类 | 1646篇 |
一般理论 | 29篇 |
预防医学 | 5908篇 |
眼科学 | 3479篇 |
药学 | 8212篇 |
中国医学 | 329篇 |
肿瘤学 | 6638篇 |
出版年
2018年 | 971篇 |
2017年 | 830篇 |
2016年 | 1176篇 |
2015年 | 1317篇 |
2014年 | 1717篇 |
2013年 | 2533篇 |
2012年 | 3313篇 |
2011年 | 3384篇 |
2010年 | 2082篇 |
2009年 | 2030篇 |
2008年 | 3468篇 |
2007年 | 3755篇 |
2006年 | 3870篇 |
2005年 | 3985篇 |
2004年 | 3874篇 |
2003年 | 3711篇 |
2002年 | 3636篇 |
2001年 | 7081篇 |
2000年 | 7009篇 |
1999年 | 5910篇 |
1998年 | 1632篇 |
1997年 | 1568篇 |
1996年 | 1341篇 |
1995年 | 1210篇 |
1994年 | 1091篇 |
1993年 | 1125篇 |
1992年 | 3780篇 |
1991年 | 3593篇 |
1990年 | 3573篇 |
1989年 | 3357篇 |
1988年 | 2992篇 |
1987年 | 2896篇 |
1986年 | 2805篇 |
1985年 | 2617篇 |
1984年 | 1943篇 |
1983年 | 1594篇 |
1982年 | 927篇 |
1981年 | 915篇 |
1980年 | 766篇 |
1979年 | 1823篇 |
1978年 | 1348篇 |
1977年 | 1113篇 |
1976年 | 936篇 |
1975年 | 1178篇 |
1974年 | 1212篇 |
1973年 | 1198篇 |
1972年 | 1040篇 |
1971年 | 975篇 |
1970年 | 880篇 |
1969年 | 787篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The splenomegaly assay (Simonsen, 1962) was standardized using different strains of rats and mice. Male Wistar rat (donor)-female Swiss mouse (host) was found to be the suitable combination that could be employed in subsequent experiments to study the potential of contraceptive steroids to alter CMIR. The index of splenomegaly appeared to increase in case of mice treated with combination oral contraceptives (Ovulen, Ovral or Enovid). The differences observed, however, neared significance only in the case of Ovral (0-05 less than P less than 0-1). Neither chlormadinone acetate nor megestrol acetate significantly altered the index of splenomegaly. 相似文献
992.
Biological effects of cyclosporin A: A new antilymphocytic agent 总被引:4,自引:0,他引:4
The fungus metabolite cyclosporin A is a small peptide acting as a novel antilymphocytic agent. It strongly depressed appearance of both direct and indirect plaque-forming cells and produced a clear dose-dependent inhibition of haemagglutinin formation in mice upon oral administration. Skin graft rejection in mice and graft-versus-host disease in mice and rats were considerably delayed by cyclosporin A which also prevented the occurrence of paralysis in rats with experimental allergic encephalomyelitis. This compound was not only highly effective in preventing development of Freund's adjuvant arthritis, but in addition improved the symptoms in rats with established arthritis, although it is inactive in acute inflammation. This new agent contrasts with other immunosuppressives and cytostatic drugs in its weak myelotoxicity. Experimental evidence suggests that cyclosporin A, rather than being cytostatic or lympholytic, affects an early stage of mitogenic triggering of the immunocompetent lymphoid cell. 相似文献
993.
V. S
RENSEN U. NILSSON S. PETTERSSON T. SCHERSTN P. O. SJ
QVIST L. SVENSSON O. JONSSON 《Acta physiologica (Oxford, England)》1996,157(2):289-297
Lipid peroxidation of mitochondrial and cell membrane structures is the final step in the oxygen radical-induced damage observed at reperfusion of kidneys after ischaemia. We compared the ability of an indeno-indol compound (code name H290/51) with that of α-tocopherol to inhibit lipid peroxidation in reoxygenated isolated rat renal tissue in vitro measured as production of TBARS (thiobarbituric acid reactive substances). H290/51 was 100 times more efficient than α-tocopherol. Treatment of rats in vivo with H290/51 in a dosage giving a plasma concentration of 500 nmol L-1 inhibited TBARS production measured in vitro by 80%. Treatment of rabbits with H290/51 almost completely inhibited radical production at reperfusion after 60 min of ischaemia measured with spin trap technique using OXANOH (2-ethyl-3-hydroxy-2,4,4-trimethyloxazolidine) as a spin trap. Furthermore, such pretreatment significantly improved kidney function and survival of rabbits subjected to 60 min of ischaemia to the left kidney and contralateral nephrectomy. These studies stress the importance of inhibiting lipid peroxidation to prevent the ischaemia-reperfusion damage and furthermore suggest a role for treatment with antioxidants like H290/51 in clinical practice, e.g. at reconstructive renal surgery and transplantation. 相似文献
994.
Occupational asthma and rhinitis due to glutaraldehyde: changes in nasal lavage fluid after specific inhalatory challenge test 总被引:2,自引:0,他引:2
BACKGROUNDd: Glutaraldehyde (GA) is a known respiratory sensitizers, and some studies have reported occupational asthma in exposed workers. Specific changes in nasal lavage fluid (NLF) induced by high-molecular-weight allergen provocation in sensitized subjects were described previously. The purpose of this study was to evaluate the changes in cytogram, protein content, eosinophil cationic protein (ECP), and mast-cell tryptase concentrations in NLF after GA inhalation challenge in patients with a positive history of GA-induced asthma and late or dual asthmatic response due to exposure to low-level GA. METHODS: A single-blind, placebo-controlled study was performed on 11 health workers with occupational asthma and rhinitis due to GA. The control groups comprised 10 atopic subjects with perennial asthma and rhinitis and 10 healthy ones. A "nasal pool" technique was used to evaluate the examined parameters in nasal washings before and 30 min, 4 h, and 24 h after the inhalatory provocation with GA and placebo. RESULTS: There was a significant increase in eosinophil number and percentage, and albumin, ECP, and tryptase concentrations in NLF from patients with occupational asthma and rhinitis when compared to controls. CONCLUSIONS: The results indicate the immunologic mechanism of GA-induced asthma and the applicability of the "nasal pool" technique as the diagnostic procedure in GA-induced airway allergy. 相似文献
995.
Depolarization-induced retrograde synaptic inhibition in the mouse cerebellar cortex is mediated by 2-arachidonoylglycerol 总被引:3,自引:0,他引:3
Bela Szabo Michal J. Urbanski Tiziana Bisogno Vincenzo Di Marzo Aitziber Mendiguren Wolfram U. Baer Ilka Freiman 《The Journal of physiology》2006,577(1):263-280
Endocannabinoids acting on CB1 cannabinoid receptors are involved in short- and long-term depression of synaptic transmission. The aim of the present study was to determine which endocannabinoid, anandamide or 2-arachidonoylglycerol (2-AG), is involved in depolarization-induced suppression of inhibition (DSI) in the cerebellar cortex, which is the most widely studied form of short-term depression. Depolarization of Purkinje cells in the mouse cerebellum led to an increase in intracellular calcium concentration and to suppression of the inhibitory input to these neurons (i.e. DSI occurred). Orlistat and RHC80267, two blockers of sn -1-diacylglycerol lipase, the enzyme catalysing 2-AG formation, abolished DSI by acting downstream of calcium influx. In contrast, DSI occurred also in the presence of a phospholipase C inhibitor. Intact operation of the calcium-dependent messengers calmodulin and Ca2+ –calmodulin-dependent protein kinase II were necessary for DSI. DSI was potentiated by an inhibitor of the main 2-AG-degrading enzyme, monoacylglycerol lipase. Interference with the anandamide metabolizing enzyme, fatty acid amide hydrolase, did not modify DSI. Thus, three kinds of observations identified 2-AG as the endocannabinoid involved in DSI in the mouse cerebellum: DSI was abolished by diacylglycerol lipase inhibitors; DSI was potentiated by a monoglyceride lipase inhibitor; and DSI was not changed by an inhibitor of fatty acid amide hydrolase. Further experiments indicated that 2-AG is the endocannabinoid mediating short-term retrograde signalling also at other synapses: orlistat abolished DSI in the rat cerebellum, DSI in the mouse substantia nigra pars reticulata and depolarization-induced suppression of excitation in the mouse cerebellum. 相似文献
996.
Proliferation in HHV-8-positive primary effusion lymphomas is associated with expression of HHV-8 cyclin but independent of p27(kip1)
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Carbone A Gloghini A Bontempo D Monini P Tirelli U Volpe R Browning PJ Gaidano G 《The American journal of pathology》2000,156(4):1209-1215
Primary effusion lymphoma (PEL) develops in immunodeficient patients, selectively localizes to the serous body cavities, and harbors infection by human herpesvirus type-8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus. HHV-8 encodes a viral (v)-cyclin homologous to cellular D-type cyclins, a class of positive cell-cycle regulators that are physiologically modulated by the p27(Kip1) cell cycle inhibitor. The aims of the present study were: 1) to establish the expression pattern of p27(Kip1) in PEL; and 2) to address the relationship between p27(Kip1) expression, proliferation index, and expression of cellular cyclin D1 and v-cyclin in PEL. Expression of p27(Kip1) was detected in all (n = 18) PEL samples analyzed by both immunocytochemistry and Western blot. All PELs displayed a high proliferation index as assessed by Ki-67 staining. Expression of cellular cyclin D1 was absent in all PELs tested, which conversely expressed (14 out of 14 samples) v-cyclin by immunocytochemistry and/or Western blot. In contrast to PELs, HHV-8-negative lymphomatous effusions secondary to a tissue-based lymphoma generally failed to express p27(Kip1). Overall, these data show that PELs consistently express p27(Kip1) protein despite the high proliferative rate of the lymphoma clone, suggesting that p27(Kip1) may be unable to drive cell-cycle arrest in PEL cells. The co-existence of p27(Kip1) expression and high proliferative index is a selective feature of PEL among lymphomas involving the serous body cavities, because lymphomatous effusions secondary to a tissue-based lymphoma generally display the inverse relationship between p27(Kip1) positivity and growth fraction observed in normal lymphoid tissues and in most other lymphomas. Expression of p27(Kip1) in PEL associates with expression of HHV-8 v-cyclin, but not of cellular cyclin D1. The fact that HHV-8 v-cyclin is resistant to p27(Kip1)-modulated inhibition, whereas cellular cyclin D1 is sensitive, may explain, at least in part, the co-existence of p27(Kip1) expression and high proliferative index observed in PEL. 相似文献
997.
Detection of gene amplification in archival breast cancer specimens by laser-assisted microdissection and quantitative real-time polymerase chain reaction 总被引:7,自引:0,他引:7
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lehmann U Glöckner S Kleeberger W von Wasielewski HF Kreipe H 《The American journal of pathology》2000,156(6):1855-1864
Gene amplification is one of the most important mechanisms leading to deregulated gene expression in cancer. The exact quantitative detection of this frequent genomic alteration in solid tumors is often hampered by an admixture of nonneoplastic bystander and stroma cells. To overcome this obstacle and to develop an objective quantitative method we have combined laser-assisted microdissection of tumor cells with the novel 5'-exonuclease-based real-time polymerase chain reaction (PCR) assay. The latter method enables the highly reproducible exact quantification of minute amounts of nucleic acids. As a model system amplification of c-erbB2/Her-2/neu gene and the adjacent topoisomerase IIalpha gene was determined in paraffin-embedded breast cancer specimens (n = 23) after immunohistochemical labeling and laser-based microdissection of tumor cells. The high sensitivity of real-time PCR enabled the reliable and objective detection of low-level amplifications in as few as 50 cells from archival tissue sections. Low-level amplifications were shown to escape from detection unless tumor cells were isolated by microdissection. In selected cases intratumor heterogeneity was demonstrated using areas of approximately 50 to 100 cells. This novel approach combining immunohistochemistry, laser microdissection, and quantitative kinetic PCR allows morphology-guided studies in archival tissue specimens and will enable the exact quantification of gene copy numbers in even small and precancerous lesions. 相似文献
998.
Persistent infection of the central nervous system (CNS) with measles virus (MV) is associated with characteristic restrictions of viral envelope gene expression as documented in subacute sclerosing panencephalitis (SSPE), measles inclusion body encephalitis (MIBE), or subacute measles encephalitis (SAME) in rats. To determine whether these restrictions are the result of a long lasting virus-host cell interaction or primarily based on intrinsic brain cell factors MV gene expression was analyzed in primary rat astroglial cultures. It could be shown that MV infection of these cells led to a defective replication cycle with a reduced synthesis of viral envelope proteins and a steep expression gradient of the monocistronic viral mRNAs similar to the findings in brain tissue of SSPE, MIBE, and SAME. This restriction of MV gene expression has not been observed in cells of nonneural origin. We suggest that this cell-type specific regulation of MV gene expression contributes to early events in the establishment of MV persistent infection in CNS tissue. 相似文献
999.
Possibilities and limitation of prenatal diagnosis and carrier determination for Duchenne and Becker muscular dystrophy using cDNA probes.
下载免费PDF全文
![点击此处可从《Journal of medical genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A Speer A W Spiegler R Hanke K Grade U Giertler J Schieck S Forrest K E Davies R Neumann R Bollmann et al. 《Journal of medical genetics》1989,26(1):1-5
Two cDNA probes, cf23a and cf56a, identify deletions of selected exons in about 50% of our DMD/BMD patients. We have estimated the most likely order of the 11 exons detectable with both probes with respect to the different extensions of the deletions. In one of our BMD pedigrees, the observed deletion could be traced in the affected males through three generations. This result shows that with the use of cDNA probes detecting deletions, the only risk of error in genomic prenatal diagnosis is the general high frequency of new mutations for DMD/BMD. This is important progress in diagnosis compared to the 2 to 5% risk of misdiagnosis because of crossing over events using conventional linkage analysis with bridging or intragenic probes. The first prenatal diagnosis of an unaffected fetus of a woman who is a DMD carrier according to ultrasound examination is described. In one of our DMD males, the cDNA probe cf56a detects a deletion breakpoint. His sister also shows the altered band and is therefore a DMD carrier, while his mother has a totally normal band pattern. The interpretation of this observation could be either germline mosaicism or two identical new mutations. The identification of deletion breakpoints is a new diagnostic strategy, especially for carrier determination, which excludes misdiagnosis owing to crossing over events and the problems of dosage estimation. It is, however, limited by the low frequency of breakpoints detectable with cDNA probes. Therefore, the generation of new intron probes in this region is an important goal. 相似文献
1000.
Summary All the necessary steps required for the cultivation of Vero cells on microcarriers are described. These procedures are used routinely in our laboratories for the growth of Vero cells on Cytodex 1. Consistent, high density, final yields of more than 106 cells/ml of culture medium are obtained. The protocols described here can be modified for the growth of a variety of anchorage-dependent cell types. Culture parameters important for the successful exploitation of microcarrier cell culture technology are discussed. 相似文献